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1

Mineralized microbes from Giggenbach submarine volcano  

Microsoft Academic Search

The Giggenbach submarine volcano, which forms part of the Kermadec active arc front, is located ?780 km NNE of the North Island of New Zealand. Samples collected from chimneys associated with seafloor hydrothermal vents on this volcano, at a depth of 160–180 m, contain silicified microbes and microbes entombed in reticular Fe-rich precipitates. The mineralized biota includes filamentous, rod-shaped, and

Brian Jones; C. E. J. de Ronde; Robin W. Renaut

2008-01-01

2

Submarine Volcanoes in Arctic Ocean Surprise Scientists  

NSDL National Science Digital Library

Until now, geoscientists believed that spreading ridges under the Arctic Ocean were too slow-spreading and cool to vent molten rock. An article published this month in Nature details sonar data revealing two young volcanoes under Arctic waters. Dr. Marago H. Edwards of the University of Hawaii led the exploration team in which civilian scientists worked in cooperation with the Navy, using a nuclear submarine to take sonar readings of the ocean floor. A submarine was employed because the ice cover makes the Arctic seafloor unviewable by satellites and difficult for ships bearing seismic instruments to navigate. The two volcanoes were found at the Gakkel Ridge, the Earth's slowest spreading mid-ocean ridge. During August and September of 2001, Russian icebreakers and Mir submersibles will be employed to investigate the volcanoes, taking rock samples and looking for organisms living at the volcanic vents. This week's In the News takes a closer look at this discovery.

Sanders, Hilary C.

2001-01-01

3

Extreme Spatial Variability in Microbial Mat Communities from Submarine Hydrothermal Vents Located at Multiple Volcanoes along the Mariana Island Arc  

NASA Astrophysics Data System (ADS)

Volcanic arc systems are the most active tectonic feature in the world, but are among the least studied. The Western Pacific contains ~20,000 km of volcanic arcs, of which only ~2% have been systematically surveyed. The lack of comprehensive knowledge of volcanic arcs is compounded by the incredible variability found in relatively short distances. The complex source history of hydrothermal fluids and the variable depths of seamounts found in island arc systems result in highly variable vent chemistries and therefore unique microbial habitats within relatively short distances. The Mariana Island Arc was surveyed in 2003 and areas with suspected hydrothermal activities were identified for targeted remote operating vehicle (ROV) exploration and sampling in 2004. Sixteen microbial mat samples from five seamounts ranging from 145-1742 mbsl and from ambient to 222°C were collected and analyzed with quantitative PCR (Q-PCR), cluster analysis of terminal restriction length polymorphism (T-RFLP) community fingerprints, and by clone library analysis of small subunit ribosomal rDNA genes. The microbial mat communities from the Mariana Island Arc exhibit greater spatial variability within their community structure than microbial mats sampled from mid-ocean ridge or hotspot hydrothermal vents from a comparable scale. Microbial communities from the summit of NW Eifuku Volcano are dominated by putative iron-oxidizing phylotypes at the Yellow Top and Yellow Cone Vent sites, but are dominated by sulfur-oxidizing ?-Proteobacteria at the Champagne Vent site. Mats collected at the Mat City Vent site on E Diamante Seamount contained nearly three times as much biomass as any other mat sample collected, and is dominated by a Planctomyces phylotype. Hydrothermal sediments at the Fish Spa site located on Daikoku Seamount contained the second highest biomass detected and supported a large community of flatfish indicating a direct route for biomass being channeled up the food chain. The microbial community at Fish Spa consists of a highly diverse assemblage of Bacteroidetes, ?-Proteobacteria and Firmicutes. While in contrast, the microbial mat at the Iceberg Vent site on NW Rota I is dominated by a single phylotype of ?-Proteobacteria.

Davis, R. E.; Moyer, C. L.

2005-12-01

4

Physical volcanology of the submarine Mariana and Volcano Arcs  

Microsoft Academic Search

Narrow-beam maps, selected dredge samplings, and surveys of the Mariana and Volcano Arcs identify 42 submarine volcanos. Observed activity and sample characteristics indicate 22 of these to be active or dormant. Edifices in the Volcano Arc are larger than most of the Mariana Arc edifices, more irregularly shaped with numerous subsidiary cones, and regularly spaced at 50–70 km. Volcanos in

Sherman H. Bloomer; Robert J. Stern; N. Christian Smoot

1989-01-01

5

A Submarine Perspective on Hawaiian Volcanoes  

NASA Astrophysics Data System (ADS)

Postwar improvements in navigation, sonar-based mapping, and submarine photography enabled the development of bathymetric maps, which revealed submarine morphologic features that could be dredged or explored and sampled with a new generation of manned and unmanned submersibles. The maps revealed debris fields from giant landslides, the great extent of rift zones radiating from volcanic centers, and two previously unknown submarine volcanoes named Mahukona and Loihi, the youngest Hawaiian volcano. About 70 major landslides cover half the flanks of the Hawaiian Ridge out to Midway Island. Some of the landslides attain lengths of 200 km and have volumes exceeding 5,000 km3. More recent higher resolution bathymetry and sidescan data reveal that many submarine eruptions construct circular, flat-topped, monogenetic cones; that large fields of young strongly alkalic lava flows, such as the North Arch and South Arch lava fields, erupt on the seafloor within several hundred km of the islands; and that alkalic lavas erupt during the shield stage on Kilauea and Mauna Loa. The North Arch flow field covers about 24,000 km2, has an estimated volume between about 1000 and 1250 km3, has flows as long as 108 km, and erupted from over 100 vents. The source and melting mechanisms for their production is still debated. The maps also displayed stair-step terraces, mostly constructed of drowned coral reefs, which form during early rapid subsidence of the volcanoes during periods of oscillating sea level. The combination of scuba and underwater photography facilitated the first motion pictures of the mechanism of formation of pillow lava in shallow water offshore Kilauea. The age progression known from the main islands was extended westward along the Hawaiian Ridge past Midway Island, around a bend in the chain and northward along the Emperor Seamounts. Radiometric dating of dredged samples from these submarine volcanoes show that the magma source that built the chain has been active for over 80 Ma and established the remarkable linearity of the age-progression along the chain. Glass rinds on submarine lava quenched at depth contain initial magmatic volatiles and yield data on the juvenile water, sulfur, CO2, and rare gas contents of basaltic magmas, and continue to reveal nuances of the volatile contents of lava. Rock sampling at Loihi Seamount led to the discovery of the pre-shield alkalic phase of Hawaiian volcanism, which mirrors the well-known post-shield alkalic phase. Lava compositions from the Hawaiian Ridge and Emperor Seamounts have clear affinities to present-day Hawaiian lavas, but subtle source differences as well. The progression from small to large and back to small degrees of melting at individual volcanoes and the compositional changes along the chain constrain the melting processes and source compositions of Hawaiian volcanism. Coupling the age of lavas with that of submerged coral reefs has provided data on the growth and subsidence of volcanic centers. This information has meshed nicely with the age, composition, and morphology of lavas from the 3.2-km-deep Hawaiian Scientific Drill Hole. Submarine studies have taught us much about the workings of Hawaiian Volcanoes, and in the process have stimulated new work and concepts on marine volcanism worldwide.

Clague, D. A.; Moore, J. G.

2011-12-01

6

Debris Avalanche Formation at Kick'em Jenny Submarine Volcano  

Microsoft Academic Search

Kick'em Jenny submarine volcano near Grenada is the most active volcanic center in the Lesser Antilles arc. Multibeam surveys of the volcano by NOAA in 2002 revealed an arcuate fault scarp east of the active cone, suggesting flank collapse. More extensive NOAA surveys in 2003 demonstrated the presence of an associated debris avalanche deposit, judging from their surface morphologic expression

H. Sigurdsson; S. N. Carey; D. Wilson

2005-01-01

7

Ocean bottom tiltmeter developed for submarine volcano monitoring  

NASA Astrophysics Data System (ADS)

Most of the oceanic crust is formed by intrusive processes, yet these processes at mid-ocean ridges are poorly understood when compared to on-land volcanos that are well monitored with respect to their surface deformation and seismic activity. This limited knowledge of tectonic processes at mid-ocean ridges stems from an absence of direct observations and inhibits our understanding of their magmatic segmentation, and many first-order magmatic processes, including fractionation and mixing. As a means to improve this situation, we have installed tiltmeters in the Scripps Ocean Bottom Seismographs (OBS) and begun initial performance testing in sediment and hard rock environments. These tests indicate that the TILT-OBS is now ready for realistic, designated testing on submarine volcanos. Such tests may be in the form of a rapid response monitoring of recently discovered submarine volcanic activity, or as the first trial measurements of strain in more stable, mid-ocean ridge volcanos.

Staudigel, H.; Wyatt, F. K.; Orcutt, J. O.

8

Hydrothermal Helium Plumes over Submarine Volcanoes of the Marianas Arc  

NASA Astrophysics Data System (ADS)

During February-March, 2003, as part of the Submarine Ring of Fire project funded by NOAA's Ocean Exploration Program, the R/V T.G. Thompson conducted a comprehensive survey of hydrothermal activity along 1200 km of the Mariana Arc from 13.5° N to 22.5° N [see Embley et al., EOS Trans. AGU, 2003]. Plume surveys were conducted in the water-column above ~50 submarine volcanoes using a CTD/rosette system. A total of 70 CTD casts were completed, and discrete water samples were collected for analysis of a variety of hydrothermal tracers, including 3He, CH4, CO2, H2S, Fe, Mn, pH, and suspended particles. Although shorebased analysis of the samples is still underway, preliminary results indicate that about 11 of the 50 submarine volcanoes surveyed are hydrothermally active. Because many of the Marianas Arc volcanoes rise to within 500 m of the sea surface, hydrothermal plume signals such as light attenuation (suspended particles) and temperature anomaly have limited utility due to masking by near surface effects. For this reason 3He, an unambiguous hydrothermal tracer, has been particularly useful for identifying which of the shallow arc volcanoes are hydrothermally active. Our expectation was that the water-column helium signal might be reduced at shallow depths due to ventilation into the atmosphere. However, we observed very high 3He enrichments at shallow depths both at Maug Islands and at NW Rota #1 (14° 36'N; 144° 46.5'E). The 3He enrichments were strongly correlated with changes in pH, Mn, and other hydrothermal tracers. The three Maug Islands mark the perimeter of a caldera formed by an explosive eruption, and a single hydrocast in the center of the caldera detected a robust helium plume at 120-200 m depth with ? 3He reaching a maximum of 250% at 150m depth. Analysis of the co-variation of [3He] vs. [4He] at Maug gave R/Ra = 6.6 for an estimate of the end-member helium isotope ratio (R = 3He/4He and Ra = Rair). This value falls well within the range of R/Ra = 5-7 generally observed for helium at subduction zone volcanic systems. At NW Rota #1, we found a strong helium plume reaching a maximum ? 3He = 320% at 460 m depth. Surprisingly, the estimate for the end-member 3He /4He at NW Rota gave R/Ra = 8.4, outside the range normally found at subduction zones and similar to that observed along MOR spreading centers. NW Rota #1 is located about 15 km west of the main arc and is part of a cross-arc volcanic chain. Craig et al. [EOS 68, No. 44, p.1531, 1987] found a similar value of R/Ra = 8.6 in vent fluids in the Mariana Trough back-arc system at 18° 13'N. Thus the higher 3He/4He ratio at NW Rota may reflect an affinity to the back-arc spreading center as opposed to a pure arc component.

Lupton, J. E.; Baker, E. T.; Embley, R. W.; Resing, J. E.; Massoth, G. J.; Nakamura, K.; Greene, R.; Walker, S.; Lebon, G.

2003-12-01

9

The INGV's new OBS\\/H: Analysis of the signals recorded at the Marsili submarine volcano  

Microsoft Academic Search

The ocean bottom seismometer with hydrophone deployed on the flat top of the Marsili submarine volcano (790 m deep) by the Gibilmanna OBS Lab (CNT–INGV) from 12th to 21st July, 2006, recorded more than 1000 transient seismic signals. Nineteen of these signals were associated with tectonic earthquakes: 1 teleseismic, 8 regional (located by INGV) and 10 small local seismic events (non

Antonino D'Alessandro; Giuseppe D'Anna; Dario Luzio; Giorgio Mangano

2009-01-01

10

A Miocene submarine volcano at Low Layton, Jamaica  

NASA Astrophysics Data System (ADS)

A submarine fissure eruption of Upper Miocene age produced a modest volume of alkaline basalt at Low Layton, on the north coast of Jamaica. The eruption occurred in no more than a few hundred meters of water and produced a series of hyaloclastites, pillow breccias and pillow lavas, massive lavas, and dikes with an ENE en echelon structure. The volcano lies on the trend of one of the island's major E-W strike-slip fault zones; the Dunavale Fault Zone. The K-Ar age of the eruption of 9.5 plus or minus 0.5 Ma. B.P. corresponds to an extension of the Mid-Cayman Rise spreading center inferred from magnetic anomalies and bathymetry of the Cayman Trough to the north and west of Jamaica. The Low Layton eruption was part of the response of the strike-slip fault systems adjacent to this spreading center during this brief episode of tectonic readjustment.

Wadge, G.

11

Southern Kermadec submarine caldera arc volcanoes (SW Pacific): caldera formation by effusive and pyroclastic eruption  

Microsoft Academic Search

Three newly identified submarine caldera volcanoes (Brothers, Healy, and Rumble II West), of the southern Kermadec arc (within water depths <1500 m), provide new insights into modes of submarine arc caldera formation. Swath MR1 data, seafloor photography, and rock dredge sampling establish the edifice and caldera morphology, outcrop volcanology, magma compositions, and petrography and rock properties of erupted components for

I. C Wright; J. A Gamble

1999-01-01

12

Modelling submarine pyroclastic flows at the Soufrière Hills volcano, Montserrat  

NASA Astrophysics Data System (ADS)

Submarine sedimentary flows are notoriously difficult to observe directly and interpreting their deposits to gain insight to the parent flows can be problematic. Pyroclastic flows from the Soufrière Hills volcano, Montserrat, which entered the ocean and deposited particles over the sea bed are a notable exception. In this case, from monitoring of the volcano, the mass of particulate released and the duration of the flow can be estimated accurately. Furthermore research cruises have imaged, cored the ocean bed and measured the distribution and composition of the deposit left by these flows over much of their runout. These observations therefore form a unique dataset in which both source conditions and final deposit are relatively well constrained. Mathematically modelling long runout sedimentary flows can also present several difficulties. Over these length and time scales, it is not feasible to simulate directly all of the fluid and particulate motions and so reduced models have been developed to capture the dominant processes and features of the flows. These have often been calibrated by laboratory scale experiments - but now with this data from the Soufrière Hills volcano, it is possible to compare model predictions with a natural scale event. Our model is based upon a shallow layer formulation, assuming hydrostatic balance in the vertical to leading order. The downslope motion of the sediment-laden fluid is driven by gravitational forces, associated with the density difference between the intruding and surrounding fluid. Particles settle out of the current to the underlying boundary, reducing the density difference, slowing the motion and forming the deposit. We develop a model that expresses conservation of fluid and particulate mass and a balance of streamwise momentum. This system of equations is integrated numerically to reveal the temporal and spatial evolution and asymptotic methods are used to reveal the dynamical controls on the runout. The theoretical predictions are then compared to the observations of the submarine deposit at Montserrat and it is shown that this relatively simple model is able to reproduce the field measurements quite accurately.

Hogg, A. J.; Goater, A.

2011-12-01

13

Growth and collapse of Waianae Volcano, Hawaii, as revealed by exploration of its submarine flanks  

Microsoft Academic Search

Wai‘anae Volcano comprises the western half of O‘ahu Island, but until recently little was known about the submarine portion of this volcano. Seven new submersible dives, conducted in 2001 and 2002, and multibeam bathymetry offshore of Wai‘anae provide evidence pertaining to the overall growth of the volcano's edifice as well as the timing of collapses that formed the Wai‘anae slump

Michelle L. Coombs; David A. Clague; Gregory F. Moore; Brian L. Cousens

2004-01-01

14

Growth and collapse of Waianae Volcano, Hawaii, as revealed by exploration of its submarine flanks  

Microsoft Academic Search

Wai`anae Volcano comprises the western half of O`ahu Island, but until recently little was known about the submarine portion of this volcano. Seven new submersible dives, conducted in 2001 and 2002, and multibeam bathymetry offshore of Wai`anae provide evidence pertaining to the overall growth of the volcano's edifice as well as the timing of collapses that formed the Wai`anae slump

Michelle L. Coombs; David A. Clague; Gregory F. Moore; Brian L. Cousens

2004-01-01

15

Rapid rates of growth and collapse of Monowai submarine volcano in the Kermadec Arc  

NASA Astrophysics Data System (ADS)

Most of Earth's volcanoes are under water. As a result of their relative inaccessibility, little is known of the structure and evolution of submarine volcanoes. Advances in navigation and sonar imaging techniques have made it possible to map submarine volcanoes in detail, and repeat surveys allow the identification of regions where the depth of the sea floor is actively changing. Here we report the results of a bathymetric survey of Monowai submarine volcano in the Tonga-Kermadec Arc, which we mapped twice within 14 days. We found marked differences in bathymetry between the two surveys, including an increase in seafloor depth up to 18.8m and a decrease in depth up to 71.9m. We attribute the depth increase to collapse of the volcano summit region and the decrease to growth of new lava cones and debris flows. Hydroacoustic T-wave data reveal a 5-day-long swarm of seismic events with unusually high amplitude between the surveys, which directly link the depth changes to explosive activity at the volcano. The collapse and growth rates implied by our data are extremely high, compared with measured long-term growth rates of the volcano, demonstrating the pulsating nature of submarine volcanism and highlighting the dynamic nature of the sea floor.

Watts, A. B.; Peirce, C.; Grevemeyer, I.; Paulatto, M.; Stratford, W.; Bassett, D.; Hunter, J. A.; Kalnins, L. M.; de Ronde, C. E. J.

2012-07-01

16

Hf, Pb, Sr, and Nd Isotope Geochemistry of Submarine Lavas from Hualalai Volcano, Hawaii  

NASA Astrophysics Data System (ADS)

The volcanoes of the Hawaiian islands are distributed in two parallel trends ('Loa' and 'Kea'), whose rocks are characterized by general geochemical differences. It is broadly accepted that Hawaiian plume is composed of several components, but the chemical structure of Hawaiian plume remains a matter of considerable debate. Hualalai volcano, the third youngest on the island of Hawaii and located on Loa trend, has been in the post shield alkalic stage for >100 ky. The study of the deep submarine ridges of this volcano has not been previously conducted. Many of submarine ridge lavas are older than any exposed on land, and extend our view of Hualalai magmatism back in time. To identify source materials involved in Hualalai ridge volcanism can provide constraints on the chemical structure of the Hawaiian plume. We analyzed Hf, Pb, Sr, Nd isotopic compositions and trace element contents of 16 lava samples from the submarine ridges of Hualalai. The samples were collected from North Kona region at 2700 - 3500 m water depth by 2001 Kaiko dive (K219) and at 2100 - 4500 m depth by 2002 Shinkai 6500 dives (S690, S692). It is considered that these samples are older than 105 ka, and are erupted at the pre-shield or shield stage of this volcano based on the stratigraphy and lithology. Isotopic compositions of the lavas have 87 Sr/86Sr ratios ranging from 0.703638 to 0.703813, 143Nd/144Nd from 0.512932 to 0.512946, 176Hf/177Hf from 0.2830988 to 0.2831234, 206Pb/204Pb from 18.1554 to 18.2663, 207Pb/204Pb from 15.4488 to 15.5518, and 208Pb/204Pb from 37.8661 to 38.2583. Hf, Nd, Sr isotopic compositions of the basalt samples are similar to, and overlap with the data previously reported for shield stage tholeiite from Hualalai and older tholeiite (>100ka) from Mauna Loa. Some of new Pb isotopic data have higher 207Pb/204Pb and 208Pb/204Pb, for a given 206Pb/204Pb, than published data from Mauna Loa and Hualalai. The results indicate that the Loa Pb isotope signature of the Hualalai source was present before 105 ka.

Yamasaki, S.; Kani, T.; Hanan, B. B.; Nohda, S.

2005-12-01

17

Submarine landslide triggered by eruption recorded by in-situ hydrophone at NW Rota-1 submarine volcano, Mariana Arc (Invited)  

NASA Astrophysics Data System (ADS)

An expedition to NW Rota-1, Mariana Arc, in March 2010 with R/V Kilo Moana and ROV Jason found that the submarine volcano (summit depth 520 m) was still erupting more or less continuously as has been observed since 2004, In addition, the expedition also discovered that a major landslide had occurred since the last visit in April 2009, demonstrating the dynamic processes of eruption, collapse, and regrowth in the submarine arc environment. The dive observations reveal the responses of the volcano’s magmatic and hydrothermal systems to such a collapse, as well as how the resident chemosynthetic biological community has responded to the event. The morphologic changes from the landslide can be quantified by comparing multibeam bathymetric surveys between 2009 and 2010. The headwall of the slide is now ~100 m north of the former summit ridge where depth changes up to -90 m occurred between surveys. The slide excavated material from the upper southern slope of the volcano to a distance of 3.5 km downslope, and deposited material between 2-8 km from the summit down to at least 2800 m on the volcano flank. The area and volume of slide deposits (positive depth changes) are 7.1 x 106 m2 and 5.3 x 107 m3, respectively, and the maximum thickness is +42 m. The area and volume of material removed by the slide (negative depth changes) are 2.2 x 106 m2 and -4.1 x 107 m3, respectively. We have found no evidence for a local tsunami generated by this event. The changes in morphology near the summit show that the landslide primarily removed loose volcaniclastic deposits that had accumulated near the active eruptive vent, exposing an underlying stock-like core of resistant intrusive rocks and massive lavas at the summit. During March 2010, there were at least 5 active eruptive vents, located along a line 200-m long, that changed between active and inactive day-to-day and even hour-to-hour, suggesting that the near-surface magmatic plumbing system was still reorganizing after the slide. The landslide also had a major impact on the resident chemosynthetic biological community at NW Rota-1, which previously included two species of shrimp in about equal numbers. However, after the landslide, the Alvinocaris shrimp species was almost wiped out, whereas the Opaepele loihi shrimp had thousands of new recruits. One instrument mooring was moved 1 km downslope and buried by the landslide and 2 others were destroyed. A hydrophone mooring deployed ~150 m west of the summit survived and recorded the sounds of eruptive activity since February 2009. After months of continuous, short duration (~1 min) explosions, the landslide event occurred within a 5-6 hr period on 14 August 2009 during a three-day interval of intense, continuous eruption that apparently triggered the landslide. This landslide/eruption acoustic signal was the largest single event during the two years of monitoring. The hydrophone mooring also showed evidence of having impacted the seafloor, possibly due to the strong currents generated by the slide.

Chadwick, B.; Dziak, R. P.; Embley, R. W.; Tunnicliffe, V.; Sherrin, J.; Cashman, K. V.; Deardorff, N.

2010-12-01

18

Submarine Strombolian Eruptions Observed at NW Rota1 Volcano, Mariana Arc  

Microsoft Academic Search

Extraordinary video and hydrophone observations of a submarine explosive eruption were made with a remotely operated vehicle in April 2006 at a depth of 550-560 m on NW Rota-1, a conical, basaltic-andesite submarine volcano in the Mariana arc. The observed eruption evolved from effusive to explosive, while the eruption rate increased from near zero to 10-100 m3\\/hr. During the peak

W. W. Chadwick; K. V. Cashman; R. W. Embley; R. P. Dziak; C. de Ronde; H. Matsumoto; N. Deardorff; S. G. Merle

2007-01-01

19

Submarine geology of Hana Ridge and Haleakala Volcano's northeast flank, Maui  

Microsoft Academic Search

We present a morphostructural analysis of the submarine portions of Haleakala Volcano and environs, based upon a 4-year program of geophysical surveys and submersible explorations of the underwater flanks of Hawaiian volcanoes that was conducted by numerous academic and governmental research organizations in Japan and the U.S. and funded primarily by the Japan Agency for Marine–Earth Science and Technology. A

Barry W. Eakins; Joel E. Robinson

2006-01-01

20

New submarine volcanoes in the Okinawa back-arc opening system  

Microsoft Academic Search

The results of a series of geological and geophysical observations, it is now better known that about 11 new submarine volcanoes are developing in the southern part of the Okinawa back-arc spreading center. These volcanoes, at the water depth from 200 V 1500 meters, were first detected by a 38 kHz single-beam echo- sounding system. The images not only show

C. Lee

2008-01-01

21

Flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano  

NASA Astrophysics Data System (ADS)

The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1-2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 ± 0.6 Tg a-1, where the magmatic gases driving eruptions at NW Rota-1 are primarily H2O, SO2, and CO2. Instantaneous fluxes varied by a factor of ˜100 over the deployment. Using melt inclusion information to estimate the concentration of CO2 in the explosive gases as 6.9 ± 0.7 wt %, we calculate an annual CO2 eruption flux of 0.4 ± 0.1 Tg a-1. This result is within the range of measured CO2 fluxes at continuously erupting subaerial volcanoes, and represents ˜0.2-0.6% of the annual estimated output of CO2from all subaerial arc volcanoes, and ˜0.4-0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO2 to the shallow ocean.

Dziak, R. P.; Baker, E. T.; Shaw, A. M.; Bohnenstiehl, D. R.; Chadwick, W. W.; Haxel, J. H.; Matsumoto, H.; Walker, S. L.

2012-11-01

22

Shoshonitic magmas in nascent arcs: New evidence from submarine volcanoes in the northern Marianas  

Microsoft Academic Search

Volcanoes in the northern Mariana arc between Uracas (lat 20°N) and Minami Iwo Jima (24°N) are very active yet entirely submarine. In contrast to the predominantly low-K basaltic magmas of the central Mariana arc, the northern Mariana arc is dominated by more siliceous melts in the south and by shoshonites in the north. The northern arc melts have enrichments in

Robert J. Stern; Sherman H. Bloomer; Ping-Nan Lin; Emi Ito; Julie Morris

1988-01-01

23

Evolution of the Hawaiian Plume: Evidence from Submarine Haleakala Volcano (Hana Ridge), Hawaii  

NASA Astrophysics Data System (ADS)

Hana Ridge is the submarine portion of the east rift zone of Haleakala Volcano, Hawaii. At 140 km long, Hana Ridge is the longest submarine rift zone in the Hawaiian Island chain and has developed a complex morphology compared to other Hawaiian rift zones, such as Puna Ridge. The main ridge comprises two or three subparallel or subjacent ridges with distinct morphological expressions related to sequential accretionary stages of the shield-building phase of Haleakala volcano. In order to investigate the geochemical evolution of Haleakala shield-building, we sampled several sections of Hana Ridge on six dives with ROV Kaiko and Shinkai 6500 submersible, both operated by JAMSTEC, in 2001 and 2002. We report new geochemical data for basalt samples from these six dives on Hana Ridge. All the recovered rocks are primitive tholeiites and picrites and more than half of them, those obtained in the deeper portions of the ridge, are picrites. Major and trace elements of the submarine Hana ridge rocks are similar to modern Kilauea and unlike Honomanu series lavas. Our results indicate that the mantle plume source for the Haleakala shield has changed over time from Kilauea-like compositions (high La/Sm, low Zr/Nb) in the submarine lavas to Mauna Loa-like compositions (lower La/Sm, higher Zr/Nb) in the subaerial Honomanu shield lavas. Moreover, the submarine stages show a gradual, but irregular, trend from higher to lower La/Sm with decreasing water depth (inferred to be decreasing age). We infer that Haleakala volcano originally had typical Hawaiian tholeiite magma compositions whose source material was similar to present-day Kilauea volcano and that the magma source became more Mauna Loa-like during growth of Haleakala volcano.

Johnson, K. T.; Ren, Z.; Takahashi, E.; Orihashi, Y.

2002-12-01

24

Gravitational tectonics at Mt Haddington, an Antarctic submarine / subglacial volcano  

NASA Astrophysics Data System (ADS)

Mt. Haddington, James Ross Island, Antarctic Peninsula, is a Miocene-recent volcanic complex erupted in marine and ice-shelf conditions. It is 60 km in diameter and 1800 m high, and is surrounded partially by a raised ring of sedimentary and volcanic formations. The sedimentary strata are mainly Cretaceous clay-rich detrital rocks and are up to 6 km thick below the volcano. The volcano is mainly composed of huge lava deltas with <1000m-thick hyaloclastite units under pahoehoe flows. We have analysed the structural deformation around the volcano to assess the role of gravitational loading on sediment deformation and consequent height changes of important paleoenvironmental marker horizons. The west side of the volcano is near the Antarctic peninsular, and the edge of the Weddel sea basin. Structures record an early tilting, then strike-slip deformation parallel to the Peninsula prior to volcanism. Further tilting occurred during volcanism with several 100’s m displacement along bedding-parallel thrusts. The thrusts are intimately linked to transtensional faults and are orientated nearly radial to the volcano. Remarkably little deformation and tilting are observed on the volcano edifice itself, and sediments exposed below the edifice in glacial valleys show only compaction. Thus the volcano has settled into the basin, compressing the substrata, but extruding it only at the edges. Deformation is most intense where the Peninsula constrained the radial expansion. To the east, open the Weddel Sea Basin the deformation is much less intense, but radial expansion is greater.

van Wyk de Vries, B.; Oehler, J.-F.; Smellie, J.

2003-04-01

25

Argon-40: excess in submarine pillow basalts from kilauea volcano, hawaii.  

PubMed

Submarine pillow basalts from Kilauea Volcano contain excess radiogenic argon-40 and give anomalously high potassium-argon ages. Glassy rims of pillows show a systematic increase in radiogenic argon-40 with depth, and a pillow from a depth of 2590 meters shows a decrease in radiogenic argon40 inward from the pillow rim. The data indicate that the amount of excess radiogenic argon-40 is a direct function of both hydrostatic pressure and rate of cooling, and that many submarine basalts are not suitable for potassium-argon dating. PMID:17812284

Dalrymple, G B; Moore, J G

1968-09-13

26

Predicting the Timing and Location of the next Hawaiian Volcano  

ERIC Educational Resources Information Center

The wealth of geologic data on Hawaiian volcanoes makes them ideal for study by middle school students. In this paper the authors use existing data on the age and location of Hawaiian volcanoes to predict the location of the next Hawaiian volcano and when it will begin to grow on the floor of the Pacific Ocean. An inquiry-based lesson is also…

Russo, Joseph; Mattox, Stephen; Kildau, Nicole

2010-01-01

27

Predicting the Timing and Location of the next Hawaiian Volcano  

ERIC Educational Resources Information Center

|The wealth of geologic data on Hawaiian volcanoes makes them ideal for study by middle school students. In this paper the authors use existing data on the age and location of Hawaiian volcanoes to predict the location of the next Hawaiian volcano and when it will begin to grow on the floor of the Pacific Ocean. An inquiry-based lesson is also…

Russo, Joseph; Mattox, Stephen; Kildau, Nicole

2010-01-01

28

Newly discovered submarine flank eruption at Stromboli volcano (Aeolian Islands, Italy)  

Microsoft Academic Search

The NW submarine portion of Stromboli volcano has been investigated by deep-towed sidescan sonar, bathymetric surveys, video camera runs and dredging during two research cruises in 2002 and 2004. The surveys resulted in the identification of an extensive pillow lava field (106-107m3) at about 2300 m of water depth and 9 km from the shoreline of Stromboli Island. The pillow

A. Di Roberto; A. Bertagnini; M. Pompilio; F. Gamberi; M. P. Marani; A. M. Rosi

2008-01-01

29

Long-term explosion records from two erupting submarine volcanoes in the Mariana and Tonga island-arcs  

NASA Astrophysics Data System (ADS)

Records of explosive activity longer than a few weeks are rare for subaerial volcanoes, and nonexistent for submarine volcanoes. From February 2008 to February 2009, we recorded a year long, continuous acoustic and volcanic plume record from NW Rota-1, an erupting submarine volcano located within the Mariana Arc. From December 2008 to May 2009, we also obtained acoustic records of ongoing explosion and tremor activity at West Mata, a submarine volcano in the NE Lau basin near the Tofua volcanic-arc. At NW Rota-1, a hydrophone and turbidity/temperature sensor were moored ~150 m from the volcano’s summit vent (520 m deep). The volcano exhibited frequent degassing explosions lasting 60-120 s, separated by quiet periods of 10-30 s, for the entire 12-months resulting in >284,000 discrete explosion events. The explosions are broadband (1-80 Hz) with typical source levels of 191 dB re ?Pa @ 1m. Harmonic tremor is also present at times in the explosions, typically with <5 Hz fundamentals and extremely high-amplitude overtone peaks near 30 Hz. The fundamentals are likely due to resonance of the entire volcanic edifice, while the peak overtone may represent reverberation of an internal structure, possibly the conduit feeding the summit vent. The hydrophone also documents a 103 decrease in explosion amplitude over the year, marked by a sharp reduction after 6 mos, which may be part of the typical eruption cycle or due to burial of the vent by accumulated ejecta. Explosions at the summit vent produced a steady series of volcanic plumes that carried ash and hydrothermal precipitates into the water column. Hundreds of short-lived turbidity spikes are present, with no long periods of quiescence, indicating changes in explosion intensity did not affect the pattern of volcanic plume creation. Our data are the first to confirm the frequent creation and dispersal of submarine volcanic plumes on a year-long scale. In December 2008 a moored hydrophone (250 Hz) was deployed ~30 km from West Mata, a near-arc boninite volcano discovered actively erupting the month before. An ROV cruise in May 2009 deployed two short-term, high-frequency (1024 Hz) hydrophones within 50 m of the Hades volcanic vent (1208 m deep). Both the long-term and in situ hydrophones detected explosive activity as well as both mono- and polychromatic volcanic tremor throughout their records. ROV video shows the acoustic signals are from violent degassing bursts from within lava extruding at the Hades vent (summit of West Mata). The explosions exhibit both short (10s of sec) and long (2-10 min) duration modes of cyclic activity. Many explosion signals also show harmonic tremor within their codas indicative of resonance from within the volcanic edifice. Frequently the explosion records are overlapped by monochromatic tremor from a narrow band within a range from 20-100 Hz. The source of this resonance is not yet clear (although not man-made) and is possibly from a nearby, unseen vent or magma movement within the volcanic edifice.

Dziak, R. P.; Embley, R. W.; Baker, E. T.; Chadwick, W. W.; Resing, J.; Matsumoto, H.; Walker, S. L.; Bohnenstiehl, D. R.; Klink, H.

2009-12-01

30

Sector collapse at Kick 'em Jenny submarine volcano (Lesser Antilles): numerical simulation and landslide behaviour  

NASA Astrophysics Data System (ADS)

Kick 'em Jenny volcano is the only known active submarine volcano in the Lesser Antilles. It lies within a horseshoe-shaped structure open to the west northwest, toward the deep Grenada Basin. A detailed bathymetric survey of the basin slope at Kick 'em Jenny and resulting high-resolution digital elevation model allowed the identification of a major submarine landslide deposit. This deposit is thought to result from a single sector collapse event at Kick 'em Jenny and to be linked to the formation of the horseshoe-shaped structure. We estimated the volume and the leading-edge runout of the landslide to be ca. 4.4 km3 and 14 km, respectively. We modelled a sector collapse event of a proto Kick 'em Jenny volcano using VolcFlow, a finite difference code based on depth-integrated mass and momentum equations. Our models show that the landslide can be simulated by either a Coulomb-type rheology with low basal friction angles (5.5°-6.5°) and a significant internal friction angle (above 17.5°) or, with better results, by a Bingham rheology with low Bingham kinematic viscosity (0 < ? B < 30 m2/s) and high shear strength (130 < ? ? 180 m2/s2). The models and the short runout distance suggest that the landslide travelled as a stiff cohesive flow affected by minimal granular disaggregation and slumping on a non-lubricated surface. The main submarine landslide deposit can therefore be considered as a submarine mass slide deposit that behaved like a slump.

Dondin, Frédéric; Lebrun, Jean-Frédéric; Kelfoun, Karim; Fournier, Nicolas; Randrianasolo, Auran

2012-03-01

31

Transition from circular to stellate forms of submarine volcanoes  

NASA Astrophysics Data System (ADS)

Large volcanic islands and guyots have stellate forms that reflect the relief of radiating volcanic rift zones, multiple volcanic centers, and embayments due to giant flank failures. Small mid-ocean ridge volcanoes, in contrast, are commonly subcircular in plan view and show only embryonic rift zones. In order to characterize the transition between these two end-members the morphology of 141 seamounts and guyots was studied using the shape of the depth contour at half the height of each edifice. Irregularity was characterized by measuring perimeter distance, elongation, and moment of inertia of the contours, assuming an "ideal" edifice is circular. The analysis reveals a general transition over 2-4 km edifice height (best transition estimate 3 km), while some large edifices 4-5 km high show no major embayments or ridges, suggesting considerable variation in the effectiveness of mechanisms that cause flank instability and growth of rift zones. The various origins of the transition are discussed, and the upper limit of magma chambers, many of which lie above the basement of the larger edifices, is proposed to affect the morphologic complexity via a number of mechanisms and is an important factor affecting the mode of growth. The origins of the truncated cone shape of mid-ocean ridge volcanoes are also discussed. Of the eruption mechanisms that have been proposed to explain their flat summits, the most likely mechanisms involve eruption from small ephemeral magma bodies lying within the low-density upper oceanic crust. The discussion includes speculations on factors affecting the depths of magma chambers beneath oceanic volcanoes. Supporting table is available via Web browser or via Anonymous FTP from ftp://kosmos.agu.org, directory "append" (Username = "anonymous", Password ="guest"); subdirectories in the ftp site are arranged by paper number. Information on searching and submitting electronic supplements is found at http://www.agu.org/pubs/csupp_about.html.

Mitchell, Neil C.

2001-02-01

32

Potential-field modeling of collapse-prone submarine volcanoes in the southern Tyrrhenian Sea (Italy)  

Microsoft Academic Search

Hydrothermal alteration may weaken volcanic rocks, causing the gravitational instability of portions of active volcanoes with potentially hazardous collapses. Here we show high-resolution multibeam, magnetic and gravity surveys of the Marsili seamount, the largest active volcano of Europe located in the southern Tyrrhenian back-arc basin. These surveys reveal zones with exceptionally low densities and with vanishing magnetizations, due probably to

F. Caratori Tontini; L. Cocchi; F. Muccini; C. Carmisciano; M. Marani; E. Bonatti; M. Ligi; E. Boschi

2010-01-01

33

Tremor Source Location at Okmok Volcano  

NASA Astrophysics Data System (ADS)

Initial results using an amplitude-based tremor location program have located several active tremor episodes under Cone A, a vent within Okmok volcano's 10 km caldera. Okmok is an andesite volcano occupying the north-eastern half of Umnak Island, in the Aleutian islands. Okmok is defined by a ~2000 y.b.p. caldera that contains multiple cinder cones. Cone A, the youngest of these, extruded lava in 1997 covering the caldera floor. Since April 2003, continuous seismic data have been recorded from eight vertical short-period stations (L4-C's) installed at distances from Cone A ranging from 2 km to 31 km. In 2004 four additional 3- component broadband stations were added, co-located with continuous GPS stations. InSAR and GPS measurements of post-eruption deformation show that Okmok experienced several periods of rapid inflation (Mann and Freymueller, 2002), from the center of the 10 km diameter caldera. While there are few locatable VT earthquakes, there has been nearly continuous low-level tremor with stronger amplitude bursts occurring at variable rates and durations. The character of occurrence remained relatively constant over the course of days to weeks until the signal ceased in mid 2005. Within any day, tremor behavior remains fairly consistent, with bursts closely resembling each other, suggesting a single main process or source location. The tremor is composed of irregular waves with a broad range of frequencies, though most energy resides between ~2 Hz and 6 Hz. Attempts to locate the tremor using traditional arrival time methods fail because the signal is emergent, with envelopes too ragged to correlate on time scales that hold much hope for a location. Instead, focus was shifted to the amplitude ratios at various stations. Candidates for the tremor source include the center of inflation and Cone A, 3 km to the south-west. For all dates on record, data were band pass filtered between 1 and 5 Hz, then evaluated in 20.48 second windows (N=2048, sampling rate=100 Hz), at 20 second intervals. Root-mean- square (rms) values were then calculated for each window of data. The ratios of these RMS amplitudes were used to investigate the tremor behavior. The ratio changes between tremor and non-tremor events suggest that the sources for episodes were closer to Cone A (and station OKCF) than they were to other locales in the caldera. Methods from Battaglia's PhD thesis (2001) were used as guidelines for a tremor location program based on amplitude decay. Written in MATLAB®, this program can be run in near-real time to estimate the tremor source location and strength. Further refinement is underway, as is an examination of all other days that have suitable data .

Reyes, C. G.; McNutt, S. R.

2007-12-01

34

Submarine geology of Hana Ridge and Haleakala Volcano's northeast flank, Maui  

USGS Publications Warehouse

We present a morphostructural analysis of the submarine portions of Haleakala Volcano and environs, based upon a 4-year program of geophysical surveys and submersible explorations of the underwater flanks of Hawaiian volcanoes that was conducted by numerous academic and governmental research organizations in Japan and the U.S. and funded primarily by the Japan Agency for Marine-Earth Science and Technology. A resulting reconnaissance geologic map features the 135-km-long Hana Ridge, the 3000 km2 Hana slump on the volcano's northeast flank, and island-surrounding terraces that are the submerged parts of volcanic shields. Hana Ridge below 2000 m water depth exhibits the lobate morphology typical of the subaqueously erupted parts of Hawaiian rift zones, with some important distinctions: namely, subparallel crestlines, which we propose result from the down-rift migration of offsets in the dike intrusion zone, and an amphitheater at its distal toe, where a submarine landslide has embayed the ridge tip. Deformation of Haleakala's northeast flank is limited to that part identified as the Hana slump, which lies downslope from the volcano's submerged shield, indicating that flank mobility is also limited in plan, inconsistent with hypothesized volcanic spreading driven by rift-zone dilation. The leading edge of the slump has transverse basins and ridges that resemble the thrust ramps of accretionary prisms, and we present a model to describe the slump's development that emphasizes the role of coastally generated fragmental basalt on gravitational instability of Haleakala's northeast flank and that may be broadly applicable to other ocean-island slumps.

Eakins, B. W.; Robinson, J. E.

2006-01-01

35

Repeat swath bathymetry surveys and the rates of growth and collapse of active submarine volcanoes  

NASA Astrophysics Data System (ADS)

Technological advances in shipboard navigation and swath bathymetry systems have made it possible to measure the depth of the seafloor to accuracies of better than 1-2 m, even in water depths > 2 km. Since 1992, there have been >500 swath bathymetry research cruises that have insonified ~6% of the ocean floor. The swath data have provided new information on seafloor processes, especially submarine volcanism, mass wasting and sediment transport from ocean margins to the deep-sea. Yet, there have been comparatively few repeat swath surveys. Recently, we compared swath data acquired in 1998, 2004, 2007 and 2011 on the Monowai submarine volcano and found dramatic differences in the depth of the seafloor between the 4 surveys. Within the 2011 survey alone, positive differences of +70 m and negative differences of up -18 m were found that indicate growth and collapse of the volcano on time-scales as short as a few days. The data are a reminder of how rapidly seafloor processes can occur. The seafloor is littered with seamounts, most of which are volcanic in origin, so comparative studies are needed in order to determine how many of them are collapsing and growing. Such studies would provide further insights into the dynamics of the seafloor and its implications for geohazards, including tsunami and sea-level change.

Watts, A. B.; Sonne 215 Shipboard Scientific Party

2012-04-01

36

New insights into hydrothermal vent processes in the unique shallow-submarine arc-volcano, Kolumbo (Santorini), Greece.  

PubMed

We report on integrated geomorphological, mineralogical, geochemical and biological investigations of the hydrothermal vent field located on the floor of the density-stratified acidic (pH ~ 5) crater of the Kolumbo shallow-submarine arc-volcano, near Santorini. Kolumbo features rare geodynamic setting at convergent boundaries, where arc-volcanism and seafloor hydrothermal activity are occurring in thinned continental crust. Special focus is given to unique enrichments of polymetallic spires in Sb and Tl (±Hg, As, Au, Ag, Zn) indicating a new hybrid seafloor analogue of epithermal-to-volcanic-hosted-massive-sulphide deposits. Iron microbial-mat analyses reveal dominating ferrihydrite-type phases, and high-proportion of microbial sequences akin to "Nitrosopumilus maritimus", a mesophilic Thaumarchaeota strain capable of chemoautotrophic growth on hydrothermal ammonia and CO2. Our findings highlight that acidic shallow-submarine hydrothermal vents nourish marine ecosystems in which nitrifying Archaea are important and suggest ferrihydrite-type Fe(3+)-(hydrated)-oxyhydroxides in associated low-temperature iron mats are formed by anaerobic Fe(2+)-oxidation, dependent on microbially produced nitrate. PMID:23939372

Kilias, Stephanos P; Nomikou, Paraskevi; Papanikolaou, Dimitrios; Polymenakou, Paraskevi N; Godelitsas, Athanasios; Argyraki, Ariadne; Carey, Steven; Gamaletsos, Platon; Mertzimekis, Theo J; Stathopoulou, Eleni; Goettlicher, Joerg; Steininger, Ralph; Betzelou, Konstantina; Livanos, Isidoros; Christakis, Christos; Bell, Katherine Croff; Scoullos, Michael

2013-08-13

37

Volcanoes  

ERIC Educational Resources Information Center

|Describes the forces responsible for the eruptions of volcanoes and gives the physical and chemical parameters governing the type of eruption. Explains the structure of the earth in relation to volcanoes and explains the location of volcanic regions. (GS)|

Kunar, L. N. S.

1975-01-01

38

Submarine volcanoes of the Kolumbo volcanic zone NE of Santorini Caldera, Greece  

NASA Astrophysics Data System (ADS)

The seafloor northeast of Santorini volcano in Greece consists of a small, elongated rifted basin that has been the site of recent submarine volcanism. This area lies within the Cyclades back-arc region of the present Hellenic subduction zone where the seafloor of the eastern Mediterranean Sea is descending beneath the Aegean microplate. The Cycladic region and the Aegean Sea as a whole are known to be regions of north-south back-arc extension and thinning of continental crust. Nineteen submarine volcanic cones occur within this small rift zone, the largest of these being Kolumbo which last erupted explosively in 1650 AD, causing significant damage and fatalities on the nearby island of Santorini. Previous SEABEAM mapping and seismic studies from HCMR indicate that many of the smaller v'olcanic cones have been built above the present seafloor, while others are partly buried, indicating a range of ages for the activity along this volcanic line. None of the cones to the northeast of Kolumbo had been explored in detail prior to a cruise of the E/V Nautilus (NA007) in August 2010. The ROV Hercules was used to explore the slopes, summits and craters of 17 of the 19 centers identified on multibeam maps of the area. Water depths of the submarine volcano's summits ranged from 18 to 450 m. In general, the domes/craters northeast of Kolumbo were sediment covered and showed little evidence of recent volcanic activity. Outcrops of volcanic rock were found in the crater walls and slopes of some of the cones but they typically consisted of volcanic fragments of pumice and lava that have been cemented together by biological activity, indicative of the lack of recent eruptions. Geochemical analysis of samples collected on the northeast cones showed evidence of low temperature hydrothermal circulation on the summit and upper flanks in the form of stream-like manganese precipitates emanating from pits and fractures.

Nomikou, P.; Carey, S.; Papanikolaou, D.; Croff Bell, K.; Sakellariou, D.; Alexandri, M.; Bejelou, K.

2012-06-01

39

Large Methane Plumes Formed by Hydrate Coated Gas Bubbles from a Deep-Sea Submarine Mud Volcano  

Microsoft Academic Search

Submarine mud volcanoes (SMVs) are major methane sources in the marine environment. Worldwide 103-105 SMVs are believed to release in total about 27 Mt CH4 yr-1. Results of the last decade \\\\'{ } s research suggest, that most of this methane, primarily released diffusively from deep-sea SMVs is immediately oxidised and, thus, has only little climatic impact. Recent hydroacoustic, visual

E. J. Sauter; S. I. Muyakshin; J. Charlou; M. Schlueter; A. Boetius; E. Damm; J. Foucher; M. Klages

2004-01-01

40

Methane discharge into the Black Sea and the global ocean via fluid flow through submarine mud volcanoes  

NASA Astrophysics Data System (ADS)

During the MARGASCH cruise M52/1 in 2001 with RV Meteor we sampled surface sediments from three stations in the crater of the Dvurechenskii mud volcano (DMV, located in the Sorokin Trough of the Black Sea) and one reference station situated 15 km to the northeast of the DMV. We analysed the pore water for sulphide, methane, alkalinity, sulphate, and chloride concentrations and determined the concentrations of particulate organic carbon, carbonate and sulphur in surface sediments. Rates of anaerobic oxidation of methane (AOM) were determined using a radiotracer ( 14CH 4) incubation method. Numerical transport-reaction models were applied to derive the velocity of upward fluid flow through the quiescently dewatering DMV, to calculate rates of AOM in surface sediments, and to determine methane fluxes into the overlying water column. According to the model, AOM consumes 79% of the average methane flux from depth (8.9 · 10 + 6 mol a - 1 ), such that the resulting dissolved methane emission from the volcano into the overlying bottom water can be determined as 1.9 · 10 + 6 mol a - 1 . If it is assumed that all submarine mud volcanoes (SMVs) in the Black Sea are at an activity level like the DMV, the resulting seepage represents less than 0.1% of the total methane flux into this anoxic marginal sea. The new data from the DMV and previously published studies indicate that an average SMV emits about 2.0 · 10 + 6 mol a - 1 into the ocean via quiescent dewatering. The global flux of dissolved methane from SMVs into the ocean is estimated to fall into the order of 10 + 10 mol a - 1 . Additional methane fluxes arise during periods of active mud expulsion and gas bubbling occurring episodically at the DMV and other SMVs.

Wallmann, Klaus; Drews, Manuela; Aloisi, Giovanni; Bohrmann, Gerhard

2006-08-01

41

Discovery of an Active Submarine Mud Volcano Along the Nootka Fault West of Vancouver Island  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes are a common feature in margin environments, but few of them have been documented in the Northeast Pacific. However, during a Hydrosweep bathymetric survey in July, 2001, and a follow-on sub-surface seismic survey in August two mud volcanoes were imaged along the Nootka Fault, 16-18 km west of Vancouver Island at a water depth of 2500 m. The southern volcano, called Maquinna, lies directly along the southern expression of the left lateral, strike slip Nootka Fault. It is 1.5 km across, has a breached caldera and two small summit craters, and it stands about 30 m above the seafloor. The base is bounded by a narrow moat, partially filled by Holocene sediments that are flat lying; older, underlying sediments show steep downwarping towards the sides of the volcano. Subsurface imaging shows a dramatic loss of reflectivity beneath the volcano mound, which may indicate significant mobilization of material. However, a very bright reflector is seen at about 400 m depth below the volcano. This reflector is too deep for stability of methane clathrate, and is interpreted as a zone of high fluid content. A CTD vertical cast above the summit of the volcano showed strong, co-registered thermal, particulate, and oxygen anomalies that extend 50 m up into the overlying water column. These data indicate that the volcano is actively venting warm hydrothermal fluids. The fluids are depleted in CO2, contain background concentrations of CH4, but show elevated H2 concentrations above ocean background water. Microscopic examination of the Nootka hydrothermal samples shows that they contain dense and morphologically diverse microbial communities in comparison to background seawater with cell densities of 106 cells/ml. Enrichment culturing indicates that these communities include both anaerobic and aerobic organisms, some of which are thermophilic with optimal growth temperatures in excess of 50 deg C. Some of these cultures can use methane oxidation as an energy source. Additional culturing experiments and analysis of preserved samples are underway to further characterize the microbes. To further understand the biogeochemical cycles at these sites, samples recently taken from piston cores and CTD casts in this region, are being surveyed for stable and radio carbon isotope signatures of CH4, dissolved inorganic carbon, organic carbon and phospholipid bacterial biomarkers. A second volcano lies ~ 8 km to the northwest of the Maquinna that has a less well defined seafloor expression. However, like Maquinna, seismic reflectivity is lost nearly completely beneath the mound, except for a very bright reflector at about 800 m depth. It is not yet known if this volcano is hydrothermally active. It is likely that high sediment accumulation and lateral tectonic compression associated with accretionary prism formation along the west coast of Vancouver Island support overpressuring of fluids at depth along the Nootka Fault zone, resulting in growth of the two volcanoes.

Riedel, M.; Riedel, M.; Kelly, D. S.; Delaney, J. R.; Spence, G. D.; Hyndman, R. D.; Hyndman, R. D.; Mayer, L.; Calder, B.; Lilley, M. D.; Olson, E. O.; Schrenk, M. O.; Coffin, R.

2001-12-01

42

Submarine tsunamigenic landslides at Stromboli Volcano: characterization and estimation of recurrence time  

NASA Astrophysics Data System (ADS)

Seafloor mapping and morphometric analysis of landslide scars can provide useful insights for marine geo-hazard assessment, as demonstrated by several studies performed on different geological settings. The availability of high-resolution multibeam bathymetry and long-range side scan sonar data on the submarine portions of Stromboli Volcano allow us to map and characterize the main mass-wasting features that affect, on the whole, about the 90% of its submarine extension. In particular, two main kinds of tsunamigenic landslides have been recognized and analyzed. Large-scale sector collapses (Fig. 1) are catastrophic events that mobilize 1-2 cubic kilometers of material, generating huge tsunami waves that may affect Stromboli and propagate in surrounding areas; related hazard is not very high, as they show recurrence periods of some (or more) thousand years. Conversely, medium-scale landslides are more hazardous, as they occur at higher frequency with respect to the previous events, i.e. from some hundreds up to few tens of years. These events are, however, able to generate local but severe tsunamis when occurring in shallow water, as demonstrated by the recent 2002 tsunamigenic landslides that struck the Stromboli coasts with waves up to 10 m-high. The aim of this contribution is thus to evidence the main predisposing factors, the possible recurrence time and the size of potentially induced tsunami for the different recognized landslides according to the available geologic constraints and historical tsunami report. Fig. 1 3D images of Eastern (a) and Northwestern (b) flank of Stromboli Volcano (vertical exaggeration 2x). Note the presence of scars in the upper part of the flank and debris avalanche deposits (i.e., megablocks) in the lower part. SdF: Sciara del Fuoco, Stromboli Cy: Stromboli Canyon

Casalbore, D.; Chiocci, F. L.; Romagnoli, C.; Bosman, A.

2010-12-01

43

Bacterial diversity in Fe-rich hydrothermal sediments at two South Tonga Arc submarine volcanoes.  

PubMed

Seafloor iron oxide deposits are a common feature of submarine hydrothermal systems. Morphological study of these deposits has led investigators to suggest a microbiological role in their formation, through the oxidation of reduced Fe in hydrothermal fluids. Fe-oxidizing bacteria, including the recently described Zetaproteobacteria, have been isolated from a few of these deposits but generally little is known about the microbial diversity associated with this habitat. In this study, we characterized bacterial diversity in two Fe oxide samples collected on the seafloor of Volcanoes 1 and 19 on the South Tonga Arc. We were particularly interested in confirming the presence of Zetaproteobacteria at these two sites and in documenting the diversity of groups other than Fe oxidizers. Our results (small subunit rRNA gene sequence data) showed a surprisingly high bacterial diversity, with 150 operational taxonomic units belonging to 19 distinct taxonomic groups. Both samples were dominated by Zetaproteobacteria Fe oxidizers. This group was most abundant at Volcano 1, where sediments were richer in Fe and contained more crystalline forms of Fe oxides. Other groups of bacteria found at these two sites include known S- and a few N-metabolizing bacteria, all ubiquitous in marine environments. The low similarity of our clones with the GenBank database suggests that new species and perhaps new families were recovered. The results of this study suggest that Fe-rich hydrothermal sediments, while dominated by Fe oxidizers, can be exploited by a variety of autotrophic and heterotrophic micro-organisms. PMID:20533949

Forget, N L; Murdock, S A; Juniper, S K

2010-12-01

44

Methane discharge from a deep-sea submarine mud volcano into the upper water column by gas hydrate-coated methane bubbles  

Microsoft Academic Search

The assessment of climate change factors includes a constraint of methane sources and sinks. Although marine geological sources are recognized as significant, unfortunately, most submarine sources remain poorly quantified. Beside cold vents and coastal anoxic sediments, the large number of submarine mud volcanoes (SMV) may contribute significantly to the oceanic methane pool. Recent research suggests that methane primarily released diffusively

Eberhard J. Sauter; Sergey I. Muyakshin; Jean-Luc Charlou; Michael Schlüter; Antje Boetius; Kerstin Jerosch; Ellen Damm; Jean-Paul Foucher; Michael Klages

2006-01-01

45

Isotope Compositions of Submarine Hana Ridge Lavas, Haleakala Volcano, Hawaii: Implications for Source Compositions, Melting Process and the Structure of the Hawaiian Plume  

Microsoft Academic Search

We report Sr, Nd, and Pb isotope compositions for 17 bulk-rock samples from the submarine Hana Ridge, Haleakala volcano, Hawaii, collected by three dives by ROV Kaiko during a joint Japan-US Hawaiian cruise in 2001. The Sr, Nd, and Pb isotope ratios for the submarine Hana Ridge lavas are similar to those of Kilauea lavas. This contrasts with the isotope

ZHONG-YUAN REN; TOMOYUKI SHIBATA; MASAKO YOSHIKAWA; KEVIN T. M. JOHNSON; EIICHI TAKAHASHI

2005-01-01

46

Submarine picritic basalts from Ko'olau Volcano, Hawai'i: Implications for parental magma compositions and mantle source  

NASA Astrophysics Data System (ADS)

Previous studies of Ko'olau Volcano subaerial basalts have invoked melting of recycled oceanic crust (garnet pyroxenite) as a mantle source to explain the unusually high SiO2 (53-55 wt.%), moderate MgO (6-8 wt.%) and low olivine contents (<5 vol.%) of these lavas. To evaluate whether such usual lavas form the bulk of Ko'olau Volcano, we sampled for the first time the dissected flanks of this volcano and the landslide blocks derived from Ko'olau and the volcanoes on the neighboring island of Molokai using the SHINKAI 6500 submersible, the remotely operated vehicle (ROV) KAIKO and dredging. Olivine-rich basalts (>10 vol.%) with high MgO contents (14 to 31.5 wt.%) are abundant among submarine Ko'olau lavas. Many of these picritic lavas have accumulated olivine, including xenocrysts with one or more subgrain boundaries. However, euhedral, undeformed olivine with forsterite contents of 88-90% and normal zoning is the dominant crystal type in these Ko'olau submarine basalts. Olivine CaO contents are moderate (0.16-0.27 wt%) and NiO contents are generally high (up to 0.60 wt%) compared to olivines from other Hawaiian volcanoes. These results indicate that subaerial Ko'olau exposures give a biased sampling of the volcano and that the olivines in these submarine lavas grew at crustal depths in parental magmas with MgO contents of at least 14-15 wt.%. Thus, they were primarily derived from melting peridotite, like other Hawaiian tholeiitic magmas. The wide range in olivine CaO contents indicates that there is a much greater range in Ko'olau parental magma compositions than observed for subaerial lavas.

Garcia, Michael O.

47

Morpho-structural setting of Stromboli volcano revealed by high-resolution bathymetry and backscatter data of its submarine portions  

NASA Astrophysics Data System (ADS)

The first high-resolution bathymetric and backscatter maps of offshore Stromboli Island are presented, together with an interpretation of its volcanic, structural and sedimentary features. The volcanic edifice is characterized by a sub-conical shape with a quasi-bilateral symmetry with respect to a NE-SW axis. The dimensions of the Strombolicchio volcanic centre, to the NE of Stromboli, have been restored by redrawing its morphology before wave action that eroded it in Late Quaternary time. On the NE submarine flank of Strombolicchio, a N64°E structural trend controls the shape of Strombolicchio Canyon. On the southern side of Stromboli, the submarine flank has a radial structural trend, possibly reflecting a volcanic stress regime. Landslide scars at various scales are ubiquitous on the submarine slopes of Stromboli. Repeated large-scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano, producing large debris avalanche deposits.

Bosman, Alessandro; Chiocci, Francesco L.; Romagnoli, Claudia

2009-11-01

48

Lava bubble-wall fragments formed by submarine hydrovolcanic explosions on L?'ihi Seamount and K?lauea Volcano  

Microsoft Academic Search

Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted\\u000a on L?'ihi Seamount and along the submarine east rift zone of K?lauea Volcano. The limu o Pele fragments are undegassed with\\u000a respect to H2O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths

David A. Clague; Alice S. Davis; James L. Bischoff; Jacqueline E. Dixon; Renee Geyer

2000-01-01

49

U-series disequilibrium of basaltic rocks from Kick'em-Jenny submarine volcano, Lesser Antilles island arc  

NASA Astrophysics Data System (ADS)

Kick'em Jenny (KEJ) submarine volcano located 9 km to the north of Grenada in the Lesser Antilles volcanic arc produces lavas ranging in composition from high MgO basalts to moderately evolved andesites. We have determined U-series disequilibria in 12 porphyritic lavas erupted from KEJ volcano by TIMS and MC-ICP-MS methods to constrain the timing and identify the processes creating the magma diversity observed. The SiO2 contents of samples studied here vary from 47 to 55 wt.% SiO2 while REE patterns evolve from slightly LREE enriched, MREE/HREE = 1 patterns to strongly LREE enriched, MREE depleted concave-up patterns. Separate dissolutions of sample KEJ100 indicate an external reproducibility (1s) of 0.7% for (230Th/238U) (n=4), 0.8% for (230Th/232Th) (n=4) and 0.6% for (226Ra/230Th) (n=3), respectively. For all sample, (234U/238U) lies within 0.7% of unity, suggesting that secondary alteration by seawater has not disturbed the U-series data significantly. Sample ages for these submarine erupted samples are unknown, resulting in uncertain values for initial (226Ra/230Th); however, 10 out of 12 of the measured (226Ra/230Th) range between 3.16 and 1.13 and are thus unequivocally young with respect to decay of 230Th and 231Pa since eruption. The U (0.535 - 4.876 ppm) and Th (1.25 - 10.78 ppm) concentrations increase with SiO2 contents. (230Th/232Th) has a restricted range, varying from 0.994 to 1.093 with the exception of one sample. (230Th/238U) ranges from 0.684 to 0.875 while (231Pa/235U) ranges from 1.76 up to 2.84, among the highest 231Pa excess in island arcs yet reported. These data confirm previous observations of the unusual behavior of KEJ lavas relative to global observations in having both large 238U and 231Pa excesses. Combined with (226Ra/230Th), these disequilibria observations require that 238U excesses reflect more than solely fluid addition to the mantle wedge from the subducted oceanic slab.

Huang, F.; Lundstrom, C. C.

2005-12-01

50

The 2002–2003 submarine gas eruption at Panarea volcano (Aeolian Islands, Italy): Volcanology of the seafloor and implications for the hazard scenario  

Microsoft Academic Search

A submarine gas eruption started in November 2002 offshore of Panarea volcano (Aeolian Islands, Italy). The intensity of the gas emission and the considerable anomalies of the geochemical and geophysical parameters have alarmed the volcanological community and the Italian Civil Protection Agency on the possibility that this activity may represent a volcanic unrest at Panarea volcano. We used a high

Alessandra Esposito; Guido Giordano; Marco Anzidei

2006-01-01

51

High-Temperature Hydrothermal Vent Field of Kolumbo Submarine Volcano, Aegean Sea: Site of Active Kuroko-Type Mineralization  

NASA Astrophysics Data System (ADS)

Kolumbo submarine volcano is located 7 km north-east of the island of Santorini in the Hellenic arc (Greece), and comprises one of about twenty submarine cones in a NE-trending rift zone. Kolumbo erupted explosively in 1649-50AD, causing 70 fatalities on Santorini. Kolumbo's crater is 1700 m in diameter, with a crater rim at 10 m below sea level and crater floor at depth of 505 m. Recent marine geological investigations, using ROVs, reveal a very active high-temperature hydrothermal vent field in the northeastern part of the Kolumbo crater floor, about 25,000 m2. Vent chimneys up to 4 m high are vigorously emitting colorless gas plumes up to 10 m high in the water column. Temperatures up to 220oC are recorded in vent fluids. Some vents are in crater- like depressions, containing debris from collapsed extinct chimneys. The entire crater floor of Kolumbo is mantled by a reddish-orange bacterial mat, and bacterial filaments of a variety of colors cling to chimneys in dense clusters. Glassy tunicates and anemones are common in lower-temperature environments on the crater floor. Most chimneys show a high porosity, with a central conduit surrounded by an open and very permeable framework of sulfides and sulfates, aiding fluid flow through the chimney walls. In the sulfate-rich samples, blades of euhedral barite and anhydrite crystals coat the outside of the chimney wall, and layers of barite alternate with sulfide in the interior. The dominant sulfides are pyrite, sphalerite, wurtzite, marcasite and galena. Crusts on extinct and lower-temperature chimneys are composed of amorphous silica, goethite and halite. Sulfur isotope composition of sulfates is virtually at sea water values, whereas the sulfides are more depleted. Elevated levels of copper, gold and silver are observed in bulk composition of chimney samples. Both the structural setting, character of the vent field and sulfide/sulfate mineralogy and geochemistry indicate on-going Kuroko-type mineralization in the Kolumbo submarine crater today.

Sigurdsson, H.; Carey, S.; Alexandri, M.; Vougioukalakis, G.; Croff, K.; Roman, C.; Sakellariou, D.; Anagnostou, C.; Rousakis, G.; Ioakim, C.; Gogou, A.; Ballas, D.; Misaridis, T.; Nomikou, P.

2006-12-01

52

Hydrothermal mineralization at Kick'em Jenny submarine volcano in the Lesser Antilles island arc  

NASA Astrophysics Data System (ADS)

Kick 'em Jenny (KeJ) is an active submarine volcano located in the Lesser Antilles island arc, ~7.5 km northwest of Grenada. Of the twelve eruptions detected since 1939, most have been explosive as evidenced by eyewitness accounts in 1939, 1974, and 1988 and the dominance of explosive eruption products recovered by dredging. In 2003, vigorous hydrothermal activity was observed in the crater of KeJ. Video footage taken by a remotely operated vehicle (ROV) during the cruise RB-03-03 of the R/V Ronald Brown documented the venting of a vapor phase in the form of bubbles that ascended through the water column and a clear fluid phase in the form of shimmering water. The shimmering water generally ascended through the water column but can also been seen flowing down gradient from a fissure at the top of a fine-grained sediment mound. These fine-grained sediment mounds are the only structure associated with hydrothermal venting; spire or chimney structures were not observed. Hydrothermal venting was also observed coming from patches of coarse-grained volcaniclastic sediment on the crater floor and from talus slopes around the perimeter of the crater. Samples were collected from these areas and from areas void of hydrothermal activity. XRD and ICPMS analyses of bulk sediment were carried out to investigate the geochemical relationships between sediment types. Sediment samples from the hydrothermal mound structures are comprised of the same components (plagioclase, amphibole, pyroxene, and scoria) as sediment samples from areas void of hydrothermal activity (primary volcaniclastic sediment) in the 500-63 ?m size range. High resolution grain size analyses show that >78% of sediment in the hydrothermal mound samples are between 63-2 ?m with 6-20% clay sized (<2 ?m) whereas <40% of the primary volcaniclastic sediment is between 63-2 ?m with ~2% clay sized. The presence of clay minerals (smectite, illite, talc, and I/S mixed layer) in the hydrothermal mound samples was confirmed x-ray diffraction analysis. Differences in major oxide composition of the two sediment types (depletion in Al2O3 but enrichments in MgO and Fe2O3* in the mound sample relative to primary volcaniclastic sediment) suggest that mound sediment has experienced hydrothermal alteration/mineralization. Elevated concentrations of As, Sb and Cu in the mound sediment also indicate a strong hydrothermal contribution. The bulk composition of the mound sediment can be reasonably modeled as a mixture of ~78% primary volcaniclastic sediment, ~30% alteration clay minerals, and ~2% pyrite. The percentage of clay required in the model is ~10% greater than the fraction (~20%) observed in the hydrothermal mound sample but some of the alteration products may consist of larger grains that have not been analyzed individually.

Olsen, R.; Carey, S.; Sigurdsson, H.; Cornell, W. C.

2011-12-01

53

Locating volcano-seismic signals in the presence of rough topography: wave simulations on Arenal volcano, Costa Rica  

Microsoft Academic Search

Quantifying the scattering effects of pronounced volcano topography on the seismic wavefield is an important component in locating and interpreting volcano seismic sources. In this study, we perform seismic wave simulations to quantify the scattering generated by a 3-D digital elevation map and 1-D velocity model of Arenal volcano, Costa Rica. Full waveform synthetic seismograms were generated using a 3-D

J. P. Métaxian; G. S. O'Brien; C. J. Bean; B. Valette; M. Mora

2009-01-01

54

Volcanoes  

NSDL National Science Digital Library

Volcanoes is part of an online series of modules entitled Exploring the Environment. Emphasizing an integrated approach to environmental Earth Science education through problem based-learning, this module asks students to look at four different situations involving volcanoes, research the situations, and make decisions about them. Information about the three volcanic areas under exploration (Mt. Hood, Kilauea, and Yellowstone) is given through maps, movies, and videos. Additional information covers plate tectonics, locations of volcanoes, volcano monitoring and hazards, how to deal with volcano threats, lavas, eruption types, and risk analysis. Once students have gone through the information, they make real-life decisions about building near volcanoes, and the possibility of eruptions in the near future. There are teacher resources, a reference for problem-based learning, and links for more information.

55

40Ar/39Ar geochronology of submarine Mauna Loa volcano, Hawaii  

NASA Astrophysics Data System (ADS)

New geochronologic constraints refine the growth history of Mauna Loa volcano and enhance interpretations of the petrologic, geochemical, and isotopic evolution of Hawaiian magmatism. We report results of 40Ar/39Ar incremental heating experiments on low-K, tholeiitic lavas from the 1.6 km high Kahuku landslide scarp cutting Mauna Loa's submarine southwest rift zone, and from lavas in a deeper section of the rift. Obtaining precise40Ar/39Ar ages from young, tholeiitic lavas containing only 0.2-0.3 wt.% K2O is challenging due to their extremely low radiogenic 40Ar contents. Analyses of groundmass from 45 lavas yield 14 new age determinations (31% success rate) with plateau and isochron ages that agree with stratigraphic constraints. Lavas collected from a 1250 m thick section in the landslide scarp headwall were all erupted around 470 ± 10 ka, implying an extraordinary period of accumulation of ˜25 mm/yr, possibly correlating with the peak of the shield-building stage. This rate is three times higher than the estimated vertical lava accumulation rate for shield-building at Mauna Kea (8.6 ± 3.1 mm/yr) based on results from the Hawaii Scientific Drilling Project. Between ˜470 and 273 ka, the lava accumulation rate along the southwest rift zone decreased dramatically to ˜1 mm/yr. We propose that the marked reduction in lava accumulation rate does not mark the onset of post-shield volcanism as previously suggested, but rather indicates the upward migration of the magma system as Mauna Loa evolved from a submarine stage of growth to one that is predominantly subaerial, thereby cutting off supply to the distal rift zone. Prior to ˜250 ka, lavas with Loihi-like isotopic signatures were erupted along with lavas having typical Mauna Loa values, implying greater heterogeneity in the plume source earlier in Mauna Loa's growth. In addition to refining accumulation rates and the isotopic evolution of the lavas erupted along the southwest rift zone, our new40Ar/39Ar results constrain the eruption of the Ninole Basalts from 227 to 108 ka and provide maximum estimates on the timing of the Ka Lae and South Kona landslides.

Jicha, Brian R.; Rhodes, J. Michael; Singer, Brad S.; Garcia, Michael O.

2012-09-01

56

Vailulu'u Seamount, Samoa: Life and death on an active submarine volcano  

PubMed Central

Submersible exploration of the Samoan hotspot revealed a new, 300-m-tall, volcanic cone, named Nafanua, in the summit crater of Vailulu’u seamount. Nafanua grew from the 1,000-m-deep crater floor in <4 years and could reach the sea surface within decades. Vents fill Vailulu’u crater with a thick suspension of particulates and apparently toxic fluids that mix with seawater entering from the crater breaches. Low-temperature vents form Fe oxide chimneys in many locations and up to 1-m-thick layers of hydrothermal Fe floc on Nafanua. High-temperature (81°C) hydrothermal vents in the northern moat (945-m water depth) produce acidic fluids (pH 2.7) with rising droplets of (probably) liquid CO2. The Nafanua summit vent area is inhabited by a thriving population of eels (Dysommina rugosa) that feed on midwater shrimp probably concentrated by anticyclonic currents at the volcano summit and rim. The moat and crater floor around the new volcano are littered with dead metazoans that apparently died from exposure to hydrothermal emissions. Acid-tolerant polychaetes (Polynoidae) live in this environment, apparently feeding on bacteria from decaying fish carcasses. Vailulu’u is an unpredictable and very active underwater volcano presenting a potential long-term volcanic hazard. Although eels thrive in hydrothermal vents at the summit of Nafanua, venting elsewhere in the crater causes mass mortality. Paradoxically, the same anticyclonic currents that deliver food to the eels may also concentrate a wide variety of nektonic animals in a death trap of toxic hydrothermal fluids.

Staudigel, Hubert; Hart, Stanley R.; Pile, Adele; Bailey, Bradley E.; Baker, Edward T.; Brooke, Sandra; Connelly, Douglas P.; Haucke, Lisa; German, Christopher R.; Hudson, Ian; Jones, Daniel; Koppers, Anthony A. P.; Konter, Jasper; Lee, Ray; Pietsch, Theodore W.; Tebo, Bradley M.; Templeton, Alexis S.; Zierenberg, Robert; Young, Craig M.

2006-01-01

57

Submarine pyroclastic deposits formed during the 20th May 2006 dome collapse of the Soufrière Hills Volcano, Montserrat  

NASA Astrophysics Data System (ADS)

The 20th May 2006 lava dome collapse of the Soufrière Hills Volcano, Montserrat, had a total non-dense rock equivalent (non-DRE) collapse volume of approximately 115 × 106 m3. The majority of this volume was deposited into the ocean. The collapse was rapid, 85% of the mobilized volume being removed in just 35 min, giving peak pyroclastic flow flux of 66 × 103 m3 s-1. Channel and levee facies on the submarine flanks of the volcano and formation of a thick, steep-sided ridge, suggest that the largest and most dense blocks were transported proximally as a high concentration granular flow. Of the submerged volume, 30% was deposited from the base of this granular flow, forming a linear, high-relief ridge that extends 7 km from shore. The remaining 70% of the submerged volume comprises the finer grain sizes, which were transported at least 40 km by turbidity currents on gradients of <2°. At several localities, the May 2006 distal turbidity currents ran up 200 m of topography and eroded up to 20 cm of underlying substrate. Multiple turbidites are preserved, representing current reflection from the graben margins and deflection around topography. The high energy of the May 2006 collapse resulted in longer submarine run out than the larger (210 × 106 m3) Soufrière Hills dome collapse in July 2003.

Trofimovs, J.; Foster, C.; Sparks, R. S. J.; Loughlin, S.; Le Friant, A.; Deplus, C.; Porritt, L.; Christopher, T.; Luckett, R.; Talling, P. J.; Palmer, M. R.; Le Bas, T.

2012-03-01

58

Volcanic construction of submarine Kermadec arc volcanoes from near-bottom sidescan sonar data collected by the Sentry AUV  

NASA Astrophysics Data System (ADS)

Seafloor mapping in the deep ocean has benefitted greatly from the advent and now routine use of autonomous underwater vehicles (AUVs) to collect areally extensive near-bottom bathymetric, photographic, hydrographic, and magnetic data. For geologic investigations, AUV-derived data is often supplemented by near-bottom sidescan sonar backscatter data that provides information on seafloor substrate (e.g., sediment/bare rock) and roughness. High-frequency sidescan sonar data with comparable resolution to AUV-derived bathymetry is typically collected by deep-towed instruments at altitudes <100 m. This approach has limited use in rough terrain as rapid depth changes in towed-vehicles can significantly degrade sidescan sonar data quality. This limitation certainly applies to arc volcanoes where regional slopes in excess of 25 degrees are present on volcano flanks and much greater local slopes due steep-walled calderas and resurgent domes are common. Here we report the first deployment of a dual-frequency sidescan sonar system (Edgetech 2200M 120/410 kHz) on the National Deep Submergence Facility AUV Sentry, which can easily operate in rough terrain. Sidescan sonar data was collected over three submarine volcanoes in the Kermadec Arc (Brothers, Healy, Rumble III) on a cruise sponsored by the Institute of Geological and Nuclear Science, New Zealand. Sentry operated at ~40 m altitude with track spacing of 50-100 m. Sonar imagery from the 410 kHz channel has a spatial resolution of ~20 cm/pixel. To our knowledge, these are the first near-bottom, high-frequency sidescan sonar data collected at submarine arc volcanoes. We use these data to evaluate the type (explosive, effusive), size, and relative age of the deposits that make up these volcanic edifices based on acoustic backscatter intensity, along with ground-truthing from deep-towed photographic surveys. Relative to existing multibeam and sidescan sonar backscatter data in similar settings, the Sentry-collected sidescan sonar can resolve much smaller scale features and thus generate a higher-fidelity record of the processes responsible for arc volcano construction and evolution than was previously possible.

Soule, S. A.; de Ronde, C. E.; Leybourne, M. I.; Caratori Tontini, F.; Kaiser, C. L.; Kurras, G. J.; Kinsey, J. C.; Yoerger, D. R.

2011-12-01

59

Submarine Pyroclastic Flow Deposits; July 2003 Dome Collapse Event of the Soufrière Hills Volcano, Montserrat, West Indies  

NASA Astrophysics Data System (ADS)

What happens when pyroclastic flows enter the ocean? To date, the subject of submarine pyroclastic flow behaviour has been controversial. Ambiguity arises from inconclusive evidence of a subaqueous depositional environment in ancient successions, to difficulty in sampling the in situ products of modern eruptions. A research voyage of the RRS James Clark Ross (9-18 May 2005) sampled 52 sites offshore from the volcanic island of Montserrat. The Soufrière Hills volcano, Montserrat, has been active since 1995 with eruptive behaviour dominated by andesite lava dome growth and collapse. Over 90% of the pyroclastic material produced has been deposited into the ocean. In July 2003 the Soufrière Hills volcano produced the largest historically documented dome collapse event. 210 x 106 m3 of pyroclastic material avalanched down the Tar River Valley, southeast Montserrat, to be deposited into the ocean. Bathymetric imaging and coring of offshore pyroclastic deposits, with a specific focus on the July 2003 units, reveals that the pyroclastic flows mix rapidly and violently with the water as they enter the ocean. Mixing takes place between the shore and 500 m depth where the deposition of basal coarse-grained parts of the flow initiates on slopes of 15° or less. The coarse components (pebbles to boulders) are deposited proximally from dense basal slurries to form steep sided, near linear ridges that amalgamate to form a kilometer-scale submarine fan. These proximal deposits contain <1% of ash-grade material. The finer components (dominantly ash-grade) are mixed into the overlying water column to form turbidity currents that flow distances >40 km from source. The total volume of pyroclastic material deposited within the submarine environment during this event exceeds 170 x 106 m3, with 65% deposited in proximal lobes and 35% deposited as distal turbidites. This broadly correlates with the block and ash components respectively, of the source subaerial pyroclastic flow. However, the efficient sorting and physical differentiation of the submarine flows, in comparison to the original mixture of their subaerial counterparts, suggests that the pyroclastic flows mix thoroughly with seawater and generate sediment gravity currents which are stratified in grain size and concentration.

Trofimovs, J.; Sparks, S.; Talling, P.

2006-12-01

60

The submarine volcano eruption at the island of El Hierro: physical-chemical perturbation and biological response  

PubMed Central

On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments.

Fraile-Nuez, E.; Gonzalez-Davila, M.; Santana-Casiano, J. M.; Aristegui, J.; Alonso-Gonzalez, I. J.; Hernandez-Leon, S.; Blanco, M. J.; Rodriguez-Santana, A.; Hernandez-Guerra, A.; Gelado-Caballero, M. D.; Eugenio, F.; Marcello, J.; de Armas, D.; Dominguez-Yanes, J. F.; Montero, M. F.; Laetsch, D. R.; Velez-Belchi, P.; Ramos, A.; Ariza, A. V.; Comas-Rodriguez, I.; Benitez-Barrios, V. M.

2012-01-01

61

Viral infections stimulate the metabolism and shape prokaryotic assemblages in submarine mud volcanoes  

PubMed Central

Mud volcanoes are geological structures in the oceans that have key roles in the functioning of the global ecosystem. Information on the dynamics of benthic viruses and their interactions with prokaryotes in mud volcano ecosystems is still completely lacking. We investigated the impact of viral infection on the mortality and assemblage structure of benthic prokaryotes of five mud volcanoes in the Mediterranean Sea. Mud volcano sediments promote high rates of viral production (1.65–7.89 × 109?viruses?g?1?d?1), viral-induced prokaryotic mortality (VIPM) (33% cells killed per day) and heterotrophic prokaryotic production (3.0–8.3??gC?g?1?d?1) when compared with sediments outside the mud volcano area. The viral shunt (that is, the microbial biomass converted into dissolved organic matter as a result of viral infection, and thus diverted away from higher trophic levels) provides 49?mgC?m?2?d?1, thus fuelling the metabolism of uninfected prokaryotes and contributing to the total C budget. Bacteria are the dominant components of prokaryotic assemblages in surface sediments of mud volcanoes, whereas archaea dominate the subsurface sediment layers. Multivariate multiple regression analyses show that prokaryotic assemblage composition is not only dependant on the geochemical features and processes of mud volcano ecosystems but also on synergistic interactions between bottom-up (that is, trophic resources) and top-down (that is, VIPM) controlling factors. Overall, these findings highlight the significant role of the viral shunt in sustaining the metabolism of prokaryotes and shaping their assemblage structure in mud volcano sediments, and they provide new clues for our understanding of the functioning of cold-seep ecosystems.

Corinaldesi, Cinzia; Dell'Anno, Antonio; Danovaro, Roberto

2012-01-01

62

Large Methane Plumes Formed by Hydrate Coated Gas Bubbles from a Deep-Sea Submarine Mud Volcano  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes (SMVs) are major methane sources in the marine environment. Worldwide 103-105 SMVs are believed to release in total about 27 Mt CH4 yr-1. Results of the last decade \\'{ } s research suggest, that most of this methane, primarily released diffusively from deep-sea SMVs is immediately oxidised and, thus, has only little climatic impact. Recent hydroacoustic, visual and geochemical observations performed at Haakon Mosby Mud Volcano (HMMV, 1250 meters water depth) reveal that a considerable amount of methane is released by discharge of bubbles and gas hydrate flakes. Gas bubbles withstand dissolution due to the formation of a gas hydrate skin and, thus, are able to ascend several hundred meters through the water column until leaving the temperature-pressure field of gas hydrate stability. Besides, microbial water column methane oxidation was found to be extremely slow, so that methane potentially escapes to the atmosphere, especially during deep winter mixing. We thus propose a much higher environmental relevance of SMVs than previously assumed.

Sauter, E. J.; Muyakshin, S. I.; Charlou, J.; Schlueter, M.; Boetius, A.; Damm, E.; Foucher, J.; Klages, M.

2004-12-01

63

Methane discharge into the Black Sea and the global ocean via fluid flow through submarine mud volcanoes  

Microsoft Academic Search

During the MARGASCH cruise M52\\/1 in 2001 with RV Meteor we sampled surface sediments from three stations in the crater of the Dvurechenskii mud volcano (DMV, located in the Sorokin Trough of the Black Sea) and one reference station situated 15 km to the northeast of the DMV. We analysed the pore water for sulphide, methane, alkalinity, sulphate, and chloride concentrations

Klaus Wallmann; Manuela Drews; Giovanni Aloisi; Gerhard Bohrmann

2006-01-01

64

North Kona slump: Submarine flank failure during the early(?) tholeiitic shield stage of Hualalai Volcano  

Microsoft Academic Search

The North Kona slump is an elliptical region, about 20 by 60 km (1000-km2 area), of multiple, geometrically intricate benches and scarps, mostly at water depths of 2000–4500 m, on the west flank of Hualalai Volcano. Two dives up steep scarps in the slump area were made in September 2001, using the ROV Kaiko of the Japan Marine Science and

P. W. Lipman; M. L. Coombs

2006-01-01

65

North Kona slump: Submarine flank failure during the early(?) tholeiitic shield stage of Hualalai Volcano  

Microsoft Academic Search

The North Kona slump is an elliptical region, about 20 by 60 km (1000-km2 area), of multiple, geometrically intricate benches and scarps, mostly at water depths of 2000 4500 m, on the west flank of Hualalai Volcano. Two dives up steep scarps in the slump area were made in September 2001, using the ROV Kaiko of the Japan Marine Science

P. W. Lipman; M. L. Coombs

2006-01-01

66

Morphometric analysis of the submarine arc volcano Monowai (Tofua-Kermadec Arc) to decipher tectono-magmatic interactions  

NASA Astrophysics Data System (ADS)

Morphometric analysis of multibeam bathymetry and backscatter data is applied to Monowai, a submarine volcano of the active Tofua-Kermadec Arc to map and document the structure and evolution of the volcanic centre. Low rates of erosion and sedimentation, and pervasive tectonic and magmatic processes, allow quantification through detailed structural analysis and measurement of deformation. The Slope, Aspect, Curvature, Rugosity, and Hydrology (flow) tools of ArcGIS provide a robust structural interpretation and the development of a model of Monowai evolution.A nested caldera structure with a volume of ~ 31 km3 and a stratovolcano of ~ 18 km3 dominate the magmatic constructs. The outer caldera is elongate along 125°, and the inner caldera along 135°. Numerous parasitic cones and fissure ridges are also observed, oriented at 039° and 041°, respectively. Northeast trending faults (with a regional average strike of 031°) are widespread within this part of the backarc, forming a nascent rift graben to the west of the Monowai caldera complex. The distribution of throw varies spatially, reaching a maximum total along-rift of 320 m and across rift of 120 m, with greater throw values measured in the west.Elongation directions of the two nested calderas are near-perpendicular to the trends of faults and fissure ridges. The inner caldera is more orthogonal to the magmatic constructs (fissure ridges and aligned vent cones) and the outer caldera is approximately orthogonal to the regional fault fabric, suggesting a strong interaction between magmatic and tectonic processes, and the directions of the horizontal principal stress. We present a detailed morphometric analysis of these relationships and the data are used to interpret the spatial and temporal evolution of the tectono-magmatic system at Monowai, and classify the type of rifting as transtensional. Similar analysis is possible elsewhere in the Kermadec backarc and within other regions of submarine volcanism.

Wormald, Sarah C.; Wright, Ian C.; Bull, Jonathan M.; Lamarche, Geoffroy; Sanderson, David J.

2012-09-01

67

Structural Morphology and Backarc Tectonic Imprint on Submarine Volcano Construction and Destruction, Central Kermadec arc (35° - 30°S), SW Pacific.  

NASA Astrophysics Data System (ADS)

Recent investigations aimed at illuminating the interplay between magmatic and tectonic processes have focused largely on continental rifts and oceanic ridges. In comparison, such work for active arc systems, where rifting is proximal, is less advanced, certainly for the case of submarine arcs. We present a detailed structural and volcanic morphological analysis of high-resolution multibeam data of central Kermadec arc volcanoes that clearly demonstrate the control of backarc tectonism on the evolution of the arc front. Of the 11 areas investigated, Macauley, Kuiwai and Brothers illustrate the range in edifice types (caldera, stratovolcano, satellite cones) and the influence of oblique backarc rifting on edifice construction and destruction. Fabric-parallel volcanic lineaments (striking 030°-060°) include volcanic ridges ± cones and aligned cones ± faults. These features predominate outside areas of significant edifice construction, though they may also occur on the flanks of major volcanoes (e.g. Kuiwai). We infer control by dike intrusion parallel to the structural fabric of the rift. In contrast, major edifices are not clearly related to fabric-parallel structures, though they are in places intersected by them. Lineaments associated with major edifices have variable orientations, oblique and orthogonal to the predominant rift fabric. Magmatic intrusion associated with major volcanic centres may perturb the regional stress field, providing a plausible explanation for this structural variability. We suggest that the presence of major arc edifices provides, through thermal weakening, efficient transfer zones for the accommodation of extensional strain within the mechanically segmented upper crust. However, the lack of discrete transfer faults together with the prevalence of dike-controlled features indicates that this is achieved through magmatic rather than purely mechanical processes. Volcanic ridges, aligned cones and lineaments parallel to the rift fabric bound regions of sector collapse (vertical drops > 1500m); edifice destruction is in part controlled by faulting and dike intrusion.

Campbell, M. E.; Rowland, J. V.; Wright, I. C.; Smith, I. E.

2005-12-01

68

Seafloor seismic monitoring of an active submarine volcano: Local seismicity at Vailulu'u Seamount, Samoa  

Microsoft Academic Search

We deployed five ocean bottom hydrophones (OBHs) for a 1-year seismic monitoring study of Vailulu'u Seamount, the youngest and easternmost volcano in the Samoan Archipelago. Four instruments were placed on the summit crater rim at 600–700 m water depth, and one was placed inside the crater at 1000 m water depth. An analysis of the first 45 days of records

J. G. Konter; H. Staudigel; S. R. Hart; P. M. Shearer

2004-01-01

69

Submarine hydrothermal activity and gold-rich mineralization at Brothers Volcano, Kermadec Arc, New Zealand  

Microsoft Academic Search

Brothers volcano, of the Kermadec intraoceanic arc, is host to a hydrothermal system unique among seafloor hydrothermal systems\\u000a known anywhere in the world. It has two distinct vent fields, known as the NW Caldera and Cone sites, whose geology, permeability,\\u000a vent fluid compositions, mineralogy, and ore-forming conditions are in stark contrast to each other. The NW Caldera site strikes\\u000a for

Cornel E. J. de Ronde; Gary J. Massoth; David A. Butterfield; Bruce W. Christenson; Junichiro Ishibashi; Robert G. Ditchburn; Mark D. Hannington; Robert L. Brathwaite; John E. Lupton; Vadim S. Kamenetsky; Ian J. Graham; Georg F. Zellmer; Robert P. Dziak; Robert W. Embley; Vesselin M. Dekov; Frank Munnik; Janine Lahr; Leigh J. Evans; Ken Takai

2011-01-01

70

Molecular comparison of bacterial communities within iron-containing flocculent mats associated with submarine volcanoes along the Kermadec Arc.  

PubMed

Iron oxide sheaths and filaments are commonly found in hydrothermal environments and have been shown to have a biogenic origin. These structures were seen in the flocculent material associated with two submarine volcanoes along the Kermadec Arc north of New Zealand. Molecular characterization of the bacterial communities associated with the flocculent samples indicated that no known Fe-oxidizing bacteria dominated the recovered clone libraries. However, clones related to the recently described Fe-oxidizing bacterium Mariprofundus ferrooxydans were obtained from both the iron-containing flocculent (Fe-floc) and sediment samples, and peaks corresponding to Mariprofundus ferrooxydans, as well as the related clones, were observed in several of our terminal restriction fragment length polymorphism profiles. A large group of epsilonproteobacterial sequences, for which there is no cultured representative, dominated clones from the Fe-floc libraries and were less prevalent in the sediment sample. Phylogenetic analyses indicated that several operational taxonomic units appeared to be site specific, and statistical analyses of the clone libraries found that all samples were significantly different from each other. Thus, the bacterial communities in the Fe-floc samples were not more closely related to each other than to the sediment communities. PMID:19114513

Hodges, Tyler W; Olson, Julie B

2008-12-29

71

Dive and Explore: An Interactive Exhibit That Simulates Making an ROV Dive to a Submarine Volcano, Hatfield Marine Science Visitor Center, Newport, Oregon  

NASA Astrophysics Data System (ADS)

We have created a new interactive exhibit in which the user can sit down and simulate that they are making a dive to the seafloor with the remotely operated vehicle (ROV) named ROPOS. The exhibit immerses the user in an interactive experience that is naturally fun but also educational. This new public display is located at the Hatfield Marine Science Visitor Center in Newport, Oregon. The exhibit is designed to look like the real ROPOS control console and includes three video monitors, a PC, a DVD player, an overhead speaker, graphic panels, buttons, lights, dials, and a seat in front of a joystick. The dives are based on real seafloor settings at Axial seamount, an active submarine volcano on the Juan de Fuca Ridge (NE Pacific) that is also the location of a seafloor observatory called NeMO. The user can choose between 1 of 3 different dives sites in the caldera of Axial Volcano. Once a dive is chosen, then the user watches ROPOS being deployed and then arrives into a 3-D computer-generated seafloor environment that is based on the real world but is easier to visualize and navigate. Once on the bottom, the user is placed within a 360 degree panorama and can look in all directions by manipulating the joystick. By clicking on markers embedded in the scene, the user can then either move to other panorama locations via movies that travel through the 3-D virtual environment, or they can play video clips from actual ROPOS dives specifically related to that scene. Audio accompanying the video clips informs the user where they are going or what they are looking at. After the user is finished exploring the dive site they end the dive by leaving the bottom and watching the ROV being recovered onto the ship at the surface. The user can then choose a different dive or make the same dive again. Within the three simulated dives there are a total of 6 arrival and departure movies, 7 seafloor panoramas, 12 travel movies, and 23 ROPOS video clips. The exhibit software was created with Macromedia Director using Apple Quicktime and Quicktime VR. The exhibit is based on the NeMO Explorer web site (http://www.pmel.noaa.gov/vents/nemo/explorer.html).

Weiland, C.; Chadwick, W. W.; Hanshumaker, W.; Osis, V.; Hamilton, C.

2002-12-01

72

Locating volcano-seismic signals in the presence of rough topography: wave simulations on Arenal volcano, Costa Rica  

NASA Astrophysics Data System (ADS)

Quantifying the scattering effects of pronounced volcano topography on the seismic wavefield is an important component in locating and interpreting volcano seismic sources. In this study, we perform seismic wave simulations to quantify the scattering generated by a 3-D digital elevation map and 1-D velocity model of Arenal volcano, Costa Rica. Full waveform synthetic seismograms were generated using a 3-D elastic lattice method including complex topography. Several different simulations were performed where the source location, source type and topographic models were varied. Synthetic seismograms were calculated for 35 seismic arrays each one comprising nine stations. At each array, the slowness vector of wave propagation is estimated from the time delays between the sensors obtained using the cross-spectral method. Results show that the backazimuth estimated for some arrays, in particular those close to the source, deviate from the true source position suggesting strong topographic effects in these regions. The maximum of the probability density function, obtained by crossing the backazimuths of the remaining arrays, coincides exactly with the true source location. We also compare our synthetic seismograms with array results from a physical field study. The true and calculated location misfit depends largely on the topography, but also on the number of antennas, the distance from the source and the spatial resolution of the antennas. The results show that this kind of study could be undertaken prior to the installation of seismic arrays to select the sites that minimize the topographic effects leading to improved source locations.

Métaxian, J. P.; O'Brien, G. S.; Bean, C. J.; Valette, B.; Mora, M.

2009-12-01

73

The volcanic debris avalanche on the SE submarine slope of Nisyros volcano, Greece: geophysical exploration and implications for subaerial eruption history  

NASA Astrophysics Data System (ADS)

A spectacular hummocky topography was discovered offshore of the south-eastern slope of the Nisyros island volcano in the eastern sector of the Aegean volcanic arc in 2000-2001, using multibeam bathymetric mapping and seismic profiling, and interpreted as part of a volcanic debris avalanche originating onland. During E/V Nautilus cruise NA011 in 2010, a detailed side-scan sonar and ROV exploration aimed at evaluating the surface morphology of this avalanche field. Combining the new data with selected older datasets reveals that the debris avalanche is characterized by numerous (at least 78) variously sized and shaped hummocks. Some of these are distinctly round, either scattered or aligned in groups, whereas others are elongated in the form of ridges. This is consistent with existing models accounting for variations in the longitudinal and lateral velocity ratio of landslides. Maximum dimensions reach 60 m in height above the sea bottom, 220 m in length and 230 m in width. The structures outline a large tongue-shaped, submarine hummock field of about 22.2 km2, approx. 4.8 km wide and 4.6 km long and with an estimated volume of 0.277 km3. Due to its characteristic shape, the collapsed volcanic flank is interpreted to represent a singular failing event, involving a rapid and virtually instantaneous downslope movement of the slide mass into the sea. Indeed, the H/L (height of 280 m vs. run-out of 7 km) ratio for the Nisyros slide is 0.04; plotted against volume, this falls within the theoretical bounds as well as measured values typical of submarine landslides. The timing of the event is probably related to the extrusion of Nikia lavas and their subsequent failure and formation of a main scarp observed at about 120 m depth on an 8-km-long seismic profile and a map of slope angle distribution, at the depth where the palaeo-coastline was located 40 ka ago. An inferred age of ca. 40 ka for the avalanche awaits confirmation based on dating of core material.

Livanos, Isidoros; Nomikou, Paraskevi; Papanikolaou, Dimitris; Rousakis, Grigoris

2013-08-01

74

Volcanoes.  

ERIC Educational Resources Information Center

One of a series of general interest publications on science topics, this booklet provides a non-technical introduction to the subject of volcanoes. Separate sections examine the nature and workings of volcanoes, types of volcanoes, volcanic geological structures such as plugs and maars, types of eruptions, volcanic-related activity such as geysers…

Tilling, Robert I.

75

Volcanoes.  

ERIC Educational Resources Information Center

|One of a series of general interest publications on science topics, this booklet provides a non-technical introduction to the subject of volcanoes. Separate sections examine the nature and workings of volcanoes, types of volcanoes, volcanic geological structures such as plugs and maars, types of eruptions, volcanic-related activity such as…

Tilling, Robert I.

76

Structural variability along the submarine south flank of Kilauea volcano, Hawai'i, from a multichannel seismic reflection survey  

NASA Astrophysics Data System (ADS)

Recent analysis of marine multichannel seismic reflection data collected across the south flank of Kilauea volcano, Hawaii has confirmed that the distal flank records significant accretion and deformation of volcaniclastic strata, building a broad and laterally extensive midslope bench [Morgan et al., 2000]. Further examination of adjacent reflection lines across the mobile flank of Kilauea demonstrates along-strike continuity in styles of deformation within the bench, as well as significant variability, which is commonly reflected in flank morphology. Correlation of reflections on 14 seismic lines allow us to identify at least 4 continuous thrust faults, several of which are traceable as far as ˜60 km from the southwestern margin of the mobile flank to the subaerial to submarine transition of the East Rift Zone in the northeast. A landward thrust fault rises from the top of the Cretaceous oceanic crust, and displaces the primary volcanic edifice seaward onto folded and faulted bedded strata. The more seaward faults originate at a horizon slightly above the oceanic crust that appears to define a regional decollement at the base of the flank. To the southeast, imbrication of seaward thrust sheets builds a broad bench which ponds sediments behind it in a deep midslope basin. A lateral fault locally disrupts these structures, marking a transition in structural style to the northeast, where thrust sheets are stacked vertically defining an antiformal stack. The basin is absent in this region, and the primary volcanic edifice is overthrust directly upon accreted and recently deposited sediments building a narrow bench. A seaward change in decollement level from the top of oceanic crust beneath the volcanic edifice to a horizon within bedded strata beneath the bench, and the lateral change in thrust sheet geometries, suggest variations in sliding resistance beneath the mobile south flank of Kilauea, contributing to the complicated morphology evident in the offshore region.

Hills, Denise J.; Morgan, Julia K.; Moore, Gregory F.; Leslie, Stephen C.

77

Noble gas systematics of the Hawaiian volcanoes based on the analysis of Loihi, Kilauea and Koolau submarine rocks  

NASA Astrophysics Data System (ADS)

Noble gas isotopes were analyzed for glass and olivine phenocrysts of Hawaiian submarine volcanic rocks collected at depths of 2300-5700 m using submersibles "Shinkai 6500" and "Kaiko". Both crushing and heating methods were used for extracting noble gases. Loihi samples had 3He/4He of 21-32 Ra, 20Ne/22Ne of 10-12 and 40Ar/36Ar of 300-2700, while Kilauea samples had 3He/4He of 13-15 Ra, 20Ne/22Ne of 10.6-11.1, and 40Ar/36Ar of 800-3600. For all samples analyzed, the 129Xe/130Xe cannot be distinguished from the atmospheric value within analytical uncertainty. Olivine separates from two Koolau basaltic rocks collected at depths of about 3600 m and 3100 m have 3He/4He of about 19 Ra, whereas other Koolau samples collected at depths of less than 3000 m have 3He/4He of 14-15 Ra like subaerial Koolau rocks. The samples collected from Loihi, in the pre-shield stage, contain both higher and more variable values of 3He/4He compared to the shield-building stage of other volcanoes in the Hawaiian chain. The post-shield and rejuvenated stages show the lowest 3He/4He, overlapping values obtained for MORB. We interpret this age trend to reflect an increasing degree of interaction between the rising plume magma and the uppermost part of asthenosphere. The extreme He isotope variation shown at Loihi may represent additional interaction of the plume magma with the old, altered oceanic crust. The variation of heavier noble gases may indicate incorporation of seawater into the magma before eruption.

Kaneoka, Ichiro; Hanyu, Takeshi; Yamamoto, Junji; Miura, Yayoi N.

78

Eruptive fracture location forecasts from high-frequency events on Piton de la Fournaise Volcano  

NASA Astrophysics Data System (ADS)

Piton de la Fournaise (La Réunion island) is a very active basaltic volcano, with five eruptions between Nov 2009 and Dec 2010. Pre-eruptive seismic crises usually last for a few hours and mainly consist of a volcano-tectonic swarm. During the quiescent period between the volcano-tectonic swarm and the eruptive tremor, we identify another swarm of events with a very high frequency content. These events are shallow and are located close to the future eruption site. They seem associated with the opening of the path for the magma propagating laterally at shallow depth. As these events start to occur while the magma is still in a vertical propagation phase, this seismicity seems to be related with the generic response of the volcano to the stress perturbation and not directly induced by the magma pressure. This new observation brings new insights to short-term forecasting of the eruption location.

De Barros, Louis; Bean, Christopher J.; Zecevic, Megan; Brenguier, Florent; Peltier, Aline

2013-09-01

79

Simulation of Submarine Hydrothermal Systems: IV. Fluid Flow in Active Arc-Related Volcanoes  

NASA Astrophysics Data System (ADS)

Fluid flow through submarine hydrothermal systems transports a major part of the Earth's heat to its surface and greatly impacts the chemistry of crust and overlying ocean. Seafloor high-temperature vent sites are manifestations of active ore-forming systems and can be regarded as modern analogues of massive sulfide deposits whose ancient equivalents have been exploited as world-class mines on land. Recent research cruises dedicated to seafloor hydrothermal activity along convergent plate boundaries, e.g. along the intra-oceanic Kermadec arc, have systematically surveyed and sampled numerous hydrothermal plumes. Follow-up submersible dives show venting that ranges from relatively high temperature (~300° C), metal-rich fluids to lower temperature, gas-rich and metal-poor fluids. Some of these vent sites show evidence for significant contributions from magmatic sources. The physics of such systems is complex because the seawater-derived hydrothermal fluid can mix with ambient seawater and phase-separate, either via boiling or condensation, into a low-salinity vapor and a high-salinity brine. In order to model the sub-seafloor hydrology with numerical transport simulation techniques, a newly developed pressure-enthalpy-salinity scheme has been used, which includes the full phase relations of the NaCl-H2O system up to 1000° C and accurately captures boiling, condensation, and salt precipitation. We have designed a new numerical model, based on observations in currently active arc-related systems, to assess the influence of first-order physical parameters (such as seafloor topography and the contribution of magmatic fluids) to fluid flow patterns, thermal structure, and phase-separation. Preliminary results of these simulations will be presented and compared with data recently obtained from simulations at mid-ocean ridge systems. In our ongoing project, we aim to predict the optimal conditions for which metal-rich magmatic vapor may cool and contract to an aqueous liquid, which in turn is likely to generate particularly Cu- and Au-rich mineralization on the seafloor.

Gruen, G.; Coumou, D.; Weis, P.; Driesner, T.; de Ronde, C.; Heinrich, C. A.

2008-12-01

80

Submarine hydrothermal activity and gold-rich mineralization at Brothers Volcano, Kermadec Arc, New Zealand  

NASA Astrophysics Data System (ADS)

Brothers volcano, of the Kermadec intraoceanic arc, is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world. It has two distinct vent fields, known as the NW Caldera and Cone sites, whose geology, permeability, vent fluid compositions, mineralogy, and ore-forming conditions are in stark contrast to each other. The NW Caldera site strikes for ˜600 m in a SW-NE direction with chimneys occurring over a ˜145-m depth interval, between ˜1,690 and 1,545 m. At least 100 dead and active sulfide chimney spires occur in this field and are typically 2-3 m in height, with some reaching 6-7 m. Their ages (at time of sampling) fall broadly into three groups: <4, 23, and 35 years old. The chimneys typically occur near the base of individual fault-controlled benches on the caldera wall, striking in lines orthogonal to the slopes. Rarer are massive sulfide crusts 2-3 m thick. Two main types of chimney predominate: Cu-rich (up to 28.5 wt.% Cu) and, more commonly, Zn-rich (up to 43.8 wt.% Zn). Geochemical results show that Mo, Bi, Co, Se, Sn, and Au (up to 91 ppm) are correlated with the Cu mineralization, whereas Cd, Hg, Sb, Ag, and As are associated with the dominant Zn-rich mineralization. The Cone site comprises the Upper Cone site atop the summit of the recent (main) dacite cone and the Lower Cone site that straddles the summit of an older, smaller, more degraded dacite cone on the NE flank of the main cone. Huge volumes of diffuse venting are seen at the Lower Cone site, in contrast to venting at both the Upper Cone and NW Caldera sites. Individual vents are marked by low-relief (?0.5 m) mounds comprising predominately native sulfur with bacterial mats. Vent fluids of the NW Caldera field are focused, hot (?300°C), acidic (pH ? 2.8), metal-rich, and gas-poor. Calculated end-member fluids from NW Caldera vents indicate that phase separation has occurred, with Cl values ranging from 93% to 137% of seawater values. By contrast, vent fluids at the Cone site are diffuse, noticeably cooler (?122°C), more acidic (pH 1.9), metal-poor, and gas-rich. Higher-than-seawater values of SO4 and Mg in the Cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from Fe-rich brines. Evidence for magmatic contributions to the hydrothermal system at Brothers includes: high concentrations of dissolved CO2 (e.g., 206 mM/kg at the Cone site); high CO2/3He; negative ?D and ?18OH2O for vent fluids; negative ?34S for sulfides (to -4.6‰), sulfur (to -10.2‰), and ?15N2 (to -3.5‰); vent fluid pH values to 1.9; and mineral assemblages common to high-sulfidation systems. Changing physicochemical conditions at the Brothers hydrothermal system, and especially the Cone site, occur over periods of months to hundreds of years, as shown by interlayered Cu + Au- and Zn-rich zones in chimneys, variable fluid and isotopic compositions, similar shifts in 3He/4He values for both Cone and NW Caldera sites, and overprinting of "magmatic" mineral assemblages by water/rock-dominated assemblages. Metals, especially Cu and possibly Au, may be entering the hydrothermal system via the dissolution of metal-rich glasses. They are then transported rapidly up into the system via magmatic volatiles utilizing vertical (˜2.5 km long), narrow (˜300-m diameter) "pipes," consistent with evidence of vent fluids forming at relatively shallow depths. The NW Caldera and Cone sites are considered to represent stages along a continuum between water/rock- and magmatic/hydrothermal-dominated end-members.

de Ronde, Cornel E. J.; Massoth, Gary J.; Butterfield, David A.; Christenson, Bruce W.; Ishibashi, Junichiro; Ditchburn, Robert G.; Hannington, Mark D.; Brathwaite, Robert L.; Lupton, John E.; Kamenetsky, Vadim S.; Graham, Ian J.; Zellmer, Georg F.; Dziak, Robert P.; Embley, Robert W.; Dekov, Vesselin M.; Munnik, Frank; Lahr, Janine; Evans, Leigh J.; Takai, Ken

2011-07-01

81

Volcanoes  

NSDL National Science Digital Library

Students investigate the processes that build volcanoes, the factors that influence different eruption types, and the threats volcanoes pose to their surrounding communities. They use what they have learned to identify physical features and eruption types of several actual volcanic episodes.

Foundation, Wgbh E.

2005-12-17

82

Eruption Rate Control On Morphology And Structure Of Submarine Monogenetic Volcanoes - Insights From Sumersible Dives Off Maui And Hawaii Islands  

Microsoft Academic Search

This paper presents the results of submersible dives off Hawaii Islands during four research cruises (R\\/V Kairei-ROV Kaiko 1998 and 2001, R\\/V Yokosuka-DSV Shinkai 1999 and 2002) by the Japan Marine Science and Technology Center. Morphologies and structures of submarine volcanic edifices were observed during dives on the Hana Ridge, submarine extension of Haleakala rift zone of East Maui and

S. Umino

2003-01-01

83

Location of eruption-related earthquake clusters at Augustine Volcano, Alaska, using station-pair differential times  

Microsoft Academic Search

Families of similar earthquakes at shallow depths occurring over multiple timescales have been identified prior to and during the 2005-2006 eruption of Augustine Volcano. The use of conventional and double-difference location methods failed to result in stable locations, due primarily to noisy site conditions as well as unfavourable station geometry for the Alaska Volcano Observatory stations. Previous work found that

Laura Sumiejski; Clifford Thurber; Heather R. Deshon

2009-01-01

84

How Slab Dip Affects the Location of Volcanoes  

NSDL National Science Digital Library

Students will plot the locations of earthquakes on the top of subducting slabs to determine slab dip and will then develop hypotheses regarding the relationship between slab dip, the depth of the slab, and volcanic activity on the surface.

Beutel, Erin

85

Structural Morphology and Backarc Tectonic Imprint on Submarine Volcano Construction and Destruction, Central Kermadec arc (35° - 30°S), SW Pacific  

Microsoft Academic Search

Recent investigations aimed at illuminating the interplay between magmatic and tectonic processes have focused largely on continental rifts and oceanic ridges. In comparison, such work for active arc systems, where rifting is proximal, is less advanced, certainly for the case of submarine arcs. We present a detailed structural and volcanic morphological analysis of high-resolution multibeam data of central Kermadec arc

M. E. Campbell; J. V. Rowland; I. C. Wright; I. E. Smith

2005-01-01

86

Submarine Pyroclastic Flow Deposits; July 2003 Dome Collapse Event of the Soufrière Hills Volcano, Montserrat, West Indies  

Microsoft Academic Search

What happens when pyroclastic flows enter the ocean? To date, the subject of submarine pyroclastic flow behaviour has been controversial. Ambiguity arises from inconclusive evidence of a subaqueous depositional environment in ancient successions, to difficulty in sampling the in situ products of modern eruptions. A research voyage of the RRS James Clark Ross (9-18 May 2005) sampled 52 sites offshore

J. Trofimovs; S. Sparks; P. Talling

2006-01-01

87

Determining the seismic source mechanism and location for an explosive eruption with limited observational data: Augustine Volcano, Alaska  

Microsoft Academic Search

Waveform inversions of the very-long-period components of the seismic wavefield produced by an explosive eruption that occurred on 11 January, 2006 at Augustine Volcano, Alaska constrain the seismic source location to near sea level beneath the summit of the volcano. The calculated moment tensors indicate the presence of a volumetric source mechanism. Systematic reconstruction of the source mechanism shows the

Phillip B. Dawson; Bernard A. Chouet; John Power

2011-01-01

88

Locating sources of volcanic explosions and study of the structure at Yasur volcano, Vanuatu  

NASA Astrophysics Data System (ADS)

Yasur volcano is a small scoria cone, located on Tanna Island, in southern Vanuatu. The cone is composed of 3 vents: two vents (A and B) in the southern crater and one vent (C) in the northern crater. The volcano is going through a permanent strombolian activity, characterized by explosions of gas bubbles and small ash plumes. The activity generates thousands of seismic signals per day, mostly explosion quakes and LP events. From January 2008 to February 2009, seismic activity has been recorded by 12 seismic antennas each composed of 7 short-period sensors: a 3 components seismometer surrounded by six vertical sensors. Distances between the central seismometer and the others sensors was 20m or 40m. In May 2008, 10 broadband stations have been installed to complete the seismic network. In this work, we present both source locations and a structural study of the volcano. To locate sources of seismic events, a seismic antenna technique is used. For each signal, the slowness vectors (which contain back-azimuth and apparent slowness) are estimated on a sliding window by inversion of the time delays calculated between the sensors using the cross-spectral method. Combining back-azimuth calculated for each antenna, sources are located by using a probabilistic approach. This method enabled to locate events belonging to several families of similar explosion quakes allowing to assign each family to the activity of one of the vents. The results show periods during which the activity shifts from northern to southern part of the crater. To improve our knowledge of the volcanic structure and therefore allow the use of other location techniques such as moment-tensor inversion, we applied remote sensing techniques and array methods in order to determine a 3D seismic velocity model of the volcano. First a Digital Elevation Model with a 5 to 10 meters resolution was built from a stereoscopic couple of satellite images (with 2.5 meters resolution) georeferenced with GPS points measured during the experiment. Then velocity models have been estimated below each antenna and for the whole array. Two methods have been used for this purpose: SPatial AutoCorrelation (SPAC) and high-resolution frequency wavenumber. These techniques enabled to determine the velocity structures below each antenna down 200m below the surface. To complete these models, the same methods are used on data recorded by the broadband stations, which allowed to estimate seismic velocities for greater depths. The different velocity models and the DEM are finally combined to recompose the P and S waves 3D velocity structures at the scale of the volcano.

Perrier, Laurence; Métaxian, Jean-Philippe; Battaglia, Jean; Garaebiti, Esline

2010-05-01

89

Volcano  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on volcanoes and the destruction that results from eruptions. Students are given a scenario of massive volcanic destruction and have to come up with a plan to help those affected by the events. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Weisel, Frank

90

Volcanic Risk Perception in Five Communities Located near the Chichón Volcano, Northern Chiapas, Mexico  

NASA Astrophysics Data System (ADS)

The Chichón volcano (17° 19’ N and 93° 15’ W) is located in the state of Chiapas, Mexico. This volcano is classified by UNESCO as one of the ten most dangerous volcanos in the world. The eruptions of March and April in 1982 affected at least 51 communities located in the surroundings of the volcano and caused the death of about 2000 people. In this work we evaluate the risk perception in five communities highly populated: Juárez, Ostuacán, Pichucalco, Reforma and Sunuapa. We selected these communities because they have a high possibility to be affected by a volcanic eruption in the future. Our survey was carried out during February and March 2006. A total of 222 families were interviewed using a questionnaire to measure risk perception. These questionnaires retrieved general information as how long people had been living there and their reasons to do so; their experiences during the 1982 events, their opinion about the authorities participation and their perception of volcanic risk; the plans of the community for disaster prevention and mitigation. Some of the most important results are: (1). People perceive a very low volcanic risk and the 70% of interviewees believe that a new eruption in the future is almost improbable because it happened in 1982. This result is particularly interesting because, according to the state government, more than 100,000 inhabitants will be directly affected in case of a new similar eruption; (2). About 95% of the population do not know the current activity of the volcano and consider that the authorities do not inform properly to their communities; (3). The response of the authorities during the events of 1982 was ranked as deficient mainly because they were unable provide shelters, storage facilities, food as well as medicine and health care access; (4). Approximately 60% of the community will accept to be re-located again in case of a new eruption; (5). About 70% of the population will not accept to be re-located because they do not know any plan, strategy, emergency schemes or shelters locations no even evacuation routes. In conclusion, during the 1982 eruption the risk perception of the population played an important role in the social impact on the region. We believe that if the population had had a proper perception of their volcanic risk, the number of casualties would have been lower. Thus, the present low volcanic risk perception of the five studied communities can be considered as an important element of vulnerability. Frances Rodríguez-VanGort1 and David A. Novelo-Casanova2 (1) Posgrado Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México Distrito Federal (2) Departamento de Sismología Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México Distrito Federal

Rodriguez, F.; Novelo-Casanova, D. A.

2010-12-01

91

Active Submarine Volcanoes and Electro-Optical Sensor Networks: The Potential of Capturing and Quantifying an Entire Eruptive Sequence at Axial Seamount, Juan de Fuca Ridge  

NASA Astrophysics Data System (ADS)

The NE Pacific Regional Scale Nodes (RSN) component of the NSF Ocean Observatories Initiative is designed to provide unprecedented electrical power and bandwidth to the base and summit of Axial Seamount. The scientific community is engaged in identifying a host of existing and innovative observation and measurement techniques that utilize the high-power and bandwidth infrastructure and its real-time transmission capabilities. The cable, mooring, and sensor arrays will enable the first quantitative documentation of myriad processes leading up to, during, and following a submarine volcanic event. Currently planned RSN instrument arrays will provide important and concurrent spatial and temporal constraints on earthquake activity, melt migration, hydrothermal venting behavior and chemistry, ambient currents, microbial community structure, high-definition (HD) still images and HD video streaming from the vents, and water-column chemistry in the overlying ocean. Anticipated, but not yet funded, additions will include AUVs and gliders that continually document the spatial-temporal variations in the water column above the volcano and the distal zones. When an eruption appears imminent the frequency of sampling will be increased remotely, and the potential of repurposing the tracking capabilities of the mobile sensing platforms will be adapted to the spatial indicators of likely eruption activity. As the eruption begins mobile platforms will fully define the geometry, temperature, and chemical-microbial character of the volcanic plume as it rises into the thoroughly documented control volume above the volcano. Via the Internet the scientific community will be able to witness and direct adaptive sampling in response to changing conditions of plume formation. A major goal will be to document the eruptive volume and link the eruption duration to the volume of erupted magma. For the first time, it will be possible to begin to quantify the time-integrated output of an underwater volcanic eruption linked to the heat, chemical, and biological fluxes. In the late stages of the event, the dissipation of the "event plume" into the surrounding water column and the plume's migration patterns in the ambient regional flow will be tracked using specifically designed mobile sensor-platforms. The presence of these assets opens the potential for more immediate, coordinated, and thorough event responses than the community has previously been able to mount. Given the relative abundance of information on many variables in a verifiable and archived spatial and temporal context, and the rapidly evolving ability to conduct real-time genomic analyses, our community may be able to secure entirely novel organisms that are released into the overlying ocean only under well-characterized eruptive conditions.

Delaney, J. R.; Kelley, D. S.; Proskurowski, G.; Fundis, A. T.; Kawka, O.

2011-12-01

92

Kinematic variables and water transport control the formation and location of arc volcanoes.  

PubMed

The processes that give rise to arc magmas at convergent plate margins have long been a subject of scientific research and debate. A consensus has developed that the mantle wedge overlying the subducting slab and fluids and/or melts from the subducting slab itself are involved in the melting process. However, the role of kinematic variables such as slab dip and convergence rate in the formation of arc magmas is still unclear. The depth to the top of the subducting slab beneath volcanic arcs, usually approximately 110 +/- 20 km, was previously thought to be constant among arcs. Recent studies revealed that the depth of intermediate-depth earthquakes underneath volcanic arcs, presumably marking the slab-wedge interface, varies systematically between approximately 60 and 173 km and correlates with slab dip and convergence rate. Water-rich magmas (over 4-6 wt% H(2)O) are found in subduction zones with very different subduction parameters, including those with a shallow-dipping slab (north Japan), or steeply dipping slab (Marianas). Here we propose a simple model to address how kinematic parameters of plate subduction relate to the location of mantle melting at subduction zones. We demonstrate that the location of arc volcanoes is controlled by a combination of conditions: melting in the wedge is induced at the overlap of regions in the wedge that are hotter than the melting curve (solidus) of vapour-saturated peridotite and regions where hydrous minerals both in the wedge and in the subducting slab break down. These two limits for melt generation, when combined with the kinematic parameters of slab dip and convergence rate, provide independent constraints on the thermal structure of the wedge and accurately predict the location of mantle wedge melting and the position of arc volcanoes. PMID:19494913

Grove, T L; Till, C B; Lev, E; Chatterjee, N; Médard, E

2009-06-01

93

Bayesian statistics applied to the location of the source of explosions at Stromboli Volcano, Italy  

USGS Publications Warehouse

We present a method for determining the location and spatial extent of the source of explosions at Stromboli Volcano, Italy, based on a Bayesian inversion of the slowness vector derived from frequency-slowness analyses of array data. The method searches for source locations that minimize the error between the expected and observed slowness vectors. For a given set of model parameters, the conditional probability density function of slowness vectors is approximated by a Gaussian distribution of expected errors. The method is tested with synthetics using a five-layer velocity model derived for the north flank of Stromboli and a smoothed velocity model derived from a power-law approximation of the layered structure. Application to data from Stromboli allows for a detailed examination of uncertainties in source location due to experimental errors and incomplete knowledge of the Earth model. Although the solutions are not constrained in the radial direction, excellent resolution is achieved in both transverse and depth directions. Under the assumption that the horizontal extent of the source does not exceed the crater dimension, the 90% confidence region in the estimate of the explosive source location corresponds to a small volume extending from a depth of about 100 m to a maximum depth of about 300 m beneath the active vents, with a maximum likelihood source region located in the 120- to 180-m-depth interval.

Saccorotti, G.; Chouet, B.; Martini, M.; Scarpa, R.

1998-01-01

94

Locating pyroclastic flows on Soufriere Hills Volcano, Montserrat, West Indies, using amplitude signals from high dynamic range instruments  

Microsoft Academic Search

Pyroclastic flows are located using amplitude signals from a seven-station high dynamic range seismograph array located 1.9–6.1 km from Soufriere Hills Volcano in Montserrat, West Indies. Locations are determined by measuring the seismograph signal amplitude for an event recorded at several stations in a moving time window analysis. For a given window, the measured amplitudes are corrected to a trial

A. D Jolly; G. Thompson; G. E Norton

2002-01-01

95

Submarine Barrier Detection Model.  

National Technical Information Service (NTIS)

The paper presents a model for calculating the maximum probability of detection of a submarine using a detection barrier of fixed length. It is assumed in this calculation that location and heading of the submarine are known to some degree of certainty. T...

A. W. Starr W. T. McCormick

1971-01-01

96

Researchers Discover Underwater Volcano-within-a-Volcano (PR 05-089)  

NSF Publications Database

... a submarine volcano growing within the summit crater of another larger underwater volcano called ... they profiled the seafloor of the Vailulu'u crater using multi-beam mapping. Existing maps of the ...

97

Location of long-period events below Kilauea Volcano using seismic amplitudes and accurate relative relocation  

USGS Publications Warehouse

We present methods for improving the location of long-period (LP) events, deep and shallow, recorded below Kilauea Volcano by the permanent seismic network. LP events might be of particular interest to understanding eruptive processes as their source mechanism is assumed to directly involve fluid transport. However, it is usually difficult or impossible to locate their source using traditional arrival time methods because of emergent wave arrivals. At Kilauea, similar LP waveform signatures suggest the existence of LP multiplets. The waveform similarity suggests spatially close sources, while catalog solutions using arrival time estimates are widely scattered beneath Kilauea's summit caldera. In order to improve estimates of absolute LP location, we use the distribution of seismic amplitudes corrected for station site effects. The decay of the amplitude as a function of hypocentral distance is used for inferring LP location. In a second stage, we use the similarity of the events to calculate their relative positions. The analysis of the entire LP seismicity recorded between January 1997 and December 1999 suggests that a very large part of the LP event population, both deep and shallow, is generated by a small number of compact sources. Deep events are systematically composed of a weak high-frequency onset followed by a low-frequency wave train. Aligning the low-frequency wave trains does not lead to aligning the onsets indicating the two parts of the signal are dissociated. This observation favors an interpretation in terms of triggering and resonance of a magmatic conduit. Instead of defining fault planes, the precise relocation of similar LP events, based on the alignment of the high-energy low-frequency wave trains, defines limited size volumes. Copyright 2003 by the American Geophysical Union.

Battaglia, J.; Got, J. -L.; Okubo, P.

2003-01-01

98

Source amplitudes of volcano-seismic signals determined by the amplitude source location method as a quantitative measure of event size  

NASA Astrophysics Data System (ADS)

The amplitude source location (ASL) method, which uses high-frequency amplitudes under the assumption of isotropic S-wave radiation, has been shown to be useful for locating the sources of various types of volcano-seismic signals. We tested the ASL method by using synthetic seismograms and examined the source amplitudes determined by this method for various types of volcano-seismic signals observed at different volcanoes. Our synthetic tests indicated that, although ASL results are not strongly influenced by velocity structure and noise, they do depend on site amplification factors at individual stations. We first applied the ASL method to volcano-tectonic (VT) earthquakes at Taal volcano, Philippines. Our ASL results for the largest VT earthquake showed that a frequency range of 7-12 Hz and a Q value of 50 were appropriate for the source location determination. Using these values, we systematically estimated source locations and amplitudes of VT earthquakes at Taal. We next applied the ASL method to long-period events at Cotopaxi volcano and to explosions at Tungurahua volcano in Ecuador. We proposed a practical approach to minimize the effects of site amplifications among different volcano seismic networks, and compared the source amplitudes of these various volcano-seismic events with their seismic magnitudes. We found a proportional relation between seismic magnitude and the logarithm of the source amplitude. The ASL method can be used to determine source locations of small events for which onset measurements are difficult, and thus can estimate the sizes of events over a wider range of sizes compared with conventional hypocenter determination approaches. Previously, there has been no parameter widely used to quantify the sources of volcano-seismic signals. This study showed that the source amplitude determined by the ASL method may be a useful quantitative measure of volcano-seismic event size.

Kumagai, Hiroyuki; Lacson, Rudy; Maeda, Yuta; Figueroa, Melquiades S.; Yamashina, Tadashi; Ruiz, Mario; Palacios, Pablo; Ortiz, Hugo; Yepes, Hugo

2013-05-01

99

Submarine sliver in North Kona: A window into the early magmatic and growth history of Hualalai Volcano, Hawaii  

USGS Publications Warehouse

Two manned submersible dives examined the Hualalai Northwest rift zone and an elongate ridge cresting at 3900 mbsl during a 2002 JAMSTEC cruise. The rift zone flank at dive site S690 (water depth 3412-2104 m) is draped by elongated and truncated pillow lavas. These olivine-rich tholeiitic lavas are compositionally indistinguishable from those examined further south along the bench, except that they span a wider range in dissolved sulfur content (200-1400 ppm). The elongate ridge investigated in dive S692, located at the base of the bench, is a package of distinct lithologic units containing volcaniclastic materials, glassy pillow breccias, and lava blocks; these units contain a range of compositions including tholeiitic basalt, transitional basalt, and hawaiite. The textures, compositions, and stratigraphic relationships of materials within the elongate ridge require that a variety of transport mechanisms juxtaposed materials from multiple eruptions into individual beds, compacted them into a coherent package of units, and brought the package to its present depth 10 km from the edge of the North Kona slump bench. Sulfur-rich hawaiite glasses at the base of the elongate ridge may represent the first extant representatives of juvenile alkalic volcanism at Hualalai. They are geochemically distinct from shield tholeiite and post-shield alkalic magmas, but may be related to transitional basalt by high-pressure crystal fractionation of clinopyroxene. Tholeiitic glasses that compose the majority of the exposed outcrop are similar to Mauna Kea tholeiites and other Hualalai tholeiites, but they differ from younger basalts in having greater incompatible element enrichments and higher CaO for a given MgO. These differences could arise from small extents of partial melting during the transition from alkalic to shield stage magmatism. Low sulfur contents of most of the volcaniclastic tholeiites point to early emergence of Hualalai above sea level relative to the development of the midslope slump bench. ?? 2005 Elsevier B.V. All rights reserved.

Hammer, J. E.; Coombs, M. L.; Shamberger, P. J.; Kimura, J. -I.

2006-01-01

100

High-precision earthquake location, velocity determination, and event family identification at Augustine Volcano, Alaska, from 1993 through the 2005-2006 eruption  

Microsoft Academic Search

Volcano seismic networks typically have few stations and marginal coverage, providing challenges for earthquake location in a complex, three-dimensional setting. To improve location precision at Augustine Volcano, Alaska, we compute a three-dimensional P-wave velocity model using double-difference (DD) tomography combined with waveform cross-correlation (WCC) techniques. We also examine temporal changes in earthquake locations and waveform characteristics associated with the 2005-2006

H. R. Deshon; S. G. Prejean; C. H. Thurber; J. A. Power

2006-01-01

101

U-series disequilibria in Kick’em Jenny submarine volcano lavas: A new view of time-scales of magmatism in convergent margins  

NASA Astrophysics Data System (ADS)

We present data for U and its decay series nuclides 230Th, 226Ra, 231Pa, and 210Po for 14 lavas from Kick'em Jenny (KEJ) submarine volcano to constrain the time-scales and processes of magmatism in the Southern Lesser Antilles, the arc having the globally lowest plate convergence rate. Although these samples are thought to have been erupted in the last century, most have ( 226Ra)/( 210Po) within ±15% of unity. Ten out of 14 samples have significant 226Ra excesses over 230Th, with ( 226Ra)/( 230Th) up to 2.97, while four samples are in 226Ra- 230Th equilibrium within error. All KEJ samples have high ( 231Pa)/( 235U), ranging from 1.56 to 2.64 and high 238U excesses (up to 43%), providing a global end-member of high 238U and high 231Pa excesses. Negative correlations between Sr, sensitive to plagioclase fractionation, and Ho/Sm, sensitive to amphibole fractionation, or K/Rb, sensitive to open system behavior, indicate that differentiation at KEJ lavas was dominated by amphibole fractionation and open-system assimilation. While ( 231Pa)/( 235U) does not correlate with differentiation indices such as Ho/Sm, ( 230Th)/( 238U) shows a slight negative correlation, likely due to assimilation of materials with slightly higher ( 230Th)/( 238U). Samples with 226Ra excess have higher Sr/Th and Ba/Th than those in 226Ra- 230Th equilibrium, forming rough positive correlations of ( 226Ra)/( 230Th) with Sr/Th and Ba/Th similar to those observed in many arc settings. We interpret these correlations to reflect a time-dependent magma differentiation process at shallow crustal levels and not the process of recent fluid addition at the slab-wedge interface. The high 231Pa excesses require an in-growth melting process operating at low melting rates and small residual porosity; such a model will also produce significant 238U- 230Th and 226Ra- 230Th disequilibrium in erupted lavas, meaning that signatures of recent fluid addition from the slab are unlikely to be preserved in KEJ lavas. We instead propose that most of the 238U- 230Th, 226Ra- 230Th, and 235U- 231Pa disequilibria in erupted KEJ lavas reflect the in-growth melting process in the mantle wedge (reflecting variations in U/Th, daughter-parent ratios, fO 2, and thermal structure), followed by modification by magma differentiation at crustal depths. Such a conclusion reconciles the different temporal implications from different U-series parent-daughter pairs and relaxes the time constraint on mass transfer from slab to eruption occurring in less than a few thousand years imposed by models whereby 226Ra excess is derived from the slab.

Huang, Fang; Lundstrom, Craig C.; Sigurdsson, Haraldur; Zhang, Zhaofeng

2011-01-01

102

Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: Earthquake locations and source parameters  

Microsoft Academic Search

An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of

Natalia A. Ruppert; Stephanie Prejean; Roger A. Hansen

2011-01-01

103

Application of near real-time radial semblance to locate the shallow magmatic conduit at Kilauea Volcano, Hawaii  

USGS Publications Warehouse

Radial Semblance is applied to broadband seismic network data to provide source locations of Very-Long-Period (VLP) seismic energy in near real time. With an efficient algorithm and adequate network coverage, accurate source locations of VLP energy are derived to quickly locate the shallow magmatic conduit system at Kilauea Volcano, Hawaii. During a restart in magma flow following a brief pause in the current eruption, the shallow magmatic conduit is pressurized, resulting in elastic radiation from various parts of the conduit system. A steeply dipping distribution of VLP hypocenters outlines a region extending from sea level to about 550 m elevation below and just east of the Halemaumau Pit Crater. The distinct hypocenters suggest the shallow plumbing system beneath Halemaumau consists of a complex plexus of sills and dikes. An unconstrained location for a section of the conduit is also observed beneath the region between Kilauea Caldera and Kilauea Iki Crater.

Dawson, P.; Whilldin, D.; Chouet, B.

2004-01-01

104

High-resolution locations of triggered earthquakes and tomographic imaging of Kilauea Volcano's south flank  

NASA Astrophysics Data System (ADS)

The spatiotemporal patterns of seismicity beneath Kilauea's south flank give insight to the structure and geometry of the decollement on which large, tsunamigenic earthquakes have occurred, and its relation to slow slip events (SSEs), which have been observed every 1 to 2 years since 1997. In order to record earthquakes triggered by a SSE that was predicted to occur in March 2007, a temporary network of 20 seismometers was deployed on Kilauea's south flank, termed the SEQ network. While the SSE did not occur until 17 June 2007, theSEQ network recorded over 3000 earthquakes, including those triggered by the SSE. We relocate hypocenters of volcano-tectonic earthquakes and invert for P and S wave velocity structure using waveform cross-correlation and double-difference tomography using data from the SEQ network and the permanent Hawaii Volcano Observatory network (HVO) data, with additional data from other previous temporary arrays. The best-constrained hypocenters, recorded by both the SEQ and HVO networks, indicate the decollement as a subhorizontal layer of seismicity at 8 km depth less than 1 km thick in most areas, with the western portion of the decollement dipping to the southeast. The seismicity triggered by the June 2007 SSE includes over 400 earthquakes overlapping with the southern edge of the decollement seismicity. A shallower swarm of earthquakes also occurred between 2 and 7 km depth in April 2007 near Apua Point, and may have been indirectly triggered by the Mw 8.1 Solomon Islands earthquake at ˜6000 km distance, which occurred 48 h prior to the beginning of the swarm.

Syracuse, Ellen M.; Thurber, Clifford H.; Wolfe, Cecily J.; Okubo, Paul G.; Foster, James H.; Brooks, Benjamin A.

2010-10-01

105

Cutting Costs by Locating High Production Wells: A Test of the Volcano seismic Approach to Finding ''Blind'' Resources  

SciTech Connect

In the summer of 2000, Duke University and the Kenyan power generation company, KenGen, conducted a microearthquake monitoring experiment at Longonot volcano in Kenya. Longonot is one of several major late Quaternary trachyte volcanoes in the Kenya Rift. They study was aimed at developing seismic methods for locating buried hydrothermal areas in the Rift on the basis of their microearthquake activity and wave propagation effects. A comparison of microearthquake records from 4.5 Hz, 2 Hz, and broadband seismometers revealed strong high-frequency site and wave-propagation effects. The lower frequency seismometers were needed to detect and record individual phases. Two-dozen 3-component 2- Hz L22 seismographs and PASSCAL loggers were then distributed around Longonot. Recordings from this network located one seismically active area on Longonot's southwest flank. The events from this area were emergent, shallow (<3 km), small (M<1), and spatially restricted. Evidently, the hydrothermal system in this area is not currently very extensive or active. To establish the nature of the site effects, the data were analyzed using three spectral techniques that reduce source effects. The data were also compared to a simple forward model. The results show that, in certain frequency ranges, the technique of dividing the horizontal motion by the vertical motion (H/V) to remove the source fails because of non-uniform vertical amplification. Outside these frequencies, the three methods resolve the same, dominant, harmonic frequencies at a given site. In a few cases, the spectra can be fit with forward models containing low velocity surface layers. The analysis suggests that the emergent, low frequency character of the microearthquake signals is due to attenuation and scattering in the near surface ash deposits.

Eylon Shalev; Peter E. Malin; Wendy McCausland

2002-06-06

106

Volcano Live  

NSDL National Science Digital Library

Volcano Live contains maps of volcanoes from around the world, a kids' page that provides volcano education links for teachers and students, a volcano glossary, volcano news, links to live video cams of volcanoes, geography and volcano information of countries around the world, and video clips of active volcanoes. There is also information for travelling to volcanoes, a volcano photo section, a section on the destruction of Pompeii, a volcanology section, and volcano safety rules.

Seach, John

107

High-precision earthquake location, velocity determination, and event family identification at Augustine Volcano, Alaska, from 1993 through the 2005-2006 eruption  

NASA Astrophysics Data System (ADS)

Volcano seismic networks typically have few stations and marginal coverage, providing challenges for earthquake location in a complex, three-dimensional setting. To improve location precision at Augustine Volcano, Alaska, we compute a three-dimensional P-wave velocity model using double-difference (DD) tomography combined with waveform cross-correlation (WCC) techniques. We also examine temporal changes in earthquake locations and waveform characteristics associated with the 2005-2006 eruption and pre-eruptive seismicity. The Alaska Volcano Observatory (AVO) has monitored Augustine using up to 9 stations since 1993, and the AVO hypocenter and waveform catalog from 1993-2006 serves as the initial dataset. Many of the catalog hypocenters locate above the summit, reflecting the limitations of applying standard location techniques in rugged and sparsely instrumented volcanic settings. WCC using bispectrum verification improves the pick accuracy of the catalog data and is used to identify similar earthquakes. Waveform similarity at Augustine is low compared to other Alaskan volcanoes such as Redoubt, and most event families contain less than 100 events. Earthquakes recorded during a period of increasing pre-eruptive seismicity in December 2005 form clusters of similar earthquakes over periods of days. Events prior to the 2005-2006 eruption can exhibit a high degree of similarity over multiple years. The DD tomography method provides significantly improved absolute and relative earthquake locations and source region velocity information. We use differential travel times from catalog and cross-correlation data to simultaneously invert for hypocenter location and P-wave velocity structure. Previous studies have shown a high degree of north-south trending variation in compressional wave velocity at Augustine. This is reflected in severe station correction-velocity-depth tradeoffs when performing standard 1D inversions to solve for a starting model. Using our combined DD tomography and WCC approach, we better constrain the 3D nature of velocity heterogeneity beneath the volcano.

Deshon, H. R.; Prejean, S. G.; Thurber, C. H.; Power, J. A.

2006-12-01

108

High-precision earthquake location and three-dimensional P wave velocity determination at Redoubt Volcano, Alaska  

Microsoft Academic Search

Redoubt Volcano, Alaska poses significant volcanic hazard to the Cook Inlet region and overlying flight paths. During and following the most recent eruption in 1989–1990 the Alaska Volcano Observatory deployed up to 10 seismometers to improve real-time monitoring capabilities at Redoubt and continues to produce an annual earthquake catalog with associated arrival times for this volcano. We compute a three-dimensional

Heather R. DeShon; Clifford H. Thurber; Charlotte Rowe

2007-01-01

109

Characterization of fracture systems using precise array locations of earthquake multiplets: An example at Deception Island volcano, Antarctica  

NASA Astrophysics Data System (ADS)

Volcano-tectonic earthquakes are common seismic events in active volcanic areas. The stress produced by volcanic processes is released through fracturing of the shallow crust. Very often, these earthquakes occur in multiplets with similar waveforms, a fact which indicates common source characteristics. In this work, we introduce a method that uses array techniques to calculate precise relative locations of earthquake multiplets. We use the relative slowness estimate method to determine accurately the apparent slownesses and propagation azimuths of the earthquakes relative to a selected master event. We also obtain precise estimates of the S-P delays. This information is used to calculate precise relative locations by ray tracing in an Earth model. We applied this method to determine the characteristics of the fractures activated during the 1999 seismic series at the Deception Island volcano, Antarctica. We selected a set of 17 earthquake multiplets, initially located in a small (4 × 4 km) region a few km NE of the array site. We estimated precise locations for 14 of the clusters. In most cases, hypocenters were distributed in well-defined planar geometries. We found the best fitting planes, which we interpreted as fractures in the medium. For two clusters, the method spatially separated the earthquakes into two subgroups. Thus, we obtained two planes for each of these clusters, resulting in a total of 16 fracture planes. This is the first time that the orientations of fracture planes related to a seismic series have been obtained using a seismic array. We performed several tests to check various aspects in relation to the stability of the method and concluded that the results were robust. The dip angles indicate that the planes are mostly subvertical, while the strike angles clearly show a NW-SE trend for most of the planes and a few planes with NE-SW trends. The geometry and position of these planes suggest that the 1999 seismic series was influenced by regional tectonics, although the origin of the destabilization of the system may be related to the reactivation of a shallow magma chamber.

Carmona, E.; Almendros, J.; PeñA, J. A.; IbáñEz, J. M.

2010-06-01

110

White submarine  

NASA Astrophysics Data System (ADS)

While not everyone gets to live in a yellow submarine, the scientific community may get to have a decommissioned U.S. Navy nuclear submarine dedicated to it. The Sturgeon class of submarines, which scientists say are the ideal choice for the project, will be coming up for decommissioning in this next decade. So the time is ripe, scientists say. Two weeks ago, oceanographers, submarine specialists, marine biologists, and geophysicists, among others met at AGU headquarters in Washington to discuss how to get the project in the water. If all goes well, the project would be the "biggest thing that ever happened in ocean and Earth science," according to Lloyd Keigwin of the Woods Hole Oceanographic Institution, who convened the meeting. For example, the submarine could make many types of "compelling" research possible that can not be done now by other means, such as studies in the Arctic that may have significant bearing on global change research, Keigwin says. However, the imposing hurdles that the project must overcome are as big as the opportunities it offers. Foremost, there is a question as to who will pick up the tab for such an endeavor.

111

Where are the Volcanoes?  

NSDL National Science Digital Library

This formative assessment item discusses common misconceptions about volcano location around the world. Resources include background and content information as well as alignment to the National Science Education Standards. The probe could easily be modified to be used with a study of earthquakes instead of volcanoes. Teachers can access other resources including facts about volcanoes and lesson ideas.

Fries-Gaither, Jessica

112

Volcanoes: Annenberg Media Project  

NSDL National Science Digital Library

Volcanoes is an exhibit from the Annenberg Media Project that provides a wealth of information about volcanoes and includes sections such as Melting Rocks, the Dynamic Earth, and Forecasting. Interactive exercises enable the user to learn how rock turns into magma, how to locate volcanoes, and how to decide if building a project near a volcano is safe. Quicktime videos are used for each of the six categories to illustrate the points outlined in the text.

1997-01-01

113

Distribution of gassy sediments and mud volcanoes offshore southwestern Taiwan  

NASA Astrophysics Data System (ADS)

This study presents the results of recent intense submarine geophysical surveys conducted offshore southwestern Taiwan. Mud volcanoes and gassy sediments have been identified from chirp sonar and seismic reflection profile data. The distribution of gassy sediments and mud volcanoes have been compiled which shows that they extend from the accretionary wedge province to the passive China continental margin province. Submarine mud volcanoes could be grouped into four main clusters in the accretionary wedge province: offshore Kaohsiung, Kaoping Submarine Canyon, Fenliao Submarine Canyon and Yung-An Lineament. Each cluster is composed of several to more than 10 submarine mud volcanoes. Their origin could be related to the gas hydrate dissociation with the rising of high-pressure fluid along faults or the mud diapir pierced the sea floor.

Chiu, J.; Tseng, W.; Liu, C.

2006-12-01

114

Pb, Hf, Nd, and Sr Isotopic Variations of Hualalai Shield Stage Tholeiites from the Submarine North Kona Region  

Microsoft Academic Search

We present the isotope and trace element compositions of tholeiitic lavas collected from deep submarine portions of North Kona region, the west flank of Hualalai volcano. The samples were collected from the lower section of the North Kona bench (dives K218 and K219), a submarine section at Hualalai volcano's northwest rift zone (dive S690), and an elongate ridge below the

S. Yamasaki; T. Kani; B. B. Hanan; T. Tagami

2007-01-01

115

Moment tensor inversion for the source location and mechanism of long period (LP) seismic events from 2009 at Turrialba volcano, Costa Rica  

NASA Astrophysics Data System (ADS)

Long-period (LP) seismic events were recorded during the temporary installation of a broadband seismic network of 13 stations from March to September 2009 on Turrialba volcano, Costa Rica. Over 6000 LPs were extracted using a modified STA/LTA method and a family consisting of 435 similar LP events has been identified. For the first time at Turrialba volcano, full-waveform moment tensor inversion is performed to jointly determine the location and source mechanism of the events. The LPs in the family are likely to be caused by crack mechanisms dipping towards the southwest at angles of approximately 10 to 20°, located at shallow depths (< 800 m) below the active Southwest and Central craters. As the locations are so shallow, the most probable causes of crack mechanisms are hydrothermal fluids resonating within or "pulsing" through a crack. The waveforms observed at the summit stations suggest a "pulsing" mechanism, but source resonance with a high degree of damping is also possible.

Eyre, Thomas S.; Bean, Christopher J.; De Barros, Louis; O'Brien, Gareth S.; Martini, Francesca; Lokmer, Ivan; Mora, Mauricio M.; Pacheco, Javier F.; Soto, Gerardo J.

2013-05-01

116

Systematic Survey of the Kermadec-Tonga Intra-oceanic arc Between 1999 and 2004: a Significant Source of Diverse Submarine Hydrothermal Emissions  

Microsoft Academic Search

The 1999 NZAPLUME cruise was the first of several expeditions to systematically locate, and chemically characterise, submarine hydrothermal vents associated with arc volcanoes of the southern part the Kermadec-Tonga intra-oceanic arc system. This was followed by the 2002 NZAPLUME II and 2004 NZAPLUME III cruises to the mid- and northern-sections of the Kermadec arc, respectively, and the 2001 TELVE cruise

C. E. de Ronde; G. J. Massoth; E. T. Baker; J. E. Lupton; R. J. Arculus; I. C. Wright; P. Stoffers; J. Ishibashi; S. L. Walker; R. R. Greene; K. Faure; K. Takai

2004-01-01

117

LA-ICPMS Measurements of Pb Isotopes and Th/U Ratios of HSDP Glasses from the Submarine Section of Mauna Kea Volcano  

NASA Astrophysics Data System (ADS)

We have developed a LA-ICPMS technique to simultaneously determine Pb isotopes, Th, U and other trace element concentrations in small glass samples. The experiments were done with a New Wave UP-213 laser system and an Element 2 ICP mass spectrometer. The glasses were ablated for 60 s in single spots 120 ? m in diameter, applying a laser energy density of 7mJ/cm2 and a pulse repetition rate of 10 Hz. The geological MPI-DING reference glasses (Jochum et al., 2000), for which high precision isotope data are now available, were used to determine the mass bias of Pb isotopes and to calibrate the trace element data. Reproducibility (RSD) of the Pb isotope data for concentrations of about 0.5 - 2 ppm is about 0.2 - 0.7 % (208/206), 0.2 - 0.5 % (207/206) and better than 1.5 % (206/204, 207/204, 208/204), respectively. The quantity of Pb measured for one analysis is about 3 pg for a Pb concentration of 1 ppm. Th/U ratios are determined with a precision of about 1 - 3 %. Overall analytical uncertainties of the trace element concentration data are about 5 - 10 %. We have applied the technique for the direct analysis of carefully handpicked glass fragments from 19 samples of the submarine section of the Hawaii Scientific Drilling Project 2 (HSDP2). Some samples provided just a few glass chips. Samples cover the depth interval from 1314 to 3060 mbsl. Three to four fresh, 200 - 500 ? m large, fragments of each sample were analyzed. In these fragments the results are indistinguishable at each spot implying a homogeneous distribution of trace elements. Our results show that 208Pb/206Pb ratios vary significantly along the stratigraphic column of the HSDP2-core ranging between 2.070 and 2.121. The lowest values are found in samples coming from depths around 1400, 2800 and 3000 mbsl whereas the highest ratios are measured in samples of 2100 mbsl depth. These microanalytical data agree with the high-precision TIMS data of Eisele et al. (2003) who found temporal variations of Pb isotopes in the whole HSDP2-core. Attributing varying isotope ratios to source heterogeneities can be confirmed when considering trace element ratios. This is best demonstrated by the correlation of the element ratio of Th and U that are parent nuclides of 208Pb and 206Pb with the 208Pb/206Pb ratios measured in the same glass fragments. Ref.: Jochum et al. (2000), Geostandards Newsletter 24, 87-133; Eisele et al. (2003), Geochem. Geophys. Geosyst. 4 (5), 8710.

Jochum, K. P.; Amini, M. A.; Stoll, B.; Herwig, K.; Hofmann, A. W.

2003-12-01

118

Characterization and location of infrasonic sources in active volcanoes: Mount Etna, September-November 2007  

NASA Astrophysics Data System (ADS)

The period September-November 2007 was characterized at Mount Etna by explosive activity and intense degassing. During this time interval, infrasonic signals were recorded by an infrasonic network. By a triggering procedure, about 1000 infrasonic events were found, characterized by very high signal-to-noise ratio and grouped into nine families. Successively, the spectral analysis allowed subdividing these nine families into three clusters based on the peak frequency and the quality factor of the events. Finally, by the location analysis a cluster (cluster 1) was related to the degassing activity of the northeast crater (NEC), while the other two (clusters 2 and 3) to the explosive activity of the southeast crater (SEC). The comparison between the stacked infrasonic waveforms, interpreted as generated by the vibration of large gas bubbles, and the synthetic ones, permitted to calculate radius, length of the bubble, and initial overpressure, by a genetic algorithm method. The higher overpressure values of cluster 3 compared to the cluster 2 values were in good agreement with the stronger intensity of the explosions accompanying the infrasonic events of cluster 3. The variation of both intensities and waveforms is tentatively attributed to the occasional accumulation of lithic clasts (due to moderate landslides?) on the explosive vent. Indeed, events belonging to cluster 3 were no longer observed once the landslides had ended. Finally, the daily emitted gas volume, related to the active degassing, was estimated for NEC and SEC by using the infrasonic data during the studied period.

Cannata, A.; Montalto, P.; Privitera, E.; Russo, G.

2009-08-01

119

Large landslides from oceanic volcanoes  

Microsoft Academic Search

GLORIA sidescan sonar surveys have shown that large landslides are ubiquitous around the submarine flanks of Hawaiian volcanoes, and GLORIA has also revealed large landslides offshore from Tristan da Cunha and El Hierro. On both of the latter islands, steep flanks formerly attributed to tilting or marine erosion have been reinterpreted as landslide headwalls mantled by younger lava flows. Large

Robin T. Holcomb; Roger C. Searle

1991-01-01

120

Submarine fans  

NASA Astrophysics Data System (ADS)

Seisimic evidence from a study of 35-m.y.-old sediment contradicts the prevailing theory that bottom currents are the main cause of sediment distribution patterns and the shape of the continental rise.In the research area 200 miles offshore from New Jersey to Cape Hatteras, N.C., Stanley D. Locker of the University of South Florida, St. Petersburg, has found that submarine fans and deep-sea sediment drifts may develop simultaneously as companion systems. He presented his work at the Geological Society of America meeting in St. Louis, Mo., November 6-9.

Bush, Susan M.

121

COMPARISON OF EARTHQUAKE LOCATIONS DETERMINED WITH DATA FROM A NETWORK OF STATIONS AND SMALL TRIPARTITE ARRAYS ON KILAUEA VOLCANO, HAWAII  

Microsoft Academic Search

The hypocenters of 43 earthquakes on Kilauea Volcano were analyzed in detail in order to examine the accuracy of hypocenters determined with data from tripartite arrays and to look for evidence of zones of abnormally high or low velocity in a region of complex crustal structure. Ten vertical and two horizontal seismometers were operated on the south flank of Kilauea

PETER L. WARD; SOREN GREGERSEN

122

Hawaiian Shield Stage Submarine Volcaniclastics: Insights From HSDP Core  

NASA Astrophysics Data System (ADS)

Ocean island volcanoes are traditionally associated with the non-explosive eruption of fluid lavas, but volcaniclastic rocks comprise a significant portion of many submarine shield volcanoes. Deep drilling (3,098 m) by the Hawaiian Scientific Drilling Project (HSDP) into the flank of Mauna Kea volcano has exposed the volcaniclastics within the pedestals of a Hawaiian volcano that were previously poorly known. The HSDP continuously cored 2,019 m of submarine Mauna Kea deposits with ˜95% recovery and revealed that volcaniclastics comprise ˜55% of this section. The shallow submarine section consists of ˜80% volcaniclastics interbedded with thin ( ˜3 m) massive lava flows and the deep section is ˜35% volcaniclastics interbedded with packages of pillow lavas up to 180 m thick. Throughout the submarine section, the volcaniclastics can occur in thick packages up to ˜100 m. The emplacement of submarine volcaniclastics is not well understood. Possible origins include primary fragmentation of lava via magmatic explosivity and magma-water interactions, and secondary fragmentation via erosion. Secondary transport of material down the steep submarine flanks by gravity flows is expected to be common, as is reworking by currents. Emplacement processes are predicted to evolve as the volcano shoals. In this study major element analyses of glassy clasts in the volcaniclastics are used to distinguish monomict and polymict assemblages, which can indicate primary versus secondary fragmentation. Clast shapes reflect fragmentation mechanisms and secondary processes and this study attempts to improve on this approach with quantitative analysis of clast shapes for the HSDP volcaniclastics and for samples of known origin. The first documentation of the textures of the Mauna Kea volcaniclastics, integrated with geochemistry, petrography, and quantitative clast shape analysis and inferences about their origins and modes of transport and deposition will be presented to better understand the shoaling of Hawaiian volcanoes.

Bridges, K. P.; Garcia, M.; Houghton, B.; Thordarson, T.

2003-12-01

123

In Brief: Underwater volcano gets real-time monitoring  

NASA Astrophysics Data System (ADS)

A real-time underwater earthquake monitoring system was installed on the top of Kick'em Jenny, an underwater volcano located off the north coast of Grenada, on 6 May. The Real Time Offshore Seismic Station (RTOSS) consists of an ocean-bottom seismometer connected by a stretchy hose to a buoy on the ocean surface. The buoy is powered by solar panels and transmits seismic data by high-frequency radio to an observatory in Sauteurs, Grenada. The RTOSS research team, led by scientists from the Woods Hole Oceanographic Institution, is coordinating with the Grenadian National Disaster Management Agency and the Seismic Unit of the University of the West Indies to incorporate the RTOSS data into existing regional monitoring. Kick'em Jenny, the only `live' submarine volcano in the West Indies, last erupted in 2001.

Zielinski, Sarah

2007-05-01

124

Volcanoes of North America  

NASA Astrophysics Data System (ADS)

Volcanoes of North America capitalises on the vast body of volcano literature now available to present, in a single source, detailed information about volcanoes found in North America. It contains brief accounts, written by leading experts in volcanology, of over 250 volcanoes and volcanic fields formed during the last 5 million years. The volcanoes of the continental United States, Alaska, Hawaii, and Canada are described. The precise location of each volcano is given, and the volcano is classified by type. Information about composition and eruptive history is also included. Each narrative description is accompanied by a photograph, a map of each location, and an extremely helpful statement on how to reach each volcano. The entries are mostly written at a level understandable by lay readers, but technical terms are also used and a background in geology is advantageous. Volcanoes of North America will be a standard reference work for practising volcanologists, petrologists, and geochemists, and to some extent, geographers. In addition, the maps and the 'How to get there' sections make this a highly valuable book for anyone interested in natural history or fascinated by volcanoes.

Wood, Charles Arthur; Kienle, Jürgen

1992-11-01

125

Expulsion of Barium and Methane at Mud Volcanoes in the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes and cold-seeps along continental margins transfer methane from gas-charged marine sediments to the water column. Such methane venting is dynamic and may provide an important and variable supply of carbon to the ocean and atmosphere through time. Barite mounds and chimneys have been found around some modern mud volcanoes and seeps, and similar structures can be identified in the geological record (e.g., bedded barite deposits). These observations suggest that expelled methane-rich fluids are greatly enriched in dissolved barium. However, there are very few analyses of barium concentrations in these systems. Here, we examine the dissolved barium of pore fluids from a series of shallow piston cores across two submarine mud volcanoes in the Gulf of Mexico. Dissolved barium concentrations at 1.5 m below the seafloor at the Garden Bank volcano range from 18200 ? M at the center of the feature to 0.56 ? M on its flanks approximately 1 km away. Similarly, dissolved barium concentrations at the Mississippi Canyon volcano range from 15600 ? M to 0.50 ? M. Thus, the concentrations in the cores of the mud volcanoes are nominally 5 orders of magnitude greater than in mean ocean water ( ˜0.1 ? M). Anaerobic oxidation of upward flowing methane consumes sulfate, which leads to the dissolution of barite and release of barium to pore fluids. Because this mechanism alone cannot explain the extreme concentrations in the mud volcanoes, a deep source of barium may exist in the Gulf of Mexico strata. Our current work is focused on quantifying the fluxes and sedimentary fate of expelled barium at these locations. However, even if a large fraction of the barium precipitates adjacent to the sites of methane venting, fluid expulsion at mud volcanoes must significantly impact the barium cycle in the Gulf of Mexico. Conceivably, submarine mud volcanoes and cold-seeps along continental margins are a major source of barium to the deep ocean, a concept that has profound implications with respect to certain paleoceanographic reconstructions.

Castellini, D. G.; Dickens, G. R.; Snyder, G. T.; Gilhooly, W. P.; Ruppel, C. D.

2003-12-01

126

Systematic Survey of the Kermadec-Tonga Intra-oceanic arc Between 1999 and 2004: a Significant Source of Diverse Submarine Hydrothermal Emissions  

NASA Astrophysics Data System (ADS)

The 1999 NZAPLUME cruise was the first of several expeditions to systematically locate, and chemically characterise, submarine hydrothermal vents associated with arc volcanoes of the southern part the Kermadec-Tonga intra-oceanic arc system. This was followed by the 2002 NZAPLUME II and 2004 NZAPLUME III cruises to the mid- and northern-sections of the Kermadec arc, respectively, and the 2001 TELVE cruise to the southern part of the Tonga (Tofua) arc. Combined, ˜1,800 km of this arc system have been mapped, including ˜60 major volcanoes and numerous subordinate volcanic edifices, making this the longest continuous stretch of intra-oceanic arc to be surveyed for hydrothermal emissions. Most of the volcanoes are simple cones although ˜25% are caldera volcanoes with their compositions ranging from basalt through rhyo-dacite. Results from the NZAPLUME I and II cruises show 16 of the 26 major volcanoes surveyed are hydrothermally active, while 7 of 19 are active along the Tongan section of the arc, a ˜50% frequency of venting. Depths to venting range from ˜120 m to ˜1,650 m. Chemical analysis of the hydrothermal plumes shows a large range in composition, including different compositions for plumes from vent sites at the same volcano, with indications locally of a magmatic fluid component. An expedition in Oct./Nov. 2004 by the deep-sea submersible Shinkai 6500 will enable vent sites at Brothers and Healy volcanoes to be mapped and mineralization, animals to be sampled.

de Ronde, C. E.; Massoth, G. J.; Baker, E. T.; Lupton, J. E.; Arculus, R. J.; Wright, I. C.; Stoffers, P.; Ishibashi, J.; Walker, S. L.; Greene, R. R.; Faure, K.; Takai, K.

2004-12-01

127

Volcanoes Galore!  

NSDL National Science Digital Library

Here, you can check out videos and links to lots of nifty volcano stuff. Have fun! This is completely unrelated...but check it out anywho. sweet periodic table! Alaska Volcano Observatory Earthquakes and Volcanoes Check this one out for info on history\\'s most distructive volcano. Exploring Pompeii and Vesuvius Exploring the Environment: Volcanoes This will give you lots of background on how Volcanoes work, what the major parts are, and how they erupt. How Volcanoes Work A quick video on how to take a lava sample...hot! Lava Sampling on Kilauea Volcano, Hawai i A volcano in antartica? ...

Syracuse, Mr.

2008-06-11

128

Submarine Explosive Eruptions: Physical Volcanology of NW Rota-1, Marianas  

NASA Astrophysics Data System (ADS)

The discovery of an actively erupting submarine arc volcano is a scientific breakthrough that greatly extends our understanding of submarine volcanism. NW Rota-1, located at 14¢X40'N in the Mariana volcanic arc, is a conical basaltic andesite volcano with a summit at 517 m b.s.l, a base at 2700 m, and a diameter of 16- km. In April 2006, on the most recent cruise of the "Submarine Ring of Fire" (SROF) expeditions, violently explosive submarine eruptions were observed and sampled at the active vent, Brimstone Pit (550 m depth), through the use of JASON II remotely operated vehicle (ROV). During six dives repeated observations made at close range over a week documented a diverse and increasingly energetic range of activity that culminated in explosive bursts of glowing red lava propelled by violently expanding gases. Preliminary work shows erupted clasts to vary greatly in density (vesicularity) and crystallinity. Densities of representative larger clasts are moderately high (1700-1900 kg/m3, or ~ 30-40% vesicularity assuming a solid density of 2800 kg/m3; Fig 5b), although the more vigorous activity clearly produced some lower density (< 1000 kg/m3;> 66% vesicularity) material. Grain sizes were measured in 1.0 intervals from -5 to 3 using dry sieving techniques. The grain size distribution is approximately log normal with a mode at -1 (2 mm). Clast morphology consists of three components: (1) very glassy juveniles ranging from light to dark brown (sideromelane), often fluidal and irregularly shaped with obvious vesicle stretching, (2) phenocryst-rich blocky juveniles ranging from dark brown to black (tachylite), (3) non-juvenile lithics are equant, often rounded, ranging from light grey to dark grey and are often coated with altered material. Initial FTIR analyses show a lack of CO2 and a range of H20 from 0.3-1.15wt%, with the average approximately in equilibrium for 550 m water depth. The high vesicularity of the samples collected directly from Brimstone Pit and equilibrium volatile content preserved in the glass suggest that most of the explosive power of the eruptions was generated by magmatic degassing rather than by magma-seawater interaction. This observation highlights the role of high volatile contents in generating explosive eruptions of mafic arc magmas.

Deardorff, N. D.; Chadwick, W. W.; Embley, R. W.; Cashman, K. V.

2006-12-01

129

Submarine Volcanic Morphology of Santorini Caldera, Greece  

NASA Astrophysics Data System (ADS)

Santorini volcanic group form the central part of the modern Aegean volcanic arc, developed within the Hellenic arc and trench system, because of the ongoing subduction of the African plate beneath the European margin throughout Cenozoic. It comprises three distinct volcanic structures occurring along a NE-SW direction: Christianna form the southwestern part of the group, Santorini occupies the middle part and Koloumbo volcanic rift zone extends towards the northeastern part. The geology of the Santorini volcano has been described by a large number of researchers with petrological as well as geochronological data. The offshore area of the Santorini volcanic field has only recently been investigated with emphasis mainly inside the Santorini caldera and the submarine volcano of Kolumbo. In September 2011, cruise NA-014 on the E/V Nautilus carried out new surveys on the submarine volcanism of the study area, investigating the seafloor morphology with high-definition video imaging. Submarine hydrothermal vents were found on the seafloor of the northern basin of the Santorini caldera with no evidence of high temperature fluid discharges or massive sulphide formations, but only low temperature seeps characterized by meter-high mounds of bacteria-rich sediment. This vent field is located in line with the normal fault system of the Kolumbo rift, and also near the margin of a shallow intrusion that occurs within the sediments of the North Basin. Push cores have been collected and they will provide insights for their geochemical characteristics and their relationship to the active vents of the Kolumbo underwater volcano. Similar vent mounds occur in the South Basin, at shallow depths around the islets of Nea and Palaia Kameni. ROV exploration at the northern slopes of Nea Kameni revealed a fascinating underwater landscape of lava flows, lava spines and fractured lava blocks that have been formed as a result of 1707-1711 and 1925-1928 AD eruptions. A hummocky topography at the area that lies between the town of Fira on the main island of Santorini and Nea Kammeni has been revealed. The lower slopes were covered with landslide debris which consisted of lava blocks mostly mantled with soft sediment. At the upper slopes an abrupt cliff face was exposed that was highly indurated by biologic material. At the top of a volcanic dome, a crater with its deepest part at 43m, its rim at about 34m with an approximately 8m diameter was also found. Shimmery water with temperatures as much as 25°C above ambient was observed there but the source of venting has not yet been found. The combination of ROV video footage and multibeam data provide new information about the main morphological characteristics of Santorini Caldera which demonstrates the intense geodynamic processes occurring at the central part of the active Hellenic volcanic arc. These results will be useful for the interpretation of understanding the offshore volcanic area and its linkage with the onshore structures.

Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

2012-04-01

130

Location and mechanism of very long period tremor during the 2008 eruption of Okmok Volcano from interstation arrival times  

Microsoft Academic Search

We describe continuous, very long period (VLP) tremor that occurred during the 2008 eruption of Okmok Volcano, Alaska. Due to its low frequency content in band from the 0.2–0.4 Hz, the wave field of the VLP tremor is relatively free of path effects. From continuous recordings of the VLP tremor on 2 three-component broadband and 3 single-component short-period instruments, we

M. M. Haney

2010-01-01

131

Jun Jaegyu Volcano: A Recently Discovered Alkali Basalt Volcano in Antarctic Sound, Antarctica  

NASA Astrophysics Data System (ADS)

Jun Jaegyu is a young volcanic construct discovered in May 2004 by researchers aboard the National Science Foundation (NSF) vessel Laurence M. Gould (LMG04-04). The volcano is located on the Antarctic continental shelf in Antarctic Sound, approximately 9 km due north of the easternmost point of Andersson Island. Swath bathymetry (NBP01-07) indicates that the volcano stands 700 meters above the seafloor, yet remains 275 meters short of the ocean surface. The seamount lies along a northwest-southeast oriented fault scarp and contains at least 1.5 km3 of volcanic rock. Video recording of the volcano's surface revealed regions nearly devoid of submarine life. These areas are associated with a thermal anomaly of up to 0.052° C higher than the surrounding ocean water. A rock dredge collected ~13 kg of material, over 80% of which was fresh volcanic rock; the remainder was glacial IRD. These observations, along with reports by mariners of discolored water in this region of Antarctic Sound, suggest that the volcano has been recently active. The basalt samples are generally angular, glassy and vesicular. Preliminary petrographic observations indicate that plagioclase, olivine, and clinopyroxene are all present as phenocryst phases, and that small (<1cm) rounded xenoliths are common. A comprehensive study of the volcano's petrography and whole-rock chemistry is currently underway. Jun Jaegyu is the northernmost volcanic center of the James Ross Island Volcanic Group (JRIVG), and the only center in this region of the Antarctic Peninsula with evidence of recent activity. It lies along the boundary between the Late Cenozoic JRIVG and the Upper Paleozoic rocks of the Trinity Peninsula Formation. While the tectonic setting of the region is complex, volcanism appears to be associated with active faults related to within-plate extension.

Hatfield, A.; Bailey, D.; Domack, E.; Brachfeld, S.; Gilbert, R.; Ishman, S.; Krahmann, G.; Leventer, A.

2004-12-01

132

Correlation of submarine deposits and witness accounts of the 1952 Myojinsho submarine eruption, Izu-Bonin arc, by bathymetric survey  

Microsoft Academic Search

The relationship between eruptive phenomena during the 1952 phreatomagmatic eruption and consequent deposits under seawater is discussed, on the basis of bathymetric survey of Myojinsho volcano, Izu-Bonin island arc (32°55'N, 140°00'E). We carried out some research cruises by the ship Natsushima (JAMSTEC) in 2006-2008. We used unmanned bathymetric vehicle, Hyperdolphin, for observation and sampling of the submarine deposit. Myojinsho volcano

T. Shimano; K. Tani; F. Maeno; R. S. Fiske; H. Shukuno; K. Ito; G. Shimoda; Y. J. Suzuki; T. Yoshida; H. Taniguchi

2009-01-01

133

Examination of the constructional processes of submarine Cerro Azul and the Galapagos Platform  

NASA Astrophysics Data System (ADS)

One of the primary goals of the 2001 Drift04 cruise was to examine the constructional processes responsible for the Galapagos platform and to investigate the relationship between the platform and the overlying volcanoes. Cerro Azul volcano is located above the steep escarpment that marks the southwestern limit of the Galapagos platform, at the leading edge of the hotspot. This area is of particular interest in light of a recent seismic tomography experiment by Toomey, Hooft, et al., which suggests that the root of the Galapagos plume is centered between Cerro Azul and adjacent Fernandina Island. During the Drift04 cruise, detailed bathymetric and sidescan sonar studies were carried out across the submarine sector of Cerro Azul and 14 dredges were collected from the same area. Major element analyses of the submarine lavas indicate that the lavas from the platform edge and the subaerial Cerro Azul lavas constitute a suite of petrologically-related lavas. The dredged glasses of the Drift04 cruise have MgO contents of <7.5% and are indistinguishable from published data on Cerro Azul. Whole rock analyses include a highly primitive sample (20 wt% MgO), which probably contains accumulated olivine. All the submarine and subaerial lavas define coherent trends in major element space that are consistent with variable amounts of olivine and olivine+cpx fractionation. Incompatible trace element (ITE) ratios indicate that the mantle source for the submarine platform flows is intermediate in composition between the magmas supplying Fernandina and Cerro Azul. Previous researchers have proposed that two mantle endmembers are interacting across the leading edge of the plume, one focused at Fernandina and the other at Floreana Island. The intermediate ITE ratios of the submarine and subaerial Cerro Azul lavas are consistent both geographically and compositionally with this hypothesis. Naumann and co-workers concluded that the lavas erupted at Cerro Azul were stored in small, ephemeral magma chambers, which formed as the result of a low magma supply to the edge of the platform. We propose that the lavas of the western edge of the Galapagos Platform originate from either the same or a similar network of magma chambers as those responsible for Cerro Azul volcano.

Lambert, M. K.; Harpp, K. S.; Geist, D. J.; Fornari, D. J.; Kurz, M. D.; Koleszar, A. M.; Rollins, N. A.

2004-05-01

134

Triggering and dynamic evolution of the LUSI mud volcano, Indonesia  

Microsoft Academic Search

Mud volcanoes are geologically important manifestations of vertical fluid flow and mud eruption in sedimentary basins worldwide. Their formation is predominantly ascribed to release of overpressure from clay- and organic-rich sediments, leading to impressive build-up of mud mountains in submarine and subaerial settings. Here we report on a newly born mud volcano appearing close to an active magmatic complex in

A. Mazzini; H. Svensen; G. G. Akhmanov; G. Aloisi; S. Planke; A. Malthe-Sørenssen; B. Istadi

2007-01-01

135

Submarine Fernandina: Magmatism at the leading edge of the Galápagos hot spot  

Microsoft Academic Search

New multibeam and side-scan sonar surveys of Fernandina volcano and the geochemistry of lavas provide clues to the structural and magmatic development of Galápagos volcanoes. Submarine Fernandina has three well-developed rift zones, whereas the subaerial edifice has circumferential fissures associated with a large summit caldera and diffuse radial fissures on the lower slopes. Rift zone development is controlled by changes

Dennis J. Geist; Daniel J. Fornari; Mark D. Kurz; Karen S. Harpp; S. Adam Soule; Michael R. Perfit; Alison M. Koleszar

2006-01-01

136

SUBMARINE AUTOMATION: DEMONSTRATION #5  

Microsoft Academic Search

This paper describes the results obtained in the final performing period of the ARPA sponsored submarine automation project1. Efforts on the mapping between the submarine operational environment and the RCS software architecture lead to the result of three watch station graphic user interface panels. The submarine automation model has been expanded to include some engineering systems control capability. On the

Hui-Min Huang; Richard Quintero

137

Prodigious submarine landslides on the Hawaiian Ridge  

NASA Astrophysics Data System (ADS)

The extensive area covered by major submarine mass wasting deposits on or near the Hawaiian Ridge has been delimited by systematic mapping of the Hawaiian exclusive economic zone using the side-looking sonar system GLORIA. These surveys show that slumps and debris avalanche deposits are exposed over about 100,000 km2 of the ridge and adjacent seafloor from Kauai to Hawaii, covering an area more than 5 times the land area of the islands. Some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume, ranking them among the largest on Earth. The slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts, culminate near the end of subaerial shield building, and apparently continue long after dormancy. Consequently, landslide debris is an important element in the internal structure of the volcanoes. The dynamic behavior of the volcanoes can be modulated by slope failure, and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems. The landslides are of two general types, slumps and debris avalanches. The slumps are slow moving, wide (up to 110 km), and thick (about 10 km) with transverse blocky ridges and steep toes. The debris avalanches are fast moving, long (up to 230 km) compared to width, and thinner (0.05-2 km); they commonly have a well-defined amphitheater at their head and hummocky terrain in the lower part. Oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high-level wave deposits (such as the 365-m elevation Hulopoe Gravel on Lanai) that are found on several islands. Most present-day submarine canyons were originally carved subaerially in the upper parts of debris avalanches. Subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters.

Moore, J. G.; Clague, D. A.; Holcomb, R. T.; Lipman, P. W.; Normark, W. R.; Torresan, M. E.

1989-12-01

138

Addressing the Challenges of a Smoke-Free U.S. Navy Submarine Force.  

National Technical Information Service (NTIS)

Traditionally submarines have had a smoking space. A study conducted 2007-9 concluded nonsmokers are exposed to significant levels of environmental tobacco smoke, regardless of location on the submarine. In 2009, a working group was established to create ...

F. Yeo J. McQuade L. Williams M. Long

2011-01-01

139

Precise Hypocenter Location of High-Frequency-Onset Earthquakes, During the Initial Stages of Activity at Soufriere Hills Volcano, Montserrat  

NASA Astrophysics Data System (ADS)

Volcano-tectonic (VT) earthquakes are interpreted as resulting from slip on fractures or faults induced by magma pressurisation. Examination of VT earthquakes can provide information on areas of magma storage and any induced stress state due to such pressurisation. The andesite stratovolcano of Soufriere Hills, Montserrat began showing an increase in seismicity in 1992, with this rapidly increasing towards the end of 1994. The eruption commenced in July 1995 with phreatic activity and during the subsequent and ongoing eruption there have been several phases, with VT seismicity varying throughout this period. Here we use data from the initial stages (July 1995 - October 1996) of activity on Montserrat to better characterise the magma storage and transport system, and stress changes which have occurred during this eruption. Recent developments have allowed more precise hypocenter relocations using relative positioning techniques. Therefore we have examined seismic data recorded at SHV, utilising the Waldhauser and Ellsworth (2000) precise relocation technique. Previous work by Aspinall et al. (1998) highlighted three main clusters, one stretching out from the summit to the NE (the Arm) showing a SW progression through time, another mass of hypocentres under St. Georges Hill and a NW-SE trending summit cluster which extended from the surface down to ~5km. Our results are comparable, but the decreased relative position errors in this study enable further analysis. We show that not only did hypocenters migrate to the SW through time in the Arm cluster, but also with decreasing depth. The St. Georges Hill cluster is also elongated and shows a temporal movement of hypocenters deepening to the NW with time. A second phase of seismicity clustered beneath the summit mainly between 1.3 and 2.3 km depth below sea level during early 1996. These hybrid events accompanied a significant increase in extrusion rate. This summit cluster persisted with a NW-SE trend in map view.

Miller, V. L.; Ammon, C. J.; Voight, B.; Thompson, G.

2006-12-01

140

Cascades Volcano Observatory - Learn About Volcanoes: Frequently Asked Volcano Questions  

NSDL National Science Digital Library

This page provides the answers to frequently asked questions about volcanoes. It is created by the United States Geological Survey. Topics addressed include: What Is A Volcano? Why Do Volcanoes Occur? How Do Volcanoes Erupt? Where Do Volcanoes Occur? When Will A Volcano Erupt? How Hot Is A Volcano? Can Lava Be Diverted? Do Volcanoes Affect Weather? What Types of Volcanoes are There? Which Eruptions Were The Deadliest? 20th Century Volcanic Eruptions and Their Impact. About 60 additional questions with answers are available under MORE FAQ's -Volcano Questions and Answers, and includes some sections on volcanoes of the western United States. Other links to volcano information are also available.

141

Location of seismic events and eruptive fissures on the Piton de la Fournaise volcano using seismic amplitudes  

USGS Publications Warehouse

We present a method for locating the source of seismic events on Piton de la Fournaise. The method is based on seismic amplitudes corrected for station site effects using coda site amplification factors. Once corrected, the spatial distribution of amplitudes shows smooth and simple contours for many types of events, including rockfalls, long-period events and eruption tremor. On the basis of the simplicity of these distributions we develop inversion methods for locating their origins. To achieve this, the decrease of the amplitude as a function of the distance to the source is approximated by the decay either of surface or body waves in a homogeneous medium. The method is effective for locating rockfalls, long-period events, and eruption tremor sources. The sources of eruption tremor are usually found to be located at shallow depth and close to the eruptive fissures. Because of this, our method is a useful tool for locating fissures at the beginning of eruptions.

Battaglia, J.; Aki, K.

2003-01-01

142

Collapsing volcanoes  

Microsoft Academic Search

A series of studies has been conducted which examined Landsat images of volcanoes in the central Andes in order to identify previously unknown avalanche deposits, with attention to the Socompa volcano in Chile. The occasional, massive collapse of an unstable volcanic cone may be seen as a normal event in the life cycle of a volcano; this is especially true

Peter Francis; Stephen Self

1987-01-01

143

Tectonic Plates, Earthquakes, and Volcanoes  

NSDL National Science Digital Library

According to theory of plate tectonics, Earth is an active planet -- its surface is composed of many individual plates that move and interact, constantly changing and reshaping Earth's outer layer. Volcanoes and earthquakes both result from the movement of tectonic plates. This interactive feature shows the relationship between earthquakes and volcanoes and the boundaries of tectonic plates. By clicking on a map, viewers can superimpose the locations of plate boundaries, volcanoes and earthquakes.

2011-05-12

144

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2010-07-01

145

33 CFR 165.1328 - Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA.  

Code of Federal Regulations, 2013 CFR

...Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA. 165.1328 Section...Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA. (a) Location...Washington whenever any U.S. Navy submarine is operating in the Hood Canal and is being...

2013-07-01

146

33 CFR 209.310 - Representation of submarine cables and pipelines on nautical charts.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Representation of submarine cables and pipelines on nautical charts...PROCEDURE § 209.310 Representation of submarine cables and pipelines on nautical charts...with respect to showing the locations of submarine cables and pipelines on nautical...

2009-07-01

147

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2009-07-01

148

33 CFR 209.310 - Representation of submarine cables and pipelines on nautical charts.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Representation of submarine cables and pipelines on nautical charts...PROCEDURE § 209.310 Representation of submarine cables and pipelines on nautical charts...with respect to showing the locations of submarine cables and pipelines on nautical...

2010-07-01

149

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2013-07-01

150

U. S. Geological Survey Volcano Hazards Program  

NSDL National Science Digital Library

A comprehensive overview of the U.S. Geological Survey's Volcano Hazards Program and current volcanic activity in the United States. The Volcano Hazards Program monitors volcanoes and collects the best possible scientific information on volcanoes in the United States and elsewhere to reduce the risk from volcanic activity. Site includes links to the Program's four volcano observatories in Alaska, the Cascades (Washington State) , Hawaii, and Long Valley (California). Other links include information on volcano hazards: types, effects, locations and historical eruptions, information on reducing volcanic risks, volcano monitoring, emergency planning, and warning schemes. Other resources available are a photoglossary, volcano fact sheets and videos, an educator's page, and updates and weekly reports on worldwide, U.S., and Russian volcano activity.

151

Morphology of Piton de la Fournaise basaltic shield volcano (La Réunion Island): Characterization and implication in the volcano evolution  

NASA Astrophysics Data System (ADS)

The topography of Piton de la Fournaise volcano (PdF) differs from the classic view of basaltic shield volcanoes as it is characterized by (1) several steep slope zones on its flanks and (2) a large U-shaped caldera, the Enclos-Grand Brûlé structure (EGBS). Most of these structures were previously interpreted as the scars of lateral landslides, the deposits of which cover the submarine flanks of PdF. We carried out a detailed analysis of the morphology of PdF, which reveals that the steep slope zones form two independent, circumferential structures that continue into the caldera. The development of circumferential steep slopes on volcano flanks may have several origins: constructive, destructive, and deformation processes. We interpret those processes acting on PdF as caused by the spreading of the volcanic edifice above a weak hydrothermal core, leading to outward displacements and a summit extensive stress field. The continuity of the steep slope on both sides of the EGBS escarpments suggests that this structure was not caused by a 4.5 ka old giant landslide as it is usually proposed but is due to a mainly vertical collapse. The recent debris avalanche deposits east of the island indicate that this event likely destabilized part of the submarine flank. We propose that the collapse of the Grand Brûlé, the lower half of the EGBS, was due to the downward drag related to the dense intrusive complex of the Alizés volcano, which is located 1 km below the Grand Brûlé. The collapse of the Enclos is interpreted as the consequence of the deformation of the hydrothermal system of the pre-Enclos volcano. Although the continuity of the geological and morphological structures between the Enclos and the Grand Brûlé suggests a narrow link between these two collapse events, their chronology and relationship are still uncertain. Finally, we hypothesize that the persistence of the NE and SE rift zones during the last 150 ka, despite the large changes of the topography related to the recurrent flank destabilizations, is linked to a deep sources, which can be either underlying crustal faults or the continuous downward subsidence of the Alizés intrusive complex.

Michon, Laurent; Saint-Ange, Francky

2008-03-01

152

Primitive Submarine Basalts and Magmatic Variation of Pagan and Daon, Mariana Arc  

NASA Astrophysics Data System (ADS)

Pagan is an active volcano located in the central island province of the Mariana arc (18°07'N) and is one of the largest volcanoes in the Mariana arc; its main edifice rises from a base ~3,000 m below sea level (b.s.l.) and has a volume of 2,160 km3 (Bloomer et al., 1989). Daon is a small reararc seamount 25 km SW of Pagan (17°58'N). We visited the submarine portions of the two volcanoes in 2010 (NT10-12), using ROV Hyper-Dolphin and RV Natsushima. Rocks were collected from the northeastern and southwestern flanks of the Pagan volcano at 1,500-2,000 m b.s.l. (dive HPD1147) and at 2,020-2,330 m b.s.l. (HPD1148), respectively, and from the southern flank of Daon at 2,360-2,580 m b.s.l. (HPD1149). Fresh pillow lavas dominate in all three dives, but the rocks recovered from HPD1147 seem to be the youngest based on very light sediment cover and no Mn coating. Sediment cover is considerably more extensive at HPD1148, and all rocks from Daon (HPD1149) had 0-10 mm thick Mn coating. Submarine Pagan lavas show major element compositions typical of subaerial Pagan basalts (Marske et al., 2011; Elliott et al., 1997; Woodhead, 1989), although the least fractionated compositions recovered from HPD1147 extend to much higher MgO (7-11 wt %) and Mg# (60-70), than the subaerial lavas. We recognize two types of primitive basalts from Pagan and Daon. Daon has plagioclase-olivine basalt (POB) and clinopyroxene-olivine basalt (COB), petrographic types that are similar to those reported from NW Rota-1 volcano (Tamura et al., 2011). Pagan has two types of COB, both having 10-11 wt % MgO; COB-1 has higher Ba/Zr and Sr/Zr and lower Zr/Y than COB-2 at the same MgO content, indicating that COB-1 has a greater subduction component and formed from higher degrees of mantle melting than COB-2. Similar distinct primitive magmas like those recognized from NW Rota-1 also coexist at Pagan and Daon.

Tamura, Y.; Ishizuka, O.; Stern, R. J.; Nunokawa, A.; Shukuno, H.; Kawabata, H.; Embley, R. W.; Bloomer, S. H.; Nichols, A. R.; Tatsumi, Y.

2011-12-01

153

Plunge Pools in Submarine Canyons  

NASA Astrophysics Data System (ADS)

Many submarine canyon systems include well-defined intra-canyon depressions. Often, these depressions are found at the base of scarps along the canyon thalweg, with morphologic characteristics similar to subarial plunge pools formed at waterfalls. One plausible mechanism for the origin of these features is scouring during submarine debris flows. Other processes which can plausibly contribute to the formation of re-entrants and depressions in submarine canyons include erosion by spring sapping, slumping, collapse following gas expulsion or subsurface dissolution, and channel damming by mass wasting of canyon walls. We have examined multibeam bathymetry surveys of a number of submarine canyons, and identified more than fifteen apparent plunge pools within submarine canyon systems offshore of Australia, Hawaii, and North America. These features range in scale from 2 km long, 6 km across, and 300 m deep (the largest plunge pool in Perth Canyon, offshore Australia) down to as small as 10 m deep and 150 m across (the smallest plunge pool identified offshore Kohala, Hawaii). Although these features vary considerably in scale, they share common characteristics. Each basin is located at the base of a headwall scarp within the canyon, and is bounded on the down-canyon side by a sill. Measurements of the characteristic dimensions of the plunge pools show that the basin depth (defined relative to the down-canyon sill) increases with the headwall scarp height,. However, the across and down canyon basin widths do not strongly correlate with the scarp height, and seem to be more closely related to the width of the overall canyon channel. The Monterey Bay Aquarium Research Institute investigated three apparent plunge pools using ROV Tiburon during a spring 2001 expedition to the Hawaiian Islands. These basins are located in submarine canyons on the north side of Molokai and the Kohala coast of Hawaii. Our ROV observations support the hypothesis that these intra-canyon depressions are formed through scouring during submarine debris flows. In all cases the down-canyon depression sills are dams composed of debris piles, with angular rubble exposed on the depression side and sand covering the down-canyon side. The Molokai plunge pool is draped with mud and silt, suggesting no recent activity. However, the Kohala plunge pools show clear signs of recent scour and no sediment cover. The headwalls above the plunge pools expose layered volcanoclastic and lava flow units, with more resistant layers frequently forming vertical or overhanging walls. We interpret these canyons as being largely formed through retrogressive (headward) erosion and slope failure. Periodic rockfalls and debris flows following undercutting of the headwalls scours the depressions, builds the pool dams, and both lengthens and deepens the canyons. Modern bathymetric surveys indicate that plunge pools occur in many, but not most submarine canyons. Our ROV observations suggest that stratigraphic variability is a key prerequisite for plunge pool formation. Headwall scarps can persist within active canyons when the existence of more and less resistive layers allows for differential erosion. In turn, plunge pools form when headwall scarps are persistent features.

Caress, D. W.; Greene, H. G.; Paull, C. K.

2002-12-01

154

Venus small volcano classification and description  

Microsoft Academic Search

The high resolution and global coverage of the Magellan radar image data set allows detailed study of the smallest volcanoes on the planet. A modified classification scheme for volcanoes less than 20 km in diameter is shown and described. It is based on observations of all members of the 556 significant clusters or fields of small volcanoes located and described

J. C. Aubele

1993-01-01

155

Erupting Volcanoes!  

NSDL National Science Digital Library

This lesson presents volcanoes through the making of volcano models. While students are constructing their physical representations of volcanoes, they will be filled with questions about volcanoes as well as how to build their models. This process will provide students with a tangible reference for learning about volcanoes and give them a chance to problem-solve as they build their models. Students will be able to observe how the eruption changes the original form of their volcano model. In this way, students see first hand how this type of phenomenon creates physical change. While students at this level may struggle to understand larger and more abstract geographical concepts, they will work directly with material that will help them build a foundation for understanding concepts of phenomena that sculpt the Earth.

156

Seismic triggering of fluid flow in the North Alex mud volcano on the western Nile deep-sea fan  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes are generally characterized by fluid formation and fluidization occuring at depths of several kilometers below the seafloor driving a complex system of interacting geochemical, geological and microbial processes. As mud volcanoes are natural leakages of oil and gas reservoirs, near-surface observations can be used for monitoring of these phenomena occurring at great depth. North Alex Mud Volcano (NAMV), located on the upper slope of the western Nile deep-sea fan is the focus of an RWE Dea funded research project using existing and newly developed observatory technologies to better understand and quantify the internal dynamics and its long-term variability in relation to underlying gas reservoirs. As it is known that the activity of mud volcanoes varies significantly over periods of months and weeks, the assessment of the activity of NAMV focuses on proxies of fluid and gas emanations. Since the initiation of the project in 2007 NAMV has arguably become one of the best-instrumented mud volcanoes worldwide with a network of observatories collecting long-term records of chemical fluxes, seismicity, temperature, ground deformation, and methane concentration. First results from parallel measurements of fluid flow variations and seismic events in the center of NAMV show a high degree of correlation. Harmonic oscillations of the uppermost gas-saturated part of the sediment conduit (see Lefeldt et al.) clearly stimulate synchronous fluid flow and gas ebullition episodes of several days duration.

Brückmann, Warner; Lefeldt, Marten; Hölz, Sebastian; Tryon, Mike; Bialas, Jörg

2010-05-01

157

Volcano Types  

NSDL National Science Digital Library

This site lists the basic types of volcanoes: scoria cone, shield volcano, and stratovolcano. Each is described in terms of shape, composition, and eruption type, and links are available to additional information. Subordinate types listed include fissure eruptions, spatter cones, hornitos, and hydrovolcanic eruptions. The site also explains when a volcano is considered active, dormant, or extinct. In addition, generic features such as vent, central vent, edifice, magma chamber, parasitic cones, and fumaroles are listed and described.

Camp, Victor

158

Hearing Conservation for Submariners.  

National Technical Information Service (NTIS)

The report advises the U.S. Navy concerning hearing conservation aboard future submarines. Included are criteria for hazard, as well as suggested techniques for hearing protection, involving personal protection, environmental damping, and noise control at...

W. D. Ward

1971-01-01

159

Dynamic Controls of Fluid and Gas Flow at North Alex Mud Volcano, West Nile Delta  

NASA Astrophysics Data System (ADS)

The North Alex Mud Volcano (NAMV) is located at a water depth of 500m above a large deep-seated gas reservoir on the upper slope of the western Nile deep-sea fan. It has been the object of an integrated study of fluid and gas flow using existing and newly developed observatory technologies to better constrain and quantify devolatilisation and defluidisation patterns and their long-term variability in relation to underlying hydrocarbon reservoirs. As it is known that the activity of mud volcanoes varies significantly over periods of months and weeks, the assessment of the activity of NAMV focuses on proxies of fluid and gas emanations. Submarine mud volcanoes are usually characterized by fluid formation and fluidization processes occuring at depths of several kilometers below the seafloor, driving a complex system of interacting geochemical, geological and microbial processes. Mud volcanoes are natural leakages of oil and gas reservoirs. Near-surface observations made at such sites can therefore be used to monitor phenomena that occur at greater depth. Since the initiation of the project in 2007, NAMV has arguably become one of the best-instrumented mud volcanoes worldwide with a network of observatories collecting long-term records of chemical fluxes, seismicity, temperature, ground deformation, and methane concentration. In addition five research cruises collected complementary geophysical and geological data and samples. In the summer of 2010 a large number of monitoring systems has been recovered which provide us with a synoptic view of the internal dynamics of an active mud volcano. We will present an integrated analysis based on ship-based and sea-floor observations.

Brueckmann, W.; Bialas, J.; Jegen, M. D.; Lefeldt, M. R.; Hoelz, S.; Feseker, T.

2010-12-01

160

Tephra dispersal from Myojinsho, Japan, during its shallow submarine eruption of 1952–1953  

Microsoft Academic Search

A new and detailed bathymetric map of the Myojinsho shallow submarine volcano provides a framework to interpret the physical\\u000a volcanology of its 1952–1953 eruption, especially how the silicic pyroclasts, both primary and reworked, enlarged the volcano\\u000a and were dispersed into the surrounding marine environment. Myojinsho, 420?km south of Tokyo along the Izu–Ogasawara arc,\\u000a was the site of approximately 1000 phreatomagmatic

Richard S. Fiske; Katharine V. Cashman; Atsushi Shibata; Kazuki Watanabe

1998-01-01

161

Decade Volcanoes  

NSDL National Science Digital Library

In the 1990s, the International Association of Volcanology and Chemistry of the Earth's Interior started the Decade Volcano Project. As part of their work, they designated sixteen volcanoes particularly worthy of study "because of their explosive histories and close proximity to human populations." The group recently teamed up with National Geographic to create a guide to these volcanoes via this interactive map. Navigating through the map, visitors can learn about Mount Rainier, Colima, Galeras, Santorini, and other prominent volcanoes. For each volcano, there's a brief sketch that gives the date of its last eruption, its elevation, nearby population centers, and a photograph. Additionally, visitors can learn more by clicking on the sections titled "Did You Know?" and "Eruption Interactive".

2007-11-02

162

The largest Au deposits in the St Ives Goldfield (Yilgarn Craton, Western Australia) may be located in a major Neoarchean volcano-sedimentary depo-centre  

NASA Astrophysics Data System (ADS)

The largest Neoarchean gold deposits in the world-class St Ives Goldfield, Western Australia, occur in an area known as the Argo-Junction region (e.g. Junction, Argo and Athena). Why this region is so well endowed with large deposits compared with other parts of the St Ives Goldfield is currently unclear, because gold deposits at St Ives are hosted by a variety of lithologic units and were formed during at least three different deformational events. This paper presents an investigation into the stratigraphic architecture and evolution of the Argo-Junction region to assess its implications for gold metallogenesis. The results show that the region's stratigraphy may be subdivided into five regionally correlatable packages: mafic lavas of the Paringa Basalt; contemporaneously resedimented feldspar-rich pyroclastic debris of the Early Black Flag Group; coarse polymictic volcanic debris of the Late Black Flag Group; thick piles of mafic lavas and sub-volcanic sills of the Athena Basalt and Condenser Dolerite; and the voluminous quartz-rich sedimentary successions of the Early Merougil Group. In the Argo-Junction region, these units have an interpreted maximum thickness of at least 7,130 m, and thus represent an unusually thick accumulation of the Neoarchean volcano-sedimentary successions. It is postulated that major basin-forming structures that were active during deposition and emplacement of the voluminous successions later acted as important conduits during mineralisation. Therefore, a correlation exists between the location of the largest gold deposits in the St Ives Goldfield and the thickest parts of the stratigraphy. Recognition of this association has important implications for camp-scale exploration.

McGoldrick, K. L.; Squire, R. J.; Cas, R. A. F.; Briggs, M.; Tunjic, J.; Allen, C. M.; Campbell, I. H.; Hayman, P. C.

2013-10-01

163

Ash from Popocatepetl Volcano  

NASA Video Gallery

The GOES-13 satellite captured this animation of an ash cloud streaming from Mexico's Popocatepetl Volcano and blowing over the town of Puebla, located to the east. This four second black and white movie was captured over several hours during the morning of April 18, 2012. > Related story > Download video

Robert Garner

2012-04-20

164

Collapsing volcanoes  

NASA Astrophysics Data System (ADS)

A series of studies has been conducted which examined Landsat images of volcanoes in the central Andes in order to identify previously unknown avalanche deposits, with attention to the Socompa volcano in Chile. The occasional, massive collapse of an unstable volcanic cone may be seen as a normal event in the life cycle of a volcano; this is especially true in the case of large 'stratovolcanoes', of which there are many hundreds in the 'Ring of Fire' around the Pacific rim. Stratovolcanoes are susceptible to collapse because of their association with subduction zones. Three kinds of collapse can be distinguished among stratovolcanoes.

Francis, Peter; Self, Stephen

1987-06-01

165

Model Volcanoes  

NSDL National Science Digital Library

In this lesson, students will explore volcanoes by constructing models and reflect upon their learning through drawing sketches of their models. Once they have finished making their models, they will experiment with making their volcanoes erupt. They will observe how eruption changes the original form of their volcano models. In this way, students see first hand how this type of phenomena creates physical change. While students at this level may struggle to understand larger and more abstract geographical concepts, they will work directly with material that will help them build a foundation for understanding concepts of phenomena that sculpt the earth.

166

Submarine Automation: Demonstration No. 5.  

National Technical Information Service (NTIS)

The major objectives of this project are to: Demonstrate the application of the NIST RCS to submarine automation; and Refine and document the RCS methodology. This cycle of the submarine automation project emphasizes: Continuing investigating and developi...

H. M. Huang R. Quintero K. Young

1995-01-01

167

Volcano load control on dyke propagation and vent distribution: Insights from analogue modeling  

Microsoft Academic Search

The spatial distribution of eruptive vents around volcanoes can be complex and evolve as a volcano grows. Observations of vent distribution at contrasting volcanoes, from scoria cones to large shields, show that peripheral eruptive vents concentrate close to the volcano base. We use analogue experiments to explore the control of volcano load on magma ascent and on vent location. Results

M. Kervyn; G. G. J. Ernst; B. van Wyk de Vries; L. Mathieu; P. Jacobs

2009-01-01

168

Mount St. Helens VolcanoCam  

NSDL National Science Digital Library

This webcam shows a static image of Mount St. Helens taken from the Johnston Ridge Observatory. The Observatory and VolcanoCam are located at an elevation of approximately 4,500 feet, about five miles from the volcano. The observer is looking approximately south-southeast across the North Fork Toutle River Valley. The VolcanoCam image automatically updates approximately every five minutes. Other features include current conditions reports, weather updates, an image achive, and eruption movies. In addition, there are frequently asked questions, and information about using the VolcanoCam image and funding for the VolcanoCam.

169

Cascade Volcanoes  

USGS Multimedia Gallery

The volcanoes from closest to farthest are Mt. Washington, Three Fingered Jack, Mt. Jefferson. This picture is taken from Middle Sister looking north in the Cascade Range, Three Sisters Wilderness Area, Deschutes National Forest, Oregon....

2009-12-08

170

Hydroacoustics of a submarine eruption in the Northeast Lau Basin using an acoustic glider  

Microsoft Academic Search

A 1000-m Slocum glider® (Teledyne Webb Research Corporation) with CTD, turbidity, and hydrophone sensors was operated for two days in the Northeast Lau Basin. The survey was conducted near West Mata Volcano, where in November of 2008 the NOAA PMEL Vents program observed an active eruption emanating from near its summit at 1207 m-the deepest submarine activity ever to be

H. Matsumoto; S. E. Stalin; R. W. Embley; J. H. Haxel; D. R. Bohnenstiehl; R. P. Dziak; C. Meinig; J. A. Resing; N. M. Delich

2010-01-01

171

The 1989 submarine eruption off eastern Izu Peninsula, Japan: ejecta and eruption mechanisms  

Microsoft Academic Search

The submarine eruption of a new small knoll, which was named “Teishi knoll”, off eastern Izu Peninsula behind the Izu-Mariana arc occurred in the evening of 13 July 1989. This is the first historic eruption of the Higashi-Izu monogenetic volcano group. The eruption of 13 July followed an earthquake swarm near Ito city starting on 30 June. There were subsequent

Takahiro Yamamoto; Tatsunori Soya; Shigeru Suto; Kozo Uto; Akira Takada; Keiichi Sakaguchi; Koji Ono

1991-01-01

172

Multi-Fluid Hydrodynamic Calculations Of Turbidite Deposits From Submarine-Landslide Tsunamis  

Microsoft Academic Search

Calculations with the LANL multiphysics hydrocode SAGE of tsunamis produced by submarine landslides illustrate the relation between fluid rheology and the resultant morphology of the turbidite deposits seen afterwards on the seafloor. Tsunamigenic underwater landslides can have a variety of triggers: a seismic event that pushes a stable slope of granular material past its angle of repose, an underwater volcano

G. R. Gisler; R. P. Weaver; M. L. Gittings

2006-01-01

173

Active submarine volcanism on the Society hotspot swell (west pacific): A geochemical study  

Microsoft Academic Search

The present work deals with the petrography and geochemistry of lavas dredged from five active submarine volcanoes (named Mehetia, Moua Pihaa, Rocard, Teahitia, and Cyana) from the southeast end of the Society Islands hotspot trace. Most samples are basic and alkaline, ranging from 16 to 5 wt % MgO, with about 5% normative nepheline. Fractionation modelling based on major and

C. W. Devey; F. Albarede; J.-L. Cheminée; A. Michard; R. Muehe; P. Stoffers

1990-01-01

174

Degassing of metals and metalloids from erupting seamount and mid-ocean ridge volcanoes: Observations and predictions  

Microsoft Academic Search

Recently, it has been reported that the element polonium degasses from mid-ocean ridge and seamount volcanoes during eruptions. Published and new observations on other volatile metal and metalloid elements can also be interpreted as indicating significant degassing of magmatic vapors during submarine eruptions. This process potentially plays an important role in the net transfer of chemical elements from erupting volcanoes

Ken Rubin

1997-01-01

175

Making a Submarine.  

ERIC Educational Resources Information Center

Describes Archimedes principle and why a ship sinks when it gets a hole in it. Suggests an activity for teaching the concept of density and water displacement through the construction of a simple submarine. Includes materials and procedures for this activity. (KHR)

Cornacchia, Deborah J.

2002-01-01

176

The Stability of Submarines  

Microsoft Academic Search

SIR WILLIAM WHITE, in his paper in the Roy. Soc. Proceedings (vol. lxxvii. A., p. 528), discusses the hydrostatic forces tending to stability or instability of a submarine at the surface of the water. When the vessel is in motion, hydrodynamical forces come into play from the stream-line action of the water, and these also will affect the stability of

J. H. Jeans

1906-01-01

177

Submarine Dynamic Modeling  

Microsoft Academic Search

This paper discusses the development of a dynamic model for a torpedo shaped sub- marine. Expressions for hydrostatic, added mass, hydrodynamic, control surface and pro- peller forces and moments are derived from first principles. Experimental data obtained from flume tests of the submarine are inserted into the model in order to provide computer simulations of the open loop behavior of

Peter Ridley; Julien Fontan; Peter Corke

178

Yellow, Yellow submarin  

NASA Astrophysics Data System (ADS)

The recollections reports on a trip by author to Severodvinsk on the White Sea border (in the Russian Federation), where one of the Buroes and the Soviet atomic submarins Factory was placed. The factory and the buroe is placed there till present. A biography of one of the constructors is given.

Gaina, Alex

2009-12-01

179

Mud Volcanoes Formation And Occurrence  

NASA Astrophysics Data System (ADS)

Mud volcanoes are natural phenomena, which occur throughout the globe. They are found at a greater or lesser scale in Azerbaijan, Turkmenistan, Georgia, on the Kerch and Taman peninsulas, on Sakhalin Island, in West Kuban, Italy, Romania, Iran, Pakistan, India, Burma, China, Japan, Indonesia, Malaysia, New Zealand, Mexico, Colombia, Trinidad and Tobago, Venezuela and Ecuador. Mud volcanoes are most well-developed in Eastern Azerbaijan, where more than 30% of all the volcanoes in the world are concentrated. More than 300 mud volcanoes have already been recognized here onshore or offshore, 220 of which lie within an area of 16,000 km2. Many of these mud volcanoes are particularly large (up to 400 m high). The volcanoes of the South Caspian form permanent or temporary islands, and numerous submarine banks. Many hypotheses have been developed regarding the origin of mud volcanoes. Some of those hypotheses will be examined in the present paper. Model of spontaneous excitation-decompaction (proposed by Ivanov and Guliev, 1988, 2002). It is supposed that one of major factors of the movement of sedimentary masses and formation of hydrocarbon deposits are phase transitions in sedimentary basin. At phase transitions there are abnormal changes of physical and chemical parameters of rocks. Abnormal (high and negative) pressure takes place. This process is called as excitation of the underground environment with periodicity from several tens to several hundreds, or thousand years. The relationship between mud volcanism and the generation of hydrocarbons, particularly methane, is considered to be a critical factor in mud volcano formation. At high flow rates the gas and sediment develops into a pseudo-liquid state and as flow increases the mass reaches the "so-called hover velocity" where mass transport begins. The mass of fluid moves as a quasi-uniform viscous mass through the sediment pile in a piston like manner until expelled from the surface as a "catastrophic eruption". Model of buoyancy drive (by Brown, 1990). Brown's basic hypothesis is similar to Ivanov and Guliev and may be summarized briefly as follows: -in situations where rapid sedimentation is occurring mud may be driven to the surface by buoyancy forces due to bulk density contrasts between mud and overlying sediment cover. Such density contrasts may be simply the result of compaction -disequilibrium, but more importantly may be related to gas expansion when fluids are transported to shallower depths with lower pressure and temperature conditions. Synthetic model had been proposed by I.Lerche, E.Bagirov, I.Guliyev (1997). The model includes the following studies: The starting point of the mud volcanoes begins with the formation of a zone of decompaction as a consequence of a high rate of gas generation. The mud body starts to rise under buoyancy. The excess pressure inside the mud intrusion is less than in surrounding formation. As a result, fluid flow toward the body of mud volcanoes. The body of the mud volcanoes then grows, increasing the buoyancy forces, with further drive the mud. If the rate of gas generation more thôn gas flow, causing exsolving of gas to free-phase gas. If there are open faults and fractures which cross the body of mud volcanoes, then gas and mud can penetrate through the faults, and so from gryphons and salses on the surface. A mud volcanoes can be consider as a huge accumulation of gas, where as the oil is concentrated on the flanks of the mud body.

Guliyev, I. S.

2007-12-01

180

Spreading volcanoes  

USGS Publications Warehouse

As volcanoes grow, they become ever heavier. Unlike mountains exhumed by erosion of rocks that generally were lithified at depth, volcanoes typically are built of poorly consolidated rocks that may be further weakened by hydrothermal alteration. The substrates upon which volcanoes rest, moreover, are often sediments lithified by no more than the weight of the volcanic overburden. It is not surprising, therefore, that volcanic deformation includes-and in the long term is often dominated by-spreading motions that translate subsidence near volcanic summits to outward horizontal displacements around the flanks and peripheries. We review examples of volcanic spreading and go on to derive approximate expressions for the time volcanoes require to deform by spreading on weak substrates. We also demonstrate that shear stresses that drive low-angle thrust faulting from beneath volcanic constructs have maxima at volcanic peripheries, just where such faults are seen to emerge. Finally, we establish a theoretical basis for experimentally derived scalings that delineate volcanoes that spread from those that do not.

Borgia, A.; Delaney, P. T.; Denlinger, R. P.

2000-01-01

181

Versatile Time-Lapse Camera System Developed by the Hawaiian Volcano Observatory for Use at Kilauea Volcano, Hawaii.  

National Technical Information Service (NTIS)

Volcanoes can be difficult to study up close. Because it may be days, weeks, or even years between important events, direct observation is often impractical. In addition, volcanoes are often inaccessible due to their remote location and (or) harsh environ...

R. P. Hoblitt T. R. Orr

2008-01-01

182

Volcano Baseball  

NSDL National Science Digital Library

In this game, learners are volcanoes that must complete several steps to erupt. Starting at home plate, learners draw cards until they have enough points to move to first base. This process repeats for each learner at each base, and each base demonstrates a different process in a volcano's eruption. The first learner to make it back to home plate erupts and is the winner. This is a good introduction to volcanoes. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Smart Attack game after they've completed several activities.

Science, American A.

2009-01-01

183

Up-Close Fluid Sampling at a Deep Submarine Lava Eruption  

NASA Astrophysics Data System (ADS)

On three separate expeditions from April 2004 to April 2006 to the Mariana volcanic arc, we found eruptive activity at NW Rota 1 submarine volcano. ROVs ROPOS, Hyper Dolphin, and Jason-2 were used to survey and collect samples. The summit of the volcano is at 520 meters depth and there are numerous sites of hydrothermal activity around the east-west trending summit ridge and down the south flank. The chemical composition of vent fluids on NW Rota and the microbiological communities entrained by the fluids varies significantly according to location. There is an eruptive pit crater on the south flank about 30 meters below the summit where seawater interacts directly with erupting lava, volcanic gases and molten sulfur. On every visit, the pit has exhibited extreme variability in output, ranging from a very quiet stream of particulate sulfur smoke to violent bursts of smoke, gas bubbles, molten sulfur, highly vesicular volcaniclastic lapilli and small lava bombs. We were able to sample many hydrothermal vents around the volcano and many phases of the output at the eruptive pit. In 2004, we sampled by lowering ROPOS directly into the pit during a quiet period, and subsequently used a long sampling tube to access the pit. In 2006, the wall of the pit was absent and the volcanic vent was directly visible. During this period we were able to sample directly over the surface of slowly erupting lava. The fluid and particle samples obtained were unlike anything ever sampled in the deep sea and appear to be the result of rapid reaction of seawater with volcanic products.

Butterfield, D. A.; Embley, R. W.; Chadwick, W. W.; Lupton, J. E.; Nakamura, K.; Takano, B.; de Ronde, C.; Resing, J.; Bolton, S.; Baross, J.

2006-12-01

184

Regularly spaced submarine rhyolitic-calderas on the Tokara volcanic ridge, northern Ryukyu arc, Japan  

NASA Astrophysics Data System (ADS)

The southern part of the Kyushu Island where is the northern end of the 1300 km long Ryukyu arc, has some huge calderas, Aira and Kikai calderas. These calderas are considered to be formed by the Quaternary super-eruptions. Submarine calderas, Kuchinoshima,Takarashima and Amami calderas, which are of the same size as the Aira caldera,on the Tokara volcanic ridge that is the southern extension of the Kyushu Island, have been proposed on the basis of the bathymetric data. To confirm whether the caldera-like topographic expressions are of volcanic or tectonic in origin, we carried out approximately 70 dredge samplings during six ocean research cruises (KT00-15, KT07-2, KT07-21, NAG252, NAG267, and NAG274). Collected rock samples both from the on-land and seafloor of the Tokara Islands were compared to define the genetic correlations. The weathering condition of the volcanic rocks in the Tokara Islands is different from the main land of Japan due to its hot and humid subtropical weather. Therefore, some samples are probably highly ferrallitizated by the weather condition. Indeed volcanic rocks with high loss on ignition value are relatively poorer in K2O and SiO2 and richer in Al2O3, Fe2O3, TiO2 compared with the low LOI value rocks. The LOI values could be an available threshold for excluding unreliable sample data. Each volcano shows individual trend on the K2O vs. SiO2 diagram. We revealed that there is obvious regional variation in their magma chemistry. Not only dense rocks but also highly vesiculated rhyolite samples collected from the seafloor are plotted on the same volcanic trends. The volcanic rocks recovered from the seafloor predominate in acidic rocks, rhyolite and dacite, rather than andesite. The rhyolitic pumice that are highly calcified by biological activity, were also found on the submarine plateaus that are located around the edge of submarine calderas at about 200 m depth. These samples imply that the submarine plateaus are not simply erosional remnant, but a product of caldera forming eruptions. The other submarine acidic rocks preserve fresh volcanic glass and are considered to be young. The measured K-Ar ages for the two representative acidic rocks, porphyritic rhyolite and aphyric dacite are young (0.6 Ma and < 0.20 Ma). Therefore, the rhyolitic volcanism could be active on the present submarine volcanic front of the Tokara volcanic ridge. Our investigations support the idea that the submarine caldera-like topographies were produced by the Quaternary super-eruptions. If this is valid, the five huge calderas, including well studied Aira and Kikai calderas, align regularly at approximately 100 km interval from the southern Kyushu Island to the central part of the Ryukyu arc.

Yokose, H.; Sato, H.; Fujimoto, Y.; Mirabueno, M.; Kobayashi, T.; Akimoto, K.; Yoshimura, H.; Morii, Y.; Yamawaki, N.

2009-04-01

185

Volcano survey  

Microsoft Academic Search

SummaryA short review is made of the main means of investigation of eruption forecast, used in the few existing, accurately staffed volcanological observatories as well as during sporadic expeditions on active volcanoes, together with non-exhaustive data obtained during recent years (volcanoseismology, gravimetry, tiltmetry, geodetic measurements, magnetic and aeromagnetic surveys, chemistry of gas, waters and sublimates, geochemistry). Details of research performed

H. Tazieff

1966-01-01

186

A new species of Copepoda Harpacticoida, Xylora calyptogenae spec. n., with a carnivorous life-style from a hydrothermally active submarine volcano in the New Ireland Fore-Arc system (Papua New Guinea) with notes on the systematics of the Donsiellinae Lang, 1948  

NASA Astrophysics Data System (ADS)

A new species of harpacticoid copepods, Xylora calyptogenae spec. n., from Edison Seamount, a hydrothermally active submarine volcano in the New Ireland Fore-Arc system (Papua New Guinea) is described. The new species belongs to the Donsiellinae Lang, 1944, a highly specialised taxon, the members of which have previously been encountered only in association with decaying wood and/or wood-boring isopods. A closer relationship of the Donsiellinae with the Pseudotachidiidae Lang, 1936, can be stated on the basis of characteristics concerning the setation and/or segmentation of A1, A2, Mxl, Mxp, the shape of the female P5, anal somite, sexual dimorphisms on P2 and P3 and missing caudal seta I. Within the Pseudotachidiidae, the Donsiellinae again can be well characterized, e.g. by the setation and segmentation of A2, Mxl, swimming-legs, the shape of P1, female P5, male P2, sexual dimorphism and male P5. The Donsiellinae share some apomorphies with the pseudotachidiid subtaxon Paranannopinae Por, 1986: setation/segmentation of Mx, P1, A1. X. calyptogenae spec. n. is more closely related to Xylora bathyalis Hicks 1988 living in the deep sea wood substrata in New Zealand waters. Some traits of the evolutionary history of the Donsiellinae become evident, probably starting from the more primitive deep sea taxa X .calyptogenae spec. n., which lives in the hydrothermal seafloor in the absence of decaying wood, and X. bathyalis, which is found in decaying wood but not necessarily associated with the wood-boring isopod Limnoria Leach, 1814, towards the more advanced genera such as Donsiella Stephensen, 1936, which invades shallow waters and, further, clings to Limnoria, forming a close and, for the copepod, probably obligatory association. The specialised mouthparts of X. calyptogenae spec. n. seem to facilitate the grabbing and fixing of larger and/or active food items. This is confirmed by the presence of a large prey organism, presumably a copepod, consumed either alive or dead, in the gut of one of the available specimens. This morphology of the mouthparts is also shared by the closely related X. bathyalis.

Willen, Elke

2006-12-01

187

Magma plumbing system of the 2000 eruption of Miyakejima Volcano, Japan  

Microsoft Academic Search

During the 2000 eruption at Miyakejima Volcano, two magmas with different compositions erupted successively from different craters. Magma erupted as spatter from the submarine craters on 27 June is aphyric basaltic andesite (2), whereas magma issued as volcanic bombs from the summit caldera on 18 August is plagioclase-phyric basalt (20 vol% phenocrysts, 50.8–51.3 wt% SiO2). The submarine spatter contains two types of

Mizuho Amma-Miyasaka; Mitsuhiro Nakagawa; Setsuya Nakada

2005-01-01

188

Ongoing inflation and magma accumulation of Grimsvotn subglacial volcano, Iceland  

Microsoft Academic Search

The sub-glacial Grimsvotn volcano, one of Iceland's most active volcanoes, erupted in 1983, 1998 and 2004. Since 1998, annual GPS measurements have been conducted at the only available nunatak at the volcano, located on the rim of its caldera. A clear pattern of deformation is observed that can be attributed to magma inflow and outflow, uplift due to glacial thinning,

E. C. Sturkell; F. Sigmundsson; P. Einarsson; F. Jouanne; H. Geirsson; B. G. Ofeigsson; T. Villemin; F. Palsson

2008-01-01

189

Submarine landslides in Spitsbergen fjords  

NASA Astrophysics Data System (ADS)

Fjords are areas that can be exposed to repeated submarine mass wasting, and more than 50% of the depositional sequences can be reworked occasionally. The largest and most frequent slope failures occur typically in relation to the advance and retreat of grounded ice. However, also areas not directly affected by ice can be exposed to slope failure. We provide an overview of mass-transport deposits (MTDs) from the Isfjorden fjord system, the largest fjord system on Spitsbergen. We discuss pre-conditioning factors, trigger mechanisms and the potential of MTDs as indicators for the activity of tidewater and terrestrial glaciers. Slides, slumps, debris-flow deposits and turbidites have been observed. We distinguish three 'types' of MTDs: 1) 'Glacigenic MTDs', including muddy debris-flow lobes, as well as thin sandy MTDs deposited in front of or beneath glaciers; 2) 'Fluvial MTDs', including sandy turbidites and other MTDs originating from slope failures beyond river mouths; 3) 'Other MTDs', i.e. deposits related to failures on slopes that are neither supplied with sediments from glaciers nor from rivers. Such deposits include sediment lobes (debris flows or slumps) and slides. The available data indicate that mass wasting in the Isfjorden area commenced shortly after the deglaciation of the mouth of the trunk fjord around 14,100 cal. years BP. The most frequent pre-conditioning factors and trigger mechanisms are probably high sediment supply and earthquakes related to isostatic adjustments. However, marked changes in the slope gradient (related to bedrock or moraine ridges) also affect the stability of the fronts of tidewater glaciers and the positions of grounding lines, thus influencing the locations of sediment sources and, in consequence, the distribution of glacigenic MTDs. In addition to providing information about the dynamics of marine-terminating glaciers, submarine MTDs occasionally also provide information about the dynamics of terrestrial glaciers during the Holocene.

Forwick, M.; Vorren, T. O.

2012-04-01

190

Petrology of deep drill hole, Kilauea Volcano  

Microsoft Academic Search

The first deep drill hole (1262 m TD) at the summit of an active volcano (1102 m elev) was drilled in 1973 at Kilauea volcano, Hawaii with support from NSF and USGS. The hole is located within southern margin of Kilauea caldera in northern part of a 15 km² triangular block bounded by east rift zone, Koae fault zone, and

L. T. Grose; G. V. Keller

1976-01-01

191

Variations of the state of stress and dike propagation at Fernandina volcano, Galápagos.  

NASA Astrophysics Data System (ADS)

Fernandina volcano forms the youngest and westernmost island of the Galapagos Archipelago, a group of volcanic islands located near the equator and 1000 km west of Ecuador. Twenty-five eruptions in the last two hundred years make Fernandina the most active volcano in the archipelago and one of the most active volcanoes in the world. Most eruptions occur along fissures fed by dikes that propagate from the central magmatic system and from reservoirs centered under the summit caldera. Eruptive fissures in the subaerial portion of the volcano form two distinct sets: (1) arcuate or circumferential fissures characterize the upper portion of the volcano around the caldera while (2) radial fissures are present on the lower flanks. The subaerial portion of the volcano lacks of well-developed rift zones, while the submarine part of Fernandina shows three rifting zones that extend from the western side of the island. Using Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface displacement at Fernandina acquired from 1992 to 2010, and in particular the ones spanning the last three eruptions (1995 - radial, 2005 - circumferential and 2009 - radial) we infer the geometry of the shallow magmatic system and of the dikes that fed these eruptions. A shallow dipping radial dike on the southwestern flank has been inferred by Jónnson et al. (1999) for the 1995 eruption. This event shows a pattern of deformation strikingly similar to the one associated with the April 2009 eruption for which we infer a similar geometry. Co-eruptive deformation for the 2005 event has been modeled by Chadwick et al. (2010) using three planar dikes, connected along hinge lines, in the attempt to simulate a curve-concave shell, steeply dipping toward the caldera at the surface and more gently dipping at depth. Dike propagation in a volcano is not a random process but it is controlled by the orientation of the principal stresses, with the dike orthogonal to the least compressive stress. We calculate stress changes within the volcanic edifice generated by the active geophysical processes (e.g., pressure changes in reservoir, dike emplacement, …) and we investigate what phenomena can produce a stress field compatible with the inferred dike geometries and the observed pattern of eruptive fissures. Stress models are generated in a three-dimensional linear elastic medium, using a 3D boundary element code based on the analytical solutions for triangular dislocations in isotropic elastic half and full space.

Bagnardi, M.; Amelung, F.

2012-04-01

192

Detection of landsides in shield volcanoes from magnetic logging - an example from Mauna Kea/Hawaii  

NASA Astrophysics Data System (ADS)

A quasi-continuous magnetic log has been obtained in the Hawaii Scientific Drilling Project 2 (HSDP-2), providing information down to 1800 mbsl of Mauna Kea volcano flank deposits. The HSDP borehole penetrates series of Aa- and Pahoehoe subaerial lava flows down to 1100 mbsl followed by submarine series of volcniclastics with intercalated massive flows. The borehole magnetometer was employed to measure the horizontal and vertical magnetic fields. Measurements were taken in downhole and uphole runs, with a good correlation between both runs.. Magnetic borehole logging in the HSDP-2 hole reveals strong magnetic anomalies in the subaerial as well in the submarine part with deviations from the normal field of up to 15000 nT. Mean inclination calculated from logging data is 22.7 °, which differs significantly from the present day inclination of 36.7° (IGRF95 reference field). The frequency distribution of inclination estimated for different rock types is clearly shifted towards lower values for rocks of the submarine part of the hole. In this lower part a decrease of magnetic inclination is observed which changes abruptly. These deviations of up to 20° are hardly explained by secular variation of the magnetic main field. Also flexural deformation of the oceanic crust by the load of the Hawaiian Island yields tilt angles, which are too small to explain the observed deviations. On the other hand mass movements, e.g. landslides and debris avalanches are well known processes, which modify the morphology of shield volcanoes during their lifetime. The interpretation of petrophysical logging data from the submarine part of HSDP-II provides strong indications for landslides during the stage of seacliff formation. Core and petrophysical logging data indicate larger mass movements between 1570 and 1670 mbsl. Here, a prominent boundary is located where petrophysical characteristics abruptly change. The boundary marks a significant decrease in rock porosity within the hyaloclastites accompanied by a strong temperature increase below this boundary. This boundary correlates well with an abrupt change in magnetic inclination to lower values.

Pechnig, R.; Stoll, J.; Steveling, E.; Buysch, A.

2003-04-01

193

CBO Testimony: Attack Submarine Programs.  

National Technical Information Service (NTIS)

Attack submarine programs are a significant portion of the Navy's overall acquisition plan: in its 1996 request, the Administration has allocated $2.8 billion for them. That sum includes $1,507 million to complete the funding for a third Seawolf submarine...

C. Williams

1995-01-01

194

Current submarine atmosphere control technology.  

PubMed

Air purification in submarines was introduced towards the end of World War II and was limited to the use of soda lime for the removal of carbon dioxide and oxygen candles for the regeneration of oxygen. The next major advances came with the advent of nuclear-powered submarines. These included the development of regenerative and, sometimes, energy-intensive processes for comprehensive atmosphere revitalization. With the present development of conventional submarines using air-independent propulsion there is a requirement for air purification similar to that of the nuclear-powered submarines but it is constrained by limited power and space. Some progress has been made in the development of new technology and the adoption of air purification equipment used in the nuclear-powered submarines for this application. PMID:11876194

Mazurek, W

1998-01-01

195

A study of methods of characterising the effects of internal noise sources on submarine flank arrays  

Microsoft Academic Search

Passive sonar arrays are used on submarines and surface vessels to detect the presence and position of other ships in the vicinity and locate and identify potential targets. Noise generated by the machinery inside the submarine carrying the array can affect the capacity to detect other vessels. The aim of this work was to develop methods of characterising the effects

Y. Gargouri; V. Nautet; P. R. Wagstaff; C. Giangreco

1998-01-01

196

Shrimp Populations on Northwest Rota, an Active Volcano of the Mariana Volcanic Arc  

NASA Astrophysics Data System (ADS)

NW Rota-1 is a submarine volcano that manifested active volcanic and hydrothermal activity during submersible surveys in March 2004 (see Embley et al.). Substratum on the volcano summit (520 m depth) was entirely basalt outcrop or variously-sized ejecta lying near the angle of repose. While no fauna inhabited the rim of the volcanic pit, patches of shrimp were located within 25 m and on the nearby summit. Two species are present. Opaepele cf. loihi shows few morphological differences from either a nearby population on Eifuku Volcano (see Chadwick et al.) at 1700 m depth or from the type locality in Hawaii. A molecular comparison of COI sequences of 13 specimens found little difference from two Hawaiian sequences. Video observations detail frequent feeding activity using spatulate chelipeds to trim microbial filaments as the cephalothorax sways across the substratum. The second species is an undescribed Alvinocaris. Juveniles of this species appear to form clusters distinct from Opaepele where they also graze on filaments. Sparse adults of Alvinocaris range up to 5.5 cm long and display aggressive behaviour moving through patches of smaller shrimp. Densities of Opaepele were highest on sloping rock walls (over 500 per sq.m.) whereas adult Alvinocaris were more abundant on rubble. This division may reflect food preference: microbial filaments versus polychaetes and meiofauna. Characterization of particulates from these substrata was conducted using visual sorting and stable isotope composition. As Alvinocaris matures, the chelipeds enlarge, enabling a greater predatory capacity. Measurements of Opaepele from digital in situ images reveal a population structure suggesting a recent recruitment. Average size is significantly smaller than the Eifuku population and no egg-bearing females were collected. The disjunct range of this species where it occurs on active volcanoes 6000 km apart is puzzling. Further work on intermediate sites and into the reproductive strategy of the species is required.

Tunnicliffe, V.; Juniper, S. K.; Limén, H.; Jones, W. J.; Vrijenhoek, R.; Webber, R.; Eerkes-Medrano, D.

2004-12-01

197

Observations of Local Seismicity and Harmonic Tremor Using an Ocean Bottom Hydrophone Array at Brothers Volcano, South Kermadec Arc.  

NASA Astrophysics Data System (ADS)

The submarine Brothers volcano is an important link in the volcanic chain of the southern Kermadec Arc system in the Southwest Pacific Ocean north of New Zealand. The 3-3.5 km wide caldera has a center depth of 1850m and steep surrounding walls of 300-450m. Active hydrothermal venting distinguished Brothers as a point of focus for the New Zealand American Submarine Ring of Fire (NZASRoF) expeditions in 2004 and 2005. Due to its remote location, moderate to small magnitude seismicity around the Brothers area is largely unknown. In late September 2004, four ocean bottom hydrophones (OBHs) were deployed on the caldera floor. In April 2005, three of the four instruments were recovered intact. These three OBHs continuously recorded, for seven months, the low frequency (0-110Hz) acoustic field around Brothers volcano, in particular seismic P- and S-waves propagating through the crust and acoustic T-waves in the water column . Preliminary analysis reveals seismicity rates on the order of 106 earthquakes per month. In addition to seismic arrivals, low frequency harmonic tremor is frequently and independently observed on each of the OBH instruments, often occurring subsequent to the larger seismic events. Qualitative comparisons of these signals with tremor observed from the Volcano Islands south of Japan (Dziak and Fox, 2002) show them to be nearly equivalent in frequency structure, suggesting the origin of the tremor observed at Brothers may also be attributed to resonance of a magma-gas mixture in a large chamber or conduit near the water/ seafloor boundary.

Haxel, J. H.; Dziak, R. P.; Lau, T. K.; Matsumoto, H.

2005-12-01

198

Volcano Explorer: Build A Virtual Volcano  

NSDL National Science Digital Library

This website allows you to build virtual volcanoes and model their eruptions by changing gas and viscosity levels. Interactive screens define vocabulary and explain volcanic activity of three common volcano categories.

199

A Volcano Population Index for Estimating Relative Risk With Example Data From Central America  

Microsoft Academic Search

We have developed a Volcano Population Index (VPI) to make objective comparisons among individual volcanoes of populations that may be subject to volcanic hazards. We used volcano location data from the Smithsonian's Global Volcanism Program (GVP) with the LandScan 2001 gridded global population data base from the Oak Ridge National Laboratory to evaluate population distribution near potentially active volcanoes in

J. W. Ewert; C. J. Harpel

2003-01-01

200

Methane and sulfide fluxes in permanent anoxia: In situ studies at the Dvurechenskii mud volcano (Sorokin Trough, Black Sea)  

NASA Astrophysics Data System (ADS)

The Dvurechenskii mud volcano (DMV) is located in permanently anoxic waters at 2060 m depth (Sorokin Trough, Black Sea). The DMV was studied during the RV Meteor expedition M72/2 as an example of an active mud volcano system, to investigate the significance of submarine mud volcanism for the methane and sulfide budget of the anoxic Black Sea hydrosphere. Our studies included benthic fluxes of methane and sulfide, as well as the factors controlling transport, consumption and production of both compounds within the sediment. The pie-shaped mud volcano showed temperature anomalies as well as solute and gas fluxes indicating high fluid flow at its summit north of the geographical center. The anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) was repressed in this zone due to the upward flow of sulfate-depleted fluids through recently deposited subsurface muds, apparently limiting microbial methanotrophic activity. Consequently, the emission of dissolved methane into the water column was high, with an estimated rate of 0.46 mol m -2 d -1. On the wide plateau and edge of the mud volcano surrounding the summit, fluid flow and total methane flux were lower, allowing higher SR and AOM rates correlated with an increase in sulfate penetration into the sediment. Here, between 50% and 70% of the methane flux (0.07-0.1 mol m -2 d -1) was consumed within the upper 10 cm of the sediment. The overall amount of dissolved methane released from the entire mud volcano structure into the water column was significant with a discharge of 1.3 × 10 7 mol yr -1. The DMV maintains also high areal rates of methane-fueled sulfide production and emission of on average 0.05 mol m -2 d -1. This is a difference to mud volcanoes in oxic waters, which emit similar amounts of methane, but not sulfide. However, based on a comparison of this and other mud volcanoes of the Black Sea, we conclude that sulfide and methane emission into the hydrosphere from deep-water mud volcanoes does not significantly contribute to the sulfide and methane inventory of the Black Sea.

Lichtschlag, Anna; Felden, Janine; Wenzhöfer, Frank; Schubotz, Florence; Ertefai, Tobias F.; Boetius, Antje; de Beer, Dirk

2010-09-01

201

Massive edifice failure at Aleutian arc volcanoes  

NASA Astrophysics Data System (ADS)

Along the 450-km-long stretch of the Aleutian volcanic arc from Great Sitkin to Kiska Islands, edifice failure and submarine debris-avalanche deposition have occurred at seven of ten Quaternary volcanic centers. Reconnaissance geologic studies have identified subaerial evidence for large-scale prehistoric collapse events at five of the centers (Great Sitkin, Kanaga, Tanaga, Gareloi, and Segula). Side-scan sonar data collected in the 1980s by GLORIA surveys reveal a hummocky seafloor fabric north of several islands, notably Great Sitkin, Kanaga, Bobrof, Gareloi, Segula, and Kiska, suggestive of landslide debris. Simrad EM300 multibeam sonar data, acquired in 2005, show that these areas consist of discrete large blocks strewn across the seafloor, supporting the landslide interpretation from the GLORIA data. A debris-avalanche deposit north of Kiska Island (177.6° E, 52.1° N) was fully mapped by EM300 multibeam revealing a hummocky surface that extends 40 km from the north flank of the volcano and covers an area of ˜ 380 km 2. A 24-channel seismic reflection profile across the longitudinal axis of the deposit reveals a several hundred-meter-thick chaotic unit that appears to have incised into well-bedded sediment, with only a few tens of meters of surface relief. Edifice failures include thin-skinned, narrow, Stromboli-style collapse as well as Bezymianny-style collapse accompanied by an explosive eruption, but many of the events appear to have been deep-seated, removing much of an edifice and depositing huge amounts of debris on the sea floor. Based on the absence of large pyroclastic sheets on the islands, this latter type of collapse was not accompanied by large eruptions, and may have been driven by gravity failure instead of magmatic injection. Young volcanoes in the central and western portions of the arc (177° E to 175° W) are located atop the northern edge of the ˜ 4000-m-high Aleutian ridge. The position of the Quaternary stratocones relative to the edge of the Aleutian ridge appears to strongly control their likelihood for, and direction of, past collapse. The ridge's steep drop to the north greatly increases potential runout length for slides that originate at the island chain.

Coombs, Michelle L.; White, Scott M.; Scholl, David W.

2007-04-01

202

Volcano Lovers  

NSDL National Science Digital Library

This Why Files article explores volcanoes and volcanic eruptions. Topics covered include: Alaska's Pavlof and its threat to jet engines; Mexico City's restless neighbor, Popocatepetl (El Popo); underground volcanic processes; modern forecasting of eruptions; various volcanic phenomena and features; large flood basalt areas around the world; California's volcanically active area, Long Valley Caldera and Mammoth Mountain; Indonesia's Krakatau eruption in 1883, which was the world's largest historical eruption; Krakatau's ecological contribution to the study of colonization of sterile lands; and central Mexico's Paricutin which was witnessed emerging from a farmer's field in 1943. Three scientists were interviewed for this article.

Tenenbaum, David

1997-01-02

203

The Electronic Volcano  

NSDL National Science Digital Library

The Electronic Volcano offers links to many types of information on active volcanoes, such as maps, photographs, full texts of dissertations and a few elusive documents. The Electronic Volcano will guide you to resources in libraries or resources on other information servers including catalogs of active volcanoes, datasets for literature citations, electronic and hard-copy journals, visual information, maps, observatories and institutions, and a volcano name and country index.

204

Earth Layers and Volcanoes  

NSDL National Science Digital Library

Why do we have volcanoes? Use the information on the websites to answer the questions on the worksheet. Worksheet First, review the layers of the earth. Labeling the layers game Next, go through the maze and read the information given. Magic School Bus volcano game Now, study the different shapes of volcanoes. Click enter, then volcano types in the menu. Read about the 3 types of volcanoes. Discovery Kids Games Finally, watch ...

Brookeshallow

2011-04-13

205

Surfing for Earthquakes and Volcanoes  

NSDL National Science Digital Library

This resource is part of the Science Education Gateway (SEGway) project, funded by NASA, which is a national consortium of scientists, museums, and educators working together to bring the latest science to students, teachers, and the general public. In this lesson, students use the Internet to research data on earthquakes and volcanoes and plot locations to determine plate boundaries. Extensions include interpretation of interaction between plate boundaries, causes of earthquakes and volcanoes, and the comparison of the formation of Olympus Mons on Mars and the Hawaiian volcanic chain. There are worksheets, references, assessment ideas, and vocabulary available for educators.

Coe, Patty; Merrick, Michael

206

Next Generation Strategic Submarine Navigator.  

National Technical Information Service (NTIS)

For the last forty-five years, Strategic Systems Programs (SSP) has been entrusted with total life cycle responsibility for the United States and the Royal (United Kingdom) Navy's Strategic Submarine (SSBN) launched ballistic missile weapons systems. SSP'...

M. J. Ringlein N. J. Barnett M. B. May

2000-01-01

207

Submarine Periscope Eyeguard Housing Assembly.  

National Technical Information Service (NTIS)

A submarine periscope eyeguard housing assembly includes a viewing lens housing having a viewing lens aperture and viewing lens therein, first and second arm members fixed to the viewing lens housing and extending therefrom, a first blinder mounted on the...

W. C. Maciejewski R. Sayegh

2001-01-01

208

A Magma Genesis Model to Explain Growth History of Hawaiian Volcanoes: Perspectives of 2001-2002 JAMSTEC Hawaii Cruises  

Microsoft Academic Search

The 2001 and 2002 JAMSTEC Hawaii cruises have been carried out using RV-Kairei with ROV-Kaiko and RV-Yokosuka with submersible Shinaki-6500, respectively. The main focus of these cruises is 1) to clarify the growth history of Hawaiian volcanoes through geological study on deep submarine exposures, 2) to understand the nature of submarine rifts, 3) to understand the nature of magmas erupted

E. Takahashi

2003-01-01

209

Observations of Local Seismicity and Harmonic Tremor Using an Ocean Bottom Hydrophone Array at Brothers Volcano, South Kermadec Arc  

Microsoft Academic Search

The submarine Brothers volcano is an important link in the volcanic chain of the southern Kermadec Arc system in the Southwest Pacific Ocean north of New Zealand. The 3-3.5 km wide caldera has a center depth of 1850m and steep surrounding walls of 300-450m. Active hydrothermal venting distinguished Brothers as a point of focus for the New Zealand American Submarine

J. H. Haxel; R. P. Dziak; T. K. Lau; H. Matsumoto

2005-01-01

210

Detection of landsides in shield volcanoes from magnetic logging - an example from Mauna Kea\\/Hawaii  

Microsoft Academic Search

A quasi-continuous magnetic log has been obtained in the Hawaii Scientific Drilling Project 2 (HSDP-2), providing information down to 1800 mbsl of Mauna Kea volcano flank deposits. The HSDP borehole penetrates series of Aa- and Pahoehoe subaerial lava flows down to 1100 mbsl followed by submarine series of volcniclastics with intercalated massive flows. The borehole magnetometer was employed to measure

R. Pechnig; J. Stoll; E. Steveling; A. Buysch

2003-01-01

211

Magma plumbing system of 2000 eruption of Miyakejima volcano, Izu-Mariana arc, Japan  

Microsoft Academic Search

The 2000 Miyakejima eruption has been very unique among 13 historic eruptions since 1469 A.D, and its activity has continued now. The activity had been detected as westward migration of the magma since June 26, part of which erupted from submarine craters at the western flank of the volcano on the next day. After that, eruption has continued at the

M. Miyasaka-Amma; M. Nakagawa; S. Nakada

2001-01-01

212

Developing monitoring capability of a volcano observatory: the example of the Vanuatu Geohazards Observatory  

Microsoft Academic Search

Vanuatu lies on the Pacific 'Ring of Fire'. With 6 active subaerial and 3 submarine (identified so far) volcanoes, monitoring and following up their activities is a considerable work for a national observatory. The Vanuatu Geohazards Observatory is a good example of what can be done from `scratch' to develop a volcanic monitoring capability in a short space of time.

S. Todman; E. Garaebiti; G. E. Jolly; S. Sherburn; B. Scott; A. D. Jolly; N. Fournier; C. A. Miller

2010-01-01

213

Hawaii Volcanoes and Volcanics - Maps and Graphics, etc.  

NSDL National Science Digital Library

This page provides maps, "pictograms", photographs, and graphics of the Hawaiian volcanoes. Maps include volcano locations in the Hawaiian Island chain, Hawaii Island, and Maui, and a global map of the 16 Decade Volcanoes, which include Mauna Loa. Photographs or "pictograms" demonstrate a shield volcano versus a composite volcano (Mauna Loa versus Mount Rainier, Washington) and Hawaiian-Style Eruptions vs. Cascades-Style Eruptions - Pu'u O'o, Hawaii vs. Mount St. Helens, Washington. The graphic shows the profile of Mauna Loa and Kilauea versus Mount Rainier.

214

Super Volcano  

NSDL National Science Digital Library

Deep beneath the surface of Earth lies one of the most destructive and yet least understood of the natural forces on the planet: the super volcano. This radio broadcast presents discussions with scientists at Yellowstone National Park who are investigating this potentially devastating natural phenomenon. Yellowstone National Park is one of the largest supervolcanoes in the world. It last erupted 640,000 years ago and scientists are now predicting that the next eruption may not be far off. To discover more, a new volcanic observatory has been built in the park to monitor the extreme volcanic activity going on beneath the surface of this much visited destination. The broadcast is 30 minutes in length.

215

OTEC submarine cable environmental characteristics and hazards analysis  

Microsoft Academic Search

This analysis focuses on submarine cable protection criteria and technology as applied to four potential OTEC plants and cable routes at Hawaii, Puerto Rico, Guam and Florida. The environmental characteristics are presented for each site as follows: (a) natural factors, such as location, tides, currents, wind, waves, bottom soil type, seafloor movement, and (b) man-made factors, such as ship traffic,

C. Chern; W. Tudor

1982-01-01

216

33 CFR 209.310 - Representation of submarine cables and pipelines on nautical charts.  

Code of Federal Regulations, 2013 CFR

...charts published by the Corps of Engineers is as follows: (1) Within protected waters such as harbors, rivers, bays, estuaries or other inland waterways the location of submarine cables and pipelines is to be indicated by shaded areas marked...

2013-07-01

217

Types of Volcanoes  

NSDL National Science Digital Library

This volcano resource introduces the six-type classification system and points out weaknesses of the classic three-type system. The six types of volcanoes are shield volcanoes, strato volcanoes, rhyolite caldera complexes, monogenetic fields, flood basalts, and mid-ocean ridges. For each type of volcano there is a description of both structure and dynamics along with examples of each. You can account for more than ninty percent of all volcanoes with these six types. Additionally, any system will be more useful if you use modifiers from the other potential classification schemes with the morphological types.

218

Lavas from Active Boninite and Very Recent Basalt Eruptions at Two Submarine NE Lau Basin Sites  

NASA Astrophysics Data System (ADS)

Very young submarine lava flows were discovered at two sites in the NE Lau Basin during a May 2009 NSF-NOAA expedition. The multidisciplinary rapid response expedition was organized to investigate these sites based on chemical and physical water column signatures observed during a NOAA-led regional study in Nov. 2008. An active eruption was discovered and observed for 5 days in May 2009 at W. Mata volcano, just behind the northernmost segment of the Tofua arc. The ongoing eruption produced extrusive and pyroclastic deposits from multiple vents near the 1200m depth summit of the volcano. Lavas were sampled from the summit and volcano flanks using the ROV Jason II. The samples indicate that W. Mata is currently erupting orthopyroxene-clinopyroxene-olivine porphyritic boninite magmas, which is also the predominant rock composition elsewhere on the seamount. The youngest lavas are very fresh, highly vesicular (up to ~30%) and occur as predominantly pillow and lobate forms, sometimes mantled by very young pyroclastic deposits and/or thin chemical coatings of presumed microbial and/or inorganic origin. The coatings and pyroclast apron make it difficult to map the extent of the youngest deposits by visual indicators alone, so we are currently dating 7 well-distributed samples from the W. Mata summit by 210Po-210Pb chronology. Very preliminary age results indicate that samples collected near the active vents are <1 month old, although samples collected further afield erupted sometime between early 2009 and Fall 2008, implying either that active vents have migrated or that lavas flowed farther from the vents in earlier eruptive phases. Extremely fresh but no longer active lava flows were also discovered along 2 km of the NE Lau Spreading Center axis, at 1600m water depth. The highly vesicular and sparsely phyric basalts occur as a series of high effusion rate sheets and lobates at vent-proximal sites along the ridge axis, transitional to pillows in distal locations. Very preliminary 210Po-210Pb data on 5 NELSC lavas suggest the eruption occurred over at least a few months, with significant chemical heterogeneity (e.g., ~1 wt% MgO variation), and with highly enriched compositions (e.g., Th=3.3 ppm, Th/U >3.8). 210Po activity in 3 samples suggest a Nov 2008 eruption, consistent with interpretations from water column physical and chemical characteristics measured in Nov. 2008. 210Po in 2 other lavas suggest early 2009 and mid 2008 eruptions, respectively. Some young lavas at both volcanoes had native sulfur deposits on or within them, which has not been observed at recent submarine eruption sites on mid-ocean ridges or Loihi, but has been seen at NW Rota seamount (Mariana arc). Our goal is to define the age, duration, composition and magnitude of both NE Lau eruptions to help quantify magmatic, hydrothermal, and ecological impacts and geochemical signatures of interest to the US Ridge2000 and Margins programs, which partially supported the NE Lau response expedition. Geochemical characterization of samples is ongoing with shore-based collaborators.

Rubin, K. H.; Embley, R. W.; Clague, D. A.; Resing, J. A.; Michael, P. J.; Keller, N. S.; Baker, E. T.

2009-12-01

219

Absolute and relative locations of earthquakes at Mount St. Helens, Washington, using continuous data: implications for magmatic processes: Chapter 4 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006  

USGS Publications Warehouse

This study uses a combination of absolute and relative locations from earthquake multiplets to investigate the seismicity associated with the eruptive sequence at Mount St. Helens between September 23, 2004, and November 20, 2004. Multiplets, a prominent feature of seismicity during this time period, occurred as volcano-tectonic, hybrid, and low-frequency earthquakes spanning a large range of magnitudes and lifespans. Absolute locations were improved through the use of a new one-dimensional velocity model with excellent shallow constraints on P-wave velocities. We used jackknife tests to minimize possible biases in absolute and relative locations resulting from station outages and changing station configurations. In this paper, we show that earthquake hypocenters shallowed before the October 1 explosion along a north-dipping structure under the 1980-86 dome. Relative relocations of multiplets during the initial seismic unrest and ensuing eruption showed rather small source volumes before the October 1 explosion and larger tabular source volumes after October 5. All multiplets possess absolute locations very close to each other. However, the highly dissimilar waveforms displayed by each of the multiplets analyzed suggest that different sources and mechanisms were present within a very small source volume. We suggest that multiplets were related to pressurization of the conduit system that produced a stationary source that was highly stable over long time periods. On the basis of their response to explosions occurring in October 2004, earthquakes not associated with multiplets also appeared to be pressure dependent. The pressure source for these earthquakes appeared, however, to be different from the pressure source of the multiplets.

Thelen, Weston A.; Crosson, Robert S.; Creager, Kenneth C.

2008-01-01

220

Experiments on Submarine Knickpoints  

NASA Astrophysics Data System (ADS)

The results of a laboratory study on the upstream migration of submarine knickpoints are presented. The main goal of this research was to obtain the formation of these features at laboratory scale. In order to achieve the objective, eight experiments using different materials were conducted in a flume at the Saint Anthony Falls Laboratory, University of Minnesota. The sediment used in these experiments was: kaolin clay, silica flour and fine sand. Silica flour and fine sand were used as single sediment in four experiments. The other four experiments consisted of a combination of the previous materials. The total sediment concentration in the experiments was 5% (one experiment) and 10% (seven experiments) by volume. The discharge ranged from 0.011 to 0.055 l/s. The experiment started with an initial slope in the channel bed of 15%. The bed deposit inside the flume was built up as the experiment progressed. Knickpoints were observed in six of the eight experiments. They were formed when one material or a combination of them was used in the tests. Initial calculations on the upstream migration velocity indicate values in the vicinity of 0.5 mm/s.

Toniolo, H.; Cantelli, A.

2004-12-01

221

Optical fiber submarine cable  

SciTech Connect

An optical fiber submarine cable, which is provided with at least one coated optical fiber, a power supplying, pressure resisting layer of a pipe-like configuration, a tension resisting wire layer formed of a conductive material of relatively low conductivity and disposed in close contact with the power supplying, pressure resisting layer of the pipe-like configuration, and an insulator layer disposed around the tension resisting wire layer. The power supplying, pressure resisting layer is formed as at least one inner layer and an outer layer. The inner layer is formed as a single layer or composite layers by forming a tape-like good conductor material into a pipe-like configuration with its joint made a mere butt, or by assembling together a plurality of pressure resisting material segments equally divided in the circumference direction for at least one layer of the inner layer and having housed the above-mentioned at least one coated optical fiber in an optical fiber housing space defined centrally of the inner layer. The outer layer is formed by winding a metal tape on the inner layer.

Nakai, T.; Ejiri, Y.; Furusawa, K.; Niiro, Y.; Nunokawa, M.; Sato, M.

1984-12-25

222

Pavlof Volcano darkens the Alaskan sky  

NASA Astrophysics Data System (ADS)

Pavlof Volcano, historically the most active volcano in the Aleutian volcanic arc and a serious potential threat to aviation safety, began a vigorous strombolian eruption in mid-September. Located 965 km southwest of Anchorage, Pavlof lies beneath the heavily traveled North Pacific jet air routes through which 10,000 passengers fly each day. During its most recent eruption in 1986-1988, an 8-hour explosive event at Pavlof sent ash more than 15 km above sea level and dropped 3 mm of ash on Cold Bay, 60 km southwest of the volcano. A similar, unanticipated explosive eruption today would pose a significant hazard to air traffic in the region.

Neal, Tina

223

Source Signature of Sr Isotopes in Fluids Emitting From Mud volcanoes in Taiwan  

Microsoft Academic Search

Located at the boundary between the Philippine Sea Plate and the Asia Continental Plate, abundance of mud volcanoes were erupted on land in Taiwan. According to their occurrences and associated tectonic settings, these mud volcanoes were classified into four groupies. The group (I) mud volcanoes are located in the western coastal plane, whereas group (II) and (III) are situated near

C. Chung; C. You; H. Chao

2003-01-01

224

Facies analysis of Hlodufell basaltic subglacial to emergent volcano, SW Iceland: insights into sub-ice growth mechanisms and meltwater drainage  

NASA Astrophysics Data System (ADS)

Hlodufell is a subglacial to emergent basaltic volcano located 9km south of the Langjokull ice-cap in SW Iceland. This study is the first detailed facies analysis of this well-known volcano. The vertical facies architecture of the basal half of the volcano is typical of many basaltic subaqueous (including submarine) to emergent volcanoes, comprising basal pillow mounds overlain by Surtseyan eruption-fed subaqueously-deposited sediment gravity flows. However, facies in the upper part of the edifice demonstrate the influence of variable water levels more typical of englacial lakes. The Surtseyan sequence is overlain by two subaerial lava flow and cogenetic lava-fed delta sequences, separated by a second Surtseyan sequence. In addition, the uppermost lava flows are also draped by a thin veneer of Surtseyan tephra. Both lava-fed delta sequences are unusually dominated by subaerial lava breccias. This may be due to a number of factors that influence steep slope stability but the possibility of retreating ice walls should be considered. Detailed facies analysis also revealed evidence of the influence of ice on eruptive and depositional products throughout the history of the edifice. Some of the basal pillow mounds preserve metre-sized cavities with partial hyaloclastite fills, interpreted as meltout structures formed during sub-ice growth by ice-block stoping. Some mounds also have steep chill surfaces where pillows have been compressed against a rigid wall (now absent) interpreted as ice. The peripheral pillow mounds, particularly those to the immediate south of Hlodufell (Rani area) are draped by Surtseyan eruption-fed tephra deposited by erosive meltwater streamflows. The draping tephra was derived from both the first and second Surtseyan sequences. These observations illustrate that direct ice-contact and ice-block stoping was important during initial construction of the volcano and that meltwater drainage (particularly to the south) was important throughout its history.

Skilling, I. P.

2003-12-01

225

Volcano-Tectonic Deformation at Taal Volcano, Philippines  

NASA Astrophysics Data System (ADS)

Taal Volcano, located in southern Luzon, Philippines, is an unusual, tholeiitic volcano situated within a calc-alkaline arc. It is one of the most active volcanic centers in the Philippines, with some 33 historic volcanic eruptions over the past four centuries. Volcanism at Taal is at least partly tectonically controlled, suggested by its location at the intersection of regional fault structures and by the location and shape of both Taal's caldera and Volcano Island. The alignment of modern eruption centers, are controlled by regional and local structures. Here, we review geomorphic and geodetic observations that constrain both tectonic and volcanic deformation in the vicinity of Taal volcano. We use GPS measurements from a 52-station GPS network measured from 1996 - 2001 to investigate overall plate interaction and microplate (intra-arc) deformation. The velocity field indicates that the majority of the Philippine Sea - Eurasia plate convergence is taking place west of Luzon, presumably largely by subduction at the Manila trench. A relatively small fraction of the convergence appears to be taking place within Luzon or across the East Luzon trough. The major intra-arc deformation is accommodated by strike-slip motion along the Philippine Fault, ranging from 25-40 mm/yr left-lateral slip. Detailed measurements in southern Luzon also indicate significant intra-arc deformation west of the Philippine Fault. GPS measurements in southwestern Luzon indicate significant motion within the arc, which could be explained by 11-13 mm/yr of left-lateral shear along the "Macolod Corridor", within which Taal Volcano resides. A dense network of continuous single- and dual-frequency GPS receivers at Taal Volcano, Philippines reveals highly time-variable deformation behavior, similar to that observed at other large calderas. While the caldera has been relatively quiescent for the past 2-3 years, previous deformation includes two major phases of intra-caldera deformation, including two phases of inflation and deflation in 1998-2000. The February-November 2000 period of inflation was characterized by approximately 120 mm of uplift of the center of Volcano Island relative to the northern caldera rim, at average rates up to 216 mm/yr. The source of deflation in 1999 was modeled as a contractional Mogi point source centered at 4.2 km depth beneath Volcano Island; the source of inflation in 2000 was modeled as a dilatational Mogi point source centered at 5.2 km depth beneath Volcano Island. The locations of the two sources are indistinguishable within the 95% confidence estimates. Modeling using a running four-month time window from June 1999-March 2001 reveals little evidence for source migration. We find marginal evidence for an elongate source whose long axis is oriented NW-SE, paralleling the caldera-controlling fault system. We suggest that the two periods of inflation observed at Taal represent episodic intrusions of magma into a shallow reservoir centered beneath Volcano Island whose position is controlled at least in part by regional tectonic structures.

Hamburger, M. W.; Galgana, G.; Corpuz, E.; Bartel, B.

2004-12-01

226

Aerosol Lesson: Volcano Types  

NSDL National Science Digital Library

This activity has students research a list of volcanoes and then write detailed information they researched under a column that identifies that type of volcano - Cinder Cone, Composite, or Shield. Included are a worksheet and a collection of links to referential websites about specific volcanoes.

227

The Volcano Adventure Guide  

Microsoft Academic Search

Adventure travels to volcanoes offer chance encounters with danger, excitement, and romance, plus opportunities to experience scientific enlightenment and culture. To witness a violently erupting volcano and its resulting impacts on landscape, climate, and humanity is a powerful personal encounter with gigantic planetary forces. To study volcano processes and products during eruptions is to walk in the footsteps of Pliny

Fraser Goff

2005-01-01

228

A Scientific Excursion: Volcanoes.  

ERIC Educational Resources Information Center

|Reviews an educationally valuable and reasonably well-designed simulation of volcanic activity in an imaginary land. VOLCANOES creates an excellent context for learning information about volcanoes and for developing skills and practicing methods needed to study behavior of volcanoes. (Author/JN)|

Olds, Henry, Jr.

1983-01-01

229

How Volcanoes Work  

NSDL National Science Digital Library

This educational resource describes the science behind volcanoes and volcanic processes. Topics include volcanic environments, volcano landforms, eruption dynamics, eruption products, eruption types, historical eruptions, and planetary volcanism. There are two animations, over 250 images, eight interactive tests, and a volcano crossword puzzle.

2011-04-18

230

Focus: alien volcanos  

NASA Astrophysics Data System (ADS)

Part 1: Volcanoes on Earth - blowing their top; Part 2: Volcanoes of the inner Solar System - dead or alive: the Moon, Mercury, Mars, Venus; Part 3: Volcanoes of the outer Solar System - fire and ice: Io, Europa, Ganymede and Miranda, Titan, Triton, Enceladus.

Carroll, Michael; Lopes, Rosaly

2007-03-01

231

Exploration models for submarine slope sandstones  

Microsoft Academic Search

Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully\\/channel fill, slope

Slatt

1986-01-01

232

Modelling Submarine Turbidity Currents  

NASA Astrophysics Data System (ADS)

When a large scale pyroclastic flow enters the ocean it leads to the spreading of sediment across the deep ocean through particle laden flows known as turbidity currents. Turbidity currents are driven by gravitational forces associated with a density difference caused by the presence of suspended particles. This generates a flow which transports the suspended particles, but which progressively slows as they sediment to the underlying boundary. We adopt a shallow layer model in which vertical accelerations are neglected and employ a three equation system that expresses the conservation of fluid and particulate mass and formulates a balance of momentum for a current flowing down an incline. Importantly we include the effects of entrainment of surrounding fluid into the flow. Solutions are constructed using numerical means and they reveal the strong dependence of run out length on the rate of entrainment. Further, the prediction of the distribution of the deposit from the flow compares favourably with field data from the July 2003 event from Soufrière Hills volcano, Montserrat.

Goater, Alexander; Hogg, Andrew J.

2011-11-01

233

Cascades Volcano Observatory  

NSDL National Science Digital Library

This is the homepage of the United States Geological Survey's (USGS) Cascades Volcano Observatory (CVO). The site features news and events, updates on current activity of Cascade Range volcanoes, and information summaries on each of the volcanoes in the range. There are also hazard assessment reports, maps, and a 'Living with Volcanoes' feature that provides general interest information. A set of menus provides access to more technical information, such as a glossary, information on volcano hydrology, monitoring information, a photo archive, and information on CVO research projects.

2010-09-15

234

Stromboli Island (Italy): Scenarios of Tsunamis Generated by Submarine Landslides  

NASA Astrophysics Data System (ADS)

Stromboli is an Italian volcanic island known for its persistent state of activity, which leads to frequent mass failures and consequently to frequent tsunamis ranging from large (and rare) catastrophic events involving the entire southern Tyrrhenian Sea to smaller events with, however, extremely strong local impact. Most of tsunamigenic landslides occur in the Sciara del Fuoco (SdF) zone, which is a deep scar in the NW flank of the volcano, that was produced by a Holocene massive flank collapse and that is the accumulation area of all the eruptive ejecta from the craters. Shallow-water bathymetric surveys around the island help one to identify submarine canyons and detachment scars giving evidence of mass instabilities and failures that may have produced and might produce tsunamis. The main purpose of this paper is to call attention to tsunami sources in Stromboli that are located outside the SdF area. Further, we do not touch on tsunami scenarios associated with gigantic sector collapses that have repeat times in the order of several thousands of years, but rather concentrate on intermediate size tsunamis, such as the ones that occurred in December 2002. Though we cannot omit tsunamis from the zone of the SdF, the main emphasis is on the elaboration of preliminary scenarios for three more possible source areas around Stromboli, namely Punta Lena Sud, Forgia Vecchia and Strombolicchio, with the aim of purposeful contributing to the evaluation of the hazard associated with such events and to increase the knowledge of potential threats affecting Stromboli and the nearby islands of the Aeolian archipelago. The simulations show that tsunami sources outside of the SdF can produce disastrous effects. As a consequence, we recommend that the monitoring system that is presently operating in Stromboli and that is focussed on the SdF source area be extended in order to cover even the other sources. Moreover, a synoptic analysis of the results from all the considered tsunami scenarios leads to a very interesting relation between the tsunami total energy and the landslide potential energy, that could be used as a very effective tool to evaluate the expected tsunami size from estimates of the landslide size.

Tinti, Stefano; Zaniboni, Filippo; Pagnoni, Gianluca; Manucci, Anna

2008-12-01

235

Mount Rainier, a decade volcano  

SciTech Connect

Mount Rainier, recently designated as a decade volcano, is a 14,410 foot landmark which towers over the heavily populated southern Puget Sound Lowland of Washington State. It last erupted in the mid-1800's and is an obvious threat to this area, yet Rainier has received little detailed study. Previous work has divided Rainier into two distinct pre-glacial eruptive episodes and one post-glacial eruptive episode. In a pilot project, the authors analyzed 253 well-located samples from the volcano for 27 major and trace elements. Their objective is to test the value of chemical compositions as a tool in mapping the stratigraphy and understanding the eruptive history of the volcano which they regard as prerequisite to determining the petrogenesis and potential hazard of the volcano. The preliminary data demonstrates that variation between flows is significantly greater than intra-flow variation -- a necessary condition for stratigraphic use. Numerous flows or groups of flows can be distinguished chemically. It is also apparent from the small variation in Zr abundances and considerable variation in such ratios as Ba/Nb that fractional crystallization plays a subordinate role to some form of mixing process in the origin of the Mount Rainier lavas.

Kuehn, S.C.; Hooper, P.R. (Washington State Univ., Pullman, WA (United States). Dept. of Geology); Eggers, A.E. (Univ. of Puget Sound, Tacoma, WA (United States). Dept. of Geology)

1993-04-01

236

Mt. Erebus: A Surprising Volcano: Grades K-1: Illustrated Book  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. Students read about the volcano in a simplified manner. The text is written at a kindergarten through grade one reading level. This version is a full-color PDF that can be printed, cut and folded to form a book. Each book contains color photographs and illustrations.

Fries-Gaither, Jessica

237

Laboratory simulation of volcano seismicity.  

PubMed

The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt from Mount Etna volcano (Italy) was deformed and fractured. The experiment was monitored with an array of transducers around the sample to permit full-waveform capture, location, and analysis of microseismic events. Rapid post-failure decompression of the water-filled pore volume and damage zone triggered many low-frequency events, analogous to volcanic long-period seismicity. The low frequencies were associated with pore fluid decompression and were located in the damage zone in the fractured sample; these events exhibited a weak component of shear (double-couple) slip, consistent with fluid-driven events occurring beneath active volcanoes. PMID:18845753

Benson, Philip M; Vinciguerra, Sergio; Meredith, Philip G; Young, R Paul

2008-10-10

238

Location, Location, Location!  

ERIC Educational Resources Information Center

|Of prime importance in real estate, location is also a key element in the appeal of romances. Popular geographic settings and historical periods sell, unpopular ones do not--not always with a logical explanation, as the author discovered when she conducted a survey on this topic last year. (Why, for example, are the French Revolution and the…

Ramsdell, Kristin

2004-01-01

239

Growth and collapse of the Reunion Island volcanoes  

NASA Astrophysics Data System (ADS)

This work presents the first exhaustive study of the entire surface of the Reunion Island volcanic system. The focus is on the submarine part, for which a compilation of all multibeam data collected during the last 20 years has been made. Different types of submarine features have been identified: a coastal shelf, debris avalanches and sedimentary deposits, erosion canyons, volcanic constructions near the coast, and seamounts offshore. Criteria have been defined to differentiate the types of surfaces and to establish their relative chronology where possible. Debris avalanche deposits are by far the most extensive and voluminous formations in the submarine domain. They have built four huge Submarine Bulges to the east, north, west, and south of the island. They form fans 20-30 km wide at the coastline and 100-150 km wide at their ends, 70-80 km offshore. They were built gradually by the superimposition and/or juxtaposition of products moved during landslide episodes, involving up to several hundred cubic kilometers of material. About 50 individual events deposits can be recognized at the surface. The landslides have recurrently dismantled Piton des Neiges, Les Alizés, and Piton de La Fournaise volcanoes since 2 Ma. About one third are interpreted as secondary landslides, affecting previously emplaced debris avalanche deposits. On land, landslide deposits are observed in the extensively eroded central area of Piton des Neiges and in its coastal areas. Analysis of the present-day topography and of geology allows us to identify presumed faults and scars of previous large landslides. The Submarine Bulges are dissected and bound by canyons up to 200 m deep and 40 km long, filled with coarse-grained sediments, and generally connected to streams onshore. A large zone of sedimentary accumulation exists to the north-east of the island. It covers a zone 20 km in width, extending up to 15 km offshore. Volcanic constructions are observed near the coast on both Piton des Neiges and Piton de la Fournaise volcanoes and are continuations of subaerial structures. Individual seamounts are present on the submarine flanks and the surrounding ocean floor. A few seem to be young volcanoes, but the majority are probably old, eroded seamounts. This study suggests a larger scale and frequency of mass-wasting events on Reunion Island compared to similar islands. The virtual absence of downward flexure of the lithosphere beneath the island probably contributes to this feature. The increased number of known flank-failure events has to be taken into consideration when assessing hazards from future landslides, in particular, the probability of landslide-generated tsunamis.

Oehler, Jean-François; Lénat, Jean-François; Labazuy, Philippe

2008-04-01

240

Volcano Seismology  

NASA Astrophysics Data System (ADS)

- A fundamental goal of volcano seismology is to understand active magmatic systems, to characterize the configuration of such systems, and to determine the extent and evolution of source regions of magmatic energy. Such understanding is critical to our assessment of eruptive behavior and its hazardous impacts. With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques, rapid progress is being made toward a synthesis of high-quality seismic data to develop a coherent model of eruption mechanics. Examples of recent advances are: (1) high-resolution tomography to image subsurface volcanic structures at scales of a few hundred meters; (2) use of small-aperture seismic antennas to map the spatio-temporal properties of long-period (LP) seismicity; (3) moment tensor inversions of very-long-period (VLP) data to derive the source geometry and mass-transport budget of magmatic fluids; (4) spectral analyses of LP events to determine the acoustic properties of magmatic and associated hydrothermal fluids; and (5) experimental modeling of the source dynamics of volcanic tremor. These promising advances provide new insights into the mechanical properties of volcanic fluids and subvolcanic mass-transport dynamics. As new seismic methods refine our understanding of seismic sources, and geochemical methods better constrain mass balance and magma behavior, we face new challenges in elucidating the physico-chemical processes that cause volcanic unrest and its seismic and gas-discharge manifestations. Much work remains to be done toward a synthesis of seismological, geochemical, and petrological observations into an integrated model of volcanic behavior. Future important goals must include: (1) interpreting the key types of magma movement, degassing and boiling events that produce characteristic seismic phenomena; (2) characterizing multiphase fluids in subvolcanic regimes and determining their physical and chemical properties; and (3) quantitatively understanding multiphase fluid flow behavior under dynamic volcanic conditions. To realize these goals, not only must we learn how to translate seismic observations into quantitative information about fluid dynamics, but we also must determine the underlying physics that governs vesiculation, fragmentation, and the collapse of bubble-rich suspensions to form separate melt and vapor. Refined understanding of such processes-essential for quantitative short-term eruption forecasts-will require multidisciplinary research involving detailed field measurements, laboratory experiments, and numerical modeling.

Chouet, B.

241

Explorations of Mariana Arc Volcanoes Reveal New Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

Some 20,000 km of volcanic arcs, roughly one-third the length of the global mid-ocean ridge (MOR) system, rim the western Pacific Ocean. Compared to 25 years of hydrothermal investigations along MORs, exploration of similar activity on the estimated ~600 submarine arc volcanoes is only beginning [Ishibashi and Urabe, 1995; De Ronde et al., 2003]. To help alleviate this under-sampling, the R/V T. G. Thompson was used in early 2003 (9 February to 5 March) to conduct the first complete survey of hydrothermal activity along 1200 km of the Mariana intra-oceanic volcanic arc. This region includes both the Territory of Guam and the Commonwealth of the Northern Mariana Islands. The expedition mapped over 50 submarine volcanoes with stunning new clarity (Figures 1 and 2) and found active hydrothermal discharge at 12 sites, including the southern back-arc site. This includes eight new sites along the arc (West Rota, Northwest Rota, E. Diamante, Zealandia Bank, Maug Caldera, Ahyi, Daikoku, and Northwest Eifuku) and four sites of previously known hydrothermal activity (Seamount X, Esmeralda, Kasuga 2, and Nikko) (Figures 1 and 2). The mapping also fortuitously provided a ``before'' image of the submarine flanks of Anatahan Island, which had its first historical eruption on 10 May 2003 (Figures 1 and 3).

Embley, R. W.; Baker, E. T.; Chadwick, W. W., Jr.; Lupton, J. E.; Resing, J. A.; Massoth, G. J.; Nakamura, K.

2004-01-01

242

Evolution of the Hawaiian Mantle Plume: Shield and Rejuvenescent Magmatism at Middle Bank, the Youngest Sunken Hawaiian Volcano  

NASA Astrophysics Data System (ADS)

Post-shield volcanism provides unique insight into the structure of mantle plumes and the magmatic processes responsible for the evolution of ocean islands. Middle Bank is the closest seamount to the main Hawaiian archipelago, thus providing a perspective into the processes related to the dying phase of a Hawaiian volcano. We conducted a detailed survey of the volcano in 2007 using multibeam sonar coupled with Jason2 ROV imaging and sampling. According to plate tectonic models, Middle Bank volcano should be about 9.6 Ma, if it formed near the present location of Kilauea. Middle Bank is 100 km in diameter and rises nearly 5000 m from base level. Its morphology is dominated by three major rift zones that emanate to the east, west, and south from the beveled summit platform. The rifts are separated by talus fans, and the volcano is surrounded by dozens of satellite cones. Many of the satellite cones are covered by remarkably unsedimented lavas that were erupted in the submarine environment, which we interpret as a rejuvenated stage of volcanism. Most of the sampled rocks are strongly alkaline and range from basanite to hawaiite and trachyte. Samples from two sites are tholeiitic, which is consistent with them forming during the shield stage of volcanism. If so, then most of the late history of volcanism, from shield building to rejuvenated volcanism is preserved at Middle Bank. The alkaline basalts and basanites have La/Sm and La/Yb ratios that are higher than the tholeiites, and all of the rocks are strongly LREE enriched. Major and trace element compositions of hawaiites and trachytes are consistent with large amounts of crystal fractionation, which especially affected magmas erupted on the outer flanks of the volcano. The tholeiites have Sr/Nb and Zr/Nb that suggest that the Middle Bank shield is akin to the modern-day "Kea" trend geochemically. Thus, Middle Bank has preserved the archetypical tholeiitic-shield to alkaline-rejuvenated evolutionary stages that characterize the subaerial Hawaiian volcanoes.

Geist, D.; Garcia, M.; Ito, G.; Harpp, K.; Weis, D.

2008-12-01

243

Currents in Monterey Submarine Canyon  

Microsoft Academic Search

Flow fields of mean, subtidal, and tidal frequencies between 250 and 3300 m water depths in Monterey Submarine Canyon are examined using current measurements obtained in three yearlong field experiments. Spatial variations in flow fields are mainly controlled by the topography (shape and width) of the canyon. The mean currents flow upcanyon in the offshore reaches (>1000 m) and downcanyon

J. P. Xu; Marlene A. Noble

2009-01-01

244

Initial waves from submarine landslides  

Microsoft Academic Search

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling.

R. Weiss; C. Synolakis

2009-01-01

245

Initial waves from submarine landslides  

Microsoft Academic Search

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling.

R. Weiss; C. E. Synolakis; J. A. O'Shay

2010-01-01

246

Submarine Tanker Concepts and Problems.  

National Technical Information Service (NTIS)

The National energy crisis of the U.S. can be responded to and diminished by the use of the large deposits of oil in the Arctic. This study discusses the use of nuclear powered submarine tankers for the transportation of oil from the Arctic regions. The a...

P. Moloney

1974-01-01

247

Human powered submarine propeller design  

Microsoft Academic Search

While all parts of a submarine contribute to its overall performance, the propeller blade design is often neglected due to the difficulties in analyzing the impact in design changes combined with a lack of previous research in blade designs for the power and speed requirements as dictated by a human powered vehicle. To aid us in the design of our

B. Ellis; D. Wacholder

2003-01-01

248

Multibeam Bathymetry of Haleakala Volcano, Maui  

NASA Astrophysics Data System (ADS)

The submarine northeast flank of Haleakala Volcano, Maui was mapped in detail during the summers of 2001 and 2002 by a joint team from the Japan Marine Science and Technology Center (JAMSTEC), Tokyo Institute of Technology, University of Hawaii, and the U.S. Geological Survey. JAMSTEC instruments used included SeaBeam 2112 hull-mounted multibeam sonar (bathymetry and sidescan imagery), manned submersible Shinkai 6500 and ROV Kaiko (bottom video, photographs and sampling of Hana Ridge), gravimeter, magnetometer, and single-channel seismic system. Hana Ridge, Haleakala's submarine east rift zone, is capped by coral-reef terraces for much of its length, which are flexurally tilted towards the axis of the Hawaiian Ridge and delineate former shorelines. Its deeper, more distal portion exhibits a pair of parallel, linear crests, studded with volcanic cones, that suggest lateral migration of the rift zone during its growth. The northern face of the arcuate ridge terminus is a landslide scar in one of these crests, while its southwestern prong is a small, constructional ridge. The Hana slump, a series of basins and ridges analogous to the Laupahoehoe slump off Kohala Volcano, Hawaii, lies north of Hana Ridge and extends down to the Hawaiian moat. Northwest of this slump region a small, dual-crested ridge strikes toward the Hawaiian moat and is inferred to represent a fossil rift zone, perhaps of East Molokai Volcano. A sediment chute along its southern flank has built a large submarine fan with a staircase of contour-parallel folds on its surface that are probably derived from slow creep of sediments down into the moat. Sediments infill the basins of the Hana slump [Moore et al., 1989], whose lowermost layers have been variously back-tilted by block rotation during slumping and flexural loading of the Hawaiian Ridge; the ridges define the outer edges of those down-dropped blocks, which may have subsided several kilometers. An apron of volcaniclastic debris shed from subaerial Haleakala smoothes the upper slopes of the slump complex. The slump and apron do not extend beyond the formerly-subaerial portion of Hana Ridge, implying that supply of subaerially-erupted volcaniclastic sediments may be a necessary precondition to massive slope failure.

Eakins, B. W.; Robinson, J.

2002-12-01

249

Volcanoes: Nature's Caldrons Challenge Geochemists.  

ERIC Educational Resources Information Center

Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

Zurer, Pamela S.

1984-01-01

250

Volcanoes: Nature's Caldrons Challenge Geochemists.  

ERIC Educational Resources Information Center

|Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

Zurer, Pamela S.

1984-01-01

251

Evidence for deformation associated with the 1998 eruption of Axial Volcano, Juan de Fuca Ridge, from acoustic extensometer measurements  

Microsoft Academic Search

Acoustic extensometer instruments capable of making precise daily measurements of horizontal distance were deployed across the north rift zone of Axial Volcano in June 1996 and were in place when a submarine eruption began on Axial's south rift zone in January 1998. The instruments recorded a gradual 9-cm extension over a 405-m baseline leading up to the eruption, and then

William W. Chadwick; Robert W. Embley; Hugh B. Milburn; Christian Meinig; Michael Stapp

1999-01-01

252

Simulation of submarine hovering based on PID control  

Microsoft Academic Search

The underwater hovering of submarine is a nonlinear process, which changes with the submarine state and navigation condition. Analysis is made on motion characters, realizing conditions and disturbing factors for submarine. The submarine hovering mathematic model is established, as well as the disturbing force. PID control is used to simulate submarine hovering, which provides the technical support.

Xiong Ying; Xu Jian

2010-01-01

253

Submarine silicic volcanism of the Healy caldera, southern Kermadec arc (SW Pacific): I - volcanology and eruption mechanisms  

Microsoft Academic Search

The submarine Healy volcano (southern Kermadec arc), with a 2-2.5 km wide caldera, is pervasively mantled with highly vesicular silicic pumice within a water depth of 1,150-1,800 m. Pumices comprise type 1 white-light grey pumice with ⢾ mm vesicles and weak-moderate foliation, type 2 grey pumice with millimetre-scale laminae, flow banded foliation, including stretched vesicles ⣗ mm in length, and

Ian C. Wright; John A. Gamble; Phil A. R. Shane

2003-01-01

254

Mineral chemistry of submarine lavas from Hilo Ridge, Hawaii: implications for magmatic processes within Hawaiian rift zones  

Microsoft Academic Search

The crustal history of volcanic rocks can be inferred from the mineralogy and compositions of their phenocrysts which record\\u000a episodes of magma mixing as well as the pressures and temperatures when magmas cooled. Submarine lavas erupted on the Hilo\\u000a Ridge, a rift zone directly east of Mauna Kea volcano, contain olivine, plagioclase, augite ±orthopyroxene phenocrysts. The\\u000a compositions of these phenocryst

Huai-Jen Yang; Frederick A. Frey; David A. Clague; Michael O. Garcia

1999-01-01

255

Galactic Super Volcano Similar to Iceland Volcano  

NASA Video Gallery

This composite image from NASAs Chandra X-ray Observatory with radio data from the Very Large Array shows a cosmic volcano being driven by a black hole in the center of the M87 galaxy. This eruption is pumping energy into the black hole's surroundings and preventing hundreds of millions of new stars from forming just as the volcano in Iceland caused disruptions in the Earth's atmosphere.

Jim Wilson

2010-08-27

256

Decreasing magmatic footprints of individual volcanoes in a waning basaltic field  

Microsoft Academic Search

The distribution and characteristics of individual basaltic volcanoes in the waning Southwestern Nevada Volcanic Field provide insight into the changing physical nature of magmatism and the controls on volcano location. During Pliocene-Pleistocene times the volumes of individual volcanoes have decreased by more than one order of magnitude, as have fissure lengths and inferred lava effusion rates. Eruptions evolved from Hawaiian-style

G. A. Valentine; F. V. Perry

2006-01-01

257

Paleomagnetic constraints on eruption patterns at the Pacaya composite volcano, Guatemala  

Microsoft Academic Search

Pacaya volcano is an active composite volcano located in the volcanic highlands of Guatemala about 40 km south of Guatemala City. Volcanism at Pacaya alternates between Strombolian and Vulcanian, and during the past five years there has been a marked increase in the violence of eruptions. The volcano is composed principally of basalt flows interbedded with thin scoria fall units,

F Michael Conway; Jimmy F Diehl; Otoniel Matías

1992-01-01

258

SAR measurements of surface displacements at Augustine volcano, Alaska from 1992 to 2005  

Microsoft Academic Search

Augustine volcano is an active stratovolcano located at the southwest of Anchorage, Alaska. Augustine volcano had experienced seven significantly explosive eruptions in 1812, 1883, 1908, 1935, 1963, 1976, and 1986, and a minor eruption in January 2006. We measured the surface displacements of the volcano by radar interferometry and GPS before and after the eruption in 2006. ERS-1\\/2, RADARSAT-1 and

C.-W. Lee; Z. Lu; O.-I. Kwoun

2007-01-01

259

Spatial and temporal variations of the state of stress at Fernandina volcano, Galápagos, revealed by InSAR measurements  

NASA Astrophysics Data System (ADS)

Fernandina volcano forms the youngest and westernmost island of the Galápagos Archipelago, a group of volcanic islands located near the equator and 1000 km west of Ecuador. Twenty-five eruptions in the last two hundred years make Fernandina the most active volcano in the archipelago and one of the most active volcanoes in the world. Most eruptions occur along fissures fed by dikes that propagate from the central magmatic system and from reservoirs centered under the summit caldera. Eruptive fissures in the sub-aerial portion of the volcano form two distinct sets: (1) arcuate or circumferential fissures characterize the upper portion of the volcano around the caldera while (2) radial fissures are present on the lower flanks. The sub-aerial portion of the volcano lacks of well-developed rift zones, while the submarine part of Fernandina shows three rifting zones that extend from the western side of the island. Dike propagation in a volcano is not a random process but it is controlled by the orientation of the principal stresses, with the dike orthogonal to the least compressive stress. Chadwick and Dietriech [1995] attributed the pattern of fissures at Fernandina to stresses induced by the sub-caldera magma body. Changes in pressure in a flat-topped magma reservoir produce circumferential tensional stress at the summit that becomes radial outward on the flanks. They also suggested that a feedback relationship exists between circumferential and radial intrusions where the intrusion in one orientation tends to favor a future intrusion in the other orientation. Using Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface deformation at Fernandina spanning the last three eruptions (1995 - radial, 2005 - circumferential and 2009 - radial) we can infer the geometry of the feeding dikes and calculate stress changes in the volcanic edifice in space and time. Large spatial coverage and frequent SAR acquisitions during the 2009 eruption allow us to study its onset and effects in terms of surface displacement. A SAR image acquired only two hours before the opening of the first eruptive vent shows distinct uplift of a circular area centered below the southwestern caldera rim. This pattern of deformation is generated by the propagation of a sheet-like body gently dipping toward the central magmatic system and parallel to the caldera's major axis (WNW-ESE). SAR interferograms generated using images acquired before and after the eruption show the subsequent opening of radial fissures on the southwestern flank. As for the 1995 event, the dike feeding the 2009 eruptive fissures generates uplift of a semi-circular area on the eastern side of the fractures. Both eruptions are consistent with a model of eastward-shallow-dipping (~30°-35°) dike. The varying orientation of the dike during its propagation and the non-verticality when it intercept the surface imply that the least principal stress direction is not horizontal as usually assumed, but varies in space from the caldera down to the submarine rifts.

Bagnardi, M.; Amelung, F.

2011-12-01

260

Monitoring Popocatepetl volcano's glaciers (Mexico): case study of glacier extinction  

Microsoft Academic Search

Popocatépetl volcano is located 60 km southeast of Mexico City and is one of the three ice-clad volcanoes in Mexico. The two glaciers of Popocatépetl became extinct after a strong retreat due to the combination of at least three causes: global change, change in regional meteorological conditions (induced by the vicinity to highly polluted areas) and local enforcement (namely volcanic

H. Delgado; P. Julio; C. Huggel; M. Brugman

2003-01-01

261

Geomorphic evolution of the Piton des Neiges volcano (Réunion Island, Indian Ocean): Competition between volcanic construction and erosion since 1.4 Ma  

NASA Astrophysics Data System (ADS)

Réunion Island (Indian Ocean) is a volcanic complex whose eruptive history was dominated by the activity of two main edifices: Piton des Neiges (PN) and Piton de la Fournaise (PF) volcanoes. The tropical climate induces erosion processes that permanently compete with volcanic constructional processes. Exposed to the trade winds and associated heavy rainfalls, the northeastern part of the island exhibits the most complex morphological evolution. Geomorphological analysis, performed on a 50 m DEM and associated to new K-Ar ages has clarified the overall history of PN volcano. Each massif is assigned to one of the main building stages of the edifice. In addition, the arrangement of these different massifs reveals that the eruptive phases have led to successive relief inversions and successive excavations of large central depressions in the proximal area. As a result, the younger massifs are always located in more proximal parts of the volcano, the youngest being close to the edifice center. In distal areas, early lava flows were channeled into valleys incised along the massif boundaries, leading to a more complex geochronological organization. Quantitative study of the dissection of PN volcano allows us to propose a minimum eroded volume of 101 ± 44 and 105 ± 41 km3 for the Mafate and Cilaos "Cirques" (depressions), respectively, during the last 180 kyr and a minimum average long-term erosion rate of 1.2 ± 0.4 km3/ka. This leads us to estimate the removed volume during the whole history of PN volcano (> 1000 km3) as equivalent to the volume of the deposits identified on the submarine flanks of Piton des Neiges volcano. Therefore, as regressive erosion appears to be the prevailing geomorphic process during the whole PN history, it questions the presence of major flank collapses younger than 1.4 Ma on this volcano. Erosion processes have largely been neglected in recent models, but our study emphasizes them as a key component of landscape development and a major process in the morphological evolution of Réunion Island that has to be fully integrated in future studies.

Salvany, Tiffany; Lahitte, Pierre; Nativel, Pierre; Gillot, Pierre-Yves

2012-01-01

262

Decreasing Magmatic Footprints of Individual Volcanos in a Waning Basaltic Field  

SciTech Connect

The distribution and characteristics of individual basaltic volcanoes in the waning Southwestern Nevada Volcanic Field provide insight into the changing physical nature of magmatism and the controls on volcano location. During Pliocene-Pleistocene times the volumes of individual volcanoes have decreased by more than one order of magnitude, as have fissure lengths and inferred lava effusion rates. Eruptions evolved from Hawaiian-style eruptions with extensive lavas to eruptions characterized by small pulses of lava and Strombolian to violent Strombolian mechanisms. These trends indicate progressively decreasing partial melting and length scales, or magmatic footprints, of mantle source zones for individual volcanoes. The location of each volcano is determined by the location of its magmatic footprint at depth, and only by shallow structural and topographic features that are within that footprint. The locations of future volcanoes in a waning system are less likely to be determined by large-scale topography or structures than were older, larger volume volcanoes.

G.A> Valentine; F.V. Perry

2006-06-06

263

Seismic structure of Taal volcano  

NASA Astrophysics Data System (ADS)

In order to investigate seismicity and tectonic structure under Taal volcano, Philippines, a temporary seismic array consisting of 8 stations was deployed in this area since March 2008. As a pioneer seismic study in this area, our first goal is to build a robust 1-D velocity model using local earthquakes. In the mean time, we also apply ambient noise cross-correlation technique to the continuous records, aiming to search for the potential volcanic structure perturbations. While we were trying to retrieve Empirical Green's functions from cross-correlation functions (CCF) of ambient noise, unexpected linear drifting of clock time are clearly identified by the gradual shifting of symmetric center of daily CCFs. The clock errors have been further confirmed by comparing earthquake signals from teleseismic events. The errors are corrected before further data processing. Over 1100 local events are recorded in the duration from March 2008 to November 2008. Phase pickings from about 450 events are used to invert for event locations and 1-D velocity model by using the standard packages HYPO71 and VELEST. The obtained 1-D velocity model of Taal volcano is lower than the global average (AK135) at the depths less than 10 km, and most events (~90%) are also located at this shallow depth range. Two groups of seismicity are noticed, with the major one clustered under the western shore of Taal lake ranging, and the other spread from Main Crater Lake to the eastern of Taal volcano complex.

You, Shuei-Huei; Gung, Yuancheng; Konstantinou, Konstantinos I.; Lin, Cheng-Horng; Chang, Emmy T. Y.

2010-05-01

264

Sizes of Conical Volcanoes  

Microsoft Academic Search

THE shield volcano Mauna Loa in Hawaii is the world's highest mountain, 9,144 m high1, if the portion below sea level is considered in addition to the exposed 4,170 m. Why, then, are the world's highest mountains not land volcanoes? We have investigated the heights and volumes of land volcanoes to try to establish what factors prevent their development to

P. W. Francis; B. M. Abbott

1973-01-01

265

Mud volcanoes on Mars?  

NASA Astrophysics Data System (ADS)

The term mud volcano is applied to a variety of landforms having in common a formation by extrusion of mud from beneath the ground. Although mud is the principal solid material that issues from a mud volcano, there are many examples where clasts up to boulder size are found, sometimes thrown high into the air during an eruption. Other characteristics of mud volcanoes (on Earth) are discussed. The possible presence of mud volcanoes, which are common and widespread on Earth, on Mars is considered.

Komar, Paul D.

1991-06-01

266

Examination of the constructional processes of submarine Cerro Azul and the Galapagos Platform  

Microsoft Academic Search

One of the primary goals of the 2001 Drift04 cruise was to examine the constructional processes responsible for the Galapagos platform and to investigate the relationship between the platform and the overlying volcanoes. Cerro Azul volcano is located above the steep escarpment that marks the southwestern limit of the Galapagos platform, at the leading edge of the hotspot. This area

M. K. Lambert; K. S. Harpp; D. J. Geist; D. J. Fornari; M. D. Kurz; A. M. Koleszar; N. A. Rollins

2004-01-01

267

A giant three-stage submarine slide off Norway  

Microsoft Academic Search

One of the largest submarine slides known, The Storegga Slide, is located on the Norwegian continental margin. The slide is up to 450 m thick and has a total volume of about 5,600 km3. The headwall of the slide scar is 290 km long and the total run-out distance is about 800 km. The slide involved sediments of Quaternary to

Tom Bugge; Stein Befring; Robert H. Belderson; Tor Eidvin; Eystein Jansen; Neil H. Kenyon; Hans Holtedahl; Hans Petter Sejrup

1987-01-01

268

Submarines, spacecraft and exhaled breath.  

PubMed

Foreword The International Association of Breath Research (IABR) meetings are an eclectic gathering of researchers in the medical, environmental and instrumentation fields; our focus is on human health as assessed by the measurement and interpretation of trace chemicals in human exhaled breath. What may have escaped our notice is a complementary field of research that explores the creation and maintenance of artificial atmospheres practised by the submarine air monitoring and air purification (SAMAP) community. SAMAP is comprised of manufacturers, researchers and medical professionals dealing with the engineering and instrumentation to support human life in submarines and spacecraft (including shuttlecraft and manned rockets, high-altitude aircraft, and the International Space Station (ISS)). Here, the immediate concerns are short-term survival and long-term health in fairly confined environments where one cannot simply 'open the window' for fresh air. As such, one of the main concerns is air monitoring and the main sources of contamination are CO(2) and other constituents of human exhaled breath. Since the inaugural meeting in 1994 in Adelaide, Australia, SAMAP meetings have been held every two or three years alternating between the North American and European continents. The meetings are organized by Dr Wally Mazurek (a member of IABR) of the Defense Systems Technology Organization (DSTO) of Australia, and individual meetings are co-hosted by the navies of the countries in which they are held. An overriding focus at SAMAP is life support (oxygen availability and carbon dioxide removal). Certainly, other air constituents are also important; for example, the closed environment of a submarine or the ISS can build up contaminants from consumer products, cooking, refrigeration, accidental fires, propulsion and atmosphere maintenance. However, the most immediate concern is sustaining human metabolism: removing exhaled CO(2) and replacing metabolized O(2). Another important concern is a suite of products from chemical reactions among oxidizing compounds with biological chemicals such as amines, thiols and carbonyls. SAMAP Meeting We (Armin and Joachim) attended the 2011 SAMAP conference in Taranto, Italy (10-14 October), which occurred just a few weeks after the IABR meeting in Parma, Italy (11-15 September 2011). It was held at the Officers' Club of the Taranto Naval Base under the patronage of the Italian navy; the local host was Lucio Ricciardi of the University of Insubria, Varese, Italy. At the 2011 SAMAP meeting, the theme was air-independent propulsion (AIP), meaning the capability of recharging the main batteries of the submarine without the need to surface. Only a few navies (e.g. US, UK, France, Russia, China) have historically had this capability using nuclear-powered submarines that can function underwater for extended periods of time (months). Most navies operate submarines with conventional diesel-electric propulsion, wherein diesel-powered generators charge battery banks which then drive an electric motor connected to the propeller. The batteries are charged while the boat is on the surface or during snorkelling, when the boat is submerged a few meters below the surface and a snorkel tube is extended to the surface. The period between battery charges can vary from several hours to one or two days depending on the power requirements and the nature of the mission. The process is necessary for breathing air revitalization (flushing out accumulated contaminants) and for the operation of the diesel engines. However, during this period the submarine is vulnerable to detection. Since the 1940s there have been various attempts to develop a power generation system that is independent of external air (AIP). To this end hydrogen peroxide was initially used and later liquid oxygen (LOX). Currently, most AIP submarines use fuel cell technology (LOX and hydrogen) to supplement the conventional diesel-electric system in order to extend the underwater endurance to 2-3 weeks. These propulsion engineering changes also reduce per

Pleil, Joachim D; Hansel, Armin

2012-02-27

269

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2013-07-01

270

Initial waves from submarine landslides  

NASA Astrophysics Data System (ADS)

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling. Submarine mass failure exhibits slower speeds and water gravitationally adjusts to a new potential field while the submarine mass is failing. Empirical formulae and computer models exist to calculate the one or two-dimensional surface waveform generated by underwater mass movements. For different empirical formulae, estimates vary over orders of magnitude for the same slide. We present the scatter from ten different empirical formulations for the leading wave amplitude for 19 different underwater landslides. Some of these formulations are based on modeling, some on analytical solutions, and some are based on experimental data. The scatter highlights that it is important to use higher order approximations of the Navier-Stokes equations to reliably and robustly compute the interaction between water surface and the deforming mass. We carry out modeling with iSALE, a hydrocode that numerically solves the compressible Navier-Stokes equations in a multi-material and multi-rheology framework, and present preliminary results for the leading wave height with varying rheologies to account for different slide materials. It appears that multi-material modeling is important in for understanding the hydrodynamics of tsunamis generated by submarine mass failures under geophysically realistic conditions.

Weiss, R.; Synolakis, C.

2009-12-01

271

Initial waves from submarine landslides  

NASA Astrophysics Data System (ADS)

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling. Submarine mass failure exhibits slower speeds and water gravitationally adjusts to a new potential field while the submarine mass is failing. Empirical formulae and computer models exist to calculate the one or two-dimensional surface waveform generated by underwater mass movements. For different empirical formulae, estimates vary over orders of magnitude for the same slide. We present the scatter from ten different empirical formulations for the leading wave amplitude for 19 different underwater landslides. Some of these formulations are based on modeling, some on analytical solutions, and some are based on experimental data. The scatter highlights that it is important to use higher order approximations of the Navier-Stokes equations to reliably and robustly compute the interaction between water surface and the deforming mass. We carry out modeling with iSALE, a hydrocode that numerically solves the compressible Navier-Stokes equations in a multi-material and multi-rheology framework, and present preliminary results for the leading wave height with varying rheologies to account for different slide materials. It appears that multi-material modeling is important in for understanding the hydrodynamics of tsunamis generated by submarine mass failures under geophysically realistic conditions.

Weiss, R.; Synolakis, C. E.; O'Shay, J. A.

2010-12-01

272

Anatomy of a Volcano  

NSDL National Science Digital Library

This interactive from NOVA Online provides a detailed look at the inner workings of one of the world's most dangerous volcanoes, Nyiragongo in the Democratic Republic of Congo. Users can click on highlighted points on a crossection of the volcano to see photos and read about its features and eruptive products.

273

Chaiten Volcano Still Active  

NSDL National Science Digital Library

This Boston Globe news article shows 12 stunning pictures of the Chaiten Volcano erupting in Chile, its first activity in over 9,000 years. The most recent eruptive phase of the volcano began on May 2, 2008, and is ongoing. The site also has a blog of open, public commentary.

274

Mud Volcanoes on Mars.  

National Technical Information Service (NTIS)

The term mud volcano is applied to a variety of landforms having in common a formation by extrusion of mud from beneath the ground. Although mud is the principal solid material that issues from a mud volcano, there are many examples where clasts up to bou...

P. D. Komar

1991-01-01

275

Groundwater at Mayon, Volcano  

Microsoft Academic Search

Around Mayon Volcano, Philippines, anecdotal evidence and rainfall normalized spring discharge data suggest that the water table 8 km from the summit of the volcano drops prior to eruptions. Residents report that they had to deepen their shallow wells in 1993 (some before and others following the eruption). In some cases they had to dig as far as 5 meters

S. E. Albano; T. Sandoval; R. Toledo

2001-01-01

276

Correlation of submarine deposits and witness accounts of the 1952 Myojinsho submarine eruption, Izu-Bonin arc, by bathymetric survey  

NASA Astrophysics Data System (ADS)

The relationship between eruptive phenomena during the 1952 phreatomagmatic eruption and consequent deposits under seawater is discussed, on the basis of bathymetric survey of Myojinsho volcano, Izu-Bonin island arc (32°55’N, 140°00’E). We carried out some research cruises by the ship Natsushima (JAMSTEC) in 2006-2008. We used unmanned bathymetric vehicle, Hyperdolphin, for observation and sampling of the submarine deposit. Myojinsho volcano is an active post-caldera volcano that grew on the northeastern rim of Myojinsho caldera (8 x 6 km in diameter). There have been many reports of colored seawater, and we also recognized a bubbly column above the summit of Myojinsho (Myojin reef; ca. 50 m below sea level) during acoustic survey. The 1952 eruption was the latest eruption that formed and destroyed new island above sea level, and would have been the first submarine eruption to be recorded by good scientific standard. This eruption was firstly recognized at the middle of September, 1952, and explosions and dome growth have been documented for about 1 year till the middle of September, 1953. There are many time series color photographs of explosions so that we can evaluate these explosions quantitatively (Ossaka, 1991). These records indicate that most of the cock’s tail jets are limited within the proximal area (ca. 500m) from the center of explosions, whereas the base surges and lateral steam clouds reach farther than ca. 500 m. During the bathymetric survey, we found several small lobes of pumice-rich deposits (< 1 m thick, several meter wide, several tens of meter long) on the sandy flat slope father than ca. 500 m from the summit of Myojinsho (deeper than ca. 300 m below sea level). Large pumices are concentrated at the front of each lobe, and the lobes become thinner toward the summit. On the other hand, the proximal deposit (<500 m from the summit) is characterized by scattered large angular blocky rocks or pumices. The largest blocks are as large as several meters in diameter. The compositional variations and textural features of these pumices and blocks are similar to those reported for samples obtained during the eruption. The correspondence of the lateral changes in witnessed phenomena (cock’s tail jets to base surges) and in depositional features (scattered blocks to pumice lobes) would indicate that (1) the lobes of pumices are derived either by base surges or by lateral steam clouds, and that (2) large angular blocks are derived by cock’s tail jets during explosions or dome collapse occurred at the end of the eruption.

Shimano, T.; Tani, K.; Maeno, F.; Fiske, R. S.; Shukuno, H.; Ito, K.; Shimoda, G.; Suzuki, Y. J.; Yoshida, T.; Taniguchi, H.

2009-12-01

277

Alaska Volcano Observatory  

NSDL National Science Digital Library

This is the homepage of the Alaska Volcano Observatory, a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). Users can access current information on volcanic activity in Alaska and the Kamchatka Penninsula, including weekly and daily reports and information releases about significant changes in any particluar volcano. An interactive map also directs users to summaries and activity notifications for selected volcanoes, or through links to webcams and webicorders (recordings of seismic activity). General information on Alaskan volcanoes includes descriptions, images, maps, bibliographies, and eruptive histories. This can be accessed through an interactive map or by clicking on an alphabetic listing of links to individual volcanoes. There is also an online library of references pertinent to Quaternary volcanism in Alaska and an image library.

278

‘New’ Antarctic volcanos  

NASA Astrophysics Data System (ADS)

Two previously unknown volcanos that show evidence o f recent eruptions were discovered in March on the east side of the Antarctic Peninsula, according to the National Science Foundation. The discovery brings to five the number of known active volcanos on the continent.Volcanic debris still covers a large swath of the adjacent Larsen Ice Shelf, pointing to very recent activity. In addition, one of the volcanos was steaming when the discovery was made, reports Oscar Gonzalez-Ferran of the University of Chile at Santiago. He made the discovery while doing a geophysical survey by helicopter of the Antarctic Peninsula. The two volcanos constitute the southernmost extension of the eastern side of the ‘ring of fire,’ a ring of volcanos that is believed to mark the active subduction zone on the periphery of the Pacific Ocean.

279

Flank tectonics of Martian volcanoes  

SciTech Connect

On the flanks of Olympus Mons is a series of terraces, concentrically distributed around the caldera. Their morphology and location suggest that they could be thrust faults caused by compressional failure of the cone. In an attempt to understand the mechanism of faulting and the possible influences of the interior structure of Olympus Mons, the authors have constructed a numerical model for elastic stresses within a Martian volcano. In the absence of internal pressurization, the middle slopes of the cone are subjected to compressional stress, appropriate to the formation of thrust faults. These stresses for Olympus Mons are {approximately}250 MPa. If a vacant magma chamber is contained within the cone, the region of maximum compressional stress is extended toward the base of the cone. If the magma chamber is pressurized, extensional stresses occur at the summit and on the upper slopes of the cone. For a filled but unpressurized magma chamber, the observed positions of the faults agree well with the calculated region of high compressional stress. Three other volcanoes on Mars, Ascraeus Mons, Arsia Mons, and Pavonis Mons, possess similar terraces. Extending the analysis to other Martian volcanoes, they find that only these three and Olympus Mons have flank stresses that exceed the compressional failure strength of basalt, lending support to the view that the terraces on all four are thrust faults.

Thomas, P.J. (Univ. of Wisconsin, Eau Claire (USA)); Squyres, S.W. (Cornell Univ., Ithaca, NY (USA)); Carr, M.H. (Geological Survey, Menlo Park, CA (USA))

1990-08-30

280

Gravity model studies of Newberry Volcano, Oregon  

SciTech Connect

Newberry, Volcano, a large Quaternary volcano located about 60 km east of the axis of the High Cascades volcanoes in central Oregon, has a coincident positive residual gravity anomaly of about 12 mGals. Model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20-km diameter and 2-km thickness, at depths above 4 km below sea level. However, uplifted basement in a northwest trending ridge may form part of the underlying excess mass, thus reducing the volume of the subvolcanic intrusive. A ring dike of mafic composition is inferred to intrude to near-surface levels along the caldera ring fractures, and low-density fill of the caldera floor probably has a thickness of 0.7--0.9 km. The gravity anomaly attributable to the volcano is reduced to the east across a north-northwest trending gravity anomaly gradient through Newberry caldera and suggests that normal, perhaps extensional, faulting has occurred subsequent to caldera formation and may have controlled the location of some late-stage basaltic and rhyolitic eruptions. Significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data.

Gettings, M.E.; Griscom, A.

1988-09-10

281

Gravity model studies of Newberry Volcano, Oregon  

USGS Publications Warehouse

Newberry Volcano, a large Quaternary volcano located about 60 km east of the axis of the High Cascades volcanoes in central Oregon, has a coincident positive residual gravity anomaly of about 12 mGals. Model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20-km diameter and 2-km thickness, at depths above 4 km below sea level. However, uplifted basement in a northwest trending ridge may form part of the underlying excess mass, thus reducing the volume of the subvolcanic intrusive. A ring dike of mafic composition is inferred to intrude to near-surface levels along the caldera ring fractures, and low-density fill of the caldera floor probably has a thickness of 0.7-0.9 km. The gravity anomaly attributable to the volcano is reduced to the east across a north-northwest trending gravity anomaly gradient through Newberry caldera and suggests that normal, perhaps extensional, faulting has occurred subsequent to caldera formation and may have controlled the location of some late-stage basaltic and rhyolitic eruptions. Significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data. -Authors

Gettings, M. E.; Griscom, A.

1988-01-01

282

Nitrogen biogeochemistry of submarine groundwater discharge  

USGS Publications Warehouse

To investigate the role of the seepage zone in transport, chemical speciation, and attenuation of nitrogen loads carried by submarine groundwater discharge, we collected nearshore groundwater samples (n = 328) and examined the distribution and isotopic signature (??15N) of nitrate and ammonium. In addition, we estimated nutrient fluxes from terrestrial and marine groundwater sources. We discuss our results in the context of three aquifer zones: a fresh groundwater zone, a shallow salinity transition zone (STZ), and a deep STZ. Groundwater plumes containing nitrate and ammonium occurred in the freshwater zone, whereas the deep STZ carried almost exclusively ammonium. The distributions of redox-cycled elements were consistent with theoretical thermodynamic stability of chemical species, with sharp interfaces between water masses of distinct oxidation : reduction potential, suggesting that microbial transformations of nitrogen were rapid relative to dispersive mixing. In limited locations in which overlap occurs between distribution of nitrate with that of ammonium and dissolved Fe2+, changes in concentration and in ??15N suggest loss of all species. Concurrent removal of NO 3- and NH4+, both in freshwater and the deep STZ, might occur through a range of mechanisms, including heterotrophic or autotrophic denitrification, coupled nitrfication : denitrification, anammox, or Mn oxidation of NH4+. Loss of nitrogen was not apparent in the shallow STZ, perhaps because of short water residence time. Despite organic C-poor conditions, the nearshore aquifer and subterranean estuary are biogeochemically active zones, where attenuation of N loads can occur. Extent of attenuation is controlled by the degree of mixing of biogeochemically dissimilar water masses, highlighting the critical role of hydrogeology in N biogeochemistry. Mixing is related in part to thinning of the freshwater lens before discharge and to dispersion at the fresh : saline groundwater interface, features common to all submarine groundwater discharge zones. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

Kroeger, K. D.; Charette, M. A.

2008-01-01

283

Submarine Maneuvers Prediction using Recursive Neural Networks  

Microsoft Academic Search

Recursive neural networks (RNNs) are a technique for developing time-dependent, nonlinear equation systems. In this paper, we applied RNN to simulate the maneuvers of submarine. The forces and moments acting on the body of submarine are functions of the motion state variables. Component force modules is developed to calculate five component forces as inputs to the recursive neural networks. These

Hassan Fahmy Hashem; Alexandria HighInstitute

2006-01-01

284

Research on Submarine Maneuverability of Flooded Compartment  

Microsoft Academic Search

The paper establishes the emergency recovery maneuver motion model. According to the characteristic of hydrodynamics coefficients on flooded submarine, attaining hydrodynamics coefficients of different angle of attack by limited ship model hydrodynamics experiment of large angle of attack. A sensitivity index is introduced to evaluate submarine's controllability. The experiment results are regressed to two kinds of hydrodynamic coefficients for big

Liu Hui; Pu Jinyun; Jin Tao

2009-01-01

285

Submarine landslides around the Canary Islands  

Microsoft Academic Search

The morphology and structure of the submarine flanks of the Canary Islands were mapped using the GLORIA long-range side-scan sonar system, bathymetric multibeam systems, and sediment echosounders. Twelve young (<2 Ma) giant landslides have been identified on the submarine flanks of the Canary Islands up to now. Older landslide events are long buried under a thick sediment cover due to

Sebastian Krastel; Hans-Ulrich Schmincke; Colin L. Jacobs; Roland Rihm; Timothy P. Le Bas; Bárbara Alibés

2001-01-01

286

Third World Submarine Threat - Another Great Equalizer.  

National Technical Information Service (NTIS)

This paper examines the growing submarine capability in the third world and the possible impact on the U.S. Navy's ability to execute its deterrence, sea control, and power projection missions in the near future. The effect of submarines on a naval force ...

F. C. Lawton

1991-01-01

287

Sediment-laden flow induced submarine cable failures off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Taiwan is located on the convergent boundary between the Eurasian and Philippine Sea plates, where has a highly frequency of earthquakes. Furthermore, the interaction between the largest continent (Eurasia Continent) and ocean (Pacific Ocean) leads to torrential-rain-induced flooding in the plume rain (May-June) and typhoon seasons (July-October). According to statistics from Water Resources Agency, in the last few decades, the mean annual sediment load was 384 million tons from the island of Taiwan into the sea. Off southwestern Taiwan, two major submarine canyons, the Gaoping submarine canyon (GPSC) and Fangliao submarine canyon (FLSC), are incising from continental shelf to deep sea floor and both of them transport considerable amounts of sediment to the South China Sea. In contrast to the GPSC which is directly connected to the Gaoping River, the FLSC which is smaller, younger and confined to the slope, does not associate with any river on land. Since 2006, southern Taiwan has been through several big typhoons and earthquakes which triggered submarine landslides and turbidity currents and damaged many submarine cables. The analytical results from sediment cores which taken from the GPSC and FLSC during 2005 to 2010 show these submarine cable break events may caused by different processes. In the upper GPSC, hyperpycnal flow might be the major process which caused the cable damages. On the contrary, cable failures in FLSC are due to sediment liquefaction.

Cheng, Y.; Su, C. C.

2012-04-01

288

Historically Active Volcanoes in Alaska - A Quick Reference  

NSDL National Science Digital Library

This United States Geological Survey (USGS) fact sheet summarizes historical data (from 1760 to 1999) on 41 Alaskan volcanoes, using information drawn from the more thorough and comprehensive USGS Open-File Report 98-582. Summaries include the volcano type, location (latitude and longitude), location on USGS quadrangle map, and any information available about the dates of eruptions and type of volcanic activity that occurred. Some volcanoes covered include Trident, Redoubt, Wrangell, Katmai, Cleveland, Kiska and more. A downloadable, printable version is available.

289

Complete data listings for CSEM soundings on Kilauea Volcano, Hawaii  

SciTech Connect

This document contains complete data from a controlled-source electromagnetic (CSEM) sounding/mapping project at Kilauea volcano, Hawaii. The data were obtained at 46 locations about a fixed-location, horizontal, polygonal loop source in the summit area of the volcano. The data consist of magnetic field amplitudes and phases at excitation frequencies between 0.04 and 8 Hz. The vector components were measured in a cylindrical coordinate system centered on the loop source. 5 references.

Kauahikaua, J.; Jackson, D.B.; Zablocki, C.J.

1983-01-01

290

AVO: Alaska Volcano Observatory  

NSDL National Science Digital Library

This site illustrates the Alaska Volcano Observatory's (AVO) objective to monitor Alaska's volcanoes for the purpose of forecasting volcanic activity and alleviating hazards. AVO's seismometers and satellite imagery allow visitors to obtain current information on selected volcanoes. Because AVO is responsible for volcanic emergencies, people in Alaska can visit the Web site to determine their vulnerability. The site also features AVO's research in geological mapping, modeling of magnetic systems, and development of new instrumentation for predication and interpretation of volcanic unrest. Everyone can appreciate the images of past volcanic eruptions.

291

Submarine evidence for large-scale debris avalanches in the Lesser Antilles Arc  

NASA Astrophysics Data System (ADS)

Results from a recent marine geophysical survey demonstrate the importance of the process of flank collapse in the growth and evolution of volcanoes along an island arc. The Aguadomar cruise, aboard the French R/V L'Atalante, surveyed the flanks of the Lesser Antilles Arc between the islands of Montserrat and St. Lucia. Analysis of the data shows that flank collapse events occurred on active volcanoes all along the arc and resulted in debris avalanches, some of them being of large magnitude. The debris avalanche deposits display hummocky topography on the swath bathymetry, speckled pattern on backscatter images, hyperbolic facies on 3.5 kHz echosounder data and chaotic units on air gun seismic profiles. They extend from horseshoe-shaped structures previously identified on the subaerial part of the volcanoes. In the southern part of the arc, large-scale debris avalanche deposits were identified on the floor of the Grenada Basin west of active volcanoes on Dominica, Martinique and St. Lucia. The extent of debris avalanche deposits off Dominica is about 3500 km2. The debris avalanches have resulted from major flank collapse events which may be mainly controlled by the large-scale structure of the island arc and the presence of the deep Grenada Basin. In the northern part of the arc, several debris avalanche deposits were also identified around the island of Montserrat. With smaller extent (20-120 km2), they are present on the east, south and west submarine flanks of Soufriere Hills volcano which has been erupting since July 1995. Flank collapse is thus a recurrent process in the recent history of this volcano. The marine data are also relevant for a discussion of the transport mechanisms of debris avalanches on the seafloor surrounding a volcanic island arc.

Deplus, C.; Le Friant, A.; Boudon, G.; Komorowski, J.-C.; Villemant, B.; Harford, C.; Ségoufin, J.; Cheminée, J.-L.

2001-10-01

292

Studies on formation mechanism and source depth of mud volcanoes by using of drilling cores in the Kumano forearc basin, SW Japan  

Microsoft Academic Search

Submarine mud volcanoes are formed as conical mounds composed of erupted unconsolidated or partially consolidated sediments from mud diapirs which are induced by high pore-fluid pressure and buoyancy developed in the deep underground. Most of them were discovered around subduction zones. Mud diapir that brings deep underground materials to seafloor has an important role for material circulations in subduction zones.

S. Muraoka; J. Ashi; T. Kanamatsu; A. Sakaguchi; F. Inagaki

2010-01-01

293

Sustaining U.S. Nuclear Submarine Design Capabilities. Executive Summary.  

National Technical Information Service (NTIS)

The U.S. submarine eet currently numbers more than 50 fast attack submarines (SSNs) and 18 submarines built to launch ballistic missiles (SSBNs). All are nuclear powered to maximize the duration and speed of underwater operations. While the submarine eet ...

J. Riposo J. F. Schank K. Curry M. V. Arena P. DeLuca

2007-01-01

294

Ups and downs on spreading flanks of ocean-island volcanoes: Evidence from Mauna Loa and Ki??lauea  

USGS Publications Warehouse

Submarine-flank deposits of Hawaiian volcanoes are widely recognized to have formed largely by gravitationally driven volcano spreading and associated landsliding. Observations from submersibles show that prominent benches at middepths on flanks of Mauna Loa and Kilauea consist of volcaniclastic debris derived by landsliding from nearby shallow submarine and subaerial flanks of the same edifice. Massive slide breccias from the mature subaerial tholeiitic shield of Mauna Loa underlie the frontal scarp of its South Kona bench. In contrast, coarse volcaniclastic sediments derived largely from submarine-erupted preshield alkalic and transitional basalts of ancestral Kilauea underlie its Hilina bench. Both midslope benches record the same general processes of slope failure, followed by modest compression during continued volcano spreading, even though they record development during different stages of edifice growth. The dive results suggest that volcaniclastic rocks at the north end of the Kona bench, interpreted by others as distal sediments from older volcanoes that were offscraped, uplifted, and accreted to the island by far-traveled thrusts, alternatively are a largely coherent stratigraphic assemblage deposited in a basin behind the South Kona bench.

Lipman, P. W.; Eakins, B. W.; Yokose, H.

2003-01-01

295

Pavlof Volcano From Station  

NASA Website

Astronauts aboard the International Space Station (ISS) photographed this striking view of Pavlof Volcano on May 18, 2013. The oblique perspective from the ISS reveals the three dimensional structure of the ash plume, which is often obscured by the ...

296

Volcanoes in the Infrared  

NSDL National Science Digital Library

In this video adapted from KUAC-TV and the Geophysical Institute at the University of Alaska, Fairbanks, satellite imagery and infrared cameras are used to study and predict eruptions of volcanoes in the Aleutian Islands, Alaska.

Foundation, Wgbh E.

2009-02-27

297

Certification of a submarine design using fiber Bragg grating sensors  

NASA Astrophysics Data System (ADS)

Systems Planning and Analysis, Inc. (SPA) has recently planned, installed, and tested a fiber Bragg grating (FBG) strain sensor system to validate FEM predictions of a new submarine design undergoing American Bureau of Shipping (ABS) certification testing. Fiber optic triaxial, biaxial, and uniaxial gage locations were selected based on the FEM analysis. FBGs were placed on six optical fibers with two fibers (33 sensors) mounted internally to the hull and four fibers (64 sensors) mounted externally. Testing was performed by lowering the submarine to the design depth and recording strain measurements. The optical sensor signals were transmitted directly to the water's surface and monitored by top-side interrogation instrumentation through over 2000 feet of optical cable. Measured temperature-compensated strain values were compared to the FEM predicted strain values with excellent results. To the author's knowledge, this successful test represents the first time that FBG sensors have been used to certify a submarine design and to validate FEM analysis on a large-scale structure.

Kiddy, Jason S.; Baldwin, Chris S.; Salter, Toni J.

2004-07-01

298

A distal earthquake cluster concurrent with the 2006 explosive eruption of Augustine Volcano, Alaska  

Microsoft Academic Search

Clustered earthquakes located 25 km northeast of Augustine Volcano began about 6 months before and ceased soon after the volcano's 2006 explosive eruption. This distal seismicity formed a dense cluster less than 5 km across, in map view, and located in depth between 11 km and 16 km. This seismicity was contemporaneous with sharply increased shallow earthquake activity directly below the volcano's vent. Focal mechanisms

Michael A. Fisher; Natalia A. Ruppert; Randall A. White; Frederic H. Wilson; Drew Comer; Ray W. Sliter; Florence L. Wong

2009-01-01

299

Volcano Watch Satellite Images  

NSDL National Science Digital Library

The University of Wisconsin's Space Science and Engineering Center displays these satellite images of the world's ten most active volcanoes. Users can view images of the Colima Volcano in Central Mexico or Mount Etna in Sicily, Italy. The latest images are updated every half-hour. Also, a Java animation feature splices together the last four images to show a simulation over a two-hour period.

300

Volcano Monitoring Techniques  

NSDL National Science Digital Library

This site introduces the several methods geologists use to monitor changes in a volcano. These methods assist in forecasting intrusions and eruptions and consist of ground movements, seismicity, gas geochemistry, and geology. As a result of this lesson, students will realize that eruptions have precursor activities, recognize patterns in volcano behavior, and interpret graphical data. This site includes fifteen activities that range from kindergarten to the twelfth grade level and include required material and worksheets.

301

Tephra layers: A controlling factor on submarine translational sliding?  

NASA Astrophysics Data System (ADS)

Submarine slope failures occur at all continental margins, but the processes generating different mass wasting phenomena remain poorly understood. Multibeam bathymetry mapping of the Middle America Trench reveals numerous continental slope failures of different dimensions and origin. For example, large rotational slumps have been interpreted to be caused by slope collapse in the wake of subducting seamounts. In contrast, the mechanisms generating translational slides have not yet been described. Lithology, shear strength measurements, density, and pore water alkalinity from a sediment core across a slide plane indicate that a few centimeters thick intercalated volcanic tephra layer marks the detachment surface. The ash layer can be correlated to the San Antonio tephra, emplaced by the 6000 year old caldera-forming eruption from Masaya-Caldera, Nicaragua. The distal deposits of this eruption are widespread along the continental slope and ocean plate offshore Nicaragua. Grain size measurements permit us to estimate the reconstruction of the original ash layer thickness at the investigated slide. Direct shear test experiments on Middle American ashes show a high volume reduction during shearing. This indicates that marine tephra layers have the highest hydraulic conductivity of the different types of slope sediment, enabling significant volume reduction to take place under undrained conditions. This makes ash layers mechanically distinct within slope sediment sequences. Here we propose a mechanism by which ash layers may become weak planes that promote translational sliding. The mechanism implies that ground shaking by large earthquakes induces rearrangement of ash shards causing their compaction (volume reduction) and produces a rapid accumulation of water in the upper part of the layer that is capped by impermeable clay. The water-rich veneer abruptly reduces shear strength, creating a detachment plane for translational sliding. Tephra layers might act as slide detachment planes at convergent margins of subducting zones, at submarine slopes of volcanic islands, and at submerged volcano slopes in lakes.

Harders, Rieka; Kutterolf, Steffen; Hensen, Christian; Moerz, Tobias; Brueckmann, Warner

2010-05-01

302

BrO formation in the plume of Pacaya volcano, plume chemistry at high resolution plume ages  

Microsoft Academic Search

During February 2010 we carried out gas emission studies of the plume of Pacaya volcano (Guatemala). The subduction zone volcano Pacaya which is characterized by basaltic to basaltic andesitic lava is located 40 km south of Guatemala City. Recent unrest from this volcano consisted of several events in the last decades in form of lava flows and strombolian explosions as

N. Bobrowski; L. Vogel; V. R. Cáceres Espinosa; C. Kern; U. Platt

2010-01-01

303

Is submarine groundwater discharge predictable?  

NASA Astrophysics Data System (ADS)

The contribution of submarine groundwater discharge (SGD) to the total hydrological discharges to the sea may be large but has been difficult to quantify. We have tested the applicability and generality of a suggested linear relationship between annual average total SGD and its fresh groundwater component against various SGD simulation results and field data. This relationship is found to constitute a general attractor for hydrologically simulated and directly measured SGD values across a wide range of conditions and world regions. But these consistent SGD quantifications differ systematically and largely from indirect SGD interpretations of tracers in seawater. This is an essential gap between inland- and sea-based methods of SGD estimation that needs to be bridged.

Prieto, Carmen; Destouni, Georgia

2011-01-01

304

Tried and True: Volcano r�sum�s  

NSDL National Science Digital Library

Tired of building a paper m�ch� volcano to teach about plate tectonics? Do you want to connect science and writing? Then the volcano r�sum� project is perfect for you. This one-week, problem-based learning (PBL) project requires students to research a specific volcano and then create a r�sum� for it that describes its location, physical characteristics, eruption history, and additional information of interest. Students are also required to include references for the information included on their r�sum�s.

Corlett, Cindy; Rutherford, Sandra

2008-03-01

305

CHALLENGES POSED BY RETIRED RUSSIAN NUCLEAR SUBMARINES  

SciTech Connect

The purpose of this paper is to provide an overview of the challenges posed by retired Russian nuclear submarines, review current U.S. and International efforts and provide an assessment of the success of these efforts.

Rudolph, Dieter; Kroken, Ingjerd; Latyshev, Eduard; Griffith, Andrew

2003-02-27

306

Improved Submarine Deployed Sea-State Sensor.  

National Technical Information Service (NTIS)

The invention relates generally to the field of electronic sensing devices, and more particularly to sensors for sensing selected conditions on an ocean surface. The invention specifically provides a sensor which may be deployed by a submarine or other su...

D. Shonting J. R. Knox

1996-01-01

307

Submarine Deployed Sea-State Sensor.  

National Technical Information Service (NTIS)

A submarine deployed sea state sensor comprises an elongated housing having a nose cone and an aft end, the housing having a forward buoyant chamber for receiving an accelerometer. Aft of the buoyant chamber, a damping assembly communication link deployme...

D. H. Shonting

1996-01-01

308

Crisis stability of a submarine deterrent.  

National Technical Information Service (NTIS)

Without defenses, stability indices fall monotonically as the number of submarine-launched ballistic missiles (SLBMs) is reduced. For few SLBMs, the favorable stability properties of the survivable SLBMs are masked by the unfavorable stability properties ...

G. H. Canavan

1992-01-01

309

Seismic reflections associated with submarine gas hydrates.  

National Technical Information Service (NTIS)

Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom ...

K. Andreassen

1995-01-01

310

Eyecup Assembly for a Submarine Periscope.  

National Technical Information Service (NTIS)

An eyecup assembly for a submarine periscope blinder assembly includes an annularly-shaped ring having a multiplicity of holes, which are unthreaded, extending therethrough and adapted to receive screws for securing the eyecup assembly to a like multiplic...

W. C. Macieiewski R. Sayegh

2000-01-01

311

Volcano Flank Terraces on Mars  

NASA Astrophysics Data System (ADS)

Flank terraces are bulge-like structures that occur on the slopes of at least nine large shield volcanoes on Mars, and three on Earth. Terraces have a convex-upward, convex-outward morphology, with an imbricate "fish scale" stacking pattern in plan. They occur at all elevations, are scale-invariant structures, and have similar proportions to thrust faults on Earth. Suggested mechanisms of formation include elastic self-loading, lithospheric flexure, magma chamber tumescence, flank relaxation, and shallow gravitational slumping. Terrace geometries predicted by most of these mechanisms do not agree with our observations, however. Only lithospheric flexure can fully account for terrace geometry on Mars and Earth, and so is the most likely candidate mechanism for flank terrace formation. To verify this hypothesis, we conducted scaled analogue modelling experiments, and investigated the structures formed during flexure. Cones of a sand-gypsum mix were placed upon a deep layer of silicone gel, to simulate volcanic loads upon viscoelastic Martian crust. Key parameters were varied across our experimental program. In all cases convex topographic structures developed on the cones' flanks, arranged in an imbricate, overlapping plan-view pattern. These structures closely resemble flank terraces observed on Mars, and our results provide for a basic kinematic model of terrace formation. Analogue volcanoes experienced a decrease in upper surface area whilst volume was conserved; the contractional surface strain was accommodated by outward verging, circumferentially striking thrusts. The morphology of experimental structures suggests an orientation of the principal stress axes of ?1 = radial, ?2 = concentric, and ?3 = vertical. Elsewhere (J. B. Murray et al., this volume) we detail the relationship between flank terraces and other structures such as pit craters and gräben, using Ascraeus Mons as a case study. We suggest that terraces may influence the distribution and location of these other structures, and thus play a fundamental role in the tectonic development of large shield volcanoes on Mars.

Byrne, P. K.; van Wyk de Vries, B.; Murray, J. B.; Troll, V. R.

2008-12-01

312

Volcanoes: Coming Up from Under.  

ERIC Educational Resources Information Center

|Provides specific information about the eruption of Mt. St. Helens in March 1980. Also discusses how volcanoes are formed and how they are monitored. Words associated with volcanoes are listed and defined. (CS)|

Science and Children, 1980

1980-01-01

313

Personality characteristics of successful Navy submarine personnel.  

PubMed

This study evaluated the personality characteristics of senior enlisted and occupationally successful Navy submarine personnel. One hundred subjects completed the Schedule for Nonadaptive and Adaptive Personality (SNAP). Results indicated that the traits of detachment, propriety, and workaholism were most descriptive of the sample. Thirty-seven percent met SNAP criteria for a personality disorder, typically antisocial, obsessive-compulsive, or avoidant. The results are discussed in terms of adaptation to environmental demands aboard submarines. Suggestions for further research are offered. PMID:8935516

Moes, G S; Lall, R; Johnson, W B

1996-04-01

314

Investigating the Source Mechanism of Long Period Volcano-Seismic Events Recorded in 2009 at Turrialba Volcano, Costa Rica  

NASA Astrophysics Data System (ADS)

Long-period (LP) seismic events (with energy concentrated between frequencies of 0.5 to 5Hz) were recorded on Turrialba volcano, Costa Rica during a field experiment from March to September 2009. This type of event has been recorded at many volcanoes across the world and in some instances swarms of LP events have signalled the onset of a volcanic eruption. The most widely accepted models for the source mechanism of these events attribute them to resonance within a fluid-filled cavity within the volcano, due to the similarity between waveforms of different LP events suggesting a non-destructive, repeatable source. Therefore inverting recorded LP events for the source mechanism can provide valuable information about the internal structure and dynamics of the volcano. Turrialba volcano is an ideal volcano on which to carry out this experiment because of the relatively easy and safe access to the volcano summit. This is important because it has been shown in previous studies that seismometers should be located in a dense network across the summit of a volcano (above the source), in order to gain as accurate a source inversion as possible. Activity at Turrialba volcano has increased dramatically in recent years with high levels of seismic and fumerolic activity. In this study 16 broadband seismometers were deployed on the summit and flanks of the volcano, including a 5 station array that was in operation for ~2 weeks. The data from the field experiment has been analysed and the LP events found. These were sorted into five families based on their correlations. The source locations have been calculated using a variety of methods including first picks, array analysis and a gridsearch implemented while carrying out moment tensor inversion. The LP events are located below the summit craters at shallow depth. These locations were then used to carry out full waveform moment tensor inversion to constrain the source mechanism, using a full waveform method to calculate the Green's functions. From unconstrained inversion, the optimum source for LP events is a crack mechanism. Constrained inversion will be carried out to better constrain the orientation of the crack. This will lead to a much greater understanding of the magmatic and hydrothermal systems within Turrialba volcano and better constraints on LP event source mechanism within volcanoes in general.

Eyre, T. S.; Bean, C. J.; O'Brien, G. S.; Martini, F.; Mora, M. M.; Pacheco, J. F.; Soto, G. J.

2011-12-01

315

Size distributions and failure initiation of submarine and subaerial landslides  

NASA Astrophysics Data System (ADS)

Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental slope follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediments does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslide sources along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude ? 6.3. Regions of submarine landslides, whose area distributions obey inverse power laws, may be controlled by different generation mechanisms, such as the gradual development of fractures in the headwalls of cliffs. The observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly-dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides. The area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area, not by the initiation process.

ten Brink, U. S.; Barkan, R.; Andrews, B. D.; Chaytor, J. D.

2009-09-01

316

Gas hydrate accumulation at the Håkon Mosby Mud Volcano  

Microsoft Academic Search

Gas hydrate (GH) accumulation is characterized and modeled for the Håkon Mosby mud volcano, ca. 1.5?km across, located on\\u000a the Norway–Barents–Svalbard margin. Pore water chemical and isotopic results based on shallow sediment cores as well as geothermal\\u000a and geomorphological data suggest that the GH accumulation is of a concentric pattern controlled by and formed essentially\\u000a from the ascending mud volcano

G. D. Ginsburg; A. V. Milkov; V. A. Soloviev; A. V. Egorov; G. A. Cherkashev; P. R. Vogt; K. Crane; T. D. Lorenson; M. D. Khutorskoy

1999-01-01

317

Mt. Erebus: A Surprising Volcano: Grades K-1: Electronic Book  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. The text is written at a kindergarten through grade one reading level. This is an onscreen version that contains recorded narration allowing students to listen to the text as they read along. Highlighted vocabulary words have individually recorded definitions heard by clicking on the links.

Fries-Gaither, Jessica

318

From suspended particles to strata: The fate of terrestrial substances in the Gaoping (Kaoping) submarine canyon  

Microsoft Academic Search

The river–sea system consisting of the Gaoping (new spelling according to the latest government's directive, formerly spelled Kaoping) River (KPR), shelf, and Submarine Canyon (KPRSC) located off southern Taiwan is an ideal natural laboratory to study the source, pathway, transport, and fate of terrestrial substances. In 2004 during the flood season of the KPR, a system-wide comprehensive field experiment was

James T. Liu; Jia-Jang Hung; Hui-Ling Lin; Chih-An Huh; Chon-Lin Lee; Ray T. Hsu; Ya-Wen Huang; Joel C. Chu

2009-01-01

319

33 CFR 334.75 - Thames River, Naval Submarine Base New London, restricted area.  

Code of Federal Regulations, 2013 CFR

...Naval Submarine Base New London, restricted area...western edge of the dredged channel to a point located at latitude...the designated navigation channel may...edge of the designated channel and...notified by personnel of the New London...

2013-07-01

320

Preliminary Results of a Near-Bottom Integrated Seafloor and Water Column survey of Brothers volcano, Kermadec arc, Using the Autonomous Vehicle ABE  

NASA Astrophysics Data System (ADS)

Brothers volcano, located about 310 km NE of New Zealand along the magmatic front of the Kermadec arc, is one of the best studied intraoceanic arc submarine volcanoes. Its 3.0 x 3.5 km caldera is slightly elliptical, with the long axis oriented about N320°E and has more than 300 m relief from a rim at ~1500 m to a maximum depth of 1880 m in its NW corner. Two major hydrothermal systems were discovered on it in the late 1990s, a high temperature field (up to 302°C) on the NW wall and a lower temperature gas-rich system on the summits of a pair of dacitic cones that occupy the SE half of the caldera. Although the caldera and cones were partly explored by submersibles in 2004 and 2005, the base map, made with a surface ship multibeam, was not detailed enough to understand the context of the seafloor observations. We used the autonomous vehicle ABE launched and recovered from the R/V SONNE in July-August 2007 to conduct high resolution near-bottom surveys of the caldera and its hydrothermal systems using a multibeam sonar, magnetometer, and CTD. The caldera wall, the dacite cones and part of the flat caldera rim were mapped in 96 hours of survey time over 8 dives. In addition, very detailed water column surveys at lower altitude and closer line spacing were conducted over the two most intense hydrothermal sites (i.e., the NW caldera wall and the smaller dacite cone). Although the results are preliminary, there are obvious correlations between hydrothermal activity, wall geomorphology, structural lineations, and the magnetic signature. New hydrothermal sites were discovered on the uppermost NW rim of the caldera and on the SW wall. This new map, along with the previously collected suites of fluid, mineral and seafloor observations, provides a baseline for future monitoring of Brothers' hydrothermal and volcanic activity. It will also provide a better understanding of how the long-term interplay of hydrothermal and volcanic activity affects the geomorphic evolution of submarine arc volcanoes.

Embley, R. W.; de Ronde, C.; Davy, B.; Baker, E. T.; Resing, J. A.; Yoerger, D. R.; Merle, S. G.; Walker, S. L.

2007-12-01

321

U-Th/He Ages of HSDP-2 Submarine Samples  

NASA Astrophysics Data System (ADS)

Hawaiian lavas have been used to investigate the life-cycles of hotspot-traversing volcanoes. The ~ 3500m core recovered by the Hawaii Scientific Drill Project, phase 2 (HSDP-2) has proven invaluable in refinement of models that link plume structures and melting rates to subaerial growth and geochemical evolution. Accurate age dating of lavas is critical in linking geochemical observations to plume characteristics; however, young ages and potassium-poor lavas limit the precision of argon methods. The U-Th/He method on olivine phenocrysts has been used to successfully date Hawaiian post-shield alkali basalts and flood basalts from the Snake River Plain. We are applying the method to olivine-rich lithologies in the HSDP-2 core in an attempt to gain further information about the growth rates of Hawaiian volcanoes. Preliminary results indicate that the method could help refine the flow chronology, but that modifications to the analysis procedure may be necessary to optimize the results. A subaerial Mauna Kea tholeiitic basalt from 528m depth yields a U-Th/He age of 485 +/- 100 ka (sample SR0222), slightly older than expected based on previous determinations on stratigraphically bounding flows by the argon isochron method (Sharp et al., Gcubed, 2005). A submarine hyaloclastite sample from 2931m depth (SR930) yields a preliminary age of 650+/-100 ka, which agrees well with previous Ar measurements. A pillow lava, SR0964, was also investigated, but it yielded a complicated He release pattern and no age can be obtained. U and Th concentrations in olivine separates from all three samples are low (2.6 - 5.2 ppb U; 4.5 - 8.0 ppb Th). The submarine samples appear to have a substantial amount of magmatic helium still remaining in the olivine after in vacuo crushing, as evidenced by high R/Ra values in gas released at high temperature. Residual gas left after crushing may be up to 85% magmatic, which makes the determination of radiogenic He less accurate. Sulfur contents of glass from the host submarine lava samples are high, indicating that the lavas were incompletely degassed. Helium isotopic ratios measured from the crushing step are within error of previously published values (R/Ra = 12.4 and 12.9). Extreme R/Ra values in the 530° C pre-fusion extraction (R/Ra = 756 for SR0964 and 68 for SR0930) suggest that high-T degassing may preferentially release 3He. We are continuing a helium isotopic exploration of the lowermost 450m of HSDP-2, which will provide important information about He isotopes in the core of the Hawaiian plume, and focusing further U- Th/He investigations on samples with low-S glass.

Peterson, B. T.; Aciego, S. M.; Kennedy, B. M.; Depaolo, D. J.

2008-12-01

322

Dike intrusion associated with the 2000 eruption of Miyakejima Volcano, Japan  

NASA Astrophysics Data System (ADS)

The model for the 2000 dike intrusion event between Kozushima and Miyakejima volcano, Japan, was reinvestigated. After the sudden earthquake swarm in Miyakejima volcano, a dike intrusion of large volume was detected by the nationwide GPS network (Geonet). The displacements detected with GPS stations over an area with a radius of about 200 km shows a distribution that is consistent with the dike source being located near Miyakejima volcano.

Yamaoka, K.; Kawamura, M.; Kimata, F.; Fujii, N.; Kudo, T.

2005-03-01

323

Volcano-Tectonic History of the Island of Montserrat, West Indies, From Seismic Reflection Profiles  

NASA Astrophysics Data System (ADS)

Seismic reflection profiles provide a cross-sectional view of crustal layers and thus details about local sedimentation rates, chronology, and depositional materials. Based on seismic profiles collected as part of the SEA-CALIPSO seismic experiment, we apply this method to interpreting the volcanic and local tectonic history of the island of Montserrat, in the Lesser Antilles arc. In December 2007, the vessel RRS James Cook towed a tuned, 2600 cubic inch, 8-airgun array along encircling and radial lines around Montserrat. The airguns fired every 60 sec (approx. every 140 m) at a pressure of 2000 psi. The ship also towed a 600 m streamer consisting of 48 hydrophone channels. Over a period of 77 hours, the hydrophones recorded a total of 4414 shots. Onboard the ship, data were stacked to produce 26 seismic profiles. The profiles vary in length up to 15 km and allow interpretation up to a depth of approx. 2.5 km. The profiles from east of Montserrat reveal fans of coarse-grained debris flows and submarine pyroclastic flows that derive from both the older volcanic centers and the active Soufriere Hills Volcano (SHV). The flows form tapering wedges that have been overlain by younger sea-floor sediments. Older ( > 1 Ma) sedimentary rocks, containing multiple reflective layers, deflect downwards towards and beneath Montserrat, forming a moat into which the debris and pyroclastic flows have deposited. A sub-sediment volcanic basement is present offshore at approximately 1.5 km depth. Offshore on the west side of the island the prominent Belham valley fault can be traced trending NW. The new data suggest that the fault line has been active in the recent geological past; the fault has offset submarine deposits offshore and tectonic blocks onshore (Garibaldi Hill, St. Georges Hill, Roches Bluff), has caused the down-warping of ocean sediments on the east side of the island, and likely influenced the location of domes and feeding conduits at and adjacent to the SHV. Montserrat itself appears to be located at the SW boundary of a large half-graben.

Kenedi, C. L.; Sparks, S. J.; Dean, S.; Hammond, J.; Malin, P. E.; Minshull, T.; Paulatto, M.; Peirce, C.; Ryan, G.; Shalev, E.; Voight, B.

2008-12-01

324

Tech trek: Viewing volcanoes  

NSDL National Science Digital Library

Help students make real-world connections to Earth science concepts such as volcanoes with the help of modern technology. This article enumerates several websites where students can explore these forces of nature in a variety of ways - all from a safe distance!

Christmann, Edwin P.; Wighting, Mervyn J.; Lucking, Robert A.

2005-03-01

325

Geology of Kilauea volcano  

SciTech Connect

This paper summarizes studies of the structure, stratigraphy, petrology, drill holes, eruption frequency, and volcanic and seismic hazards of Kilauea volcano. All the volcano is discussed, but the focus is on its lower east rift zone (LERZ) because active exploration for geothermal energy is concentrated in that area. Kilauea probably has several separate hydrothermal-convection systems that develop in response to the dynamic behavior of the volcano and the influx of abundant meteoric water. Important features of some of these hydrothermal-convection systems are known through studies of surface geology and drill holes. Observations of eruptions during the past two centuries, detailed geologic mapping, radiocarbon dating, and paleomagnetic secular-variation studies indicate that Kilauea has erupted frequently from its summit and two radial rift zones during Quaternary time. Petrologic studies have established that Kilauea erupts only tholeiitic basalt. Extensive ash deposits at Kilauea's summit and on its LERZ record locally violent, but temporary, disruptions of local hydrothermal-convection systems during the interaction of water or steam with magma. Recent drill holes on the LERZ provide data on the temperatures of the hydrothermal-convection systems, intensity of dike intrusion, porosity and permeability, and an increasing amount of hydrothermal alteration with depth. The prehistoric and historic record of volcanic and seismic activity indicates that magma will continue to be supplied to deep and shallow reservoirs beneath Kilauea's summit and rift zones and that the volcano will be affected by eruptions and earthquakes for many thousands of years. 71 refs., 2 figs.

Moore, R.B. (Geological Survey, Denver, CO (United States). Federal Center); Trusdell, F.A. (Geological Survey, Hawaii National Park, HI (United States). Hawaiian Volcano Observatory)

1993-08-01

326

Chilean Volcano Eruption  

NASA Video Gallery

This animation includes visible and infrared imagery from GOES-13 that runs from June 4, 2011, at 1:45 p.m. EDT to June 6, 2011, at 10:45 a.m. EDT and shows the ash plume from the Puyehue-Cordón Caulle volcano in Chile (lower left) follow the wind shift from southeast to north. (no audio)

Robert Garner

2011-06-09

327

Open Architecture Framework for Improved Early Stage Submarine Design.  

National Technical Information Service (NTIS)

Could transparency between current disparate methods improve efficiency in early stage submarine design. Does the lack of transparency between current design methods hinder the effectiveness of early stage submarine design. This thesis proposes that coord...

E. A. Sewell

2010-01-01

328

Exercise Aboard Attack Submarines: Rationale and New Options.  

National Technical Information Service (NTIS)

Substantial scientific evidence supports the potential benefits of exercise for submariners: regular exercise improves many human functions that directly apply to submarine operations. These benefits include improved alertness, cognitive function, immune ...

D. E. Watenpaugh A. J. Quatroche J. Bertoline D. M. Fothergill

2004-01-01

329

Mathematical modelling of submarine landslide motion  

NASA Astrophysics Data System (ADS)

Mathematical modelling of submarine landslide motion The paper presents a mathematical model to calculate dynamic parameters of a submarine landslide. The problem of estimation possible submarine landslides dynamic parameters and run-out distances as well as their effect on submarine structures becomes more and more actual because they can have significant impacts on infrastructure such as the rupture of submarine cables and pipelines, damage to offshore drilling platforms, cause a tsunami. In this paper a landslide is considered as a viscoplastic flow and is described by continuum mechanics equations, averaged over the flow depth. The model takes into account friction at the bottom and at the landslide-water boundary, as well as the involvement of bottom material in motion. A software was created and series of test calculations were performed. Calculations permitted to estimate the contribution of various model coefficients and initial conditions. Motion down inclined bottom was studied both for constant and variable slope angle. Examples of typical distributions of the flow velocity, thickness and density along the landslide body at different stages of motion are given.

Burminskij, A.

2012-04-01

330

Continuous monitoring of volcanoes with borehole strainmeters  

NASA Astrophysics Data System (ADS)

Monitoring of volcanoes using various physical techniques has the potential to provide important information about the shape, size and location of the underlying magma bodies. Volcanoes erupt when the pressure in a magma chamber some kilometers below the surface overcomes the strength of the intervening rock, resulting in detectable deformations of the surrounding crust. Seismic activity may accompany and precede eruptions and, from the patterns of earthquake locations, inferences may be made about the location of magma and its movement. Ground deformation near volcanoes provides more direct evidence on these, but continuous monitoring of such deformation is necessary for all the important aspects of an eruption to be recorded. Sacks-Evertson borehole strainmeters have recorded strain changes associated with eruptions of Hekla, Iceland and Izu-Oshima, Japan. Those data have made possible well-constrained models of the geometry of the magma reservoirs and of the changes in their geometry during the eruption. The Hekla eruption produced clear changes in strain at the nearest instrument (15 km from the volcano) starting about 30 minutes before the surface breakout. The borehole instrument on Oshima showed an unequivocal increase in the amplitude of the solid earth tides beginning some years before the eruption. Deformational changes, detected by a borehole strainmeter and a very long baseline tiltmeter, and corresponding to the remote triggered seismicity at Long Valley, California in the several days immediately following the Landers earthquake are indicative of pressure changes in the magma body under Long Valley, raising the question of whether such transients are of more general importance in the eruption process. We extrapolate the experience with borehole strainmeters to estimate what could be learned from an installation of a small network of such instruments on Mauna Loa. Since the process of conduit formation from the magma sources in Mauna Loa and other volcanic regions should be observable, continuous high sensitivity strain monitoring of volcanoes provides the potential to give short time warnings of impending eruptions. Current technology allows transmission and processing of rapidly sampled borehole strain data in real-time. Such monitoring of potentially dangerous volcanoes on a global scale would provide not only a wealth of scientific information but also significant social benefit, including the capability of diverting nearby in-flight aircraft.

Linde, Alan T.; Sacks, Selwyn

331

Theory of NURBS and its application in submarine hull modeling  

Microsoft Academic Search

Submarine hull consists of complicated spatial freeform surface. During the development of submarine design, the design of its body is the important factor which will decide whether this design is successful or not. But the design of complex curve and curve surface is the core in the CAD of submarine body. It is the key skill to speed up the

Zhang Jing; He Qiwei; Feng Shaowei

2010-01-01

332

47 CFR 32.2424 - Submarine & deep sea cable.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Submarine & deep sea cable. 32.2424...Balance Sheet Accounts § 32.2424 Submarine & deep sea cable. (a) This...shall include the original cost of submarine cable and deep sea cable...

2009-10-01

333

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2013-07-01

334

47 CFR 32.2424 - Submarine & deep sea cable.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Submarine & deep sea cable. 32.2424...Balance Sheet Accounts § 32.2424 Submarine & deep sea cable. (a) This...shall include the original cost of submarine cable and deep sea cable...

2010-10-01

335

The mortality of Royal Naval submariners 1960-89  

Microsoft Academic Search

OBJECTIVES: To examine the mortality pattern of submariners in the Royal Navy to assess the long term effects on health of serving in submarines. Any specific cause of death which was increased was considered in advance to be of interest, but attention focused particularly on cancer mortality. METHOD: A mortality follow up study: 15 138 submariners who had conducted their

H Inskip; M Snee; L Styles

1997-01-01

336

Hazard maps of Colima volcano, Mexico  

NASA Astrophysics Data System (ADS)

Colima volcano, also known as Volcan de Fuego (19° 30.696 N, 103° 37.026 W), is located on the border between the states of Jalisco and Colima and is the most active volcano in Mexico. Began its current eruptive process in February 1991, in February 10, 1999 the biggest explosion since 1913 occurred at the summit dome. The activity during the 2001-2005 period was the most intense, but did not exceed VEI 3. The activity resulted in the formation of domes and their destruction after explosive events. The explosions originated eruptive columns, reaching attitudes between 4,500 and 9,000 m.a.s.l., further pyroclastic flows reaching distances up to 3.5 km from the crater. During the explosive events ash emissions were generated in all directions reaching distances up to 100 km, slightly affected nearby villages as Tuxpan, Tonila, Zapotlán, Cuauhtemoc, Comala, Zapotitlan de Vadillo and Toliman. During the 2005 this volcano has had an intense effusive-explosive activity, similar to the one that took place during the period of 1890 through 1900. Intense pre-plinian eruption in January 20, 1913, generated little economic losses in the lower parts of the volcano due to low population density and low socio-economic activities at the time. Shows the updating of the volcanic hazard maps published in 2001, where we identify whit SPOT satellite imagery and Google Earth, change in the land use on the slope of volcano, the expansion of the agricultural frontier on the east and southeast sides of the Colima volcano, the population inhabiting the area is approximately 517,000 people, and growing at an annual rate of 4.77%, also the region that has shown an increased in the vulnerability for the development of economic activities, supported by the construction of highways, natural gas pipelines and electrical infrastructure that connect to the Port of Manzanillo to Guadalajara city. The update the hazard maps are: a) Exclusion areas and moderate hazard for explosive events (rockfall) and pyroclastic flows, b) Hazard map of lahars and debris flow, and c) Hazard map of ash-fall. The cartographic and database information obtained will be the basis for updating the Operational Plan of the Colima Volcano by the State Civil & Fire Protection Unit of Jalisco, Mexico, and the urban development plans of surrounding municipalities, in order to reduce their vulnerability to the hazards of the volcanic activity.

Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Escudero Ayala, C. R.

2011-12-01

337

Complete Data Listings for CSEM Soundings on Kilauea Volcano, Hawaii.  

National Technical Information Service (NTIS)

This document contains complete data from a controlled-source electromagnetic (CSEM) sounding/mapping project at Kilauea volcano, Hawaii. The data were obtained at 46 locations about a fixed-location, horizontal, polygonal loop source in the summit area o...

J. Kauahikaua D. B. Jackson C. J. Zablocki

1983-01-01

338

Monitoring the Dynamic Properties of an active Mud Volcano in the West Nile Delta  

NASA Astrophysics Data System (ADS)

Large numbers of submarine mud volcanoes have been discovered in many different continental margin settings often associated with hydrocarbon provinces. They are characterized by fluid formation and fluidization processes occuring at depths of several kilometers below the seafloor which drive a complex system of interacting geochemical, geological and microbial processes. As mud volcanoes are natural leakages of oil and gas reservoirs, near-surface phenomena can be used for monitoring of processes at great depth. North Alex Mud Volcano (NAMV) in the West Nile Delta, apparently rooted at depths of more than 5 kilometers is the focus of an industry-funded research project using existing and newly developed observatory technologies to better understand and quantify the internal dynamics and its long-term variability in relation to underlying gas reservoirs. As it is known that the activity of mud volcanoes varies significantly over periods of months and weeks, the assessment of the activity of NAMV focuses on proxies of fluid and gas emanations. Since the initiation of the project in 2007 NAMV has arguably become one of the best-instrumented mud volcanoes worldwide with a network of observatories collecting permanent long-term records of chemical fluxes, seismicity, temperature, ground deformation, and methane concentration. We will report on the first results of CAT meter deployments to determine chemical fluxes and relate them to long-term records of temperature, deformation as evident from tiltmeter deployments, and seismicity from a local OBS network.

Brueckmann, W.; Tryon, M. D.; Bialas, J.; Feseker, T.; Lefeldt, M. R.

2009-12-01

339

The submarine South Sandwich arc: structure, instability and sediment wave formation  

NASA Astrophysics Data System (ADS)

The South Sandwich volcanic arc, in the South Atlantic, is one of the world’s prime examples of an intra-oceanic arc in an entirely oceanic setting, and is unaffected by collision or arc rifting. During the 2010 (cruise JR206) we succeeded in completing, for the first time, bathymetric mapping of the entire 650 km x 100 km submarine arc using multibeam sonar. The new survey shows that there are nine main volcanic centers and ca. twenty main seamounts in the 540 km long volcanic arc. The central seven volcanic centers are 3-3.5 km high and emerge as the main South Sandwich Islands. The northernmost center, around Protector Shoal, is an at least partly silicic cluster of seven stratovolcano seamounts and a 15 km diameter volcanic plateau. The southern Adventure center, which is 45 km across and 1.7 km high, is newly-discovered, and consists of a chain of seamounts and two submarine calderas. Seven distinct calderas are identified in both large centers and seamounts within the arc. There are also three 60 km long tectonically controlled, northwest-southeast-trending seamount chains that extend from the volcanic front to the rear of the arc. The volcanoes have been affected by a range of mass wasting phenomena, including debris avalanches, slumps, erosion at sea level and sediment dispersal by mass flows. There is abundant evidence of slope instability and landsliding of volcanoes during their initial stages of growth, when they form seamounts yet to rise above sea level. On the other hand, the forms of the emergent volcanoes indicate that they have only rarely collapsed to form large tsunamigenic landslides. There are abundant large, striking, wave-like structures that have wavelengths of 2-4 km and amplitudes of 50-150 m on the ca. 2°-3° submarine slopes of these volcanoes. TOPAS sub-bottom imagery shows stratified units in the wave-like structures that prograde downslope from wave crests and that can locally be traced from crest to crest, indicating that they are sediment waves, although modified by slumping. Sediment wave fields have central channels and originate from chutes connecting them to shallow shelves around the islands. The origin of the large volumes of sediment required to form the sediment wave fields is interpreted to result from high rates of coastal erosion. The emergent volcanoes are largely glaciated, with many glaciers discharging sediment at the coast. Coasts are unprotected from South Atlantic swell and dominated by eroding cliffs. Sediment on the shelves is discharged along the cutes as turbidity currents or other mass flows towards to sediment wave fields. The resulting thick piles of sediments on lower volcano flanks appear to have reduced slopes and hence increased slope stability.

Leat, P. T.; Tate, A. J.; Deen, T. J.; Day, S. J.; Owen, M.

2010-12-01

340

The Alaska Volcano Observatory - Expanded Monitoring of Volcanoes Yields Results  

USGS Publications Warehouse

Recent explosive eruptions at some of Alaska's 52 historically active volcanoes have significantly affected air traffic over the North Pacific, as well as Alaska's oil, power, and fishing industries and local communities. Since its founding in the late 1980s, the Alaska Volcano Observatory (AVO) has installed new monitoring networks and used satellite data to track activity at Alaska's volcanoes, providing timely warnings and monitoring of frequent eruptions to the aviation industry and the general public. To minimize impacts from future eruptions, scientists at AVO continue to assess volcano hazards and to expand monitoring networks.

Brantley, Steven R.; McGimsey, Robert G.; Neal, Christina A.

2004-01-01

341

Modelling the equilibrium bed topography of submarine meanders that exhibit reversed secondary flows  

NASA Astrophysics Data System (ADS)

Submarine meandering channels formed by turbidity currents are common; however, their location on the ocean floor and their inactive status make it difficult to measure process dynamics and bed morphology. Conceptual models have, therefore, instead been developed by analogy with the well understood mechanics of fluvial bends. However, unlike fluvial currents, in turbidity currents the downstream velocity maximum typically occurs near the bed and recent experimental and theoretical studies suggest that, under certain hydraulic and morphological conditions, this forces the secondary flow to exhibit the reverse sense to that encountered in fluvial bends. Herein the possible morphological implications of a reversal of secondary flow are explored by modelling the force balance on sediment grains moving through either (i) field and laboratory submarine meander bends that are known to exhibit 'reversed' secondary flows, or (ii) inactive submarine meander bends where the nature of the secondary flow in the formative turbidity currents can be inferred to be reversed. Exploratory simulations are undertaken for a single hypothetical submarine bend with morphological properties based on nine relic meanders observed on the floor of the Gulf of Alaska. Reconstructions of secondary flow properties within the Gulf of Alaska bends indicate that they likely exhibited reversed secondary flows. Results of the exploratory simulations indicate that, unlike typical fluvial meanders, the transverse bed profile gradient of the hypothetical bend is very low and the point bar is located downstream of the bend apex.

Darby, Stephen E.; Peakall, Jeff

2012-08-01

342

Stratigraphic reconstruction of the 13 ka BP debris avalanche deposit at Colima volcano (Mexico): effect of climatic conditions on the flow mobility  

Microsoft Academic Search

Colima volcano is an andesitic stratovolcano located in the western part of the Trans-Mexican Volcanic Belt (TMVB) and at the southern end of the N-S trending Colima graben, about 70 km from the Pacific Ocean coast. It is probably the most active Mexican volcano in historic time and one of the most active of North America. Colima volcano yielded numerous

M. Roverato; L. Capra

2010-01-01

343

Volatile Abundances and Magma Geochemistry of Recent (2006) Through Ancient Eruptions (Less Than 2100 aBP) of Augustine Volcano, Alaska  

Microsoft Academic Search

Augustine Volcano, Cook Inlet, Alaska, is a subduction-related Aleutian arc volcano located approximately 275 km southwest of Anchorage. During the past 200 years, Augustine volcano has shown explosive eruptive behavior seven times, with the most recent activity occurring in January through March 2006. Its ash and pumice eruptions pose a threat to commercial air traffic, the local fishing industry, and

J. D. Webster; C. W. Mandeville; T. Gerard; B. Goldoff; M. L. Coombs

2006-01-01

344

Mt. Erebus: A Surprising Volcano: Grades K-1: text only version  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. The reading level is at Kindergarten through grade one. This is a PDF containing the informational text and a glossary.

Fries-Gaither, Jessica

345

Isopach map and Characteristics of the Ashfall Deposits From Parícutin Volcano, (México)  

Microsoft Academic Search

Parícutin volcano belongs to the Michoacán-Guanajuato volcanic field located in the central portion of the state of Michoacán, in western Mexico, approximately 50 km northwest of the town of Uruapan. Parícutin is the famous Mexican volcano born in a cornfield in 1943 erupting until 1952, and has been the object of many studies since its birth up to now. In

J. Pérez Bustamant; H. Delgado Granados; C. Linares Lopez; A. Victoria Morales; I. A. Farraz Montes

2007-01-01

346

Submersible study of mud volcanoes seaward of the Barbados accretionary wedge: sedimentology, structure and rheology  

Microsoft Academic Search

In 1992, the Nautile went to a mud volcano field located east of the Barbados accretionary wedge near 13 ° 50N. Using nannofossil analysis on cores, we determined the sedimentation rate, and provided a new estimation of the age of the mud volcanoes (750,000 years for the oldest one). Six structures have been explored with the submersible Nautile, and manifestations

Sophie Lance; Pierre Henry; Xavier Le Pichon; Siegfried Lallemant; Hervé Chamley; Frauke Rostek; Jean-Claude Faugères; Eliane Gonthier; Karine Olu

1998-01-01

347

Volcanic Activity in Alaska: Summary of Events and Response of the Alaska Volcano Observatory, 1992.  

National Technical Information Service (NTIS)

During 1992, the Alaska Volcano Observatory (AVO) responded to 10 eruptions, episodes of eruptive activity, or false alarms at 8 volcanoes--Spurr, Redoubt, Iliamna, Mageik, Westdahl, Akutan, Bogoslof, and Seguam--located from upper Cook Inlet to 1770 km o...

C. A. Neal M. P. Doukas R. G. McGimsey

1995-01-01

348

Deformation of the Augustine Volcano, Alaska, 1992-2005, measured by ERS and ENVISAT SAR interferometry  

Microsoft Academic Search

The Augustine Volcano is a conical-shaped, active stratovolcano located on an island of the same name in Cook Inlet, about 290 km southwest of Anchorage, Alaska. Augustine has experienced seven significant explosive eruptions-in 1812, 1883, 1908, 1935, 1963, 1976, 1986, and in January 2006. To measure the ground surface deformation of the Augustine Volcano before the 2006 eruption, we applied

C.-W. Lee; Z. Lu; O.-I. Kwoun; J.-S. Won

2008-01-01

349

Catalog of Earthquake Hypocenters at Alaskan Volcanoes: January 1 through December 31, 2006.  

National Technical Information Service (NTIS)

Between January 1 and December 31, 2006, AVO located 8,666 earthquakes of which 7,783 occurred on or near the 33 volcanoes monitored within Alaska. Monitoring highlights in 2006 include: an eruption of Augustine Volcano, a volcanic-tectonic earthquake swa...

C. Searcy J. A. Power J. P. Dixon S. D. Stihler

2007-01-01

350

Estimates of Gas Flux From Infrasonic Recordings of Vulcanian Blasts at Augustine Volcano, Alaska  

Microsoft Academic Search

In January 2006, Augustine volcano awoke from nearly 20 years of quiescence. The 2006 eruption lasted nearly three months and included discrete explosive, continuous explosive and effusive phases. The eruption was well-monitored by the Alaska Volcano Observatory, with a network that included dense seismic and geodetic instrumentation. Co-located with one of the seismometers was a pressure sensor which captured the

J. Caplan-Auerbach; A. K. Bellesiles; J. J. Fernandes

2008-01-01

351

Mt. Erebus: A Surprising Volcano: Grades 2-3: text only version  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. The text is written at a grade two through grade three reading level. This is a PDF containing the informational text and a glossary.

Fries-Gaither, Jessica

352

Liquid Carbon Dioxide Venting at the Champagne Hydrothermal Site, NW Eifuku Volcano, Mariana Arc  

NASA Astrophysics Data System (ADS)

In March/April 2004, submersible dives with the remotely-operated vehicle ROPOS discovered an unusual CO2-rich hydrothermal system near the summit of NW Eifuku, a submarine volcano located at 21.49° N, 144.04° E in the northern Mariana Arc. Although several sites of hydrothermal discharge were located on NW Eifuku, the most intense venting was found at 1600-m depth at the Champagne site, slightly west of the volcano summit. The Champagne site was found to be discharging two distinct fluids into the ocean: a) several small white chimneys were emitting milky 103° C gas-rich hydrothermal fluid with at least millimolar levels of H2S and b) cold (< 4° C) droplets coated with a milky skin were rising slowly from the sediment. These droplets were later determined to consist mainly of liquid CO2, with H2S as a probable secondary component. The droplets were sticky, and did not tend to coalesce into larger droplets, even though they adhered to the ROV like clumps of grapes. The film coating the droplets was assumed to be CO2 hydrate (or clathrate) which is known to form whenever liquid CO2 contacts water under these P,T conditions. Samples of the 103° C hydrothermal fluids were collected in special gas-tight titanium sampling bottles that were able to withstand the high internal pressures created by the dissolved gases. The Champagne hydrothermal fluids contained a surprising 2.3 moles/kg of CO2, an order of magnitude higher than any CO2 values previously reported for submarine hydrothermal fluids. The overall gas composition was 87% CO2, < 0.1% CH4, < 2 ppm H2, 0.012 mM/kg 4He, with the remaining 13% (322 mM/kg) assumed to be sulfur gases (H2S, SO2, etc.). (Additional analyses planned will confirm the speciation of this sulfur gas component). The helium had R/RA = 7.3, typical of subduction zone systems (R = 3He/4He and RA = Rair). Isotopic analysis of the CO2 yielded ? 13C = -1.75 ‰ , much heavier than the -6.0 ‰ typical for carbon in MOR vent fluids. The C/3He ratio was ~2.2 x 1010, an order of magnitude higher than the average value of 2 x 109 found in MOR vent fluids. The ? 13C and C/3He values suggest a substantial contribution to the carbon from subducted carbonates rather than mantle carbon. The Champagne site is only the second locality where liquid CO2 has been observed venting into the deep sea (the other reported location is in the Okinawa Trough, see Sakai et al., 1990). Because of the presence of liquid CO2 in proximity to hydrothermal organisms, the Champagne site may prove to be a valuable natural laboratory for studying the effects of high CO2 concentrations on marine ecosystems.

Lupton, J.; Lilley, M.; Butterfield, D.; Evans, L.; Embley, R.; Olson, E.; Proskurowski, G.; Resing, J.; Roe, K.; Greene, R.; Lebon, G.

2004-12-01

353

Volcanoes, Third Edition  

NASA Astrophysics Data System (ADS)

It takes confidence to title a smallish book merely “Volcanoes” because of the impliction that the myriad facets of volcanism—chemistry, physics, geology, meteorology, hazard mitigation, and more—have been identified and addressed to some nontrivial level of detail. Robert and Barbara Decker have visited these different facets seamlessly in Volcanoes, Third Edition. The seamlessness comes from a broad overarching, interdisciplinary, professional understanding of volcanism combined with an exceptionally smooth translation of scientific jargon into plain language.The result is a book which will be informative to a very broad audience, from reasonably educated nongeologists (my mother loves it) to geology undergraduates through professional volcanologists. I bet that even the most senior professional volcanologists will learn at least a few things from this book and will find at least a few provocative discussions of subjects they know.

Nye, Christopher J.

354

Generation scenarios for Atlantic-region tsunamis: landslides and volcanos  

NASA Astrophysics Data System (ADS)

Significant historical and prehistoric tsunami activity in the Atlantic and in the peripheral Caribbean and Mediterranean Basins has often been associated with volcanic activity. Landslides from continental shelf margins and from undersea trenches have also contributed. These none-earthquake sources probably contribute more tsunamis to the Atlantic basin than earthquakes do, in contrast to the more earthquake- prone Pacific and Indian Oceans. (Of course one must always remember the devastating Lisbon earthquake tsunami of 1755). For the Atlantic region it is therefore important to better understand the ways in which volcanos and landslides produce tsunamis, and to that end I present simulations of tsunami generation mechanisms in the context of subaerial landslides (as in the Canary and Cape Verde Islands), submarine landslides (as in Caribbean trenches and continental shelf margins), and by hydromagmatic activity (as in the Caribbean and Iceland). I will also briefly discuss the unlikely danger posed by asteroid-impact tsunamis.

Gisler, G. R.

2008-12-01

355

Preliminary radon measurements at Villarrica volcano, Chile  

NASA Astrophysics Data System (ADS)

We report data from a radon survey conducted at Villarrica volcano. Measurements have been obtained at selected sites by E-PERM® electrets and two automatic stations utilizing DOSEman detectors (SARAD Gmbh). Mean values for Villarrica are 1600 (±1150) Bq/m3 are similar to values recorded at Cerro Negro and Arenal in Central America. Moderately higher emissions, at measurement sites, were recorded on the NNW sector of the volcano and the summit, ranging from 1800 to 2400 Bq/m3. These measurements indicate that this area could potentially be a zone of flank weakness. In addition, the highest radon activities, up to 4600 Bq/m3, were measured at a station located near the intersection of the Liquiñe-Ofqui Fault Zone with the Gastre Fault Zone.

Cigolini, C.; Laiolo, M.; Coppola, D.; Ulivieri, G.

2013-10-01

356

Gelatin Volcanoes: Student Page  

NSDL National Science Digital Library

This is the Student Page of an activity that teaches students how and why magma moves inside volcanoes by injecting colored water into a clear gelatin cast. The Student Page contains the activity preparation instructions and materials list, key words, and a photograph of the experimental setup. There is also an extension activity question that has students predict what will happen when the experiment is run using an elongated model. This activity is part of Exploring Planets in the Classroom's Volcanology section.

357

Buried Rift Zones and Seamounts in Hawaii: Implications for Volcano Tectonics  

NASA Astrophysics Data System (ADS)

As volcanoes grow, they deform due to their own weight and ongoing magmatic intrusions. For example, Kilauea's south flank is moving seaward ~10 cm/yr, apparently pushed by dike injection along rift zones and/or gravitational spreading. Offshore, Kilauea's south flank has developed a broad bench, attributed to overthrusting at the toe of the mobile flank. Mauna Loa's southeastern flank is much less mobile today, and exhibits no offshore bench. The great variability in present-day surface motions and deformation of these two volcanoes is not well explained by the distribution of surface structures, which might influence the driving and resisting forces acting on the flanks. Using first-arrival seismic tomography of a unique onshore-offshore airgun dataset, we have developed a 3-D P-wave velocity model of the southeastern part of the Island of Hawaii. This model provides an unprecedented view into both the submarine and subaerial portions of Kilauea, Mauna Loa, and Loihi volcanoes, helping to resolve some outstanding puzzles. The preferred velocity model shows that the known summits and rift zones of Kilauea, Mauna Loa and Loihi volcanoes are underlain by high velocity anomalies (6.5-7.0 km/s), indicating the presence of intrusive magma cumulates and dike complexes. In addition, we observe an anomalously high velocity feature (7.0-7.5 km/s) within the southeastern flank of Mauna Loa that extends ~40 km south of the volcano's summit. Our model also shows anomalously high velocity materials (6.3-6.8 km/s) in the oceanic crust beneath Kilauea's outer bench. Based on the geometry of their high velocities, we propose that these features represent previously unrecognized intrusive complexes that have influenced the evolution of the two volcanoes. The high velocity feature within Mauna Loa's southeastern flank appears to represent a buried rift zone, either of ancient Mauna Loa, or an older volcano perhaps related to the Ninole Hills. Curiously, at shallow depths (5-9 km below sea level), the high velocities are sharply truncated to the south. However, at greater depths, the anomalously high velocities extend another 20 km into the submarine flank, distinguishing this feature as a once extensive rift zone. The presence of dense, coherent intrusive rock may have anchored Mauna Loa's southeastern flank, such that much of the volcano's recent deformation has occurred along the west flank of Mauna Loa. This massive rift zone may also impede the propagation of Kilauea's southwest rift zone, accounting for its lesser development relative to Kilauea's east rift zone. The velocity highs beneath Kilauea's submarine flank likely represent buried seamounts that might obstruct the seaward migration of volcano's south flank, causing the bench uplift at the toe of flank. These new observations lead us to propose that previously unrecognized intrusive complexes within Mauna Loa and Kilauea have significantly affected the past evolution of these volcanoes in the Island of Hawaii, and are likely responsible for the present patterns of deformation on these active volcanoes.

Park, J.; Morgan, J. K.; Zelt, C. A.; Okubo, P. G.

2005-12-01

358

New insights on Mafate - Saint Gilles debris avalanche deposits (westward Piton des Neiges volcano Réunion Island)  

NASA Astrophysics Data System (ADS)

Studies of debris avalanche deposits on Reunion Island (southwestern Indian Ocean) have been started in the last decade with the bathymetric surveys offshore Piton de la Fournaise and the identification of giant submarine landslides (Lénat et al., 1989; Cochonnat et al., 1990). Since this discovery, new field investigations have been driven to characterise and understand the role of debris avalanche phenomena in the evolution of volcanic island like Reunion. The first aerial outcrop of debris avalanche deposits has been identified in the west part of Piton des Neiges volcano in 1996. It has been described has a succession of breccia events interbedded by lava flows, and localised in St Gilles area (Bachèlery et al, 2003). In the last two years, the breccia problematic has been revisited and new outcrops have been found in the northern and southern part of St Gilles area (Bret et al., 2003). In the light of new geological surveys, new debris avalanche deposits outcrops have been identified around the St Gilles area. Most of these new outcrops are situated in the main riverbeds of the western Piton des Neiges flank (Rivière des Galets, Ravine Divon, Ravine Bernica and Ravine Trois Bassins). Furthermore, similar breccia outcrops has been identified down the Maïdo cliff, in the walls of Mafate cirque, uphill St Gilles area. All these formations show common characters of debris avalanche deposits with (i) a “block facies” consisting of plurimetric to decametric shattered lava flow and dykes segments with typical jigsaw fractures packed in (ii) a “matrix facies” composed of silty to sandy heterogeneous elements. This tends to prove that previous authors have underestimated the St Gilles event lateral extent. Our new field surveys point out the new extension (obvious landslide scars) of the St Gilles well known debris avalanche deposits. These scars start in the Mafate cirque (where the landslide head is located), then continue through the Mafate wall in the north of Maïdo place and go down to the sea from Ravine Trois Bassins in the south to Rivière des Galets in the north. These discoveries associated to recent submarine DEM interpretation (Oehler, 2001) allow us to consider a new global evolution sketch of the whole Piton des Neiges west flank with a large debris-avalanche (now called Mafate - St Gilles debris avalanche deposits) that has recovered the former basaltic Piton des Neiges topography at the end of the shield building stage (around: 0.45 My).

Fèvre, F.; Bret, B.; Odon, O.; Arnaud, A.; Bachèlery, B.

2003-04-01

359

First Use of an Autonomous Glider for Exploring Submarine Volcanism in the SW Pacific  

NASA Astrophysics Data System (ADS)

A 1000-m Slocum glider® (Teledyne Webb Research Corporation) with CTD, turbidity, and hydrophone sensors was operated for two days in the Northeast Lau Basin. The survey was conducted near West Mata Volcano, where in November of 2008 the NOAA PMEL Vents program observed an active eruption at its 1207 m summit—the deepest submarine activity ever before witnessed. Our goal was to use the glider as a forensic tool to search for other nearby eruption sites with onboard sensors that detect the chemical and hydroacoustic signatures associated with the volcanic and hydrothermal plumes. The glider was launched approximately 40 km to the west of West Mata. It flew toward West Mata and was recovered near the summit of the volcano after repeating 13 yos during a 41-hour mission. Although the recordings were affected by mechanical noise from the glider’s rudder, the data demonstrate that the system can detect the wide-band noises (>1 kHz) associated with submarine volcanic and intense hydrothermal activity. The glider recorded complex acoustic amplitudes due to the multiple raypaths from West Mata as well as temporal variations in the volcano’s rate of activity, and demonstrated that these geologic processes contribute to the region’s high ambient noise levels. With the exception of the deployment and recovery, the mission was managed entirely by the shore teams in PMEL (Seattle, WA) and OSU labs (Newport, OR), ~5000 miles away without an engineer onboard. The dive cycle of the 950-m dives was ~3.5 hours and the average speed was ~0.27 cm/s. The CTD data were downloaded at every surface cycle and appeared to be of high quality. However we found that the sensitivity of the Wetlabs ECO flntu turbidity sensor was not adequate for the detection of volcanic plumes. The mission demonstrated PMEL’s ability to use autonomous gliders to monitor a variety of environmental parameters including ambient sound levels, temperature, salinity and turbidity for the purpose of finding subsea volcanism. Our plan is to add a more sensitive turbidity sensor and design a near realtime interface between the NOAA’s acoustic system and glider.

Matsumoto, H.; Embley, R. W.; Haxel, J. H.; Dziak, R. P.; Bohnenstiehl, D. R.; Stalin, S.; Meinig, C.

2010-12-01

360

What Controls Submarine Groundwater Discharge?  

NASA Astrophysics Data System (ADS)

Numerous processes have been implicated in controlling submarine groundwater discharge (SGD) to coastal zones since Ghyben, Herzberg and Dupuit developed models of fresh water discharge from coastal aquifers at the turn of the 19th century. Multiple empirical and modeling techniques have also been applied to these environments to measure the flow. By the mid-1950's, Cooper had demonstrated that dispersion across the fresh water-salt water boundary required salt water entrained into fresh water flow be balanced by recharge of salt water across the sediment-water interface seaward of the outflow face. Percolation of water into the beach face from wind and tidal wave run up and changes in pressure at the sediment-water interface with fluctuating tides have now been recognized, and observed, as processes driving seawater into the sediments. Within the past few years, variations in water table levels and the 1:40 amplification from density difference in fresh water and seawater have been implicated to pump salt water seasonally across the sediment- water interface. Salt water driven by waves, tides and seasonal water table fluctuations is now recognized as a component of SGD when it flows back to overlying surface waters. None of these processes are sufficiently large to provide measured volumes of SGD in Indian River Lagoon, Florida, however, because minimal tides and waves exist, flat topography and transmissive aquifers minimize fluctuations of the water table, and little water is entrained across the salt water-fresh water boundary. Nonetheless, the saline fraction of SGD represents more than 99% of the volume of total SGD in the Indian River Lagoon. This volume of saline SGD can be driven by the abundance of burrowing organisms in the lagoon, which pump sufficient amounts of water through the sediment- water interface. These bioirrigating organisms are ubiquitous at all water depths in sandy sediment and thus may provide one of the major sources of SGD world wide. Because bioirrigated water is well oxygenated and passes through sedimentary pore spaces, its influence may be quite large on fluxes of diagenetic reactive components, including organic matter, nutrients, and redox sensitive metals. While fresh meteoric groundwater may be confined to the shoreline in most cases and delivers new material from continents to the ocean, seawater circulating through sediments as part of SGD is apparently a much greater fraction of the total water flux and hence has the potential to significantly impact sediment diagenetic processes and subsequent export of nutrients and other solutes from the sediment to the water column.

Martin, J. B.; Cable, J. E.; Cherrier, J.; Roy, M.; Smith, C. G.; Dorsett, A.

2008-05-01

361

KrakMon: Seismic signals recorded at Krakatau Volcano, Indonesia  

NASA Astrophysics Data System (ADS)

A recently installed multi-parameter monitoring system on the Krakatau volcanic island complex located in the Sunda Strait (Indonesia) provides continuous broadband records of seismic data. We present here an overview of the different signal types identified and first results of an automated detection and classification procedure for volcano-seismic events recorded at Krakatau volcano. In comparison to seismic signals known from other volcanoes, an unusually high portion of high-frequency content is observed in the spectra of the Krakatau signals. This observation applies to short-term volcano-tectonic (VT) events as well as to continuous tremor signals: most VT events show significant energy at frequencies above 30Hz, harmonic signals last almost continuously for days and show spectral peaks at distinct frequencies well above15Hz. The automated detection and classification procedure bases a spectrogram analysis of volcano-seismic signals using a straight-forward pattern recognition approach: a suitable threshold operator generates a binary representation of the spectrogram which is processed by a contour finding algorithm. The resulting contour-polygons define regions in the spectrogram containing significant spectral energy and their shapes reveal information about the respective volcano-seismic signals. By the extraction of stable shape-describing properties from the polygons and their statistical analysis it is attempted to identify different classes of signal types. A comparison of the resulting signal types with those determined visually by the operator can improve classification schemes for volcano-seismic signals and contribute to defining the activity status of Krakatau and other volcanoes.

Ibs-von Seht, M.; Hoffmann-Rothe, A.; Kniess, R.

2005-12-01

362

Nitrogen Dioxide Levels Aboard Nuclear Submarines.  

National Technical Information Service (NTIS)

The NO2 levels permitted aboard submarines are 0.5 ppm for 90 days, 1 ppm for 24 hours and 10 ppm for 1-hour. The 90 day limit 'represents an average value for continuous exposure which may be temporarily exceeded so long as there are corresponding period...

K. R. Bondi M. L. Shea R. M. DeBell

1983-01-01

363

Vitamin D Status of Submariners During Patrol.  

National Technical Information Service (NTIS)

The circulating vitamin D (25-OH-D) levels were measured in 22 submariners before, during and after a three month patrol. Eleven subjects received a multivitamin-mineral supplement that contained 10.0 mg of ergocalciferol while the other 11 received a pla...

C. L. Schlichting D. J. Styer

1989-01-01

364

Sliding of outrunner blocks from submarine landslides  

Microsoft Academic Search

Outrunner blocks are nearly intact pieces of debris that detach from a slowing-down submarine landslide and flow ahead of the front. Data gathered from different sliding areas highlight some properties of outrunner blocks and in particular their inordinate mobility reflected in runouts of up to 25 kilometres, even on very gentle slopes. Blocks may produce an erosion glide track on

Fabio Vittorio De Blasio; Lars Enok Engvik; Anders Elverhøi

2006-01-01

365

Monitoring corrosion in submarine sonar domes  

Microsoft Academic Search

The Applied Physics Laboratory at the University of Washington (APL-UW) and the Naval Sea Systems Command (NAVSEA) are involved in a long-term study to reduce corrosion in submarine sonar domes. Besides periodically inspecting the structures in tile domes and recommending improvements in their design, materials, and maintenance, APLUW has recently developed an instrument package to monitor selected parameters of the

C. J. Sandwith; R. L. Ruedisueli; K. G. Booth; J. P. Papageorge; B. A. Eng

1993-01-01

366

Submarine launched ballistic missile - Improved accuracy  

Microsoft Academic Search

The Improved Accuracy Program, a U.S. Navy advanced technology development program which is to provide the capability for predicting with confidence the costs and schedules associated with achieving quantified accuracy improvements in future submarine launched ballistic missile (SLBM) systems, is presented. The stellar inertial Trident I system, which is the baseline upon which improvements are being considered, is summarized. The

R. L. Topping

1981-01-01

367

Arctic Ocean warming: submarine and acoustic measurements  

Microsoft Academic Search

In 1993 the USS Pargo made the first Submarine Science Expedition (SCICEX) to the Arctic Ocean. In April 1994 the first Transarctic Acoustic Propagation (TAP) experiment designed to measure Arctic Ocean temperature was conducted. SCICEX cruises to the Arctic followed annually from 1995 to 2000. Expendable CTDs and on some cruises standard CTDs were deployed along or close to the

P. Mikhalevsky; A. Gavrilov; M. S. Moustafa; B. Sperry

2001-01-01

368

Methanogenic diversity and activity in hypersaline sediments of the centre of the Napoli mud volcano, Eastern Mediterranean Sea.  

PubMed

Submarine mud volcanoes are a significant source of methane to the atmosphere. The Napoli mud volcano, situated in the brine-impacted Olimpi Area of the Eastern Mediterranean Sea, emits mainly biogenic methane particularly at the centre of the mud volcano. Temperature gradients support the suggestion that Napoli is a cold mud volcano with moderate fluid flow rates. Biogeochemical and molecular genetic analyses were carried out to assess the methanogenic activity rates, pathways and diversity in the hypersaline sediments of the centre of the Napoli mud volcano. Methylotrophic methanogenesis was the only significant methanogenic pathway in the shallow sediments (0-40 cm) but was also measured throughout the sediment core, confirming that methylotrophic methanogens could be well adapted to hypersaline environments. Hydrogenotrophic methanogenesis was the dominant pathway below 50 cm; however, low rates of acetoclastic methanogenesis were also present, even in sediment layers with the highest salinity, showing that these methanogens can thrive in this extreme environment. PCR-DGGE and methyl coenzyme M reductase gene libraries detected sequences affiliated with anaerobic methanotrophs (mainly ANME-1) as well as Methanococcoides methanogens. Results show that the hypersaline conditions in the centre of the Napoli mud volcano influence active biogenic methane fluxes and methanogenic/methylotrophic diversity. PMID:21382146

Lazar, Cassandre Sara; Parkes, R John; Cragg, Barry A; L'Haridon, Stéphane; Toffin, Laurent

2011-03-07

369

Towards Developing Systematics for Using Periodic Studies of the Hydrothermal Manifestations as Effective Tool for Monitoring Largely 'inaccessible' Volcanoes  

Microsoft Academic Search

The San José and Tupungatito volcanoes, located near Santiago (Chile), are the potential hazards, given their geological and historical record of explosive eruptions with pyroclastic flows, most recently in 1960 and 1987 respectively (Global Volcanism Program, Smithsonian Institution). What aggravates the potential risk of these very high (>5290m elevation) snow- and ice-covered volcanoes is their location at the source of

M. Alam

2010-01-01

370

Fluid Flow Simulations of an Active Arc-Related Submarine Hydrothermal System  

NASA Astrophysics Data System (ADS)

Active high-temperature vents at the seafloor greatly contribute to the heat transport system at the Earth's surface and significantly influence the chemistry of crust and overlying ocean. While mid-ocean ridge systems have been intensely studied in the last decades, hydrothermal activity along convergent plate boundaries has received deeper attention only in the last few years. Brothers volcano is the most hydrothermally active volcano situated along the intra-oceanic Kermadec arc, northeast of North Island, New Zealand. Recent detailed surveys of hydrothermal plumes at Brothers volcano picture several distinct vent sites at different localities within the volcanic edifice. Venting ranges from lower temperature, gas-rich and metal-poor fluids to relatively high temperature (~300 °C), metal-rich fluids. However, the sub-surface structure of these systems and the contribution of magmatic sources are not well understood yet. In order to model the sub-seafloor hydrodynamics of Brothers volcano, a numerical transport scheme has been applied, using a combined finite element - finite volume method which computes multi-phase fluid flow and describes heat transport on basis of enthalpy, pressure, and salinity. Our process code covers the full phase relations of the binary NaCl-H2O system up to 1000 °C and accurately captures boiling, condensation, and salt precipitation. Numerical simulations for varying first-order physical parameters such as water depth and seafloor topography, rock permeability, and a heat source with or without a deep magmatic fluid source have been conducted. Our results show that seafloor topography controls the spatial distribution of venting sites and the input of a magmatic fluid source affects the style of hydrothermal venting. In this ongoing project, by combining simulation results with real observations in Brothers volcano and other currently active arc-related submarine volcanoes, we aim to present a new understanding of the sub-surface hydrology, the interaction of seawater with magmatic fluids, and subsequently the conditions to generate particularly Cu- and Au-rich mineralization within such magmatic-hydrothermal systems.

Gruen, G.; de Ronde, C. E.; Driesner, T.; Heinrich, C. A.

2009-12-01

371

Seismic anisotropy and its time variation on active volcanoes  

NASA Astrophysics Data System (ADS)

Seismic anisotropy, the directional dependence of wave speeds, is caused by stress-oriented cracks and can be used to monitor stresses from magmatic movement. Shear wave splitting fast polarisations (?) align with cracks and hence with the compressive stress field. Delay times (dt) measure the density of cracks. Time variations in both ? and dt on volcanoes have been reported by ourselves and other workers. Here we report results from a new objective automatic technique, developed on Ruapehu, New Zealand and Asama, Japan. We also applied it to Okmok; Soufrière Hills; Aso; Unzen and Sakurajima. Thousands of measurements made on each volcano allow us to determine correlations with other volcano monitoring techniques. We examine volcano-tectonic earthquakes local to each volcano and more distant regional earthquakes. Seismic waves from local earthquakes travel solely through the volcano, so that anisotropy in the mantle or lower crustal mineral alignment will not affect the measurements, but care must be taken because earthquake locations and hence ray paths may change due to magma movement. Spatial changes are thus difficult to disentangle from temporal changes. We analyse families of earthquakes with near-identical waveforms to try to overcome this limitation. Deep regional earthquakes occur mostly in subducted plates and their paths are affected by mantle and lower crustal mineral anisotropy as well as by crustal stress. They are also affected by laterally varying properties, but earthquakes far removed from the volcano should not have systematic variations in location that are correlated with magma movement. Therefore, changes in measurements from regional events that correlate with magma movement can be interpreted as temporal rather than spatial variations. Common features at all volcanoes are that stations closest to the craters yield the fewest good measurements, and even those tend to give varying results at closely spaced stations. Scattering from the volcanic edifice may be making the S waves difficult to pick, and the local stresses may be varied. Stations on the volcanic flanks give many good measurements. Some stations yield variations in ? and dt that depend upon the earthquake location. But at most volcanoes, some stations show changes that are better explained by variations in time than in space. Where GPS measurements are available, the variations sometimes but not always correlate with previously-modeled inflation or deflation events and ? usually matches well with the stress field modelled from GPS-derived locations of magmatic sources. At Soufrière Hills variations in focal mechanisms correlate with variations in ?. The temporal variations in ? are large, ranging from 30? at some stations to 90? at other stations.

Savage, M. K.; Ohkura, T.; Umakoshi, K.; Shimizu, H.; Iguchi, M.; Johnson, J. H.; Ohminato, T.; Roman, D. C.

2009-12-01

372

Methane anomalies in seawater above the Loihi submarine summit area, Hawaii  

SciTech Connect

Hydrothermal activity above Loihi submarine volcano was characterized by water column distributions of methane, pH and helium-3. It was found that the southern Loihi summit is almost covered with hydrothermal plumes, which have anomalously high concentrations of methane (maximum: 569 {times} 10{sup {minus}6} cm{sup 3} kg{sup {minus}}1) accompanied by high concentrations of helium-3 and low pH values (minimum: 7.18). The plumes consist of two layers: a shallow plume (about 200 m above the summit) and a deep plume (about 100 m above the summit), probably derived from different hydrothermal vents. The shallow and deep plumes showed different CH{sub 4}/{sup 3}He and CH{sub 4}/pH ratios with the same {sup 3}He/pH ratio, which implies that methane concentrations differ between the hydrothermal end members for the two plumes. The variation of methane between the end members is suggested to result from inter-vent inhomogeneity of bacterial activities that consume or produce methane within the vents. Comparison of the CH{sub 4}/{sup 3}He ratios of the two plumes with the previous data for Loihi and other submarine hydrothermal areas confirms that the Loihi hotspot has one to two orders of magnitude smaller CH{sub 4}/{sup 3}He value than those of the East Pacific Rise and the Galapagos spreading centers.

Gamo, Toshitaka; Ishibashi, Junichiro; Sakai, Hitoshi (Univ. of Tokyo (Japan)); Tilbrook, B. (Univ. of Hawaii, Honolulu (USA))

1987-10-01

373

Deformation time series at Llaima volcano, southern Andes  

NASA Astrophysics Data System (ADS)

Llaima volcano, with an edifice height of 3125 m and a volume of about 400 km³, is one of the largest and most active volcanoes in South America. Its eruptive history suggest a potential for very large and hazardous eruptions including pyroclastic flows, air falls and material remobilization in the form of lahars affecting regions even at the lower apron and beyond, posing a significant risk to civilizations, infrastructure and traffic ways. Llaima volcano is near constantly active; since the 17th century strombolian eruptions occurred at a mean frequency of one eruptive phase every five years. Although this strong activity and socioeconomic importance the source of magma, possible magma reservoirs and deformations prior to or associated with eruptions are hitherto unknown. One of the problems for establishing a monitoring system is that Llaima is difficult to access and located in vegetated and topographically rough terrain. To better understand the volcano physics, we created an InSAR time series based on the PS technique using 18 Envisat images from Dezember 2002 to November 2008. Using the StaMPS software we obtained 24,000 stable pixels in the vicinity of the volcano, that allow to investigate a spatiotemporal displacement field. Associated with the recent eruptions, we observed non-linear subsidence at the vicinity of the volcano base. We assessed the validiy of the deformation signal, using statistical tests and discussed the possible influence of athmospheric and topographic errors. To investigate the cause of the observed spatiotemporal deformation we employed an inverse source modelling approach, and simulated the dislocation source as an analytical pressurized spherical model. The inverted source can reproduce the observed deformation and allows to constrain the location of the magma reservoir under Llaima. Moreover we observed a signal might be associated to a slow landslide at the eastern flank of the volcano between December 2007 and Januar 2008. In this presentation we will give the detail of data processing, modelling and interpretation.

Bathke, Hannes; Walter, Thomas; Motagh, Mahdi; Shirzaei, Manoochehr

2010-05-01

374

Anatomy of a basaltic volcano  

Microsoft Academic Search

Kilauea volcano, in Hawaii, may be the best understood basaltic volcano in the world. Magma rises from a depth of 80 km or more and resides temporarily in near-surface reservoirs: eruption begins when the crust above one of these reservoirs splits open in response to a pressure increase. Repeated rift-zone eruptions compress Kilauea's flanks; after decades of accumulation, the stress

Robert I. Tilling; John J. Dvorak

1993-01-01

375

Earthquakes, Volcanoes, and Plate Tectonics  

NSDL National Science Digital Library

This page consists of two maps of the world, showing how earthquakes define the boundaries of tectonic plates. Volcanoes are also distributed at plate boundaries (the "Ring of Fire" in the Pacific) and at oceanic ridges. It is part of the U.S. Geological Survey's Cascades Volcano Observatory website, which features written material, images, maps, and links to related topics.

376

Volcano Homework Assignment  

NSDL National Science Digital Library

In this and similar assignments students have to download quantitative natural hazard data from the Internet, load it into a spreadsheet, rank order the data, calculate recurrence times and plot the result on a log-log graph. They then interpret this graph in terms of the recurrence time of hazard events of different sizes. In many cases this includes comparing results from two different features (volcanoes, faults, rivers, etc.) Uses online and/or real-time data Addresses student fear of quantitative aspect and/or inadequate quantitative skills Uses geophysics to solve problems in other fields Addresses student misconceptions

Jaume, Steven

377

Ruiz Volcano: Preliminary report  

NASA Astrophysics Data System (ADS)

Ruiz Volcano, Colombia (4.88°N, 75.32°W). All times are local (= GMT -5 hours).An explosive eruption on November 13, 1985, melted ice and snow in the summit area, generating lahars that flowed tens of kilometers down flank river valleys, killing more than 20,000 people. This is history's fourth largest single-eruption death toll, behind only Tambora in 1815 (92,000), Krakatau in 1883 (36,000), and Mount Pelée in May 1902 (28,000). The following briefly summarizes the very preliminary and inevitably conflicting information that had been received by press time.

378

Gelatin Volcanoes: Teacher Page  

NSDL National Science Digital Library

This is the Teacher Page of an activity that teaches students how and why magma moves inside volcanoes by injecting colored water into a clear gelatin cast. Activity preparation instructions are on the Student Page, while the Teacher Page has background, preparation, and in-class information. An extension activity has the students repeat the experiment using a square bread pan to simulate the original research that was done using elongate models with triangular cross-sections. This activity is part of Exploring Planets in the Classroom's Volcanology section.

379

New insights on Panarea volcano from terrestrial, marine and airborne data  

NASA Astrophysics Data System (ADS)

The Panarea volcano belongs to the Aeolian arc system and its activity, which recently produced impacts on the environment as well as on human settlements, is known since historical times. This volcano, which includes Panarea island and its archipelago, is the emergent portion of submarine stratovolcano more than 2000 m high and 20 Km across. In November 2002 a submarine gas eruption started offshore 3 Km east of Panarea on top of a shallow rise of 2.3 km2 surrounded by the islets of Lisca Bianca, Bottaro and Lisca Nera. This event has posed new concern on a volcano generally considered extinct. Soon after the submarine eruption, this area has been surveyed under multidisciplinary programs funded by the Italian Department of the Civil Protection and INGV. Monitoring programs included subaerial and sea bottom DEM of Panarea volcano by merging aerial digital photogrammetry, aerial laser scanning and multibeam bathymetry. A GPS ground deformation network (PANANET) was designed, set up and measured during time span December 2002 - October 2007. GPS data show rates of motion and strain values typical of volcanic areas which are in agreement with the NE-SW and NW-SE tectonic systems. The latter coincide with the main pathways for the upwelling of hydrothermal fluids. GPS data inferred a pre-event uplift followed by a general subsidence and shortening across the area that could be interpreted as the response to the surface of the inflation and deflation of the hydrothermal system reservoir which is progressively reducing its pressure after the 2002 gas eruption. Magnetic and gravimetric data depict the deep and shallow structure of the volcano. From geochemical surveys were calculated energetic conditions at craters. Data were coupled with the computed physic-chemical state of the fluids at the level of the deep reservoir and provided the boundary conditions of the occurred event, and suggesting that a low-energy explosion was responsible for producing the craters at the sea bottom. Finally, we provide a model constrained by GPS data and Okada formulation, which suggests that the degassing intensity and distribution are strongly influenced by geophysical-geochemical changes within the hydrothermal/geothermal system. These variations may be triggered by changes in the regional stress field as suggested by the geophysical and volcanological events which occurred in 2002 in the Southern Tyrrhenian area.

Anzidei, Marco

2010-05-01

380

Submarine groundwater discharge in Lützow-Holm Bay, Antarctica  

NASA Astrophysics Data System (ADS)

We measured submarine groundwater discharge (SGD) for the first time in Antarctica, at Lützow-Holm Bay, using a newly developed automated seepage meter. Measured SGD rates ranged from 10-8 to 10-6 m s-1 are substantially greater than previously observed discharge rates at similar depth. The obtained SGD rates are accurate to within 3%-5%. Using a fast Fourier transform, we found that variations in the power spectrum density had a predominant period of 12.8 h, similar to that of the M2 tide, with peak values differing from average SGD rates by a factor of three. The high SGD rates obtained at the Antarctic marginal ice zone may reflect the contribution of significant volumes of subglacial meltwater from the rugged subglacial mountains located about 20 km inland from the coast. We discuss a possible mechanism of meltwater discharge to this coastal region.

Uemura, Takeshi; Taniguchi, Makoto; Shibuya, Kazuo

2011-04-01

381

Seismic Observations of Westdahl volcano and Western Unimak Island Alaska: 1999-2005  

NASA Astrophysics Data System (ADS)

Westdahl volcano is a large basaltic shield volcano on the western end of Unimak Island Alaska in the Aleutian Island Arc. The volcano is topped by three separate vents, Pogromni Volcano, Faris Peak, and Westdahl Peak. The volcano is frequently active with known eruptions from Westdahl Peak in 1964, 1978, and 1991-92 that produced large basaltic lava flows. InSAR measurements indicate that Westdahl Volcano has been inflating at a slowly declining rate since 1992 (Lu et al., 2003). The Alaska Volcano Observatory has operated a network of six short-period seismometers on Westdahl Peak since 1998. Complementing this network are similar networks centered on Shishaldin and Akutan Volcanoes. Since 1999 more than 300 earthquakes have been located within 20 km of Westdahl Volcano. A volcano specific velocity model was determined for the western half of Uminak Island by simultaneously inverting for the velocity model and hypocentral earthquake locations using the program VELEST. Earthquakes located with the new model reveal five clusters of hypocenters: (a) a shallow cluster beneath Westdahl Peak, that largely occurred during a 24-hour period on January 7, 2004, (b) a concentration of 68 earthquakes with hypocenters ranging in depth from zero to eight km beneath Faris Peak occurring continually since 1999, (c) a diffuse cluster of long-period events northwest of Westdahl and Faris Peaks, (d) a cluster of 12 earthquakes near Pinnacle Rock, 12 km southwest of Westdahl Peak in October 2003, and (e) a cluster of 43 hypocenters near Unimak Bight, 20 km east of Westdahl Peak, that occurred between January and April 2004. Focal mechanisms were derived for four earthquakes in the Faris Peak cluster and four additional earthquakes that locate off the volcanic edifice (the four mechanisms are in the Pinnacle Rock cluster, the Unimak Bight cluster, and 20 km southeast and 30 km northeast of the volcano). Focal mechanisms in the Faris Peak cluster showed normal faulting with nodal planes trending north-south to northwest-southeast. Mechanisms of the off-volcano earthquakes are generally characterized by normal faulting with nodal planes trending southwest-northeast. These events are consistent with a stress field dominated by the Aleutian subduction zone. The Faris Peak mechanisms are not consistent with the presumed regional stress field and may reflect volcanic process. Lu et al., (2003) proposed the observed inflation of Westdahl Volcano resulted from a slowly pressurizing magma source at 6 km depth beneath Westdahl Peak. The observed seismicity is consistent with this model. Lu, Z., T. Masterlark, D. Dzurisin, and R. Rykhus, 2003, Magma supply dynamics at Westdahl volcano, Alaska, modeled from satellite radar interferometry, Alaska, J. Geophys. Res. 108, 2354, doi:10.1029/2002JB002311, 2003.

Dixon, J. P.; Power, J. A.; Stihler, S. D.

2005-12-01

382

Hydrothermal mineralogy of core from geothermal drill holes at Newberry Volcano, Oregon  

USGS Publications Warehouse

Hydrothermal mineralogy studies of specimens collected from nine geothermal drill holes suggest that, at the locations and depths drilled, past temperatures have been hottest (exceeding 300?C) near ring fractures on the south and west sides of Newberry Volcano.

Bargar, Keith E.; Keith, Terry E.

1999-01-01

383

Crustal and mantle influences and U–Th–Ra disequilibrium in andesitic lavas of Ngauruhoe volcano, New Zealand  

Microsoft Academic Search

The andesitic volcano Ngauruhoe, which is located within the Tongariro Volcanic Complex at the southern end of the Taupo Volcanic Zone in North Island, New Zealand, has been constructed over the past 5ka and last erupted in 1975. Nearby Ruapehu volcano has a much longer eruptive history extending back beyond 230kaB.P. The magmas erupted at both volcanoes have been predominantly

Richard C. Price; Simon Turner; Craig Cook; Barbara Hobden; Ian E. M. Smith; John A. Gamble; Heather Handley; Roland Maas; Anja Möbis

2010-01-01

384

Submarine Paleoseismology Based on Turbidite Records  

NASA Astrophysics Data System (ADS)

Many of the largest earthquakes are generated at subduction zones or other plate boundary fault systems near enough to the coast that marine environments may record evidence of them. During and shortly after large earthquakes in the coastal and marine environments, a spectrum of evidence may be left behind, mirroring onshore paleoseismic evidence. Shaking or displacement of the seafloor can trigger processes such as turbidity currents, submarine landslides, tsunami (which may be recorded both onshore and offshore), and soft-sediment deformation. Marine sites may also share evidence of fault scarps, colluvial wedges, offset features, and liquefaction or fluid expulsion with their onshore counterparts. This article reviews the use of submarine turbidite deposits for paleoseismology, focuses on the dating and correlation techniques used to establish stratigraphic continuity of marine deposits, and outlines criteria for distinguishing earthquake deposits and the strategies used to acquire suitable samples and data for marine paleoseismology.

Goldfinger, Chris

2011-01-01

385

Submarine paleoseismology based on turbidite records.  

PubMed

Many of the largest earthquakes are generated at subduction zones or other plate boundary fault systems near enough to the coast that marine environments may record evidence of them. During and shortly after large earthquakes in the coastal and marine environments, a spectrum of evidence may be left behind, mirroring onshore paleoseismic evidence. Shaking or displacement of the seafloor can trigger processes such as turbidity currents, submarine landslides, tsunami (which may be recorded both onshore and offshore), and soft-sediment deformation. Marine sites may also share evidence of fault scarps, colluvial wedges, offset features, and liquefaction or fluid expulsion with their onshore counterparts. This article reviews the use of submarine turbidite deposits for paleoseismology, focuses on the dating and correlation techniques used to establish stratigraphic continuity of marine deposits, and outlines criteria for distinguishing earthquake deposits and the strategies used to acquire suitable samples and data for marine paleoseismology. PMID:21329198

Goldfinger, Chris

2011-01-01

386

33 CFR 334.75 - Thames River, Naval Submarine Base New London, restricted area.  

Code of Federal Regulations, 2010 CFR

...Thames River, Naval Submarine Base New London, restricted area. 334.75 ...Thames River, Naval Submarine Base New London, restricted area. (a) The area...area when notified by personnel of the New London Submarine Base that such...

2010-07-01

387

33 CFR 334.75 - Thames River, Naval Submarine Base New London, restricted area.  

Code of Federal Regulations, 2010 CFR

...Thames River, Naval Submarine Base New London, restricted area. 334.75 ...Thames River, Naval Submarine Base New London, restricted area. (a) The area...area when notified by personnel of the New London Submarine Base that such...

2009-07-01

388

Types and Effects of Volcano Hazards  

NSDL National Science Digital Library

This United States Geological Survey (USGS) website discusses volcano hazards by type (gas, lahars, landslides, lava flows, pyroclastic flows, and tephra) and by the effect volcanoes have on people and land. This site gives an overview of volcano hazards and links to selected case studies listed by country, volcano, year, and type of hazard. Links to more USGS information about volcanoes, such as a photo glossary, a site index, observatories, and an educator's page are also provided.

389

Probing High-altitude Winds Using Infrasound from Volcanoes  

Microsoft Academic Search

The analysis of infrasound of the International Monitoring System (IMS) shows that infrasound detection and location are submitted to the effects of the stratospheric winds which significantly influence the propagation. Known and quasi permanent infrasonic sources are needed to evaluate and improve upper-wind models. Continuous monitoring of infrasound from active volcanoes in Vanuatu is proposed for such investigations. A 3D

A. Le Pichon; D. Drob

390

Topographic Effects on Ground Motion at Santiaguito Volcano, Guatemala  

Microsoft Academic Search

Broadband seismic data recorded at four stations near an active volcanic vent suggest that topographic effects may significantly alter amplitude and frequency components in the near field. Four days of continuous recording of explosions at Santiaguito Volcano, Guatemala, show significant variations in seismic response when stations are located off of nearby domes versus at the nearby dome peaks. Each station

J. Anderson; J. M. Lees; J. B. Johnson; G. P. Waite

2009-01-01

391

Microearthquakes at St. Augustine Volcano, Alaska, Triggered by Earth Tides  

Microsoft Academic Search

Microearthquake activity at St. Augustine volcano, located at the mouth of Cook Inlet in the Aleutian Islands, has been monitored since August 1970. Both before and after minor eruptive activity on 7 October 1971, numerous shallow-foci microearthquake swarms were recorded. Plots of the hourly frequency of microearthquakes often show a diurnal peaking of activity. A cross correlation of this activity

F. J. Mauk; J. Kienle

1973-01-01

392

Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements  

Microsoft Academic Search

Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January–March) and the summer (July–September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores

Chih-An Huh; James T. Liu; Hui-Ling Lin; J. P. Xu

2009-01-01

393

General patterns of circulation, sediment fluxes and ecology of the Palamós (La Fonera) submarine canyon, northwestern Mediterranean  

Microsoft Academic Search

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data

Albert Palanques; Emilio García-Ladona; Damià Gomis; Jacobo Martín; Marta Marcos; Ananda Pascual; Pere Puig; Josep-Maria Gili; Mikhail Emelianov; Sebastià Monserrat; Jorge Guillén; Joaquín Tintoré; Mariona Segura; Antoni Jordi; Simón Ruiz; Gotzon Basterretxea; Dolors Blasco; Francesc Pagès

2005-01-01

394

Volcano spacing and plate rigidity  

SciTech Connect

In-plane stresses, which accompany the flexural deformation of the lithosphere under the load adjacent volcanoes, may govern the spacing of volcanoes in hotspot provinces. Specifically, compressive stresses in the vicinity of a volcano prevent new upwelling in this area, forcing a new volcano to develop at a minimum distance that is equal to the distance in which the radial stresses change from compressional to tensile (the inflection point). If a volcano is modeled as a point load on a thin elastic plate, then the distance to the inflection point is proportional to the thickness of the plate to the power of 3/4. Compilation of volcano spacing in seven volcanic groups in East Africa and seven volcanic groups of oceanic hotspots shows significant correlation with the elastic thickness of the plate and matches the calculated distance to the inflection point. In contrast, volcano spacing in island arcs and over subduction zones is fairly uniform and is much larger than predicted by the distance to the inflection point, reflecting differences in the geometry of the source and the upwelling areas.

Brink, U. (Stanford Univ., California (USA))

1991-04-01

395

Submarine seawater reverse osmosis desalination system  

Microsoft Academic Search

The project presented addresses the strategic topic of providing drinking and irrigation water through seawater desalination via a very energy-efficient and cost-competitive submarine technology. In conventional surface based industrial desalination plants applying the reverse osmosis (RO) technology, the freshwater flow behind the membranes is approximately 20–45% of the inlet seawater flow, depending on membrane type and characteristics. The resulting brine

Paolo Pacenti; Mario de Gerloni; Mario Reali; David Chiaramonti; Sven O. Gärtner; Peter Helm; Michael Stöhr

1999-01-01

396

Tracking of Constrained Submarine Robot Arms  

Microsoft Academic Search

Despite the appearance of impressive submarine robot arms (SRA), simple posture (position\\/orientation) regulators are implemented\\u000a nowadays and tracking still remains an open issue, let alone the force\\/posture tracking goal. The main challenge to achieve\\u000a simultaneous tracking of posture and force seems the complex dynamical structure, the difficulty to measure precisely the\\u000a inertial parameters of SRA and the access to the

Ernesto Olguín-Díaz; Vicente Parra-Vega

397

Isotopic and trace element geochemistry of lavas from the northern Mariana and southern volcano arcs  

SciTech Connect

Samples from submarine volcanoes and islands were analyzed for concentrations of K, Rb, Sr, Ba, REE, {sup 87}Sr/{sup 86}Sr and some selected samples for {sup 143}Nd/{sup 144}Nd. These data show strong variations along the arc, being relatively depleted in the tholeiitic and low-K calc-alkaline volcanoes of the Volcano Arc (VA) and the Mariana Central Island Province (CIP). All of the Mariana Northern Seamount Province (NSP) and Volcano arc Iwo Jima (IJ) are enriched in LIL and LREE, particularly in the northern half, where the lavas have strong shoshonitic affinities. Chemical characteristics of these lavas suggest source- or melt-mixing, with the NSP shoshonites being derived from a LIL- and LREE-enriched OIB-like source or melt, while Mariana CIP and Volcano Arc melts are derived from a depleted MORB-like mangle that has been recharged with K, Rb, Sr and Ba by hydrous fluids. Neodymium and strontium isotopic data reveal {var epsilon}{sub Nd} values ranging from +2.4 to +9.5 and {sup 87}Sr/{sup 86}Sr from 0.70320 to 0.70405. Anomalous trends of {sup 87}Sr/{sup 86}Sr and Ba/La found in some S-NSP lavas suggest that the addition of a sedimentary component may be superimposed on the two component mixing. The lavas from the Mariana and Volcano arcs, therefore, are interpreted as resulting from mixing of at least three components. The bulk of the lavas derive from an OIB-like mantle source (or melt) mixing with various proportions of a metasomatized depleted mantle source (or melt). These hybrid sources may be contaminated with minor amounts of subducted sediment and fluxed by multistage-fractionated metasomatic fluid which is derived from subducted sediment and slab after the mixing of the first two components.

Lin Pingnan.

1989-01-01

398

Large debris avalanches and associated eruptions in the Holocene eruptive history of Shiveluch Volcano, Kamchatka, Russia  

Microsoft Academic Search

Shiveluch Volcano, located in the Central Kamchatka Depression, has experienced multiple flank failures during its lifetime,\\u000a most recently in 1964. The overlapping deposits of at least 13 large Holocene debris avalanches cover an area of approximately\\u000a 200?km2 of the southern sector of the volcano. Deposits of two debris avalanches associated with flank extrusive domes are, in addition,\\u000a located on its

Vera V. Ponomareva; Maria M. Pevzner; Ivan V. Melekestsev

1998-01-01

399

Moment tensor analysis of near-field broadband waveforms observed at Aso Volcano, Japan  

Microsoft Academic Search

Locations and focal mechanisms of long-period volcanic events observed at Aso volcano, Japan, are determined by waveform inversion. Near-field broadband three-component seismograms of four to seven stations are simultaneously inverted in the time domain in order to find the six-component seismic moment tensor. A linear inversion is performed at each point of a 3D grid located under the volcano in

D. Legrand; S. Kaneshima; H. Kawakatsu

2000-01-01

400

The submarine service of the future?  

PubMed

Space missions, although now routine, are unique in terms of their environment and logistical requirements. The number of missions (man-hours) remains relatively small and planning still relies on comparisons with analogous missions, including submarine operations. Antarctic missions, which tend not to be classified, have provided more information about isolated communities because of the number of personnel per base. Space medicine has traditionally been an extension of aviation medicine with high g-forces involved in the transition from Earth to orbit and astronauts such as Neil Armstrong recruited from the test pilot fraternity. As the length of a mission increases and the space habitation relies more on regenerative systems, the environment becomes more analogous with today's nuclear submarines. As well as the air purification implications, radiation still is a significant hazard with even greater impact on future Mars missions requiring the provision of health physics monitoring, advice and countermeasures well established in the submarine flotilla. Nevertheless, the specialty space medicine will progress as a specialty in its own right, pooling expertise from other specialties such as aviation, radiation, emergency and occupational medicine taking human exploration beyond the confines of land and sea. PMID:11346925

Bland, S A

2000-01-01

401

Tephra compositions from Late Quaternary volcanoes around the Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

Crustal extension and rifting processes opened the Bransfield Strait between the South Shetland Islands and the Antarctic Peninsula during the last 4 Ma. Similar processes on the Peninsula's eastern side are responsible for volcanism along Larsen Rift. There are at least 11 volcanic centers with known or suspected Late Pleistocene / Holocene explosive activity (Fig. 1). Fieldwork was carried out on the islands Deception, Penguin, Bridgeman and Paulet, moreover at Melville Peak (King George Is.) and Rezen Peak (Livingston Is.). Of special importance is the second ever reported visit and sampling at Sail Rock, and the work on never before visited outcrops on the northern slopes and at the summit of Cape Purvis volcano (Fig. 1). The new bulk tephra ICP-MS geochemical data provide a reliable framework to distinguish the individual volcanic centers from each other. According to their Mg-number, Melville Peak and Penguin Island represent the most primitive magma source. Nb/Y ratios higher than 0.67 in combination with elevated Th/Yb and Ta/Yb ratios and strongly enriched LREE seem to be diagnostic to distinguish the volcanoes located along the Larsen Rift from those associated with Bransfield Rift. Sr/Y ratios discriminate between the individual Larsen Rift volcanoes, Paulet Island showing considerably higher values than Cape Purvis volcano. Along Bransfield Rift, Bridgeman Island and Melville Peak have notably lower Nb/Y and much higher Th/Nb than Deception Island, Penguin Island and Sail Rock. The latter displays almost double the Th/Yb ratio as compared to Deception Island, and also much higher LREE enrichment but extraordinarily low Ba/Th, discriminating it from Penguin Island. Such extremely low Ba/Th ratios are also typical for Melville Peak, but for none of the other volcanoes. Penguin Island has almost double the Ba/Th and Sr/Y ratios higher than any other investigated volcano. Whereas the volcanoes located in the northern part of Bransfield Strait have Zr/Hf ratios lower than N-MORB, all other volcanoes including the Larsen Rift centers display Zr/Hf higher than N-MORB. It is expected that the correlation of the new data with published data from tephra layers found in ice, lake and marine sediment cores will contribute to a better constrained timing of individual climatic events identified in the northern Antarctic Peninsula area. Late Quaternary volcanoes around the northern Antarctic Peninsula.

Kraus, S.

2009-12-01

402

Contrasting pyroclast density spectra from subaerial and submarine silicic eruptions in the Kermadec arc: implications for eruption processes and dredge sampling  

NASA Astrophysics Data System (ADS)

Pyroclastic deposits from four caldera volcanoes in the Kermadec arc have been sampled from subaerial sections (Raoul and Macauley) and by dredging from the submerged volcano flanks (Macauley, Healy, and the newly discovered Raoul SW). Suites of 16-32 mm sized clasts have been analyzed for density and shape, and larger clasts have been analyzed for major element compositions. Density spectra for subaerial dry-type eruptions on Raoul Island have narrow unimodal distributions peaking at vesicularities of 80-85%, whereas ingress of external water (wet-type eruption) or extended timescales for degassing generate broader distributions, including denser clasts. Submarine-erupted pyroclasts show two different patterns. Healy and Raoul SW dredge samples and Macauley Island subaerial-emplaced samples are dominated by modes at ~80-85%, implying that submarine explosive volcanism at high eruption rates can generate clasts with similar vesicularities to their subaerial counterparts. A minor proportion of Healy and Raoul SW clasts also show a pink oxidation color, suggesting that hot clasts met air despite 0.5 to >1 km of intervening water. In contrast, Macauley dredged samples have a bimodal density spectrum dominated by clasts formed in a submarine-eruptive style that is not highly explosive. Macauley dredged pyroclasts are also the mixed products of multiple eruptions, as shown by pumice major-element chemistry, and the sea-floor deposits reflect complex volcanic and sedimentation histories. The Kermadec calderas are composite features, and wide dispersal of pumice does not require large single eruptions. When coupled with chemical constraints and textural observations, density spectra are useful for interpreting both eruptive style and the diversity of samples collected from the submarine environment.

Barker, Simon J.; Rotella, Melissa D.; Wilson, Colin J. N.; Wright, Ian C.; Wysoczanski, Richard J.

2012-08-01

403

Groundwater at Mayon, Volcano  

NASA Astrophysics Data System (ADS)

Around Mayon Volcano, Philippines, anecdotal evidence and rainfall normalized spring discharge data suggest that the water table 8 km from the summit of the volcano drops prior to eruptions. Residents report that they had to deepen their shallow wells in 1993 (some before and others following the eruption). In some cases they had to dig as far as 5 meters deeper to reach the water table. Significant decreases in spring discharge were recorded prior to the 1999 phreatic explosions and explosive eruption in 2000. A lesser decrease in spring discharge was recorded prior to the 2001 explosive eruptions. The cause of the observed correlation is not yet understood. Mechanisms consider include decrease in rainfall and boiling away of groundwater due to magmatic intrusion. Dilatation of the volcano may cause an increase in pore pressure, opening of cracks, and inflation of the ground surface that would all result in lower water table levels and decreases in spring discharges. Lack of significant hydraulic precursors prior to the 2001 eruptions may be due to a sustained state of inflation following the eruption of 2000. To better understand the relationship between changes in the volcanic system and changes in the groundwater system surrounding Mayon, instruments were installed about eight kilometers from the summit immediately following the explosive eruption of 26 July 2001. Parameters monitored include rainfall data, water levels in four shallow wells, discharge in the main river basin, and spring discharge. The aquifers at eight kilometers are predominantly poorly sorted lahar flow deposits. Characterization of these highly permeable aquifers has been conducted. Preliminary data include porosity ranges, hydraulic conductivity estimates, and response to rainfall. Water samples have been collected that are intended for geo-chemical analysis to determine if the water is predominantly meteoric or magmatic in origin. Numerical modeling of the system using the above mentioned parameters is planned. We expect to determine what the magnitude of strain produced by the intruding magma would have to be for the lowering of the water table that was observed in 1993, 1999, and 2000. This strain will then be compared with the expected strain from volcanic intrusion to determine if strain alone could be responsible for the changes to the groundwater system.

Albano, S. E.; Sandoval, T.; Toledo, R.

2001-12-01

404

Plunge Pools in Hawaiian Submarine Canyons  

NASA Astrophysics Data System (ADS)

Many submarine canyon systems include well-defined intra-canyon depressions. Often, these depressions are found at the base of scarps along the canyon thalweg, with morphologic characteristics similar to subarial plunge pools formed at waterfalls. One plausible mechanism for the origin of these features is scouring during submarine debris flows. Other processes which can plausibly contribute to the formation of re-entrants and depressions in submarine canyons include erosion by spring sapping, slumping, collapse following gas expulsion or subsurface dissolution, and channel damming by mass wasting of canyon walls. The Monterey Bay Aquarium Research Institution conducted ROV dives around the Hawaiian Islands during a spring 2001 expedition of the R/V Western Flyer and ROV Tiburon. Three ROV dives investigated submarine canyons on the north (windward) sides of Molokai and Hawaii that exhibit well-developed intra-canyon depressions. These depressions ranged from 10 m deep and 150 m across to 90 m deep and 750 m across. The headwall scarps ranged from 20 m to 350 m. ROV video observations combined with rock and sediment sampling allowed us to characterize the depressions' detailed morphology, relate the morphology to the underlying geology, and view the genesis of these features in the context of the origin and evolution of the canyon systems as a whole. Our observations support the hypothesis that these intra-canyon depressions, or plunge pools, are formed through scouring during submarine debris flows. In all cases the down-canyon depression sills are dams composed of debris piles, with angular rubble exposed on the depression side and sand covering the down-canyon side. The Molokai plunge pool is draped with mud and silt, suggesting no recent activity. However, the Kohala plunge pools show clear signs of recent scour and no sediment cover. The headwalls above the plunge pools expose layered volcanoclastic and lava flow units, with more resistant layers frequently forming vertical or overhanging walls. We interpret these canyons as being largely formed through retrogressive (headward) erosion and slope failure. Periodic rockfalls and debris flows following undercutting of the headwalls scours the depressions, builds the pool dams, and both lengthens and deepens the canyons. >http://www.mbari.org/education/cruises/Hawaii/

Caress, D. W.; Greene, H. G.; Greene, H. G.; Paull, C. K.; Ussler, W.; Clague, D.; Moore, J. G.; Maher, N. H.

2001-12-01

405

Gas hydrate accumulation at the Hakon Mosby Mud Volcano  

USGS Publications Warehouse

Gas hydrate (GH) accumulation is characterized and modeled for the Hakon Mosby mud volcano, ca. 1.5 km across, located on the Norway-Barents-Svalbard margin. Pore water chemical and isotopic results based on shallow sediment cores as well as geothermal and geomorphological data suggest that the GH accumulation is of a concentric pattern controlled by and formed essentially from the ascending mud volcano fluid. The gas hydrate content of sediment peaks at 25% by volume, averaging about 1.2% throughout the accumulation. The amount of hydrate methane is estimated at ca. 108 m3 STP, which could account for about 1-10% of the gas that has escaped from the volcano since its origin.

Ginsburg, G. D.; Milkov, A. V.; Soloviev, V. A.; Egorov, A. V.; Cherkashev, G. A.; Vogt, P. R.; Crane, K.; Lorenson, T. D.; Khutorskoy, M. D.

1999-01-01

406

Assessing Volcanic Threat and Prioritizing Volcano Monitoring in the United States  

NASA Astrophysics Data System (ADS)

A methodology to characterize and rank volcanic threat was developed to prioritize monitoring improvements on a national scale. 169 Holocene-age U.S. volcanoes are ranked by level of threat based on scoring of various hazard factors (for example, explosivity, frequency of eruptions) and exposure factors (for example, nearby population and infrastructure, aviation) that were chosen to give a balanced view of unmitigated volcanic threat. For each volcano, the sum of its hazard score times the sum of its exposure score gives a numerical threat score. The distribution of scores for all 169 volcanoes defines five threat groups ranging from Very High to Very Low. Higher-threat volcanoes warrant better early-warning monitoring capability than lower-threat volcanoes. Accordingly, the adequacy of the current monitoring level at each volcano is rated on our ability to characterize ongoing and expected activity based on the types, numbers, and location of monitoring instrumentation now in place at each. The current monitoring level is compared to the level warranted by a volcano's threat score to determine if it has a significant "monitoring gap". The gap analysis systematically identifies hazardous volcanoes where monitoring is inadequate for the threats posed such as in the Cascade Range. This analysis also highlights serious monitoring inadequacies in Alaska and the Northern Marianas where the volcanic-ash hazard to aviation is high yet numerous volcanoes have no monitoring whatsoever; from a hazards perspective these regions can no longer be considered remote. The results of the U.S. volcanic threat assessment are being used to guide long-term improvements to the national volcano-monitoring infrastructure operated by the USGS and affiliated partners and to establish a National Volcano Early Warning System. Given the time required to install instrumentation and telemetry in volcanic areas and the need to provide reliable scientific interpretation of the progression of unrest, improvements need to be implemented well in advance the onset of unrest.

Ewert, J. W.; Guffanti, M.; Murray, T. L.

2005-12-01

407

Deep long-period earthquakes beneath Washington and Oregon volcanoes  

USGS Publications Warehouse

Deep long-period (DLP) earthquakes are an enigmatic type of seismicity occurring near or beneath volcanoes. They are commonly associated with the presence of magma, and found in some cases to correlate with eruptive activity. To more thoroughly understand and characterize DLP occurrence near volcanoes in Washington and Oregon, we systematically searched the Pacific Northwest Seismic Network (PNSN) triggered earthquake catalog for DLPs occurring between 1980 (when PNSN began collecting digital data) and October 2009. Through our analysis we identified 60 DLPs beneath six Cascade volcanic centers. No DLPs were associated with volcanic activity, including the 1980-1986 and 2004-2008 eruptions at Mount St. Helens. More than half of the events occurred near Mount Baker, where the background flux of magmatic gases is greatest among Washington and Oregon volcanoes. The six volcanoes with DLPs (counts in parentheses) are Mount Baker (31), Glacier Peak (9), Mount Rainier (9), Mount St. Helens (9), Three Sisters (1), and Crater Lake (1). No DLPs were identified beneath Mount Adams, Mount Hood, Mount Jefferson, or Newberry Volcano, although (except at Hood) that may be due in part to poorer network coverage. In cases where the DLPs do not occur directly beneath the volcanic edifice, the locations coincide with large structural faults that extend into the deep crust. Our observations suggest the occurrence of DLPs in these areas could represent fluid and/or magma transport along pre-existing tectonic structures in the middle crust. ?? 2010 Elsevier B.V.

Nichols, M. L.; Malone, S. D.; Moran, S. C.; Thelen, W. A.; Vidale, J. E.

2011-01-01

408

Electrical structure of Newberry Volcano, Oregon  

NASA Astrophysics Data System (ADS)

From the interpretation of magnetotelluric, transient electromagnetic, and Schlumberger resistivity soundings, the electrical structure of Newberry Volcano in central Oregon is found to consist of four units. From the surface downward, the geoelectrical units are (1) very resistive, young, unaltered volcanic rock, (2) a conductive layer of older volcanic material composed of altered tuffs, (3) a thick resistive layer thought to be in part intrusive rocks, and (4) a lower-crustal conductor. This model is similar to the regional geoelectrical structure found throughout the Cascade Range. Inside the caldera, the conductive second layer corresponds to the steep temperature gradient and alteration minerals observed in the USGS Newberry 2 test hole. Drill hole information on the south and north flanks of the volcano (test holes GEO N-1 and GEO N-3, respectively) indicates that outside the caldera the conductor is due to alteration minerals (primarily smectite) and not high-temperature pore fluids. On the flanks of Newberry the conductor is generally deeper than inside the caldera, and it deepens with distance from the summit. A notable exception to this pattern is seen just west of the caldera rim, where the conductive zone is shallower than at other flank locations. The volcano sits atop a rise in the resistive layer, interpreted to be due to intrusive rocks. The intrusive material has served as a heat source to produce enhanced hydrothermal alteration and, perhaps in the case of the west-flank anomaly, elevated fluid temperatures. While no public drill hole information is available to confirm this hypothesis, the west-flank anomaly appears to be a good geothermal target. In addition to the possibility that a region on the west side of the volcano could be favorable for prospecting, part of the resistive structure under the center of the volcano could be due to a vapor-dominated environment with temperatures above 300°C. In other parts of the Cascades, pervasive alteration has produced mixed layer clays and zeolites, resulting in low-resistivity anomalies. Low resistivities cannot be assumed to indicate high-temperature pore fluids. The use of electrical methods that measure resistivity as a function of excitation frequency, such as spectral induced polarization, may provide a way of obtaining information about the type and extent of alteration.

Fitterman, D. V.; Stanley, W. D.; Bisdorf, R. J.

1988-09-01

409

On the absence of InSAR-detected volcano deformation spanning the 1995–1996 and 1999 eruptions of Shishaldin Volcano, Alaska  

Microsoft Academic Search

Shishaldin Volcano, a large, frequently active basaltic-andesite volcano located on Unimak Island in the Aleutian Arc of Alaska, had a minor eruption in 1995–1996 and a VEI 3 sub-Plinian basaltic eruption in 1999. We used 21 synthetic aperture radar images acquired by ERS-1, ERS-2, JERS-1, and RADARSAT-1 satellites to construct 12 coherent interferograms that span most of the 1993–2003 time

S. C. Moran; O. Kwoun; T. Masterlark; Z. Lu

2006-01-01

410

Soil CO2 emissions at Furnas volcano, São Miguel Island, Azores archipelago: Volcano monitoring perspectives, geomorphologic studies, and land use planning application  

Microsoft Academic Search

Carbon dioxide (CO2) diffuse degassing structures (DDS) at Furnas volcano (São Miguel Island, Azores) are mostly associated with the main fumarolic fields, evidence that CO2 soil degassing is the surface expression of rising steam from the hydrothermal system. Locations with anomalous CO2 flux are mainly controlled by tectonic structures oriented WNW–ESE and NW–SE and by the geomorphology of the volcano,

Fátima Viveiros; Carlo Cardellini; Teresa Ferreira; Stefano Caliro; Giovanni Chiodini; Catarina Silva

2010-01-01

411

VolcanoWorld Online Lessons  

NSDL National Science Digital Library

These five activities are sequential and are designed to cover introductory volcano topics. Included are objectives, materials lists, procedures, and a selection of related sites for students to access.

412

USGS Cascades Volcano Observatory: Maps and Graphics  

NSDL National Science Digital Library

The United States Geological Survey's website for the Cascades Volcano Observatory (CVO) has a host of graphics and maps for the professional volcano researcher or the amateur volcanologist. The maps and graphics are divided into four broad categories, and within each of those categories are dozens and dozens of maps and graphics. The categories include "Hazards, Features, Topics, and Types: Maps and Graphics", "Monitoring: Maps and Graphics", and "Volcano or Region: Maps and Graphics". Visitors should check out "Bachelor", which is in the "Volcano or Region" category, as there is an "Interactive Imagemap" of the Cascade Range Volcanoes. Clicking on any of the images of the volcanoes will reveal a beautiful, aerial photo of the volcano, along with a brief description of the history of the volcano. Additionally, there is a "Planning Your Visit" section that gives online and offline resources to look at before going to the actual volcano.

413

Mud volcanoes in deepwater Nigeria  

Microsoft Academic Search

Detailed study of 3D seismic data from deepwater Nigeria has revealed the presence of features interpreted to be mud volcanoes. They occur in an upper slope environment seen as 1–2km circular features at the seabed. Seabed cores from the mud volcanoes contain oil, gas and sand\\/shale–clast content richer than the seabed background. Pliocene fossils have been identified in the cores,

K Graue

2000-01-01

414

Mahukona: The missing Hawaiian volcano  

SciTech Connect

New bathymetric and geochemical data indicate that a seamount west of the island of Hawaii, Mahukona, is a Hawaiian shield volcano. Mahukona has weakly alkalic lavas that are geochemically distinct. They have high {sup 3}He/{sup 4}He ratios (12-21 times atmosphere), and high H{sub 2}O and Cl contents, which are indicative of the early state of development of Hawaiian volcanoes. The He and Sr isotopic values for Mahukona lavas are intermediate between those for lavas from Loihi and Manuna Loa volcanoes and may be indicative of a temporal evolution of Hawaiian magmas. Mahukona volcano became extinct at about 500 ka, perhaps before reaching sea level. It fills the previously assumed gap in the parallel chains of volcanoes forming the southern segment of the Hawaiian hotspot chain. The paired sequence of volcanoes was probably caused by the bifurcation of the Hawaiian mantle plume during its ascent, creating two primary areas of melting 30 to 40 km apart that have persisted for at least the past 4 m.y.

Garcia, M.O.; Muenow, D.W. (Univ. of Hawaii, Honolulu (USA)); Kurz, M.D. (Woods Hole Oceanographic Institution, MA (USA))

1990-11-01

415

The ~ 2500 yr B.P. Chicoral non-cohesive debris flow from Cerro Machín Volcano, Colombia  

Microsoft Academic Search

Cerro Machín Volcano (CMV) is located in the central part of the Colombian Andes (2750 m asl), 150 km southwest of Bogotá. It is considered the most dangerous active volcano of Colombia. CMV has experienced at least six major explosive eruptions during the last 5000 years. These eruptions have emplaced many types of pyroclastic deposits with associated lahars that have traveled more than

H. F. Murcia; B. O. Hurtado; G. P. Cortés; J. L. Macías; H. Cepeda

2008-01-01

416

Volcanic Hazard Map as a Tool of City Planning: Experiences at Galeras Volcano and the county of Pasto, Colombia  

Microsoft Academic Search

Large populated areas located near active volcanoes emphasize the importance to take effective actions towards risk reduction. A volcanic hazard map is believed to be the first step in order to inform government officials, private institutions and community about the danger that poses a particular volcano. The hazard map is a tool that must be used to evaluate risk and

M. L. Calvache

2001-01-01

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