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Exploring Submarine Arc Volcanoes Steven Carey University of Rhode Island, [email protected]

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Exploring Submarine Arc Volcanoes Steven Carey University of Rhode Island, Scarey@Uri.Edu University of Rhode Island DigitalCommons@URI Graduate School of Oceanography Faculty Graduate School of Oceanography Publications 2007 Exploring Submarine Arc Volcanoes Steven Carey University of Rhode Island, [email protected] Haraldur Sigurdsson University of Rhode Island Follow this and additional works at: https://digitalcommons.uri.edu/gsofacpubs Terms of Use All rights reserved under copyright. Citation/Publisher Attribution Carey, S., and H. Sigurdsson. 2007. Exploring submarine arc volcanoes. Oceanography 20(4):80–89, https://doi.org/10.5670/ oceanog.2007.08. Available at: https://doi.org/10.5670/oceanog.2007.08 This Article is brought to you for free and open access by the Graduate School of Oceanography at DigitalCommons@URI. It has been accepted for inclusion in Graduate School of Oceanography Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. This article has This been published in or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any permitted articleonly photocopy by is of machine, reposting, this means or collective or other redistirbution SP ec I A L Iss U E On Ocean E X P L O R ATIO N Oceanography , Volume 20, Number 4, a quarterly journal of The 20, Number 4, a quarterly , Volume O ceanography Society. Copyright 2007 by The 2007 by Copyright Society. ceanography Exploring O ceanography Society. All rights All reserved. Society. ceanography O Submarine Arc Volcanoes or Th e [email protected] Send Society. ceanography to: correspondence all B Y S T even C A R E Y an D H A R A LDUR SIGURD ss O N Three quarters of Earth’s volcanic activ- although a significant part of arc volca- tion of tsunamis (Latter, 1981). The loss ity occurs beneath the sea, predomi- nism can also occur subaerially. of the Japanese survey vessel Kaio-maru nantly along the extensive mid-ocean Eruptions that take place beneath the in 1952 from an eruption of the shallow P ermission is granted to copy this article for use in teaching and research. article use for research. and this copy in teaching to granted is ermission ridge system that winds its way through sea in arcs contribute to the formation Myojinsho volcano underlines the dan- the major ocean basins. The style of of thick sedimentary sequences (Wright, gers of submarine eruptions that reach eruptive activity along mid-ocean ridges 1996), provide sites for hydrothermal the surface (Fiske et al., 1998). has been extensively studied and well mineralization (Iizasa et al., 1999; de Unlike mid-ocean ridges, the sub- characterized. Submarine eruptions at Ronde et al., 2005), and may be responsi- marine eruptive styles and types of O mid-ocean ridges are dominated by effu- ble for the introduction of biogeochemi- edifice construction within island arcs Society, ceanography sive production of pillow and sheet-flow cally significant components such as Fe have only begun to be explored in detail. lavas at water depths of several thou- into the upper water column (de Ronde The Ocean Exploration program of the sands meters. The other major style of et al., 2001). The impact on biological U.S. National Oceanic and Atmospheric submarine eruptions occurs along island production is likely to be accentuated in Administration (NOAA) pioneered PO Box 1931, arcs where subduction of oceanic crust subantarctic and polar waters where Fe the systematic study of submarine arc triggers melting of mantle rocks by the is a limiting constraint. In shallow water, volcanoes with expeditions in the west- R ockville, M R epublication, systemmatic reproduction, reproduction, systemmatic epublication, release of volatile components, such as the activity of submarine-arc volcanoes ern Pacific (Embley et al., 2004, 2006), water and carbon dioxide. Submarine poses significant hazards from explosive Lesser Antilles (Sigurdsson et al., 2006a), D 20849-1931, volcanism constitutes an important eruptions that can breach the surface and the eastern Mediterranean Sea component of active island arc systems, (Baker et al., 2002) and cause the genera- (Sigurdsson et al., 2006b). Remarkable U SA. 80 Oceanography Vol. 20, No. 4 ...large parts of the world’s subduction zones remain unexplored and present exciting targets for future exploration. discoveries made on these expeditions eth century, volcanologists witnessed for debris avalanche deposits in the deep sea provide new insight into the structure the first time the devastating potential of has been facilitated by the use of side- and behavior of submarine arc volca- unstable volcanic slopes. The resulting scan sonar to identify the characteristic noes. In particular, these discoveries have horseshoe-shaped scar would become hummocky topography of their surfaces allowed scientists to better gauge the the fingerprint of unstable-slope col- (Holcomb and Searle, 1991). potential hazards, geological significance, lapse at many volcanic centers. Such In island arcs such as the Lesser and economic importance of these types collapses may or may not be associated Antilles, slope collapse was first proposed of volcanic centers. with eruptive activity. The recogni- for a number of volcanic centers on tion of numerous and extensive sub- the islands of St. Lucia, Dominica, and COLLAPSING EDIFIces marine debris avalanche deposits and St. Vincent (Roobol et al., 1983). Large The presence of major horseshoe-shaped slumps along the Hawaiian island chain arcuate depressions represented the scars on many oceanic volcanoes led confirmed their important role in the early workers to speculate that large-scale evolution of large intraplate oceanic STeven CAREY ([email protected]) gravitational collapse of island flanks volcanoes (Moore et al., 1994a). Such is Professor, Graduate School of Ocean- was responsible for these distinctive fea- collapses are inferred to have produced ography, University of Rhode Island, tures (Fairbridge, 1950; McBirney, 1971). enormous tsunamis that may have car- Narragansett, RI, USA. HARALDUR When the side of Mount St. Helens col- ried coral fragments up to 60 m above SIGURDssON is Professor, Graduate School lapsed on May 18, 1980, and generated sea level on some of the Hawaiian islands of Oceanography, University of Rhode the largest rock avalanche of the twenti- (Moore et al., 1994b). Recognition of Island, Narragansett, RI, USA. Oceanography December 2007 81 scars of gravity slides that traveled into volcano located just off the island of A reconnaissance survey in 1962 the back-arc Grenada Basin. In a recent Grenada in the Lesser Antilles (Figure 1). showed that the depth to the crater rim study utilizing swath bathymetry, back- The volcano was discovered in 1939 was 223–232 m. The depth decreased scatter data, and seismic reflection pro- when numerous earthquakes were felt, as a result of each successive eruption, files, large-scale, debris-avalanche depos- and tsunamis affected Grenada and reaching a minimum of 160 m by 1978. its were found in the Grenada Basin west the Grenadines, and reached as far as The first detailed survey of the volcano of the islands of Dominica, Martinique, Barbados. An explosive eruption broke in 1972 revealed a 1300-m-high coni- and St. Lucia (Deplus et al., 2001). Sector the surface and produced ash-laden col- cal structure, constructed on the west- collapse and the generation of subma- umns that extended up to 300 m above ern flank of the arc (Sigurdsson and rine debris avalanches thus appears to the sea surface (Devas, 1974). There have Shepherd, 1974). The summit crater be an important process for submarine been at least eleven eruptions since that was found at a depth of 190 m and was and subaerial arc volcanoes (Coombs et event, some of which caused distur- approximately 180 m in diameter. An al., 2007), as well as large oceanic islands bances at the sea surface and small tsu- eruption in 1977 resulted in shallow- such as the Hawaiian chain. namis. Other eruptions, with no surface ing of the volcano’s summit to 160 m, An excellent example of a young manifestations, have been detected only and the summit region was more dome- submarine arc volcano that illustrates by T-phase seismic signals (Shepherd shaped than distinct crater. The first this important process is Kick’em Jenny and Robson, 1967). multibeam survey of the volcano in 1985 confirmed the earlier findings, but showed that the region between the volcanic cone and the Grenada Basin to the west comprises irregular topography (Bouysse et al., 1988). Submersible dives in 1989, a few months after a 1988 erup- 100 tion, revealed that the volcanic cone con- Caribbean Sea sisted of both pyroclastic deposits and pillowlike lava-flow units. The summit Canouan 12°40' region exhibited the remnants of a lava Union Island dome and a breached crater. 1600 Multibeam surveys were undertaken 1500 by the NOAA research vessel Ronald Kick'em Carriacou H. Brown following a December 2001 Jenny eruption. They yielded a high-resolu- 1250 tion image of the volcano and the sur- 12°20' rounding region and revealed important 750 100 new details regarding its structure. The 200 300 most striking feature is a large arcuate 1000 500 600 west-facing scarp that surrounds much 400 Grenada of the volcanic cone to the south, west, 500 250 and north (Figure 2). The new data 12°00' show that the Kick’em Jenny volcanic cone is actually located inside a major 5-km-wide, horseshoe-shaped, west- 62°00' 61°40' 61°20' Figure 1. Location of Kick’em Jenny submarine volcano off the north coast facing amphitheater that most likely was of the island of Grenada in the Lesser Antilles island arc. formed by slope failure and associated 82 Oceanography Vol. 20, No. 4 Figure 2. SeaBeam multibeam bathymetry shadow image in the area of Kick’em Jenny submarine volcano.
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