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Oceanographyra Spocietyhy OceThe OfficiaaL MaganZineog of the Oceanographyra Spocietyhy CITATION Rubin, K.H., S.A. Soule, W.W. Chadwick Jr., D.J. Fornari, D.A. Clague, R.W. Embley, E.T. Baker, M.R. Perfit, D.W. Caress, and R.P. Dziak. 2012. Volcanic eruptions in the deep sea. Oceanography 25(1):142–157, http://dx.doi.org/10.5670/oceanog.2012.12. DOI http://dx.doi.org/10.5670/oceanog.2012.12 COPYRIGHT This article has been published inOceanography , Volume 25, Number 1, a quarterly journal of The Oceanography Society. Copyright 2012 by The Oceanography Society. All rights reserved. USAGE Permission is granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: [email protected] or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. downLoaded from http://www.tos.org/oceanography OCEANIC SPREADING CENTER PROCESSES | Ridge 2000 PROGRAM RESEARCH Volcanic Eruptions in the Deep Sea BY KEnnETH H. RUBIN, S. ADAM SOULE, WILLIAM W. CHADWICK JR., DANIEL J. FORNARI, DAVID A. CLAGUE, RobERT W. EMBLEY, EDWARD T. BAKER, MICHAEL R. PERFIT, DAVID W. CAREss, AND RobERT P. DZIAK Eruption of molten lapilli, ash, and sulfur-rich fumes at Hades vent, West Mata Volcano. 142 Oceanography | Vol. 25, No. 1 AbsTRACT. Volcanic eruptions are important events in Earth’s cycle of magma eruptions, we also discuss submarine generation and crustal construction. Over durations of hours to years, eruptions eruptions in other settings because produce new deposits of lava and/or fragmentary ejecta, transfer heat and magmatic volcanism is a continuum of conditions volatiles from Earth’s interior to the overlying air or seawater, and significantly and processes across the full range of modify the landscape and perturb local ecosystems. Today and through most of tectonic settings and eruption depths, geological history, the greatest number and volume of volcanic eruptions on Earth and because our sample of MOR erup- have occurred in the deep ocean along mid-ocean ridges, near subduction zones, tions is small and, as yet, lacking direct on oceanic plateaus, and on thousands of mid-plate seamounts. However, deep- observation of an ongoing eruption. sea eruptions (> 500 m depth) are much more difficult to detect and observe than Photographs of a variety of deep-sea subaerial eruptions, so comparatively little is known about them. Great strides have eruption styles and deposits (Figure 2) been made in eruption detection, response speed, and observational detail since the depict the two general forms that first recognition of a deep submarine eruption at a mid-ocean ridge 25 years ago. volcanic deposits take: lava flows and Studies of ongoing or recent deep submarine eruptions reveal information about their pyroclasts (volcanic fragments). sizes, durations, frequencies, styles, and environmental impacts. Ultimately, magma Seafloor eruptions punctuate the tran- formation and accumulation in the upper mantle and crust, plus local tectonic stress quility of the deep sea with injections of fields, dictate when, where, and how often submarine eruptions occur, whereas heat, lava, pyroclasts, and gases into the eruption depth, magma composition, conditions of volatile segregation, and tectonic overlying water, affecting its composi- setting determine submarine eruption style. tion, density structure, and ecology (e.g., Delaney et al., 1998; Kelley et al., An ABUNDANCE of This paper provides an overview 2002). The volcanic and tectonic char- SUBMARINE VOLCAnoES of active deep-sea volcanism, here acteristics of MORs vary with spreading There are thousands of submarine taken to mean at water depths greater rate and magma supply (e.g., Macdonald mountains throughout the deep ocean, than approximately 500 m (Mastin et al., 1992; Perfit and Chadwick, 1998; and nearly all of them are volcanoes and Witter, 2000). Representative case Small, 1998). Along fast-spreading (e.g., Smith and Jordan, 1987; Smith and studies describe the general character ridges, small (50–1,000 m tall) volcanoes Cann, 1992). They form long, continuous of eruptions and volcanic histories at merge into a semicontinuous ridge, ridges along seafloor spreading centers, different geological settings. Although producing lava fields several kilometers arcuate chains along subduction zones, our focus is on mid-ocean ridge (MOR) to either side. Slow-spreading ridges are and both linear chains and widely distrib- uted individual seamounts away from Kenneth H. Rubin ([email protected]) is Professor, Department of Geology and plate boundaries. Submarine volcanism Geophysics, University of Hawaii at Manoa, Honolulu, HI, USA. S. Adam Soule is Associate is one of the most important geological Scientist, Geology and Geophysics Department, Woods Hole Oceanographic Institution processes on the planet, forming a dense, (WHOI), Woods Hole, MA, USA. William W. Chadwick Jr. is Professor, Cooperative low-lying, igneous crust that floors the Institute for Marine Resources Studies/Oregon State University, Hatfield Marine Science vast ocean basins and covers nearly two- Center, Newport, OR, USA. Daniel J. Fornari is Senior Scientist, Geology and Geophysics thirds of Earth’s surface. Studies of active Department, WHOI, Woods Hole, MA, USA. David A. Clague is Senior Scientist, Monterey volcanism around the planet provide Bay Aquarium Research Institute, Moss Landing, CA, USA. Robert W. Embley is Senior information that is critical to under- Research Scientist, National Oceanic and Atmospheric Administration (NOAA) Pacific standing the range of volcanic conditions Marine Environmental Laboratory (PMEL), Hatfield Marine Science Center, Newport, OR, in different settings, but they are heavily USA. Edward T. Baker is Supervisory Oceanographer, NOAA PMEL, Seattle, WA, USA. weighted to the subaerial environment Michael R. Perfit is Professor, Department of Geological Sciences, University of Florida, (Figure 1). Deep-sea eruptions are much Gainesville, FL, USA. David W. Caress is Software Engineer, Monterey Bay Aquarium more difficult to detect and observe than Research Institute, Moss Landing, CA, USA. Robert P. Dziak is Professor, Cooperative subaerial eruptions, but knowledge about Institute for Marine Resources Studies/Oregon State University, Hatfield Marine Science them is increasing rapidly. Center, Newport, OR, USA. Oceanography | March 2012 143 Historically active volcanoes (< 500 y) some organisms flourish even when volcanic events make the environment unstable (Tunnicliffe et al., 2003; Fornari et al., 2004; Embley et al., 2006). Our understanding of deep subma- rine volcanism has been greatly aided by mapping and sampling the types and distributions of volcanic products from recent but unknown age erup- tions. In particular, seafloor studies at various MOR sites have provided information about eruption styles, Subaerial (n = 497) Shallow submarine (n = 23) Deep submarine (n = 17) sizes, and frequencies over a broad Figure 1. Sites of historical volcanism on land and in the sea over the past 500 years, based on data from range of dominantly effusive volcanoes the Smithsonian Institution Global Volcanism project and references cited in this paper. Shallow and (e.g., Bryan and Moore, 1977; Ballard deep submarine volcanoes are distinguished because the style of volcanism differs greatly at the two. Note the much higher number of sites on land. Only confirmed (red dot) and likely (pink dot) historical et al., 1979, 1982; Embley and Chadwick, deep submarine eruptions are shown. Likely but unconfirmed eruptions are defined as those lacking a 1994; Sinton et al., 2002, 2010; White dated eruption signal on the seabed and in the water column (i.e., having a seismicity signal and an event et al., 2002; Fornari et al., 2004; Soule plume but no young lava, or having seismicity and visually young lavas but no event plume or high- resolution lava dating). et al., 2005, 2009; Stakes et al., 2006; Escartín et al., 2007). Complementary studies of historical marked by a 5–15 km wide rift valley ocean (e.g., Wolery and Sleep, 1976). deep-sea eruption deposits are key to in which volcanism occurs on elongate Hydrothermal processes create both understanding short-term evolution volcanic ridges (Searle et al., 2010). At focused and diffuse fluid flow into of seafloor volcanic landscapes and MORs, tectonic processes modify the the deep ocean, forming edifices of rapidly changing thermal and subsurface zone of active volcanism, making it diffi- chemical precipitates (e.g., black smoker hydrologic conditions in the uppermost cult to construct large volcanic edifices. chimneys) and creating habitats for crust (e.g., Embley and Chadwick, 1994; In contrast, much of Hawaii’s 10,000 m chemosynthetic animal communities Gregg et al., 1996; Embley et al., 2000, tall Mauna Loa (Earth’s largest active (e.g., Tivey, 1995; Shank et al., 1998; 2006; Perfit and Chadwick, 1998; Soule volcano) was built by many thousands Luther et al., 2001). Chemosynthetic et al., 2007). Ideally, these features are of submarine eruptions over about a ecosystems are sensitive to hydrothermal studied before they are modified by million years at roughly the same loca- fluid compositions, which change with post-eruption faulting, volcanic collapse, tion in the middle of the Pacific Plate. time and distance from the magmatic and background sedimentation, which Magmas
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