Pumice Eruption in the Area of the South Sandwich Islands

Gass, I. G.; Harris, Peter; Holdgate, M. W.

doi:10.1017/s0016756800056053

Cited by 54 publications

(26 citation statements)

References 3 publications

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“…Estimated caldera volumes range from 0.4-0.9 km 3 for the two nested Quest calderas to 3 km 3 for Resolution and 9-12 km 3 for Douglas Strait, Adventure and Kemp. The Quest volumes are within an order of magnitude of the 0.2 km 3 estimated volume of magma erupted during the dacite-rhyolite eruption of 1962 (Gass et al, 1963;Leat et al, 2007), suggesting that they could have formed during a single similar eruptive event. The larger caldera volumes in the southern volcanoes of the arc may be products of multiple eruptive events as documented for comparable Kermadec arc calderas (Barker et al, 2012).…”

Section: Caldera Collapsementioning

confidence: 66%

“…Newly found seamounts are likely to be biodiversity hotspots, especially where hydrothermally active. New discoveries of submarine hydrothermal vents with associated communities in the backarc and arc are among the most remote in the World's oceans (Rogers et al, 2012).All the volcanoes forming the curved volcanic front are recently volcanically active or currently hydrothermally active, or both (Holdgate, 1963;Gass et al, 1963;Baker, 1990;Lachlan-Cope et al, 2001;Leat et al, 2003;Patrick et al, 2005;Patrick and Smellie, 2013). Even within the short period (less than 100 years) of historical records, eruptions from the South Sandwich arc have been varied, ranging from submarine explosive eruptions (Protector Shoal, 1962) through strombolian eruptions with associated lava flows (Montagu Island, 2001 and Bristol Island, 1956, to possible lava lake activity (Saunders Island, 1995.…”

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confidence: 99%

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Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Leat

Day

Tate

et al. 2013

Journal of Volcanology and Geothermal Research

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New multibeam bathymetry data are presented for the South Sandwich intra-oceanic arc which occupies the small Sandwich plate in the South Atlantic, and is widely considered to be a simple end-member in the range of intra-oceanic arc types. The images show for the first time the distribution of submarine volcanic, tectonic and erosional-depositional features along the whole length of the 540 km long volcanic arc, allowing systematic investigation of along-arc variations. The data confirm that the volcanic arc has a simple structure composed of large volcanoes which form a well-defined volcanic front, but with three parallel crosscutting seamount chains extending 38-60 km from near the volcanic front into the rear-arc. There is no evidence for intra-arc rifting or extinct volcanic lines. Topographic evidence for faulting is generally absent, except near the northern and southern plate boundaries. Most of the volcanic arc appears to be built on ocean crust formed at the associated back-arc spreading centre, as previously proposed from magnetic data, but the southern part of the arc appears to be underlain by older arc or continental crust whose west-facing rifted margin facing the back-arc basin is defined by the new bathymetry. The new survey shows nine main volcanic edifices along the volcanic front and ca. 20 main seamounts. The main volcanoes form largely glaciated islands with summits 3.0-3.5 km above base levels which are 2500-3000 m deep in the north and shallower at 2000-2500 m deep in the south. Some of the component seamounts are interpreted to have been active since the last glacial maximum, and so are approximately contemporaneous with the volcanic front volcanism. Seven calderas, all either submarine or ice-filled, have been identified: Adventure volcano, a newly discovered submarine volcanic front caldera volcano is described for the first time. All but one of the calderas are situated on summits of large volcanoes in the southern part of the arc, and most are associated with current or historic volcanic or hydrothermal activity. Shallow shelves around the islands are generally 1-10 km wide. Submerged banks up to 1100 m deep are interpreted as subsided erosional surfaces. Seamounts and emergent volcanoes experienced a range of mass wasting processes including by landsliding and smaller mass flows. KeywordsVolcanic arc, subduction zone, caldera, seamount, submarine volcanism The importance of the South Sandwich volcanic arcThe South Sandwich volcanic arc, situated in the South Atlantic ( Fig. 1), is a tectonically simple, active, intra-oceanic arc, and is ideally suited to studies of volcanic arc crustal structure, geochemical investigation of mantle processes above a subduction zone, and sedimentation in an early stage of arc evolution. The active arc is built largely on oceanic crust of the small Sandwich plate which formed about 10 Ma at the back-arc East Scotia ridge spreading centre . The arc is forming in response to steeply inclined subduction of the South American plate beneath the Sand...

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Section: Caldera Collapsementioning

confidence: 66%

mentioning

confidence: 99%

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Leat

Day

Tate

et al. 2013

Journal of Volcanology and Geothermal Research

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“…In the sub-Antarctic, the most likely regions are the Scotia Arc ( fig. 3) 27 m below sea level) erupted a vast raft of pumice (Gass et al 1963, Sutherland & Olsen 1968. That raft circled the Southern Hemisphere for many years, slowly becoming more dispersed, the fragments smaller, and providing glass shards to the seafloor to contribute to the sediment.…”

Section: Earthquakesmentioning

confidence: 99%

Extreme events in the sub-Antarctic

Quilty¹

2012

PPRST

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Extreme physical events, excluding meteorological events, can be divided into two broad categories -endogenous and exogenous. Endogenous phenomena include earthquakes, landslides, tsunami, volcanic or gas hydrate eruptions that occur within the region but may have both local and distant impacts; the 2011 Puyehue-Cordon Caulle volcanic eruption, and the frequent major earthquakes along the Chile margin or near Macquarie Island are examples. Exogenous events are those originating outside the area but influencing it. These include the terminal Cretaceous asteroid impact, asteroid/meteorite impacts, such as the major Eltanin Asteroid impact 2.5 million years ago, and extraterrestrial-sourced radiation from extreme solar/galactic or extra-galactic events in which the effect is not confined to the sub-Antarctic but is global.

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“…Submarine eruption and hydrothermal plumes can buoyantly rise to the sea surface, producing sea-rafted pumice that is subsequently dispersed by ambient currents and winds (Gass et al 1963;Kokelaar and Durant 1983;Fiske et al 1998;Cashman and Fiske 1991). Syn-eruptive plumes have been observed during two modern eruptions from shallow (<250 m water depth) Kermadec volcanoes (Latter et al 1992).…”

Section: Pumice Dispersal and Agementioning

confidence: 99%

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

2002

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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 ≤30 mm vesicles and weakmoderate foliation, type 2 grey pumice with millimetrescale laminae, flow banded foliation, including stretched vesicles ≤55 mm in length, and a minor finely vesicular type 3 pumice. All types are sparsely porphyritic, with undevitrified glassy groundmass (68-70% SiO 2 ), which is microlite and lithic free. Coexisting pyroxenes yield magma temperatures of ~950°C. Pumice density is ≤0.5 g cm -3 and vesicularity is 78-83%. Vesicle size distributions for types 1 and 2 pumice, range from ~20 µm to >20 mm, with a strong power-law relation (with d=-2.5±0.4) for vesicles <1-2 mm. Larger vesicles have variable size modes. The vesicle size distribution and packing indicates rapid magma decompression and ascent. Consideration of the pressure dependent, solubility of H 2 O at a magma temperature of ≤950°C and water content of ≤6 wt%, with pumice petrography and vesicle granulometry, strongly suggests a pyroclastic eruption. Reconstructions of the submarine edifice between water depths of 1,000 and 550 m constrain the ambient hydrostatic pressure to ~6-9 MPa. Pressures >~9 MPa will limit vesicularity to less than the observed 78-83%, whereas pressure <~6 MPa require a more shallower reconstruction of the edifice and larger-volume syn-eruptive collapse. Uniformly high vesicularity is interpreted as evidence of insulation within an eruption column comprising steam and hot pyroclasts. Most pyroclasts cool, condensing and ingesting water into steam-inflated vesicles, and then sink. Progression into pyroclastic mode would expand the eruption column, displace ambient water, reduce the hydrostatic load, and further promote vesiculation and fragmentation. Pyroclasts within the column would quench at these reduced pressures. We argue that Healy eruptions deeper than ~1,000 m cannot be pyroclastic. Volumes for the lower and upper bounds of edifice size are 2.36 and 3.58 km 3 , respectively, but do not account for intra-caldera pumice fill. These volumes are considered to be predominantly primary eruption output, as shown by a dearth of accessory lithics in all pumice, yielding (at an average 81% vesicularity) eruptive pumice volumes of between 10 and 15 km 3 . Some pyroclasts may have risen to the sea surface and be a correlative of the sea-rafted Loisels pumice; the latter occurs in some New Zealand Holocene beach sequences and has a estimated age of 590±80 calendar years.

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Pumice Eruption in the Area of the South Sandwich Islands

Cited by 54 publications

References 3 publications

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Extreme events in the sub-Antarctic

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

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