The pumice raft-forming 2012 Havre submarine eruption was effusive

Journal Article · Wed Mar 07 00:00:00 EST 2018 · Earth and Planetary Science Letters

DOI:https://doi.org/10.1016/j.epsl.2018.02.025· OSTI ID:1479403

Manga, Michael ^[1]; Fauria, Kristen E. ^[2]; Lin, Christina ^[1]; Mitchell, Samuel J. ^[3]; Jones, Meghan ^[4]; Conway, Chris E. ^[5]; Degruyter, Wim ^[6]; Hosseini, Behnaz ^[1]; Carey, Rebecca ^[7]; Cahalan, Ryan ^[8]; Houghton, Bruce F. ^[3]; White, James D. L. ^[9]; Jutzeler, Martin ^[7]; Soule, S. Adam ^[4]; Tani, Kenichiro ^[5]

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1. University of California, Berkeley, CA (United States)
2. University of California, Berkeley, CA (United States); Woods Hole Oceanographic Institute, Woods Hole, MA (United States)
3. University of Hawaii, Manoa, HI (United States)
4. Woods Hole Oceanographic Institute, Woods Hole, MA (United States)
5. National Museum of Nature and Science, Tsukuba (Japan)
6. Cardiff University (United Kingdom)
7. University of Tasmania, Hobart, TAS (Australia)
8. Georgia Institute of Technology, Atlanta, GA (United States)
9. University of Otago, Dunedin (New Zealand)

A long-standing conceptual model for deep submarine eruptions is that high hydrostatic pressure hinders degassing and acceleration, and suppresses magma fragmentation. The 2012 submarine rhyolite eruption of Havre volcano in the Kermadec arc provided constraints on critical parameters to quantitatively test these concepts. This eruption produced a >1 km³ raft of floating pumice and a 0.1 km³ field of giant (>1 m) pumice clasts distributed down-current from the vent. We address the mechanism of creating these clasts using a model for magma ascent in a conduit. We use water ingestion experiments to address why some clasts float and others sink. We show that at the eruption depth of 900 m, the melt retained enough dissolved water, and hence had a low enough viscosity, that strain-rates were too low to cause brittle fragmentation in the conduit, despite mass discharge rates similar to Plinian eruptions on land. There was still, however, enough exsolved vapor at the vent depth to make the magma buoyant relative to seawater. Buoyant magma was thus extruded into the ocean where it rose, quenched, and fragmented to produce clasts up to several meters in diameter. We show that these large clasts would have floated to the sea surface within minutes, where air could enter pore space, and the fate of clasts is then controlled by the ability to trap gas within their pore space. We show that clasts from the raft retain enough gas to remain afloat whereas fragments from giant pumice collected from the seafloor ingest more water and sink. The pumice raft and the giant pumice seafloor deposit were thus produced during a clast-generating effusive submarine eruption, where fragmentation occurred above the vent, and the subsequent fate of clasts was controlled by their ability to ingest water.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: Australian Research Council; Japan Society for the Promotion of Science (JSPS); Marsden Fund; National Defense Science and Engineering Graduation Fellowship; National Science Foundation (NSF); USDOE Office of Science (SC); University of California
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1479403
• Journal Information: Earth and Planetary Science Letters, Journal Name: Earth and Planetary Science Letters Journal Issue: C Vol. 489; ISSN 0012-821X
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
conduit flow
fragmentation
pumice
raft
submarine eruption
x-ray tomography