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Sink or float: microtextural controls on the fate of pumice deposition during the 2012 submarine Havre eruption

Citation

Mitchell, SJ and Fauria, KE and Houghton, BF and Carey, RJ, Sink or float: microtextural controls on the fate of pumice deposition during the 2012 submarine Havre eruption, Bulletin of Volcanology, 83 Article 80. ISSN 0258-8900 (2021) [Refereed Article]


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DOI: doi:10.1007/s00445-021-01497-6

Abstract

Silicic submarine volcanic eruptions can produce large volumes of pumices that may rise buoyantly to the ocean surface and/or sink to the seafloor. For eruptions that release significant volumes of pumice into rafts, the proximal to medial submarine geologic record is thus depleted in large volumes of pumice that would have sedimented closer to source in any subaerial eruption. The 2012 eruption of Havre volcano, a submarine volcano in the Kermadec Arc, presents a unique opportunity to study the partitioning of well-constrained rafted and seafloor pumice. Macro- and microtextural analysis was performed on clasts from the Havre pumice raft and from coeval pumiceous seafloor units around the Havre caldera. The raft and seafloor clasts have indistinguishable macrotextures, componentry, and vesicularity ranges. Microtextural differences are apparent as raft pumices have higher vesicle number densities (109 cm−3 vs. 108 cm−3) and significantly lower pore space connectivity (0.3–0.95 vs. 0.9–1.0) than seafloor pumices. Porosity analysis shows that high vesicularity raft pumices required trapping of gas in the connected porosity to remain afloat, whereas lower vesicularity raft pumices could float just from gas within isolated porosity. Measurements of minimum vesicle throat openings further show that raft pumices have a larger proportion of small vesicle throats than seafloor pumices. Narrow throats increase gas trapping as a result of higher capillary pressures acting over gas–water interfaces between vesicles and lower capillary number inhibiting gas bubble escape. Differences in isolated porosity and pore throat distribution ultimately control whether pumices sink or float and thus whether pumice deposits are preserved or not on the seafloor.

Item Details

Item Type:Refereed Article
Keywords:submarine volcanism, pumice raft, microtextures, connected porosity, pore throats, gas trapping, pumice, volcano, eruption, havre
Research Division:Earth Sciences
Research Group:Geology
Research Field:Geology not elsewhere classified
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Carey, RJ (Associate Professor Rebecca Carey)
ID Code:147429
Year Published:2021
Funding Support:Australian Research Council (DE150101190)
Web of Science® Times Cited:2
Deposited By:Earth Sciences
Deposited On:2021-10-31
Last Modified:2022-05-16
Downloads:0

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