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Unusual fluidal behavior of a silicic magma during fragmentation in a deep subaqueous eruption, Havre volcano, southwestern Pacific Ocean

journal contribution
posted on 2023-05-20, 02:31 authored by Murch, AP, White, JDL, Rebecca CareyRebecca Carey
Magma responds to applied stresses in either a viscous or elastic manner, depending on the time scales over which strain is accommodated. For silicic magmas, high strain rates of explosive volcanism cause brittle fragmentation and produce abundant small particles (ash). The A.D. 2012 Havre (Kermadec arc, southwestern Pacific Ocean) eruption at ∼900 m water depth deposited a unit of silicic ash with features indicative of syn- and/or post-fragmentation viscous deformation. Viscously deformed ash makes up 3%-35% of the two main ash subunits, S1 and S2, with the remaining ash formed by brittle fragmentation. Viscous behavior of melt during production of fine ash is unexpected for the silicic Havre magma, and for the high strain rates typical of fine fragmentation. The occurrence together of viscous and brittle ash grains suggests local and/or short-term variations in eruption conditions. We infer an explosive eruption mechanism modified by magma-water interaction, during which multi-source steam-veiled fragmentation sites permitted rapid viscous deformation of ash prior to contact with water.

Funding

Australian Research Council

History

Publication title

Geology

Volume

47

Issue

5

Pagination

487-490

ISSN

0091-7613

Department/School

School of Natural Sciences

Publisher

Geological Soc America

Place of publication

Inc, Po Box 9140, Boulder, USA, Co, 80301-9140

Rights statement

Copyright 2019 Geological Society of America

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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