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Experimental simulations of explosive degassing of magma.

Mader, Heidy and Zhang, Y. and Phillips, J. C. and Sparks, R. S. J. and Sturtevant, B. and Stolper, E. (1994) Experimental simulations of explosive degassing of magma. Nature, 372 (6501). pp. 85-88. ISSN 1476-4687

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Abstract

The violent release of volatiles in explosive volcanic eruptions is known to cause fragmentation of magma and acceleration of the resulting mixture of gas and pyroclasts to velocities exceeding 100 m s-1 (ref. 1). But the mechanisms underlying bubble nuclea-tion, flow acceleration and fragmentation are complex and poorly understood. To gain insight into these phenomena, we have simu-lated explosive eruptions using two model systems that generate expansion rates and flow velocities comparable to those observed in erupting volcanos. The key feature of both experiments is the generation of large supersaturations of carbon dioxide in a liquid phase, achieved either by decompressing CO2-saturated water or by rapid mixing of concentrated K2CO3 and HC1 solutions. We show that liberation of CO2 from the aqueous phase is enhanced by violent acceleration of the mixture, which induces strong exten-sional strain in the developing foam. Fragmentation then occurs when the bubble density and expansion rate are such that the bubble walls rupture. In contrast to conventional models of fragmentation1,2, we find that expansion and acceleration precede—and indeed cause—fragmentation.

Item Type: Article
Journal or Publication Title: Nature
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 22483
Deposited By: ep_ss_importer
Deposited On: 29 Jan 2009 10:21
Refereed?: Yes
Published?: Published
Last Modified: 09 Apr 2014 20:26
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/22483

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