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Fragmentation of a porous viscoelastic material: Implications to magma fragmentation

Ichihara, Mie and Rittel, Daniel and Sturtevant, Bradford (2002) Fragmentation of a porous viscoelastic material: Implications to magma fragmentation. Journal of Geophysical Research B, 107 (B10). Art. No. 2229. ISSN 0148-0227. doi:10.1029/2001JB000591. https://resolver.caltech.edu/CaltechAUTHORS:20141027-104725013

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Abstract

Fragmentation of vesicular magma by rapid decompression is one of the most likely triggers for explosive eruptions. In this phenomenon the decompression rate and the viscoelastic nature of magma are considered to be key factors. In order to obtain a clear idea on the effects of these two factors, controlled fragmentation experiments have been conducted. These experiments have three advantages. First, the specimen is made of a viscoelastic material with controlled porosity and geometry. Second, the fragmentation process is directly monitored. Finally, both the magnitude and rate of decompression are controlled. Brittle fragmentation and ductile expansion were both observed in the same porous material at different timescales. The various mechanical responses of the specimen (elastic, flow, and fragmentation) were correlated with the pressure profile measured at the base of the specimen. Fragmentation was noted to occur when the decompression exceeded a critical value within a critical time. Two relevant timescales are discussed in terms of physical mechanisms of relaxation. The first is the measured glass transition time. The second is the estimated timescale for the onset of viscous bubble expansion. The observed phenomena bear several similarities with natural magma fragmentation. It is thus considered that the present results are a useful step toward constructing a model for magma fragmentation.


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Additional Information:Copyright 2002 by the American Geophysical Union. Received 29 October 2001; revised 31 December 2001; accepted 4 January 2002; published 15 October 2002. This work was supported by the Japan Society for the Promotion of Science. We thank O. Spieler and D. B. Dingwell for their helpful comments and providing us with their results (Figure 15). We are grateful to Y. Takei for help with the ultrasonic test, Rheometrics Scientific F. E. Ltd. for technical assistance with the rheometer test, and Dow Corning Corporation for providing us with the test material. T. Koyaguchi, E. E. Brodsky, and M. Kameda are acknowledged for the constructive discussions and encouragement throughout this study. Bradford Sturtevant passed away on 20 October 2000. M. Ichihara and D. Rittel dedicate this paper to his memory.
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Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:fragmentation; eruption; rheology; experimental volocanology; magma; viscoelasticity
Issue or Number:B10
Classification Code:8414 Volcanology: Eruption mechanisms; 5104 Physical Properties of Rocks: Fracture and flow; 8429 Volcanology: Lava rheology and morphology; 3210 Mathematical Geophysics: Modeling
DOI:10.1029/2001JB000591
Record Number:CaltechAUTHORS:20141027-104725013
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141027-104725013
Official Citation:Ichihara, M., D. Rittel, and B. Sturtevant, Fragmentation of a porous viscoelastic material: Implications to magma fragmentation, J. Geophys. Res., 107(B10), 2229, doi:10.1029/2001JB000591, 2002
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50844
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:27 Oct 2014 18:14
Last Modified:10 Nov 2021 19:01

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