Campus Units

Geological and Atmospheric Sciences

Document Type

Article

Publication Version

Published Version

Publication Date

8-2010

Journal or Book Title

Bulletin of Volcanology

Volume

72

Issue

6

First Page

761

Last Page

766

DOI

10.1007/s00445-010-0377-4

Abstract

Rock shear strength plays a fundamental role in volcano flank collapse, yet pertinent data from modern collapse surfaces are rare. Using samples collected from the inferred failure surface of the massive 1980 collapse of Mount St. Helens (MSH), we determined rock shear strength via laboratory tests designed to mimic conditions in the pre-collapse edifice. We observed that the 1980 failure shear surfaces formed primarily in pervasively shattered older dome rocks; failure was not localized in sloping volcanic strata or in weak, hydrothermally altered rocks. Our test results show that rock shear strength under large confining stresses is reduced ∼20% as a result of large quasi-static shear strain, as preceded the 1980 collapse of MSH. Using quasi-3D slope-stability modeling, we demonstrate that this mechanical weakening could have provoked edifice collapse, even in the absence of transiently elevated pore-fluid pressures or earthquake ground shaking. Progressive strength reduction could promote collapses at other volcanic edifices.

Comments

This article is published as Reid, Mark E., Terry EC Keith, Robert E. Kayen, Neal R. Iverson, Richard M. Iverson, and Dianne L. Brien. "Volcano collapse promoted by progressive strength reduction: new data from Mount St. Helens." Bulletin of Volcanology 72, no. 6 (2010): 761-766. DOI: 10.1007/s00445-010-0377-4.

Rights

Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.

Language

en

File Format

application/pdf

Included in

Volcanology Commons

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