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Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008

H. Elizabeth Gaunt, Peter R. Sammonds, Philip G. Meredith, Rosanna Smith and John S. Pallister
Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
Geology (Boulder) (November 2014) 42 (11): 947-950

Abstract

The ability of volatiles to escape rising magma regulates the explosivity of a volcanic system. During silicic lava dome eruptions, strain localization at the conduit margin occurs during magma ascent, creating a damage halo with implications for gas escape. Here we report the first systematic study of permeability network anisotropy across the marginal shear zone of the A.D. 2004-2008 lava dome at Mount St. Helens (Washington State, USA). The results show increasingly large permeability anisotropy of as much as four orders of magnitude (over approximately 4 m) moving from the interior of the spine through the damage halo. We find the permeability to be essentially isotropic in the spine interior but highly anisotropic in the damage zone and fault core. Our examination of the dome rocks reveals that the permeability anisotropy depends strongly on the presence of vertically oriented shear layers. Here we show that the rate of escape of volatiles will be several orders of magnitude higher vertically through a conduit margin shear zone than horizontally into the conduit wall.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 42
Serial Issue: 11
Title: Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
Affiliation: University College London, Department of Earth Sciences, London, United Kingdom
Pages: 947-950
Published: 201411
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2014-105164
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2014337
Illustration Description: illus.
N46°12'00" - N46°12'00", W122°10'60" - W122°10'60"
Secondary Affiliation: U. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201452
Program Name: USGSOPNon-USGS publications with USGS authors
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