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

Gaunt, HE; Sammonds, PR; Meredith, PG; Smith, R; Pallister, JS; (2014) Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008. GEOLOGY , 42 (11) 947 - 950. 10.1130/G35940.1. Green open access

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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 ∼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.

Type: Article
Title: Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
Open access status: An open access version is available from UCL Discovery
DOI: 10.1130/G35940.1
Publisher version: http://dx.doi.org/10.1130/G35940.1
Additional information: Copyright © 2014 Geological Society of America. Gold Open Access: This paper is published under the terms of the CC-BY license.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Inst for Risk and Disaster Reduction
URI: https://discovery.ucl.ac.uk/id/eprint/1459892
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