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Effect of temperature on the permeability of lava dome rocks from the 2004–2008 eruption of Mount St. Helens

Gaunt, HE; Sammonds, PR; Meredith, PG; Chadderton, A; (2016) Effect of temperature on the permeability of lava dome rocks from the 2004–2008 eruption of Mount St. Helens. Bulletin of Volcanology , 78 (4) , Article 30. 10.1007/s00445-016-1024-5. Green open access

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Abstract

As magma ascends to shallow levels in the volcanic conduit, volatile exsolution can produce a dramatic increase in the crystal content of the magma. During extrusion, low porosity, highly crystalline magmas are subjected to thermal stresses which generate permeable microfracture networks. How these networks evolve and respond to changing temperature has significant implications for gas escape and hence volcano explosivity. Here, we report the first laboratory experimental study on the effect of temperature on the permeability of lava dome rocks under environmental conditions designed to simulate the shallow volcanic conduit and lava dome. Samples were collected for this study from the 2004–2008 lava dome eruption of Mount St. Helens (Washington State, USA). We show that the evolution of microfracture networks, and their permeability, depends strongly on temperature changes. Our results show that permeability decreases by nearly four orders of magnitude as temperature increases from room temperature to 800 °C. Above 800 °C, the rock samples become effectively impermeable. Repeated cycles of heating leads to sample compaction and a reduction in fracture density and therefore a decrease in permeability. We argue that changes in eruption regimes from effusive to explosive activity can be explained by strongly decreasing permeability caused by repeated heating of magma, conduit walls and volcanic plugs or domes. Conversely, magma becomes more permeable as it cools, which will reduce explosivity.

Type: Article
Title: Effect of temperature on the permeability of lava dome rocks from the 2004–2008 eruption of Mount St. Helens
Open access status: An open access version is available from UCL Discovery
DOI: 10.1007/s00445-016-1024-5
Publisher version: http://dx.doi.org/10.1007/s00445-016-1024-5
Language: English
Additional information: © The Author(s) 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Keywords: Permeability, Mount St Helens, Fractures, Outgassing, Lava domes
UCL classification: UCL
UCL > Provost and Vice Provost Offices
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
URI: https://discovery.ucl.ac.uk/id/eprint/1477331
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