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Changes in degassing potential within cooling lava domes

H. Elizabeth Gaunt1, Adam J. Stinton2,3

  • Affiliations: 1  The Hazard Centre, Department of Earth Science, University College London, WC1E 6BT  2  Montserrat Volcano Observatory, Flemmings, Montserrat, West Indies  3  Seismic Research Centre, University of the West Indies, St Augustine, Trinidad & Tobago, West Indies 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 90

  • Programme No: 3.16.17

  • Theme 3 > Session 16

Abstract

The extrusion of viscous lava domes is often a passive process, but can result in plugging of the conduit and the build up of pressure, causing an explosive event. How easily volcanic gases can move through a lava dome depends on the permeability of the lava and the presence (or not) of large scale degassing pathways. Once lava reaches the surface, it begins to cool, changing its physical properties and state, altering its permeability. Through the use of high temperature experiments, we investigate the impact of changes in these properties on the permeability of samples from Soufrière Hills volcano, Montserrat. During extrusion, internal lava dome temperatures were estimated to around 850°C and measured surface temperatures were reported to be 500-600°C. However, current surface temperatures are near ambient. In addition, the physical properties of the lava extruded over 15 years of eruption have varied significantly. For example, porosity has varied by over 20% over the course of the eruption. Changes in the temperature of the lava dome will alter the potential of gases to move and escape. Permeability experiments at temperatures up to 800°C show that in general, as the lava in the dome cools, permeability increases. Due to differing physical properties, lavas from different phases of the eruption show variations in their response to cooling. Different sections of the lava dome may therefore have different degassing potentials and pathways. This has potential implications for the hazards associated with a restart at volcanoes where recently emplaced lava domes are still present.