High-temperature fracture mechanics of dome lava
Lead Research Organisation:
University College London
Department Name: Earth Sciences
Abstract
Volcanoes that erupt highly-viscous lava domes are amongst the most hazardous, intensely studied and newsworthy of geological phenomena, as the past twenty-five years of activity at Mount St Helens, USA have demonstrated. A key challenge in geological science is how to predict reliably the sudden changes in behaviour that are typical of such domes, from gentle lava effusion to devastating explosive eruptions. Much progress has been made in recent years in studying eruptive behaviour, with the realisation that the material response of magma to applied stresses largely controls eruption mechanisms and the rheology of dome lava changes greatly during shallow degassing and crystallisation. A goal of the current generation of models for dome growth is to identify thresholds in behaviour (e.g. explosive/effusive eruptions, endogenous/exogenous dome growth) that are closely related to the fundamental physical behaviour of whether deforming magma will fracture or flow. We propose to do experiments in the laboratory on lava dome material from the recent eruption of Mt St Helens under simulated volcanic conditions. These expriments will establish the thresholds for dome growth and explosive eruptions. Acoustic emissions will also be measured during these laboratory experiments, so that the laboratory experiments can be related to observed volcano seismicity.These laboratory studies will provide direct input into the development of the current generation of models of volcanic dome behaviour.
Organisations
Publications
Gaunt H
(2014)
Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
in Geology
Smith R
(2011)
Evolution of the mechanics of the 2004-2008 Mt. St. Helens lava dome with time and temperature
in Earth and Planetary Science Letters
Smith R
(2010)
Forecasting eruptions after long repose intervals from accelerating rates of rock fracture: The June 1991 eruption of Mount Pinatubo, Philippines
in Journal of Volcanology and Geothermal Research
Smith R
(2009)
Fracturing of volcanic systems: Experimental insights into pre-eruptive conditions
in Earth and Planetary Science Letters
Lavallée Y
(2008)
Seismogenic lavas and explosive eruption forecasting
in Nature
Tuffen H
(2008)
Evidence for seismogenic fracture of silicic magma.
in Nature
Benson PM
(2008)
Laboratory simulation of volcano seismicity.
in Science (New York, N.Y.)
Smith R
(2006)
Rock fracture as a precursor to lava dome eruptions at Mount St Helens from June 1980 to October 1986
in Bulletin of Volcanology
Description | It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of ? 600 deg C. This thinking underpins our understanding of volcanic earth- quakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? We showed by deforming high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting. |
Exploitation Route | Our work is much cited and has stimulated further research into the fundamentals of volcano lava dome stability. |
Sectors | Environment |
Description | Better understanding of precursors to volcanic eruptions. |
First Year Of Impact | 2015 |
Sector | Environment |
Impact Types | Societal,Policy & public services |
Description | Studentship |
Amount | £60,000 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
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