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Autopsy of an eruption: Linking crystal growth to volcano seismicity

False colour image of zoned orthopyroxene crystal used in forensic-style analysis of Mount St Helens 1980 eruption

False colour image of zoned orthopyroxene crystal used in forensic-style analysis of Mount St Helens 1980 eruption Dr Kate Saunders

Press release issued: 24 May 2012

A forensic approach that links changes deep below a volcano to signals at the surface is described by scientists from the University of Bristol in a paper published today in Science. The research could ultimately help to predict future volcanic eruptions with greater accuracy.

Using forensic-style chemical analysis, Dr Kate Saunders and colleagues directly linked seismic observations of the deadly 1980 Mount St. Helens eruption to crystal growth within the magma chamber, the large underground pool of liquid rock beneath the volcano.

Over 500 million people live close to volcanoes which may erupt with little or no clear warning, causing widespread devastation, disruption to aviation and even global effects on climate.  Many of the world’s volcanoes are monitored for changes such as increases in seismicity or ground deformation.  However, an on-going problem for volcanologists is directly linking observations at the surface to processes occurring underground.

Dr Saunders and colleagues studied zoned crystals, which grow concentrically like tree rings within the magma body.  Individual zones have subtly different chemical compositions, reflecting the changes in physical conditions within the magma chamber and thus giving an indication of volcanic processes and the timescales over which they occur. 

Chemical analysis of the crystals revealed evidence of pulses of magma into a growing chamber within the volcano.  Peaks in crystal growth were found to correlate with increased seismicity and gas emissions in the months prior to the eruption.

Dr Saunders said: “Such a correlation between crystal growth and volcanic seismicity has been long anticipated, but to see such clear evidence of this relationship is remarkable.”

This forensic approach can be applied to other active volcanoes to shed new light upon the nature and timescale of pre-eruptive activity.  This will help scientists to evaluate monitoring signals at restless volcanoes and improve forecasting of future eruptions.

The research was funded by the Natural Environment Research Council (NERC).

Paper

‘Linking Petrology and Seismology at an Active Volcano’ by Kate Saunders, Jon Blundy, Ralf Dohmen, Kathy Cashman in Science

The Cabot Institute

The Cabot Institute at the University of Bristol carries out fundamental and responsive research on risks and uncertainties in a changing environment.  Our interests include natural hazards, food and energy security, resilience and governance, and human impacts on the environment. Our research fuses rigorous statistical and numerical modelling with a deep understanding of interconnected social, environmental and engineered systems – past, present and future. We seek to engage wider society – listening to, exploring with, and challenging our stakeholders to develop a shared response to 21st Century challenges.

The Natural Environment Research Council (NERC)

The Natural Environment Research Council (NERC) is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, environmental influences on human health, the genetic make-up of life on earth, and much more.   NERC receives around £300 million a year from the government's science budget, which it uses to fund independent research and training in universities and its own research centres.

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