May 25th, 2012 by James Ayre
A new forensic approach that links changes deep within a volcano to surface observations has just been described by scientists in a new study published in Science. The research may help develop volcanic prediction of great accuracy.
Using chemical analysis the researchers directly linked seismic observations of the Mt. St. Helen’s eruption in 1980 to crystal growth in its magma chamber. The magma chamber is the large pool of liquid rock beneath the volcano.
Half-a-million people in the world live close to volcanos that can erupt with little or no warning, leading to widespread destruction, airway disruption, and effects on climate. Most of the most dangerous volcanoes in the world are actively monitored via seismicity readings and signs of ground deformation. However the signs currently used to predict impending eruptions aren’t that reliable. The processes occurring at the surface and deep underground aren’t necessarily suggestive of one another.
“False colour image of zoned orthopyroxene crystal used in forensic-style analysis of Mount St Helens 1980 eruption.”
The researchers studied zoned crystals, which grow concentrically like tree rings within the magma body. Individual zones have subtle chemical differences, reflecting the physical changes in the magma chamber, thusly giving insight into the volcanic processes and the timescales on which they occur.
Chemical analysis of the crystals revealed evidence of pulses of magma into the growing chamber in a volcano. Peaks in the crystal growth correlated with the increased seismic activity and gas emissions in the months prior to the eruption.
Dr Kate Saunders, one of the study authors 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 approach can be applied to active volcanoes to give insight into the nature and timescales of pre-eruptive activity. This will help researchers to evaluate monitoring signals at active volcanoes and improve forecasting of volcanic eruptions.
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