Monday, July 15, 2013

Volcanic 'scream' precedes explosive eruptions

Redoubt eruption in 2009 AVO/USGS 

The researchers studied the eruption of Redoubt in 2009

A change in the frequency of earthquakes may foretell explosive volcanic eruptions, according to a new study.

The seismic activity changes from steady drum beats to increasingly rapid successions of tremors.

These blend into continuous noise which silences just before explosion.

The study of tremors in the lead up to the 2009 eruption of Redoubt, a volcano in Alaska, appears in Journal of Volcanology and Geothermal Research.

Those quakes continuously rose in pitch like a volcanic glissando - a musical glide from one pitch to another.

Subterranean magma plumbing systems sit beneath volcanoes and feed pressurised molten rock toward the surface before eruptions.

As the magma flows through deep conduits and cracks, it generates small seismic tremors and earthquakes.

Scientists have noted earthquakes preceding volcanic eruptions before, for example drumbeat earthquakes were the first sign of renewed magmatic activity in Mount St Helens in April 2005. 

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