Pre-eruption rumbles help volcano forecasting

Before a volcano erupts it rumbles and shakes the ground, just as an angry dog growls before it bites, says this press release.

The point is that different volcanoes behave in different ways – some rumble consistently, some stop and start, some rumble and erupt straightaway, others rumble for ages before they do anything, and others never get round to erupting at all – and understanding that behaviour helps with eruption forecasting and the issuing of alarms.

Volcano observatories often have a good understanding of these behaviours in the case of their local volcanoes: now Emily Brodsky, associate professor of earth and planetary sciences at the University of California, Santa Cruz, working with Luigi Passarelli of the University of Bologna and Stephanie Prejean of the USGS Alaska Volcano Observatory, has been trying to ‘stitch together those empirical rules with the underlying physics and find some sort of generality’. Professor Brodsky is presenting her findings at the AGU Fall Meeting in San Francisco.

Physics, of course, is only part of the problem with effective forecasting and warning of volcanic eruptions. Psychology is also an issue. The Pasto volcanological observatory in Colombia, which keeps watch on Galeras, has an excellent understanding of Galeras’s behaviour and always issues timely and appropriate warnings, but the local inhabitants do not respond to the alerts because they also feel that they know the volcano very well and don’t believe, from their experience, that its activity will do them any harm. They also weigh up the potential risks of volcanic activity (rather remote) against the risks of leaving their homes, farms and businesses unattended for an unknown length of time (very real) and decide to stay put.

(Press release re-heated here, here and here.)