Identifying indications of impending explosions in active volcanoes
One of the most difficult aspects of natural disasters is the element of surprise. We’ve gotten much better at forecasting and tracking hurricanes over the years, but events originating underground are understandably harder to keep an eye on. Seismic pressure that trigger earthquakes can be measured, but it’s hard to know when a fault will finally give, releasing built-up energy and shaking buildings on the surface. For a long time, active volcanoes were equally difficult to predict, leaving people to wonder what was mundane rumblings, an what might be leading to an explosion of smoke and magma. Fortunately, new data shows a fairly reliable pattern that may give us some useful predictions about eruption timing and power.
Active versus alarming
It might seem like the most surprising eruptions would come from volcanoes that had been dormant, since their eruptions would be an abrupt change in activity. However, dormant volcanoes usually show many signs of ramping up before erupting, with symptoms like subtle deformations in the surrounding terrain, freshly vented subterranean gas, and seismic activity. Some of these symptoms may go unnoticed to the casual observer, but if monitored, a dormant volcano’s reawakening is likely to be noticed before it erupts.
Active volcanoes that aren’t erupting are the trickier case, since they continually show symptoms of a pending eruption. This makes it hard to know what activity is worth responding to, and what can safely be dismissed as benign rumbling. To look for patterns, sensors were embedded at the Telica Volcano in Nicaragua in 2009 so that a record of activity before an eruption could be analyzed. The pattern that emerged wasn’t so much distinct activity as much as a lack thereof.
Warnings based on wait-time
Out of the 50 explosions that were monitored from Telica, 48 events were immediately precluded by a period of seismic silence. What’s more, the longer the “calm,” the larger the resulting “storm” would be, with a 10 hour quiet period matching up to the largest monitored explosion. Accordingly, shorter pauses, sometimes as little as six minutes, corresponded with less dramatic eruptions. Researchers suspect that these quiet periods are times when normal venting of underground pressure somehow gets blocked due to erosion or other activity, which then build up and need to be released as an explosion. The more time it takes to unclog the blockage, the more time pressurized gas and magma will have to build up. This means that measuring the quiet periods in active volcanoes can be very informative for keeping local populations safe without too many false alarms that wouldn’t pose much of a problem in the first place.
Source: Volcanoes get quiet before they erupt!, Scien Mag