Little crystals, big bangs: A step toward lahar warnings
Predicting volcanic eruptions is of more than academic interest in this part of the country.
The Cascade Range contains a string of giant powder kegs – Mount St. Helens, Mount Rainier and Mount Baker among them – that can explode with the force of nuclear weapons. Eruptions would be less of a worry if we had some advance warning, but Mother Earth tends to play her cards close to the vest.
Volcanologists may be teasing out some of her secrets, though. An article in last week’s issue of Science magazine described a newly discovered link between underground crystals and the surges of magma that turn snow-covered peaks into steaming, fulminating killers.
Mount St. Helens was the researchers’ test subject. Studying its rocks, a team based at the University of Bristol in England found patterns closely correlated to the volcano’s fits of anger. Their electron microscopes revealed that the tiny “orthopyroxene” crystals were reliable indicators of what the underground magma was up to during their formation.
The chemistry of the crystals reportedly reflected the properties of nearby molten rock, including pressures, vapor content and movement. The scientists matched these profiles with eruptions that occurred between 1980 and 1986. It turned out that crystals formed when the mountain was getting ready to blow up had distinct chemical fingerprints marked by high levels of iron or magnesium.
Unfortunately, there’s no immediate way to turn this discovery into a warning system. Continuously sampling the crystals in formations below the flanks of a giant mountain isn’t a practical option.
But this discovery suggests that it’s at least theoretically possible to predict upswells of magma, given more knowledge and more sophisticated detection systems.
Early detection could be a lifesaver here. The biggest risk from Mount Rainier is not the stuff that would come out its top – ash, lava and boulders – during an eruption. A far greater threat are the floods of water, boulders and debris known as lahars. Mount Rainier – encased in a cubic mile of ice – has a long history of heating up and sloughing off lahars into the valleys fed by its glaciers.
A massive lahar racing down the Puyallup River Valley would put tens of thousands of people in grave danger. Mount Rainier’s destructive potential makes it one of the world’s most dangerous volcanoes.
The report in Science is a sobering reminder that we have a time bomb in our backyard. It’s also an encouraging hint that we might someday be able to tell when the bomb is about to go off.
