- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Volcanoes: Shaken, but Not Stirred
4 October 2005 (All day)
Volcanoes often announce their intentions through low-frequency earthquakes. Now researchers have a new idea how this happens, and the findings may shed light on why some eruptions are much more violent than others.
Volcanic eruptions range from mild to extreme, depending on the kind of molten rock that's underground. When the lava is thick and viscous, it usually bulges out as a harmless dome. But runnier lava that's full of gas can explode like a fiery champagne bottle. Sometimes these devastating eruptions are presaged by low-frequency temblors. The reason, according to a standard geophysical model--developed by geophysicist Bernard Chouet of the United States Geological Survey (USGS) in Menlo Park, California--is that gas in the magma flows in and out of cracks in the surrounding rock, creating low-frequency seismic waves.
That may not be all that's going on, however. Based on work at the Montserrat Volcano in the West Indies and other volcanoes, a new model suggests that the quakes could occur when slabs of highly viscous magma with low gas content stick momentarily and then slip past one another, producing the vibrations. Steve Malone, a geophysicist at the University of Washington, Seattle, and colleagues believe that new measurements and observations over the past year greatly strengthen the case for this new model. When the team observed magma emerging from the Mount St. Helens' crater in late October 2004, there was no evidence of gas. The magma was quite viscous, Malone says, and the emerging stuff bore a clue: striations along the edges, as though chunks had slid past one another on their way to the surface.
Malone, who will describe his work later this month at a meeting of the Geological Society of America, stresses that the new idea does not replace Chouet's model. But it does complicate predictions of eruption violence, he says, because seismologists can no longer take low-frequency earthquakes as a sure sign of high gas content, and thus higher risk. The viscous magma that Malone's model predicts is likely to ooze slowly from the surface, producing a mild dome-building eruption instead.
"Mt. St. Helens certainly makes a stronger case [for the magma sliding model] that seismologists are going to have to confront," says Seth Moran, a geophysicist with the USGS's David A. Johnston Cascades Volcano Observatory in Vancouver, Washington.