Mt. St. Helens opens a unique 'window into the earth'
Vancouver, Wash. — As Mt. St. Helens continues her periodic rumbling and snorting, scientists from around the world are taking this unique opportunity to study one of Earth's less-well known phenomena. Pouring over the new information that is collected almost hourly, they should be able to more accurately predict (and therefore better prepare for) similar volcanoes in the future.
"We're going to find out an awful lot more about how volcanoes work," said Dr. Richard Stoiber, Dartmouth College volcanologist monitoring the sulphurous dioxide gas that Mt. St. Helens emits. Since a volcano is "a window into the earth," Dr. Stoiber adds, St. Helens also will add new data on general subsurface geology.
Other scientists are analyzing volcanic ash, studying the mud sliding down the mountain's sides, and testing local ground water. Seismographs and tiltmeters have been planted in St. Helens' flanks, aircraft hover overhead to test the steam and gas, and a side-looking radar soon will be in place to measure the mountain's changing size and shape.
The center of activity is the temporary office of the Federal Emergency Management Agency in Vancouver, Wash., just across the Columbia River from Portland. Here, the US Geological Survey (USGS) is coordinating the work of government and university experts from North America and Europe.
USGS geologist Mary Hill explained that Mt. St. Helens and the other 8 to 12 active volcanoes in the Cascade Mountain Range (as well as the other "Ring of Fire" volcanoes around the Pacific rim) are of the "andesitic" type.These are more explosive and unpredictable than the smoother flowing "basaltic" volcanoes such as those in Hawaii and Iceland.
There are some 600 to 800 active volcanoes in the world, with an average of 22 eruptions each year. Most are andesitic.
In modern times, scientists have been able to observe only two andesitic volcanoes. One was in the Soviet Union in 1956, the other in New Guinea five years earlier.
"This type of volcano has not been carefully monitored before," government geologist Hill says. "We probably have the most thoroughly instrumented eruption of this type -- perhaps of any type -- anywhere in the world."
"One thing this volcano will do is give us a much more detailed history of what can happen in the future," she adds. "It should be helpful in at least predicting the sequence of events and perhaps when it will happen in the future."
Scientists are even now better able to tell what Mt. St. Helens is apt to do in coming weeks and months. A possible new bulge has been detected on the mountain's side, plumes of steam have been measured up to 17,000 feet since the second major eruption May 25, and earthquake tremors are being detected daily. Seismologists here now can tell not only the strength of such tremors, but how close to the surface they occur. This can give an indication of how close the next eruption may be.
By monitoring gas venting, scientists also can better describe the magma, or active core content of the volcano. They may find that such venting reduces the pressure that "blows the cork from the bottle," as geologists here put it.
While scientists cannot be absolutely sure that there will be another major eruption, they do know that the last time Mt. St. Helens became active (123 years ago), it erupted 14 times over a quarter-century span.
Dwight Crandell, the USGS's volcano hazards coordinator, says, "Mt. St. Helens is still in an explosive phase and we should expect similar eruptions [ that is, like the lesser one of May 25] in the future."
Meanwhile, as Portland and other communities west of the mountain continue to clean up after the latest eruption, officials reduced the list of missing to 58. The death toll remains at 21.