When Do Scientists Predict Mt St Helens Will Erupt Again

When earthquakes started jolting Mount St. Helens in March, 1980, little infrastructure was available to monitor the mountain or warn of an eruption. As the quakes continued, scientists scavenged seismographs and surveying equipment to take the mount'south pulse. Their agenda combined science (What is going on within the volcano?) and public service (When and how should we warn residents and touristo-gawkers?)

The real thing: During the 1980 eruption, Mount St. Helens spewed superheated ash, stone and gas. Photo: USGS

After a couple of months of nervus-wracking foreplay, St. Helens exploded on May 18. Fifty-7 people died, mainly because the eruption started with a rare but phenomenally powerful sideways blast. Crusty sometime Harry Truman, who had become a media hero by refusing to go out his chemical compound at Spirit Lake, died under a gigantic landslide.

St. Helens taught scientists a corking deal nigh how volcanoes piece of work -- or at least, how that particular volcano works, says Steve Malone, who watched the events from a seismology lab at the Academy of Washington, where he at present heads the Pacific Northwest Seismograph Network.

The experience, he says, was "like a baptism of fire" that "got us a huge leg up" on the difficult problem of predicting eruptions.

Volcanoes give 4 major categories of data that can serve as a basis for predictions:

Geologic history: What has this volcano done in the past? How regular and frequent were the eruptions, and what did they do?

Land deformation: Ascension magma changes the surface in and nearly the crater. Broad deformation indicates that the magma is deep, while more focused deformation signifies shallow magma, and perhaps an eruption in the near future.

Gas emissions: Rising magma releases gases like carbon dioxide and sulfur dioxide. The timing and intensity of these gases hints at the magma's location.

Earthquakes: Ascent magma must bust through rock, and the resulting quakes may be the best unmarried indication of magma movement.

Each of these factors became the field of study of intense scrutiny as St. Helens rocked and rolled in jump, 1980. Just ii years before, a U.South. Geological Survey study had predicted that the volcano might erupt before 2000. "Information technology was a long-range forecast based on the geological record" of adequately regular eruptions, says Dan Dzurisin, a volcanologist with the Cascades Volcano Observatory.

1973, 1983 and 2000: The time machine at Mount St. Helens. These satellite pix show the surface area before and after the 1980 eruption, and after twenty years of ecological healing. 284KB Moving-picture show: Landsat, NASA

Although there were plenty of warnings, there were no eruption forecasts as such in 1980, Dzurisin says. "Clearly nosotros issued statements anticipating eruptive activity, but the exact timing was hard to forecast. Fifty-fifty in retrospect, on May eighteen, 1980, at that place was nothing we were measuring that could have offered whatsoever short-term alarm that it would start that morning time."

Subsequently the cataclysmic eruption, however, it was piece of cake to find enquiry funding on St. Helens, and the ensuing scientific activity paid off during a series of minor eruptions. "Nosotros began to encounter a pattern repeated ... with increased seismicity and deformation of the crater floor," Dzurisin says. "In well-nigh cases, a new lava lobe would extrude onto the surface. From December, 1980, to October, 1986, we successfully predicted each dome-edifice eruption, at least 18 of them, as far every bit three weeks in advance, although sometimes it was just hours in advance." Domes are mounds of lava that form, usually inside the existing crater.

Using seismology only, scientists as well predicted iv of five explosive eruptions in the summer of 1980, Malone adds.

St. Helens fabricated history, and not just for the behemothic landslide, says Dzurisin. "For the showtime fourth dimension, were willing to step upward to the plate and predict the style and timing of eruption events. It'south off-white to say this was a watershed, and since then, information technology has become more common to make specific forecasts."

Sept. 30, 2004: U.S. Geological Survey scientist Dan Dzurisin collects information from a Global Positioning System station on the east flank of St. Helens. Since intense earthquakes started Sept. 23, more than a dozen GPS stations have measured surface deformation. Photo: Michael Poland, USGS.

St. Helens offered two types of lessons, says Dzurisin. "At that place are two aspects to an eruption forecast. 1 is pattern recognition. If you meet the same thing happening repeatedly, you lot are in a position to forecast the next occurrence. To a large extent, that'southward what we used for the dome-building forecasts at Mount St. Helens."

A second aspect is agreement what'south going on inside an active volcano. "If nosotros empathise the processes, even if the pattern changes, we should be in a position to understand why they might accept changed, and nonetheless provide some form of forecast," Dzurisin adds. Although achieving such an understanding is "much more than difficult," it'southward as well potentially more than helpful, since it might utilise to other volcanoes.

Since 1980, the biggest advances in forecasting have come up from seismology, says Dzurisin, who was at the Hawaii Volcano Observatory earlier St. Helens. "At HVO, we counted the number of quakes per twenty-four hour period. ...At present, instead of maxim, we had 250 quakes yesterday and 324 today, we say" that groundwater or magma seems to be moving inside the volcano, based on the size and shape of traces on the seismograph.

Oct. half-dozen, 2004: Traces of seismic activity at Mount St. Helens. These fiddling squiggles read the eye of the volcano. Courtesy Pacific Northwest Seismograph Network

In 1991, the lessons of Mount St. Helens were tested in the Philippines, after the ground began shaking around Mountain Pinatubo, a short mountain but productive volcano. A collaboration of U.S. and Filipino volcanologists watched, waited, and eventually made an authentic forecast. "At that place was no question that the learning curve took a huge bound at St. Helens, and they succeeded at Pinatubo, it was a dramatically successful forecast," says Malone, who adds that he was not involved in Pinatubo.

The Philippine government evacuated tens of thousands of residents, saving massive casualties during the largest eruption of the 20th century. Although gigantic mud flows and ash deposits pb to the closing of two major U.s.a. military bases, few lives were lost.

No evacuation warnings have been issued around Mountain St. Helens, where, as we write, in October, 2004, magma has risen to a few hundred meters below the surface, and a lava dome is forming in the crater. "The fact that the deformation is very localized tells usa that the firsthand crusade is very shallow," Dzurisin said.

October. 1, 2004: A minor eruption of Mount St. Helens; the first in more than a decade -- followed a week of earthquakes beneath the volcano and deformation of the lava dome. This eruption sent a steam and small-scale ash feather to almost 10,000 feet to a higher place ocean level. Photo: USGS

It's unlikely that the surface lava flow is being driven by a monster menstruation deep under the volcano, Dzurisin adds. "If there was a large body of magma pressurizing it," says Dzurisin, "information technology would definitely cause ground move on the outer flank, only we are non seeing that."

The mountain's shape is also reassuring, courtesy of the 1980 eruption, Dzurisin adds. "In that location has been a change in the edifice itself. Information technology was decapitated, so there is no potential for a large landslide, or the large, lateral, directed eruption. That's off the tabular array."

How practise volcanoes bear upon the mural?

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