Science: Decoding the Volcano's Message

At Mount St. Helens: T shirts, bumper crops and suspense

It is the hottest show out of the West, competing with Disneyland and the tinsel of Hollywood. Visitors are flocking to it by the thousands. For sheer suspense it rivals even Hitchcock, continually hinting of ominous new surprises. The sulfurous center of all this attention is Mount St. Helens, site of the largest volcanic explosion in the U.S. in more than 60 years.

When the volcano erupted last May 18 with the force of 500 Hiroshima-size atomic bombs, it blew away a cubic mile of earth, killed at least 31 people (another 32 are missing and presumed dead), destroyed or damaged 220,000 acres of timberland and created a monumental dredging job on three nearby rivers. In the four months since then, the mountain has been restive but not cataclysmic. There have been four major eruptions and numerous smaller ones, the most recent on Aug. 15. But Mount St. Helens lets no one rest, especially scientists.

Last week harried U.S. Geological Survey workers noticed a quirky change in the volcano's gaseous emissions. Abruptly, the 5-to-1 ratio of carbon dioxide to sulfur dioxide dropped sharply to 2.4 to 1. Similar drops preceded at least two of the post-May 18 eruptions. That raised immediate concern that the volcano was about to blow again. But the ratio is no certain predictor. Says Geologist Bob Noble: "We don't have anything that's 100% accurate."

Tiltmeters on the mountain's north rim were showing a slight but growing deformation similar—but on a much smaller scale—to the bulge on the peak's north face before the May explosion. Scientists were not sure if it was caused by a swelling on the rim or the settling of material on the floor of the crater. Inside the crater a lava dome has been forming. It glows red as molten rock roils underneath its hardened crust. The questions: Will it be able to cap the volcano? Or will pent-up gases blast through again?

Almost anywhere in the , wedge-shaped 400-km² (150 sq. mi.) blast zone stretching north of the mountain, all appears to be devastated, a sea of gray volcanic ash. Geologists and biologists believe it will be decades before life comes back to the mountain's highest slopes. Yet lower down, in what looks like a totally forbidding, colorless world, life, incredibly, is returning. Deer tracks have been spotted on otherwise barren slopes; new growths of ferns and skunk cabbage are poking through the ash. Tree sprouts are "coming up beautifully," says John Allen, 72, geology professor emeritus at Portland State University.