Washington St. Helens
July 10, 1998
When driving north into Washington state on Interstate Five, a symmetrical, snow-covered, mountain could be seen on a clear day. Then one day in March 1980, the north side and about 1,300 feet of the top of the mountain slid off into the valley below. It was one of the greatest landslides ever recorded. Scientists warned that something big was likely to happen because their seismometers were recording repeated earthquakes and there had been several smaller eruptions from the cone of the volcano. But they were not prepared for the events following the landslide. Superheated gasses that had built up in the bowels of the mountain were suddenly released by the landslide and exploded across the landscape. Winds, estimated at up to 700 mph, blasted into the forest, picking up mature Sitka spruce and Douglas firs, as well as lots of rocks, and slamming them against their neighbors. From the north side of the volcano, the forest was leveled -- except in protected spots behind hills -- over a 230 square mile area. Most plant and animal life was killed quickly. The explosion outran the landslide, but the landslide followed, burying forests and lakes under several hundred feet of the old mountainside. A vertical column of ash rose 17 miles into the sky -- turning day into night for some towns in eastern Washington. The heat generated by this volcanic activity melted the snow and ice that were on the volcano. This release of water mixed with landslide material formed mud which washed down the Toutle River, carrying and grinding up homes, bridges, automobiles, and humans. To understand the immensity and intensity of this whole process requires a visit. I was profoundly impressed!
The story of this Mt. St. Helens volcanic activity and the photos took of it, filled the world news networks for weeks after the event. Many of us saw photos of the billowing clouds, the destruction of the forest and the human suffering and bravery that followed. So what was so unusual about this event? Expert volcanologists thought that volcanos vented at the top, releasing magma that build the nice symmetrical cones of volcanic mountains. But Mt. St. Helens did not behave as expected. It blew out horizontally so that it was more destructive to the forest that might be expected. Fundamentally, it changed the landscape dramatically in just a matter of minutes. Most of us have been conditioned in the classroom to accept the slow, evolutionary-like changes in the landscape. You know, like the slow build-up of land masses by the subduction of the Juan de Fuca plate, at a rate of maybe 1-4 cm per year, under the North American Plate, or the slow evolution of new species of plants and animals. We thought of stable ecosystems that endure for long periods of time and change slowly.
Mt. St. Helens also surprised many biologists. The process of ecological succession describes the orderly establishment and successive replacement of one group of plants by another after some kind of disturbance to the landscape. According to theory, a few seeds of plants should recolonize the outer edges of this scoured landscape, followed by the animals that eat the plants, and then another group of plants. Succession is taking place much more rapidly than expected. Small pockets of life representing later successional stages survived the blast in protected places. Plants in these pockets grow and form small, living islands that expand as they reproduce. Some animals that lived underground such as ants and pocket gophers survived the blast. About 68,000 acres of forest lands outside the Mount Saint Helens National Volcanic Monument, owned by the Weyerhaeuser Corporation, were quickly replanted. Some of the replanted trees are now 35 to 45 feet tall. The Toutle Riverbed, that was filled with rocks and debris, was seeded with clover and grass and fertilized. Elk numbers increased very rapidly. In the Toutle Valley, far below the Weyerhaeuser Visitor Center, I counted more than 100 elk from one viewpoint. These elk rapidly colonized the blasted area. Their hooves broke through the top layer of ash that had fallen from the volcano allowing the roots of seeds (carried in the digestive tracts of the elk) to take root in the soil below the ash. Forecasts of forest recovery are now much more optimistic than first estimated.
Volcanologists have learned from the experience. Models that forecast these cataclysmic events remain imperfect. Experts asked when Mt. St. Helens will erupt again, answer that it could happen tomorrow, but it is more likely to take place in about 60 years. Currently, there is a build-up in the frequency of earthquakes (11 small ones on July 8, 1998) which suggests some increase in volcanic activity. The lava deposits in the crater of the mountain continue to grow and steam can be seen venting from several places on the growing lava dome. The “fingerprints” that volcanologists use for prediction -- such as earthquake frequency and intensity, harmonic rumblings of magma, changes in elevations of the dome, carbon dioxide concentrations and other such stuff -- do not forecast an eruption soon. Experts expect that the volcano will enter a long period of semi-dormancy before it erupts again. But nobody really knows.
On a clear day, the relatively new Johnston Ridge Observatory provides an exceptional view of the mountain, the crater, lava dome, pumice plain and devastation caused by the eruption. The visitor’s center at Johnston Ridge also provides a clear analysis of what the experts think happened. A movie showed a film taken by a photographer -- who probably did not know how brave he was to be standing in the face of such a large explosion. After the film of the blast and associated activities, the movie screen was raised to show the magnificent, snow-clad mountain in the background through a large glass window. The audience reaction was “Wow!”
In my mind, exposure to the information generated by this volcano reinforces the notion that we live on these fragile, continental islands of land, that float around the planet on an ocean of molten rock. When old Alfred Wegener first postulated the theory of continental drift in the early 1900's, his idea was rejected almost universally by the scientific community. When I went to school, his theory was still subject to considerable skepticism. Evidence continues to accumulate to support his theory. But this skepticism is as it should be because most new and old ideas are wrong or incomplete. The acceptance of ideas, especially new ideas, must be accompanied by exceptional supporting evidence. Mt. St. Helens has added a little more evidence to the idea of continental drift. Ain’t it fun!
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