Sunday, May 22, 2005
Mount St.Helen's last volcano eruption still provides surprises
It obliterated nearly everything in its path for 8 miles, sandblasting old-growth forests down to bedrock. As far as 19 miles from volcano, large evergreens were mowed down like grass. The lateral blast was followed by a vertical explosion of ash, enough to cover a football field-sized mound 150 miles high. The ash fell in measurable amounts in 11 states and soon circled the earth.
Finally, mudflows overwhelmed local rivers, bullying their way down to the Columbia, where for weeks they blocked shipping lanes.It was the most destructive eruption in U.S. history and it killed 57 people - incinerating a few, mummifying some, crushing, drowning or asphyxiating the rest. With the exception of one volcano scientist, a few loggers and Harry Truman, an octogenarian innkeeper who refused to leave the mountain, most of those who died had no compelling reason to be near the mountain.
They died as volcano tourists.The summit of Mount St. Helens is now 1,314 feet lower than it was on the morning of May 18, 1980. In many ways, though, the mountain's stature has soared during the past quarter century. It has become an icon of volcanic vulnerability in the Pacific Northwest. And its cataclysmic eruption, which caught many experts off guard, is widely regarded as the defining event in a worldwide push to use better technology to monitor volcanoes.Mount St. Helens is now wired so scientists and public safety officials can respond immediately to signs of trouble.
These instruments have come in handy, as the volcano has awakened in recent months after 18 years of quiescence. It is energetically building itself a new lava dome and periodically belching great plumes of ash.Owing to the big blow in 1980, careful attention is being paid to some of St. Helens' older but still active cousins in the Cascade Range, two of which are near major population centers.
Mudslides from Mount Rainier, which is far larger than St. Helens and much closer to Seattle and Tacoma, are regarded as such a serious threat that volcano evacuation routes have been established and school children near Rainier are regularly drilled in the art of running for high ground.The eruption of Mount St. Helens - filmed and photographed as it occurred - occasioned new insights into how volcanoes work.
The most important lesson learned here, according to scientists at the United States Geological Survey (USGS), is that volcanoes, before they explode, tend to fall apart."The reality that volcanoes fall apart was imprinted on all our brains in 1980," said Seth Moran, a USGS seismologist at the Cascades Volcano Observatory.Researchers have traveled to volcanoes around the world, evaluated the rubble pattern from old eruptions and concluded that Mount St. Helens, by the self-destructive standards of its peers, behaved rather typically.The blast zone has also become an ecological laboratory where researchers have overturned conventional wisdom about how lakes, meadows and forests recover from a catastrophic natural disturbance.
"In 1980, we envisioned the recovery as a linear and predictable process," said Virginia Dale, a plant ecologist who was 28 and finishing graduate work at the University of Washington when the mountain erupted. "Now, that has all been thrown out the window."In a paper published last week in the journal Science and in a forthcoming book, Dale and two other researchers summarize 25 years of recovery on the mountain.
They saw lakes, opaque with ash and choked with debris, turn clear and quickly become nutrient-rich playgrounds for frogs, toads and salamanders, which somehow showed up in the inhospitable blast zone.In the first year after the eruption, as a handful of isolated plants called lupines emerged from avalanche debris, they saw honeybees "in the middle of nowhere, making a beeline to pollinate the plants," said Dale, who works at the Oak Ridge National Laboratory in Tennessee.
They also saw trees behaving in ways that were contrary to botany textbooks.Dale, whose research was paid for by the National Geographic Society, said that western hemlock trees, which typically grow under heavy shade, outraced Douglas fir to sunny spots in the avalanche zone."We thought some plant species would come in and die off, to be replaced by others in an orderly succession," she said. "What we found was everything was happening at once. It was humbling.
"Timber operators, too, have been surprised. The eruption destroyed 68,000 acres of trees on private land owned by the Weyerhaeuser Corp. It also blanketed most of the singed forest with several inches of ash, which is mostly silica and contains none of the organic nutrients needed by conifer trees.Unsure what the ash might do, Weyerhaeuser decided to go ahead and replant, by hand, about 18 million Douglas fir seedling.
Last week, ash was still thick on the forest floor, as Bob Keller, a Weyerhaeuser manager, showed off a thriving crop of trees that is pushing 70 feet in height."We found that ash retained moisture and suppressed weed growth," Keller said. "This stand is taller and the diameter of the trees is greater than outside the blast area. It was a good investment to go back in and replant."For many of the people who survived the eruption, the indelible lesson of Mount St. Helens seems to be that life belongs to the lucky.
On the afternoon before the eruption, Mark Smith, then 20, entered the red zone that officials had established around the volcano. The state had cordoned it off in the early spring of 1980, when the mountain awoke spewing ash and steam. But on the weekend of May 17-18, they allowed local property owners to return and collect belongings.Smith's parents owned a lodge at the base of the volcano - not far from where their longtime friend, Harry Truman, was becoming an international media celebrity for his crotchety refusal to clear off the mountain.
"On Saturday we went back to inventory the lodge and decide what we were going to haul down," said Smith, who remembers noticing the absence of birds and other wildlife on that visit. "The plan was for our family to come back the next day at 10 a.m. and collect our stuff."The following morning, the Smiths were having breakfast at their home about 26 miles southwest of the mountain, when Mark's father strolled out to the porch, saw the sky darken with ash and announced, "It doesn't look like we're going back there today.
"On Mount St. Helens, Truman was already dead and buried under hundreds of feet of rock. Scientists have speculated that prior to the landslide, he felt a cold wind off the mountain and was then incinerated.Mark Smith did not return to the site of his family's lodge for 20 years. When he did, there wasn't much to see.
About 300 feet of rock lies on top of the lodge.Thinking about the eruption, Smith says he does not have any particular insight into why he and his family were spared."We were just very lucky," he said.