Mt. St. Helens - Explosive Lessons

[Snowden]

washingtonpost.com
Explosive Lessons of 25 Years Ago
Eruption of Mount St. Helens Gave Scientists Insight Into How Volcanoes Work


By Blaine Harden
Washington Post Staff Writer
Wednesday, May 18, 2005; A03


MOUNT ST. HELENS NATIONAL VOLCANIC MONUMENT, Wash. -- Twenty-five years ago, the bulging north flank of this mountain fell away in the largest landslide in recorded history. Stripped of its rock-and-ice corset, the volcano was suddenly semi-naked, its seething innards exposed to a fine spring morning.

And then it blew.

In an explosion heard 690 miles away in Canada, an ash-laden, superheated version of hell exited the mountain laterally and rioted northward at hundreds of miles per hour. It obliterated nearly everything in its path for eight miles, sandblasting old-growth forests down to bedrock. As far as 19 miles from the 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-size mound 150 miles high. The ash fell in measurable amounts in 11 states and soon circled 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 the volcano's 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 schoolchildren 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 U.S. Geological Survey, 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 survey 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 watching 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 seedlings. 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 before 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 was not 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.

© 2005 The Washington Post Company

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[Woodmonkey]

I followed all of that because I am only about a 2-1/2 hour drive from Mt St Helens. There was an exciting buildup and the scientists were sure that it was going to erupt, but didn't know the extent of the eruption. At that time, they simply did not have the knowledge that they do now.

They declared the mountain a red zone and put roadblocks up on the major roads into the mountain. However, there was no way for them to completely block that mountain from people determined to sneak in. They made their best guess about where to put the red zone, but smart people stayed further away then that.

I read a recent story of a couple who took their two young children close in and they had a recorder they used that survived the blast. The children are recorded as being excited and asking if it was safe and the parents said yes. They died from inhaling the ash. How horrible for them. What were the parents thinking to take their children up there?

There was a lawsuit that was, thankfully, thrown out, trying to make the state responsible for all the deaths of people who went up there. Weyerhauser settled with some families, which was a shame because, again, there was no way that the company could stop them.

The families just asked the current governor for an apology that the state didn't make the wide zone big enough. I hope she doesn't do that because those people who just had to get close knew there were risks.

[Woodmonkey]

There were people who survived and had to be rescued at great risk. I talked to some of the chopper folks and they told how they had to use panty hose to cover some intake valves (?) on the engines from the ash. They would spot someone and then land. As they got closer the ash was stirred up and they landed completely blind. They were never sure if they were on the edge of trees or ravines and would topple over when they finally touched down. They were also not sure if the engines would be damaged and they would be able to lift off again. That to me took real courage.

When they opened the mountain back up and built some service roads, we went up to see it. It was a completely grey world. The vast majority of trees were leveled and all in the direction of the pyroclastic flow. Those trees that were just by the cliffs that the flows went over were snapped off. Imagine, huge trees with just the tops snapped off.

There were tiny pockets that were covered in snow that the flows went over, but the snow protected them and they survived. Doc can tell for sure, but I always thought they seeded the area and helped it comeback.

It stayed that grim grey for the longest time, but slowly there were patches of green showing as things started to grow up there.