The clock stopped with the May 18, 1980, eruption of Mount St. Helens. It was time zero, a clean slate. Life had to start over from scratch.
Scientists began visiting the blast zone within weeks, while the mountain was still occasionally popping off, to take advantage of the natural laboratory. The volcanic heat and blast, unleashing a natural disaster that captured the world's attention, had wiped out plants and animals. An explosion of pumice and a massive avalanche had created an almost sterile environment to challenge the reinvasion of life.After 10 years, the biggest surprise is the speed with which nature healed its self-inflicted wounds. Lakes and streams have cleaned themselves. Insects that fly or drift on the wind have returned. Plants have returned. Bigger animals have walked in. And, incredibly, a few fish survived in ravaged streams, a few gophers in their tunnels.
Here is a 10-year report:
The tan-color flow of pumice had curved around a hillside and stopped, like a suddenly frozen stream of water. Glowing hot when it had rushed from the Mount St. Helens crater, it was now cool. The rocks squeaked underfoot, like snow on a very cold day.
A helicopter sat a few yards away, its rotor whirling. It was the summer of 1980, and there was still a requirement to be able to get out in five minutes, just in case.
This is the Pumice Plain, material that had been blasted out of the mountain. Nothing should have survived the blast, the heat, the millions of tons of shattered mountain covering the landscape.
Suddenly an insect buzzed past. An insect? Here?
"Insects were in there virtually as soon as the dust settled, drifting on the wind," said Rick Sugg, a University of Washington entomologist who has studied recovery in the blast zone. "But the first ones didn't survive."
There were no plants, no shelter, no food. It was the reverse of the textbook situation where a community of plants provides food for vegetation-eating insects, which in turn are eaten by predator insects, which are then gobbled up by bigger insects - all based on plant production.
It provided a rare opportunity for John Edwards, UW professor of zoology, and Sugg to learn which insects would be the first to return, survive and reproduce in a landscape that resembled the moon.
The winner? The ground beetle, an active, black insect a quarter-inch long. Adult beetles could have flown in on the wind. But by 1982 Sugg had found beetle larvae, evidence that the insects had recolonized the area and were reproducing.
The answer to the beetles' early success, as Edwards and Sugg had suspected it would be, was the bounty of insects deposited on the mountain by the wind. Two million spiders, drifting on strands of silken web, fall on each square mile of the mountain each summer day.
The spiders and insects dependent on plant life didn't survive in those early years. But they provided food for the predatory ground beetles.
"The beetles ate everything they could get their little mandibles into," Sugg said. "The rain of insects supported a whole community of predators. Even many biologists don't appreciate the magnitude of insect dispersal by the wind."
The beetles found shelter from the heat and dryness of the summer by crawling under rocks or burrowing into the loose, shifting surface of the Pumice Plain.
As plants slowly returned, spiders and other insects were able to establish themselves. By 1985, Sugg said, there were insect "boom towns" thriving on the plain.
"Recolonization went much as we expected," Sugg said. "But the degree of success in terms of population growth really was a surprise."
The water in Spirit Lake was the color of coffee. It was still warm in the first months after the eruption of Mount St. Helens had blasted hot debris into the lake, sending huge waves sloshing 800 feet up bordering hills.
As the water drained back into the lake, it carried thousands of blown-down trees, which covered the lake almost completely.
Among jumbled snags and boulders on what had been a beach, a breeze brought a shock. The lake stunk.
Jim Sedell, a researcher with Oregon State University and the Forest Service, jumped into Spirit Lake a few weeks after the May 18 eruption.
"That was a big mistake," he recalled. "It was like jumping into a pulp-mill lagoon in terms of both smell and feel. The water temperature was still in the high 70s or low 80s."
Sedell had planned to use an inflatable raft to get water samples, but the raft leaked. Sedell had other lakes to sample, time was short and helicopter time was expensive. So, after eyeing the dark water with gas bubbling up through it, Sedell jumped in.
"We're talking of water that had several million bacteria cells per cubic centimeter," he said. "I was sicker than a dog about 48 hours later - chills and fever. But the microbiologists were delighted with the samples. They never would have jumped in."
The Muddy River, east of Mount St. Helens, was scoured by a massive mudflow after the eruption. The stream bed through Ape Canyon, draining a glacier into the Muddy, rose 12 to 14 feet as it was clogged by mud.
Clearwater Creek, another tributary of the Muddy hit by the blast and a heavy deposit of ash, was so unstable that Sedelldiscovered the whole stream bed was moving downhill.
"And yet brook trout survived in those rivers," Sedell said. "We didn't believe it for a couple of years when the streams still looked like liquid concrete.
"But somehow, somewhere in the system, the fish were hanging on. I think that's what surprised me most."
Beavers in the blast zone didn't survive, but in the years since, Sedell has seen signs that beavers have visited the streams. Not finding the trees they need for food and dam construction, however, they didn't stay. That is changing.
"My guess is that an explosion (in beaver population) is about to start," Sedell said. "We're already seeing it along the South Fork of the Toutle at Harrington Creek, where willows and cottonwoods have been planted. Beavers are just mowing them down and creating ponds.
"There's going to be one big beaver farm in a few years. And if you're a coho salmon or a cutthroat trout, that's very good."
Mounds left when hardy alpine lupine - usually among the first plants to reappear after a disaster - drop their leaves and then die create a patch of organic soil.
Other plants taking hold in the mounds are spreading out. James MacMahon of Utah State University, who calls them "little islands of fertility," has found Douglas fir seedlings 12 inches tall growing in the mounds.
MacMahon found that pocket gophers, which survived May 18 underground in their tunnels, also created mounds on the surface that speeded plant recovery. By tunneling in search of the roots and corms, or fleshy underground stems, that provide their food, the gophers dug through organic soil buried by volcanic ash. The soil deposited on the surface, when mixed with ash, created a mixture as rich as the potting soil used by gardeners, MacMahon said.
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(ADDITIONAL INFORMATION)
Another blast coming?
Ten years after its massive eruption, there is a 50-50 chance Mount St. Helens will explode its dome again within three decades, a University of Washington seismologist says.
Steve Malone, a geophysics professor, said that Mount St. Helens is the most likely volcano in the Cascade Mountains to erupt in the next 20 to 30 years.
He said seismic activity, on which the predication is largely based, is a good barometer because it indicates the breaking of rock below the Earth's surface as molten material rises underneath the volcano. The probability of eruption increases with the frequency and magnitude of the earthquakes, he said.