Helens heads the
volcano watch list in North America. It is the most active volcano
in the Northwest, and one of the most closely monitored volcanoes
in the world. "It's the volcano most likely to explode," says
Bill Steele, director of the Seismic Monitoring Program at the
University of Washington in Seattle.
keeps tabs on the volcano through 11 seismographs, which are
planted around the mountain's base and at the rim of the crater.
These extremely sensitive instruments are connected to radio
transmitters that send back a record of every "pop and gurgle"
inside the volcano. Typically, they record a few small tremors
Generally, scientists believe these tremors are
produced by magma
cooling several kilometers beneath the surface of the volcano.
As magma cools, it settles and releases various gases, which
escape upwards through the rock. These tremors, however, might
also be a warning that magma is rising towards the surface.
"We might have only a few months of warnings when the magma
starts moving back into the mountain," says Steele. "I would
not be surprised if we had another eruption in the next ten
Geologists had little warning before Mount Saint
Helens's last major eruption. A small earthquake was recorded
on March 20, 1980, followed a week later by a minor eruption.
But the ground continued to tremble, and six weeks later, on
Sunday, May 18, 1980, the mountain exploded in one of the most
spectacular eruptions in recent memory.
200 mile-an-hour blast flattened trees 20 miles away, killed
57 people, and sheared 1,300 feet off the peak of the mountain,
leaving a crater more than a mile wide. The north side of the
volcano burst, letting lose a side-long flare of magma and burning
gas that incinerated the surrounding region. One hundred and
fifty square miles of prime old-growth forests were reduced
to a wasteland of scorched timber buried under a thick layer
of volcanic ash, where fires burned for weeks afterwards.
The blast also triggered the largest landslide in recorded history,
sending ash and rocks, some the size of large buildings, tumbling
across a 14 mile swatch of land. The landslide also spilled
into Spirit Lake, sending millions of gallons of water surging
down the mountain. This water picked up debris and created a
mudflow, known as a lahar,
which rushed down the mountain, wiping away bridges and roads.
The lahar poured down Toutle Valley, jamming rivers, destroying
homes, and blocking navigation as far away as the Columbia River.
The eruption also sent more than 540 million tons of volcanic
ash raining down over 22,000 square miles, covering Montana,
South Dakota, and Nebraska, and sending ash drifting as far
away as Virginia. From space, the eruption initially took the
shape of a giant mushroom cloud, signifying a blast 400 times
more powerful than the atomic bomb that leveled Hiroshima.
Rebirth is the legacy of natural destruction,
and life quickly returned to the scorched earth near Mount Saint
Helens. The rapid regeneration surprised most scientists, who
believed that the rebirth would occur in steady, regular stages.
Instead, nature ran riot, led by dozens of organisms that had
amazingly survived the devastation. Moles, tiny pocket gophers,
and ants survived because they were buried when the explosion
occured. And saplings and shurbs buried in the snow survived,
while the taller trees were devastated.
The tiny pocket gophers turned into a major force for renewal.
Their habitual digging into the soil mixed the sterile volcanic
ash with the rich earth buried below. Deer mice, ants, and beetles
also assisted in turning over the soil, allowing new plants,
shrubs, and trees to take root quickly. Algae, plankton, and
various freshwater crustaceans quickly appeared to recolonize
the ash poisoned lakes in the area, followed soon after by frogs
large animals quickly returned. Elk were seen on the mountain's
west slopes within weeks of the eruption, and by the following
summer, the hills near the volcano were covered with fireweed,
a pink flowering plant whose seeds are carried like little parachutes
on the wind. Grasses, plants, and trees quickly took root in
the sterile ash, and after three years, the plant composition
in the blast zone was similar to adjacent lands that had been
The federal government moves more slowly than mother nature,
but some 110,000 acres around the volcano were set aside in
1992 and turned into a park called the Mount Saint Helens National
Volcanic Monument. A law was also passed that allowed nature
to follow its own course in the park, permitting scientists
to continue studying the cycles of natural regeneration.
The eruption has also generated an unexpected economic rebirth
in the region. Mountain climbing to the summit of the volcano
has been allowed since 1986. By the end of 1989, the park had
hosted more than 1.5 million visitors. Today, the volcano continues
to draw more than 600,000 visitors a year, and tourism has become
a major economic engine for the region.
The last two decades have also witnessed 30 more small eruptions
on the mountain, and molten rock continued to surface as late
as 1986. Between 1980 and 1986, Mount Saint Helens built a lava
dome about 1,000 feet high and 3,500 feet in diameter. The last
significant eruption was in 1994.
-- By Micah Fink