Helens, began to stir. On March 20, 1980, it was shaken by a strong
earthquake. The quake was a sign of movement inside St. Helens. It was
a sign of a waking volcano that might soon erupt again.
Mount St. Helens was built by many eruptions over thousands of
years. In
each eruption hot rock from inside the earth forced its way to
the surface. The
rock was so hot that it was molten, or melted, and it
had gases trapped in it.
The name for such rock is magma. Once the
molten rock reaches the surface
it is called lava. In some eruptions the
magma was fairly liquid. Its gases
escaped gently. Lava flowed out of the
volcano, cooled, and hardened. In other
eruptions the magma was thick
and sticky. Its gases burst out violently,
carrying along sprays of molten
rock. As it blasted into the sky, the rock
cooled and hardened. Some of
it rained down as ash—tiny bits of rock. Some
rained down as pumice— frothy rock puffed up by gases.
Together the lava flows, ash, and pumice built a mountain with a
bowlshaped
crater at its top. St. Helens grew to a height of 9,677 feet, so
high that its peak was often hidden by clouds. Its big neighbors were built
in
the same way. Mount St. Helens is part of the Cascade Range, a chain
of
volcanoes that runs from northern California into British Columbia.
For well over a hundred years the volcano slept. Each spring, as winter
snows melted, its slopes seemed to come alive. Wildflowers bloomed
in
meadows. Bees gathered pollen and nectar. Birds fed, found mates,
and built
nests. Bears lumbered out of their dens. Herds of elk and deer
feasted on
fresh green shoots. Thousands of people came to hike, picnic,
camp, fish,
paint, bird-watch, or just enjoy the scenery. Logging crews
felled tall trees
and planted seedlings.
These people knew that Mount St. Helens was a volcano, but they did
not fear it. To them it was simply a green and pleasant mountain, where
forests of firs stretched up the slopes and streams ran clear and cold.
The mountain did not seem so trustworthy to geologists, scientists who
study the earth. They knew that Mount St. Helens was dangerous. It was
a young volcano and one of the most active in the Cascade Range. In
1975 two geologists finished a study of the volcano's past eruptions. They
predicted that Mount St. Helens would erupt again within 100 years,
perhaps before the year 2000.
The geologists were right. With the earthquake of March 20, 1980,
Mount St. Helens woke from a sleep of 123 years.
