In March 1980, Mount St. Helens,
a dormant volcano in the Pacific Northwest, stirred
to life. Increasing numbers of earthquakes under the
volcano and steam explosions near the summit indicated
that this beautiful, symmetrical mountain was getting
ready to erupt.
As the signals of an eruption became
obvious, officials had to consider which locations around
the volcano might be in danger from lava, ash, and mudflows.
They needed to define an evacuation area and move all
the people within that area to a safe distance from