Helen's, located in the Cascade Mountains, about 95 miles south of Seattle has been an active volcano for more than 4,000 years. It is considered a very young volcano. Over the last 4,000 years, the mountain has erupted regularly every few hundred years and the top that was destroyed in 1980, was less than 500 years old. .
The 123 years before 1980 were very quiet for Mount St. Helens even though it was still classified as an active volcano. In the 1800s, a few small eruptions took place but nothing as big as the 1980 eruption. After 1857, the mountain was very quiet and was considered dormant until the fatal blast. It became a popular vacation spot for many people, especially Spirit Lake at the base of the mountain.
Geologists were worried about Mount St. Helens before it exploded. In 1978, Dwight Crandell and Donal Mullineaux of the U.S. Geological Survey (USGS) looked at the amount and type of volcanic debris found at Mount St. Helens. Based on their research, they predicted that the mountain could erupt before the year 2000. .
On March 27, 1980 at 12:30 p.m., Mount St. Helens woke up from its long nap. The summit of the mountain exploded releasing steam and ash into the air. A crater was created in the glacial ice cap that had kept the lid on the mountain for many years. On March 29, 1980, a second crater was formed and by April 7, the craters merged forming one large crater more than 1,700 feet across and 500 feet deep.
Seismologists on April 3, 1980 at the University of Washington recorded a tremor that caused them great concern. The tremor showed that there was an underground movement of magma or gases. The governor of Washington declared a state of emergency that day and recommended people evacuate the area.
From mid-April to May 17, 1980, there were a few eruptions but the seismologists were still recoding high readings of activity beneath the mountain. They were still worried.