Mt St Helens Eruption 1980 Facts

Mount St. Helens erupted at 8:32 a.m. PST on May 18, 1980, reminding Pacific Northwest residents and people around the world of the powerful and uncontrollable forces of nature. Physical effects of the eruption were experienced in dozens of U.S. states, with ash falling as far away as Oklahoma. Visit Mount St. Helens yourself to learn more about the volcano’s history and current condition.

The first sign of activity at Mount St. Helens in the spring of 1980 was a series of small earthquakes that began on March 16. After hundreds of additional earthquakes, steam explosions on March 27 blasted a crater through the volcano’s summit ice cap. Within a week the crater had grown to about 1,300 feet in diameter and two giant crack systems crossed the entire summit area. By May 17, more than 10,000 earthquakes had shaken the volcano and the north flank had grown outward at least 450 feet to form a noticeable bulge. Such dramatic deformation of the volcano was strong evidence that molten rock (magma) had risen high into the volcano.

During the eruption a great portion of the rock facing on north side of the mountain fell, followed by a lateral blast of stone, ash, and poisonous gas that carried debris 17 mi (27 km) and flattened and buried surrounding forest. The disaster took some 65 lives, wiped out substantial populations of elk, deer, bear, and coyote, and destroyed 230 sq mi (600 sq km) of vegetation.

The facts and effects of the Mt St Helens eruption included:

* Mount St. Helens was reduced by over 1,300 feet in height
* Ash fell as far as 930 miles away
* The debris avalanche and mudflows buried the Toutle valley to a depth of almost 50 meters
* The eruption lasted for 9 hours
* 57 people lost their lives, or are still considered missing
* 250 square miles of land was damaged
* “Countless” animals were killed - estimates are 7,000 big game animals and millions of birds, fish, and small mammals
* Minor eruptions continued into 1986