Located in the state of Washington, St. Helens is considered to be the youngest and most active volcano in the Cascade Range. Although only 12th in height among the major Cascade volcanoes, scientists predict a significant increase in size in the future because the mountain is still in its cone building stage. Mount St. Helens stands atop an older volcano which historically, was probably one of the most explosive peaks in the Pacific Northwest. This assumption is evident through the amount of debris that is scattered for miles over the countryside. The oldest recognized products of the ancestral cone are a pumice layer which is dated at 37,600 years and a weathered mudflow deposit dated at approximately 36,000 years (Harris 1980). Evidence of glacial sediments containing fragments of the earlier mountain are dated at approximately 18,000 years and in

Ash fall of up to 8cm in Washington and Idaho caused harmful problems clogged air filters that disabled vehicles and short-circuited electrical transformers, resulting in power outages. Breathing was so difficult in some areas that many had to wear masks. Needless to say much of the wildlife in the surrounding area was destroyed. Few trees and plants survived the eruption. “The volcano blew out a large portion of the mountainside and baked several hundred square kilometers of adjacent countryside to 400600 oC. The result was a lifeless moonscape punctuated by the ash-gray, leafless trunks of thousands of blown-down trees” (Life erupts at Mount St. Helens 1997:400)

The first sign of activity at Mount St. Helens began On March 16, 1980. A series of small earthquakes were detected and on March 27, after hundreds of earthquakes had been detected, steam explosions blasted a crater through the volcano’s summit ice cap. The crater was estimated to have grown about 1,300 feet in diameter within a week (Brantley et al. nd). Two enormous crack systems had also crossed the entire summit area. 10,000 earthquakes had shaken the volcano by May 17, and the north flank had grown outward to form a noticeable bulge. This indicated to geologists that magma had risen high into the volcano. On the morning of May 18, 1980 and earthquake of magnitude 5.1, shook the volcano and within 20 seconds, the volcano’s bulge and summit slid away in the largest landslide in recorded history. The landslide was about 2.5km^3 (Pringle 1990). Powerful explosions were triggered because the landslide depressurized the volcano’s magma system. “Rocks, ash, volcanic ash and steam were blasted upward and outward to the north. This lateral blast of hot material accelerated to at least 300 miles per hour, the slowed as the rocks and ash fell to the ground and spread away from the volcano.” (Brantley et al. nd) The blast cloud is reported to have traveled as far as 17 miles northward from the volcano. An eruptive column was a result of the blast and rose more than 15 miles in about 15 minutes. The destruction continued as magma erupted from the new crater and a second eruption column was formed.

Following the eruption, thousands of people were evacuated, some by helicopter. Emergency responses that included salvaging lives and property were the first priority. Work crews worked for weeks removing tons of ash from roofs, streets, sidewalks and parking lots. The U.S Army Crops of Engineers worked around the clock, deepening the channel of the Columbia River so that

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