what were the effects?
57 people known to have died in that day's eruption succumbed to asphyxiation, while several died from burns
1980 eruption of Mount St. Helens
By the time this pyroclastic flow hit its first human victims, it was still as hot as and filled with suffocating gas and flying debris. Most of the 57 people known to have died in that day's eruption succumbed to asphyxiation, while several died from burns. Lodge owner Harry R. Truman was buried under hundreds of feet of avalanche material. 
what happened after the mt st helens eruption An earthquake which caused the entire weakened north face to slide away, creating the largest landslide recorded when was the last time it erupted? January 2008 and before that? October 2004 and before that? Between 1980s to 1991 which was the deadliest eruption? March 27, 1980 eruptions describe the build up of this eruption that you just mentioned On March 20, at 3:45 p.m. Pacific Standard Time, a shallow magnitude 4.2 earthquake centered below the volcano's north flank, signaled the volcano's return from 123 years of hibernation. A gradually building earthquake swarm saturated area seismographs and started to climax at about noon on March 25, reaching peak levels in the next two days, including an earthquake registering 5.1 on the Richter scale. A total of 174 shocks of magnitude 2.6 or greater were recorded during those two days how far did the landslide reach? He traveled and moved across Spirit Lake's west arm, part of it hit a ridge about north, some of the slide spilled over the ridge, but most of it moved down the North Fork Toutle River, filling its valley up to deep with avalanche debris were there mudslides as well? Yes, mudflows from the southern and eastern flanks had the consistency of wet concrete as they raced down Muddy River, Pine Creek and Smith Creek to their confluence at the Lewis River is it true there were side way blasts? Yes
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1980 eruption of Mount St. Helens [SEP] Lateral blast result
The huge ensuing ash cloud sent skyward from St. Helens' northern foot was visible throughout the quiet zone. The near-supersonic lateral blast, loaded with volcanic debris, caused devastation as far as from the volcano. The area affected by the blast can be subdivided into three roughly concentric zones: By the time this pyroclastic flow hit its first human victims, it was still as hot as and filled with suffocating gas and flying debris. Most of the 57 people known to have died in that day's eruption succumbed to asphyxiation, while several died from burns. Lodge owner Harry R. Truman was buried under hundreds of feet of avalanche material.