Mount St. Helen

September 22, 2018 General Studies

Mount St. Helen is a volcano located along the Cascade range which is avolcano chain stretching from Northern California to British Colombia. It nowstands at a height of 8,364 feet above sea level.

Mount St. Helen was on of the smaller eruptions of five major ones inWashington State. It’s elevation before the eruption was 9,677 feet high.

On March 29, 1980 after a period of one-hundred and twenty-three yearsof inactivity a earthquake under the volcano quaked, and seven days later apheartic (steam) explosions began.

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As magma pushed up from beneath the earth’s surface, the north side ofthe mountain developed a bulge. Angle and slope-distance measurementsindicating that the bulge was growing at a rate of 1.5 feet per day (Lyn TopinkaPage 2). By May 17 the volcano’s north-side had been pushed upward andoutward 450 feet (Lynn Topinka Page 2).

On May 18,1980 at 8:32 a.m. Pacific daylight time a magnitude 5.1earthquake shook Mount St. Helen. The bulge on the North side of the mountaingave way in a gigantic rock slide releasing pressure and triggering a major rockand pumice eruption . At thirteen hundred feet the peak collapsed and as a result24 square miles of the valley was filled with rock and debris. From that rock slide250 square miles of timber, recreation and private lands were demolished from thelateral blast. For more than nine hours the volcano spit vigorous ash in a largeplume. Eventually the plume reached 12-15 miles above sea level. The plumewent eastward at about sixty miles per hour. By noon the plume of ash hadreached as far as Idaho.

By the 19 the eruption was over. Now the volcanoes elevation is only 8,364 feetabove sea level before the eruption it was 9,677 feet above sea level knock off awhopping 1,313 feet off of the top of the mountain. Now it has a mile widehorseshoe shaped crater on the northern side of the mountain.

From the eruption noticeable ash fell in eleven states. The total amount ofash that fell was .26 cubic miles or enough ash to cover a football field to a depthof 150 miles(Lyn Topinka Page3). From the landslide 2/3 cubic miles of debriswas deposited in the valley that enough to cover Washington DC fourteen feetthick.(Lynn Topinka, Page 4)Mount St. Helen is said to have caused the most damage (Mattox Page 1) atotal of 1.6 billion dollars of damage was caused by the blast from the volcano. That figure comes from losses due to home and road cleanup, damage toagriculture, timber, roads, bridges, fisheries, houses, sewer treatment plants, andthe dredging of rivers.(MattoxPage1). 57 people were killed or still missing(Topinka Page1) More than 100,000 acres of were demolished by the blast of that100,000 acres include 41,000 acres of national forest,(Scooner Page1) also overfour billion feet of usable timber became unusable that’s enough lumber to build150,000 homes.(Topinka Page3) Nearly 135 miles of river channels were effectedby the volcano and more than 185 miles of roads and over 200 homes weredestroyed. (Topinka Page 5)Now over 9.5 million tree seedlings have been planted to replace the onesdestroyed by the blast and of those 70 percent of those have survived(ScoonerPage 1)some already growing twenty feet high(ScoonerPage1). The fish andwildlife have received considerable attention since the eruption. The heavilyhunted Elk have shown that the restrictions after the eruption have helped therepopulating of them returning to the pre-eruption population within five years. Also the Samon and trout have returned to there population since the eruption. Stream temperatures have exceeded there legal threshold population in most yearssince the eruption. (Sconner Page 1)Now the United States Geological Survey has established both a continuostwenty-four hour and periodic monitoring programs to study and predict futureeruptions Mount St. Helen. (Lyn Topinka). They also setup a seismic station nearthe dome of the mountain. The University of Washington State in conjunctionwith the US Geological Survey now monitor it.


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