Mount St. Helen Essays - Geology, Plate Tectonics, Volcanology

Mount St. Helen Mount St. Helen is a volcano located along the Cascade range which is a volcano chain stretching from Northern California to British Colombia. It now stands at a height of 8,364 feet above sea level. Mount St. Helen was on of the smaller eruptions of five major ones in Washington 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 years of inactivity a earthquake under the volcano quaked, and seven days later a pheartic (steam) explosions began. As magma pushed up from beneath the earth's surface, the north side of the mountain developed a bulge. Angle and slope-distance measurements indicating that the bulge was growing at a rate of 1.5 feet per day (Lyn Topinka Page 2). By May 17 the volcano's north-side had been pushed upward and outward 450 feet (Lynn Topinka Page 2). On May 18,1980 at 8:32 a.m. Pacific daylight time a magnitude 5.1 earthquake shook Mount St. Helen. The bulge on the North side of the mountain gave way in a gigantic rock slide releasing pressure and triggering a major rock and pumice eruption . At thirteen hundred feet the peak collapsed and as a result 24 square miles of the valley was filled with rock and debris. From that rock slide 250 square miles of timber, recreation and private lands were demolished from the lateral blast. For more than nine hours the volcano spit vigorous ash in a large plume. Eventually the plume reached 12-15 miles above sea level. The plume went eastward at about sixty miles per hour. By noon the plume of ash had reached as far as Idaho. By the 19 the eruption was over. Now the volcanoes elevation is only 8,364 feet above sea level before the eruption it was 9,677 feet above sea level knock off a whopping 1,313 feet off of the top of the mountain. Now it has a mile wide horseshoe shaped crater on the northern side of the mountain. From the eruption noticeable ash fell in eleven states. The total amount of ash that fell was .26 cubic miles or enough ash to cover a football field to a depth of 150 miles(Lyn Topinka Page3). From the landslide 2/3 cubic miles of debris was deposited in the valley that enough to cover Washington DC fourteen feet thick.(Lynn Topinka, Page 4) Mount St. Helen is said to have caused the most damage (Mattox Page 1) a total 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 to agriculture, timber, roads, bridges, fisheries, houses, sewer treatment plants, and the 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 that 100,000 acres include 41,000 acres of national forest,(Scooner Page1) also over four billion feet of usable timber became unusable that's enough lumber to build 150,000 homes.(Topinka Page3) Nearly 135 miles of river channels were effected by the volcano and more than 185 miles of roads and over 200 homes were destroyed. (Topinka Page 5) Now over 9.5 million tree seedlings have been planted to replace the ones destroyed by the blast and of those 70 percent of those have survived(Scooner Page 1)some already growing twenty feet high(ScoonerPage1). The fish and wildlife have received considerable attention since the eruption. The heavily hunted Elk have shown that the restrictions after the eruption have helped the repopulating 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 years since the eruption. (Sconner Page 1) Now the United States Geological Survey has established both a continuos twenty-four hour and periodic monitoring programs to study and predict future eruptions Mount St. Helen. (Lyn Topinka). They also setup a seismic station near the dome of the mountain. The University of Washington State in conjunction with the US Geological Survey now monitor it.