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.