Mount St. Helens or Louwala-Clough is an active stratovolcano(which means its formed by layers of ash and lava) located in Skamania County, Washington, in the Pacific Northwest region of the United States, mount saint Helens is still active and its last eruption was in 2008.
On March 16, 1980, the first sign of activity at Mount St. Helens occurred as a series of small earthquakes occurred, on March 27, after additional earthquakes, the volcano produced its first eruption in over 100 years, huge amount of ask was funneled into the sky, however this initial eruption gave no evidence that a later eruption would occur.
The initial earthquake that was created by the pressure of magma building up underneath mount saint Helens was a 4.2 in the rictor scale, the earthquake was caused by the subductive plate boundary Juan de Fuca plate subducting beneath the North American plate , this caused a benniof zone that would create the magma that was storing under the mountain.
Fore weeks after the initial earthquake and eruption a bulge in the mountain occurred this bulge grew with time and towards the last few days before the eruption and landslide the bulge seemed to breathe, the bulge is magma exploiting a weak spot as it cant find a blowhole.
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This shows how a stratovolcano is formed
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On March 16, 1980, the first sign of activity at Mount St. Helens occurred as a series of small earthquakes occurred, on March 27, after additional earthquakes, the volcano produced its first eruption in over 100 years, huge amount of ask was funneled into the sky, however this initial eruption gave no evidence that a later eruption would occur.
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| www.thinglink.com |
The initial earthquake that was created by the pressure of magma building up underneath mount saint Helens was a 4.2 in the rictor scale, the earthquake was caused by the subductive plate boundary Juan de Fuca plate subducting beneath the North American plate , this caused a benniof zone that would create the magma that was storing under the mountain.
Fore weeks after the initial earthquake and eruption a bulge in the mountain occurred this bulge grew with time and towards the last few days before the eruption and landslide the bulge seemed to breathe, the bulge is magma exploiting a weak spot as it cant find a blowhole.
Suddenly at 8:32 a.m a magnitude 5.1 earthquake directly below the north slope triggered that part of the volcano to slide approximately 10 seconds after the shock The landslide, the largest in recorded history, traveled at 110 to 155 miles per hour, the total amount of rock moved was 1.5 billion tonnes, the surrounding 230 square miles were destroyed and a 17 mile blast zone was produced.
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| The blast released energy equal to 24 Megatons of TNT, one megaton is 1,000,000 tons of chemical explosives the fat boy bomb was 20,000 tons compared to 24,000,000 |
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