:: This last picture was taken the morning of May 18th, 1980 before the eruption.
If you lived in the Pacific Northwest on May 18th, 1980 you will remember this date.
Do you remember where you were when Mt. Saint Helens blew her top?
I was 8 years old playing in our yard waiting for the Fairchild Air Show to start(the planes would fly over our house during the show). I remember it was 2:00 in the afternoon and the sky was as dark as night....really eery feeling. Then, the ash started falling. People didn't know what to think.
Here are some facts about that day:
May 18, 1980 dawned clear and bright. It was an amazingly beautiful day for May in the Pacific Northwest. Being a Sunday, there were only a few loggers, campers and scientists in the area. Many of these people had been lulled into a false sense of security because of the mountain's recent silence. Not even the scientists could predict exactly what was to come.
At 8:32 a.m. a 5.1 magnitude quake struck one mile below the mountain. While there had been literally hundreds of earthquakes at the mountain since March 20th, the unstable north face could not sustain another. Within moments the largest landslide in recorded history removed more than 1,300 feet from the summit and swept away almost the entire north side of the mountain. The elevation of the mountain dropped from 9,677 feet to its present day 8,363 feet. What was once the 9th highest peak in Washington state was suddenly reduced to the 30th highest peak. The intense high pressure/high temperature steam that escaped, instantly turned more than 70% of the snow and glacial ice on the mountain to water. This massive movement of rock, ash, water and downed trees swept into Spirit Lake and down the north fork of the Toutle River Valley at speeds in excess of 175 miles per hour.
Mt. St. Helens is on an ocean-continent subduction boundary (the Juan de Fuca plate is subducting under the N. American plate). Mt. St. Helens is an active strato volcano. The easiest answer to what caused the eruption is that a body of magma moved into the shallow part of the volcano between the first earthquakes and minor eruptions in March, and by May 18th had become so pressurized that the north face of the mountain failed and this magma was able to erupt. The slow moving collision of the continental rock of North America and the Oceanic Rock of the Juan de Fuca tectonic plate, which is slowly moving beneath the Pacific Northwest is slowly refueling Mount St. Helens for another eruption. Scientists estimate that there is a large reservoir of magma four miles beneath the crater.