The History of Mount Saint Helens Volcano
by Krysta CardinaleMount Saint Helens is an active volcano on the Pacific coast of North America, and it is part of the Cascade Mountain Range. The volcano is known for its ash explosions and lava flows. The Mt. St. Helen eruption on May 18, 1980 made it famous. It is still the deadliest and most economically devastating volcanic disaster in United States history.
Location of Mt. St. Helens Volcano
Mount Saint Helens is located in Skamania County, Washington, in the United States. It is about 96 miles south of Seattle, and about 53 miles northeast of Portland, Oregon. This volcano is part of the Pacific Ring of Fire that has over 160 active volcanic members. The Cascade Range that includes the location of Mt. St. Helens is home to a number of volcanoes. Most of these are made up of lava rock with layers of pumice stone, ash, and other deposits. Helens also includes several layers of andesite and basalt.
This volcano is about 34 miles west of the eastern portion of the Cascade Range including the volcanic Mount Adams. These two mountains are often called “sister and brother.” They are both about 50 miles from the giant Cascade volcano, Mount Rainier. The closes major volcanic mountain in Oregon is Mount Hood, which is 60 miles southeast of Mount St. Helens. The closest community to the mountain is Cougar, Washington. It’s located in the Lewis River Valley and is approximately 11 miles from Helens’ peak.
Helens is typically considered a young volcano since it only developed 40,000 years ago. In the last 10,000 years it is also the most active volcano of the Cascade Range.
The Mt. St. Helens Eruption of 1980
On May the 18th, 1980, there was an explosion five hundred times as powerful as the atomic blast at Hiroshima. It blew away three quarters of a cubic mile of rock, and the forests around the mountain were totally destroyed. Trees two hundred feet tall lay scattered like matchsticks. Weeks beforehand, Geologists watched a huge bulge develop on the side of the mountain, and had warned of the coming catastrophe.
The 1980 Mt. St. Helens eruption reached a magnitude of a 5.1 earthquake that caused the north face of the mountain to collapse. This is the largest avalanche of debris in recorded history. The eruption reached a five on the “Volcanic Exclusivity Index scale” as it destroyed over 320 square miles of land.
The total eruption lasted over nine hours, and less severe outbursts lasted for several days afterwards. On the northern side of the volcano, there were not even trees to be seen. A huge avalanche of rock blown out by the blast had slid for 15 miles down the side of the mountain and buried everything. Behind it, Mount Saint Helens lay wrecked. Its summit was over 1,000 feet lower, and at the back of the huge amphitheater a mile wide crater stood. Over 60 people stayed and were killed during the eruption.
Mt. St. Helens After Effects
The remainder of volcanic ash in the area presents different problems. The difficulty here is not the glassy hardness of the rock, but quite the reverse, its dustiness. Mount Saint Helens was still a wasteland after some two and a quarter years since the volcano erupted. Three miles from the crater, the scene was still one of devastation and sterility. It's not just the fact that the volcanic ash is not very fertile, but it's also that it’s so loose that it’s difficult for plants to get root. But the possibility of life still remained. For example, in some crevices there were the seeds of the willow herb, or fireweed, that had been blown up from the valleys below.
Other Mt. St. Helens’ after effects included seismic and volcanic activity until 1986, as a new lava dome was being formed in the crater. Then from 1989 to 1991 there were more seismic activities and small explosions from the mountain. There were recorded “earthquake swarms” below the Helen’s crater in 1995, 1998, and again in 2001. However, none of these produced any sort of explosive activity.
Since the fall of 2004, Mount St. Helens has become active. It was given the distinction of “active” from recording of thousands of localized earthquakes in the area, and also steam and ash coming from the crater. On October 11, 2004 magma actually reached the surface of the volcano and a new lava dome formed in addition to the already existing one. This “new” dome continued to expand into 2006. The only real significant action in 2005 was on March 8th. The Mt. St. Helens volcano released a 36,000 foot tall emission of steam and ash. Yakima, Washington received a shower of ash. This was not considered an eruption or volcanic explosion, but instead just a release of pressure. Due to this recent activity, geologists warn of another Mt. St. Helens eruption, however they do not feel it will be as severe as the one in 1980.
