GEOLOGY 170 REPORT:


MT. ST. HELENS:


Mount St. Helens is located in southwestern Washington about 50 miles northeast of Portland, Oregon. Mount St. Helen is one of several volcanic peaks that dominate the Cascade Range in the Pacific Northwest. The principal part of the range extends from Mount Garibaldi in British Columbia, Canada, to Lassen Peak in northern California. It was considered one of most beautiful mountains in the Cascade Mountain Range. St. Helens was often compared to Mount Fuji in Japan because of the mountain's similarity in appearance. All of that would change on May 18, 1980 when the young and quiet Mt. St. Helens decided to become an active volcano and cause the worst natural disaster in the history of the U.S.
The eruption was triggered by a massive mudslide on the side of the mountain. All the material that slid away from the mountain caused a lateral blast that could be heard hundreds of miles away. The lateral blast only lasted a few minutes of a nine-hour eruption. After the mountain was forced open by the lateral blast the mountain erupted in full force. Mt. St. Helens ejected a cloud of ash 15 miles into the air. The ash being ejected into the atmosphere blanketed virtually the entire Northwest a blanket of ash. Towns as far away as Spokane Washington were covered in the choking ash. Day turned into night as the mountain erupted. Roads and highways at a stand still. Mt. St. Helens was creating it's own weather systems. 150 square miles of forest and recreation area were destroyed in minutes. Hot pyroclastic clouds of ash burnt everything in sight. Trees knocked down because of the massive blast the mountain released. Mudflows wiped out entire river systems and lakes in the Mt. St. Helen area. The Columbia River, which borders the states of Oregon and Washington, was affected by mudflows. The giant river is about 70 river miles from St. Helens. The shipping canal was blocked because of the mudflows and needed to be dredged for passage. That May 18 day will be remembered forever because of the power that Mother Nature displayed.
As soon as the mountain erupted the National Guard was called in to try and find survivors. As soon as it was possible and clear enough to fly into the blast zone choppers were sent to see the damage that has been done. The terrain, which at one time was green, was now gray and burnt. The smell of sulfur was in the air. A total of 60 people were dead or missing after the eruption. There was a large rescue effort that saved many lives but many lives were lost instantly. Scientist knew that the eruption was probably going to come because of earthquakes on and around St. Helens. But the large mudslide sped up the process dramatically. After all was said and done to Mt. St. Helens lost roughly one cubic mile of material from its summit. The mountain lost 1,300 feet of its crown during the eruption. The once cone shaped mountain now resembled a horseshoe. The eruption made all of the newspapers in the world. In that time Mt. St. Helens was the center of the worlds attention.
Twenty years after the eruption of Mt. St. Helens the question that most people ask is whether or not this kind of catastrophe will happen again in the future. The study of volcanoes has come leaps and bounds since 1980. Trying to predict when and where an eruption may occur is much more affective now. Mt. St. Helens has roughly nine eruptions in the past 50,000 years. That's not counting the activity in 1980. The most recent and best known of the pre-1980 eruptive periods began with a major explosive eruption in 1800 AD. For the next 57 years, intermittent relatively small explosive eruptions, lava flows, and the extrusion of lava dome followed this event. Assuming that Mount St. Helens behaves as it did in the 19th century, the present activity could continue intermittently for years, possibly decades. Such activity could include the outpouring of lava flows (not observed to date), as well as some dome growth and small explosive activity. The chance of another catastrophic landslide and blast comparable to
The eruption of May 18, 1980 is pretty low. The