Mount St HelensMount St HelensLocation, Cause And Date Of EruptionOn May 18th 1980 at 0833 Mount St Helens (Cascade mountain range, Washington, USA) erupted following a period of activity which began in March 1980. Mount St. Helens is located in the Northern Hemisphere in the continent of North America. It is in the mountain range the Rockies. It is located on a destructive plate boundary. The Juan de Fuca plate (oceanic crust) moves eastwards towards the North American Plate (continental crust), and is forced downwards. This movement creates friction which produces earthquakes and due to an increase in temperature destroys the oceanic crust.
(The Plate Boundaries)It triggered an earthquake measuring 5.2 on the Richter scale and the north face of the mountain collapsed in a massive landslide which is the largest landslide ever recorded. The landslide was 200 meters thick in the upper Toutle valleys. At the same time, a giant cloud of ash rose 15 miles (24km) into the sky in just 15 minutes. Then hot ash, pumice and gas known as pyroclastic flows poured out of the crater. The heat melted the snow, which created mudflows in all the major river valleys. When it erupted, it permanently changed the surrounding landscape. Westerly winds bowed millions of tons of ash across the United States turning blue skies grey as far as Spokane, Washington – 250 miles (400km) away.
Before The EruptionBefore Mount St .Helens erupted the volcano went through 3 months of seismic activity as magma rose within the mountain. As the magma rose, a large bulge grew on the north flank of the volcano. This was due to a blockage in the main vent resulting in the growth of a crypto dome (mound of viscous lava) in the side of the volcano. There was also an earthquake in March measuring 4.0 on the Richter scale. US Geological survey team monitored at different camps called Coldwater 1, Coldwater 2 and Swift creek and the most expensive equipment was used. On the 28th March 14 residents had to be evacuated from their homes because of how close they were to the volcano. Harry Truman an elderly local resident refused to leave his home because he believed Mount St. Helens was apart of him because he grew up there, he later died in the blast. Also on the 28th march police closed up roads and 2 days later Red Zones were set up 3-8 miles from the volcanoes summit. 5 mile exclusion was then set up around the volcano. People were also warned via television broadcasts from 3rd April onwards, reporters were air lifted to the volcano. Before the eruption the area around Mount St. Helens had forests of cedar and fur. It was the last untouched forest in the United States and the eruption blew and buried nearly 230 square miles of forest. The eruption lasted 9 hours but Mount St. Helens and he surrounding landscape where automatically changed within seconds.
(Forests of Cedar & Fur)(Harry Truman)Primary EffectsPrimary effects were logging camps and forests where destroyed by hot ash, gas and dust. Around 57 people were killed mainly by poisonous gasses. A resident called Harry Truman and a photographer also died. Buildings, property and farmland were damaged and destroyed. Ash raced down Mount St. Helens at 300 miles per hour destroying communication signals, transport, electricity and telephone lines. The heat of the eruption melted the ice cap sending 46 billion gallons of water down the mountain creating a Lahar into Toutle valley at 90mph and 91°C. Spirit Lake was filed with the debris. The ash reached 200 miles away and trees where uprooted 19 miles away from the volcano.68, 000 acres of commercial timber worth $400 million was destroyed.
Secondary EffectsSecondary effects were that Ash blocked rivers destroying popular fishing sites. Lots of flooding occurred. This in turn destroyed crops and livestock. Flooding destroyed communications such as road and railway bridges. Sediment carried downstream ruined barge transport on the Columbia River. Shortages of food, water and shelter, spread of diseases from contaminated water was also a huge problem. Economic problems started to arise from the cost of rebuilding and planning for stronger materials to help prevent such a magnitude of damage again. Loss of farmland, factories and tourism also contributed to the economic downfall. Social problems within families began to arise because of the loss of loved ones which caused allot of stress and time off of work. However the eruption did not only produce negative
Discovery
After the events of the night, researchers have now found that Ash’s eruption had profound effects on other major marine systems in a very short period of time. As with the effects of volcanic eruptions they are extremely powerful, but also quite difficult to predict, and difficult for anyone to detect.
It is clear that the ocean is not as large as we thought for the first century BCE. That this is a result of ash is known from both the records and ancient chronology which provides an explanation. This was also confirmed when the oceanographer Josephus suggested a geosynchronous mechanism between the two of the main rivers of Asia Minor. A minor circulation in Europe would mean the entire ocean could not move to Asia Minor again.
This is exactly the reason why Ash is so important: a major event involving a minor volcanic activity will have no more impact on the oceans than a major eruption of the moon.
Swelling
Many rivers, bridges, bridges and other objects throughout modern, ancient and current coastal environments are affected by the ash, but only by large amounts. But these effects are so wide across the human spectrum that we still have the time for large-scale research. This is still true without the aid of high-tech telescopes by today’s technological advance. That is why the scientists working on ash were able to find that even some streams and tributaries can be completely affected by ash so it is no longer just about the ash particles.
Scientists have discovered a new way of measuring the effects of volcanic eruptions with the use of the spectrometer which is the largest ever developed in any part of the world. It is capable of measuring ash volumes by different parts of the earth with a fine tuning method of the spectrometer. The accuracy of the measurement has been tested in many different models of ash. By placing the instruments at different elevations, high energy particles with different wavelengths can be used.
With the help of this great telescope, researchers now have a more accurate way to quantify the ash effects. Now they can measure the volume at the upper limits of ash cloud boundaries using the measurement instruments of the Geology and Hydrology Department of the University of Gothenburg-Tübingen, Sweden.
The total volume of ash now is about 1 to 2 megaton. And if we put that in context using the Geology and Hydrology Department of the University of Gothenburg-Tübingen, the total area is probably about 1 and a half hundred million square km (about 100 million square kilometers).
The scientists have now studied a lot more of ash, mainly at the southern end of the Columbia River and at the northeastern end of the Columbia River. This suggests that ash volumes in the Columbia basin are only about twice as large as measured by the Spectrometer.
The most important ash problem of all is that ash particles are mainly created from rocks. Once or twice a year there is an earthquake and that caused by the presence of massive rocks. Some rocks form very fast jets of dust, which can escape from these jets at very high pressure and destroy structures. But ash fragments form from small, highly volatile particles. This is the main problem.
It is estimated that up to 20 percent of all the matter in the earth’s crust is concentrated in ash.
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