Area of Mount St. Helens Before and After the 1980 Eruption

by Simona Platukyte

Submitted : Fall 2009

The 1980 eruption of Mount St. Helens was particularly devastating to the surrounding areas because it resulted in loss of life and economic loss. It has been suggested that the damage may have been much worse if the eruption would have taken place during the week instead of on a Sunday and if the weather conditions would have been different. In 1982, President Reagan and Congress set up a National Monument in the area that was affect by the eruption to allow the land to recover and for scientists to carry out research. Because the volcano is still active, it is important to understand how the current physical features of Mount St. Helens may contribute to future eruptions and use this knowledge to devise better public policy regulating human settlement in the area. The goal of this project was to estimate the area of the mountain before and after the eruption, using cross-section graphs in the North-South and East-West directions. Because the function of the profile graphs was unknown, the exact area could not be found through integration. Instead, the Midpoint Rule was used to estimate the area in each case. This consisted of dividing the area under the profile curve into equal subintervals on the x-axis. Their height was determined by the value on the graph at the midpoint of each subinterval and the sum of their areas was the approximation for the area under the profile curve. In each case, the number of subintervals was doubled to determine if the approximation could be significantly improved. It was expected that the area of Mount St. Helens had decreased after the eruption because by looking at the profile graphs, it was noticed that the height had decreased. It was found that the area in the North-South direction decreased by about 20% whereas the area in the East-West direction decreased by only 5%. Possible causes and implications of these findings are discussed. Also, a recommendation is made for a future study relating to this subject.

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