Presentation on theme: "MEDC Case Study - Mount St.Helens, USA"— Presentation transcript:
1MEDC Case Study - Mount St.Helens, USA Volcanic EruptionsMEDC Case Study - Mount St.Helens, USA
2Mount St. Helens, USA – MEDC Case Study Is part of the ring of fire.Well known for ash explosions and pyroclastic flows.Most famous eruption – 18th May 1980.57 people were killed, 250 homes destroyed.The 1980 eruption was the first time that it was possible to use modern technology to carefully monitor a volcano as it built up towards a violent eruption.Trees were pushed flat pointing away from the source of the blast. Such was the speed of the moving air and debris that it overtook cars as people tried to escape.Its last eruption was 10th July 2008!
4The little Juan de Fuca ocean plate slides under the continental plate. As the ocean plate descends the rock melts and magma rises.This has created the Cascade Range of volcanoes.
5Mt St Helens – causes of the eruption North American PlateJuan de Fuca plateThe Volcano at Mt St Helens was formed because the _________ plate is ________ under the _________ plate. When this happens _________ occurs and _______is formed under ____________ . The magma rises and when the pressure is _________ a volcanic eruption occurs.Juan de Fuca pressure North American Melting subducted magma released
6A bulge was growing on the north flank. April May 1980A bulge was growing on the north flank.May 18th at 8.32 a.m.An earthquake occurs under the volcano and triggers a huge landslide.May 18th at 8.33 a.m.With the pressure released a huge lateral blast heads northwardsMay 18th rest of the dayMore and more ash shoots up high into the atmosphere. It gradually blows around the world.
7PRIMARY EFFECTSMaterial from a massive landslide sped down the mountain, filling Spirit Lake and, mixed with lake water, racing down the Toutle and Kalama rivers as a mudflow (or lahar). Explosions of gas and steam flatened everything in its pathSnow melt mixed with ash and mud carried huge amounts of debris, trees, cars etcAsh clouds circulated the earth for 7 days.The volcano was reduced in height by 400 meters.57 DEAD.
8Pyroclastic CloudsThe pyroclastic cloud caused hundreds of trees to be completely destroyed beneath the volcano.
9Pyroclastic Flows – Mt. St.Helens May 1980 The pyroclastic flow contained large boulders up to 1 metre in diameterLarge bulldozer wrecked by the pyroclastic flow of May 18th 1980
10Pyroclastic Flows – Mt. St.Helens May 1980 AfterBeforeThe same marker pole
16Environmental Impacts Today’s Tasks(1) On your diagram from earlier, add some of the labels/numbers from diagram B. (2) Copy and complete the table below using diagram C (3) Complete the Mount St. Helens worksheetSocial ImpactsEconomic ImpactsEnvironmental Impacts