火山分析和总结.docxVIP

The Earth’s Hidden Power Comes To The Surface “Vancouver! Vancouver! This is it!” The excited cry of a young scientist, Da vid Johnston, to his colleagues in Vancouver， Washington announced the long-awaited eruption of Mount St. Helens. These were David Johnston’s last words. An instant later, his observation post six miles from the peak was swallowed up by a wave of fiery hot gases and pieces of rock. The eruption of Mount St. Helens in the southwestern corner of Washington on May 18, 1981, was equal in force to the largest hydrogen bomb ever tested. People in the North-west had been anticipating an eruption for some time, but the blast was much bigger than expected. At 8:32 on a peaceful Sunday morning the mountain “blew its top”. Clouds of gas, ash, and rock shot into the air. As much as three inches of ash covered towns in Washington, Idaho, and Montana hundreds of miles away. The thick clouds of ash stopped all car and air traffic and forced residents to stay inside or put on face masks. The blast leveled forests 17 miles away, and boiling mud flowed down the mountain’s sides into neighboring rivers. As a result, the water temperature rose sharply from 50°to90°F., causing fish to jump out of the hot water onto the banks. The eruption took the lives of 64 people around the sides of the mountain. Among those killed or injured were scientists, miners, residents, and curious tourists who had not listened to the warnings they had been given. The 200-square-mile area north of the mountain covered by a grey blanket ash looked like a scene from a different planet. The west coast of the United States is famous for its volcanic activity and earthquakes. Scientists have been trying to understand what powerful underground forces can produce these dramatic acts of nature. One popular theory is known as continental drift. According to this theory, the surface of the earth is like the cracked shell of a soft-boiled egg. The outer crust of the earth is made up of pieces, calle