1985 Mexico City earthquake | |
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| Total costs | N/A |
| Deaths | 10000 |
The 1985 Mexico City earthquake struck in the early morning of 19 September at 07:17:50 (CST) with a moment magnitude of 8.0 and a maximal Mercalli intensity of IX (Violent). The event caused serious damage to the Greater Mexico City area and the deaths of at least 5,000 people. The sequence of events included a foreshock of magnitude 5.2 that occurred the prior May, the main shock on 19 September, and two large aftershocks. The first of these occurred on 20 September with a magnitude of 7.5 and the second occurred seven months later on 30 April 1986 with a magnitude of 7.0. They were located off the coast along the Middle America Trench, more than 350 kilometres (220 mi) away, but the city suffered major damage due to its large magnitude and the ancient lake bed that Mexico City sits on. The event caused between three and four billion USD in damage as 412 buildings collapsed and another 3,124 were seriously damaged in the city.
Source: Wikipedia 1980 Mount St. Helens | |
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| Total costs | N/A |
| Deaths | 57 |
On March 27, 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated until a major explosive eruption took place on May 18, 1980. The eruption, which had a Volcanic Explosivity Index of 5, was the most significant to occur in the contiguous United States since the much smaller 1915 eruption of Lassen Peak in California. It has often been declared the most disastrous volcanic eruption in U.S. history. The eruption was preceded by a two-month series of earthquakes and steam-venting episodes caused by an injection of magma at shallow depth below the volcano that created a large bulge and a fracture system on the mountain's north slope. An earthquake at 8:32:11 am PDT (UTC−7) on Sunday, May 18, 1980 caused the entire weakened north face to slide away, creating the largest landslide in recorded history. This allowed the partly molten rock, rich in high-pressure gas and steam, to suddenly explode northward toward Spirit Lake in a hot mix of lava and pulverized older rock, overtaking the landslide. An eruption column rose 80,000 feet (24 km; 15 mi) into the atmosphere and deposited ash in 11 U.S. states and two Canadian provinces. At the same time, snow, ice, and several entire glaciers on the volcano melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly 50 miles (80 km) to the southwest. Less severe outbursts continued into the next day, only to be followed by other large, but not as destructive, eruptions later that year. Thermal energy released during the eruption was equal to 26 megatons of TNT.About 57 people were killed, including innkeeper and World War I veteran Harry R. Truman, photographers Reid Blackburn and Robert Landsburg, and geologist David A. Johnston. Hundreds of square miles were reduced to wasteland, causing over $1 billion in damage (equivalent to $3.5 billion in 2020), thousands of animals were killed, and Mount St. Helens was left with a crater on its north side. At the time of the eruption, the summit of the volcano was owned by the Burlington Northern Railroad, but afterward, the railroad donated the land to the United States Forest Service. The area was later preserved in the Mount St. Helens National Volcanic Monument.
Source: Wikipedia
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