Mount St. Helens is located in the state of Washington on the west coast of the United States. It is part of the Cascade Range, which is dominated by periodically active volcanic peaks. For most of the 20th century, the snow-covered mountain was known for its quiet beauty, until on 18 May 1980, the top 420 m (1 300 ft) disappeared within minutes. The blast leveled 400 km2 (249 square miles) of forest, formed a deep horseshoe crater, and sent thousands of tonnes of ash into the upper atmosphere. A major debris flow filled a valley 24 km long (15 miles). Sixty-two people were dead or missing. This eruption of Mount St. Helens was the most destructive in the history of the United States, with total economic losses estimated at US$1.2 billion (NGDC 2004). Growth of the new lava dome inside the crater of Mount St. Helens continues, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash (USGS 1999). Lessons learned from this and other volcanic activity in the Cascade Range will be invaluable to scientists for predicting such events and anticipating their ecological impacts (UNEP 2003). View detailed information
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