On what date did the 1980 eruption of Mount St. Helens, in which "Crater Glacier" was formed, occur?
1980 eruption of Mount St. Helens On May 18, 1980, a major volcanic eruption occurred at Mount St. Helens, a volcano located in Skamania County, in the state of Washington, United States. The eruption (a VEI 5 event) was the only significant volcanic eruption to occur in the contiguous 48 U.S. states since the 1915 eruption of Lassen Peak in California. However, it has often been declared as the most disastrous volcanic eruption in United States 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.
Harrison Glacier Harrison Glacier is located in the US state of Montana in Glacier National Park. Situated on a southeast facing ridge immediately south of Mount Jackson, Harrison Glacier is the largest glacier in Glacier National Park and was estimated in 2005 to have an area of 466 acre . Though many experts have stated that all the glaciers in Glacier National Park may disappear by the year 2030, Harrison Glacier lost only 9 percent of its surface area in the 40-year period between 1966 and 2005 and will likely still exist well beyond 2030. Compared to many of the vanishing glaciers in Glacier National Park, Harrison Glacier has a much higher altitude accumulation zone (approximately 9000 ft ) which has allowed it to maintain some equilibrium in its glacier mass balance. Comparing images of the glacier taken in 1913 with those from 2009, indicates that the glacier has experienced thinning and retreat.