Aerial view of Mount St. Helens shows ash and steam eruption. Skamania County, Washington. 1980.

Caption: Mount St. Helens sends ash plume two miles high. March 28, 1980 aerial view of Mount St. Helens showing ash and steam eruption that sent volcanic material almost two miles above the mountain's 9,677-foot peak. When the main eruption violently occurred seven weeks later on May 18, 1980, an estimated minimum of 1 cubic kilometer (1.3 billion cubic yards) of ash and rock was ejected by the volcano, according to USGS scientists. In comparison, Mt. Vesuvius spewed slightly more than 1 cubic kilometer in its eruption in 79 A.D. that buried Pompeii. The eruption of Indonesia's Krakataua in 1883 produced over 20 cubic kilometers. The force of the volcanic blast on that Sunday morning in May 1980, was estimated to be the energy equivalent [...]