The 1912 eruption that formed Novarupta was the largest to occur during the 20th century. It began on June 6, 1912, and culminated in a series of violent eruptions. Rated a 6 on the Volcanic Explosivity Index,[6] the 60-hour-long eruption expelled 3.1 to 3.6 cubic miles (13 to 15 km3) of ash, thirty times as much as the 1980 eruption of Mount St. Helens.[7][8][9] The erupted magma of rhyolite, dacite, and andesite[10] resulted in more than 4.1 cubic miles (17 km3) of air falltuff and approximately 2.6 cubic miles (11 km3) of pyroclastic ash-flow tuff.[11] During the 20th century, only the 1991 eruption of Mount Pinatubo in the Philippines and the 1902 eruption of Santa MaríainGuatemala were of comparable magnitude; Mount Pinatubo ejected 2.6 cubic miles (11 km3) of tephra,[12] and Santa María just slightly less.
The Novarupta eruption occurred about 6.59 mi (10.61 km) from the peak of Mount Katmai Volcano and 4,000 ft (1,200 m) below the post-eruption Mount Katmai summit. During the eruption a large quantity of magma erupted from beneath the Mount Katmai area, resulting in the formation of a 1.2-mile (2 km) wide, funnel-shaped vent and the collapse of Mount Katmai's summit, creating a 2,000-foot (600 m) deep,[7] 1.9 by 2.5 mi (3 by 4 km) caldera.[15]
The eruption ended with the extrusion of a lava domeofrhyolite[10] that plugged the vent. The 295-foot (90 m) high and 1,180-foot (360 m) wide dome it created forms what is now referred to as Novarupta.[16]
Despite the magnitude of the eruption, no deaths directly resulted.[17]: 3 [18] Eyewitness accounts from people located downwind in the path of a thick ash cloud described the gradual lowering of visibility to next to nothing.[19] Ash threatened to contaminate drinking water and destroyed food resources, but the Alaska Natives were aided in their survival by traditional knowledge passed down through generations from previous eruptions. However, the Native villages experiencing the heaviest ash falls were abandoned and the inhabitants relocated.[19]
The eruption that formed the Valley of Ten Thousand Smokes is one of the few in recorded history to have produced welded tuff, producing numerous fumaroles that persisted for 15 years.[21]
Established as a National Park & Preserve in 1980, Katmai is located on the Alaska Peninsula, across from Kodiak Island, with headquarters in nearby King Salmon, about 290 mi (470 km) southwest of Anchorage. The area was originally designated a National Monument in 1918 to protect the area around the 1912 eruption of Novarupta and the 40-square-mile (104 km2), 100-to-700-foot (30 to 210 m) deep, pyroclastic flow of the Valley of Ten Thousand Smokes.[22]
^Novarupta has been translated from Latin to multiple English meanings, including "newly erupted",[2] "new eruption",[3] "new break",[4] and "new vent".[5]
^ abWood, C.A. and Kienle, J. (editors) (1990) Volcanoes of North America: United States and Canada, Cambridge, Cambridge University Press, ISBN0-521-36469-8, p. 70.
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