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Geology of Interactions of Volcanoes, Snow, and Water:

RESULTS of Recent Surveys

Mount Redoubt, Alaska

Mount Redoubt west of Cook Inlet erupted 18 times between 14 December 1989 and early June 1990. Ash from one eruption nearly brought down a passenger-filled jetliner inbound for Anchorage. Floods caused by rapidly melted snow threatened an oil storage-and-loading facility at the mouth of Drift valley. Hot fragmental flows completely stripped the upper part of Drift glacier from its valley.

Mt. Spurr (Crater Peak), Alaska

Crater Peak at Mt. Spurr west of upper Cook Inlet erupted in June, August, and September 1992. Ashfall in August temporarily closed Anchorage International Airport. Hot fragmental debris melted snowpack to yield floods during each eruption. Impressive ballistics reveal water-based explosions near the end of each eruption.

Mt. Augustine, Alaska

Mt. Augustine volcano forms an island in southern Cook Inlet. It had substantial explosive eruptions in 1964, 1976, and 1986, a pattern suggesting that the next eruption may well occur during the mid- to late 1990s. Ash from Augustine eruption disrupts commercial air traffic, including Anchorage International Airport. The potentially most destructive hazard is from tsunami generated when a huge landslide ("debris avalanche") sweeps from the summit into the sea, as has happened often in the last 2000 years.

Mount St. Helens, Washington

Mount St. Helens erupted on 18 May 1980, its first large eruption in 123 years. During the first minutes of the eruption, a gigantic landslide ("debris avalanche") removed the former summit, slid down into Spirit Lake, where it raised a tsunami to astonishing heights. The landslide triggered a gigantic hot, turbulent flow ("pyroclastic surge") that swept outward to the west, north, and east across 600 square km (235 square miles), leveling a mature coniferous forest and killing 53 people. On the volcano cone the hot surge swiftly melted snowpack, engendering large floods down surrounding valleys. Smaller explosive eruptions occurred periodically until October 1986, most of them yielding snowmelt floods. For a popular early summary of the eruption, see U.S. Geological Survey Professional Paper 1249 (1982, 125 p.). For an early compendium of technical reports, see U.S. Geological Survey Professional Paper 1250 (1981, 844 p.).

Mount Rainier, Washington

Glacier Peak, Washington


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11/03/97, Lyn Topinka