"Cascade Range Summary"
Mount Adams, Washington |
Mount Adams Volcano:
Mount Adams, one of the largest volcanoes in the Cascade Range (3,742 meters - 12,276 feet), dominates the Mount Adams volcanic field in Skamania, Yakima, Klickitat, and Lewis counties and the Yakima Indian Reservation of south-central Washington. The nearby Indian Heaven and Simcoe Mountains volcanic fields lie west and southeast, respectively, of the 1250 square kilometers (500 square miles) Adams field. Even though Mount Adams has been less active during the past few thousand years than neighboring Mounts St. Helens, Rainier, and Hood, it assuredly will erupt again. Future eruptions will probably occur more frequently from vents on the summit and upper flanks of Mount Adams than from vents scattered in the volcanic fields beyond. Large landslides and lahars that need not be related to eruptions probably pose the most destructive, far-reaching hazard of Mount Adams. -- Scott, et.al., 1995 Eruptive History: Mount Adams stands astride the Cascade Crest some 50 kilometers due east of Mount St. Helens. The towering stratovolcano is marked by a dozen glaciers, most of which are fed radially from its summit icecap. In the High Cascades, Mount Adams is second in eruptive volume only to Mount Shasta, and it far surpasses its loftier neighbor Mount Rainier (which is perched on a pedestal of Miocene granodiorite). Adams's main cone exceeds 200 cubic kilometers, and at least half as much more was eroded during late Pleistocene time form earlier high-standing components of the compound edifice: peripheral basalt adds another 70 cubic kilometers or so. Nearly all the high cone above 2,300 meters in elevation was constructed during latest Pleistocene time, probably between 20 and 10 thousand years ago, explaining the abundance of late-glacial till and the scarcity of older till. -- Hildreth, 1990, IN: Wood and Kienle Recent Volcanic Activity: Approximately 1,000 years ago: four tephra falls and perhaps small lava flows from two vents on upper flanks. -- Scott, et.al., 1995 Debris Avalanches and Lahars: During the past 10,000 years, the steep upper slopes of Mount Adams have produced several notable debris avalanches. In 1921, about 4 million cubic meters (5 million cubic yards) of altered rock fell from the head of Avalanche Glacier on the southwest flank of the volcano and traveled almost 6 kilometers (4 miles) down Salt Creek valley. The debris avalanche contained or acquired sufficient water to partly transform into small lahars. Ancient debris avalanches of much larger size have also occurred at Mount Adams, and these formed lahars that traveled far down the White Salmon and other valleys. An avalanche of roughly 70 million cubic meters (90 million cubic yards) of debris initiated the largest of these lahars about 6000 years ago. This lahar inundated the Trout Lake lowland and continued down the valley of the White Salmon River at least as far as Husum, more than 55 kilometers (35 miles) from Mount Adams. The lahar deposit left in the lowland varies from 1 to 20 meters (3 to 65 feet) thick; it is clearly visible today as a sediment layer in the banks of the White Salmon River and as isolated blocks (some more than 5 meters (16 feet) in diameter) that protrude from fields and meadows. -- Scott, et.al., 1995 MORE Mount Adams:
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