Take a virtual tour around Mt. Shasta Billow Clouds/Kelvin-Helmholst Principle/Waves
Gallery of Mt. Shasta Pictures
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Eruptive HistoryMount Shasta in northern California, is a massive composite volcano consisting of overlapping cones centered at four main vents. The volcano was constructed during the last several hundred thousand years (Christiansen and Miller, 1976; Miller, 1980; Christiansen, 1985). Each of the cone-building periods produced andesite lava flows and pyroclastic flows, mainly at the central vents, as well as numerous lahars on and beyond the flanks of the volcano. Construction of each cone was followed by eruption of domes and pyroclastic flows of more silicic composition at central vents, and of domes, cinder cones, and lava flows at vents on the flanks of the cones. Two of the main eruptive centers at Mount Shasta, the Shastina and Hotlum (summit of Mount Shasta) cones, were formed during the last 10,000 yr (Miller, 1980). Holocene eruptions also occurred at Black Butte, a composite dacite dome about 13 km west of Mount Shasta (Miller, 1978). Geologically recent eruptions at these two main centers and at flank vents form the principal basis for assessing the most likely kinds of future eruptive activity and associated potential hazards. Streams that head on Mount Shasta drain into the Shasta River to the northwest, the Sacramento River to the west and southwest, and the McCloud River to the east, southeast, and south. The lower flanks of Mount Shasta consist mostly of broad, smooth coalescent fans formed by pyroclastic flows, lahars, and streams that descended the volcano along canyons and then spread out. As a result, pyroclastic flows and lahars at Mount Shasta have traveled a shorter distance from the volcano than they would have if they had been confined to narrow valleys. Their paths, on the fans, however, are less predictable.
Eruptions during the last 10,000 yr produced lava flows and domes on and around the flanks of Mount Shasta. Lava flows issued from vents near the summit and from flank vents as far as 9 km away, and individual flows are as long as 13 km. Only about 33 percent of past lava flows reached more than 10 km from the summit and none reached as far as 20 km.
Eruptions at the Hotlum and Shastina vents produced many lahars, about 20 percent of which reached more than 20 km from the summit of Mount Shasta, and spread out on fans around the base of the volcano. Even larger lahars and floods extended beyond the base of the volcano and entered the McCloud and Sacramento Rivers (Hill and Egenhoff, 1976; Miller, 1980). During Holocene time Mount Shasta erupted pumiceous dacite tephra twice about 10,000 yr ago (Miller, 1980). One deposit is more than 0.1 km3 in volume and the other is less than 0.1 km3; both lie mainly east and within about 50 km of the volcano. Lithic ash has been erupted at Mount Shasta many times during the last 10,000 yr and the deposits mantle the ground surface within about 25 km of the summit (Miller, 1980).
Volcanic-Hazards AssessmentFuture eruptions like those of the last 10,000 yr will probably produce deposits of lithic ash, lava flows, domes, and pyroclastic flows, and could endanger works of man that lie within several tens of kilometers of the volcano.
Owing to great relief and steep slopes, a portion of the volcano could also fail catastrophically and generate a very large debris avalanche and lahar. Such events could affect any sector around the volcano and could reach more than 50 km from the summit. Explosive lateral blasts could also occur as a result of renewed eruptive activity, or they could be associated with a large debris avalanche; such events could affect broad sectors to a distance of more than 30 km from the volcano.
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NEWSJune 29, 2021 Lava Fire Rages on Mount Shasta in Weed, Calif. After Lightning Strikes
June 13, 2017 Current Conditions at Mount Shasta and the McCloud River
Sept. 16, 2014 Breaking News: Boles Fire forces evacuations in Weed Wildfire burns homes, 2 churches in Weed, Calif. Sept. 21, 2014 UPDATE: Flash Flood Watch After Glacier Breaks Off Mt. Shasta Glacier breaks off Mt. Shasta Volcano in North California - Lahar mud flow |
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In memory of Susan Ekwall 10/19/1944-3/19/13 |
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Mt. Shasta City in front of Mt. Shasta |
Original sculpture for sale, Sedna, goddess of the sea