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Mount St. Helens -
Summary of Volcanic History
-- Excerpt modified from:
Doukas, 1990, U.S. Geological Survey Bulletin 18591
unless subscripted otherwise.
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| (Eruptive stages and periods are separated by dormant intervals for which no unequivocal volcanic products have been recognized. Years before 1980 are based on tree-ring dates (Yamaguchi, 1983), Carbon14 ages, and (or) historical records. A.D. dates during the Goat Rocks and Kalama eruptive periods from Yamaguchi (1983, 1985). All tephras consist of multiple layers not subdivided further here; only the thickest layers of W, B, and Y tephras are distinguished. After Crandell and others (1981), Mullineaux and Crandell (1981), and Crandell (1988))1 | |||
| Eruptive stages and periods | Eruptive products | ||
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Spirit Lake Eruptive Stage |
Modern eruptive period |
Began 1980 |
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Goat Rocks eruptive period |
150-100 years B.P. |
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| A.D. 1800 |
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Kalama eruptive period |
500-338 years B.P. |
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| A.D. 1647? |
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| A.D. 1482 |
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| A.D. 1480 |
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Sugar Bowl eruptive period |
1,200 years B.P. |
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Castle Creek eruptive period (first appearance of mafic magma at the surface, which initiated the modern Mount St. Helens)2 |
2,500-1,600 years B.P. |
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Pine Creek eruptive period |
3,000-2,500 years B.P. |
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Smith Creek eruptive period |
4,000-2,200 years B.P. |
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A dormant period of more than 6,000 years2
10,500 - 4,000 years ago |
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Swift Creek
eruptive stage |
13,700-9,200 years B.P.1
(between about 13,000 and 10,500 years ago)2 |
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| Mostly dormant interval of about 5,000 years2 | |||
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Fraser Glaciation
ended approximately 13,000 years B.P. |
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Cougar
eruptive stage |
20,400-19,200 years B.P.1
(began about 20,500 years ago, lasted only 2,000-3,000 years)2 |
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| Mostly dormant interval of about 15,000 years2 | |||
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Ape Canyon
eruptive stage |
approximately 40,000?-25,000 years B.P. |
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a
The term "blast deposit" is here used to designate a deposit resulting from any
process initiated by the lateral explosion. Precise transport and deposition
mechanisms are controversial (Walker and McBroome, 1983; Hoblitt and Miller,
1984; Waitt, 1984a; Walker and Morgan, 1984)
1 -- Michael P. Doukas, 1990, Road Guide to Volcanic Deposits of Mount St. Helens and Vicinity, Washington: U.S.Geological Survey Bulletin 1859, 53p. 2 -- Donal R. Mullineaux, 1996, Pre-1980 Tephra-Fall Deposits Erupted From Mount St. Helens, Washington: USGS Professional Paper 1563. |
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