|
Eruption Summary -
Mount St. Helens Eruptions Since May 18, 1980 |
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|---|---|---|---|---|---|---|---|---|
| Date eruption began |
Explosive activity /
Ash plumes |
Pyroclastic flows /
Lahars |
Facts of interest | Dome growth | ||||
| Onset of extrusion | Duration (days) |
Erupted volumea
(million cubic meters |
Dome volumeb
(million cubic meters |
Dome dimensionsc
(l x w x h, in meters) |
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| May 25, 1980 | explosive activity; plume to 9 miles | pyroclastic flows | ||||||
| Jun 12, 1980 | explosive activity; plume to 2.5 miles | pyroclastic flows | 1/2-inch-size pumice fell in Cougar, 10 miles downwind | Jun 13 | 7 | 5 | 5 | 365-365-45 |
| Jul 22, 1980 | three explosive pulses; plumes to 6-11 miles; June dome destroyed | pyroclastic flows | plumes seen in Tacoma, WA, 100 miles north | |||||
| Aug 7, 1980 | explosive activity; plume to 7-8 miles | pyroclastic flows | Aug 8 | 2 | 1 | 1 | 120-120-60 | |
| Oct 16, 1980 | explosive activity; plume to 8-9 miles; August dome destroyed | pyroclastic flows | Oct 18 | 1 | 1.2d | 1.2d | 300-300-34 | |
| Dec 27, 1980 | produced two lobes on dome (N and S) | Dec 27 | 7 | 1.6 | 2.8 | 440-320-93 | ||
| Feb 5, 1981 | small tephra-laden plumes accompanied start of extrusion | new lobe on top of dome | Feb 5 | 3 | 3.6 | 6.4 | 520-464-120 | |
| Apr 10, 1981 | small tephra-laden plumes accompanied start of extrusion, largest reached 1.5 miles above crater floor | lobe added on NNW flank of dome | Apr 10 | 3 | 4.1 | 10.5 | 666-470-129 | |
| Jun 18, 1981 | small tephra-laden plumes accompanied start of extrusion | lobe covered SW flank of dome to crater floor | Jun 18 | 2 | 4.1 | 14.6 | 574-520-161 | |
| Sep 6, 1981 | vigorous gas and ash emissions preceded start of extrusion | stubby lobe high on E flank of dome | Sep 6 | 5 | 3.9 | 18.5 | 680-590-161 | |
| Oct 30, 1981 | small tephra-laden plumes accompanied start of extrusion; small hot explosion during eruption produced ash layer on crater floor | Oct 30 | 4 | 3.6 | 22.1 | 680-660-184 | ||
| Mar 19, 1982 | most explosive activity since October 1980; plume to 9 miles; pumice deposited | March 19 mudflow reached Spirit Lake and N.F.Toutle; major hot rock-avalanche of April 4 created mudflow to N.F.Toutle valley | produced two lobes on dome (March, April) | Mar 19 | 24 | 3.4e | 24.5 | 760-600-195.1 |
| May 14, 1982 | small tephra-laden plumes accompanied start of extrusion | lobe on top dome | May 14 | 5 | 2.7 | 27.2 | 800-636-198 | |
| Aug 18, 1982 | lobe on W side of dome | Aug 18 | 6 | 4.6 | 31.8 | 820-692-204.1 | ||
| Feb 7, 1983 | minor eruptive activity preceded dome growth phase; largest plume to 2-4 miles | mudflows across crater; small flow reached Spirit Lake | produced two lobes (February, April); 200ft-high spine | Feb 7 | 368 | 22.4f | 53.2 | 860-780-227.3 |
| Mar 29, 1984g | Mar 29 | 5 | ||||||
| Jun 17, 1984g | Jun 17 | 2.0g | 54.2g | 860-790-227.1g | ||||
| Sep 10, 1984 | Sep 10 | 3 | 3.7 | 57.9 | 960-800-225.6 | |||
| May 24, 1985 | minor mudflows in crater | graben formed | May 24 | 17 | 4.3 | 62.2 | 1000-800-222.9 | |
| May 8, 1986 | May 8 | 5 | 5.8 | 68.0 | 1040-800-255.9 | |||
| Oct 21, 1986 | Oct 21 | 4 | 6.1 | 74.1 | 1060-860-267.2 | |||
|
aTotal volume erupted,
including tephra and rockfall debris
bNet volume of dome shown at end of each eruptive episode cDimensions at end of each extrusive episode, including talus. L, length; w, width, h, height above base of October 1980 lobe at assumed elevation of 1,914 meters. All measurements from topographic maps. dVolume of October 1980 lobe estimated from dimensions eIncludes pumice erupted on Marcy 19 and deposited beyond dome, and rock-avalanche of April 4 fIncludes notch in dome blown out and then refilled gIncludes estimated volume for March and June, 1984, lobes, and crater formed by explosions in May. | ||||||||
SourcesChristiansen and Peterson, 1981, Chronology of the 1980 Eruptive Activity: IN: Lipman and Mullineaux (eds.), The 1980 Eruptions of Mount St. Helens, Washington, USGS Professional Paper 1250; Swanson, et.al., Growth of the lava dome at Mount St. Helens, Washington (USA), 1981-1983: IN: Fink (ed.), The Emplacement of Silicic Domes and Lava Flows: GSA Special paper 212; Swanson, Casadevall, and Dzurisin, 1983, Predicting Eruptions at Mount St. Helens, June 1980 Through December 1982: Science, September 1983, v.221; Swanson and Holcomb, 1989, Regularities in Growth of the Mount St. Helens Dacite Dome, 1980-1986: IN: IAVCEI Proceedings in Volcanology, Vol.2, Lava Flows and Domes: Springer-Verlag; Tilling, Topinka, and Swanson, 1990, Eruptions of Mount St. Helens: Past, Present, and Future: USGS General Interest Publication; |
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| Table compiled by Lyn Topinka, USGS/CVO, June 17, 1997 | ||||||||
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