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Stratovolcanoes

Mount St. Helens

The Cascade Range volcano whose eruption on 18 May 1980 began with the largest landslide ever recorded.

Elevation
2,549 m
Last eruption
2008
Confirmed eruptions
40
Max VEI
6
Country
United States
Location
46.20° N, 122.18° W
Region (GVP)
High Cascades Volcanic Arc
GVP type
Stratovolcano
Tectonic setting
Subduction zone / Continental crust (> 25 km)
Main rock type
Dacite

Show on the timeline GVP entry ↗

Other volcanoes and strong earthquakes within 300 km

About the volcano

For two months in the spring of 1980, Mount St. Helens in Washington State swelled as magma pushed into it – its north flank bulged by a metre a day. On 18 May an earthquake brought the flank down in a gigantic landslide, and the released magma exploded sideways, flattening forests over hundreds of square kilometres. Fifty-seven people died, and the summit was lowered by about 400 metres. One of the best-documented eruptions in history, it changed how volcanoes are monitored. From 2004 to 2008 a new lava dome grew in the crater.

Eruption history

VEI – Volcanic Explosivity Index: 0 = lava outpouring, 4 = like Eyjafjallajökull 2010, 6 = like Pinatubo 1991, 7 = like Tambora 1815. The scale is logarithmic – each step is about 10 times more material.

StartEndVEIVent and dating
1 October 2004 27 January 2008 2 South of 1980-1986 lava dome · Observations: Reported
5 November 1990 14 February 1991 3 North side of lava dome · Observations: Reported
7 December 1989 6 January 1990 2 North side of lava dome · Observations: Reported
27 March 1980 28 October 1986 5 Summit and north flank · Observations: Reported
16 April 1857 — 2 Observations: Reported
16 February 1854 16 April 1854 2 North flank · Observations: Reported
15 March 1853 16 August 1853 2 North flank · Observations: Reported
16 March 1850 16 May 1850 2 North flank · Observations: Reported
1 April 1848 — 2 Observations: Reported
26 March 1847 30 March 1847 2 North flank (Goat Rocks) · Observations: Reported
22 November 1842 18 September 1845 3 North flank (Goat Rocks) · Observations: Reported
16 March 1835 — 2 North flank (Goat Rocks area) · Observations: Reported
16 August 1831 — 3 North Flank (Goat Rocks area) · Observations: Reported
15 January 1800 — 5 N flank--Goat Rocks area · Sidereal: Dendrochronology
1610 ± 40 years — ? Pre-1980 summit dome · Isotopic: 14C (calibrated)
1525 ± 25 years — ? Sidereal: Dendrochronology
15 January 1482 — 5 Sidereal: Dendrochronology
15 January 1480 — 5 Sidereal: Dendrochronology
780 ± 300 years — ? NE flank (Sugar Bowl) · Isotopic: 14C (uncalibrated)
c. 420 — ? Isotopic: 14C (calibrated)
c. 270 — ? Isotopic: 14C (calibrated)
c. 230 — 0 Correlation: Tephrochronology
c. 190 — ? Lower E flank (East Dome) · Isotopic: 14C (calibrated)
c. 100 — 0 SW flank (Cave basalts) · Isotopic: 14C (calibrated)
c. 100 BCE — ? Isotopic: 14C (calibrated)
c. 220 BCE — ? NNE flank (Dogs Head) · Isotopic: 14C (calibrated)
c. 250 BCE — ? Correlation: Tephrochronology
c. 280 BCE — ? Isotopic: 14C (calibrated)
c. 530 BCE — 5 Isotopic: 14C (calibrated)
c. 800 BCE — ? Isotopic: 14C (calibrated)
830 BCE ± 75 years — ? Isotopic: 14C (uncalibrated)
c. 1,010 BCE — ? Isotopic: 14C (calibrated)
c. 1,100 BCE — ? Isotopic: 14C (calibrated)
c. 1,180 BCE — ? Isotopic: 14C (calibrated)
c. 1,610 BCE — ? Isotopic: 14C (calibrated)
c. 1,680 BCE — ? Isotopic: 14C (calibrated)
1,770 BCE ± 100 years — 5 Correlation: Tephrochronology
c. 1,860 BCE — 6 Isotopic: 14C (calibrated)
2,100 BCE ± 300 years — ? Correlation: Tephrochronology
c. 2,340 BCE — 5 Isotopic: 14C (calibrated)

Data: Global Volcanism Program, Smithsonian Institution (#321050) · Wikipedia (pl) · Wikipedia (en)