Mount St Helens


Mount St Helens, made famous in recent times by the eruption in 1980 has many pages about it on the internet and there is little point in me repeating all that information other than the basics.

Jump to seismograph stations

USGS Photograph taken on May 19, 1982, by Lyn Topinka. Click the image to go to the CVO website for a larger image.

[Excerpts from the CVO website]

Mount St. Helens was known as “the Fuji of America” because its symmetrical beauty was similar to that of the famous Japanese volcano. The graceful cone top, whose glistening cap of perennial snow and ice dazzled the viewer, is now largely gone as you can see in the image above.

Mount St. Helens, like most other Cascade volcanoes, is a great cone of rubble consisting of lava rock interlayered with pyroclastic and other deposits. Volcanic cones of this internal structure are called composite cones or stratovolcanoes. Mount St. Helens includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit; another formed Goat Rocks on the northern flank.

Northwest Indians told early explorers about the firey Mount St. Helens. In fact, an Indian name for the mountain, Louwala-Clough, means “smoking mountain”. According to one legend, the mountain was once a beautiful maiden, “Loowit”. When two sons of the Great Spirit “Sahale” fell in love with her, she could not choose between them. The two braves, Wyeast and Klickitat fought over her, burying villages and forests in the process. Sahale was furious. He smote the three lovers and erected a mighty mountain peak where each fell. Because Loowit was beautiful, her mountain (Mount St. Helens) was a beautiful, symmetrical cone of dazzling white. Wyeast (Mount Hood) lifts his head in pride, but Klickitat (Mount Adams) wept to see the beautiful maiden wrapped in snow, so he bends his head as he gazes on St. Helens.

Below is a photograph of Mt St Helens as it was before the last eruption.

USFS Photograph taken before May 18, 1980, by Jim Nieland, U.S. Forest Service, Mount St. Helens National Volcanic Monument. Click for full size image

[From: Brantley, 1994, Volcanoes of the United States: USGS General Interest Publication, online version 1.1]

Mount St. Helens, Washington: The catastrophic eruption on May 18, 1980, was preceded by 2 months of intense activity that included more than 10,000 earthquakes, hundreds of small phreatic (steam-blast) explosions, and the outward growth of the volcano’s entire north flank by more than 80 meters. A magnitude 5.1 earthquake struck beneath the volcano at 08:32 on May 18, setting in motion the devastating eruption.

Within seconds of the earthquake, the volcano’s bulging north flank slid away in the largest landslide in recorded history, triggering a destructive, lethal lateral blast of hot gas, steam, and rock debris that swept across the landscape as fast as 1,100 kilometers per hour. Temperatures within the blast reached as high as 300 degrees Celsius. Snow and ice on the volcano melted, forming torrents of water and rock debris that swept down river valleys leading from the volcano. Within minutes, a massive plume of ash thrust 19 kilometers into the sky, where the prevailing wind carried about 540 million tons of ash across 57,000 square kilometers of the Western United States.

Seismograph staions near to Mt St Helens
Below the map are links to the current and previous day seismograms for many of these stations.

Station
(Dist miles)
Link Link
CC.NED (0.47m)
NE part of old Dome
Today Yesterday
CC.SEP (0.47m)
September lobe, Mt. St. Helens
Today Yesterday
CC.VALT (0.86m)
Mt. St. Helens Crater, WA
Today Yesterday
CC.SWFL (1.13m)
Southwest Flank
Today Yesterday
UW.EDM (1.46m)
East Dome
Today Yesterday
UW.HSR (2.1m)
South Ridge
Today Yesterday
UW.SHW (2.97m)
Mt. St. Helens
Today Yesterday
UW.SOS (3.35m)
Source Of Smith Creek
Today Yesterday
PB.B202 (3.35m)
windyr202bwa2007 (Windy Ridge)
Today Yesterday
UW.STD (3.41m)
Studebaker Ridge
Today Yesterday
CC.STD (3.41m)
Studebaker Ridge
Today Yesterday
UW.JUN (3.72m)
June Lake
Today Yesterday
PB.B204 (4.1m)
marble204bwa2007
Today Yesterday
UW.FL2 (8.2m)
Flat Top 2
Today Yesterday
UW.CDF (8.3m)
Cedar Flats
Today Yesterday
UW.TDL (10.6m)
Tradedollar Lake
Today Yesterday
UW.ELK (10.8m)
Elk Rock
Today Yesterday

Other links

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