Message:22579 In: TODAY.WW
From: KF5JRVDate: Mon, 18 May 26 08:32:00 Z
Newsgroups: TODAY.WW
Subject: Today in History - May 18
Message-ID: <25648_KF5JRV>
Path: N2NOV|VE2PKT|VE7ASS|VA7RBP|KF5JRV
R:260518/0839z @:N2NOV.#RICH.NY.USA.NOAM $:25648_KF5JRV
R:260518/0838Z 8557@VE2PKT.#TRV.QC.CAN.NOAM LinBPQ6.0.25
R:260518/0838Z 51413@VE7ASS.#VAN.BC.CAN.NOAM LinBPQ6.0.24
R:260518/0837Z 37981@VA7RBP.#SCBC.BC.CAN.NOAM LinBPQ6.0.25
R:260518/0832Z 25648@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.24
At 8:32 a.m. PDT on May 18, 1980, Mount St. Helens, a volcanic peak in southwestern Washington, suffers a massive eruption, kil
ling 57 people and devastating some 210 square miles of wilderness.
Called Louwala-Clough, or “the Smoking Mountain,” by Native Americans, Mount St. Helens is located in the Cascade Range and
stood 9,680 feet before its eruption. The volcano has erupted periodically during the last 4,500 years, and the last active pe
riod was between 1831 and 1857. On March 20, 1980, noticeable volcanic activity began with a series of earth tremors centered o
n the ground just beneath the north flank of the mountain. These earthquakes escalated, and on March 27 a minor eruption occurr
ed, and Mount St. Helens began emitting steam and ash through its crater and vents.
Small eruptions continued daily, and in April people familiar with the mountain noticed changes to the structure of its north f
ace. A scientific study confirmed that a bulge more than a mile in diameter was moving upward and outward over the high north s
lope by as much as six feet per day. The bulge was caused by an intrusion of magma below the surface, and authorities began eva
cuating hundreds of people from the sparsely settled area near the mountain. A few people refused to leave.
On the morning of May 18, Mount St. Helens was shaken by an earthquake of about 5.0 magnitude, and the entire north side of the
summit began to slide down the mountain. The giant landslide of rock and ice, one of the largest recorded in history, was foll
owed and overtaken by an enormous explosion of steam and volcanic gases, which surged northward along the ground at high speed.
The lateral blast stripped trees from most hill slopes within six miles of the volcano and leveled nearly all vegetation for a
s far as 12 miles away. Approximately 10 million trees were felled by the blast.
The landslide debris, liquefied by the violent explosion, surged down the mountain at speeds in excess of 100 miles per hour. T
he avalanche flooded Spirit Lake and roared down the valley of the Toutle River for a distance of 13 miles, burying the river t
o an average depth of 150 feet. Mudflows, pyroclastic flows, and floods added to the destruction, destroying roads, bridges, pa
rks, and thousands more acres of forest. Simultaneous with the avalanche, a vertical eruption of gas and ash formed a mushroomi
ng column over the volcano more than 12 miles high. Ash from the eruption fell on Northwest cities and towns like snow and drif
ted around the globe for two weeks. Fifty-seven people, thousands of animals, and millions of fish were killed by the eruption
of Mount St. Helens.
By late in the afternoon of May 18, the eruption subsided, and by early the next day it had essentially ceased. Mount St. Helen
s’ volcanic cone was completely blasted away and replaced by a horseshoe-shaped crater–the mountain lost 1,700 feet from th
e eruption. The volcano produced five smaller explosive eruptions during the summer and fall of 1980 and remains active today.
In 1982, Congress made Mount St. Helens a protected research area.
Mount St. Helens became active again in 2004. On March 8, 2005, a 36,000-foot plume of steam and ash was expelled from the moun
tain, accompanied by a minor earthquake. Another minor eruption took place in 2008. Though a new dome has been growing steadily
near the top of the peak and small earthquakes are frequent, scientists do not expect a repeat of the 1980 catastrophe anytime
soon.
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
Email KF5JRV@gmail.com
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