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KF5JRV > TODAY 18.05.19 13:30l 66 Lines 3518 Bytes #999 (0) @ WW
BID : 36560_KF5JRV
Read: GUEST
Subj: Today in History - May 18
Path: IW8PGT<IR2UBX<F1OYP<ON0AR<OZ5BBS<CX2SA<N3HYM<KF5JRV
Sent: 190518/1124Z 36560@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.18
At 8:32 a.m. PDT, Mount St. Helens, a volcanic peak in southwestern
Washington, suffers a massive eruption, killing 57 people and
devastating some 210 square miles of wilderness.
Called Louwala-Clough, or “the Smoking Mountain,ö 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 period was between 1831 and 1857.
On March 20, 1980, noticeable volcanic activity began again with a
series of earth tremors centered on the ground just beneath the north
flank of the mountain. These earthquakes escalated, and on March 27 a
minor eruption occurred, 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 face. A
scientific study confirmed that a bulge more than a mile in diameter was
moving upward and outward over the high north slope by as much as six
feet per day. The bulge was caused by an intrusion of magma below the
surface, and authorities began evacuating 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 followed 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 as 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. The avalanche
flooded Spirit Lake and roared down the valley of the Toutle River for a
distance of 13 miles, burying the river to an average depth of 150 feet.
Mudflows, pyroclastic flows, and floods added to the destruction,
destroying roads, bridges, parks, and thousands more acres of forest.
Simultaneous with the avalanche, a vertical eruption of gas and ash
formed a mushrooming column over the volcano more than 12 miles high.
Ash from the eruption fell on Northwest cities and towns like snow and
drifted around the globe within 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. Helens’ volcanic cone
was completely blasted away and replaced by a horseshoe-shaped
crater–the mountain lost 1,700 feet from the 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 mountain,
accompanied by a minor earthquake. 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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