 |
Narrative of Mount St. Helens The mountain and its
surroundings were peaceful during the last century of settlement and development, but the
serenity was misleading. To the practiced eye, the conical shape and composition of rocks
on the mountain boldly proclaimed Mount St. Helens' true nature--it was a volcano.
Abundant evidence of prior eruptions was apparent to anyone who cared to look. Lava flows
and thick deposits of ash (powdered volcanic rock) lay everywhere under the carpet of
trees. Even beautiful Spirit Lake was created by a volcanic accident, a giant mudflow that
rolled down the mountain about 3000 years ago and backed up a stream. Photo: Courtesy of NGDC/NOAA.The local Indians called Mount St. Helens "fire mountain" and were reluctant to approach it despite the abundant game in the area. The mountain continued to emit occasional bursts of ash and fire between 1832 and 1857. After that, Mount St. Helens "dozed off" for over a century. During this nap, Easterners migrated into the area and began a significant settlement.
On May 18, a quiet Sunday morning, a few volcanologists were at their stations, watching Mount St. Helens. A few tourists and loggers were also nearby. At 8:32 A.M., a small aircraft with two geologists aboard flew directly over the central cone. Eleven seconds later, a strong earthquake shook Mount St. Helens, and the whole north face of the mountain broke free and slid downward as a giant rock avalanche. In seconds, as the rock slid off the mass of hot lava inside the mountain, pressure in the lava dropped, and water dissolved in the lava turned into a superheated steam which fragmented the lava into a fine powder ash. This mass of super heated steam and ash blasted upward and outward over the top of the avalanche, roaring to the north and west at speeds reaching hundreds of miles an hour. The small aircraft avoided disaster by turning sharply south, away from the expanding ash cloud. [ Narrative of Mt. St. Helens: page 1 / page 2 / page 3 / page 4 / page 5 ] |
HTML code by Chris Kreger
Maintained by ETE Team
Last updated October 23, 1998
Privacy Statement and Copyright© 1997-2000 by Wheeling Jesuit University/NASA Classroom of the Future™. All rights reserved.
The quiet ended rather
abruptly in March, 1980, with a series of steam explosions and bursts of ash. During the
succeeding months, volcanologists and seismologists closely watched the mountain. Small
earthquakes accompanied the bursts and indicated the intrusion of fresh lava into the
heart of the mountain. Enormous cracks appeared in the summit and sides of the mountain,
and the entire northern face of the mountain expanded outward some 450 feet. All of this
initial activity was minor, and in spite of warnings and the designation of the mountain
and its surroundings as a dangerous "Red Zone," tourists flocked to the area and
evaded the overworked rangers to get a close view of the fireworks. Residents of the area
were strongly advised to move away,