Lateral Blast Essay, Research Paper
Lateral Blast The sudden
removal of the volcano’s north flank released pressure on the hydrothermal and magmatic system within the volcano,
triggering a devastating lateral blast to the north. The abrupt pressure
release, or "uncorking," of the volcano by the avalanche can be
compared in some ways to the removal of the cap from a vigorously shaken bottle
of soda pop, or to punching a hole in a boiler tank under high pressure. The
northward-directed lateral blast of rock, ash,
and hot gas devastated an area of about 150 square miles. The blast stripped trees from most hill slopes
within six miles north of the volcano and leveled nearly all vegetation for as
far as 13 miles in a 180-degree arc north of the mountain. The blast deposited
blocks and smaller rock fragments and organic debris over the devastated area
in layers to more than three feet in thickness. Surrounding this zone of
toppled vegetation is a narrow band of scorched but standing timber in which sandy deposits
are as thick as four inches; this zone has an area of about 25 square miles. The Eruption A
magnitude 5.1 earthquake on May 18 (8:32 a.m. PDT) shook loose the steepened
bulge on the volcano’s north flank,
resulting in the largest known landslide in historic time, 2.3 cubic km (0.56
cubic miles). The entire north flank was described by an aerial observal as
"rippling" and "churning" moments before "the north
side of the summit began sliding north along a deep-seated slide plane." As the avalanche reached the north base of the
cone, the topography it encountered caused it to be divided into three
Part of the
avalanche slid into Spirit Lake, raising the lake bed roughly 180 feet, and
damming its natural outlet. Water displaced by the avalanche surged up the
surrounding hillslopes, washing the blown-down
timber from the lateral blast into the lake. 2.
Part of the
avalanche "ramped" up and over a 1,200 foot high ridge five miles
north of the volcano (Johnston Ridge) depositing debris on top of the ridge and
in the South Colwater Creek drainage. 3.
The bulk of
the avalanche was deflected westward down the North Fork of the Toutle River
valley. The front of the avalanche traveled a distance of 15 miles in about 10
minutes. The resulting deposit covers the valley floor to an average depth of
150 feet, but it is more than 500 feet deep in a few places (such as 1.5 miles
west of Harry Truman’s Lodge). The hummocky avalanche deposit covers a
total area of about 24 square miles. It consists of intermixed volcanic debris
of various sizes, including blocks, pebbles, sand and silt, and blocks of
glacial ice. Mount Saint Helens: The Great Eruption Anonymous
Teacher/Mentor: Rene Dolbec Mount Saint Helens is located in Southern Washington.
Before May 18, 1980 the mountain stood still and was silient and beautiful. Mt.
St. Helens is a composite cone, also called stratovolcanoes which are very
large. These types of volcanoes consists of layers of both lava and cinder. The
layers of lava causes the volcanoes to be more resistant to erosion. Andesite
lava is more "sticky" than basalt and tends to be more explosive. The
first recorded eruption of the mountain was estimated around 40,000 years ago.
In 1802 A.D. there was a great eruption of ash. About this time mudflows and
lava flows occurred. On May 18, 1980 around 8:31 a.m.
Mount Saint Helens erupted. Denver Nelson predicted that the eruption would
occur at 8:30 Sunday morning, and missed his prediction by one minute.
Seventeen missing people were presumably said to be dead from being s o close
to the mountain. Including one eighty year old man who refused to leave his
home, which he had lived in for fifty years, on the side of Mt. St. Helens.
Thinking that he knew the mountain so well that it would never hurt him. But he
was wrong. His memorial would be one everyone at that time would remember. On July 22 two months after the eruption,
the mountain sends plume high into the sky. After the big eruption, the
northern side of Mt. St. Helens was said to look like the surface of the moon.
It was gray and lifeless. When the warm weather started to come, you could
start to see touches of green among the grays and brown. Some small animals
such as chipmunks, white-footed deer mice, and red squirrels had survived under
the snow pack or below the ground. Hundred years from now, a new forest will be
g rowing on the north slope of Mount Saint Helens. Everything that lived on the
mountain before May 18, 1980, will be able to live there again.It depends on what and where you
are talking about. For example, there are many places on Mt. St. Helens that
today still look as bleak as the days after the big eruption. These tend to be
the locations closer to the volcano. On the other hand there are areas that
were covered by quite thick blankets of ash and debris where the plants have
come back to the point that you could be plunked down in the middle of the
forest and not know that something dramatic had even happened. In general, the areas on the edges
of the devastated zones are coming back the fastest because there are sources
of seeds and animals in the adjacent un-devastated zones. The hunting and
fishing industry in and around Spirit Lake has not recovered at all. Volcanologists are getting much
better at predicting eruptions. Several methods are used to monitor volcanoes. These methods are
applied to volcanoes that have shown signs of unrest. The past behavior of the
volcano would provide the best estimate of the potential volume of future
eruptions. Volcanoes erupt because of pressure caused by gas dissolved in the
magma. Different size eruptions are caused by the volume of the magma, magma
supply rate, eruption frequency, composition of magma, size of the conduit, and
gas content. Mount St. Helens was explosive because the magma was viscous
(sticky) and the gas could not escape until it was in the throat of the
volcano. Then the gas expanded and blew the lava into ash-sized fragments.
Sorry, I have not seen "joe vs the volcano" but I hear it is funny.
Most movies (and some TV shows) dont worry much about the accuracy of the
science information – they just want it to be exciting.
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