Mount
Saint Helens Documentary
This
documentary discussed the geological and volcanic conditions that lead to the
1980 eruption of Mt Saint Helens and what made this particular eruption unique.
Mt Saint Helens is part of the cascade mountain range and its unique conical
shape gave it the garnished nick name of the Mt Fuji of North America. In 1980
a series of earthquakes occurred in the area surrounding Mt Saint Helen.
Knowing that volcanic activity can generate earthquakes as a result of magma
forcing its way through the crust, groups of scientists and researchers flocked
to Mt Saint Helens to study this new activity. Scientists set up to measure the
amount of hydrogen sulfate being produced by the mountain under the assumption
that as more magma moved into the mountain and pressures increased, that the
volume of gas released would increase. This assumption would prove to be false
as the volume of gas released remained relatively stable even though the tremors
persisted.
After a few months of observation, individuals
and the public began to notice that the mountain no longer had its signature
conical shape, but now had a deformity protruding from the mountains north
side. A bulge began to form and data from measurements taken daily showed that
the bulge was growing by about 5ft per day. Geologists and volcanologists
hypothesized that migrating magma and gas pressure could be the cause of this
deformation. On the morning of May 18th 1980 Mount Saint Helens erupted,
surprising all of the researchers who had been studying the mountain. The
researchers knew there was activity in the mountain but none of their data
hinted that an eruption was imminent. The entire north side of the mountain
became destabilized and collapsed during a 5.4 earthquake, with no earth to
contain the pressure, magma and gas exploded out from the north side of Mt
Saint Helens, triggering a lateral eruption, decimating hundreds of acres of
forest. The eruption was so violent that the mountain changed its shape from an
elegant conical tower to a rough horseshoe shaped mountain. Rotten rock was
determined to have played a role in the collapse of the north face which lead
to the devastating eruption. Rock becomes rotten when hot water passes through
the rock, altering the chemistry of the sediment making it loose and crumbly.
With such a large portion of the mountain made up of rotten rock, when that
earthquake hit the crumbly and weakened bulge destabilized and collapsed in a
massive landslide.
Hot ash from the eruption melted
the snow and ice at the top of nearby peaks, causing massive flows of water and
sediment down from the mountain tops forming a lahar which blocked Spirit Lake
from its river. As time went on the snow melt continually flowed into Spirit
Lake causing the lake to rise to dangerous levels. Eventually Spirit Lake
overflowed creating a massive lahar which washed down the mountain destroying
thousands of woodlands. Knowledge of this put construction crews into action to
create a relief system for Spirit Lake so as to let the lake drain if the water
level got to high, in hopes of preventing any other lahars from forming.
An eruption
similar to that of Mount Saint Helens occurred in 1995 on the island of
Montserrat in the Phillipines. The volcano on this island also formed a
distinctive bulge making the scientists wary and inciting an order to evacuate
or relocate many of the islands citizens. Sure enough, seismic activity lead to
the collapse of the bulge creating a landslide and another lateral eruption,
just like that of Mt Saint Helens. The islands capital of Plymouth was
destroyed and covered in 30ft of mud. Thankfully, knowledge obtained from the
findings and experiences from the Mt Saint Helens eruption helped save thousands
of lives on that island.
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