Transcript Mount St. Helens - Westfield State University: Department

Mount St. Helens
By:
Chuck Wolfe
Chris LaPlante
Matt ‘Chang’ Madden
The Biggest Thing To Rock
Washington…
The Creation of the Beast
• Created 40,000 years ago
• Created from decite and andesite
eruptions
• Most of the Volcano’s bulk was created
over the last 2500 years
What, When, Where…
• What:
– Mt. St. Helens; a
majestic stratovolcano
that drew tourists from
thousands of miles
• When:
– Erupted on May 18,
1980
• Where:
– Washington State;
46.2N 122.18W
The Point is….
• Pre-eruption
– Early effects of the volcano
– The explosion of the Summit Dome
• Pyroclastic activity
– The establishment of pyroclastic activity
– The effect on the land surrounding the
volcano
Taking One to the “Dome”
• Geothermic activity heated underground
water
– Steam gradually built up which resulted in a
phreatic explosion
– Summit Dome exploded from the pressure,
hurling material across the landscape
She called out a warning…
• University of Washington deployed
portable seismographs.
• So well known that people came to
observe volcano for pleasure.
• Despite warnings, some people didn’t
want to leave.
Active History
• Mt. St. Helens has been dormant for a
century.
– Months before the 1980 eruption, seismic
activity has been recorded.
– Out of the Cascade Volcanic range, St.
Helens is presently the most active.
The Warning Signs To Doom
• Early Effects
– Earthquakes
began to increase
in quantity and
intensity.
• This led to the
breakup of St.
Helens icecaps
– The intrusion of
the Goat Rock
Dome
The Beginning of the Calamity
• Predictions come
true with the
occurrence of a 5.1
earthquake
– Causes biggest
landslide in recorded
history
• Second largest
eruption in U.S.
history
• Pyroclastic flows
– Hot mixtures of volcanic
gas, pumice, and ash
• Pyroclastic surge
– Low density surge of
pyroclastic material
– Carries less material, but
travels at much faster
rates
Pyroclastic
Spirit Lake
• Created by previous volcanic activity
thousands of years ago
• A heavily forested area before 1980
eruption
The Destruction of Spirit Lake
• Post-Eruption
– Barren land scattered with ash, tree trunks
scattered across the area, empty waterbed
Powerful Nature of the Surge
• The pyroclastic material is
capable of traveling up to
300 mph
• The temperature of
the rocks reach
200°C to 700°C
• Follow indentations
of crust (i.e. valleys
& canyons)
Range and Effect of the Flow
• The Mount St.
Helens
pyroclastic flow
created a 15
mile radius of
destruction
around the base
of the volcano
The Conclusion
• The destruction
– Flooding
– Pyroclastic flows;
• Melted icecaps
– Mudslides
– Falling debris
…Before
After…