mount st. helens by: chuck wolfe chris laplante matt ‘chang’ madden
TRANSCRIPT
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 • 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
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