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Procedure
The instructor will:
1. Assign the following roles to different students:
• First Yellowstone caldera eruption (2 students)
• Second Yellowstone caldera eruption (2 students)
• Third Yellowstone caldera eruption (2 students)
• Glacial ice
• Glacial lake
• Glacial lake sediments (2 students)
• Yellowstone river
• Future Yellowstone caldera eruption (2 students)
2. Instruct the students to act out the attached skit.
3. Narrate the skit.
Script
Once upon a time, a hotspot lurked beneath the surface of the Earth, in a part of the world we now call Yellowstone National Park. It caused a HUGE volcanic eruption and deposited ayer upon layer of lava and ash on the Earth’s surface.
At this point, the students playing the first caldera eruption should carefully lie down on the floor, one on top of the other.
Many thousands of years passed by and the exposed lava (the uppermost layer) hardened into rock and then was slowly eroded away by exposure to the elements—wind, water, snow, and ice.
The uppermost student playing a layer should carefully get up and leave the stage.
The hotspot continued to melt rock beneath the earth’s surface. This magma slowly gathered into a great underground chamber. The earth’s crust was pushed upwards until once again—another HUGE eruption! Lava and ash hurtled out of the volcano’s caldera, settling in layers over the top of the hardened lava from the first eruption.
Students playing the second eruption should carefully lie down on top of the remaining layer from the first.
As the long years passed, the lava once more became rock. Once again, erosion removed the top layers of volcanic debris.
Top student gets up and leaves.
Time continued to pass and what do you think happened? Another eruption and more hardened lava flows! Anyone see a cycle here? The most recent eruption of the Yellowstone hotspot occurred about 640,000 years ago.
Students playing the third eruption get on top of the other two.
Geologists have a better record of what caused the erosion of more recent volcanic rock. For example, they have learned that up to 4,000 feet of glacial ice covered Hayden Valley at one time!
Student playing glacial ice joins pile.
Glaciers carved away some of the volcanic rock (top eruption student leaves). The outlet in Hayden Valley became blocked with ice and rock, and as the climate changed, the ice gradually melted (glacial ice leaves). The melt water formed a glacial lake over the top of the volcanic rock, and (student playing the glacial lake joins the pile) sediments slowly collected on its floor. By the time the water disappeared (glacial lake leaves); many layers of sediment blanketed the volcanic rock (sediment layers join the pile).
That isn’t the end of the story! For many years, and even today, the Yellowstone River has been eroding down into those sediments, creating constant change across the landscape in Hayden Valley.
At this point, the student playing the Yellowstone River should approach the pile and move the limbs of the sedimentary layers around to represent erosion and change.
What about the future? There may be another eruption someday, and once again lava and ash will cover Hayden Valley, burying the landscape we know today.
Final eruption students complete the pile.
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| Funding for this trip was provided by Canon U.S.A., Inc., through The Yellowstone Park Foundation. |
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| Web server services are funded through generous grants to The Yellowstone Park Foundation. |
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