The Island Park Caldera
Posted by: 
Volcanoguy
N 44° 11.258 W 111° 19.716
12T E 473737 N 4892765
History sign about the Island Park Caldera in the Upper Mesa Falls area.
Waymark Code: WMC83P
Location: Idaho, United States
Date Posted: 08/06/2011
Views: 4
This history sign along walkways leading to Upper Mesa Falls and deals with the Island Park Caldera.
Marker Name: The Island Park Caldera
Marker Type: Roadside
Marker Text:
The Island Park landscape is a product of volcanic activity that began approximately 2 million years ago. Massive eruptions created what are called calderas -- broad crater-like areas tens of miles across. Three of these calderas were formed at intervals of hundreds of thousands of years, the most recent one about 650,000 years ago near the center of what is now Yellowstone National Park.
The Island Park caldera was created about 1.3 million years ago and is nearly 15 miles wide and ejected approximately 250 times more material into the atmosphere than the 1980 eruption of Mt. Saint Helens. It was the smallest of the three calderas that were part of the creation of the Greater Yellowstone landscape.
How are Calderas formed?
A large chamber of magma from deep within the earth begins to push toward the surface. As it lifts the rock layers above it, a circular series of fractures in the rock is formed around the crest of the dome.
The magma pushes its way up through these fractures, releasing with explosive force the dissolved gases contained in the molten material. As it is blown into the air, the molten material solidifies into hot ash. The lighter ash is carried along by wind over a wide area, while the heavier portions flow down and outward across the landscape, covering thousands of square miles with hundreds of feet of hot volcanic material.
With pressure relieved and considerable magma released to the surface as ash, the rock layers above the magma chamber collapse downward as much as several thousand feet to form a large crater.
The continued rise of the magma chamber pushes up the center of the caldera and molten material erupts through the fractures to fill in the bottom of the crater.
County: Fremont
Group Responsible for Placement: U.S. Forest Service
City: Not listed
Date Dedicated: Not listed
Marker Number: Not listed
Web link(s) for additional information: Not listed
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Visit Instructions:
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