The Island Park Caldera
Posted by: Groundspeak Premium Member Volcanoguy
N 44° 11.258 W 111° 19.716
12T E 473737 N 4892765
Quick Description: History sign about the Island Park Caldera in the Upper Mesa Falls area.
Location: Idaho, United States
Date Posted: 8/6/2011 9:13:39 PM
Waymark Code: WMC83P
Published By: Groundspeak Premium Member muddawber
Views: 3

Long Description:
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

Visit Instructions:
In your log, please say if you learned something new, and if you took any extra time to explore the area once you stopped at the historic marker waymark. If possible please post a photo of you OR your GPS at the marker location. Also if you know of any additional links not already mentioned about this bit of Idaho history please include that in your log.

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Recent Visits/Logs:
Date Logged Log User Rating  
Volcanoguy visited The Island Park Caldera 9/26/2010 Volcanoguy visited it