Henrys Fork Caldera
Posted by: Groundspeak Premium Member Volcanoguy
N 44° 19.827 W 111° 26.358
12T E 464975 N 4908670
Quick Description: Sign about the geologic history of the Henrys Fork Caldera.
Location: Idaho, United States
Date Posted: 8/9/2011 1:04:10 PM
Waymark Code: WMC8TM
Published By: Groundspeak Premium Member muddawber
Views: 1

Long Description:
This history sign is one of four signs at the Mesa Falls Scenic Byway information site at the north end of the byway near the junction of F.S. Route 294 and U.S. Hwy. 20.
Marker Name: Henrys Fork Caldera

Marker Type: Roadside

Marker Text:
Ground Zero of an Epic Explosion You are standing at the site of one of the largest volcanic explosions in geologic history. The explosion of the Yellowstone Super Volcano, 1.2 million years ago, created the Henrys Fork Caldera. Look to your left. The curving ridgeline you see to the southwest forms a portion of the Henrys Fork Caldera -- the remains of a volcano that exploded and collapsed into itself. The blast ejected 67 cubic miles of molten rock into the sky -- Mount St. Helens, during 1980, ejected 1/4 cubic mile. The blast buried Eastern Idaho in ash up to 1,000 feet thick -- briefly obliterating all life for hundreds of square miles. Geologist believe that the caldera is a result of the Yellowstone Super Volcano -- a deep thermal mantle plume of molten rock presently below Yellowstone. Evidence of the super volcano’s track across Southern Idaho is visible as volcanism, faulting, and uplift that resulted during the past 16 million years when the North American Continental Plate passed over the mantle plume. Earthquake activity beneath Yellowstone National Park indicates that the mantle plume is still active today. Another eruption of the Yellowstone Super Volcano would plunge the Earth into darkness -- altering global climate for many years.


County: Fremont

Group Responsible for Placement: Mesa Falls Scenic Byway

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 Henrys Fork Caldera 9/24/2010 Volcanoguy visited it