The Geology Behind Hoodos

by Aliyah Schneider, Geology student at California Lutheran University

IMG_9583

Bryce Canyon national park is in Ebenzer Bryce’s own words, “One hell of a place to find a cow.” You might be asking yourself, how then do these unique formations we see called Hoodo’s and Goblins form? Lets go back a few million years, 80 to be exact. During this period in time called the Eocene, the landscape looked incredibly different. It was not yet uplifted and there were no Hoodo’s in sight. Actually this area of what was soon to become the state of Utah was a series of transgressing and regressing fresh water lakes. Can you picture it? Called the Claron lake system, it is this unique environment that eventually led to the formation of these funky spires we see today. See when there is warm shallow water we get limestone, and when there is a beach at the lake we get sandstone. So what happens when the water level rises and falls?

Limestone
Shale
Sandstone
Shale
Limestone
Shale
Sandstone
Shale……..

And so on and so on, deposited perfectly flat, right on top of each other.  After about 10 million more years these rocks were uplifted by another orogenic ( mountain building ) event. As a result of the expansion in the rocks they joint perfectly at 60°/ 120°. Normally this would just create spires, like the ones we see out at monument valley. But because of the unique layering of the rocks at Bryce, we end up with Hoodoo’s. Shale is soft mud, while sandstone and limestone have much stronger cements keeping them together. As the shale erodes more quickly and the SS and LS remain the resulting rocks have inward and outward curvatures. These have been fondly named hoodoos and I think it’s safe to say that Bryce canyon would be a terrible place to lose a cow.

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