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The Moab Fault: Arches National Park

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Hidden : 11/17/2006
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Geocache Description:

If you go to Arches National Park you’ll first visit the Moab Fault ... You can’t help it - you’re in it! Highway 191 follows the Fault for much of its extent. There is a stunning panoramic view of it at the first turnout after you leave the visitors’ center and drive into the park.

View from the Turnout

The Moab Fault is a nearly vertical, normal fault (see links below) in the Paradox Basin of southeastern Utah. Geologists believe it occurred as the result of the dissolution-migration of subterranean salts (the Paradox evaporites) laid down by inland seas during the Pennsylvanian Epoch, ~300 million years ago (Mya).

Complex "fractal" faulting in the Hwy. 191 Roadcut


1. To see in your mind's eye the earth movement that created the Moab Fault;

2. To identify the major geological layers (strata) exposed in the region.

Directions: Enter Arches NP north of Moab from Highway 191. Follow the switchbacks to the first turnout at the posted coordinates. Be sure to read the colorful descriptive plaque.

Supplies: Stop at the Visitors Center and pick up a free pamphlet that identifies the different rock strata. You will refer to it as you tour the Park and nearby attractions.

As you search for answers to the Study Questions, use Wikipedia or Google for a starter; put quotation marks around compound phrases, such as "hanging wall".

Educational Requirement: To get credit for this EarthCache you must email us your answer to any one of the Study Questions and let us know how many people were in your party.


The Study Questions are arranged by our adaptation of the Asimov ratings. Isaac Asimov wrote quizzes for daily newspapers over many years. The difficulty of the questions was classified as "Freshman", "Graduate" or "Ph.D."

1) AP College-Bound. Are the nearly vertical red cliffs on the west side of the highway the same formation as those to the east (in Arches NP)? If not, why not? Has some rock "gone missing" ? Where do you suppose it went?

2) Freshman. Look at this Earthcache on Google Maps; bring up Satellite and Hybrid views and find Arches NP. Can you identify the Moab Fault? How do you know it's a fault?

3) Freshman. Why are some of the rock layers nearly vertical, while others form slopes?

4) Graduate. Name some of the features that help one distinguish one layer/formation from another.

5) Graduate. What is a “normal” fault? Did Arches go up or did it go down? Kinds of Faults Also, check out the Animation under Links and Resources below.


6) Ph. D. Are you standing on the hanging wall or the foot wall? Kinds of Faults

7) Ph.D. Assuming that you are standing on the Navajo formation and that you are eye-level with the bottom of the Wingate formation across Hwy. 191, how far would you estimate one side of the fault moved relative to the other?

Links and Resources:

What are those strata? The NPS page that showed the strata is under review. This older figure is rich in information but hard to read.

Robert J. Lillie. Parks and Plates. The Geology of our National Parks, Monuments and Seashores. WW Norton, New York, 2005. Publisher's Advertisement

An animated explanation of geological faulting. View Animation

Additional Hints (Decrypt)

Lbh zvtug jnag gb gnxr n fancfubg bs gur fvtantr ng gur ghea-bhg sbe yngre ersrerapr. ;-)

Decryption Key


(letter above equals below, and vice versa)

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