GEOLOGY HAPPENINGS - December 2025

Two of the most popular hiking trails in the Moab area are found along the Potash Road (Highway 279). The two trailheads sit only a third of a mile from one another. Both trails lead to natural arches but offer distinctive hiking experiences that directly result from small nuances of their geology.

The Corona Arch Trail is an approximately 3-mile roundtrip hike to one of the most spectacular natural arches in all of Utah. Corona Arch stands about 105 feet tall and is 140 feet wide.

The Jeep Arch Trail is a bit longer at approximately 3.5-miles roundtrip with more elevation gain. Jeep Arch (alternatively called Gold Bar Arch) is a smaller but still impressive rock opening with a span of about 66 feet.

Both natural arches are in the Navajo Sandstone, one of the most scenic rock layers (formations to geologists) in the Southwest. The Navajo Sandstone was deposited in a massive sand dune field during age of dinosaurs in the Jurassic Period, approximately 185 million years ago. The Navajo Sandstone erodes to form smooth rock domes and cliffs that are usually a light yellow to orange color. This layer has the propensity to erode into natural arches like the two found at the end of these trails.

The trails start in the Kayenta Formation. The Kayenta Formation consists of sandstone layers that are each a few feet thick and were deposited by river systems and in stream channels about 190 million years ago, before the development of the Navajo sand dunes. The environment didn’t change all at once from the Kayenta river systems to the desert dunes of the Navajo, so there is a gradational contact (boundary) between the layers. The fluvial (deposited by flowing water) layers of the Kayenta are easy to differentiate from Navajo eolian (deposited by wind) layers as the former are made up of thin beds that can make natural stone stairways. The Navajo Sandstone is characterized by massive rounded domes that have an subtle internal structure of large swooping layering (cross bedding). The cross bedding formed as sand was deposited along the dune surfaces and as those dunes moved with the wind.

Although the trails start and end in the same layers and despite the fact that they both lead to beautiful natural arches, they offer different journeys. After a steep climb from the trail head, the Corona Arch Trail has a relatively flat surface that is surrounded by soaring domes and cliffs of the Navajo Sandstone. The Corona Arch Trail does have a few very steep sections, including one that requires the use of a steel cable and ladder, but otherwise, it is an easier walk.

In contrast, most of the Jeep Arch Trail provides more of a cardiovascular workout as it consists of a gentle but relentless incline on the way to the arch. This trail also largely stays within the sandstone ledges of the Kayenta Formation and only climbs into the overlying Navajo Sandstone near the end of the trail.

The Kayenta Formation is only around 300 feet thick near the Jeep Arch Trail, yet most of the trail remains in the Kayenta despite climbing 800 feet in elevation. How this occurs is that the rock layers in the area have been slightly tilted from their original horizontal position. (Note that this tilt is a bit more pronounced along the Jeep Arch Trail compared to near the Corona Arch Trail). The Jeep Arch Trail follows a dip slope (e.g., a surface made by a tilted resistant rock layer like the Kayenta). This dip slope is responsible for most of the gradual ascension of the Jeep Arch Trail as well as for the explanation for why the trail remains mostly in the Kayenta despite the elevation gain.

Although rock layers in southeastern Utah are generally flat lying, in some areas, like near Jeep Arch, they have been tilted and/or folded. This tilt creates the dip slope that hikers generally follow to reach Jeep Arch and is what sets this trail apart from some of the others in southeastern Utah and in the overall Four Corners region. For example, hikers climbing in elevation along a trail in an area where the rock layers are still completely horizontal will ascend into younger rock layers as they reach new topographic heights, and descend into older ones as they hike to lower elevations. Grand Canyon in Arizona is a textbook location with such flat-lying layers. Hikers there descend into older rock layers on the hike into the canyon, and then reverse into younger layers on the way back to the rim.

Without the subtle difference in the amount of tilting of rock layers and its orientation in the area right around the Corona and Jeep Arch Trails, these trails would probably offer a much more similar hiking experience than they do. But as it is, one offers soaring rock domes and the other a persistent climb up rocky ledges. But both offer an amazing geologic reward at the end, and plenty of opportunities for geologic appreciation along the way.

A self-described “rock nerd,” Allyson Mathis is a geologist, informal geoscience educator and science writer living in Moab.
To learn more about Moab’s geology, visit the Geology Happenings archive online at https://www.moabhappenings.com/Archives/000archiveindex.htm#geology