Hank Snyder
Field Report: Devil’s Slide
04/29/14
The Devil’s Slide is a unique geologic formation near Morgan, Utah just south of
Interstate 84. It is comprised of two large walls protruding from the hillside that are aligned
north-south as you can see in the attached map (Google Maps, 2014). I have determined from the
rock sample that I collected from the formation that the two walls are composed of limestone.
The two sedimentary walls were formed by differential erosion on two limestone beds that are a
part of the Jurassic Twin Creek Formation (Chronic, 1990). In the immediate area the limestone
beds were weathered and eroded down over millions of years until only the more resistant
limestone slabs that make up the formation remained. During the middle to late Jurassic Epochs,
the majority of Utah was a shallow basin and the area where the Twin Creek Formation is today
was made up of coastal sand dunes (Willis, 2000). A shallow sea originating from the north then
covered the entire area depositing large amounts of sediment that formed layers of limestone and
sandstone over millions of years. These layers are now referred to as the Twin Creek Formation
and are about 2700 feet thick (Ege, 2003). Evidence of this shallow sea has been found as welldeveloped current ripples have been noted in the limestone near Devil’s Slide. Major thrust
faulting then occurred throughout the state during the late Cretaceous period. This thrust faulting
built up many of the mountain ranges found in Utah today, including the Wasatch Range, the
Rocky Mountains, and the Uinta Range, which is the only range in North America that lies on a
horizontal axis (McDermott, 2005). This same thrusting also folded and overturned the layers of
limestone that made up the Twin Creek Formation to a near vertical position. The middle layers
that were composed of a less resistant shaly limestone were then weathered and eroded away
leaving the formation that we see today. The surrounding hillside appears to be composed of the
same limestone that makes up the formation. As the less resistant limestone in the middle layer
erodes, it slides downhill making a pile of gravel at the base of the formation between the outer
layers. There is a small, private dirt road in front of the formation to the north. The Weber River
flows past the formation merely 15 meters to the North and there is a viewing area just before
Interstate 84, which is just beyond the river. The only human activity in the area are people
fishing in the river itself, sparse use of the private dirt road in front of the formation, and quarries
on the other side of the Interstate that mine the limestone to make cement.
Fig. 1. Satellite view map of the Devil’s Slide Area.
Works Cited
Chronic, Halka (1990). Roadside Geology of Utah. Missoula, Montana. Mountain Press
Publishing Company.
Ege, Carl. Nature’s Version of a Playground Slide-Devil’s Slide, Morgan County, Utah. 2 April
2003. http://www.geology.utah.gov/surveynotes/geosights/devilsslide.htm
Google Maps. 2014. Devil’s Slide Area. Satellite View.
McDermott, Kirk. Formation of the Uinta Mountains. 6 December 2005.
http://legacy.earlham.edu/~mcderki/geo/blah.htm
Willis, Grant. Utah’s Sevier Thrust System. 1 January 2000.
http://geology.utah.gov/utahgeo/geo/thrustfault.htm