Wolford Mountain Thrust Fault EarthCache
Wolford Mountain Thrust Fault
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This EarthCache will take you to a spot near the parking area at the Ritschard Dam, the dam across Muddy Creek which creates the Wolford Reservoir. The object will be an introduction to a characteristic of Wolford Mountain which causes the mountain to be able to be uniquely identified from several miles away.
Wolford Mountain, at 9,163’, has an interesting history behind it that is bound up in the unusual vegetative pattern that you can see here. This vegetative pattern is directly related to the underlying geology of this mountain.
This pattern exists because Wolford Mountain was created by a thrust fault. In a thrust fault, rock from a deeper (and often older) rock formation is “thrust over” the rock from a shallower formation. In this case, billion year old Precambrian granite has been thrust over the much younger, 75 million year old Pierre Shale.
The soils created by the weathering of the granite are able to support trees and larger vegetative types, whereas the decaying shale from the Pierre Shale can only support grasses and low shrubs such as sagebrush. This is the reason that Wolford Mountain looks like it has had a line drawn across it halfway up its slope.
To log this EarthCache, send me an email with the answers to these questions:
1.) Using the information given, and the information from your GPS receiver on your present location, estimate the elevation at which the granite meets the Pierre Shale on Wolford Mountain.
2.) You are presently standing in the area which makes up the Pierre Shale. Looking at the small road cut to the west, you can see the thin rock plates that make up the rock of this formation. With a ruler or measuring tape, measure the thickness of at least 5 of the pieces of shale and send me the average with your email.
Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.
The above information was compiled from the following sources:
1989. Kuntz, D.W., H.J. Armstrong, and F. J. Athearn. Faults, Fossils, and Canyons. Significant Geologic Features on Public Lands in Colorado. Geologic Advisory Group, Bureau of Land Management. Cultural Resource Series, Number 25.
Thanks to the Bureau of Land Management – Kremmling Field Office for allowing placement of this EarthCache!
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