Ancient Rock at the Road Cut EarthCache
Ancient Rock at the Road Cut
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Rocky Mountain National Park is located west of Estes Park and north and east of Grand Lake. This is a fee area of the National Park Service, and costs $30 per vehicle. This fee is covered in the Rocky Mountain National Park Annual Pass, the Rocky Mountain National Park/Arapaho National Recreation Area Annual Pass, and the America the Beautiful Pass. Please see the following website (visit link) for the entire fee schedule. The park is open 24 hours a day, 365 days a year. Road and Trail Conditions and Closures can be found at: (visit link) Recorded information for the condition of Trail Ridge Road can be found by calling (970) 586-1222. Please remember that all geologic features within the borders of Rocky Mountain National Park are protected by law, as are all natural and historic features. Please do not disturb, damage, or remove any rocks, plants, or animals.
Parking for this EarthCache is at a paved pull off on the west side of the road. Please be cautious of traffic from both directions.
The rocks at this road cut are very old, and at about 1.8 – 2.0 billion years old, are some of the oldest in Rocky Mountain National Park. Biotite schist and gneiss make up the majority of what you can see, along with some veins and lenses of pegmatite.
Schist and gneiss are the types of rocks that result when sedimentary rocks of shale & siltstone (schist) and siltstone and sandstone (gneiss) are subjected to millions of years of extreme pressure and heat. Because they have been changed from their original form, they are called “metamorphic” rocks. Pegmatites are chemically similar to granite, and result when liquid rock is injected into spaces between existing layers of solid rock. Pegmatites at this site are light in color, whereas the schist is darker and shiny, due to the presence of mica.
To log this EarthCache, send me an email with the answers to these questions:
1.) How tall is the road cut at this location?
2.) Are the pegmatite layers at this location younger or older than the schist and gneiss? What is the reason for your answer?
3.) Only if you feel safe doing so, cross the road to the east side. If you do not feel safe crossing the road, or if there is too much traffic, please only answer questions 1 and 2. Examine the schist and tell me if the flakes of mica that you see are large (greater than 0.25 inch across) or small (less than 0.25 inch across).
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:
2004. Rocky Mountain National Park. In Harris, A.G. et al., editors. Geology of National Parks, Sixth Ed. P. 337-356. Dubuque, Iowa: Kendall/Hunt Publishing Company.
Cole, J.C., and Braddock, W.A. 2009. Geologic map of the Estes Park 30’ x 60’ quadrangle, north-central Colorado: U.S. Geological Survey Scientific Investigations Map 3039, 1 sheet, scale 1:100,000, 1 pamphlet, 56 p.
Raup, O.P. 2005. Geology Along Trail Ridge Road. A Self-Guided Tour for Motorists. Estes Park, Colorado: Rocky Mountain Nature Association.
Rocky Mountain National Park. Online at: (visit link)
Rocky Mountain National Park was most helpful in the background discussion, aid in the choosing of sites, and review of this EarthCache. My thanks to the Park for allowing the placement of this EarthCache!
Additional Hints
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