Garden of the Gods - Sentinel Rock EarthCache
Garden of the Gods - Sentinel Rock
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This EarthCache is located in Garden of the Gods Park, a Colorado Springs City Park. Park hours are as follows: May 1 – October 31, 5 am – 11 pm; November 1 – April 30, 5 am – 9 pm. There is no charge for entry into the park.
Sentinel Rock is composed of two of the rock formations which are found in the central part of the park: Fountain Arkose and Lyons Sandstone.
Fountain Arkose, found primarily on the west side of Sentinel Rock, is a conglomerate made up of coarse-grained sediments. An arkose is a rock formed from at least 25% feldspar, and the Fountain Arkose is composed of stream sediments which were deposited as gravels from the erosion of the Ancestral Rocky Mountains millions of years ago. Other rock formations found in the park which are composed of Fountain Arkose include Cathedral Spires, the Three Graces, and the Siamese Twins.
Lyons Sandstone, on the east side, is a quartz sandstone that is the remnant of a field of ancient sand dunes. Over time, the dunes were buried, compacted, and lithified (turned to rock). Ripple marks can be seen in the sandstone, as can cross-bedding which was caused by wind action on the dunes. North Gateway Rock, South Gateway Rock, White Rock, and the Sleeping Giant are all made of Lyons Sandstone. Different colors in these formations are caused by different amounts of iron oxide present in the rocks.
To log this EarthCache, send me an email with the answers to the following: 1.) How long ago were the layers deposited? 2.) Compare the particle size of the Fountain Arkose and the Lyons Sandstone. Which has the larger particles? 3.) Name at least one other way in which the Fountain Arkose and Lyons Sandstone are different.
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:
Interpretive Sign at Site.
Colorado Springs City Webpage: Garden of the Gods Park. (visit link)
Colorado Springs City Webpage: Important Events in Garden of the Gods Geology. (visit link)
2007. Chronic H., and F. Williams. Roadside Geology of Colorado, 2nd Ed.
2004. Hopkins, R.L., and L.B. Hopkins. Hiking Colorado’s Geology
Thanks to the City of Colorado Springs and the Parks, Recreation & Cultural Services Department for allowing placement of this EarthCache!
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