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.
After you have emailed me the answers to these questions, post
at least 1 picture of you with Sentinel Rock in the background.
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!
