Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
Location: Pinnacle at right is at 38o 44' 40" N, 109o 18' 47" W.
The Colorado River flows southwest from Grand Junction, Colorado past Moab, Utah. On the way it passes scenic Castle Valley. The thick resistant Wingate Sandstone forms the cliffs, with the Kayenta Formation forming the ledges on top. The Wingate, though very thick, is actually a soft formation and the cliffs exist because of the protection of the resistant Kayenta Formation. The vertical fluting visible on the pinnacles is due to erosion by rainwater runoff. The horizontal ribs are somewhat more resistant rock layers.
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Created 14 July 2009, Last Update 15 January 2020