Forming a Pinnacle

The Dillon Pinnacles are among many spires within Curecanti formed by erosion as wind, rain, and ice carve the landscape. Their shape results from differences in rock hardness: weaker underlying rock wears away rapidly, while more resistant tuff forms a cap on top. This cap rock protects some of the rock directly beneath it as surrounding rocks erode, leaving a spire or pinnacle. Over time, the tuff cap on a pinnacle also erodes, as shown by many pinnacles here that no longer have a cap. West Elk Breccia is a soft rock composed of ash and volcanic rock chunks, and Blue Mesa Tuff is a hard rock that serves as a cap.

Colorado · United States