September 02, 2003
The pillars (Hoodoos) shown in this photo are common in Alberta’s Badlands, southeast of Drumheller. They're produced through erosion by water, wind and frost. Hoodoos form where there's a hard “caprock,” which shelters the softer rocks beneath it from erosion. As these softer rocks erode away, a free-standing pillar is formed. Gradually, however, rain will undermine the caprock, and it'll topple over and expose the softer sediments beneath. Without its protective cap, the hoodoo pillar will rapidly disappear.
The hoodoos in this photo show three layers (base, pillar and caprock) that were all deposited during the Upper Cretaceous Period, between 75 and 70 million years ago. The base is red-brown marine shale and the pillar and caprock are sand and clay. The caprock contains nearly 40% calcite cement and is therefore more resistant to erosion than the pillar.