Figure 15.9

Landforms created by differential weathering. (A) Devil’s Tower, in Wyoming, is a resistant column of intrusive igneous rock that was once surrounded by sedimentary rock. The less resistant sedimentary rock has been weathered and eroded away, creating this monolith. (B) A natural arch forms, typically in sandstone, when weak joints and bedding planes are eroded fastest. Like all natural arches, this one near Ghayen, Iran, will eventually collapse with further weathering. (C) Hoodoos are tall, columnar rock formations, usually capped with a layer of rock that is resistant to erosion. The resistant cap protects the softer rocks beneath from erosion. These hoodoos are near Drumheller in Alberta, Canada.

(A. © Joel Sartore/National Geographic/Getty Images; B. © Rene Mattes/hemis.fr/Getty Images; C. © Wayne Barrett & Anne MacKay/All Canada Photos/Getty Images)