Mechanical Weathering and Root Pry

Photographer: Dottie Edwards
Summary Author: Dottie Edwards; Jim Foster

The photo was taken from one of the many unnamed but nonetheless striking slot canyons in the southwestern U.S. This one was discovered while travelling between Bryce Canyon and Zion National Park in Utah. Notice the tree root (perhaps from a pinyon tree) protruding through the sandstone slab. Root pry is one of the methods of mechanical/physical weathering. Tree and plant roots dig deep into small cracks and crevices, and as they grow they pry the rock apart. In mechanical weathering, a rock’s size and shape is changed, but the chemical composition remains the same. Photo taken in August of 2006.