When weathering across a rock face or exposure occurs at different rates mainly due to variations in the composition and resistance of the rock. This results in an uneven surface with the more resistant material protruding
Lynn M. Highland of USGS and Peter Bobrowsky of Geological Survey of Canada, U.S. Department of the Interior, U.S. Geological Survey USGS,Circular 1325, The Landslide Handbook (a Guide to Understanding Landslides), Appendix A: Basic Information about Landslides Landslide, Part 1: Glossary of Landslide Terms, Washington, DC, USA 2013. http://pubs.usgs.gov/circ/1325/pdf/Sections/Append ixA.pdf, (ND/ Lndsld - Amer) {924}