Figure 18.16
GEO-GRAPHIC: Formation of mesas and buttes. (A) Mesa-and-butte terrain forms as a plateau consisting of sedimentary rock is eroded. (B) In Monument Valley, on the Colorado Plateau in northern Arizona and southern Utah, buttes and chimneys form as slabs of sandstone shear off along vertical joints and accumulate as talus on the slopes. The gentle slope at the base of the butte is composed of relatively soft shale that is too weak to develop a vertical cliff face. Where talus accumulates along the length of a mesa or linear escarpment, a talus apron results.(B. © Guido Alberto Rossi/Age Fotostock, Inc.)