This Plateau in northeastern Arizona rises abruptly above the deeply eroded lowland which is traversed by the Little Colorado River (out of the stereogram at the top). A weekly cemented sandstone forms the rim of the plateau, and it has been weathered ,yielding sand to be drifted by the prevailing southwest wind . U-shaped dunes are formed (C.3-1.9), but sand then extends on as a narrow straight ridge parallel to the wind direction. These are longitudinal dunes which form straight parallel bands in the lower part of the stereogram. On dry plains or plateaus such dunes may extend for many miles until the supply of sand for their growth is used up.