Bedrock (also termed Bed rock) is a layer of undisturbed rock usually located beneath a surface layer of soil or other material. In areas of high erosion, bedrock may become exposed to the surface. Bedrock can be of igneous, sedimentary, or metamorphic origin and forms the upper surface of the rocky foundation that composes the earth's crust.

A surface exposure of bedrock is called an outcrop. Bedrock is only rarely exposed, or crops out, where sediment accumulates rapidly, for example, in the bottom of stream valleys and at the base of hills or mountains. Outcrops are common where erosion is rapid, for example, along the sides of steep stream channels and on steep hill or mountain slopes. Deserts and mountain tops above the treeline also host good bedrock exposures due to the scarcity of vegetation, and resulting rapid erosion. Man-made outcrops are common where roadways cut through mountains...