Figure 13.9

GEO-GRAPHIC: Exhumation of a batholith, a laccolith, and a dike. Weathering and erosion have removed overlying rocks to expose these intrusive igneous features. (A) The Sierra Nevada mountain range in California is an exhumed batholith. Many kilometers of sedimentary and volcanic rocks once covered the Sierra Nevada. These older rocks were removed by erosion as the batholith was uplifted. (B) Pine Valley Mountain in southern Utah is the one of the largest laccoliths in the United States, measuring about 35 km (20 mi) across. It is an igneous intrusion that formed between layers of sedimentary rock that have since been eroded away. Once the overlying sedimentary rock was removed, erosion by streams cut canyons into the laccolith. (C) Shiprock is a prominent landform found in northwestern New Mexico. A large volcano once existed there. After the volcano became extinct, its outer layers of rock were eroded away, exposing the relatively resistant volcanic neck and the dike.