Batholith is a large body of igneous rock formed beneath the
Earth's surface by the intrusion and solidification of magma. It is commonly
composed of coarse-grained rocks (e.g., granite or quartz diorite) with a
surface exposure of 100 square km (40 square miles) or larger. A batholith has
an irregular shape with side walls that incline steeply against the host rock.
Most batholiths intrude across mountain folds and are elongated along the
dominant axis of the range; faulting and contact metamorphism of the enveloping
rock near the batholith is also observed. Although batholiths were once believed
to extend to unknown depths, recent studies have shown that many of them have a
thickness of perhaps 10 to 15 km (6 to 9 miles). A well-known batholith is
located in the Sierra Nevada range of California, U.S.