Sometimes batholiths arise through several smaller diapiric intrusions (plutons) and have a complex history of magmatic intrusion and crystallization at depths of 5 to 30 kilometers. Batholith formation is commonly associated with lithospheric plate boundaries, where tectonicinteractions between plates are associated with large scale melting of crustal rocks and the formation of deep magma chambers. As erosion uncovers the crystalline rock that formed at great depth, crystal structures respond to the decrease in load and expand, rendering the plutonic rocks susceptible to exfoliative weathering.
Although they may appear uniform, batholiths are in fact structures with complex histories and compositions. They are composed of multiple masses, or plutons, bodies of igneous rock of irregular dimensions (typically at least several kilometers) that can be distinguished from adjacent igneous rock by some combination of criteria including age, composition, texture, or mappable structures. Individual plutons are crystallized from magma that traveled toward the surface from a zone of partial melting near the base of the Earth's crust.
