A batholith is a large, intrusive igneous rock mass or rock formation that forms beneath the Earth's surface through the solidification of molten magma. Batholiths are typically composed of granitic or other felsic rocks and can cover large areas, often tens to hundreds of kilometers in diameter. These rock formations are often associated with mountain-building processes and can be found in many geologically active regions around the world. Batholiths are important features in the study of geology, as they provide valuable insights into the processes of magmatism, crustal evolution, and tectonic activity.