A batholith is a large mass of igneous rock that forms when magma cools and solidifies deep beneath the Earth's surface. These formations can cover an area of over 100 square kilometers and are typically composed of granite or similar rocks. Batholiths are often exposed at the surface due to erosion over millions of years. Batholiths are significant in geology because they provide insights into the Earth's crust and the processes that shape it. They can be associated with mountain ranges and are often found in regions with tectonic activity, such as the Sierra Nevada in California or the Andes in South America.