A batholith is a large mass of igneous rock that forms when magma cools and solidifies deep within the Earth's crust. 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 processes that shape the Earth's crust. They are often associated with mountain ranges and can influence local geology and ecosystems. Famous examples of batholiths include the Sierra Nevada Batholith in California and the Coastal Range Batholith in British Columbia.