Batholiths are large dome-shaped intrusive bodies of igneous rock that form deep within the Earth's crust. They are composed of a variety of rock types, including granite, granodiorite, and diorite. Batholiths are characterized by their massive size, often covering hundreds of square kilometers.

Formation of Batholiths:

1. Intrusion: Batholiths are formed when large volumes of magma are injected into the Earth's crust. This magma is generated through the melting of pre-existing rocks in the lower crust and upper mantle.

2. Cooling and Solidification: Once the magma is injected into the crust, it begins to cool and solidify over a long period of time. The cooling process is slow due to the large size of batholiths and the insulating properties of surrounding rocks.

Characteristics of Batholiths:

1. Dome-shaped: Batholiths typically have a rounded or dome-shaped appearance due to the slow cooling and solidification process. The magma intrudes into the crust and forms a large, bulging mass of rock.

2. Intrusive: Batholiths are intrusive igneous features, meaning that they form within the Earth's crust rather than on the surface. This is in contrast to extrusive igneous features, such as volcanoes, which form when magma erupts onto the surface.

3. Composition: Batholiths are primarily composed of coarse-grained rocks, such as granite, which contain large crystals that formed as the magma slowly cooled. The composition of batholiths can vary depending on the source of the magma and the surrounding rocks.

4. Size: Batholiths are some of the largest intrusive features on Earth, often spanning hundreds of square kilometers. They are typically much larger than other intrusive features, such as dikes or sills.

Importance of Batholiths:

1. Economic Significance: Batholiths often contain valuable mineral deposits, such as gold, copper, and molybdenum. These minerals can be extracted through mining, providing important economic resources.

2. Landforms: Batholiths can influence the landscape by uplifting and exposing the overlying rocks. They can create mountain ranges, ridges, and other prominent landforms.

In conclusion, batholiths are large dome-shaped intrusive bodies of igneous rock that form deep within the Earth's crust. They are characterized by their massive size, dome-shaped appearance, and coarse-grained composition. Batholiths play a significant role in shaping the Earth's surface and can contain valuable mineral resources.