Igneous complexes are large geological formations created by the solidification of molten rock, or magma, beneath the Earth's surface. They can consist of various types of igneous rocks, which are classified based on their mineral composition and texture. These complexes often form when magma accumulates in large chambers and cools slowly, resulting in the formation of coarse-grained rocks like granite. These complexes can also be associated with volcanic activity, where magma erupts to the surface, creating volcanic rocks like basalt. The study of igneous complexes helps geologists understand the processes that shape the Earth's crust and the formation of different rock types over geological time.