The type of rock formed from cooling lava is called igneous rock. When lava erupts from a volcano and cools, it solidifies into igneous rock either above ground (as volcanic rock) or below ground (as intrusive rock). Examples of igneous rock include basalt, which forms from rapidly cooled lava, and granite, which occurs when magma cools slowly beneath the Earth's surface. Igneous rocks are significant in geology because they provide information about the Earth’s structure and the processes that shape it, including volcanic activity and plate tectonics.