The main type of rock formed from volcanic activity is called igneous rock. Igneous rocks are created when molten magma or lava cools and solidifies. There are two primary types of igneous rock: intrusive and extrusive. Intrusive igneous rocks, such as granite, form when magma cools slowly beneath the Earth's surface, resulting in larger crystals. Extrusive igneous rocks, like basalt, form when lava cools quickly on the Earth's surface, producing smaller crystals. Overall, igneous rocks play a crucial role in the Earth's geological processes and contribute to the planet's diverse landscape.