Igneous rocks form from the cooling of molten rock or magma. There are two types of cooling that produce different igneous rocks: rapid cooling leads to volcanic rocks like obsidian near the surface, while slow cooling deep underground forms plutonic rocks like granite. Volcanic rocks include obsidian, lava, basalt, and pumice, which cool quickly above ground, whereas plutonic rocks such as granite, syenite, and pink granite form from slow cooling underground.