Igneous rock that cools on the surface of the Earth, including beneath water; typically with small crystals due to rapid cooling Also known as volcanic; opposite of intrusive or plutonic
rock or volcanic rock ligneous rock formed on the surface of the Earth; for example, basalt
Any igneous rock derived from magma that is poured out or ejected at the Earth's surface. Extrusive rocks are usually distinguished from intrusive rocks on the basis of their texture and mineral composition. Lava flows and pyroclastic debris (fragmented volcanic material) are extrusive; they are commonly glassy (e.g., obsidian) or finely crystalline (e.g., basalts and felsites)