Igneous rock the partial melting of rocks within the mantle and crust. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Hence such rocks are smooth, crystalline and fine-grained. Basalt is a common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to form long polygonal columns. The Giant's Causeway in Antrim, Northern Ireland is an example. The molten rock, with
Little Lava Lake side of Little Lava Lake and leads south into Three Sisters Wilderness and on to Williamson Mountain. Little Lava Lake Little Lava Lake lies in the Cascade Range about west-southwest of Bend in the U.S. state of Oregon. A close neighbor of Lava Lake, from which it is separated by solidified lava, Little Lava Lake is at an elevation of in the Deschutes National Forest. Generally considered the source of the Deschutes River, the lake covers to an average depth of . Lava Lake, Little Lava Lake, and other nearby lakes formed after lava flows from Mount Bachelor altered drainage