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
Cave-In-Rock, Illinois Logan Belt Gang terrorized Hardin County in the 1870s and 1880s, until Belt was assassinated. In the middle of the 1800s, church services were being held in the cave. This earliest Christian congregation eventually formed the Big Creek Baptist Church. Founded in 1807, it was the first church organized in southeastern Illinois. Cave-In-Rock incorporated in 1839, in the same year that Hardin County was created from a section of Pope County. According to the Illinois Department of Natural Resources, "in 1929, the State of Illinois acquired for a park that since has increased to . The well-wooded, hills and the