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
Fingal's Cave the name as Fingal (meaning "white stranger") through a misapprehension of the name which in old Gaelic would appear as Finn. The legend of the Giant's Causeway has Fionn or Finn building the causeway between Ireland and Scotland. The cave has a large arched entrance and is filled by the sea. Several sightseeing cruises organised from April to September by local companies pass the entrance to the cave. In calm conditions, one can land at the island's landing place (as some of these cruises permit) and walk the short distance to the cave, where a row of fractured columns forms