Giant’s Causeway is an unusual formation of rock columns along the north coast of Northern Ireland. It gets its name from an old legend that the causeway was built by Finn MacCool, or Fingal, to bridge the channel from Ireland to Scotland so that giants could pass over it. The causeway is formed of about 40,000 separate basalt columns, quite close together. Some pillars are up to 20 feet (6 meters) high. They are from 15 to 20 inches (38 to 51 centimeters) in diameter. Geologists believe the causeway resulted from the contracting of a lava flow. See also Basalt .