Giant's Causeway cases the horizontal fracture has resulted in a bottom face that is convex while the upper face of the lower segment is concave, producing what are called "ball and socket" joints. The size of the columns is primarily determined by the speed at which lava from a volcanic eruption cools. The extensive fracture network produced the distinctive columns seen today. The basalts were originally part of a great volcanic plateau called the Thulean Plateau which formed during the Paleocene. According to legend, the columns are the remains of a causeway built by a giant. The story goes that the Irish
Cave-In-Rock, Illinois 43.8% of those under age 18 and 24.1% of those age 65 or over. Cave-in-Rock's primary feature is a striking riverside cave formed by wind and water erosion and by cataclysmic effects of the 1811–12 New Madrid earthquakes. The cave is located at , just upriver (east) from the village. The first European to come across it was M. de Lery of France, who found it in 1739 and called it ""caverne dans Le Roc"". Other names for the cave include Rock-In-Cave, Rocking Cave, Rock-and-Cave, House of Nature, The Cave, Big Cave, and Murrell's Cave. The cave is the main