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
Crag Cave Crag Cave Crag Cave is a cave in Ireland, located just outside Castleisland, County Kerry. Formed in elevated limestone rock, the system extends to of surveyed passage, on two levels. It is the 7th-longest cave system in the Republic of Ireland, and the 10th-longest in the whole of Ireland. While the Geological Survey of Ireland in 1859 acknowledged the presence of "caves worn by water, some of which can be traversed for some distance," positive efforts at exploration were not made until 1981, when the upper part of the cave was explored to a sump, named the "Green Lake". When