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 of the Crystals Cave of the Crystals Cave of the Crystals or Giant Crystal Cave () is a cave connected to the Naica Mine at a depth of , in Naica, Chihuahua, Mexico. The main chamber contains giant selenite crystals (gypsum, CaSO·2 HO), some of the largest natural crystals ever found. The cave's largest crystal found to date is in length, in diameter and 55 tons in weight. When it was accessible, the cave was extremely hot, with air temperatures reaching up to with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors. Without proper protection, people could