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
Natural Arch, Tirumala hills Natural Arch, Tirumala hills Natural Arch, Tirumala hills, a notified National Geo-heritage Monument, is a distinctive geological feature north of the Tirumala hills temple, near the Chakra Teertham in the state of Andhra Pradesh, India. The arch is also called Silathoranam (శిలాతోరణం) in the local language (Telugu language: "sila" means ‘rock’ and "thoranam" means a garland strung over a threshold, connecting two vertical columns or an ‘arch’ as in this case). The arch measures in width and in height, and is naturally formed in the quartzites of Cuddapah Supergroup of Middle to Upper Proterozoic (1600 to 570 Ma) due to