Igneous rock the partial melting of rocks within the mantle and crust. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Hence such rocks are smooth, crystalline and fine-grained. Basalt is a common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to form long polygonal columns. The Giant's Causeway in Antrim, Northern Ireland is an example. The molten rock, with
Natural Arch, Tirumala hills pleasant experience. 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)