Taiwan, officially the Republic of China (ROC), is a country in East Asia. The island of Taiwan, formerly known to Westerners as Formosa, has an area of 35,808 square kilometres (13,826 sq mi) and makes up 99% of the land under ROC control. It lies about 180 kilometres (112 mi) across the Taiwan Strait from the southeastern coast of the Mainland China. The East China Sea is to the north of the island, the Philippine Sea to its east, the Luzon Strait directly to its south, and the South China Sea to its southwest. The ROC also controls a number of smaller islands, including the Penghu archipelago in the Taiwan Strait, Kinmen and Matsu in Fuchien near the Mainland coast, as well as Pratas and Taiping in the South China Sea.
Geologically, the main island comprises a tilted fault block, characterized by the contrast between the eastern two-thirds, consisting mostly of five rugged mountain ranges running parallel to the east coast, and the flat to gently rolling plains of the western third, where the majority of the population resides. Several peaks exceed 3,500 m in height – the highest, Yu Shan at 3,952 m (12,966 ft), makes Taiwan the world's fourth-highest island. The tectonic boundary that formed these ranges remains active, and the island experiences many earthquakes, some of them highly destructive. There are also many active submarine volcanoes in the Taiwan Straits.
