Topography of Taiwan - Geology

Geology

Main article: Geology of Taiwan See also: Taiwanese hot springs and List of volcanoes in Taiwan

The island of Taiwan was formed approximately 4 to 5 million years ago at a complex convergent boundary between the Philippine Sea Plate and the Eurasian Plate. In a boundary running the length of the island and continuing southwards in the Luzon Volcanic Arc (including Green Island and Orchid Island), the Eurasian Plate is sliding under the Philippine Sea Plate.

Most of the island comprises a huge fault block tilted to the west. The western part of the island, and much of the central range, consists of sedimentary deposits scraped from the descending edge of the Eurasian Plate. In the northeast of the island, and continuing eastwards in the Ryukyu Volcanic Arc, the Philippine Sea Plate slides under the Eurasian Plate.

The tectonic boundary remains active, and Taiwan experiences 15,000 to 18,000 earthquakes each year, of which 800 to 1,000 are noticed by people. The most catastrophic recent earthquake was the magnitude-7.3 Chi-Chi earthquake, which occurred in the center of Taiwan on 21 September 1999, killing more than 2,400 people. On 4 March 2010 at about 01:20 UTC, a magnitude 6.4 earthquake hit southwestern Taiwan in the mountainous area of Kaohsiung County.