Geography of Taiwan and Green Island to the southeast, separated from the northernmost islands of the Philippines by the Bashi Channel. The islands of Kinmen and Matsu near the coast of Fujian across the Taiwan Strait have a total area of ; the Pratas and Taiping islets in the South China Sea are also administered by the ROC, but are not part of the Taiwanese archipelago. 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
Geology of Taiwan Emei Township, Hsinchu County. The second deadliest was a 7.3 quake that ruptured the Chelongpu Fault (車籠埔斷層) on 21 September 1999, known as the "921 earthquake". On 4 March 2010 at about 01:20 UTC, a magnitude 6.4 earthquake hit southern Taiwan. The seismic hazard map for Taiwan by the USGS shows 9/10 of the island as the highest rating (most hazardous). The offshore features include the Kaoping Slope extending off the southwest coast of Taiwan into the South China Sea. This is emerging from the sea over time to extend the island. The Henchung Ridge extends south from the Hengchun