Orchid Island, known as Pongso no Tao by the indigenous inhabitants, is a 45 km (17 sq mi) volcanic island located off the southeastern coast of Taiwan. The island and the nearby Lesser Orchid Island are governed by Taiwan as Lanyu Township in Taitung County, which is one of the county's two insular townships (the other being Lyudao Township). It is separated from the Batanes of the Philippines by the Bashi Channel of the Luzon Strait.
It is considered a potential World Heritage Site.
The Bashi Channel (Chinese: 巴士海峽; pinyin: Bā shì hǎi xiá, Filipino: Tsanel ng Bashi, Kipot ng Bashi) is a waterway between Mavulis Island of the Batanes Islands, Philippines and Orchid Island of Taiwan. It is a part of the Luzon Strait, with the Pacific Ocean to the east, and is between the East China Sea and the South China Sea. It is characterized by windy storms during the rainy period, which lasts from June to December.
Taiwan Province (Chinese: 臺灣省; pinyin: Táiwān Shěng; Pe̍h-ōe-jī: Tâi-oân-séng; PFS: Thòi-vàn-sén or Thòi-vân-sén) is a de jure administrative division of the Republic of China (Taiwan). Provinces remain a titular division as a part of the Constitution of the Republic of China, but are no longer considered to have any administrative function practically.
Taiwan Province covers approximately 69% of the island of Taiwan, and comprises around 31% of the total population. The province initially covered the entire island of Taiwan (Formosa), Penghu (the Pescadores), Orchid Island, Green Island, Xiaoliuqiu Island, and their surrounding islands. Between 1967 and 2014, six special municipalities (Kaohsiung, New Taipei, Taichung, Tainan, Taipei and Taoyuan) were split off from the province, all in the most populous regions.
Green Island, also known by other names, is a small volcanic island in the Pacific Ocean about 33 km (21 mi) off the eastern coast of the main island of Taiwan. It is 15.092 km (5.83 sq mi) at high tide and 17.329 km (6.69 sq mi) at low tide, making it the seventh-largest island in Taiwan. The island is administered as Lyudao Township, a rural township of Taitung County and one of the county's two insular townships (the other being Lanyu Township). The island once served as a penal colony for political prisoners during Taiwan's period of martial law, although today it is primarily known as a tourist hotspot.
The Luzon Volcanic Arc is a chain of volcanoes in a north–south line across the Luzon Strait from Taiwan to Luzon. The name "Luzon Volcanic Arc" was first proposed by Carl Bowin et al. to describe a series of Miocene to recent volcanoes due to eastward subduction along the Manila Trench for approximately 1,200 km from the Coastal Range in Taiwan south to southern Mindoro in the Philippines. Islands that form part of the arc are the Eastern Coastal Range of Taiwan, Green Island, Taiwan, Orchid Island, Kaotai Rock, Mavudis or Y'ami Island, Mabudis, Siayan Island, Itbayat Island, Diogo Island, Batan Island, Unnamed volcano Ibuhos, Sabtang Island, Babuyan, Didicas, and Camiguin de Babuyanes. At the south end it terminates on Luzon. The geochemistry of a number of volcanoes along the arc have been measured. There are five distinct geochemical domains within the arc (Mindoro, Bataan, Northern Luzon, Babuyan, and Taiwan). The geochemistry of the segments verified that the volcanoes are all subduction related (e.g., strong niobium anomalies and calc-alkaline characteristics). Isotopes and trace elements show unique geochemical characteristics in the north. Geochemical variations northward (Babuyan segment) were due to the subduction of sediments derived from the erosion of continental crust from China and Taiwan.
There is a distinct increase in strontium isotopic ratios with latitude northward. This supports the conjecture that the variations were due to an increasing "crustal" component in subducted sediments as the continental blocks in the north were approached (China and Taiwan). The sediment thicknesses increased toward the north along the trench.