Oshima (Hokkaido)

Ōshima

Native name: 大島, Ōshima
Geography
Location	East Asia
Coordinates	41°30′N 139°23′E / 41.500°N 139.383°E / 41.500; 139.383
Archipelago	Japanese archipelago
Area	9.73 km2 (3.76 sq mi)
Width	4 km (2.5 mi)
Highest elevation	732.4 m (2402.9 ft)
Highest point	Mount Era
Administration
Japan
Prefecture	Hokkaido
Subprefecture	Oshima Subprefecture
District	Matsumae District
Town	Matsumae

Ōshima (大島, lit. Big Island) is an uninhabited island in the Sea of Japan, 50 kilometers (31 mi) west of Matsumae town and therefore the westernmost point of Hokkaido. It is part of the town of Matsumae in Oshima Subprefecture in Hokkaido, Japan. To distinguish Ōshima from other islands with the same name, it is sometimes known as Oshima Ōshima (渡島大島) or Matsumae Ōshima (松前大島).

At 9.73 square kilometers (3.76 sq mi), Ōshima is the largest uninhabited island under Japanese sovereignty. The island is a double caldera with a scoria hill rising in the middle. It is the peak of two overlapping stratovolcanoes and their associated calderas, Mount Higashi and Mount Nishi.^[1] The highest peak, Mount Era (江良岳, Era-dake) at 737 meters (2,418 ft),^[2] is part of a triple volcano. The peak rises close to 2,000 meters (6,600 ft) from the sea floor. The island consists of mafic alkali and non-alkali volcanic rock, less than 18,000 years old.^[3]

On the south side of the island at Aidomari (北風泊, Aidomari), there is a lighthouse and a heliport operated by Japan Coast Guard.

Because of volcanic activity and nature conservation, landing on the island requires the approval of the Agency for Cultural Affairs.