(means "big island") is an uninhabited island in the

Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, i ...

, to the west from Matsumae town and therefore the westernmost point of

Hokkaido is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The lar ...

. It is part of the town of Matsumae in

Oshima Subprefecture is a Subprefectures of Hokkaido, subprefecture of Hokkaido, Hokkaido Prefecture, Japan. As of 2004 it had a population of 456,621 and an area of 3,715.38 km2. Hakodate Airport is located in the City of Hakodate, Hokkaido, Hakodate. Ge ...

in Hokkaido, Japan. To distinguish Ōshima from other islands with the same name, it is sometimes known as or . At , Ōshima is the largest uninhabited island under Japanese sovereignty. The island is a double caldera with a

scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) '' ...

hill rising in the middle. It is the peak of two overlapping stratovolcanoes and their associated calderas, Mount Higashi and Mount Nishi. The highest peak, at , is part of a triple volcano. The peak rises close to from the sea floor. The island consists of mafic alkali and non-alkali volcanic rock, less than 18,000 years old. On the south side of the island at , there is a lighthouse and a heliport operated by

Japan Coast Guard The is the coast guard of Japan. The Japan Coast Guard consists of about 13,700 personnel and is responsible for the protection of the coastline of Japan under the oversight of the Ministry of Land, Infrastructure, Transport and Tourism. Th ...

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

History

Because of the island's isolation and volcanic activity there are almost no records of its past left behind. had a major eruption on 27 August 1741, which created a large horseshoe-shaped caldera breached to the north and extending from the summit down to the sea floor at the base of the

volcano A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...

. This event produced a mostly submarine debris avalanche that traveled 16 km distance, and triggered a large tsunami. The

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

devastated the coasts of

, western

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island se ...

, and as far as

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

, causing nearly 1500 deaths. The 1741 eruption was the largest in historical time at Ōshima and it ended with the construction of a basaltic cinder cone at the head of the breached caldera. No eruptions have occurred since the last eruption in 1790, but seismic unrest under the volcano occurred in 1996.

Flora and fauna

Ōshima is the northern limit of the breeding grounds for the

streaked shearwater The streaked shearwater (''Calonectris leucomelas'') is a species of seabird. The adult bird averages in length, with a wingspan. Description The streaked shearwater feeds mainly on fish and squid. It follows fishing boats, attracted to anch ...

and is part of the Matsumae-Yakoshi Prefectural Natural Park.

Baird's beaked whale Baird's beaked whale (''Berardius bairdii''), also known as the northern giant bottlenose whale, North Pacific bottlenose whale, giant four-toothed whale, northern four-toothed whale and the North Pacific four-toothed whale, is a species of whale ...

s are targets of commercial whaling in the nearby waters.Kasuya T.( jp). 2017
Small Cetaceans of Japan: Exploitation and Biology
"13.3.2 Regional distribution and population structure". CRC Press. Retrieved on September 25, 2017

References

Sources

* Based on the translation of :ja:渡島大島 on 12 December 2008 {{DEFAULTSORT:Oshima, Hokkaido Islands of the Sea of Japan Islands of Hokkaido Uninhabited islands of Japan Matsumae, Hokkaido Stratovolcanoes of Japan Calderas of Japan

History

Flora and fauna

See also

References

Sources