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, it ...
, west of
Matsumae town and therefore the westernmost point of
Hokkaido
is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...
. It is part of the town of Matsumae in
Oshima Subprefecture in Hokkaido,
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
. 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
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
with a
scoria hill rising in the middle. It is the peak of two overlapping
stratovolcano
A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
es 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.
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 seafloor at the base of the
volcano
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most oft ...
. This event produced a mostly-submarine debris avalanche that traveled 16 km and triggered a large tsunami, which devastated the coasts of
Hokkaido
is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...
, western
Honshu
, historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...
, and
Korea
Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...
, causing nearly 1500 deaths. The 1741 eruption was the largest in historical times at Ōshima and ended with the construction of a basaltic
cinder cone
A cinder cone or scoria cone is a steep, volcanic cone, conical landform of loose pyroclastic rock, pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are forme ...
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 and is part of the
Matsumae-Yakoshi Prefectural Natural Park.
Baird's beaked whales 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
The CRC Press, LLC is an American publishing group that specializes in producing technical books. Many of their books relate to engineering, science and mathematics. Their scope also includes books on business, forensics and information technol ...
. Retrieved on September 25, 2017
See also
*
Desert island
An uninhabited island, desert island, or deserted island, is an island, islet or atoll which lacks permanent human population. Uninhabited islands are often depicted in films or stories about shipwrecked people, and are also used as stereotypes ...
*
List of islands
This is a list of the lists of islands in the world grouped by country, by continent, by body of water
A body of water or waterbody is any significant accumulation of water on the surface of Earth or another planet. The term most often refer ...
*
List of volcanoes in Japan
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