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Ogasawara Islands

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(Redirected from Volcano Islands)

The Ogasawara Islands (小笠原諸島) are an archipelago of over 30 subtropical islands some 1000 km directly south of central Tokyo, Japan. Administratively, they are a part of Tokyo. The islands are also known as the Bonin Islands, and the southernmost (uninhabited) group is known as the Volcano Islands. Still 700 km further south is Okino Torishima, and 1 900 km further east is Minami Torishima. These two remote islands are not geographically, but administratively part of Ogaswara. The total area of the islands is 84 km².

The Ogasawara Islands consists of four subgroups, including the Volcano Islands, which are listed along with their main islands:

  • Mukojima Group (聟島列島 Mukojima Rettō)
    • Mukojima (聟島, literally: Bridegroom Island)
    • Yomejima (嫁島, literally: Bride Island)
    • Kitanojima (北ノ島)
  • Chichijima Group (父島列島 Chichijima Rettō)
    • Chichijima (父島, literally: Father Island),
    • Anijima (兄島, literally: Elder Brother Island)
    • Ototojima (弟島等, literally: Younger Brother Island)
  • Hahajima Group (母島列島 Hahajima Rettō)
    • Hahajima (母島, literally: Mother Island)
    • Anejima (姉島, literally: Elder Sister Island)
    • Imōtojima (妹島, literally: >Younger Sister Island)
  • Volcano Group (火山列島 Kazan Rettō)
    • Kita Iōjima (北硫黄島 Kitaiōjima, literally: North Sulphur Island)
    • Iōjima (硫黄島 Iōjima, literally: Sulphur Island)
    • Minami Iōjima (南硫黄島 Minamiiōjima, literally: South Sulphur Island)
  • Single Isolated Island, west of Hahajima Group and North of Volcano Group:
    • Nishino shima (西之島, literally: Western Island, also: Rosario Island)
  • Isolated Remote Islands, not geographically but administratively part of Ogaswara Islands

The only inhabited islands are Chichi-jima (父島) and Haha-jima (母島). Sugar Cane, Pineapples and Bananas are grown on the islands. From the forests, valuable woods from sugi, beech, box tree, rosewood and sandalwood trees are exported. Access to these islands is possible only via a single weekly overnight ferry from Tokyo, although there are plans to open an airport. Tourists are attracted to the islands by scuba diving and whale watching.

The uninhabited Iō-jima (硫黄島), better known in English as Iwo Jima, is a part of the Volcano Islands. Access to the island requires special permission.

Contents

Geology

The Ogaswara islands are a part of island arc know as the fore arc. They lie above a subduction zone between the Pacific Plate and the Philippine Plate. The Pacific Plate is subducting under the Philippine Plate, which creates an oceanic trench to the east of the islands. The crust of the Bonin islands were formed by volcanic activity when subuduction began about 45=50 million years ago, and are composed mostly of an andesitic volcanic rock called Boninite, which is rich in magnesium oxide, chromium, and silicon dioxide. The Bonin Islands may represent the exposed parts of an ophiolite that has not yet been emplaced on oceanic crust. The rocks of the Volcano Islands are much younger; Iwo Jima is a dormant volcano characerized by rapid uplift and several hot springs. The Battle of Iwo Jima, one of the fiercest battles of World War II, was fought here in 1945.

Most of the islands have steep shorelines, often with sea cliffs ranging from 50 to 100 meters in height. Several of the islands are fringed with coral reefs.

History

The first recorded settlement of the islands was an American colony founded in 1830, which persisted until the Second World War. Japan has ruled the islands since 1875.

Ogasawara subtropical moist forests

The Ogasawara Islands form a distinct subtropical moist broadleaf forest ecoregion, with a high degree of biodiversity and endemism. The islands are home to about 500 plant species, of which 43% are endemic. The forests are of three main types:

  • Type I: Elaeocarpus-Ardisia mesic forest is found in the moist lowland areas with deep soils. The forests have a closed canopy with a height of about 15 meters, dominated by Ardisia sieboldii. Elaeocarpus photiniaefolius, Pisonia umbellifera, and Pouteria obovata are other important canopy species. These forests were almost completely destroyed by clearing for agriculture before 1945.
  • Type II: Distylium-Raphiolepis-Schima dry forest is found in drier lowland and upland sites with shallower soils. It is also a closed-canopy forest, with a 4 to 8 meter canopy comprised mostly of Distylium lepidotum, Rhaphiolepis integerrima, Schima mertensiana, Pouteria obovata, and Syzygium buxifolium. The Type II forests can be further subdivided into:
    • Type IIa: Distylium-Schima dry forest occurs in cloudy upland areas with fine-textured soils. These forests contain many rare and endemic species, with Pandanus boninensis and Syzygium buxifolium as the predominant trees.
    • Type IIb: Raphiolepsis-Livistona dry forest is found in upland areas with few clouds and rocky soils. Rhaphiolepis integerrima is the dominant tree species, along with the fan palm Livistona chinensis var. bonensis, Pandanus boninensis and Ochrosia nakaiana.
  • Type III: Distylium-Pouteria scrub forest is found on windy and dry mountain ridges and exposed sea cliffs. These forests have the highest species diversity on the islands. Distylium lepidotum and Pouteria obovata are the dominant species, growing from .5 to 1.5 meters tall. Other common shrubs are Myrsine okabeana, Symplocos kawakamii, and Pittosporum parvifolium.

Two bird species are endemic to the islands, the Japanese wood-pigeon (Columba janthina) and the Vulnerable Bonin honeyeater (Apalopteron familiare).

External links

Template:Tokyode:Ogasawara-Inseln et:Ogasawara saared ja:小笠原諸島

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