Osumi Peninsula - Osumihanto

A peninsula that juts out south from the eastern part of Kagoshima Prefecture, at the southeastern tip of Kyushu. Its southernmost point, Cape Sata, is located at approximately 31 degrees north latitude. Facing the Satsuma Peninsula to the west, it contains Kagoshima Bay (Kinko Bay), which is about 10 kilometers wide at its narrowest point and about 70 kilometers deep at its innermost part. Sakurajima is located near the inner part of the bay. Sakurajima became connected to the Osumi Peninsula by lava flows from a major eruption in 1914 (Taisho 3). The eastern side of the peninsula opens into Shibushi Bay (Ariake Bay). On the west side, with the exception of a small area, the Takakuma Mountains (1,000-1,300 meters) and the Shirasu Plateau approach the bay, and at the southern tip of the peninsula, there is the Kimotsuki Mountains, which run northeast-southwest from Shibushi Bay to the mouth of Kagoshima Bay, and are nearly 1,000 meters high. As a result, the entire large river system flows into Shibushi Bay. The Wanizuka Mountains also extend from the northern part of Shibushi Bay. Surrounded by these mountains, the Shirasu Plateau, 100-200 meters high, and the hills that have been dissected from it are widely distributed. The administrative district consists of the four cities of Soo, Shibushi, Kanoya, and Tarumizu, the four towns of Higashikushira, Kinko, Minamiosumi, and Kimotsuki in Kimotsuki County, and Osaki Town in Soo County. The main river systems include the Kimotsuki River, the Hishida River, the Anraku River, etc. These rivers cut deep into the Shirasu plateaus such as Kasanohara, but except for the lower reaches of the Kimotsuki River, the alluvial lowlands are not very large.

In recent years, irrigation facilities have been installed in Kasanohara, and the cultivation of sweet potatoes, rapeseed, etc. is being switched over to a variety of fruit trees and horticultural crops. Paddy field cultivation is the main practice in the alluvial lowlands. The Kimotsuki Mountains are the Osumi Natural Recreation Forest, Sakurajima and Sata Cape are Kirishima-Kinkowan National Park, and the coast of Shibushi Bay is Nichinan Coast Quasi-National Park. These areas are dominated by subtropical vegetation (cycads, tree staghorns, Japanese fan palms, etc.) and other rich natural scenery.

[Kimihiko Tsukada]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

九州の南東端、鹿児島県の東部から南に向かって突き出た半島。この最南端、佐多(さた)岬は北緯31度付近にあたる。西にある薩摩半島(さつまはんとう)と相対し、湾口の最狭部幅約10キロメートル、湾奥まで約70キロメートルの鹿児島湾（錦江湾(きんこうわん)）を擁する。湾奥近くに桜島がある。桜島は1914年（大正3）の大噴火による溶岩流で大隅半島と陸続きとなった。半島東側は志布志湾(しぶしわん)（有明湾(ありあけわん)）に開ける。西側はごく一部を除き高隈山地(たかくまさんち)（1000～1300メートル）や、シラス台地が湾に迫り、半島南端部にも志布志湾から鹿児島湾口へ北東～南西走向の1000メートルに近い肝属山地(きもつきさんち)がある。このため大水系はすべて志布志湾へと注ぐ。また志布志湾北部からは鰐塚山地(わにつかさんち)が張り出す。これらの山地に取り囲まれて、100～200メートルのシラス台地およびそれが開析された丘陵地が広く分布する。行政区は曽於(そお)、志布志、鹿屋(かのや)、垂水(たるみず)の4市、肝属郡東串良(ひがしくしら)、錦江、南大隅、肝付(きもつき)の4町、曽於郡大崎(おおさき)町からなる。おもな水系には、肝属川や、菱田(ひしだ)川、安楽(あんらく)川などがある。これらの河川は笠野原(かさのはら)などのシラス台地を深く刻んで流れるが、肝属川下流部を除き、沖積低地は広くない。

　笠野原は近年畑地灌漑(かんがい)施設が整備され、サツマイモ、菜種などの栽培から多様な果樹、園芸作物への転換が進められている。沖積低地は水田耕作が中心。肝属山地は大隅自然休養林、桜島や佐多岬は霧島錦江湾(きりしまきんこうわん)国立公園、志布志湾岸は日南海岸国定公園となっている。これらは亜熱帯植生（ソテツ、ヘゴ、ビロウなど）や、他の豊かな自然景観を主体としている。

［塚田公彦］

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