Kutsuna Islands

A group of islands in the eastern part of the Boyo Islands, located on the border between the Iyo Nada Sea and the Itsuki Nada Sea in the Seto Inland Sea. They were within the sphere of influence of the manor of the Kutsuna clan, a development feudal lord during the Nanboku-cho period, and belong to Matsuyama City, Ehime Prefecture. The islands are known as the Kutsuna Seven Islands, including Nakajima, Muzukijima, Nogutsunajima, Nuwajima, Tsuwajijima, Futagamijima, and Gogojima. There are also 22 uninhabited islands. They are made up of granite from the Ryoke Belt, and the mountainous areas of the islands are a group of dissecting volcanoes formed by selective erosion of andesite, a volcanic rock from the Tertiary Period. The complex coastline is typical of subsiding islands, and the beach ridges formed by the accumulation of drift sand in the inlets form crescent-shaped beaches, creating a beautiful shoreline typical of the Seto Inland Sea. Many of the islands are included in the Seto Inland Sea National Park. The warm, low-rainfall climate and weathered granite soil are ideal for growing fruit such as mandarin oranges and loquats.

[Kazuo Fukaishi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

瀬戸内海の伊予灘(いよなだ)と斎灘(いつきなだ)の境界にある防予(ほうよ)諸島東部の島群。南北朝期の開発領主忽那氏荘園(しょうえん)の勢力範囲で、愛媛県松山市に属す。中島、睦月(むづき)島、野忽那(のぐつな)島、怒和(ぬわ)島、津和地(つわじ)島、二神(ふたがみ)島に興居(ごご)島を加え、忽那七島という。ほかに22の無人島がある。領家帯花崗岩(かこうがん)類からなり、島の山地は第三紀の火山岩である安山岩などが選択侵食された開析火山群。沈降性島嶼(とうしょ)特有の複雑な海岸線をなし、入り江には漂砂が堆積(たいせき)してできた浜堤(ひんてい)が三日月状となって瀬戸内海的な汀線(ていせん)美を呈し、瀬戸内海国立公園に含まれる島が多い。温暖寡雨の気候と花崗岩の風化した土壌は、ミカン、ビワなどの果樹栽培に適している。

［深石一夫］

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