Kii Peninsula

A peninsula in the southern part of the Kinki region that juts out into the Pacific Ocean. It is the part of the Kinki region south of the Median Tectonic Line that connects the Kino River and the Kushida River, and is made up of the Kii Mountains. It faces the mouth of Ise Bay and the Kumano Sea to the east, and the Kii Channel to the west. It includes the entire Wakayama Prefecture and the southern halves of Nara and Mie Prefectures, and is the largest peninsula in Japan with an area of ​​approximately 9,900 square kilometers and a population of approximately 1.5 million. Geologically, it belongs to the Western Japan Outer Zone south of the tectonic line, and is arranged from north to north in the Paleozoic, Mesozoic, and Tertiary layers. Therefore, the mountain ranges and rivers also run roughly east-west, but in the center of the peninsula, the Omine Mountains run north-south, and the Daiko Mountains and Kiwa Mountains run parallel to both sides. The area is generally isotopic, with elevated quasi-plains with flat summits such as Mt. Odaigahara and Mt. Koya. Many of the rivers that flow through this area are meandering rivers with an antediluvian flow, such as Doro Hatcho.

As represented by Kumano in the southern part of the peninsula, the mountains are deep and mature, approaching the coast, and coastal terraces rise steeply to the sea level, as in the ria coasts of Kihoku and Shima, and along the coast of the Kumano Nada Sea. Therefore, there are few basins or river basin plains, and apart from the Wakayama Plain at the mouth of the Kinokawa River and the Ise Plain at the mouth of the Kushida River, there are only narrow plains at the mouth of the Hidaka River. There is no real plain along the 1,200 km long coastline.

The climate is warm due to the influence of the Kuroshio Current, and as can be seen from the fact that Mt. Odaigahara is the rainiest area in Japan, the southern part of the prefecture receives ample rainfall, which has nurtured the rich mountain forests of Yoshino and Kumano. Most of the population is concentrated along the coast. There are only two railway lines: the JR Kisei Main Line, which runs along the coast, the Sangu Line on the Shima Peninsula, and the Wakayama Line, which runs along the Kinokawa River valley. This is why the former Japanese National Railways' planned line across the peninsula only remained in planning form. Meanwhile, there are more than 200 fishing ports along the long coastline, and Tanabe, Kushimoto, Katsuura, Nikishima, and Daio are bases for deep-sea fishing. Blessed with scenic mountain and sea views and hot springs, the prefecture is connected to mountain religious sites such as Ise, Koyasan, Kumano, and Yoshino, and is home to the Yoshino-Kumano and Ise-Shima National Parks, as well as the Koyasan-Ryujin Quasi-National Park.

[Yoichi Koike]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

近畿地方南部、太平洋に突出した半島。近畿地方のうち、紀ノ川と櫛田(くしだ)川を結ぶ中央構造線以南の部分で、紀伊山地によって構成される。東は伊勢(いせ)湾口部と熊野灘(なだ)に、西は紀伊水道に臨む。和歌山県全域と奈良、三重両県の南半部を含み、面積約9900平方キロメートル、約150万の人口を有する日本最大の半島である。地質的には構造線以南の西日本外帯に属し、北から古生層、中生層、第三紀層と配列する。したがって山脈、河川もほぼ東西方向をとるが、半島中央部は大峰(おおみね)山脈が南北に走り、台高(だいこう)山脈、紀和山脈が両側に並行している。全体として等高性の山地で、大台ヶ原山や高野山(こうやさん)などに山頂平坦(へいたん)面が残る隆起準平原である。この間を流れる河川も瀞八丁(どろはっちょう)に代表されるような先行性の曲流が多い。

　半島南部の熊野に代表されるように、山地は壮年期の深山で、これが海岸にまで迫り、紀北や志摩のリアス式海岸や熊野灘沿岸のように海岸段丘が海面に切り立っている。したがって盆地や流域平野に乏しく、紀ノ川河口の和歌山平野、櫛田川河口の伊勢平野のほかは、日高川河口などに狭い平野がみられるにすぎない。延長1200キロメートルに及ぶ海岸線にも平野らしい平野はない。

　気候は黒潮の影響で温暖であり、大台ヶ原山が日本最多雨地帯であるように、主として南部は雨量が豊富で、吉野、熊野の豊かな山林地帯を育てた。人口はほとんど海岸部に集まる。鉄道は海岸をたどるJR紀勢本線と、志摩半島の参宮線のほか、紀ノ川河谷に沿う和歌山線だけで、半島縦断の旧国鉄の計画線が計画だけに終わったのもそのためである。一方、長い海岸線には200以上の漁港が並び、田辺、串本(くしもと)、勝浦、二木島(にきしま)、大王(だいおう)などは遠洋漁業の根拠地である。山と海の景勝地と温泉に恵まれ、伊勢、高野、熊野、吉野などの山岳宗教の地と結び、吉野熊野、伊勢志摩の国立公園、高野竜神(りゅうじん)国定公園がある。

［小池洋一］

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