Yonezawa Basin

A basin in the southern part of Yamagata Prefecture. It is 24 km north to south and 7 to 18 km east to west. It is a sedimentary basin made up of the accumulation of sand and gravel carried by the Matsukawa and Omonogawa rivers, which originate from Mt. Azuma in the south, the Yashiro and Wada rivers that flow down from the Ou Mountains in the east, and the Yoshinogawa river that flows south from the Shirataka Hills. Alluvial fans are formed by these rivers on the outskirts, and the Matsukawa river flows north through the center of the basin, merging with the other rivers before passing between the Nagameyama and Isazawa hills, entering the Nagai Basin and becoming the Mogami river. The basin floor is dominated by rice paddies, and the surrounding hills are a popular place for growing grapes, apples, and other fruits. The basin is centered in Yonezawa city and Nanyo city. This basin is said to have been formed when a lake that was created by the collapse of a fault line dried up, and Lake Hakuryu (Nanyo City) in the northern part of the basin is said to be a remnant of the former lake basin.

[Shige Nakagawa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

山形県南部にある盆地。南北24キロメートル、東西7～18キロメートル。南部の吾妻(あづま)山を源流とする松川や鬼面(おもの)川、東部の奥羽山脈から流下する屋代(やしろ)川、和田川、白鷹(しらたか)丘陵から南流する吉野川などが運び込んだ砂礫(されき)の堆積(たいせき)した堆積盆地。周辺部にはこれらの河川の扇状地が形成され、盆地中央を松川が北流、諸河川を合流して眺(ながめ)山、伊佐沢(いさざわ)両丘陵間を抜け、長井盆地に入り最上(もがみ)川となる。盆地床は水田が多く、周辺丘陵地はブドウ、リンゴなど果樹栽培が盛ん。盆地の中心は米沢市と南陽市。なお、この盆地は断層の陥没によって生じた湖が干上がってできたものといわれ、盆地北部の白竜湖(はくりゅうこ)（南陽市）はかつての湖盆の残存湖といわれる。

［中川　重］

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