Tsuyama Basin

A basin in the northeastern part of Okayama Prefecture, it is the largest of the basins that run east to west between the Chugoku Mountains and the Kibi Plateau. To the north are Mt. Nagi (1,240 meters) and Yamagata-Sen (791 meters), and the hills and plateaus at the foot of the mountains are made of Japanese original layers, which are made of bedrock consisting of Paleozoic and Mesozoic layers, Tertiary layers, and diluvial layers. In the lower part, there are alluvial deposits formed by the Yoshii River and its tributaries. The altitude is 100 to 200 meters, and the climate is Seto Inland Sea type overall, but shows inland characteristics, with lower average temperatures, maximum and minimum temperatures, and more precipitation than Okayama. There are about 100 days a year when fog occurs, especially in winter. The local wind that occurs in the eastern part of the basin, in Nagi Town, Katsuta County, at the foot of Mt. Nagi, and in the eastern part of Tsuyama City, is known as the Hirotokaze. The central city of the basin is Tsuyama City.

[Shogo Yuihama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

岡山県北東部にある盆地で、中国山地と吉備(きび)高原の間に東西に分布する盆地列中の最大。北側には那岐(なぎ)山（1240メートル）、山形仙（791メートル）などがあり、山麓(さんろく)の丘陵や台地は、古生層、中生層からなる基盤岩および第三紀層、洪積層よりなる日本原層で形成される。低部には吉井川とその支流の形成した沖積層がある。標高100～200メートルで、気候は全体としては瀬戸内型であるが内陸性を示し、岡山と比べて平均気温、最高・最低気温とも低く、降水量は多い。霧の発生日数が年間約100日あり、とくに冬に多い。盆地の東部、那岐山麓の勝田郡奈義(なぎ)町や津山市の東部に発生する局地風は広戸風(ひろとかぜ)として知られる。盆地の中心都市は津山市。

［由比浜省吾］

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