Iwatahara Plateau - Iwataharadaichi

A plateau that spreads across the western Shizuoka Prefecture, on the eastern side of the downstream Tenryu River plain. From Kanzo in Iwata City, at an elevation of about 130 meters, the southern end passes through the central city area of ​​Iwata City and transitions into alluvial plain. The alluvial plateau was formed by uplift at the same time as the Mikatahara Plateau on the west bank of the Tenryu River, and the plateau surface is covered with gravel layers of the former alluvial fan deposits of the Tenryu River. The eastern side of the plateau is bordered by a steep cliff on the Ota River lowland. The plateau is dotted with ancient tombs such as Choshizuka, Shorinzan, and Inariyama, and the remains of Totomi Kokubunji Temple (a special historic site) are located in the Iwata city area. Small valleys have developed on the plateau, and place names with the characters "saka," "hara," "kubo," and "tani" can be seen, but development was delayed due to poor water quality. The area of ​​farmland and tea plantations is expanding due to the flow of irrigation water from the Tenryu River Downstream Agricultural Water Utilization Project. Forest land has also been cleared to create housing estates and industrial land, with industrial complexes for automobiles, engines, bearings, etc. visible in the southeastern part of the plateau. In addition, the plateau's gravel layers have been harvested for foundation materials and fill, causing significant changes to the natural landscape.

[Kitagawa Mitsuo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

静岡県西部、天竜川下流平野の東側に広がる台地。標高約130メートルの磐田市神増(かんぞ)から南端は磐田市の中心市街地を経て沖積地に移行する。天竜川西岸の三方原台地(みかたはらだいち)と同時期の隆起運動で形成された洪積台地で、台地面はかつての天竜川の扇状地堆積物(たいせきぶつ)の礫(れき)層で覆われる。台地の東側は急崖(きゅうがい)で太田川低地に接する。台地には銚子塚(ちょうしづか)、松林山(しょうりんざん)、稲荷山(いなりやま)などの古墳が分布し、磐田市街地には遠江(とおとうみ)国分寺跡（特別史跡）もある。台地面は小谷が発達して、坂、原、久保、谷などのつく地名がみられるが、乏水性のため開発は遅れた。天竜川下流農業水利事業による農業用灌漑(かんがい)用水の通水によって畑地、茶園面積も拡大している。林地も開かれて住宅団地の造成や、工業用地化も進み、台地南東部には自動車、発動機、ベアリングなどの工業団地もみられる。また、台地の砂礫層が基礎材や盛土用に採取され自然景観の変化が著しい。

［北川光雄］

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