Uemachi Plateau - History and Formation

History and Formation

From the results of post-war university studies into geological stratum and faults and the examination of old maps, it is assumed that by around the fifth century a sand bank had already formed, eventually becoming the Uemachi Plateau. It is believed that in the Jomon period the Uemachi Plateau was a sandbank that separated the Inland Sea on the west and Kawachi Bay on the east. From the Yayoi period to current times large amounts of sediment was deposited from the Yodo and Yamato rivers. Kawachi Bay turned into Kawachi Lake, then into swampland, and finally into an alluvial plain. Similarly, due to the movement of rivers, the west side of the plateau became a plain which is now the center part of Osaka city.

In contrast to the relatively gently-sloping decent on the eastern side of the plateau, the decent on the western side is steep. This is because of the deposition of large amounts of sediment from the upper reaches of the Yodo and Yamato rivers located on the eastern side of the plateau. Whereas on the western side of the plateau a zero-meter zone is widely distributed from Osaka Bay.

The highest point of the plateau is at the base the main tower of Osaka Castle at 38 meters.

The names of Osaka wards Higashinari-ku and Nishinari-ku originate from the formation of the Uemachi Plateau. Higashinari literally means east-become (東成), and likewise Nishinari (西成) literally means west-become.