The Uplands and Lowlands of Tokyo: A Geomorphological Outline

Landforms of the main part of Tokyo Metropolis consist of Pleistocene uplands and Holocene lowlands. The original forms of upland surfaces are sea bottoms of the Last Interglacial Age, or the fluvial surface of the Last Glacial. These terrace surfaces are covered with thick air-laid tephra layers. They were supplied by westerly sitting volcanoes such as Mt. Fuji and the Hakone Caldera during the late Pleistocene. The uplands are dissected by valleys whose heads are situated on the upland surface. Some valleys in the upland were formed by remnant streams on the upland surface where tephras were accumulated. The origin of these valleys dates back to the Last Glacial. The lowlands were the places where some large valleys were cut during the Last Glacial. The marine deposits of the Postglacial Transgression buried these valleys. Fluvial systems, including the Japan's largest river Tone, developed after that. These deposits formed the “soft ground”. The outline of the evolution of Tokyo Lowland during the late Holocene is shown by the method of historical ge-omorphology. Since the 17th century, river courses have been changed artificially and the coastal area along Tokyo Bay has been reclaimed and filled up. The Tokyo Lowland is the most transformed area by human activities in Japan. The characteristics of the mobile belt such as crustal movements and volcanic activities have played as important a role as the eustatic changes in the landform of the uplands and lowlands of Tokyo. Human activities are increasing on the landform of Tokyo.