The outline of this paper is as following. 1. The stratigraphical sequences of the type locality (Neighbouring north-eastern area of the Musashino terrace) are as follows : Kanto volcanic ash bed 78 meters Musashino gravel bed 28 meters Tokyo group Upper Tokyo formation 10± meters Middle Tokyo formation 30± meters Lower Tokyo formation 180± meters Miura group 2. The basic ground, i.e. Miura group, is of undulating structure and dips toward the northeast with about 1° as a whole. 3. On the Miura group, there are found underground valleys which seem to be old river-roads, and which go straight from west to north-east. 4. The Lower Tokyo formation is distributed meeting with this basic ground and is developing its formation progressively from west or south-west to north-east. 5. On the surface of the Lower Tokyo formation, there are some buried valleys and the Middle Tokyo formation is distributed covering these valleys. The direction of these valleys is analogous to that of the valleys found on the surface of the Miura group. 6. And these two type valleys' features conform with the geological structure of the Miura group. 7. It is possible to consider that this fact is related with a series of tectonic movements in the Kanto basin. These movements are well known as the Kanto tectonic movement. 8. Judging from the direction of buried valleys and the conditions of development of the geological groups which cover the said valley, we guess that all the water system of this district was situated at least at the north-east or at the east-northeast, before sedimentation of the Musashino gravel bed. Therefore, as to the distribution of the Tachikawa terrace and the river-road of the River Tama, we guess that they had been formed after the formation of the Musashino terrace, by the movements which changed these old river-roads, this is to say, by the inclination of the basic ground which moved relatively ascending the north-western part of this district to the south-eastern part.
Taking the good opportunity of International Symposium on Land Subsidence held in Tokyo with excursion to Osaka and Niigata from September 17 to 23 in 1969, the writer tried to review the present situation of land subsidence in the world and its related problems. He gives definition of land subsidence as the comparatively progressive sinking in a limited area due to the artificial withdrawal of fluids such as ground water, gas, oil and so on. This phenomenon is different from the slower progressive downwarping movement in a tectonic basin or relative sinking due to eustatic movement during Quaternary age with the rate of 1-3 mm per year in Japan. The rate of land subsidence may differ by as much as one or two orders in magnitude. It may also be different from more rapid collapse due to mining of coal, gold and so on. According to R. Dolzal and M. Petersen's definition, subsidence, settlement and lowering are distinguished, the writer's definition corresponds to their settlement and in some case, to lowering. He reviewed the history of study on land subsidence in Japan, and grouped them to three categories. Leveling net-work covering all over Japan was established as early as the end of 19 centuries and precise geodetic leveling has been repeated at a fixed interval. This was very useful for making clear the phenomenological aspect of land subsidence. The first researcher, who gave attention to this problem was A. Imamura with his opinion of crustal movement. In an earlier stage of this survey, his successor, N. Miyabe might have the similar opinion, but soon later noticed that its cause was the contraction of the surface soil. Among these geophisicians, K. Wadati and his collaborators pointed out that there existed a proportional relation between the rate of subsidence and that of ground water pressure changes. S. Hayami added other elements such as tidal and artificial periodic changes to this. The second group was of soil mechanicians who applied Terzaghi's theory on compaction of clay layer. Y. Ishii and his collaborators estimated future amount of land subsidence and S. Murayama conducted laboratory experiments on land subsidence. The third group which is consist of geographers, geologists and hydrologist contributed to give the fundamental knowledges, for example, F. Tada and T. Nakano supplied subsurface topography of the land subsidence areas, S. Aoki and T. Shibasaki furnished Quarternary geology of these areas and I. Kayane and the present writer discussed water balance relations of the subsiding areas. These three groups are elaborating to proceed their researches and investigations with administrative officials. Now, Japan has many observation wells in land subsidence areas. (Tab. 1) He also summarized recent trend of subsidence in Japan (Tab. 2) collecting available data on the amount and rate of land subsidences in the world (Tab. 3) and pointed out the future problems and further studies.