A series of coastal and near-shore survey was carried out in 1962 by members of the Japanse Hydrographic Office on the beach of Ninomiya, Kanagwa Prefecture. The author, leader of the survey, made an investigation into the seasonal change of the beach and the sea bottom near shore from the results of the survey conducted several times within the one-year period.
Situated at the northwest corner of Sagami Bay, the Ninomiya coast has a narrow beach of 60 to 70 meters in width, running east-west on the south side of the Ôiso Hills. The sea bottom near the shore of Ninomiya coast is flattened by both wave abrasion and sedimentation down to 20 meters in depth and continues to a steep slope of deeper than 20 meters which several gullies incise. Some beach developments by small waves were observed during summer season and erosion during late summer and late spring by stormy waves was also recognized. While, the sea bottom near shore was eroded during summer season by long. period waves and deposited during late summer by stormy typhoon waves.
Major records of the beach cycle observed are as follows: The berm was cut back and extinguished by stormy waves during late spring and the beach fore-shore became more gently sloping. In the calm season of small waves, sands started piling up on the beach to form a new berm, which later showed a growth. At the typhoon season of late summer, again the berm was cut back and the beach fore-shore became gently sloping. Beach cusps occurred in accordance with the formation of berm during summer season, but they were sharpened upward with berm development. Both berms and beach cusps disappeared because of the typhoon. From measurement of the inner structure of beach sediments, it may be said that the beach was rapidly deposited with sands of about 1 meter in thickness after it was eroded by stormy waves. Then, gravels were deposited on the seaward edge of the berm as cusp materials no sooner than the formation of berms and cusps started. Distribution of gravels extended on the beach with the devel opment of berms and cusps during calm season.
The sea bottom near shore showed a gentle profile with minor steps in front of large cusps in late spring. During summer season it was eroded and the profile was further smoothed away because of distinguishable erosion of the edge of the steps. Eroded areas were formed in front of the large cusps and elongated in north-south direction. Sea bottom in front of the cusps was filled with finer sediments, and was slightly elevated against other areas. The author thinks that the large cusps were on the route of the near-shore circulation of sediments, since the cusps adjacent to the eroded areas of the sea bottom received much sedimentation during summer season.
At the typhoon season of late summer, the sea bottom near shore received considerable sedimentation in contrast to the beach where erosion took place simultaneously. Deposited areas were found on the seaward extention of the large cusps, coincident with the eroded areas formed during calm season. In such areas, the sea bottom again showed a profile with minor steps due primarily to the sheet flow of sediments by rip curreat. At the same time, offshore bars occurred temporarily by stormy waves, but within a month after the storm those offshore bars disappeared.

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In this paper, the distribution of beach rocks in the Japanese Islands is shown, and the origin of them is discussed on the basis of their structure, forms, and location in the shore profile.
Beach rock in Japan can be classified as follows: (1) Intertidal beach rock: (2) reef surface beach rock (this is subdivided into reef-like beach rocks and Tatamiishi beach rock), and (3) conglomerate beach rock. The last one is found as far north as Tateyama (35°N, 140°E) in Chiba Prefecture.
R. J. Russel and S. Yonetani attributed its origin to underground water. But the present author considers from the survey made on Yoron Island process of the formation of beach rock consists of two distinguishable stages, that is, the stiffening of the stratum on lagoon floor and the consolidation in the intertidal zone, and that the effect of underground water would be negligible.
The formation of micro-cuesta topography of rock is due to (1) sea water which dissolves and precipitates minerals, (2) heating by strong insulation, (3) slow lowering of sea-level, and (4) existence of a calm lagoon.
The process of beach rock formation is explained as follows: (1) Detrital materials deposit on a lagoon floor, rather coarser materials during stormy weather or seasons and finer materials during cairn weather alternatively. (2) incipient consolidation (stiffening) on the surface of a lagoon floor in calm terms is held by calcium carbonate brought by sea water and organisms. (3) The slow lowering of sea-level causes beach rock to locate at the intertidal zone. They are deformed at that place, mainly by tidal action so as to have a seaward surface dip of 0° to 10°. This dip coincides with the general beach slope. At the same time, heating by strong insolation and evaporation of sea water makes calcium carbonate abhere to deposited particles and then dry and consolidate deposits. (4) As the lowering of sea-level progresses, beach rock rises up above high-tide level. Then it is consolidated more firmly, but it suffers from destructive agencies.

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In the Higasi-Kubiki Mountains, Niigata prefecture, the well-known Kamiya Landslide about 20 km east of Takada City of which miocene Teradomari black shale is the only constituent has been active for the last several centuries, although the exact year of the beginning of the movement is not known. The crown of the slide has been regressing year after year by sliding and/or fall mainly in the period of snow melting. The size of the mass which continues to move is about 1400 m long, 400 to 500 m wide and about 20 m deep at the present time.
On the upper half of the slide, there are three scarps (upper, middle and lower scarp) and two terraces (upper and lower) between those scarps, as shown in Fig. 1. Each terrace surface dips toward mountain side, being different from the general slope of the slide, as shown by the cross section in Fig. 2.
Without any fixed evidence have many authors believed that the topographic feature of terraces was formed by rockslides which are termed “sô-suberi” in Japanese based primarily on the assumption that the valleyward-dipping bedding plane is coincident with topographic surfaces of the middle and fower scarps. In other wards, they have assumed that the two scarps are themselves true surfaces of rupture (or planes of sliding). This article concerns with revision of such imagination.
From the results of geologic survey at the slide and its vicinity, dip of the bed rock which is composed of miocene black shale including very thin tuff layers was expected to be about 30 degrees or more for WNW at the middle scarp of the slide. The field evidence at the spot, however, sohows a remarkably lower dipping plane (15°N) in the direction of N 60°W against many authors' conjecture and the above-mentioned expection, as shown in Fig. 3.
This fact suggests that the mass below terraces took backward rotations with little internal disturbance.
With the aim of confirming this suggestive fact of the slump, physical prospecting on the surfaces of rupture below the upper and lower terraces was made by means of electro-resistivity method. As a result of the prospecting, the surfaces of rupture are presumably concave below these terraces, as illustrated by dotted lines in Fig. 2. Furthermore, the slump blocks seem to take little downslope movement. Consequently, the terrace features of this fandslide were concluded to be formed by backward rotation to which the terms “slump (Sharpe, 1938, Crandell, 1954), slump-earthflow (Jones et al, 1961, Vernes, 1958), treva block (Reiche, 1937), shearing slide (Terzaghi, 1950) and Felsstürze (Heim, 1930)” have been already given.
It could not be clarified whether the movement at the present time (4-5m in a year at the lower half) which is considered as a plastic flow has a relation to the movent forming the terrace topography, This slump was not caused directly by excavation from the toe of original valley wall, because lateral erosion by the revulet Hirakatagawa takes piece far away from the slump blocks.

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[in Japanese]

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