千葉県富津州のビーチカスプ
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概要
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From 1959 to 1960 the writer carried out observations of beach cusps that are developed along the normal high water line of the southern shore of the Futtsu cuspate foreland, Chiba Prefecture. The result revealed the following facts.<BR>1) All the year round, development of cusps is best in the Experimental Station zone (from the west of the Summer Bungalow of the Japan National Railway toward the tip of the foreland). The Onuki zone is the second best in the cusp development.<BR>2) Three types of cusps are recognized singular and lingulate type (A type), continuous and fan-shaped type (B type) and continuous and triangular type (C type). The A type cusps are distributed in the Summer Bungalow zone, B type ones in the Onuki and Summer Bungalow zones, and C type ones mostly in the Experimental Station zone.<BR>3) Intercusp space is generally between 3 m and 27 m. But, in the A type cusps the predominant space is 8 to 11 m, in B type ones it is mostly 10 to 18 m, and in C type ones it is mostly 10 to 15 m.<BR>4) The sediments constituting the surface of cusps comprise four types gravel type, shell type, sand type, and gravel-shell mixed type. In the report area the mixed type is predominant.<BR>5) In the area where cusps are undeveloped the beach profile has a 2° to 3° gradient, whereas in the area where development of cusps is good the gradient is 4° to 7°, steeper than the former area.<BR>6) The bottom profile of the surf zone is convex in the area where cusps are undeveloped, and concave in the area where cusps are developed well. As a factor of cusp formation, the difference in the bottom profile may be more important than the difference in the beach profile.<BR>7) The consecutive observations of the same group of cusps showed that the horn direction of cusps and the intercusp space are generally constant, except for a period of abnormally high water due to typhoons or some other causes.
- 社団法人 東京地学協会の論文