The term Jisuberi, or landcreep, in Japan, refers to a slow and continuous displacement of a mass of debris formed by a former landslide; there is no basic difference between landcreep and creep proper.Yamakuzure, or landslide signifies a rapid movement of a mass of bedrock or mantle constituting the mountainside. Destructive landcreeps will hardly be distinguished from certain landslide. Landcreeps and landslides usually take place in sparsely populated mountainous districts, and are rather far from general attention and interest, although it is considered that recent reclamation and overlumbering in those areas have resulted the increase of their occurrences. In mountainous countries, gentle slopes formed by landcreeps and landslides are often preferred as locations of settlements or arable land, because of their lower inclination and more fertility of soil.Repeated occurrences of disasters on the same spots, and the preferability of such spots for habitation are dilemma hard to get out.
The writer investigated the sand-dune area near Tottori-shi, where he found many small basins named“Suribachi”(=mortar in English). He inspected the features of these basins and studied their subterranean condition geologically, obtaining the following results. 1) There are two types among“Suribachi”: the one has a fountain and the other has no fountain. The former has been a water-welling place befor the accumulation of sand-dune, while the latter is a simple basin which is surrounded by sand-dunes. 2) The writer finds out a volcanic-ash beds underneath the sand-dunes. The ash bed occupies a boundary layer between the recent sand-dune and the ancient one. He finds also clay beds directly below the ash bed. These clay beds are thought to be of a sediment in water and will become a key by which the writer can solve the episode from the ancient sand-dune to the recent one. 3) The ancient sand-dune is thought to be of a stable dune upon which plants grew. Here and there the writer has found goethite (“Takashi-kozo”in Japanese) among the ancient dune sand. 4) Judging from the site of outcrops of a bed rock and sedimentary condition below the sand-dunes, the writer might restore the ancient status as follows: the front of the recent sanddune area has proceeded forwards as far as 500 meters from the front of the ancicnt sand-dune area.