Change of Mountain Landforms due to Large Landslides : Geomorphological Research on Mass Movement of Mountainland

Abstract

The purpose of the present investigation is to clarify the relation of rapid landslide, larger than 10^5m^3 in total volume of landslide mass, betweetn ridge or spur of mountain, and valley in the humid temperate zone. The writer's conclusions attained are as follows : 1. Many large landslides occur at or near the former ones, but the scale of the new landslide is similar or somewhat larger than that of the former. 2. The mass of landslide falls down the valley floor and deposits, which makes the slope stable, and the cirquelike landform which is often observed on the higher part of the surrouding mountains is hardly formed. 3. There are some ridges which are retreated by collapsing of those tips as if the top of a nose is cut aslant, but these phenomena scarcely occur by eroding from the side flank. On the other hand, many spurs are easily liable to erode from the side and to retreat by collapsing. 4. Denudation to the river floor is given a greater influence to the large landslides than lateral erosion. 5. It is usually said that landslide occurs by the pressure of weight of the upper mass, but as to landslide on a large scale the writer states that the loss of support of lower blocks causes the land to slide.