The Basic Landform Units Composing of Landslide Area

Abstract

In humid temperate region, Landslide is one of the most important processes of slope formation. But usual landform classifications of landslide area were uncertain and even the name of each landform units was not consistant. In this report the authors tried to set up the landform units composing of landslide area on the bases of usual studies and investigations of some Landslides occuring in the Tertiary of Tohoku district, from the point of view that each landform was not only an index of landslide area but also some reflextions of the process or structure of the Landslide.
The results obtained are summarized as follows.
1. ‘Topographical height’ is subdivided into four landform units. BLOCK is the height which is not crushed in the process of mass movement and is formed by tension stress. PRESSURE-RIDGE is formed by compression stress towards the movement direction, so it's structure is remarkably clushed. DEBRIS-FLOW-RIDGE and DEBRIS-FLOW-CONE are formed in the process of consumption of the end of landslide area by flow and composed of debris.
2. ‘Scarp’ is subdivided into two types. SLIDING SCARP is formed by slumping and SEPARATING SCARP is by glock-glide. They are generally divided by topographical feature and pattern of landform arrangement.
3. ‘Crack’ is subdivided into TENSION CRACK and COMPRESSION CRACK. Tension crack mostly grow at right angle to the movement direction.
4. ‘Hollow’ which is formed by block-glide and exposes slip surface can be recognized by topographical feature and we call it DITCH-LIKE-HOLLOW.
Consequently it become evident that each landslide area is composed of the conbination of above nine landform units.