Abstract
A hard and fast classification of mass movements can neither be given nor make sense, because its practical application to the actual or natural phenomena encounters great difficulties. For the time being a simplification is preferable to pining for a too detailed classification of mass movements. This paper is chiefly concerned with clay minerals in areas of mass movements of flow- and slip-type in Canada, compared with those in Scandinavia and in Japan, and it stresses the important role of swelling clay minerals.