Roger Moore 2020
Mass
Movement
Mass movement is characterized by the transfer of large volumes of soil and/or rock. It can be subdivided into two categories. The first one consists of the downward movement of the land surface, without a new surface. This is called subsidence.
The second category, which is the focus of this site, is the downward and/or outward displacement of soil and rock, which forms a new surface. This type of movement is most common on slopes, as the diagram shows. Many different mechanisms come into play when looking at the variety of movements possible. Falls are movements along very steep slopes, where the mass travels most of its distance in the air. Topples involve rotational movement about a pivot point below the center of gravity of the block.
There are different categories of slides, such as translational slides, where chunks of rock break off and slide downslope. Block slides are a type of translational slide, very similar to a rockfall, but on a gentler slope. There are rotational slides, where the body of the slide rotates downhill and gives out. Mudslides are blocks of oversaturated soil that move downhill.
Let's take a closer look at slides.