Slides
By Angie Ramirez
A slide is a downslope movement of a rock or soil through a surface of rupture, which is the surface that separates the slide material from the more stable underlying material. There are two main types of slides: rotational slides and translational slides.
Rotational slide
In a rotational slide, the surface of rupture is usually deeper and has a curved shape like a spoon. The material displacement is generated in a rotational way with an axis that is roughly parallel to the slope’s contours. Because of this, the unstable mass tilts backward, allowing a collapse in the area adjacent to the crown with a move almost vertically downward and a slight uplift in the toe of the surface of rupture.
The displaced material commonly can move as a coherent mass along the rupture surface with minor internal deformation.
Schematic of a rotational slide. (Modified from Highland & Bobrowsky, 2008)
Translational slide
On the other hand, in a translational slide, the mass moves down and outward, along a surface of rupture relatively straight, which usually corresponds to a bedding plane that inclines in the direction of the slope. This material moves almost parallel to the slope of the terrain.
Depending on the inclination of the surface of rupture, the material can be mobilized further compared to rotational slides.
Schematic of a translational slide. (From Highland & Bobrowsky, 2008)