The correct option is 1, 2, 3 and 4.
Explanation
Mass movements refer to the transfer of rock debris down a slope under the direct influence of gravity. These movements are classified based on the speed of movement, the type of material involved, and the moisture content.
Statement 1 is Correct
A slump is a type of landslide characterized by the slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place. This rotation occurs because the movement happens along a curved slip surface.
Statement 2 is Correct
A debris slide involves the rapid rolling or sliding of earth debris without backward rotation of the mass. Unlike slumps, slides typically occur on planar surfaces (translational slides), resulting in the material moving down the slope without the characteristic backward tilt seen in slumps.
Statement 3 is Correct
Debris fall is the nearly free fall of earth debris from a vertical or overhanging face. It is distinguished from slides or flows by the lack of contact with the slope during the descent.
Statement 4 is Correct
A rockslide is the sliding of individual rock masses down bedding, joint, or fault surfaces. It is a rapid movement often triggered by earthquakes or undercutting of the slope.
Key Takeaway: The primary distinction between a slump and a slide is the mechanics of movement: slumps involve rotational movement on a curved surface, whereas slides involve translational movement on a planar surface without backward rotation.