A landslide is the downhill movement of masses of soil and rock by gravity. Soil , as defined by civil engineers, is the loose material between the ground surface and the underlying bedrock .
Landslides come in many forms.
Rock falls occur along cliffs and outcrops where blocks of rock break off and fall down the slope. Block slides and slumps occur where blocks or masses of intact soil or rock move downslope along a failure surface. Slumps, on the other hand, have concave failure surfaces. As the landslide mass moves along this curved surface, it rotates and tilts trees and other objects so that they point uphill. The motion in an earth flow is analogous to a thick mixture of soil and water oozing down the slope.