Landslide

A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flows, see flow. Although gravity acting on an over steepened slope is the primary reason for a landslide, there are other contributing factors:
Erosion by rivers, glaciers, or ocean waves create oversteepened slopes

Rock and soil slopes are weakened through saturation by snowmelt or heavy rains

Earthquakes create stresses that make weak slopes fail (see liquefaction, Hope Slide)

Volcanic eruptions produce loose ash deposits, heavy rain, and debris flows.

Vibrations from machinery, traffic, blasting, and even thunder may trigger failure of weak slopes

Excess weight from accumulation of rain or snow, stockpiling of rock or ore, from waste piles, or from man-made structures may stress weak slopes to failure and other structures

Groundwater pressure acting to destabilise the slope

In shallow soils, the removal of deep-rooted vegetation that binds the colluvium to bedrock