Why do Landslides occur?
When there is a heavy rain and the ground becomes water logged, the land will not be able to hold water anymore. This state of the land gets converted into landslide. Landslides can be formed due to leaking water pipes, earthquakes, mining and volcanic eruptions. Landslides are known to occur generally when the gravitational forces are extremely higher than the material strength in a slope.
Landslides are created when rocks, debris and slumps slide on the broken, slick, clayey, water saturated curved or planar slippery surface. The landslide moves down and the ground surface tilts, cracks and drops. Due to the irrigation in the slopes, rain and melting of snow, water gets accumulated in the slopes. The water content in the slope raises the material weight over there, increases the pore pressure and dissolves the minerals slowly which further decreases the strength of the material in the slope. The increase in water and decrease in strength of the soil will in turn weaken the slope.
Excavation and soil erosion may lead to the reduction in the stability of the slope. The slopes filled with buildings, waste dumps, fills, and embankments increase the stress in the slope. The vibrations from large machines working for construction purpose or any earthquakes or increase in the pore pressure in the slope because of ground water, lead to landslide formation. The change in water level in small and large water bodies or streams might stimulate the formation of landslide across the shores or banks of the stream.
The landslides that are formed due to certain reasons may remain like that for years together. Later, they might get activated again whenever there is change in ground water levels or when water enters into the cracks in the ground. The movement of landslide might result due to some activities done related to construction which modifies the slope and diminishes its stability. This will lead to the formation of large landslides. To summarize, landslides result because of erosions, moisture additions, vibrations or shocks, and volcanic eruptions.