What is a landslide?

A landslide is the movement of a mass of rock, debris, or earth down a slope. Events such as heavy rainfall, earthquake and volcanic eruption can trigger a landslide, but they are not the only causes. More often than not, it is a combination of factors that lead to landslides. Geologists call landslides a type of “mass wasting,” which means any slope movement of soil and rock. The surface gets worn away as a result. Landslides could pose major hazards to people and property.

Underwater landslides resulting from factors such as earthquake are common too. These are called submarine landslides, which in turn can lead to tsunamis.

Geological factors

Landslides occur when the slope undergoes some processes that change its condition from stable to unstable. These could be due to geology and human activity. The geological factor concerns the material that forms the slope and the land. Some material with a loose, open sediment structure will weaken if they are disturbed or flooded with water. Absence of vegetation (or loss of it due to fire or drought), erosion and physical and chemical weathering are some of the geological factors that lead to landslides.

Human activities

Human activities such as deforestation (removal of deep-rooted vegetation), cultivation, building of roads and structures (without adequate grading of slopes), mining and blasting can destabilise or weaken a slope. Irrigation and vibration from machinery or traffic can also increase the risk of landslides.

Hazards can be mitigated by restricting or even removing populations from areas with a history of landslides and by restricting certain types of land use.

 

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