Landslide
This article is about the
geological phenomenon. For other uses, see Landslide
(disambiguation).
A landslide, also known as a landslip, is a
form of mass wasting that
includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. Landslides can occur in underwater,
called a submarine landslide,
coastal and onshore environments. Although the
action of gravity is the primary driving force for a
landslide to occur, there are other contributing factors affecting the original
slope stability. Typically, pre-conditional
factors build up specific sub-surface conditions that make the area/slope prone
to failure, whereas the actual landslide often requires a trigger before being
released. Landslides should not be confused with mud flows, a form of mass
wasting involving very to extremely rapid flow of debris that has become
partially or fully liquefied by the
addition of significant amounts of water to the source material.
Landslides occur when the slope changes from a stable to an
unstable condition. A change in the stability of a slope can be caused by a
number of factors, acting together or alone. Natural causes of landslides include:
- groundwater (pore water) pressure acting to
destabilize the slope
- loss
or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire - a
fire in forests lasting for 3–4 days)
- erosion of the toe of a slope by rivers or
ocean waves
- weakening
of a slope through saturation by snow melt, glaciers melting, or heavy rains
- earthquakes adding loads to barely stable
slope
- earthquake-caused
liquefaction
destabilizing slopes
- volcanic eruptions
Landslides are aggravated by human activities, such as
- deforestation, cultivation and construction, which destabilize the already
fragile slopes.
- vibrations from machinery or traffic
- blasting
- earthwork
which alters the shape of a slope, or which imposes new loads on an
existing slope
- in
shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock
- construction, agricultural or forestry
activities (logging) which change the amount of water
infiltrating the soil.
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