Landslides

People recovering belongings after a landslide

A landslide is the movement of rocks and soil down a slope and, when a large slide occurs in an area of dense human habitation, large numbers of people can be killed. In January 2011 mudslides in south-eastern Brazil killed more than 400 people.

Many natural events such as heavy rainfall, an earthquake or volcano can trigger a landslide, but human activities such as building construction can also cause or increase the chances of such an event.

The biggest landslide in recorded history was triggered by the eruption of Mount St Helens in 1980, according the United States Geological Survey. Nearly 3km3 of rock moved down slope.

Image: People recovering belongings after a landslide in southern Valle de Las Flores, La Paz, 27 February 2011 (credit: AFP/Getty Images)

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People recovering belongings after a landslide Landslides

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Landslides

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.

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