Landslide

Related Topics:
Landslide_Disaster :: Landslides

This entry refers to the geological term. For political usage, see landslide victory. For the Fleetwood Mac song, see Landslide (song).

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. 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.

Special types of landslides

Debris flow

Slope material that becomes saturated with water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses, and cars, thus blocking bridges and tributaries causing flooding along its path.

Sturzstrom

A sturzstrom is a rare, poorly understood type of landslide. Often very large, these slides are unusually mobile, flowing very far over low angle, flat, or even slightly uphill terrain. They are suspected of "riding" on a blanket of pressurized air, thus reducing friction with the underlying surface.

Related phenomena

An avalanche, similar in mechanism to a landslide, involves a large amount of ice, snow and rock falling quickly down the side of a mountain. Usually the snow builds in cornices or forms over a weaker layer of snow, increasing the danger of an avalanche.

A pyroclastic flow is caused by a collapsing cloud of hot ash, gas and rocks from a volcanic explosion that moves rapidly down an erupting volcano.

Historical Landslides

The Storegga Slide - Norway
Frank Slide - Turtle Mountain, Alberta, Canada
The 1966 Aberfan disaster
Thistle, Utah on April 1983
The Mameyes Disaster - Ponce, Puerto Rico on October 7, 1985
Thredbo landslide, Australia on 30 July, 1997
Payatas, Manila garbage slide on 11 July, 2000.
Bluebird Canyon area in Laguna Beach, California, on June 1, 2005 ^*
Southern Leyte landslide in the Philippines on 17 February, 2006
Devil's Slide, an ongoing landslide in San Mateo County, California
Mount St. Helens eruption on May 18, 1980.

Reference

First-draft text taken from USGS fact sheet, public domain

External links

United States Geological Survey site
British Columbia government landslide information
Slide!, a program on B.C.'s Knowledge Network, with video clips
Geoscience Australia Fact Sheet ^*

Environmental soil science | Geological hazards

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