Landslide



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 affecting the original slope stability:

* 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.

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.

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.

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
* Cliff landslip of the Undercliff near Lyme Regis, Dorset, England, on 24 December 1839
* Frank Slide - Turtle Mountain, Alberta, Canada, on 29 April 1903
* The 1966 Aberfan disaster
* Thistle, Utah on 14 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.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
Virtual Magic is a human knowledge database blog. Text Based On Information From Wikipedia, Under The GNU Free Documentation License. Copyright (c) 2007 Virtual Magic. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

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