Landslide
- 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, see flow. 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.
Slope material that become saturated with water may develop 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.
An avalanche is similar in mechanism to landslide and it involves a large amount of ice, snow and rock falling quickly down the side of a mountain. Usually the ice builds in cornices or forms over a weaker layer of snow, creating the danger of an avalanche.
A pyroclastic flow is caused by a collapsing cloud of ash, poisonous gas and hot 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 [1]
- 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.
See also
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 [2]