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Landslide

A landslide is the sliding down of a mass of land from a mountain, hill or cliff.

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, 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-existing 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.

Facts about landslides

  • Landslides are very common and occur in a variety of forms.
  • Land may topple off in a big chunk or slip down in bits, burying people in
    the process.
  • Landslides may be composed of mud or may contain rocks and other debris.
  • Landslides occur as a result of natural phenomena but human activity can also be a factor.
  • Landslides occur gradually but some failures may be sudden.
  • Vibrations from earthquakes and volcanoes can trigger a landslide.
  • Water logging due to heavy rains can saturate the top layers of unstable
    soil and cause them to slide downhill.
  • Many landslides in Antigua happen in the southern section of the island, extending from the Golden Grove – Jennings areas around through All Saints, Liberta and English Harbour areas.
  • Several of the hills within the Sherkley mountain range, especially Fig Tree Drive, John Hughes and Old Road are composed of a mixture of volcanic rock and soil.
  • Human activity such as deforestation, vegetation removal, construction of
    roads, and construction of buildings on steep slopes may also lead to land
    slippage.
  • Landslides may move very slowly from a few centimeters per year to a
    sudden, total collapse or avalanche.
  • Dominica experienced a landslide in May 2010. It was due to unstable soil
    conditions. Three people died.
  • Landslides may travel just a few meters to many kilometers in the event of mudflows.
  • Landslides can be very dangerous. They destroy houses, cars, water mains and gas pipes.

Tell-tale signs of an impending landslide

  • Doors or windows stuck or jammed for the first time.
  • New cracks appear in plaster, tile, brick, or foundation.
  • Outside walls, walks, or stairs begin pulling away from the building.
  • Slowly developing widening cracks appear on the ground or on paved areas such as streets or driveways.
  • Fences begin to lean or bulge down-slope.
  • Underground utility lines break.
  • Bulging ground appears at the base of a slope.
  • Ground water seeps to the surface in new locations.
  • You hear a faint rumbling sound that increases in volume as the landslide nears.

What to do about landslides

  • If you are constructing, find out the history of the area.
  • Plant trees to bind the soil and build retaining walls when you are building.
  • Use techniques such as terracing, when planting on slopes.
  • Maintain good drainage.
  • Beware of building on steep slopes or cutting into them to level the ground
    for building.
  • Putting too much weight on vulnerable areas can contribute to landslide
    hazards.
  • Beware of changing the natural course of waterways.