WHAT IS A 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. Landslides are rock, earth, or debris flows on slopes due to gravity. They can occur on any land which has right condition of soil, moisture, and the angle of slope.  Also known as mud flows, debris flows, earth failures, slope failures, etc., they can be triggered by rains, floods, earthquakes, and other natural causes as well as human causes, such as grazing, terrain cutting and filling, excessive development, etc.  Because the factors affecting landslides can be geographical or human-made, they can occur in developed areas, undeveloped areas, or any area where the land was changed for roads, houses, buildings, and even for lawns in one's backyard. It is a natural hazard.

Famous landslides in history

Some of the most famous landslides are the following- the Uganda landslide 2010, the LA Conchita landslide 1996, Manilla landslide 201 , Sinking creek and the Allapian Valley.

How are landslides caused?

The causes of landslides are usually related to instabilities in slopes. It is usually possible to identify one or more landslide causes and one landslide trigger. The landslide causes are the reasons that a landslide occurred in that location and at that time. Landslides include geological factors, morphological factors, physical factors and factors associated with human activity. One of the main reasons is deforestation. There are no trees to absorb the rain and thus this affects the soil causing it to collapse.

Gravity is the primary factor in a landslide. Soil on a flat surface does not move. On a slope, gravity alone also may not trigger a landslide. But when another disrupting factor == like rain == comes into play, gravity will pull sediment downhill.

• Water: Perhaps the most common trigger of a landslide, water reduces the friction between the bedrock and the overlying sediment, and gravity sends the debris sliding downhill. In sand and clay soils, a small amount of water may increase stability. You've likely seen this when building a sand castle or working with clay. However, too much water causes the sediment to flow, which is why many landslides occur after rainstorms.
• Earthquakes: If the Earth's crust vibrates enough to disrupt the force of friction holding sediments in place on an incline, a landslide can strike. 

• Effects of landslides

  Landslides are very dangerous and destructive to sum extent they cause severe injuries and death! Archaeological evidence suggests that not many people perished in the sinking creek mountain however many farms and crops were destroyed and in some places animals were killed. It affected a huge piece of and drastically changed the landscape. They displaced a lot of land. New species of plants have grown on the slopes. Few houses were destroyed but fortunately, not many people lived near the creek. Nowadays, landslides occur in places with a lot of industrialization and land clearing which claim more lives than the countryside.

  References:

  www.bbcschools.co.uk

  http://bit.ly/116aJYg
  

  Daily Nation Newspaper