What is in news : Nine tourists were killed after heavy boulders fell on their van following a landslip near Basteri in Kinnaur district of Himachal Pradesh

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What are Landslides: A landslide is described as a mass of rock, debris or earth moving down a slope. Landslides are a form of mass waste under the direct influence of gravity, that indicates any down-slope movement of rock and soil. The word landslide encompasses five forms of slope movement, topples, falls, spreads, slides and flows.

Causes for Landslides

• Slope movement occurs whenever down-slope forces exceed the strength of the earth’s materials that make up the slope.
• Landslides may be caused by snowmelt, rainfall, water level changes, groundwater changes, stream flooding, volcanic activity, earthquakes, intrusion by human activities, or any combination of these causes, in slopes that are on the verge of movement.
• The shaking of earthquakes and some other factor can also cause aquatic landslides.