Landslides: Groundwater increases the weight of the rock or the soil which contains it. Sometimes a mass of earth saturated with water slides down a hill slope causing landslides.

Causes: One or more causes such as lubrication by rains or melting snow, steep slopes and unusual structures, earthquakes, removal of support, or gravity may produce landslides. Lubrication of rocks takes place by means of rains or melting snows as in many parts of the Himalayas. Rocks become slippery and slide down. Steep slopes may be caused by the sliding of rocks straight through faulting or by quarries made by man. The sides of these may collapse on accounts of other factors.

Effects of landslides: Landslides and rock slides are of frequent occurrence in many mountains. National highways are closed. Cattle and vehicles suffer a lot.

Measures to reduce the risk during the landslides :

• Cutting down of trees must be stopped on mountain slopes.
• Avoiding construction of buildings on steep slopes.
• Building codes have to be followed strictly.
• Drainage should be proper.
• Afforestation on slopes is done.
• Retaining walls along roads are built.

Avalanches: The. sliding of ice along the slope leads to avalanches downwards. These cause a lot of damage to roads, cattle, human beings, buildings, etc. When the pressure of ice increases, it slides down the slopes.

Measures:

• Knowledge of avalanches is provided to people.
• Afforestation can check it.
• Barriers should be built to check the movement of avalanches.
• Ice-breaking machines are used to clear ice on roads.
• Relief is given to victims.