Question

The mass movement of rock, debris or earth down a slope is referred to as:
1. Volcano
2. earthquake
3. flood
4. landslide

Answer 1

Correct Answer - Option 4 : landslide

The correct answer is Landslide.

• A landslide is defined as the movement of a mass of rock, debris, or earth down a slope.
• It occurs when the consequence of a complex field of forces (stress is a force per unit area) active on a mass of rock or soil on the slope.
• The term landslide encompasses five modes of slope movement: falls, topples, slides, spreads, and flows.
• It happens due to geological causes, morphological causes, physical causes, and human causes. 
• There are two parameters that determine the landslides are as follows:
  • ​Increase of shear stress: It happens due to the removal of lateral and underlying support; an increase of lateral forces as well as a load, transitory stresses like blasting, earthquakes, etc., and geological movement.
  • Decrease of material strength: It happens due to the weathering, pore water pressure, and changes in structure.
• ​The incidents of landslides increasing day by day due to over urbanization, massive deforestation, construction, and development work in landslide-prone areas.

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Volcano	A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
Earthquake	An earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves.
Flood	A flood is an overflow of water on normally dry ground. This is most commonly due to an overflowing river, a dam break, snowmelt, or heavy rainfall. Less commonly happening are tsunamis, storm surge.