“Weathering is the breaking down of rocks, soil and minerals as well as wood and artificial materials through contact with the Earth’s atmosphere, biota and waters.

1. Mechanical weathering is the physical breakdown of rocks into smaller and smaller pieces. One of the most common mechanical actions is frost shattering. Another type of mechanical weathering is called salt wedging. Winds, water waves, and rain also have an effect on rocks as they are physical forces that wear away rock particles, particularly over long periods of time.
2. Organic or biological weathering refers to the same thing. It is the disintegration of rocks as a result of the action by living organisms. Trees and other plants can wear away rocks since as they penetrate into the soil and as their roots get bigger Microscopic organisms like algae, moss, lichens and bacteria can grow on the surface of the rocks and produce chemicals that have the potential of breaking down the outer layer of the rock. 
3.  Chemical weathering happens when rocks are worn away by chemical changes. The natural chemical reactions within the rocks change the composition of the rocks over time. Because the chemical processes are gradual and ongoing, the mineralogy of rocks changes over time thus making them wear away, dissolve, and disintegrate. The chemical transformations occur when water and oxygen interacts with minerals within the rocks to create different chemical reactions and compounds through processes such as hydrolysis and oxidation.

The Loo is a strong, hot and dry summer afternoon wind from the west which blows over the western Indo-Gangetic Plain region of North India and Pakistan. It is especially strong in the months of May and June.

Physical weathering is also called as mechanical weathering. This is the process where rocks breakdown without altering their chemical composition. Physical weathering can occur due to temperature, pressure or snow. There are two main types of physical weathering. They are freeze thaw and exfoliation.

Chemical weathering is the decomposition of rocks due to chemical reactions. This changes the composition of the rock. This often takes place when rain water reacts with minerals and rocks. Rain water is slightly acidic (due to dissolution of atmospheric carbon dioxide, carbonic acid is produced), and when the acidity increases chemical weathering also increases. With the global pollution, acid rains occur now, and this increases chemical weathering more than the natural rate.

Physical weathering does not change the chemical composition of the rock whereas chemical weathering changes the composition.

Physical weathering may result due to temperature, pressure, snow, etc. whereas chemical weathering mainly takes place due to rain.

Rapid Movement - involves a visible movement of material. Occurs very suddenly and rapidly. These types of movements can be very dangerous. Result in loss of life and property. Most occur on steep slopes and can involve rock, soil or debris.

Slow Movement - advances very slowly. Usually only noticeable by the effects of their movements. Responsible for the down-slope transport of a much greater volume of material since it is always occurring.

Terrestrial hazards: The hazards which originate inside the earth or its atmosphere are called terrestrial hazards.

E.g. Volcano, Earthquake