ICSE Class 9 Answered

Mechanical weathering involves the breaking of fragments of rocks without changing its chemical composition. Some kinds of mechanical weathering are:

1. Block Disintegration: When the difference between the day and night temperature is large, rocks expand and contract. They expand during the day, when the temperature is high and contract during the night when the temperature is extremely low. This results in the splitting of rocks. This happens in regions where there is a great variation in the day and the night temperatures. Example in the deserts.

    

2. Granular Disintegration: When the agents of weathering, reduce rocks made up of different minerals to small pieces and fragments, it is called granular disintegration.

    

3. Exfoliation: The changes in temperature may create fissures or cracks in rocks. Water then enters into the cracks and the outer layer of the rock peels off. This is called exfoliation.

    

4. Frost Action: In regions of great variation between the day and the night temperature, cracks or fissures develop in the rocks. Water enters into these cracks. During the night, the water freezes into the cracks causing the rock to expand. During the day, ice in the fissures of the rock melts. When this process is repeated many times, the rock breaks. This is called frost action.