Weathering class 7

WEATHERING

1. Weathering

2. Difference between weathering and erosion Weathering involves disintegration and decomposition of rocks. It is a static process. It is important for soil formation. Erosion wears and tears away the rocks and transports the eroded materials. It is a dynamic process. It is a destructive process.

3. Types of weathering A. Mechanical weathering. B. Chemical weathering. C. Biological weathering.

4. Mechanical weathering Disintegration of rocks due to elements of weather such as frost, wind, plants, man and animals. It depends on the following factors: Extremes of temperature, nature of rocks, structure of rocks, frost, wind and slope of the land.

5. Extremes of temperature In arid and semi arid regions due to intense heat of day time the rock gets expanded and during night due to cool temperature the rock gets contracted. Due to this repeated process the rocks become weak and gets disintegrated. In some cases the rocks peel-off layer by layer resulting in a rounded structure of rock and we call it as exfoliation.

6. Exfoliation of rock

7. Nature of rocks Some rocks may be hard and some be soft. Mechanical weathering takes place in soft rocks. Eroded materials are easily lifted by wind.

8. Structure of rocks. Vertically arranged layers of rocks are more susceptible to weathering than the horizontally arranged layers.

9. Frost Most common agent of weathering in temperate regions. Water enters into cracks, turns into ice and the volume increases. During the day ice thaws and water enters deep into rocks. Repeated process results in breaking of rocks.

10. Frost

11. Wind Most common feature in deserts. Soft rocks are eroded and blown away by wind.

12. Slope of land Steep slopes of rocks are eroded more rapidly than the gentle slopes.

13. Homework to be written in c.w Answer the following questions. 1. What is meant by exfoliation? 2. Describe the action of frost in weathering of rocks. 3. Differentiate between weathering and erosion.