This document summarizes the key concepts of weathering. It defines weathering as the physical, chemical, and biological breakdown of rocks due to atmospheric forces like wind, water, and glaciers. The three main types of weathering are physical, chemical, and biological. Physical weathering breaks rocks into smaller pieces through frost wedging, wetting and drying, exfoliation, and abrasion. Chemical weathering alters the composition of rocks through oxidation, hydration, carbonation, and acid rain. Biological weathering is caused by organisms like lichens. Over time, weathering and erosion form soil from broken down rock materials.

2. Roll # 02
BS-Geology 1st semester
Mr. Aamir Asghar
Sabz Ali Khan & Malli Khan Institute Of
Earthsciences

3. What Is Weathering?

4. What Is Rock?
• Aggregate of minerals
is known as rock.
• Rock is naturally
occurring in the earth.
• Which have different
physical & chemical
properties.

5. What Is Weathering?
Defination:
• The Physical, Chemical & biological Break Down
Of Rocks Is Called Weathering.
• The Rock Break and Undergo Decay Under The
Influence Of Atmosphere Agencies Like
Wind,Water, And Glaciers.
• Disintigration Of Rock Known As Weathering.

6. Types Of Weathering
 There Are Three Types Of Weathering:-
1. Physical Or Mechanical Weathering:
2. Chemical Weathering:
3. Biological Weathering:

7. Physical Weathering
•Rock break into pieces.
•Changing size and shape.
•But not their composition.
•Example: Breaking of a rock
cliff into boulders and
pebbles.

8. Types of Physical weathering
Following are the agents or types of physical
weathring
•frost wedging:
•Wetting and drying:
•Exfoliation:
•Plant Growth:
•Thermal expansion:
•Abrasion:
•Burrowing of animals:
•Temperature changes:

9. Frost wedging
1. Water enter the small
cracks in the rock.
2. When it freezes,it
expand and forces the
crack to open more.
3. The process repeat
over again untill the
rock break apart.

10. Frost wedging

11. Freeze-thaw weathering in action

12. Wetting and drying
1. breaks up rocks that are
made from clay.
2. When they are wet they
expand, and they shrink
as they dry.
3. As this repeats over and
over, the clay becomes
weak and cracks.

14. 1. The top rock layers are
removed releasing
pressure.
2. The underlying rocks
then crack and fall apart.
Exfoliation

15. Granite exfoliation:-

16. Plant Growth:-
•As plants such as trees send
out root systems, the fine
roots find their way into
cracks in the rocks. As the
roots increase in size, they
force the rock sections apart,
increasing the separation
and weathering.

17. Root wedging:-

18. Thermal expansion
1. Daily cycle of temperature change weakens rock.
2. Rock expand when they are heated and contract
when they cool.
3. The repeated expansion and contraction tends to
develop cracks in rocks.
4. It is most common in deserts.

19. Abrasion
1. Many rocks along on the
beach or stream or river
are rounded.
2. They have been rounded by
collision during down
stream movement with silt
and sand carried by water.
3. Abrasion is also done by
wind.

20. Chemical Weathering
1. When agents of weathering
chemically change the composition
of rock.
2. The process that break down the
rock through chemical change.

21. Agents of chemical weathering:-
1. Oxidation:
2. Hydration:
3. Carbonation:
4. Acid rain:
5. Living organisms:

22. Oxidation:-
1. oxygen reacts with some minerals,
especially those containing iron to form
rust (called iron oxide)
2. Oxygen combines with minerals to form
oxides.
(iron + oxygen = Rust)

23. Hydration:-
•Minerals absorb water and chemically change the
composition of the material.

24. Carbonation:-
•When pollutants like Carbon Dioxide, Nitrogen & Sulfuric
Oxides mix with rain water creating acid rain, which can
dissolve limestone and harm the living environment.
1:- 2:-

25. Karst Topography
1. A type of landscape in
rainy regions where there
is limestone near the
surface, characterized by
caves, sinkholes, and
disappearing streams.
2. Created by chemical
weathering of limestone

27. Acid rain:-
1. Compounds from burning coal, oil and gas react
chemically with water forming acids.
2. Acid rain causes very rapid chemical weathering.

28. Living organisms:-
•Lichens that grow on rocks produce weak acids that
chemically weather rock.

29. 1. They wedge their tiny
roots into spores and
crevices.
2. When the roots grow, the
rock splits.
 Lichens:-

30. Soil Formation:-
1. Over many years, weathering and erosion
will cause the formation of soil.
2. Soil is the loose, weathered material on
the Earth’s surface in which plants can
grow.
3. Soil forms as rock is broken down by
weathering and mixes with other
materials on the surface.

31. Factors affecting soil formation:-
1. Parent material:
2. Slope:
3. Living organism:
4. Climate:
5. Time:

32. Thanks