Rocks break down over time through weathering and erosion. Weathering occurs through physical, chemical, and biological processes that break rocks into smaller pieces. Physical weathering is caused by temperature changes that induce expansion and contraction as well as freezing and thawing of water. Chemical weathering alters the chemical structure of rocks as they interact with carbon dioxide, oxygen, and acid in rainwater. Running water, wind, and glacial ice are the main agents of erosion that transport weathered materials away.

1. NAME:MISS IQRA
CLASS:8th A-B

4. NATURE OF ROCKS:
 Rocks are made up of soft minerals(e.g, gypsum and
calcite) that take a shorter time to break down.

6.  Rocks made up of granite takes longer time to be
weathered down because it is made up of quartz
material.

8. Erosion:
 Erosion refers to the removal of the weathered
materials from the area where weathering of rock had
taken place.

9. AGENTS OF EROSION:
Flowing water:
 where streams and rivers flow across the earth’s
surface ,flowing water causes erosion to take place.

11. Winds:
Wind erosion is dominant by dry areas:

13. NATURAL AGENTS OF WEATHERING:
 RUNNING WATER

14.  RAINFALL:

15. TEMPERATURE:
HOT TEMPERATURE:

16. COLD TEMPERATURE:

18. THERE ARE THREE TYPES OF WEATHERING:
 PHYSICAL WEATHERING
 CHEMICAL WEATHERING
 BIOLOGICAL WEATHERING

19. PHYSICAL WEATHERING:
 Physical weathering refers to the process whereby
rocks are break down.
 It is also known as mechanical weathering.

21. TYPES OF PHYSICAL WEATHERING:
There are three types of physical weathering.
 Alternate expansion and contraction of rocks.
 Freeze-thaw action of ice or frost shattering
 Release of pressure within rocks

22. Alternate Expansion and Contraction of Rocks:
Exfoliation:
Alternate expansion and contraction of rocks causes
the outer surface of rocks to break down into
different layers this kind of peeling away of rock's
layer is known as EXFOLIATION.

23. Reasons of Exfoliation:
 In arid regions like deserts during the day timing
rock become heated due to high temperature and
expanded with rays of sun.

25.  While in night timing rock becomes cool due
decrease in temperature and contracted with the
decrease in temperature.

27. Freeze-thaw action of ice or frost shattering:
 In mountainous areas, the temperature in the
atmosphere may drop below freezing point. This
causes water in the cracks to freeze.
 When water changes into ice, its volume increase by
10%.

29. PRESSURE RELEASE OF ROCKS:
 Disintegration of rock in parallel sheets as it expands
in response to the removal of confining stress.
 The most common mechanisms of pressure release is
removal of overlying rock by erosion.

31. BIOLOGICAL WEATHERING:
 Biological weathering refers the process whereby
rocks are breakdown through the action of plants and
animals in situ.
 The rocks slowly break down either by disintegration
or by decomposition.

34. CHEMICAL WEATHERING:
 Chemical weathering is responsible for change in
chemical structure.
 When rainwater mixes with carbon dioxide in the air
it makes carbonic acid(carbonation)
 When calcium carbonate in limestone combines with
weak carbonic acid in rain water, the limestone's
chemical composition changes to become calcium
bicarbonate.

36. AGENTS OF CHEMICAL WEATHERING:
Agents of chemical weathering are:
 Acid rain
 Oxygen
 Carbon dioxide
 Living organisms

37. Types of chemical weathering:
Oxidation:
 Minerals in rocks react chemically with rainwater or
oxygen in the atmosphere.
 Minerals expand in volume and change their
chemical composition.
 Rocks weaken and decomposed.

41. References:
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