1. Presented By:
M Sajjad (907)
Ph# +923346544625

2.  Introduction
 Definition
 Weathering vs. erosion
 Types of weathering
 Mechanical weathering
 Agents of Mechanical weathering
 Frost Action
 Pressure Release (Exfoliation)
 Insulation
 Some minor Agents of Mechanical weathering
 Chemical weathering
 Main process of Chemical Weathering
 Hydrolysis
 Oxidation
 Carbonation
 Acidic Rain
 Solution
 Biological weathering
 Mechanical weathering vs. chemical weathering
 Factors af fecting weathering
 Significance of weathering

3.  “Weathering is the process of disintegration and
decomposition of rocks of the earth’s surface”.
 Weathering Vs. Erosion

4.  Mechanical weathering
 Disintegration by physical agents
 Composition of rock does not change

5.  Frost Action
 Weathering process by ice
 Water increases in volume by about 9% when it freezes
 Produces about 1890 metric tons pressure for every 1 ft2
 Common in high altitude zones

7.  Pressure Release (Exfoliation)
 Metamorphic and intrusive igneous rocks are under
pressure
 Upper layer is removed by erosion
 Due to pressure release the cracks are formed

9.  Insolation
 Common in arid and desert regions
 Temperature is high in day time and low in night
 Disintegration due to expansion and contraction
 Block Disintegration
 Granular disintegration

11.  Rainfall
 Gravity
 Salt wedging

12.  Weathering process by chemical agents
 Composition of rocks is changed

13. These weathered tombstones are from a burying ground in
Boston, Massachusetts. The marker on the left, carved in marble,
has been strongly weathered, weakening the lettering. The
marker on the right, made of slate, is much more resistant to
erosion.

14.  Hydrolysis
 Addition of water
 When minerals are moistened, hydrolysis occurs.
H2O + CO2 + CaCO3 --> Ca+2 + 2HCO3-
 water + carbon dioxide + calcite dissolve into calcium ion and bicarbonate ion

15. Feldspars to clay
+ H 2 CO 3 (acid)

17.  Oxidation
 Iron combines with oxygen in the presence of water in a
processes called oxidation
 The product of oxidation is rust

18.  Carbonation
 Mostly in humid areas
 CO2 dissolves in rain water and creates carbonic acid
 Carbonic acid easily weathers limestone and marble
CaCo3+H2CO3 Ca2+ + 2HCO3

19.  Acidic Rain
 Compounds from burning coal, oil and gas react chemically with
water forming acids.
 Acid rain causes very rapid chemical weathering

21.  Solution
 Rock salt and gypsum may be dissolved by water and
then removed in solution

23.  Can be both chemical and mechanical in
nature.
• roots split rocks apart
• roots produce acids
that dissolve rocks.

24. • Animal And
Insects
• Vegetation
• Human
Activities

25. MECHANICAL WEATHERING CHEMICAL WEATHERING
 Rocks are disintegrated by  Rocks are decomposed by
physical force chemical action
 There is no chemical change  Rocks undergo chemical change
 Prominent in hot and humid
 Prominent in dry and cool areas areas
 Rocks are broken into great  Only surface rocks are affected
depth  Hard rock like quartz resist
 Hard rocks are weathered too chemical weathering

26.  Nature of rock
 Slope of land
 Joints
 Vegetation cover
 Climate

27.  Landforms
 Formation of sedimentary rocks
 Mass wasting
 Regolith formation

30. Niche habitation of native Americans wall of canyon de chelly
Arizona

31. This granite outcrop in Yosemite National Park, California, displays sheetlike joints, giving a
stepped appearance to the mountain slope.

36.  Monolith
 Buttes
 Mesas

37. Monoli Mesa
th
Butte

38.  Bajwa.A.S, “Modern Physical Geography” publishers emporium Urdu Bazar
Lahore
 Strahler.A “Physical Geography” 2nd 2005
 http://www.soils.wisc.edu/courses/SS325/weathering.htm
 http://www.physicalgeography.net/fundamentals/10s.html
 http://russiatrek.org/blog/nature/the-weathering-pillars-of-komi-republic-
photos/
 http://www.allrussiantours.com/natural-attractions/pillars-of-
weathering.html