1. CHEMICAL
WEATHERING

3.  Decomposition of rock in situ resulting
from chemical change
 Water (rain, fog, moisture, ocean etc) is
the key medium for chemical weathering.
 Common in warm humid climate (high
temperature & high rainfall)
 Weathered rocks by this process have a
dull pitted appearance

4. 1. Oxidation
2. Hydration
3. Hydrolysis
4. Carbonation
5. Solution

5.  Oxygen dissolved in
water reacts with mineral
iron in the rock
 The rock is converted to
iron oxide
 Always seen as reddish-
brown crust
 This conversion
weakened the mineral
bonding and
consequently the whole

9.  Involves in the expansion of minerals
resulting from the absorption of water
 E.g. Clay minerals are capable of absorbing
large quantities of water into their crystal
structure
 When this happen, they exerts stresses
within the rock which may eventually cause it
to break apart

11.  Involves a chemical reaction
 between hydrogen ions in water with certain
minerals in the rock
 E.g. Weakly acidic rainwater causes
feldspar to be converted into white powdery
clay (kaolin) which breaks down easily

12. Hydrolysis

13. Kaolinite mine

14.  Is a form of solution weathering
 Common in rocks composed of calcium
carbonate such as limestone and chalk
 Rainwater mixed with carbon dioxide form
carbonic acid
 The acid water change the calcium
carbonate to soluble calcium bicarbonate
which is then easily washed away

17.  Simply the
dissolving
minerals in water
 E.g Halite (rock
salt) dissolve in
water
 Quartz dissolves
at an extremely
slow rate

22. Spheroidical Weathering
 A type of chemical
weathering
 Creates rounded boulders
and domed monolith
 Typically granitic in
composition
 Rock forms at great
temperatures and pressures

26. BIOLOGICAL
WEATHERING

27.  Caused by the action living organisms
 Can lead to physical break down of rock
(Biophysical)
 Also chemical attack (Biochemical weathering)

28. 1. By plant roots
2. By animals such as rodents
and earthworms
3. By human activities

29.  By plant roots:
 When roots
penetrate
into
cracks, they
will usually
break rocks
apart

31.  By animals:
 Help to widen and
loosen the joints in
rocks and expose
underlying rocks to
weathering
processes as they
burrow through the
ground

32.  By human activities:
 Clearing of land for
cultivation
 Construction and
mining activities
 This activities break
up rocks and expose
them to the
weathering

33.  Organic acids from
dead plants and root
can help to decompose
rock
 Chelation is the effect
of organic acid on rock
 Waste and organic
acids from dead
animals help to
weather rocks
chemically

34.  Human activities:
 Industrialisation
can cause pollution
such emission of
sulphur dioxide
which can produce acid rain
 Accelerate the chemical weathering process of
hydrolysis, carbonation and solution