Weathering and Erosion

3. WEATHERING
Definition: Any of the chemical or mechanical processes by
which rocks exposed to the weather undergo changes
in character and break down.
 Agents act to physically disintegrate and chemically
decompose the rock and the minerals of the land
surface, thus freeing elements and rendering them
more mobile. This process is called weathering.

4. The breakdown do the materials of Earth’s crust
into smaller pieces.

5. WEATHERING & GRADATION
 The process by which land is leveled off
through erosion or the transportation or
deposition of sediments.
 Especially the process by which a riverbed is
brought to a level where it is just able to
transport the amount of sediment delivered to
it.

6. EXPLANATION
• Gradation
– Erosion: Removal of material
– Deposition: Filling of
depressions
– Transportation of materials
• Gradational agents
– Water, wind, ice
– All agents are powered by solar
radiation and gravity

8. Weathering process
Weathering can be divided into three
types
 MECHANICAL WEATHERING
 CHEMICAL WEATHERING
 BIOTIC WEATHERING

9. Mechanical Weathering
Rock and mineral fragments are reduced to
small size by purely physical means,
without change in composition.

10. TYPES OF MECHANICAL WEATHERING
There are many types of MECHANICAL WEATHERING
such as
 FROST WEDGING
 SALT CRYSTALLIZATION
 SHEETING
 EXFOLIATION
 SPHEROIDAL WEATHERING

11. FROST WEDGING
 A PROCESS BY WHICH WATER SEEPS INTO
ROCK JOINT, FREEZS AND WEDGES LIKE
ROCK APART.
 WATER SEEPS INTO THE ROCK
FRACTURES, EXPANDS AS IT CHANGES INTO
ICE, AND DISLODGES ROCKS. THE PROCESS
IS CALLED FORST WEDGING.

13. SALT CRYSTALLIZATION
WHEN WATER PRESENT IN THE PORES OF ROCK
EVAPORATES MINUTE SALT CRYSTALLS ARE
PRECIPITATED. THIS PROCESS IS CALLED SALT
CRYSTALLIZATION.

14. SHEETING
A TYPE OF JOINTING PARALLEL TO THE ROCK
SURFACE CAUSE BY PRESSURE RELEASE.

15. EXFOLIATION
THE FLAKING OR STRIPPING OF A ROCK BODY IN
CONCENTRIC LAYERS.

16. SPHEROIDAL WEATHERING
 THE PEELING OF A
SMALL ROCK BODIES
INTO ONIONLIKE
LAYERS

17. CHEMICAL WEATHERING
THERE ARE VARIOUS TYPES OE CHEMICAL
WEATHERING SUCH AS
 DIRECT SOLUTION
 HYDROLYSIS
 OXIDATION

18. DIRECT SOLUTION
 THIS IS A PROCESS IN WHICH SOME OF
THE MINERALS GET DISSOLVED IN WATER.
THEY ARE THEREFORE REMOVED IN
SOLUTION. ROCK SALT AND GYPSUM ARE
REMOVED IN BY THIS PROCESS.

19. HYDROLYSIS
 THIS IS A PROCESS BY WHICH WATER IS
ABSORBED BY THE MINERAL OF THE ROCK.
DUE TO THE ABSORBTION OF WATER BY
THE ROCK ITS VOLUME INCREASES AND THE
GRAINS LOSE THEIR SHAPE.
 THE REACTION BETWEEN THE
MUNERALS, ESPECIALLY SILICATES AND
WATER.

20. OXIDATION
 THIS IS A PROCESS IN WHICH
ATMOSPHERIC OXYGEN REACTS WITH THE
ROCK TO PRODUCE OXIDE IS CALLED
OXIDATION.
 RUSTING

21. RATE OF WATHERING
 THE RATE AT WHICH ROCKS DISINTIGRATE DEPNDS
BOTH ON THE TYPE OF ROCK INVOLVED AND THE
EXTERNAL FORCES TO WHICH THE ROCK S EXPOSED.
 BOWEN’S REACTION

22.  The process that breaks down rock through
chemical changes.
 The agents of chemical weathering
 Water
 Oxygen
 Carbon dioxide
 Living organisms
 Acid rain

23.  Water weathers rock by dissolving it

24.  Iron combines with oxygen
in the presence of water in
a processes called
oxidation
 The product of oxidation is
rust

25.  CO2 dissolves in rain water and creates carbonic acid
 Carbonic acid easily weathers limestone and marble

26.  Lichens that grow on rocks produce weak acids that
chemically weather rock

27.  Compounds from burning coal, oil and gas react
chemically with water forming acids.
 Acid rain causes very rapid chemical weathering

28.  The word ‘bio’ means life. Thus biotic weathering is
any type of weathering that is caused by living
organisms. Most often the culprit of biotic weathering
are plant roots. These roots can extend downward,
deep into rock cracks in search of water, and nutrients.
In the process they act as a wedge, widening and
extending the cracks.
 Other causes of biotic weathering are digging animals,
microscopic plants and animals, algae and fungi.

31. EROSION
 PROCESS OF REMOVING EARTH
MATERIALS FROM THEIR ORIGINAL SITES
THROUGH WEATHERING AND TRANSPOORT.
 THE WEARING AWAY OF THE EARTH’S
SURFACE BY ANY NATUAL PROCESS.

32. TYPES OF EROSION
THERE ARE VARIOUS TYPES OF EROSION. SOME OF
IT ARE MENTIONED HERE: WATER EROSION
 WIND EROSION
 GLACIAER EROSION
 SEA EROSION
 SOIL EROSION

33. WATER EROSION
 Water erosion occurs from the chemicals in the
water, and the force of the flow of water in the river.
There are many chemicals in the water of a river, and
those chemicals can break down certain rocks, such as
limestone or chalk.
 This eroded rock is carried down the river.
Sometimes, a crack or crevice develops. When the force
of the flowing river smashes into that crack, the rock
can break away, and again be carried down the river.

35. WATER EROSION

36. WIND EROSION
 LIGHT OBJECTS, SUCH AS ROCKS AND PEBBLES
ARE CARRIED BY THE WIND AND CAN HIT
LANDFORMS, ERODING MATERIALS OFF THEM,
THAT ARE CARRIED OFF IN THE WIND.
 WIND EROSION, THOUGH IT MAY BE SMALL
WHERE YOU LIVE, CAN TAKE QUITE A TOLL ON
AREAS OF THE WORLD COVERED IN DESERT. WIND
EROSION IS SIMPLE

38. WIND EROSION

39. GLACIER EROSION
 ICE EROSION, BESIDES THAT OF HAIL, COMES
MOSTLY IN THE FORM OF GLACIER EROSION.
GLACIERS ARE GIANT BODIES OF ICE THAT CAN
PICK UP HUGE PIECES OF ROCK, SOME EVEN AS BIG
AS HOUSES. A COMBINATION OF THE WATER, ICE,
AND PICKED UP SEDIMENT, CREATE A POWERFUL
ERODING MACHINE.
 GLACIERS CAN CARRY ALMOST ANYTHING, AND
LIKE SANDPAPER, THE SEDIMENT JUST KEEPS
INCREASING. GLACIERS ARE SUCH A POWERFUL
FORCE THAT THEY CAN CARVE VALLEYS, DEPOSIT
MORAINES, OR LEAD TO THE CREATION OF
LANDFORMS SUCH AS DELTA'S

41. GLACIER EROSION

42. SEA EROSION
 EROSION IN THE SEA ALSO OCCURS. THE SALTS
AND OTHER CHEMICALS CAN ERODE WEAK ROCKS
ON THE COAST, SUCH AS LIMESTONE AND CHALK.
THE ERODED MATERIALS ARE CARRIED UP THE
SHORE BY THE MEANS OF A LONG SHORE DRIFT.
 WAVES CRASHING AGAINST THE SHORE CAN
CREATE AIR PRESSURE INSIDE CRACKED ROCKS,
THAT CAN EVENTUALLY BREAK THEM.
FURTHERMORE, IF ROCKS, PEBBLES OR SEDIMENT IS
CARRIED IN THE WAVES, THEY CAN SMASH UP
AGAINST THE SHORE AND ERODE IT EVEN MORE.

44. SOIL EROSION
 SOIL EROSION PAYS THE BIGGEST PRICE TO
FARMERS. FLOODING, WIND ETC. CAN CARRY THE
TOPSOIL AWAY FROM FARMLANDS, AND MAKE THE
SOIL UNFERTILE.

46.  Process by which rocks are broken down into smaller
pieces by external conditions.
 Types of Physical weathering
 Frost heaving and Frost wedging
 Plant roots
 Friction and impact
 Burrowing of animals
 Temperature changes

52.  The process by which water, ice, wind or gravity moves
fragments of rock and soil.

53.  Rivers, streams, and runoff

54.  Glaciers

56.  Landslides, mudslides, slump and creep