Erosion and weathering shape Earth's surface through mechanical and chemical processes. Mechanical weathering breaks rocks into smaller pieces through freezing and thawing, plant and animal actions, and abrasion by other particles. Chemical weathering alters rocks through reactions with water, oxygen, carbon dioxide, organisms, and acid rain. These weathering processes further break down rocks, which are then transported and eroded by forces like wind, water and glaciers to form landscapes like the Grand Canyon over long periods of time.

1. Forces That Shape Our
Earth:
Weathering
And
Erosion

2. Weathering & Erosion:
 Erosion and weathering are major
forces that shape Earth’s surface.
 For example, the Grand Canyon
was formed through erosion by the
Colorado River running through it!

5. What is weathering?
Weathering: The breaking down
of rocks into smaller pieces.
1. Mechanical /Physical
2. Chemical
Hulk
Rock
Smash!

6. So what is erosion?
Erosion:
The movement
of weathered
rock by wind,
water, glaciers
& gravity

8. Types of Weathering:
Mechanical/Physical:
Rock is physically broken into smaller
pieces (larger pieces become smaller
pieces of the same rock)
Chemical:
Rock is chemically changed (like
rusting or dissolving away)

9. 5 Agents of Mechanical
Weathering:
1. Release of Pressure
2. Freezing & Thawing
3. Animal Actions
4. Plant Growth
5. Abrasion

10. Release of Pressure
 As the surface of a rock is
eroded, the rock begins to release
pressure
 Causes top layers of the rock to
crack and flake off

11. Release of pressure: rock
cracks like an egg shell

12. Freezing & Thawing
When water in the cracks
of rocks freezes it
expands causing the
crack to enlarge or get
bigger. The ice melts &
refreezes over & over,
breaking the rock apart.

13. Result of Freezing & Thawing

14. Animal Actions
Animals dig (burrow) through
the ground to make their
homes. This loosens the soil &
breaks apart rocks.

16. Plant Root Growth
Plants roots can grow into
cracks in the rock, slowly
breaking them apart.

18. Abrasion
 Sand and other rock particles in
wind, water or ice can wear
away exposed rock surfaces.
 Like sandblasting or sandpaper
on wood

21. Chemical Weathering
The process that breaks down
the surface of rock by
chemical changes.

22. 5 Agents of Chemical
Weathering
1. Water
2. Oxygen
3. Carbon Dioxide
4. Living Organisms
5. Acid Rain

23. Water
Water dissolves rock
Water is the most important
cause of chemical weathering

25. Oxygen
 Oxygen + Water + Iron = Rust
through the Chemical reaction
called Oxidation
 Rock will become crumbly, soft,
and appear reddish-brown in color

26. Rusted rock on hillside

27. Carbon Dioxide
CO2 + rainwater = Carbonic Acid
Carbonic Acid weathers softer rock
like limestone & marble as it seeps
into spaces in rock.
Ex: sinkholes, caves

29. Living Organisms
The roots of plants make a
weak acid that slowly
dissolves rocks around the
plant.

30. Lichens grow on rock

31. Acid Rain
Acid rain causes rocks to
weather very rapidly.