This document discusses weathering and erosion. It defines weathering as the breaking down of rocks into smaller pieces through mechanical or chemical processes. Mechanical weathering occurs via physical forces like frost wedging and does not alter the rock's composition. Chemical weathering alters the rock through chemical reactions with water, oxygen, carbon dioxide, living organisms, and acid rain. Erosion is the movement and transport of weathered rock by forces like wind, water and gravity. The Grand Canyon formed through erosion by the Colorado River over millions of years.

1. Prentice Hall
EARTH SCIENCEEARTH SCIENCE
Tarbuck Lutgens

2. Chapter
55 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!
Weathering, Soil, and
Mass Movements

3. Mechanical Weathering
5.1 Weathering
 Mechanical weathering occurs when
physical forces break rock into smaller and
smaller pieces without changing the rock’s
mineral composition.
 In nature three physical process are
especially important causes of weathering:
frost wedging, unloading, and biological
activity.

6. What is weathering?
Weathering: The breaking down
of rocks into smaller pieces.
1. Mechanical /Physical
2. Chemical

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

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

10. Mechanical Weathering
5.1 Weathering
• Reduced pressure on igneous rock
causes it to expand and allows slabs of
outer rock to break off in layers in a
process called exfoliation.
1. Release of Pressure

11. Unloading and Exfoliation
of Igneous Rocks

12. Mechanical Weathering
5.1 Weathering
2. Frost wedging
• The mechanical breakup of rock caused
by the expansion of freezing water in
cracks and crevices

13. 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.

14. Frost Wedging

15. Mechanical Weathering
5.1 Weathering
3. Biological activity
• The activity of organisms, including plants,
burrowing animals, and humans, can also
cause mechanical weathering.

16. Mechanical Weathering
5.1 Weathering
3. Biological - Plant growth
• Plants roots can grow into cracks in the rock,
slowly breaking them apart.
Plant Root Growth

17. Weathering and
Biological Activity

18. Mechanical Weathering
5.1 Weathering
4. Biological – Animal actions
Animals dig (burrow) through the ground to
make their homes. This loosens the soil &
breaks apart rocks.

20. 5.1 Weathering
5. Abrasion
Sand and other rock particles in wind,
water or ice can wear away exposed
rock surfaces.
Like sandblasting or sandpaper on
wood
Sand-Blasting

23. Chemical Weathering
5.1 Weathering
 Chemical weathering is the breaking
down of rock through chemical reactions.

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

25. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.

27. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.
2. Oxygen – Chemically changes rock
through a process called Oxidation.
Oxygen + Water + Iron = RustOxygen + Water + Iron = Rust

28. Rusted rock on hillsideRusted rock on hillside

29. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.
2. Oxygen – Chemically changes rock
through a process called Oxidation.
3. Carbon Dioxide – forms carbonic acid.

30. Chemical Weathering
5.1 Weathering
CO2 + rainwater = Carbonic Acid
Carbonic Acid weathers softer rock like
limestone & marble as it seeps into spaces in
rock.
Examples: Karst topography – caves, sinkholes

31. Chemical Weathering
5.1 Weathering
Examples: Karst topography – caves, sinkholes

32. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.
2. Oxygen – Chemically changes rock
through a process called Oxidation.
3. Carbon Dioxide – forms carbonic acid.
4. Living Organisms -
The roots of plants make a weak acid that slowly
dissolves rocks around the plant.

33. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.
2. Oxygen – Chemically changes rock
through a process called Oxidation.
3. Carbon Dioxide – forms carbonic acid.
4. Living Organisms -

34. Chemical Weathering
5.1 Weathering
 5 Agents of Chemical Weathering
1. Water – Water dissolves rock.
2. Oxygen – Chemically changes rock
through a process called Oxidation.
3. Carbon Dioxide – forms carbonic acid.
4. Living Organisms - Lichen, mosses
5. Acid Rain – rapid weathering

35. 5.1 How does Acid Rain form?

36. Acid rain dissolves granite

37. Acid rain dissolves limestone
and marble

38. Click

39. • http://classroom.synonym.com/effects-
acid-rain-cemetery-stones-19291.html
• http://www.dnrec.state.de.us/DNREC2000
/Divisions/AWM/aqm/education/airqualityL
esson6.pdf
• Summary & Quiz

40. Rate of Weathering
5.1 Weathering
Increased surface area = Increased weathering