1. 17.4 Weathering and Erosion
To do:
• Class reading: page 583 – 588.
• Individual Silent Work: Vocabulary starting page 583

2. 17.4 Weathering and Erosion
Weathering – The change in the physical form or
chemical composition 0f rock materials exposed at
Earth’s surface.
Two types of the Weathering process:
1. Physical or mechanical – it is a kind of
weathering that breaks rocks into smaller pieces
but does not alter the rocks’ chemical
composition.

3. 17.4 Weathering and Erosion
Two types of the Weathering process:
1. Physical or mechanical – it is a kind of
weathering that breaks rocks into smaller pieces
but does not alter the rocks’ chemical
composition.
a. Ice (frost wedging) – occurs when water seeps
into cracks or joints in rocks and then freezes.
When water freezes, its volume increase by
about 10% pushing the rock apart.

4. 17.4 Weathering and Erosion
a. Ice (frost wedging) – occurs when water seeps
into cracks or joints in rocks and then freezes.
When water freezes, its volume increase by
about 10% pushing the rock apart.
b. Plants (plant wedging) – occurs when roots
grow into cracks in the rocks. As the plant
grows, the roots exert a constant pressure on
the rock. The crack continues to deepen and
widen, eventually causing a piece of the rock
to break off.

5. 17.4 Weathering and Erosion
b. Plants (plant wedging) – occurs when roots
grow into cracks in the rocks. As the plant
grows, the roots exert a constant pressure on
the rock. The crack continues to deepen and
widen, eventually causing a piece of the rock
to break off.
2. Chemical Weathering- kind of weathering that
breaks down rocks by changing its chemical
composition.

6. 17.4 Weathering and Erosion
2. Chemical Weathering- kind of weathering that
breaks down rocks by changing its chemical
composition.
a. Oxidation – When certain elements, specially
metals, react with oxygen, they become
oxides and their properties change.

7. 17.4 Weathering and Erosion
a. Oxidation – When certain elements, specially
metals, react with oxygen, they become
oxides and their properties change.
- Oxidation in minerals causes minerals to
decompose or form new minerals causing
both chemical and physical appearance of
the rock to change.
b. Carbon dioxide – carbon dioxide in the air
dissolves in rainwater resulting to a carbonic
acid.

8. 17.4 Weathering and Erosion
b. Carbon dioxide – carbon dioxide in the air
dissolves in rainwater resulting to a carbonic
acid.
- Although carbonic acid is a weak acid, it
reacts with minerals, seeps into the ground
and weather rocks underground.
- Acid rain – slowly dissolves minerals caused
burning fossil fuels in cars, power stations,
factories

9. 17.4 Weathering and Erosion
- Although carbonic acid is a weak acid, it
reacts with minerals, seeps into the ground
and weather rocks underground.
- Acid rain – slowly dissolves minerals caused
burning fossil fuels in cars, power stations,
factories.
- Acid rain damages both living organisms
and non-living matter.

10. 17.4 Weathering and Erosion
- Acid rain damages both living organisms
and non-living matter.
How does pollution contribute to acid rain?
- Coal, oil and gasoline – release gases including
sulfur dioxide reacting with water in the air and
clouds to form nitric acid or nitrous acid and sulfuric
acid.

11. 17.4 Weathering and Erosion
How does pollution contribute to acid rain?
- Coal, oil and gasoline – release gases including
sulfur dioxide reacting with water in the air and
clouds to form nitric acid or nitrous acid and sulfuric
acid.
- US Act of 1970 (Clean Air Act) – reduced the release
of chemicals that cause acid rains. Acidity of rain is
greatly reduced.

12. 17.4 Weathering and Erosion
- US Act of 1970 (Clean Air Act) – reduced the release
of chemicals that cause acid rains. Acidity of rain is
greatly reduced.
Erosion – removal and transportation of weathered
and non-weathered materials by agents of erosion.
Agents of Erosion:
• running water
• Wind

13. 17.4 Weathering and Erosion
Erosion – removal and transportation of weathered
and non-weathered materials by agents of erosion.
Agents of Erosion:
• running water
• Wind
• Waves
• Ice
• underground water
• gravity.

14. 17.4 Weathering and Erosion
• Ice
• underground water
• gravity.
Notes on Erosion:
• Water erosion shapes Earth’s surface
• Water is by far the most effective physical
weathering agent.

15. 17.4 Weathering and Erosion
Notes on Erosion:
• Water erosion shapes Earth’s surface
• Water is by far the most effective physical
weathering agent.
• Rivers carry sediments that scrapes and scratch
rocks and soil in riverbanks and river bottom
• Deposition – the process of depositing
sediments on the floor of calmer portions of
rivers, lakes and sea.

16. 17.4 Weathering and Erosion
Notes on Erosion:
• Rivers carry sediments that scrapes and scratch
rocks and soil in riverbanks and river bottom
• Deposition – the process of depositing
sediments on the floor of calmer portions of
rivers, lakes and sea.
• Glaciers erode mountains
• Wind also shape landscapes

17. 17.4 Weathering and Erosion
Poster: figure 17-35 on page 588