1. Mechanical & Chemical Weathering

2. Mechanical weathering is when rock is physically broken into smaller pieces.
The smaller pieces have the same composition as the larger pieces they came from.
Mechanical weathering works slowly. Over time, it can eventually wear away whole mountains.

4. Freezing & Thawing
Water freezes and expands that creates large cracks in the rock.

5. Animal Actions
Burrowing in the ground will loosen and break apart rocks.

6. Plant Growth
Tree roots enter cracks in rocks and force cracks farther apart

7. Abrasion
Sand and rock particles can wear away exposed rock surfaces like sand paper

8. Release of Pressure
When materials are removed from the surface of a rock, pressure is reduced. This can cause layers of rock to flake off.

9. Chemical Weathering

10. Chemical weathering can produce new materials as it breaks down rock.
Chemical weathering is the process that breaks down rock through chemical changes.
Chemical weathering can produce new materials as it breaks down rock.
Granite is made of feldspar, quartz, mica and other materials.
Chemical weathering eventually changes feldspar to clay.

11. Water
weathers rock by dissolving it.

12. Oxygen Found in the air and combines with Earth’s materials.
Combines with iron to create rust – oxidation
Can happen to rock that contains iron.

13. Carbon Dioxide Found in the air and dissolves in rain water
Creates carbonic acid.
Weathers marble and limestone.

14. Living Organisms
As plants grow, they produce a weak acid.

15. Acid Rain
Air pollution chemically reacts with water vapor in the cloud.
The acid mixes with rain drops.

16. Rate of Weathering
Some variables can affect the rate at which rock is weathered.
Type of Rock – some minerals that make up the rock weather faster than others.
Climate – weathering occurs faster in wet climates. Chemical reactions occur faster in higher temperatures
Human Activities – air pollution, factories, etc.

17. LEFT PAGE: Comparing Mechanical and Chemical Weathering
Draw a Venn diagram comparing and contrasting mechanical and chemical weathering.