1. Natural decomposition of rocks
Weathering
Natural decomposition of rocks

2. Evidence of Weathering
Broken sidewalks
Discolored rocks
Rust
Disintegrating statues
Sandy beaches
Caves
Soil

3. Mechanical Weathering
Breaks down rocks in size only. There is no change in composition of the rocks.

4. 1. Frost Action Also called Ice Wedging.
Water freezes and expands in the cracks of rocks, breaking them apart.

5. 2. Root Pry
Tree roots grow in cracks of rocks,
breaking them apart.

6. 3. Salt Crystals The growth of salt crystals in dry
climate can break apart rocks.

7. 4. Exfoliation Rocks will break off in layers due to a
decrease in pressure or temp. change.

8. 5. Burrows
Earthworms help break down the rocks when air and water enter their burrows.

9. Chemical Weathering
A process that changes the chemical composition while reducing it to smaller fragments.

10. 1. Carbonation
Carbonic acid forms from water and carbon dioxide mixing and can dissolve feldspar and calcite found in rocks.
CO2 + H2O = H2CO3

11. 2. Oxidation
Water and oxygen combine with iron in the rock to form iron oxide (rust).
Other metals can also be oxidized.

12. Magnesium Oxide

13. 3. Hydration
Water dissolves minerals in rock
and Carries them away.

14. 4. Plant Acids, such as
Lichens also dissolve
Rocks.

15. Organic Weathering Root pry Burrows Plant acids
When living things help break down rocks.
Root pry
Burrows
Plant acids

16. Factors Affecting Rate of Weathering
Increase in temperature
Amount of rainfall
Freezing and thawing conditions
Topography (lay of the land)
Altitude
Composition of rocks