1. Weathering
the various mechanical and chemical processes that cause exposed rock to decompose.
Or.. Making big rocks into little rocks

2. Two basic types
Chemical
Physical

3. Chemical Weathering Oxidation Hydrolosis Carbonation
Higher temperatures and higher moisture content accelerate these processes.
Involves a change in the chemistry of the rock, going from one mineral to another.

4. Oxidation
Primary a change in iron minerals – decomposing to iron oxide.
Commonly known as rust.

8. Hydrolosis. The most important chemical weathering process
Water plus feldspar minerals (what most igneous rocks are made from) under the right conditions gives you clay minerals.
Clay is then really easy to move.

11. Carbonation The natural form of acid rain. Only carbonic acid
CO2 + H2O H2CO3
Relatively slow process
Attacks primarily limestone and marble. Dissolves it!
Seeps in and along cracks in rock.
Forms Karst topography (more next week)

13. Physical Weathering Frost wedging Salt wedging
Heating/cooling (heat weathering)
Plants/animals
Exfoliation
Those pesky humans

14. Frost wedging Obviously, need freeze/thaw
Remember, water expands when it freezes (9%)
Force exerted is more than enough to fracture any rock.

18. Salt wedging Same as frost wedging, only salt instead of water.
Very dry climates.
Or.. Coastal regions where salty spray seeps in and evaporates.
Called honeycomb or tafoni weathering.

21. namibia

22. Heat weathering
More thermal expansion on the outside of rocks than the inside. Puts differential stress on the rock. Eventually rounding and busting it up like an onion.

27. Plants and animals
Directly attacking/dissolving the rocks. Lichen (technically, this is chemical weathering)
Tree roots
Burrowing animals
Moving stuff around, or directly boring into rocks

28. Lichens! A combination of algae and fungus.
Secrete an acid which dissolves rocks (chemical weathering) to be used as food.

30. Tree roots

33. Trees right next to your house are bad

37. What about human action?
Talk about some things humans do to increase weathering, both chemical and physical.