1. Weathering
The process by which materials on or near the Earth’s surface break down and change.

2. 1. Mechanical / Physical Weathering
Refers only to the physical breakdown of matter (as opposed to chemical breakdown)
Frost Wedging: Water expands in volume by 9%. As water infiltrates cracks in rock causes additional cracking due to freeze-thaw cycles
Pressure: pressure on underlying rock is consistent until erosion, or another process, removes matter. The reduction in pressure can cause elastic energy within underlying rock to be released. This looks likes widening cracks or fractures

6. 1. Mechanical / Physical Weathering
Refers only to the physical breakdown of matter (as opposed to chemical breakdown)
Exfoliation: As pressure cycles and freeze-thaw cycles proceed, outer layers of rock can be stripped away in succession (like an onion)

8. 1. Mechanical Weathering
The rate of physical weathering is relatively high in cool climates.
Frost wedging / freeze-thaw cycles
Cool climates are not ideal for chemical reactions / dissolution

9. Pylon of Ramses II, Egypt
Cleopatra’s Needle, New York

10. Surface Area versus Volume
As rocks break down into fragments, they maintain the same volume, but increase their surface area.
Side Length
Volume
Surface Area
1 cm
1 cm3
6 cm2
2 cm
8 cm3
24 cm2
3 cm
27 cm3
54 cm2

13. 2. Chemical Weathering
Process by which rocks and minerals undergo changes in their composition and is dependent on a mineral’s chemical composition and temperature
Oxidation: reaction with oxygen.
EX Iron and Oxygen = Iron Oxide (Hematite)
Water: able to dissolve minerals and rocks. Water may also act as a medium in which reactions can occur.

15. 2. Chemical Weathering
Carbon Dioxide: when CO2 (from living and decaying organic matter) reacts with water in the atmosphere it produces carbonic acid that falls to Earth as acid precipitation which then cuts through mineral and rock.
Acid Precipitation:
Usually at pH 5.6 or below
Carbon dioxide, Sulfur dioxide

17. 2. Chemical Weathering
Rate of chemical weathering is relatively high in climates with warm temperatures, abundant rainfall and lush vegetation.
Chemical weathering has the greatest effect at, and around the equator.

19. Transportation of Weathered Materials
Erosion:
The removal of weathered rock and soil from its original location.
Running water, glacier, wind, ocean currents, and waves.
When material ‘drops’ after being eroded it experiences deposition.

20. Erosion by Water
Rill erosion: Running water cuts small channels into the side of a slope.
Gully erosion: Rill erosion eventually becomes gully erosion as the channel widens.

23. Glacial Erosion
Glaciers account for < 10% of Earth’s water, yet cover about 30% of Earth’s surface (due to expansion)
Scrape out large sections of Earth’s landscape

24. Erosion by Wind and by Living Things
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25. Try this
Complete Q: 1-5 on page 170
Complete Q: 1-4 on page 175