1. Ch 14 Weathering Two Types: 1.Physical or Mechanical 2.Chemical

2. Mechanical Weathering Rock is broken down into smaller pieces by physical means. Agents: wind, water, ice, gravity, plants & animals.

3. EXFOLIATION Rocks break into curved sheets that peal away

4. Ice Wedging Water gets into cracks and freezes Freeze/Thaw cycle splits rock

5. ABRASION WIND WATER ICE Wearing away of rocks by other rock particles

6. ROOT WEDGING

7. Animals - Burrowing

9. Chemical Weathering Rock is broken down by chemical interaction with the environment.

10. OXIDATION (rusting) Elements combine with oxygen to form rust Iron bearing rocks

11. HYDROLYSIS: Minerals decompose in water as hydrogen replaces cations in feldspar (turns into clay). HYDROLYSIS : Minerals dissolve in water. LEACHING : Water carries dissolved minerals away, forms beds of aluminum (bauxite)

12. CARBONATION: Limestone caves Carbon Dioxide and water react to form carbonic acid...Carbonic acid “eats” limestone.

13. Acid Precipitation Acids formed from the burning of fossil fuels combining with atmospheric water; bad for plants & structures.

15. Factors that affect Rates of Weathering

16. DIFFERENTIAL WEATHERING Softer, less-resistant rock wears away, leaving harder resistant rock behind.

17. Bryce Canyon “Hoodoos”

18. Rock composition Sedimentary rocks containing calcites weather rapidly (limestone). Quartz containing rocks are strong and weather slowly

19. Surface area The more surface area per volume, the faster the rock’s weathering rate.

20. Fractures and Joints Increase surface area of rock Allow weathering to happen faster

21. Climates Hot/Cold climates with freeze/thaw cycles have fastest weathering rates. Hot/Dry climates weather the least.

22. Topography Elevation or slope of the land. High Elevations – cold temp, ice wedging Steep Slopes – gravity pulls rock down

23. Human Activities Mining Construction

24. Plants and Animals Roots, Burrowing, Waste (Bat Guano)