1. WEATHERING
Definition: The physical and chemical processes that break down rock on earth’s surface.

2. 2 Types of Weathering
PHYSICAL/ MECHANICAL WEATHERING – rocks are fractured and broken apart increasing the surface area.
Initial product = Final product
CHEMICAL WEATHERING – Chemical reactions dissolve minerals that were stable when the rocks were formed below the surface to types that are now stable at surface temperatures and pressure. Products have different chemical composition than the original.
Initial product ≠ Final product

3. EXAMPLES OF CHEMICAL WEATHERING
OXIDATION OCCURS when free oxygen combines chemically with metallic elements (usually iron)
AKA RUST

4. CARBONATION
Water containing carbonic acid dissolves minerals (all rain water is slightly acidic)
Most strongly affected are calcite minerals:
limestone and marble

5. CARBONATION
Stalagmites and stalactites

6. CARBONATION – SINK HOLES
Karst Topography
forms caves, caverns,
and sinkholes

7. CAVES AND SINK HOLES

8. CHEMICAL WEATHERING HYDRATION
OCCURS WHEN Water combines with minerals – most often in granite (mica and feldspars) to form CLAY

9. PHYSICAL WEATHERING FROST ACTION – FROST WEDGING
MOST IMPORTANT IN OUR CLIMATE
FROST ACTION – FROST WEDGING
ALTERNATE FREEZE AND THAW

10. ROCKS ARE CRACKED BY WATER FREEZING

11. EXAMPLES: POT HOLES AND FROST HEAVES

13. PHYSICAL WEATHERING – ROOT ACTION
PLANT ROOTS UPLIFT AND FRACTURE ROCK

14. PHYSICAL WEATHERING - ABRASION
SCRAPE, GRIND AND WEAR AWAY ROCK DURING EROSION
WATER
WIND

15. PHYSICAL WEATHERING EXFOLIATION – PEELING AWAY OF ROCK
due to unloading (reduced pressure at earth’s surface) or fluctuations in temperature. Rocks expand and crack

16. PHYSICAL WEATHERING - EXFOLIATION

17. PHYSICAL WEATHERING INCREASES SURFACE AREA
MORE CHEMICAL WEATHERING CAN OCCUR

19. WHAT KIND OF CLIMATE SUPPORTS WEATHERING?
HIGH
PPT ↑
LOW
COLD →→→→→→→→→→ HOT

20. CLIMATE CONTROLS WEATHERING
PHYSICAL WEATHERING:
COLD AND MOIST
ALTERNATE FREEZE / THAW
CHEMICAL WEATHERING:
WARM AND MOIST
IN BOTH CASES – WATER IS THE PRIMARY INGREDIENT THAT PROMOTES WEATHERING

21. Question 41 from the most recent Regents exam – August ‘07

22. Differential Weathering
Masses of rock do not weather uniformly due to regional and local factors
Results in many unusual and spectacular rock formations and landforms

23. Question #9 from January ’07 exam

24. WHICH DIAGRAM IS AN ARID CLIMATE? HUMID CLIMATE?B

25. Question #27 from the August ’04 exam

26. WHICH LAYER IS MORE RESISTANT TO WEATHERING? LEAST RESISTANT?D C B

27. YOU MIGHT ALSO SEE IT LIKE THIS.

28. THE END PRODUCTS OF WEATHERING
CALLED SEDIMENTS OR SOIL
SOIL: a combination of sediment, rock minerals, and humus (organic material)

31. SOIL – THE PRODUCT OF WEATHERING
AFTER THOUSANDS OF YEARS…

32. SOIL HORIZONS
Layers that develop as a result of the weathering processes, biologic activity, and leaching (flow of water through rocks)
O = Organic. It consists of fragments of leaf litter, twigs, roots, and other organic material lying on the surface of the soil. This layer is not present in cultivated fields.
A = Topsoil. It is usually darker than lower layers, loose, and crumbly with varying amounts of organic matter. This is generally the most productive layer of soil.
B = Subsoil. It is usually light colored, dense, and low in organic matter.
C = Parent Material. Partially decomposed parent material The unconsolidated organic and mineral material in which soil forms..
R = Bedrock. The solid rock that underlies the soil and other unconsolidated material

33. Soil Development Size and thickness of each horizon depends on:
Climate
Vegetation
Slope (gradient or incline)
Time

34. 2 TYPES OF SOIL
TRANSPORTED SOIL: SOIL CARRIED BY EROSION AND DEPOSITED ON THE BEDROCK (MOST SOIL IS TRANSPORTED)
RESIDUAL SOIL: SOIL FORMED BY THE WEATHERING OF THE BEDROCK DIRECTLY BENEATH IT

35. Question #25 from the August ’06 exam

36. TRANSPORTED SOILS DUE TO …

37. FERTILE SOIL IS EXTREMELY VALUABLE FOR FOOD PRODUCTION

38. WEATHERING SUMMARY WEATHERING IS THE BREAKDOWN OF ROCK INTO SEDIMENTS
PHYSICAL WEATHERING – INCREASES SURFACE AREA - COLD/HUMID CLIMATE
CHEMICAL WEATHERING – WARM/HUMID CLIMATE
IN BOTH CASES, WATER IS THE PRIMARY INGREDIENT