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WEATHERING

WEATHERING. Definition: The physical and chemical processes that break down rock on earth’s surface. 2 Types of Weathering. PHYSICAL/ MECHANICAL WEATHERING – rocks are fractured and broken apart increasing the surface area. Initial product = Final product

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WEATHERING

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  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 • 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

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

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

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

  15. PHYSICAL WEATHERING - EXFOLIATION

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

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

  18. 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

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

  20. 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

  21. Question #9 from January ’07 exam

  22. WHICH DIAGRAM IS AN ARID CLIMATE? HUMID CLIMATE? A B

  23. Question #27 from the August ’04 exam

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

  25. YOU MIGHT ALSO SEE IT LIKE THIS.

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

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

  28. SOIL HORIZONS Layers that develop as a result of the weathering processes, biologic activity, and leaching (flow of water through rocks)

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

  30. 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

  31. Question #25 from the August ’06 exam

  32. TRANSPORTED SOILS DUE TO …

  33. FERTILE SOIL IS EXTREMELY VALUABLE FOR FOOD PRODUCTION

  34. 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

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