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

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Presentation on theme: "WEATHERING Definition: The physical and chemical processes that break down rock on earth’s surface. Definition: The physical and chemical processes that."— Presentation transcript:

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

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

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

5 CARBONATION Stalagmites and stalactites 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

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

14 PHYSICAL WEATHERING - ABRASION SCRAPE, GRIND AND WEAR AWAY ROCK DURING EROSION WATERWIND

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

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

20 CLIMATE CONTROLS WEATHERING PHYSICAL WEATHERING: COLD AND MOIST COLD AND MOIST ALTERNATE FREEZE / THAW ALTERNATE FREEZE / THAW CHEMICAL WEATHERING: WARM AND MOIST 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 factorsMasses of rock do not weather uniformly due to regional and local factors Results in many unusual and spectacular rock formations and landformsResults 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? AB

25 Question #27 from the August ’04 exam

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

27 YOU MIGHT ALSO SEE IT LIKE THIS.

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

29

30

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)

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


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