1. Weathering and Erosion
Soil formation

2. Standards S6E5, S6CS2, S6CS3, S6CS4, S6CS5, S6CS6 S6E3, S6E5, S6CS2,

3. Weathering
2 types
Mechanical
Chemical

4. Effects of rock type Hardness of rock determines weathering rate
Chemicals in air – air pollution
Amount of water in air
Temperature of area

5. Mechanical Weathering
When rocks are broken apart by physical processes
Chemical makeup of rock stays the same

6. Pressure release
Under Earth’s surface
Rock layers break apart
Exfoliation
Layers slowly break off

7. Plants and animals Water and nutrients collect in cracks and soil
Plants grow in cracks
Animals burrow and leave tunnels and holes in ground

8. Ice wedging Water enters cracks in rock and freeze.
Expanding water causes rock to break apart
Ice melts and processes repeat.

9. Abrasion
Wearing down by friction
Moving water (river)
Rocks hitting each other
Ocean waves

10. Chemical weathering
Chemical reactions dissolve the minerals in rocks or change them into different minerals
Weakens rock

11. Dissolving
Water + carbon dioxide
Dissolves rock into new substance

12. Rusting
Iron in soil
Oxygen rusts iron
Soil is red in color

13. Natural Acids
Water mixes with carbon dioxide gas and form carbonic acid
Roots and decaying plants give off acids
Dissolve minerals in rock

14. Effects of Climate
Pattern of weather that occur in a particular area over a period of time
Cold areas – mechanical weathering – ice wedging
Warm areas – chemical weathering – rain

15. Surface area
Small pieces of rock have more surface area exposed than large rock
Allows more rock to be exposed and weathering to occur

16. 4.2 Weathering and organic soil formation
Climate
Slope of land
Type of rock
Type of vegetation
Amount of time rock has been weathering

17. Composition of Soil Rock sediment Minerals Organic plant matter
Decayed animals
Microorganisms – bacteria
Humus – decayed organisms
water

18. Soil horizons
Horizon A – top layer of soil – litter of leaves twigs and other organic material – litter prevents erosion – topsoil – dark and fertile
Horizon B – below A – lighter in color – no litter – less fertile – leaching – removal of dissolved minerals – move from A to B
Horizon C - bottom layer – thickest layer- not much organic matter-not fertile – many rocks

19. Soil types Type of soil determined Climate Region Rainfall
Types of rock

20. Observable properties of soil
Texture
Color
Pore space
Chemistry

21. Human activities affect soil

22. Land-use Farming Overgrazing of animals=desertification
Adding nutrients (organic or artificial)
Top soil erosion
Clear trees
Wind

23. Construction and development
Roads
Houses
Malls
Stores
What are some problems with this?

24. Mining
How would this affect an area?

25. Protection of soil Crop-rotation Conservation tillage Terraces
Contour plowing
Windbreaks

26. Contour plowing

27. Crop-rotation

28. Windbreaks

29. Preventing Soil Erosion
Managing crops
Plant shelter belts – protect soil from wind
Proper grazing management – arid areas farmers do not plow under vegetation – allow grazing of natural vegetation
“No-till” farming –
stalks are left as ground cover during the winter.
Farmers seed area without plowing.
Leftover stalks stop erosion, keep moisture in ground and control weeds.

30. Reduce erosion at construction sites
Cover cleared areas with mulch, mats, or plastic coverings
Water sprayed onto cleared area
New topsoil is added to exposed areas
Area is seeded and reinforced with netting or straws
Retaining walls are built for steeper areas – made of stone, concrete or wood