1. Warm-up

2. Soil and Weathering Test Review

3. Weathering and Erosion
Order
Weathering
Erosion
Deposition
Weathering breaks down the rocks, erosion moves the particles, and deposition drops the sediments in another location.
Badlands National Park, South Dakota

4. Arches National Park, Utah
Weathering
The process in which water, ice, and heat break down rock into smaller pieces, called sediments.
Arches National Park, Utah

5. Mechanical (physical) Weathering
Physical Weathering – the breakdown of rocks and minerals into smaller pieces without a change in chemical composition.
Frost Wedging and Root/Plant Wedging
Exfoliation
Abrasion

6. Mechanical (physical) Weathering
Frost Wedging - alternate freezing & thawing of water
Root/plant wedging – plant roots growing into existing joints and fractures.

7. Exfoliation- outer layers of rock get stripped away over time
Abrasion- when rocks rub against each other

8. Badlands National Park, South Dakota
Chemical Weathering
The breakdown of rocks and minerals into smaller pieces by chemical action.
Badlands National Park, South Dakota
7 Colors Hill, Argentina

9. Chemical Weathering
Oxidation- when oxygen unites chemically with a mineral. Ex. Rust (iron oxide)
Hydration- when water unites chemically with minerals.

10. Rates of Weathering
Climate- the average weather of a location over time (precipitation and temperature)
Surface area - If particle size goes down then weathering rate goes up

11. Rock type and composition
Rates of Weathering
Rock type and composition
Different minerals weather at different rates.
Hard rocks weather slowly
Soft rocks weather quickly

12. Erosion and Deposition
Erosion – the removal and transport of weathered material by:
Wind
Gravity
Glaciers
Running water
Living Things
Deposition –The process in which sediment is dropped and comes to rest

13. Erosion Wind Erosion– hot and dry areas especially
Glacial Erosion– scrape and gouge, carry debris

14. Erosion
Rill erosion – caused when water runoff is heavy (after rainfall)
Gully Erosion – removal of large amounts of soil by heavy rainfall

15. Soil
Soil- made primarily of particles of rocks, minerals, and humus – decaying organic matter.
Horizons- The layers of soil

16. Residual soil - Soil formed from the rock material beneath the soil.
Transported soil - Soil that has been moved from its place of origin.

17. Soil Horizons
Topsoil- (A horizon) the top layer of mature soil containing organic matter and the most weathered rock.
Subsoil - (B horizon) the layer below the topsoil made of partly weathered rock, clay sized particles, and very little organic matter.
Bedrock- (C horizon) rock layer underneath useable soil
Parent Material

18. Not all horizons may be present!
Humus- (O horizon) dead material on top of the soil column. Rich in nutrients.
Not all horizons may be present!

19. Soil Profile: The vertical sequence of soil layers.
Soil is the result of weathering and biological activities. Humus “improves” the soil texture and helps it to hold water. Can take 100 years for 1 cm of soil to form!

20. Soil Texture: classified according to % of the various sized grains: clay, silt, and sand.
Sand- any rock particle less than 2 mm but more than 0.05 mm
Silt - any rock particle less than 0.05 mm but more than .002 mm
Clay- any rock particle smaller than .002 mm

21. 30% Clay
20% Silt
50% Sand

22. Soil Type:
Sandy clay loam

23. Soil Types Often classified based on climate: polar temperate desert
tropical
other
Climatic conditions are the main influence on soil development

24. Mass Movements All mass movements occur on a slope!
Creep - Slow, steady, downhill flow of loose materials – 3 cm/year
Slides - Rapid, downslope movement of layer of loose material
Mudflow - Swiftly moving mixtures of mud and water
Slump - Landslide along a curved surface
Avalanche - Landslides of snow
All mass movements occur on a slope!

25. Glacial Erosion Glacier: large, moving mass of ice
Weight of top layers exerts downward pressure forcing snow below to recrystallize into ice

26. If Formed in Valley:
Snow accumulation causes glacier to become heavy and to flow downhill, due to gravity
Speed affected by slope, temperature, thickness of ice and valley shape – 1mm/day

27. Valley Glaciers Carve out U-shaped valleys from bedrock
The deep depressions where carved out from valley called a cirques
More rounded – U Shape