1. Weathering, Erosion, and Rivers Chapters 7 and 9

2. Weathering and Types
Weathering – The process in which rocks on Earth break down and change
Mechanical Weathering – Rocks break down into smaller pieces without changing chemical composition
Example: I usually break boulders apart with my head for fun

4. Types (continued)
Chemical Weathering - Rocks are broken down due to a chemical reaction in which the composition of the material changes
Example – Pouring acid on my face will chemically dissolve part of my face and maybe create some new components

6. More Examples of Mechanical Weathering
Frost Wedging – water seeps into the rock and then expands when frozen
Roots – tree roots dig into bedrock splitting it open
Animals – burrowing animals dig into the rock
Exfoliation – rocks that were once under pressure are exposed and expand until sheets peel off
Abrasion- particles bang into one another when moving

7. Frost Wedging

8. Tree Roots

9. Burrowing Animals

10. Exfoliation

11. Abrasion

12. More Examples of Chemical Weathering
Water – water can dissolve minerals in rocks
Oxygen – oxidation (rusting) of minerals
Carbon Dioxide – combines with water in the air to form carbonic acid (weak) which reacts with calcite (creates caves)

13. Chemical Weathering by Oxidation

14. Chemical Weathering due to Acid Rain

15. Chemical Weathering and Cave Formation

17. Factors that affect the rate of Weathering
Surface Area
Precipitation
Temperature
Rock Type

18. Surface Area

19. Precipitation and Temperature

20. Rock Type and Composition

21. Erosion Erosion is the transport of rock and sediment
Erosion takes place naturally 4 different ways
Wind
Gravity
Water
Ice

22. Wind

23. Gravity

24. Water

25. Ice

26. Soils: Result of weathering
Soil is made up of weathered rock and organic material.
Parent Material – the material in which soil is formed from.
Residual soil - soil that has bedrock as its parent material.
Transported soils – soil that has been moved from it original spot (wind, rain water, glaciers…)

27. Parent material……

28. Residual soil
Soil that has bedrock underlining it.

29. Transported soil
Soils transported from other places.

30. Mature Soil Profile…..

31. Mature Soil Profile
Soil profile – cross section of any given area of land
Top soil – the A horizon: gray to black, organic, sandy
Sub soil – the B horizon: red or brown, clay
Weathered bedrock – the C horizon: weathered parent material.

32. Soil Conservation…….
Soil erosion – the removal of topsoil by the action of running water or wind.
Reduce by:
Windbreaks – belts of trees along a field
Contour farming – crops are planted parallel to land contours
Terraces – flattened hills and slope’s.
Strip cropping – alternating crops and bare ground
No-till – plowing, planting, and fertilizing are all done at the same time.

33. Windbreaks…..

34. Contour Farming……

35. Strip cropping…….

36. No – Till…….

37. Water Cycle

38. Water Cycle Definitions
Precipitation – Rainfall
Infiltration – Rainfall entering the ground
Runoff – Water that doesn’t infiltrate and runs off the surface
Evaporation – Water entering the atmosphere from bodies of water
Transpiration – Water entering the atmosphere from vegetation
Condensation – Water cooling into liquid from gas in the atmosphere

39. 3 ways rivers transport sediment
Suspension – small particles carried within the water
Solution – minerals dissolved within the water
Bed Load – large particles dragged along the bottom

41. Erosion by Rivers Young Rivers – deepen the valley
Old Rivers – widen the valley
Meanders
Erosion takes place on the outsides of the meander
Deposition takes place on the inside of the meander

43. River Stages and Development

44. Rivers are classified as 3 different stages
Young
Mature
Old

45. Young Water moves rapidly
The water cuts downward, deepening the valley
Rapids, waterfalls, etc.
Poor drainage
Little or no flood plain

46. Mature Water slows down
The water is directed sideways, widening the valley
Meanders or curves develop
Better drainage and flood plain developed

47. Old Water moves very slowly Little gradient
Extreme meanders and oxbow lakes
Very good drainage and a wide flood plain
Rivers can rejuvenate and become young again

48. Floods

49. Terms
Flood – Occurs when water spills over the banks into the floodplain
Floodplain- Flat area of land next to the river
Natural Levee – The sediment left behind from previous floods that protect the banks
Flood Crest – The highest point the flood water reaches above normal