1. Weathering and Erosion

2. Mechanical Weathering Chemical Weathering

3. Examine the illustration below that shows volcanic mountain formation
Examine the illustration below that shows volcanic mountain formation. Note that the volcanoes bring new rock to the surface.

4. Weathering
Mechanical or chemical weathering is a surface process that breaks rocks into smaller pieces.
Freezing
Thawing
Oxygen in the air
Plants
Animals
Weather

5. Mechanical Weathering
Breaks rocks into smaller pieces without changing them chemically.
The small pieces are identical in composition to the original rock.
Ice wedging
Living beings

6. Ice Wedging The freezing and thawing cycle breaks up rocks.
Ice wedging occurs when water seeps into rock cracks and freezes. Interestingly, water EXPANDS when it freezes. As the water freezes in the rock crack, sections of rock are broken off. Ice wedging is common in areas where the climate includes a cold season.

7. Ice Wedging Note how the water can freeze and expand in rock cracks.

8. Plants and animals
Plants grow in inconvenient places. Their roots grow into cracks in rocks where water collects.
Roots become thicker and longer exerting pressure and wedging rock apart.

9. Note that the roots are creating large cracks in the rock.

10. Plants and animals
Gophers and prairie dogs weather rock, burrowing in the ground.
When they burrow through sediment, they break the rocks.

11. Prairie dogs burrowing into the soil
Prairie dogs burrowing into the soil. Note the small rocks that are now exposed

12. Interest Scientific Fact:
Earthworms are a major factor in the weathering of rock. Earthworms tunnel through the soil looking for food. As they tunnel, they bring rock flakes to the surface and expose covered rock to the weathering effects of air and water.

13. Earthworms

14. Abrasion
Abrasion is the grinding of rocks. Abrasion may occur because of the action of wind, running water, waves, and gravity.
Wind, running water, and waves push smaller particles of rock into other rock eventually causing pieces to chip away. Rocks fall and tumble as gravity pulls them down hill. When this happens, the rocks chip or break apart.

15. Note how the wind has weathered the rock.

16. Remember this:
Rocks are weathered when small pieces of rock are pushed across other rock or when a rock falls.

17. Abrasion

18. Abrasion
Abrasion occurs when small pieces of rocks are pushed into or across another rock. Over time this results in chipping or wearing down of the rocks.
Rocks are weathered when small pieces of rock are pushed across other rock or when a rock falls.

19. Abrasion

20. Interesting Scientific Fact:
The Grand Canyon continues to be weathered by the action of the small grains of rock that are carried along by the Colorado River.

21. Review 1 Describe how rocks are mechanically weathering.
Explain how carbonic acid weathers rocks.
Describe how soil forms. What factors are important.

22. Agents of Erosion
Erosion is the wearing away and removal of rock and sediment.
Agents:
Gravity
Ice
Wind
water

23. Gravity
Gravity is a force that pulls every object toward every other object.
Gravity pulls everything on Earth toward its center.
Mass movement is when gravity causes rock or sediment to move down a slope.

24. Mass Movement Creep process in which sediments move slowly downhill.
Common where freezing and thawing occur.

25. Creep

26. Mass Movement
Slump occurs when a mass of rock or sediment moves downhill, leaving a curve scar.

27. Slump

28. SLUMPS Slumps are: often clay-rich (cohesive unit) slow to rapid
have spoon-shaped failure surfaces
show clear scarp face at head (top)
end in earthflows at toe (bottom)

29. Slump

30. Slump

31. Mass Movement
Rock Slides layers of rock break loose from slopes and slide to the bottom.
Million of cubic meters of rock roaring down a mountain at speeds greater than 250 Km/h.

32. Rock Slides

33. Mass Movement
Mudflows where heavy rains or melting snow and ice saturate sediments.
Mudflows is a mass of wet sediment that flows downhill over the ground surface.

34. Mudflows

35. Mudflows

36. Mudflows

37. Ice Continental glaciers. Valley glaciers. Mountain glaciers.
Ice can remove rock from mountaintops.
Ice forms cirques.
Ice can remove rock layers from land’s surface.

38. Ice

39. Wind The erosion of the land by wind is called deflation.
Deflation can lower the land’s surface by several meters.
Abrasion is a form of erosion that can make pits in rocks and produce smooth, polished surfaces. ( deserts, cold regions with strong winds).

40. Wind

41. Water Water that flows over Earth’s surface is called runoff.
Runoff causes erosion, especially if water is moving fast.
Sheet erosion is a thin sheet of water can carry loose sediment grains with it, causing erosion of the land.

42. Water

43. Water