1. Weathering & Erosion

2. Does the Earth’s surface change over time?

7. What shapes the Earth’s surface over time?

8. Weathering and Erosion
Weathering - processes at or near Earth’s surface that cause rocks and minerals to break down
Erosion - process of removing Earth materials from their original sites through weathering and transport

9. What evidence of weathering do you see in this picture?

10. Types of Weathering
Mechanical (Physical) - processes that break a rock or mineral into smaller pieces without altering its composition
Chemical - processes that change the chemical composition of rocks and minerals

11. Mechanical Weathering
1. Abrasion/Scouring – wind & water

13. What evidence of weathering do you see in this picture?
Why wasn’t this mass of land weathered away?

14. Mechanical Weathering
2. Frost wedging – water expands when it freezes

15. Frost Wedging

16. Mechanical Weathering
3. Exfoliation/Unloading
As deeply buried rock is uplifted, pressure is reduced and the rock breaks off into leaves or sheets along joints

17. Enchanted Rock

18. Mechanical Weathering
4. Thermal Expansion/Contraction – repeated, daily heating (expansion) and cooling (contraction) of rock causes stress along natural boundaries in the rock

19. Mechanical Weathering
5. Plant/Animal Activity – plant roots, animal burrows

20. Mechanical Weathering
6. Crystal Growth – water evaporates leaving minerals (salt) behind; crystals grow and fracture the rock

21. Chemical Weathering
Rock reacts with water, gases and solutions which add or remove elements from minerals

22. Chemical Weathering 1. Oxygen
Iron combines with oxygen in the presence of water in a processes called oxidation. The product is rust.

26. Chemical Weathering 2. Carbon Dioxide
CO2 dissolves in rain water and creates carbonic acid which easily weathers limestone and marble

27. Acid rain has eaten away this limestone statue

28. Chemical Weathering 3. Biological Activity
Lichen that grow on rocks produce weak acids that chemically weather rock

29. Erosion is caused by…
1. Water – Rain, Streams, Oceans, Ice

30. Erosion is Caused by…
2. Wind

31. Erosion is Caused by…
3. Gravity

32. Mass Wasting
Movement of large amounts of material downhill under the influence of gravity
Creep
Solifluction
Mudflow
Earthflow
Slump
Rockfall
Avalanche

33. Soil Creep

34. Creep

35. Slump
scarp

36. Slump near Fargo, ND

37. Mass Wasting in Haiti

40. Earthflow

41. Rockfalls, Yosemite, California

42. Triggers for rapid Mass Wasting
Rain
Over-steepening
cutting at foot of slope
piling on head of slope
Deforestation / Devegetation
Earthquakes