1. Surface Processes Weathering and Soils (Let’s Break it Down)
(Let’s get ready to crumble!)

2. Weathering:
The breakdown of rocks into smaller particles by natural processes
Two types of weathering:
Physical(mechanical)
Chemical

5. Frost Action

6. Talus Slope

7. Kristínartindar, Skaftafellsjökull
Talus Slope in Iceland

8. Potholes

12. Plant Action

13. Animal Action-burrowing moles

14. Plant and Animal Action

16. Exfoliation

17. Exfoliation Half Dome, Yosemite Park, California
That’s a ladder with people on it

18. The view from part of the way up the ladder

19. Going up?

20. View from the top of Half Dome

21. Those cracks are caused by pressure unloading and if they break off it is called exfoliation

22. Physical weathering
Temperature changes can also cause exfoliation

23. Physical weathering
Pressure Unloading makes basalt break into pencil shapes
Devil’s Postpile, California

24. Svartifoss, Skaftafellsjökull

26. - makes caves

29. Weathering
Weathering is the breakdown of rocks into smaller particles by natural processes.
Physical (mechanical) Weathering - breaks down rocks without changing the chemical composition.
Chemical Weathering - breaks down rock by changing the chemical composition of the rock

30. Physical Weathering
FROST ACTION – water expands as it freezes, expanding cracks in rocks
Works best in moist, variable climates
Causes “talus slopes” at base of cliffs
Causes potholes

31. Physical Weathering
Abrasion – rocks rub against each other and get scratched
Often happens in streams
Particles become rounded

32. Chemical weathering
Breaks down rock by changing the chemical (mineral) composition of the rock

33. Chemical weathering Oxidation – reaction of rocks with oxygen (rust)
Not a rock

34. Rocks that are red on the outside have oxidized

35. Chemical weathering
Hydration, hydrolysis and solution – reactions of rocks with water
White tank campground, Joshua Tree National Park

36. Turns granite into weird shapes
Feldspar turns to kaolinite (clay) which loosens the other minerals so they fall off.
Turns granite into weird shapes
Skull rock, Joshua Tree National Park

37. Chemical weathering
Carbonation – carbon dioxide combines with another substance
Can dissolve rocks containing calcite, creating pits and caves

38. Chemical weathering
Organic acids – some plants secrete acids which can weather away rocks
Lichen on rock

39. Chemical weathering
Human Activity – sulfur dioxide from exhaust fumes causes acid rain which can cause chemical weathering
Cleopatra’s Needle, before and after being moved to NYC from Egypt

41. Factors affecting weathering
Climate (VERY IMPORTANT!)
Warm climates favor chemical weathering
Cold climates favor physical weathering (frost action)
The more moisture, the more weathering
Temperate (medium) climates have aspects of both warm and cold climates

42. Factors affecting weathering
This chart is in your review book on pg 132
Describe the climatic conditions which would cause strong chemical weathering.

43. Factors affecting weathering
Weathering or frost action are not taking place at location X. Explain why they do not occur under these conditions

44. Factors affecting weathering
Assume that the rate of precipitation is constant at 150 mm. During what season will the weathering rate be the greatest?

45. Factors affecting weathering
Particle Size and Surface Area
The smaller the particles of a rock, the faster they will weather
Many smaller particles have more surface area than fewer larger particles

47. Factors affecting weathering
Exposure – if a rock is not exposed to the surface it is less likely to weather
Mineral Composition – softer minerals tend to abrade quickly, some minerals will react with acids, water or oxygen
Time – the longer a rock is exposed at the surface, the more it will weather

48. HooDoo

49. HooDoo

50. HooDoo
HooDoo

51. HooDoo

52. HooDoo

53. How do you Hoodoo?

54. Products of weathering
Sediments – clay, silt, sand, pebbles, cobbles, boulders
Soil – an accumulation of weathered material, decaying organic material (called humus), water, air and bacteria
Soils develop best when there is weathering of the rock, without erosion.

55. Soils Parent material – the rock material that is forming the soil
Residual soil – soil that is forming directly over the parent material
Transported soil – soil forming from transported material (Long Island soils)

56. Soils
Soil horizons – layers of soil possessing different characteristics
Soil profile – a cross section of the soil at a particular location
Soils tend to be rich in organic material at the top, and composed mainly of weathered rock near the bedrock

57. Soil Profile

59. Soil Profile