Surface Processes Weathering and Soils (Let’s Break it Down)

Presentation on theme: "Surface Processes Weathering and Soils (Let’s Break it Down)"— Presentation transcript:

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

3

4

5 Frost Action

6 Talus Slope

7 Kristínartindar, Skaftafellsjökull
Talus Slope in Iceland

8 Potholes

9

10

11

12 Plant Action

13 Animal Action-burrowing moles

14 Plant and Animal Action

15

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

25

26 - makes caves

27

28

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

40

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

46

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

58

59 Soil Profile