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Presentation on theme: "Download Study Guide."— Presentation transcript:

1 Download Study Guide

2 Weathering of Rocks Hoodoos

3 Weathering in the Rock Cycle
And Pressure Cementation Weathering/Erosion Sedimentary Rocks Sediment Weathering/Erosion Heat Erosion Pressure Weathering Heat and Pressure Metamorphic Rocks Igneous Rocks Heat Cooling Magma

4 Three Dynamic Processes of Breaking and Removing rock
Weathering - the disintegration and decomposition of rock at or near the surface Erosion Mass Wasting

5 Types of Weathering Mechanical – physical breakdown of rocks.
Chemical – decomposition of rocks by chemical reactions.

6 Mechanical Weathering makes smaller pieces


8 Mechanical Weathering
Frost Wedging Salt Wedging Biological Wedging Unloading Thermal Expansion

9 Frost Wedging

10 Types of Mechanical Weathering
Frost wedging – water penetrates into cracks, expands when it freezes. Must have: Adequate moisture Cracks in rocks Freeze/thaw cycles

11 Salt Wedging

12 Types of Mechanical Weathering
Salt wedging – growth of minerals in cracks Desert environments Water evaporates, ions in solution combine to form minerals

13 Biological Wedging

14 Types of Mechanical Weathering
Biological wedging – plant roots penetrate into cracks causing cracks to widen. Must have: Climate hospitable for plants Adequate moisture and temperature

15 removal of pressure of deep burial
Unloading removal of pressure of deep burial

16 Unloading Sheeting

17 Thermal expansion repeated daily heating and cooling of rock; heat causes expansion; cooling causes contraction.

18 Chemical Weathering Chemical alteration of minerals.
Results in new minerals and ions in solution. Water and acid are essential.

19 Types of Chemical Weathering
Hydrolysis - any reaction in which water participates. Ion Exchange – H+ replaces other cations. Dissolution - mineral completely dissolves, leaving only ions in solution. Oxidation - reaction in which elements gain or lose electrons (example: rust).

20 Carbon dioxide reacts with water to form carbonic acid (Equation 1)
Carbon dioxide reacts with water to form carbonic acid (Equation 1). Carbonic acid then dissociates to give the hydrogen ion (H+) and the hydrogen carbonate ion (HCO3-) (Equation 2). The ability of H2CO3 to deliver H+ is what classifies this molecule as an acid, thus lowering the pH of a solution.

21 Ion Exchange Carbon Dioxide + Rain Becomes Acid Dissolves Minerals
Leaves ----Clay Carries away--- Ions Silica

22 Certain minerals dissolve in water
Dissolution Certain minerals dissolve in water



25 Oxidation Iron Silicate dissolves Iron Oxidizes
Oxidized Iron combines with Water Leaves Iron Oxide

26 Relative susceptibility To weathering


28 Factors influencing Weathering Rates
Rock Structures – chemical/mineral composition, Physical features Topography Climate

29 Spheroidal Weathering

30 Elephant Rock State Park, MO


32 Results of Weathering

33 Result of Weathering Regolith – a loose layer of broken rock and mineral fragments. Dissolved ions

34 Benefits of Weathering
Creates soil Produces clay, sand, and gravel Produces minerals

35 Erosion and Transport

36 Erosion – transport of unconsolidated Earth material from one place to another
Modes of Transport Water Wind Ice Gravity

37 Erosion by Water Removal of regolith
Loose material is easily picked up by flowing water. Downcutting of stream channel Sediments abrade stream bottom, dislodging pieces of bedrock

38 Headward Erosion

39 Headward Erosion

40 Transport by Water Saltation – particles move downstream in short jumps. Bed load – material transported by saltation Suspended load – material carried in water for long distances.

41 Transport by Water

42 Erosion by Wind Deflation - Loose material can be picked up by wind
Abrasion - Windblown sediments can "sandblast" rocks.

43 Erosion by Wind Abrasion – airborne particles chip off small fragments of other rocks.

44 Transport by Wind Same processes as water – saltation, bed load and suspended load.

45 Transport by Wind Deflation – removal of small, loose particles. Can form desert pavement.


47 Erosion by Ice Plowing – loose material is "bulldozed"
Plucking – pieces of bedrock are pried loose. Abrasion – pieces of rock in the ice grind against bedrock below.

48 Abrasion and Plucking

49 Transport by Ice

50 Particle size and method of Transport
Water – smallest particles to small boulders. Wind – smallest particles to sand size. Ice – smallest particles to boulders as big as a house.

51 Mass Wasting Transport by gravity
The downslope movement of unconsolidated Earth material due to gravity.


53 What is mass wasting? What causes mass wasting? Why is it important to know about mass wasting? What can be done to control mass wasting?



56 Watch for fallen Rocks


58 Slope Failures - Slump

59 Slump


61 Creep

62 Creep

63 Creep

64 Stability reduced by: Adding water to the material of a slope
Increasing the steepness of the slope Removing material from the lower part of the slope Earthquakes Removal of vegetation

65 What is mass wasting? What causes mass wasting? Why is it important to know about mass wasting? What can be done to control mass wasting?

66 Engineering Solutions
Rock Nets

67 Soil Nailing

68 Avalanche Barriers Switzerland

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