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Download Study Guide. Weathering of Rocks Hoodoos.

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Presentation on theme: "Download Study Guide. Weathering of Rocks Hoodoos."— Presentation transcript:

1 Download Study Guide

2 Weathering of Rocks Hoodoos

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

4 Three Dynamic Processes of Breaking and Removing rock 1.Weathering - the disintegration and decomposition of rock at or near the surface 2.Erosion 3.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 1.Frost Wedging 2.Salt Wedging 3.Biological Wedging 4.Unloading 5.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 Unloading removal of pressure of deep burial

16 Sheeting Unloading

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

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

19 Types of Chemical Weathering 1.Ion Exchange – H+ replaces other cations. 2.Dissolution - mineral completely dissolves, leaving only ions in solution. 3.Oxidation - reaction in which elements gain or lose electrons (example: rust). Hydrolysis - any reaction in which water participates.

20 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 (HCO 3 -) (Equation 2). The ability of H 2 CO 3 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 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 1.Rock Structures – chemical/mineral composition, Physical features 2.Topography 3.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 Modes of Transport 1.Water 2.Wind 3.Ice 4.Gravity Erosion – transport of unconsolidated Earth material from one place to another

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

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

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


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



61 Creep



64 Stability reduced by: 1.Adding water to the material of a slope 2.Increasing the steepness of the slope 3.Removing material from the lower part of the slope 4.Earthquakes 5. 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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