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8/13/2019 Chapter 16-Weathering (GEO, BIO & CIV)
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11/26/200
Understanding Earth
Fifth Edition
Copyright 2007 by W. H. Freeman and Company
Lecturer: H Mohammadzadeh
Assistant professors,Department of Geology, FUM
Grotzinger Jordan Press Siever
Chapter 16:
WEATHERING, EROSION,
AND MASS WASTING
Interface Between Climate and Tectonics
ChapterChapter 1616Weathering,Weathering,
Erosion,Erosion,
andand
Mass WastingMass Wasting
(Landslide):(Landslide):
InterfaceInterfaceBetweenBetween
Climate andClimate and
TectonicsTectonics
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About Weathering, etc.About Weathering, etc.
Weathering produces all the soils, clays,Weathering produces all the soils, clays,
sediments, and dissolved substances.sediments, and dissolved substances.
Erosion is the removal of sediments byErosion is the removal of sediments by
natural processes such as wind and rivers.natural processes such as wind and rivers.
Mass wasting is the downslopeMass wasting is the downslope
movement of masses of Earth materials.movement of masses of Earth materials.
Lecture Outl ineLecture Outl ine
1.1. Weathering, erosion, mass wasting, andWeathering, erosion, mass wasting, and
the rock cyclethe rock cycle
22. Controls on weathering. Controls on weathering
33. Chemical weathering. Chemical weathering
44. Physical weathering. Physical weathering
55. Soil: the residue of weathering. Soil: the residue of weathering66. Mass Wasting. Mass Wasting
77. Classification of mass movements. Classification of mass movements
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1.1. Weathering, erosion, mass wasting,Weathering, erosion, mass wasting,
and the rock cycleand the rock cycle WeatheringWeathering is the process ofis the process of
converting rock into sediment andconverting rock into sediment and
forming soils, a main process in theforming soils, a main process in the
rock cycle.rock cycle.
Erosion and mass wastingErosion and mass wasting are theare the
processes that loosen and transportprocesses that loosen and transport
soil and rock downhill.soil and rock downhill.
22. Controls on weathering. Controls on weathering
Properties of the parent rockProperties of the parent rock
various minerals weather at different ratesvarious minerals weather at different rates
a rocks structure affects its susceptibilitya rocks structure affects its susceptibility
to cracking and fragmentationto cracking and fragmentation
Other important factorsOther important factors
climate (rainfall and temperature)climate (rainfall and temperature) soil (presence or absence)soil (presence or absence)
time (length of exposure)time (length of exposure)
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22. Controls on weathering. Controls on weathering
33. Chemical weathering. Chemical weathering
Occurs when minerals reactOccurs when minerals react
with air and waterwith air and water
role of water (hydrolysis)role of water (hydrolysis)
carbon dioxide (carboniccarbon dioxide (carbonicacid)acid)
moist soilsmoist soils
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FeldsparFeldspar
MagnetiteMagnetite
BiotiteBiotite
QuartzQuartz
Granite is made upGranite is made up
of several mineralsof several minerals
that decay atthat decay at
different rates.different rates.
33. Chemical weathering:. Chemical weathering:
the disintegration of granitethe disintegration of granite
FeldsparFeldspar
MagnetiteMagnetite
BiotiteBiotite
QuartzQuartz
Cracks form alongCracks form along
crystal boundaries.crystal boundaries.
The decay progresses,The decay progresses,
and the rock weakensand the rock weakens
and disin tegrates.and disin tegrates.
33. Chemical weathering:. Chemical weathering:
the disintegration of granitethe disintegration of granite
Granite is made upGranite is made up
of several mineralsof several minerals
that decay atthat decay at
different rates.different rates.
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2 cm
2 cm
1 cm
1 cm
Large rocks have lessLarge rocks have less
surface area for chemicalsurface area for chemical
weatheringweathering
than small rocks do ,than small rocks do ,
so smaller rocks weatherso smaller rocks weather
more quickly.more quickly.
33. Chemical weathering:. Chemical weathering:
the role of increasing surface areathe role of increasing surface area
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33. Chemical weathering. Chemical weathering
Chemical stability: a speedChemical stability: a speed
control for weatheringcontrol for weathering
solubilitysolubility
rate of dissolutionrate of dissolution
relative stability of commonrelative stability of commonrockrock--forming mineralsforming minerals
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33. Chemical weathering: red means iron. Chemical weathering: red means iron
44. Physical weathering. Physical weathering
What determines how rock breaks?What determines how rock breaks?
natural zones of weaknessnatural zones of weakness
activity of organismsactivity of organisms
frost wedgingfrost wedging
exfoliationexfoliation
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44. Physical weathering: joints in rocks. Physical weathering: joints in rocks
44. Physical weathering: tree roots. Physical weathering: tree roots
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44. Physical weathering: frost wedging. Physical weathering: frost wedging
44. Physical weathering: exfoliation. Physical weathering: exfoliation
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44. Physical weathering. Physical weathering
Physical weathering and erosionPhysical weathering and erosion
duration of weatheringduration of weathering
bedrock typebedrock type
climateclimate
topographytopography
44. Physical weathering. Physical weathering
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55. Soil: the residue of weathering. Soil: the residue of weathering
Soils asSoils as geosystemsgeosystems
input materialinput material
transformations and translocationstransformations and translocations
output materialoutput material
The basic soilThe basic soil--forming processes result informing processes result in
losses (transformations) and additionslosses (transformations) and additions
(translocations).(translocations).
LossesLosses AdditionsAdditionsOrganicmaterial
Airbornedust
ChemicalsandmineralsfrombedrockLeaching
Wind
Watererosion
TRANSLOCATION
Minerals, grains,and aggregatesmay movethrough the soil.
Other mineralsprecipitate from fluids.
TRANSFORMATION
Minerals are transformedinto other minerals.
Transformation and translocationoccur throughout the soil profile.
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55. Soil: the residue of weathering. Soil: the residue of weathering
PaleosolsPaleosols ancient soilsancient soils
climate historyclimate history
ancient atmosphereancient atmosphere
history of erosionhistory of erosion
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6. Mass wasting6. Mass wasting
Mass wastingMass wasting includes all processesincludes all processes
by which masses of rock and soil moveby which masses of rock and soil move
downslope.downslope.
Mass movementMass movement occurs when theoccurs when the
force of gravity exceeds the strength offorce of gravity exceeds the strength of
the material and it moves downslope.the material and it moves downslope.
Three primary factorsThree primary factors Nature of slope materialsNature of slope materials
Unconsolidated materialsUnconsolidated materialssand and siltsand and siltrock fragments, sand, silt, and clayrock fragments, sand, silt, and clay
Consolidated materialsConsolidated materialsrockrockcompacted (cohesive) sediments and soilscompacted (cohesive) sediments and soils
Amount of waterAmount of water
Steepness and stabilitySteepness and stability
angle of slopeangle of slope
accumulation of rubbleaccumulation of rubble
breakage into large blocksbreakage into large blocks
66. Mass wasting. Mass wasting
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66. Mass wasting. Mass wasting
66. Mass wasting:. Mass wasting:the behavior of dry and wet sandthe behavior of dry and wet sand
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66. Mass wasting:. Mass wasting:
the accumulation of rubble on a slopethe accumulation of rubble on a slope
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Water contentWater content lubricationlubrication
liquefactionliquefaction
Triggers of mass movementsTriggers of mass movements
earthquake vibrationsearthquake vibrations
rainfall and water infiltrationrainfall and water infiltration overloadingoverloading
66. Mass wasting. Mass wasting
66. Mass wasting. Mass wasting
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MassMass
wasting:wasting:
afterafter
thethe
earthquakeearthquake
77. Classification of mass movements. Classification of mass movements
ThreeThree characteristics usedcharacteristics used
naturenature of materialof material
((rock or unconsolidated)rock or unconsolidated)
nature of movementnature of movement
((flow, slide, or fallflow, slide, or fall))
velocityvelocity ofof movementmovement
(slow(slow, moderate, or fast, moderate, or fast))
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ChemicalChemical weatheringweatheringConsolidated materialConsolidated material
CreepCreep
ErosionErosion
ExfoliationExfoliation
HematiteHematite
HumusHumus
JointJoint
KaoliniteKaolinite
LiquefactionLiquefaction
Mass movementMass movement
MassMass wastingwasting
PhysicalPhysical weatheringweathering
SoilSoilSoil profileSoil profile
UnconsolidatedUnconsol idated materialmaterial
Key terms and conceptsKey terms and concepts