Chapter 16-Weathering (GEO, BIO & CIV)

8/13/2019 Chapter 16-Weathering (GEO, BIO & CIV)

1/19

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


2/19

11/26/200

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


3/19

11/26/200

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.


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)


4/19

11/26/200



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


5/19

11/26/200

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.


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.


6/19

11/26/200

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.


the role of increasing surface areathe role of increasing surface area


7/19

11/26/200


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


8/19

11/26/200

33. Chemical weathering: red means iron. Chemical weathering: red means iron


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


9/19

11/26/200

44. Physical weathering: joints in rocks. Physical weathering: joints in rocks

44. Physical weathering: tree roots. Physical weathering: tree roots


10/19

11/26/200

44. Physical weathering: frost wedging. Physical weathering: frost wedging

44. Physical weathering: exfoliation. Physical weathering: exfoliation


11/19

11/26/200


Physical weathering and erosionPhysical weathering and erosion

duration of weatheringduration of weathering

bedrock typebedrock type

climateclimate

topographytopography



12/19

11/26/200

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.


13/19

11/26/200

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


14/19

11/26/200

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


15/19

11/26/200


66. Mass wasting:. Mass wasting:the behavior of dry and wet sandthe behavior of dry and wet sand


16/19

11/26/200

66. Mass wasting:. Mass wasting:

the accumulation of rubble on a slopethe accumulation of rubble on a slope


17/19

11/26/200

Water contentWater content lubricationlubrication

liquefactionliquefaction

Triggers of mass movementsTriggers of mass movements

earthquake vibrationsearthquake vibrations

rainfall and water infiltrationrainfall and water infiltration overloadingoverloading




18/19

11/26/200

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))


19/19

11/26/200

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

Documents

Chapter 16-Weathering (GEO, BIO & CIV)