weathering and soils
DESCRIPTION
Weathering and Soils. Granite headstone in Southern Vermont. Weathering and Soils. Marble headstones in Southern Vermont. Weathering and Soils. Mechanical Weathering- the physical breakdown of rocks Chemical Weathering- reaction of rocks with water, acids, oxygen, etc. - PowerPoint PPT PresentationTRANSCRIPT
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Weathering Weathering and Soilsand Soils
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Marble headstones in Southern Vermont
Weathering Weathering and Soilsand Soils
Granite headstone in Southern Vermont
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Weathering and SoilsWeathering and Soils MechanicalMechanical Weathering- the physical Weathering- the physical
breakdown of rocksbreakdown of rocks ChemicalChemical Weathering- reaction of rocks Weathering- reaction of rocks
with water, acids, oxygen, etc. with water, acids, oxygen, etc.
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Mechanical Mechanical WeatheringWeathering
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Tectonic Tectonic JointingJointing
Mechanical WeatheringMechanical Weathering
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ExfoliationExfoliationMechanical WeatheringMechanical Weathering
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ExfoliationExfoliationMechanical WeatheringMechanical Weathering
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ExfoliationExfoliationMechanical WeatheringMechanical Weathering
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Chemical Chemical WeatheringWeathering
Solution:Solution:HH22O + COO + CO22 = =
HH22COCO33 ( H ( H++ + HCO + HCO33-- ) )
in air (acid rain)in air (acid rain) acidacid
gasgasLimestone dissolves readilyLimestone dissolves readily
CaCOCaCO33 + 2 H + 2 H++ (aq) = (aq) =
CaCa+2+2 + CO + CO22 + H + H22OO
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Chemical WeatheringChemical Weathering Solution: Karst TopographySolution: Karst Topography
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Chemical WeatheringChemical Weathering Solution: Karst TopographySolution: Karst Topography
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Chemical WeatheringChemical Weathering Karst Sinkhole- FloridaKarst Sinkhole- Florida
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Chemical WeatheringChemical Weathering Karst Sinkhole- FloridaKarst Sinkhole- Florida
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Chemical WeatheringChemical Weathering Tower Karst - ChinaTower Karst - China
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Chemical WeatheringChemical Weathering
Oxidation:Fe2SiO4 + ½ O2 = Fe2O3 + SiO2
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Chemical WeatheringChemical Weathering
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Chemical Weathering Chemical Weathering Differential WeatheringDifferential Weathering
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Chemical WeatheringChemical Weathering Differential WeatheringDifferential Weathering
Weathering can preferentially dissolve out mafics & increase the sialic component in sediments to yield “granite”
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Chemical WeatheringChemical WeatheringWhat happens when granite is weathered?
The biotite and hornblende will undergo hydrolysis to form clay, and oxidation to form iron
oxides.
The feldspars will undergo hydrolysis to form kaolinite (clay) and release Na+ and K+ ions into solution
The quartz (and muscovite, if present) will remain as residual minerals because they are very resistant to weathering.
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Idealized soil profile from a humid climate at middle latitudes
Zon
e of
Lea
chin
g
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Horizon Development and Horizon Development and Climate Climate
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Soil textural classesSoil textural classes
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Topsoil ecosystem Topsoil ecosystem in a temperate in a temperate climateclimate
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Effect of climate on soil developmentEffect of climate on soil development
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Chemical WeatheringChemical Weathering
Transported SoilsTransported Soils
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Wind-blown Glacial Wind-blown Glacial LoessLoess Deposits Deposits
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Wind-blown Glacial Wind-blown Glacial Loess DepositsLoess Deposits
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The Principal Soil TypesThe Principal Soil Types
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Effect of climate on soil typesEffect of climate on soil types
tundra soils
Precipitation
Tem
pera
ture
cold
hot hot
coollow high50 cm/yr
pedalferspedocals
laterites
tundra soils
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Principal soil types in the USAPrincipal soil types in the USA
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Effect of climate on soil typesEffect of climate on soil types
A typical pedocal with A typical pedocal with white white calichecaliche (CaCO (CaCO33) )
deposits in a shallow B deposits in a shallow B horizonhorizon
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Effect of climate on soilsEffect of climate on soils
Making Making laterite laterite bricksbricks
Temple at Temple at Angkor Angkor
Wat Wat CambodiaCambodia
(700 yrs (700 yrs old)old)
Laterite
Tundra soil
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A Newer A Newer Classification Classification of Soil Typesof Soil Types
Pf
Pc
Pf
Pf, Pc
L
Pf, L
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Rates of soil formation:Rates of soil formation:
Central USA: ~ 1 cm/100 years in very porous Central USA: ~ 1 cm/100 years in very porous and permeable rockand permeable rock
Humid N. Carolina: ~ 1 cm/5 yearsHumid N. Carolina: ~ 1 cm/5 years““
Granite may require over 1000 years for a cmGranite may require over 1000 years for a cm
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Both Ends of the Erosion ProblemBoth Ends of the Erosion Problem
Serious Serious soil erosionsoil erosion and gully and gully formation related to diversion of formation related to diversion of water runoff over a few months water runoff over a few months in central Californiain central California Sediment pollutionSediment pollution following following
heavy rains in North Carolinaheavy rains in North Carolina
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Soil DegradationSoil Degradation ErosionErosion DeforestationDeforestation Agricultural depletionAgricultural depletion Contamination - PollutionContamination - Pollution
SalinizationSalinization PesticidesPesticides Chemical additions and spillsChemical additions and spills
UrbanizationUrbanization DesertificationDesertification OvergrazingOvergrazing
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Raindrop impact: Raindrop impact: millions in a single millions in a single shower hit at ~ 30 mphshower hit at ~ 30 mph
Soil ErosionSoil Erosion
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Rill-wash and gullying in loose Rill-wash and gullying in loose and poorly-consolidated soilsand poorly-consolidated soils
Soil ErosionSoil Erosion
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Soil Lost (tons/km2/yr) % runoffWoods ~ 0 0.12Grass 10 6.5Corn 18087 42Fallow 17050 49
Soil Erosion for Various Uses
Soil ErosionSoil Erosion
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Number of dust storms during the month of March, 1936Number of dust storms during the month of March, 1936
Soil ErosionSoil Erosion
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Effects of logging in MadagasgarEffects of logging in Madagasgar
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Soil ErosionSoil Erosion
Figure 3.12:Figure 3.12: (a) a natural forested slope(a) a natural forested slope(b) the same slope following a clearcut(b) the same slope following a clearcut
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Soil ErosionSoil Erosion
Figure 3.12:Figure 3.12: (c) the same slope after conversion to farmland(c) the same slope after conversion to farmland(b) the same slope following urbanization(b) the same slope following urbanization
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Soil ErosionSoil Erosion
1968 motorcycles 1968 motorcycles first come to Deer first come to Deer
Creek near Creek near Bakersfield, CABakersfield, CA
1972 after only 4 1972 after only 4 years of ORV use years of ORV use little vegetation or little vegetation or
topsoil remainstopsoil remains
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Soil ErosionSoil ErosionORV users increased ORV users increased from 21 to 38 million from 21 to 38 million
between 1982 and 1992between 1982 and 1992
ATVs rip through a marsh in ATVs rip through a marsh in West VirginiaWest Virginia
Great Grizzly Hike, MontanaGreat Grizzly Hike, Montana
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Soil ErosionSoil Erosion
1985 photo of bulldozer and jeep tracks in 1985 photo of bulldozer and jeep tracks in Alaskan tundra made in 1946Alaskan tundra made in 1946
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Soil ErosionSoil Erosion
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Salt accumulation due to irrigation in Salt accumulation due to irrigation in an arid climate: San Fernando Valleyan arid climate: San Fernando Valley
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Worldwide Distribution of Salt-affected SoilsWorldwide Distribution of Salt-affected Soils
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Chemical Contamination of SoilsChemical Contamination of Soils
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Grain production Grain production levels off while levels off while population population continues to growcontinues to grow
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Strip-croppingStrip-croppingand and
Contour plowingContour plowing
Combating Soil DegradationCombating Soil Degradation
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Rice terraces in Rice terraces in AsiaAsia
Combating Soil DegradationCombating Soil Degradation
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No-tillNo-tillFarmingFarming
Combating Soil DegradationCombating Soil Degradation