Geology: Processes, Hazards, and SoilsGeology: Processes, Hazards, and Soils

Brian Kaestner

Saint Mary’s Hall

Brian Kaestner

Saint Mary’s Hall

Thanks to Miller and ClementsThanks to Miller and Clements

Geologic ProcessesGeologic Processes

Structure ofthe Earth

Structure ofthe Earth

Mantle

Core

Crust

Low-velocity zone

Solid

Outer core(liquid)

Innercore(solid)

35 km (21 mi.) avg., 1,200˚C

2,900km(1,800 mi.)3,700˚C

5,200 km (3,100 mi.), 4,300˚C

10 to 65km

100 km

200 km

100 km (60 mi.)200 km (120 mi.)

Crust

Lithosphere

Asthenosphere(depth unknown)

Fig. 10.2, p. 212

Composition of Earth’s CrustComposition of Earth’s CrustEarth’s CrustEarth’s Crust

Oxygen 46.6%Oxygen 46.6%

Silicon 27.7%Silicon 27.7%

All others 1.5%All others 1.5%

Magnesium 2.1%Magnesium 2.1%

Potassium 2.6%Potassium 2.6%

Sodium 2.8%Sodium 2.8%

Calcium 3.6%Calcium 3.6%

Iron 5.0%Iron 5.0%

Aluminum 8.1%Aluminum 8.1%

Fig. 10.4, p. 213

Features of the CrustFeatures of the Crust

Oceanic crustOceanic crust(lithosphere)(lithosphere)

AbyssalAbyssalhillshills AbyssalAbyssal

floorfloorOceanicOceanic

ridgeridgeTrenchTrench

VolcanoesVolcanoes

Folded mountain beltFolded mountain belt

CratonCraton

Mantle (lithosphere)Mantle (lithosphere)

Mantle (asthenosphere)Mantle (asthenosphere)

Ab

ys

sa

l p

lain

Continental crust(lithosphere)

MantleMantle(lithosphere)(lithosphere)

Continentalrise

Continentalslope

Continentalshelf

Abyssal plain

AbyssalAbyssalfloorfloor

Fig. 10.3, p. 213

Fig. 10.5b, p. 214

EURASIAN PLATE

CHINASUBPLATE PHILIPINE

PLATE

INDIAN-AUSTRLIAN PLATE

PACIFICPLATE

JUAN DEFUCA PLATE

COCOSPLATE

CARIBBEAN PLATE

NORTHAMERICAN

PLATE

SOUTHAMERICAN

PLATE

EURASIAN PLATE

ANATOLIAN PLATE

ARABIAN PLATE

AFRICAN PLATE

AFRICAN PLATE

CarlsbergRidge

Southwest IndianOcean Ridge

ANTARCTIC PLATE

Transformfault

East PacificRise

Transformfault

Mid-IndianOceanRidge

Southeast IndianOcean Ridge

Mid-AtlanticOceanRidge

ReykjanesRidge

Transformfault

Divergent ( ) andtransform fault ( )boundaries

Convergentplate boundaries

Plate motionat convergentplate boundaries

Plate motionat divergentplate boundaries

Internal EarthProcessesInternal EarthProcesses

Plate tectonicsPlate tectonics

Divergent boundaryDivergent boundary

Convergent boundaryConvergent boundary

Subduction zoneSubduction zone

Transform faultTransform fault

Ring of FireRing of Fire

Lithosphere

AsthenosphereOceanic ridge at a divergentOceanic ridge at a divergentplate boundaryplate boundary

Lithosphere

TrenchTrench Volcanic island arcVolcanic island arc

Asthenosphere

Risingmagma

Subductionzone

Trench and volcanic island arc atTrench and volcanic island arc ata convergent plate boundarya convergent plate boundary

Fracture zoneFracture zone

Transformfault

Lithosphere

Asthenosphere

Transform fault connecting twoTransform fault connecting twodivergent plate boundariesdivergent plate boundaries

Fig. 10.6, p. 215Refer to Fig. 10-5 p. 214

Fig. 10.6a, p. 215

Lithosphere

Asthenosphere

Oceanic ridge at a divergent plate boundary

Fig. 10.6b, p. 215

Lithosphere

Trench Volcanic island arc

Asthenosphere

Risingmagma

Subductionzone

Trench and volcanic island arc at a convergentplate boundary

Fig. 10.6c, p. 215

Fracture zone

Transformfault

Lithosphere

Asthenosphere

Transform fault connecting two divergent plate boundaries

Fig. 10.7, p. 216

Dunes Lagoon

SpitsStream

Glacier

Lake

Tidalflat

Barrierislands

Shallow marineenvironment

Volcanicisland

Coral reef

Abyssal plain

Deep-sea fan

Continental shelf

Continental slope

Continental rise

DeltaDunes

Beach

Shallow marineenvironment

External Earth ProcessesExternal Earth Processes

Erosion Erosion

Mechanical weatheringMechanical weathering

Frost wedgingFrost wedging

Chemical weatheringChemical weathering

Refer to Fig. 10-7 p. 216Refer to Fig. 10-7 p. 216

Minerals and RocksMinerals and Rocks

Mineral (diamond, bauxite)Mineral (diamond, bauxite)

Rock TypesRock Types

Igneous (granite, lava)Igneous (granite, lava)

Sedimentary (limestone, sandstone)Sedimentary (limestone, sandstone)

Metamorphic (marble, slate)Metamorphic (marble, slate)

The Rock CycleThe Rock Cycle

Igneous RockGranite, Pumice,

Basalt

Sedimentary RockShale, Sandstone,

Limestone

Metamorphic RockSlate, Quartzite,

Marble

Magma(Molten Rock)

WeatheringWeathering

ErosionErosion

TransportTransport DepositionDeposition

External ProcessesInternal ProcessesExternal ProcessesInternal Processes

Heat,Pressure

Heat,Pressure

Heat,

Pressure

Heat,

Pressure

Fig. 10.8, p. 217

Natural Hazards: EarthquakesNatural Hazards: Earthquakes

Features Features

Magnitude Magnitude

Aftershocks Aftershocks

Primary effects Primary effects

Secondary effects Secondary effects

Liquefaction ofLiquefaction ofrecent sedimentsrecent sedimentscauses buildingscauses buildingsof sinkof sink

Landslides mayLandslides mayoccur onoccur onhilly groundhilly ground

ShockShockwaveswaves

EpicenterEpicenter

FocusFocus

Two adjoining platesTwo adjoining platesmove laterally alongmove laterally alongthe fault linethe fault line

Earth movementsEarth movementsCause flooding inCause flooding inLow-lying areasLow-lying areas

Fig. 10.9, p. 217

Expected Earthquake DamageExpected Earthquake Damage

CanadaCanada

United StatesUnited States

No damage expectedNo damage expected

Minimal damageMinimal damage

Moderate damageModerate damage

Severe damageSevere damage

Fig. 10.10, p. 218

Natural Hazards: Volcanic EruptionsNatural Hazards: Volcanic Eruptions

extinctvolcanoes

magmareservoir

centralvent

magmaconduit

SolidSolidlithospherelithosphere

Upwellingmagma Partially moltenPartially molten

asthenosphereasthenosphere

Fig. 10.11, p. 218See Spotlight p. 219

Fig. 10.5a, p. 214Volcanoes Earthquakes

Soils: FormationSoils: Formation

Soil horizonsSoil horizons Soil profile Soil profile Humus Humus

O horizonO horizonLeaf litterLeaf litter

A horizonA horizonTopsoilTopsoil

B horizonB horizonSubsoilSubsoil

C horizonC horizonParentParent

materialmaterial

Mature soilMature soil

Young soilYoung soil

RegolithRegolithRegolithRegolith

BedrockBedrockBedrockBedrock

Immature soilImmature soil

Fig. 10.12, p. 220

Fig. 10.13, p. 221

Flatworm

Rove beetle

AntCentipede

Mite

Pseudoscorpion

Groundbeetle

Adultfly

Millipede

Flylarvae

Sowbug

Mite

Earthworms

Slug

Snail

Roundworms

Protozoa

Bacteria

Organic debris

BeetleMites

Fungi

Springtail

Actinomycetes

Soil PropertiesSoil Properties

Infiltration Infiltration

Leaching Leaching

Porosity/permeability Porosity/permeability

Texture Texture

Structure Structure

pH pH

100%clay100%clay

IncreasingIncreasingpercentage siltpercentage silt

IncreasingIncreasingpercentage claypercentage clay

00

2020

4040

6060

8080

8080

6060

4040

2020

00100%sand100%sand 8080 6060 4040 2020 100%silt100%silt

Increasing percentage sandIncreasing percentage sand

Fig. 10.16, p. 224

Water Water

High permeability Low permeability

Fig. 10.17, p. 224

Fig. 10.17, p. 224

Water Water

High permeability Low permeability

Fig. 10.16, p. 224

100%clay

Increasingpercentage silt

Increasingpercentage clay

0

20

40

60

80

80

60

40

20

0

100%sand 80 60 40 20 100%silt

Increasing percentage sand

sandyclay

clay

siltyclay

silty clayloam

clayloam

loam siltyloam

silt

sandy clayloam

sandyloam

loamy sandsand

Table 10-1 p. 225Table 10-1 p. 225

Texture Nutrient Infiltration Water-Holding Aeration TilthCapacity Capacity

Clay Good Poor Good Poor Poor

Silt Medium Medium Medium Medium Medium

Sand Poor Good Poor Good Good

Loam Medium Medium Medium Medium Medium

Fig. 10.15b, p. 223

Fig. 10.15a, p. 223

Weak humus-mineral mixture

Mosaicof closelypackedpebbles,boulders

Dry, brown toreddish-brownwith variableaccumulationsof clay, calciumcarbonate, andsoluble salts

Desert Soil(hot, dry climate)

Grassland Soil(semiarid climate)

Alkaline,dark,and richin humus

Clay,calciumcompounds

Fig. 10.15b, p. 223

Acidiclight-coloredhumus

Iron andaluminumcompoundsmixed withclay

Forest litterleaf mold

Humus-mineralmixture

Light, grayish-brown, silt loam

Dark brownFirm clay

Acid litterand humus

Humus andiron andaluminumcompounds

Light-coloredand acidic

Tropical Rain Forest Soil(humid, tropical climate)

Deciduous Forest Soil(humid, mild climate)

Coniferous Forest Soil(humid, cold climate)

Areas of serious concern

Areas of some concern

Stable or nonvegetative areas

Global Soil ErosionGlobal Soil Erosion

Fig. 10.19, p. 226

Fig. 10.20, p. 227

Colorado Kansas

DustBowl

Oklahoma

New Mexico

Texas

MEXICO

Soils: DegradationSoils: Degradation

DesertificationDesertification

Salinization Salinization

WaterloggingWaterlogging

EvaporationTranspiration

Evaporation

Waterlogging

Less permeableclay layer

Fig. 10.22, p. 229

Fig. 10.21, p. 228

Moderate Severe Very Severe

desertificationdesertification

Fig. 10.23, p. 229

Solutions: Soil ConservationSolutions: Soil Conservation

Conventional-tillageConventional-tillage

Conservation tillage Conservation tillage

Cropping methods Cropping methods

WindbreaksWindbreaks

Land ClassificationLand Classification

Refer to Fig. 10-24 p. 230Refer to Fig. 10-24 p. 230

Fig. 10.24d, p. 230

Windbreaks

Fig. 10.24c, p. 230

Alley cropping

Fig. 10.24b, p. 230

Control planting and strip cropping

Soil RestorationSoil Restoration

Organic fertilizerOrganic fertilizer

Animal manureAnimal manure

Green manureGreen manure

CompostCompost

Crop rotationCrop rotation

Commercial inorganic fertilizerCommercial inorganic fertilizer