Geology: Processes, Hazards, and Soils

Geology: Processes, Hazards, and Soils

Chapter 10

G. Tyler Miller’sLiving in the Environment

13th Edition

Chapter 10

G. Tyler Miller’sLiving in the Environment

13th Edition

Geologic StructureGeologic Structure

Earth’s internal structur

e

Earth’s internal structur

e

Fig. 10-2 p. 204Fig. 10-2 p. 204

Structure of EarthStructure of Earth

Structure of EarthStructure of Earth• Inner Core/Outer Core – Inner Core/Outer Core –

magma/molten rock with intensely magma/molten rock with intensely hot metals, mostly Fehot metals, mostly Fe

• Mantle – pliable, hot enough to bend Mantle – pliable, hot enough to bend like taffy, less dense than core as it like taffy, less dense than core as it contains lighter elements (Ocontains lighter elements (O22, Si, Mg), Si, Mg)

• Crust – floats atop mantle, consisting Crust – floats atop mantle, consisting of oceanic and continental crustof oceanic and continental crust

Hard Boiled EggHard Boiled Egg

Eight Most Common Chemical Elements (%)Eight Most Common

Chemical Elements (%)WHOLE EARTHWHOLE EARTH CRUSTCRUST

IronIron 33.333.3 OxygenOxygen 45.245.2

OxygenOxygen 29.829.8 SiliconSilicon 27.227.2

SiliconSilicon 15.615.6 AluminumAluminum 8.28.2

MagnesiumMagnesium 13.913.9 IronIron 5.85.8

NickelNickel 2.02.0 CalciumCalcium 5.15.1

CalciumCalcium 1.81.8 MagnesiumMagnesium 2.82.8

AluminumAluminum 1.51.5 SodiumSodium 2.32.3

SodiumSodium 0.20.2 PotassiumPotassium 1.71.7

Features of the CrustFeatures of the Crust

Oceanic crust(lithosphere)

Abyssalhills Abyssal

floorOceanic

ridgeTrench

Volcanoes

Folded mountain belt

Craton

Mantle (lithosphere)

Mantle (asthenosphere)

Ab

ys

sa

l p

lain

Continental crust(lithosphere)

Mantle(lithosphere)

Continentalrise

Continentalslope

Continentalshelf

Abyssal plain

Abyssalfloor

Lithosphere = oceanic + continental crust

Asthenosphere = mantle

Internal Earth ProcessesInternal Earth Processes

• Geological changes originating from the Geological changes originating from the earthearth’’s interiors interior– Residual heat from the earthResidual heat from the earth’’s cores core– Radioactive decay in the earthRadioactive decay in the earth’’s crusts crust

• Convection cellsConvection cells• Mantle plumesMantle plumes

Tectonic plate

Collision between two continents

Oceanic tectonicplate

Spreading center Oceanic tectonic

plateOcean trench

Plate movement Plate movement

Continentalcrust

Subductionzone

Oceaniccrust

Oceaniccrust

Continentalcrust

Mantle

Innercore

Hot outercore

Two plates movetowards each other.One is subductedback into the mantleon falling convectioncurrent.

Mantleconvectioncell

Hot materialrisingthroughthe mantle

Material coolsas it reachesthe outer mantle

Cold densematerial fallsback throughmantle

Plate Tectonics p. 208Plate Tectonics p. 208• Theory explaining the movement of

tectonic plates and the processes that occur at their boundaries.– more commonly referred to as

“continental drift” theory– Plates slide across surface of Earth and

can break or collide– Plate Boundary = area where two

plates meet

EURASIAN PLATEEURASIAN PLATE

CHINACHINASUBPLATESUBPLATE PHILIPPINEPHILIPPINE

PLATEPLATE

INDIAN-AUSTRLIAN PLATEINDIAN-AUSTRLIAN PLATE

PACIFICPLATE

JUAN DEJUAN DEFUCA PLATEFUCA PLATE

COCOSPLATE

CARIBBEANCARIBBEAN PLATEPLATE

NORTHNORTHAMERICANAMERICAN

PLATEPLATE

SOUTHSOUTHAMERICANAMERICAN

PLATEPLATE

EURASIANEURASIAN PLATEPLATE

ANATOLIANANATOLIAN PLATEPLATE

ARABIANARABIAN PLATEPLATE

AFRICANAFRICAN PLATEPLATE

SOMALIAN SUBPLATE

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

Tectonic Plate BoundariesTectonic Plate Boundaries

Divergent boundary

Divergent boundary

Convergent boundary•Subduction zone

Convergent boundary•Subduction zone

Transform fault

Transform fault

LithosphereLithosphere

AsthenosphereAsthenosphere

Plates move apart, forms as mantle magma forms oceanic crust, occurs along ocean basins

EX: Mid Atlantic Ridge, East Pacific Rise

Divergent BoundaryDivergent Boundary

LithosphereLithosphere

Trench Volcanic island arc

AsthenosphereAsthenosphere

RisingRisingmagmamagma

SubductionSubductionzonezone

Convergent BoundaryConvergent Boundary

Plates collide, resulting in subduction OR mtn building, occurs at plate boundaries

EX: Indian Plate, Western South America

Transformfault

LithosphereLithosphere

AsthenosphereAsthenosphere

Transform Faults

Plates slide past each other in opposite but parallel directions, occurs along Fault Lines

EX: San Andreas Fault

Volcanoes Earthquakes

Ring of Fire

Natural Hazards: EarthquakesNatural Hazards: Earthquakes• FeaturesFeatures

– Shock wavesShock waves– Focus and epicenterFocus and epicenter

• MagnitudeMagnitude– Richter ScaleRichter Scale– 1 (insignificant) to 1 (insignificant) to 9 (great) 10X9 (great) 10X

• AftershocksAftershocks• Primary EffectsPrimary Effects

– shakingshaking

• Secondary EffectsSecondary Effects– Rockslides, fires, and floodingRockslides, fires, and flooding– tsunamistsunamis

Expected Earthquake DamageExpected Earthquake Damage

Fig. 10-10 p. 211Fig. 10-10 p. 211

CanadaCanada

United StatesUnited States

No damage expectedNo damage expected

Minimal damageMinimal damage

Moderate damageModerate damage

Severe damageSevere damage

Natural Hazards: Volcanic LocationsNatural Hazards: Volcanic Locations• Volcanic Eruptions occurs at three

geographic locations p. 207

1. Subduction Zones = Pacific Basin Ring of Fire

2. Spreading Centers (Ocean Ridges) = Iceland

3. Hot Spots = rising plume of magma that flowed from crack in crust, Hawaiian Islands

Natural Hazards: Volcanic EruptionsNatural Hazards: Volcanic Eruptions

• Ejecta (rock and ash)

• Molten lava

• Gases

extinctvolcanoes

extinctvolcanoes

magmareservoir

centralvent

magmaconduit

SolidlithosphereSolidlithosphere

Upwellingmagma

Partially moltenasthenosphere

ROCK CYCLE REVIEWROCK CYCLE REVIEW

Rock CycleRock Cycle• Cycle of creation, destruction, and

metamorphosis.– Three major rock classifications:

•IgneousIgneous•SedimentarySedimentary•MetamorphicMetamorphic

Minerals and RocksMinerals and Rocks

• MineralsMinerals– Naturally occurringNaturally occurring– Crystalline structureCrystalline structure– InorganicInorganic– SolidSolid

• Rocks – solid, cohesive, aggregate of one Rocks – solid, cohesive, aggregate of one or more crystalline mineralsor more crystalline minerals– Igneous (granite, lava)Igneous (granite, lava)– Sedimentary (limestone, sandstone)Sedimentary (limestone, sandstone)– Metamorphic (marble, slate)Metamorphic (marble, slate)

Igneous RockGranite, Pumice,

Basalt

Sedimentary RockShale, Sandstone,

Limestone

Metamorphic RockSlate, Quartzite,

Marble

Magma(Molten Rock)

WeatheringWeathering

ErosionErosionTransportTransport

DepositionDeposition

Internal ProcessesInternal Processes

External ProcessesExternal ProcessesHeat,Heat,

PressurePressure

Heat,Heat,

PressurePressure

LithificationLithification

External Earth ProcessesExternal Earth Processes

• Weathering – breakdown of solid rockWeathering – breakdown of solid rock– Mechanical (physical) weatheringMechanical (physical) weathering

• Frost wedging, freeze thaw cycleFrost wedging, freeze thaw cycle– Chemical weatheringChemical weathering

• Oxidation (losing or gaining of electrons)Oxidation (losing or gaining of electrons)• Hydrolysis (splitting of water)Hydrolysis (splitting of water)

• Erosion – process by which earth Erosion – process by which earth particles are moved from one place particles are moved from one place and deposited in anotherand deposited in another– WindWind– WaterWater– IceIce– GravityGravity

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

Landforms resulting from Landforms resulting from external processesprocesses

SoilSoil• Complex mixture of …

– eroded rock– mineral nutrients– decaying organic matter– water– air– micro-organisms

• Renewable resource– Weathering of rocks– Sedimentation– Decomposition of organic matter

What is soil?What is soil?• Mixture of :

– Minerals – weathered rock, essential nutrients– Water – trapped in pore spaces, responsible for leaching

or illuviation– Gases – located in pore spaces– Humus – dead “stuff”, decaying organic materials

thanks to fungi and decomposers, Leaf Litter

Humus NOT HUMMUS Humus NOT HUMMUS

Soil CompositionSoil Composition

Soils: FormationSoils: Formation• Soils form as parent rock material is weathered

(broken down) into smaller pieces via chemical or mechanical weathering– Chemical : lichens excreting acids that break apart rock– Physical: physical forces, freeze/thaw cycles, critters,

biological activity

Soils: Formation p. 212, 215Soils: Formation p. 212, 215

Soil horizons Soil horizons Distinctive layers Distinctive layers

O horizonLeaf litter, organic

A horizonTopsoil

C horizonWeathered Parent

MaterialMature soil

Young soil

RegolithRegolith

BedrockBedrock

Immature soilImmature soil

Humus

B horizonSubsoil, clay/cations leached from above

accumulate here

Weak humus-mineral mixture

Mosaicof closelypackedpebbles,boulders

Dry, brown toreddish-brown, with variable accumulationsof clay, calciumcarbonate, andsoluble salts

Desert Soil(hot, dry climate)

Grassland Soil(semiarid climate)

Alkaline,dark,and richin humus

Clay,calciumcompounds

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)

Soil Organisms

Provide ecosystem services:-Maintain soil fertility-Cycle organic matter (nutrients)-Break down toxins (bioremediation)-Clean water as it percolates down

Soil PropertiesSoil Properties

Infiltration

Infiltration Leaching

Leaching

Porosity Porosity

Water Water

High permeability Low permeability

Permeability

Porosity vs. PermeabilityPorosity vs. Permeability

Porosity : amount of pore space, # of pores

Porosity : amount of pore space, # of pores

Permeability : ability to transmit fluids

Permeability : ability to transmit fluids

Water Water

High permeability Low permeability

CLAYS:High porosityImpermeable

SANDS:Low porosityPermeable

Soil PropertiesSoil Properties

1. Texture : the way the soil feels

Depends on amount of each

sized particles termed soil fraction

Sand-largest-feel gritty Silt-medium-feel soft, silky,

floury Clay-small-feel sticky, hard to

squeeze, greatest surface area

1. Texture : the way the soil feels

Depends on amount of each

sized particles termed soil fraction

Sand-largest-feel gritty Silt-medium-feel soft, silky,

floury Clay-small-feel sticky, hard to

squeeze, greatest surface area

Soil PropertiesSoil Properties

1. Texture 1. Texture

Structure: % clay, % sand, % silt Structure: % clay, % sand, % silt

100%clay

Increasingpercentage silt

Increasingpercentage clay

0

20

40

60

80

80

60

40

20

0

100%sand80 60 40 20

100%silt

Increasing percentage sand

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

Gravel 2-64 mm

Sand 0.05-2 mm

Silt 0.002-0.05 mm

Clay less than 0.002 mm

Soil Texture Triangle

Properties of Soils with Different TexturesProperties of Soils with Different Textures

TextureNutrient InfiltrationWater-HoldingAeration 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

Refer to Fig. 10-15 p. 215Refer to Fig. 10-15 p. 215

Why care about soil texture?predicts fertility and use

Why care about soil texture?predicts fertility and use

Chemical Properties of SoilChemical Properties of Soil

• pH• Fertility

– 20 minerals needed for plant growth– Major Nutrients (N-P-K)

• Nitrogen• Phosphorus• Potassium

– Minor Nutrients• Soil Tests

Soil ErosionSoil Erosion

The movement of soil components from one The movement of soil components from one place to another by wind and water.place to another by wind and water.

• Sheet erosionSheet erosion – water moves down a slope or – water moves down a slope or across a field in a wide flowacross a field in a wide flow

• Rill erosionRill erosion – surface water forms fast-flowing – surface water forms fast-flowing rivulets that cut channels in the soilrivulets that cut channels in the soil

• Gully erosionGully erosion – rivulets join together and cut – rivulets join together and cut channels wider and deeper until they become channels wider and deeper until they become ditches and gullies.ditches and gullies.

Areas of serious concern

Areas of some concern

Stable or nonvegetative areas

Global Soil ErosionGlobal Soil Erosion• loss of soil organic matterloss of soil organic matter

• reduced ability to store reduced ability to store waterwater

• increased use of fertilizerincreased use of fertilizer

• floodingflooding

• sedimentationsedimentation

DesertificationDesertification

CausesCauses• OvergrazingOvergrazing• DeforestationDeforestation• Surface miningSurface mining• ErosionErosion• SalinizationSalinization• Soil compactionSoil compaction

ConsequencesConsequences• Worsening droughtWorsening drought• FamineFamine• Economic lossesEconomic losses• Lower living Lower living

standardsstandards• Environmental Environmental

refugeesrefugees

Conversion of rangeland, rain-fed cropland, or irrigated cropland to desert-like land, with a drop in agricultural productivity of 10% or more.

Soil DegradationSoil Degradation

Salinization -the accumulation of salt

Salinization -the accumulation of salt

Waterlogging –saturation of soil with irrigation water or excess precipitation so the water table rises close to the surface.

Waterlogging –saturation of soil with irrigation water or excess precipitation so the water table rises close to the surface.

EvaporationTranspiration

Evaporation

Waterlogging

Less permeableclay layer

Solutions: Soil ConservationSolutions: Soil ConservationConventional-tillageConventional-tillage

Conservation tillage Conservation tillage

Cropping methods Cropping methods

WindbreaksWindbreaks

Conventional tillageConventional tillage

• Crop cultivation Crop cultivation method in which method in which a planting surface a planting surface is made by is made by plowingplowing land, land, breaking upbreaking up the the exposed soil, and exposed soil, and then then smoothingsmoothing the surface.the surface.

Conservation tillageConservation tillage

• Crop cultivation in Crop cultivation in which soil is which soil is disturbed littledisturbed little ((mini-mum tillage mini-mum tillage farmingfarming) or ) or not at not at allall ( (no-till farmingno-till farming) ) to reduce soil to reduce soil erosion, lower erosion, lower labor costs, and labor costs, and save energy.save energy.

TerracingTerracing

Contour planting and strip croppingContour planting and strip cropping

Alley croppingAlley cropping

WindbreaksWindbreaks

Soil RestorationSoil Restoration

Crop RotationCrop Rotation– planting a field with different planting a field with different

crops from year to year to reduce crops from year to year to reduce soil nutrient depletion.soil nutrient depletion.

Soil RestorationSoil Restoration

Organic FertilizersOrganic Fertilizers• Animal manure

– Improves soil structure– Adds organic nitrogen– Stimulates beneficial soil bacteria and fungi

• Green manure– Fresh and growing green vegetation

• Compost– Microorganisms break down organic matter

in the presence of oxygen

Soil RestorationSoil RestorationCommercial Inorganic FertilizersCommercial Inorganic Fertilizers

Nitrogen, Phosphorus and PotassiumNitrogen, Phosphorus and Potassium– N, P, KN, P, K

• AdvantagesAdvantages– Easily transported, stored, and appliedEasily transported, stored, and applied

• DisadvantagesDisadvantages– Not adding humusNot adding humus– Reducing organic matter contentReducing organic matter content– Lowering oxygen contentLowering oxygen content– Supply only 2 or 3 of the more than 20 Supply only 2 or 3 of the more than 20

nutrients needednutrients needed– Require large amountsRequire large amounts– Release nitrous oxidesRelease nitrous oxides