ch12

Chapter 12Chapter 12

Earth’s Internal Earth’s Internal Structure, Rock Structure, Rock

Cycle, and Geologic Cycle, and Geologic TimeTime

Earth’s Internal StructureEarth’s Internal Structure

The CoresThe Cores

InnerInner– Solid Solid → pressure > heat→ pressure > heat

OuterOuter– Liquid Liquid → heat > pressure→ heat > pressure

– Creates Creates ____magnetosphere________magnetosphere____

How?How?

AsthenosphereAsthenosphere– ““without _strength_”without _strength_”– Is part of the upper mantleIs part of the upper mantle– Molten rockMolten rock

LithosphereLithosphere– ““_stone_”_stone_”– Includes the upper part of the Includes the upper part of the

asthenosphereasthenosphere– Slides over the upper mantleSlides over the upper mantle– Location for earthquakes, volcanoes, Location for earthquakes, volcanoes,

& continental drifts occur& continental drifts occur

The CrustsThe Crusts

Oceanic CrustOceanic Crust– Mostly ___basalt___Mostly ___basalt___– Thinner and denser than continental Thinner and denser than continental

Continental CrustContinental Crust– Mostly graniteMostly granite– Thickest beneath mountain rangesThickest beneath mountain ranges– Thinnest in ___Rift Valley Africa____Thinnest in ___Rift Valley Africa____

Rocks and Minerals of the Rocks and Minerals of the CrustCrust

MineralsMinerals– Naturally occurring with distinct configurations Naturally occurring with distinct configurations

in crystalline formin crystalline form RocksRocks

– 2+ minerals bonded in solid state2+ minerals bonded in solid state– 3 Major types3 Major types

Igneous Igneous SedimentarySedimentary MetamorphicMetamorphic

IgneousIgneous

Form from solidification of molten Form from solidification of molten magmamagma– ExtrusiveExtrusive

Cools _____on surface________Cools _____on surface________

– IntrusiveIntrusive Cools _____within the crust_____Cools _____within the crust_____

Obsidian Gabbro

Basalt Granite Pumice

Intrusive PyroclasticExtrusive

Intrusive Igneous Rock Intrusive Igneous Rock ExamplesExamples

Horizontal spread

Vertical spread

Huge; unknown depth

Horizontal spread that warps rocks above it

Types of _________

BatholithBatholith

Sill Sill

DikesDikes

Silicate Minerals and Silicate Minerals and Igneous RocksIgneous Rocks

Mafic Igneous MineralsMafic Igneous Minerals

Mafic: “m” for Mafic: “m” for magnesium, “f” for magnesium, “f” for Fe (iron)Fe (iron)

Silicates containing Silicates containing magnesium and magnesium and ironiron

Mafic minerals are Mafic minerals are denser and heavier denser and heavier than felsic minerals than felsic minerals

Color?Color?

Felsic Igneous Felsic Igneous MineralsMinerals

Felsic: “fel” for Felsic: “fel” for feldspar “si” for feldspar “si” for silicatesilicate

FeldsparsFeldspars– silicate-aluminum silicate-aluminum

minerals, as well minerals, as well as K, Na, Ca, as K, Na, Ca,

Felsic minerals Felsic minerals are lighter in color are lighter in color and less dense and less dense than mafic than mafic mineralsminerals

Igneous Rock

Felsic Mafic

Granite

Extrusive

Intrusive

Rhyolite

Gabbro

Basalt

Sedimentary RocksSedimentary Rocks

Form from burial, compression and Form from burial, compression and chemical modificationchemical modification– e.g. ________ and ___________ of materialse.g. ________ and ___________ of materials

Classes of SedimentsClasses of Sediments

Clastic (composed of fragments = Clastic (composed of fragments = clastsclasts))

Chemically precipitated sedimentChemically precipitated sediment Organic sedimentOrganic sediment

Clastic Sedimentary RocksClastic Sedimentary Rocks

Consist of inorganic rock and mineral Consist of inorganic rock and mineral fragmentsfragments– quartz most important componentquartz most important component

““_______” - separation of particles by size_______” - separation of particles by size– determines texture of rockdetermines texture of rock

Compaction and cementationCompaction and cementation– CementationCementation occurs when dissolved occurs when dissolved

minerals recrystallizeminerals recrystallize _______ and __________ are common cements_______ and __________ are common cements

Clastic sedimentation - hyperlink

Common Clastic Common Clastic Sedimentary RocksSedimentary Rocks

Classified by size of particlesClassified by size of particles Sandstone Sandstone

– fine to coarse cemented sandfine to coarse cemented sand Conglomerate – Conglomerate –

– sandstone with mutlisized pebblessandstone with mutlisized pebbles Siltstone, claystone, mudstoneSiltstone, claystone, mudstone

– ________ – any of the above that ________ – any of the above that break easily into small flakesbreak easily into small flakes

– usually __________ and ______ easilyusually __________ and ______ easily

Sandstone

Shale

Conglomerate

Chemically Precipitated Chemically Precipitated Sedimentary RocksSedimentary Rocks

Precipitation and recrystallization Precipitation and recrystallization – Carbonate rocks:Carbonate rocks:

limestonelimestone: calcium carbonate (calcite): calcium carbonate (calcite) dolomitedolomite: calcium-magnesium carbonate: calcium-magnesium carbonate

– ChertChert: silica in hard noncystalline form: silica in hard noncystalline form Evaporites: _________________________Evaporites: _________________________

--halitehalite - rock salt - rock salt

Limestone

Dolomite

Halite

Organic SedimentsOrganic Sediments

Large accumulations of plant Large accumulations of plant remainsremains

Hydrocarbon deposits (“fossil Hydrocarbon deposits (“fossil fuels”):fuels”):– solids: peat (histosols) and coalsolids: peat (histosols) and coal– liquids and gases (mineral fuels): liquids and gases (mineral fuels):

petroleumpetroleum natural gasnatural gas

Peat

Coal

Metamorphic RocksMetamorphic Rocks

““to ______________”to ______________” Existing rock is modifiedExisting rock is modified Form from:Form from:

– ________ and ___________________ and ___________– Contact with invading magma – Contact with invading magma –

batholiths, dikes, sillsbatholiths, dikes, sills Mineral components are rearrangedMineral components are rearranged Look for bandingLook for banding

Slate

Gneiss

Rock CycleRock Cycle

Geologic TimeGeologic Time

““deep time”deep time” Def: the period of time that Def: the period of time that

encompasses all of Earth history, encompasses all of Earth history, from its formation to presentfrom its formation to present

Universe: 14 Universe: 14 BYBY

Earth: 4.6 BYEarth: 4.6 BY Large to smallLarge to small

– EonsEons– ErasEras– PeriodsPeriods– EpochsEpochs

Telling Geologic Time:Telling Geologic Time:Radiometric DatingRadiometric Dating

Measure amount of radioactive Measure amount of radioactive decay of rocksdecay of rocks

Radioactive isotopesRadioactive isotopes– Unstable isotopes change from one Unstable isotopes change from one

element to anotherelement to another– Radiation is emitted in the processRadiation is emitted in the process– __________________________– the amt of time required – the amt of time required

for ½ of the isotopes in any sample to for ½ of the isotopes in any sample to decaydecay

The The Grand Grand

Canyon Canyon and and

Geologic Geologic TimeTime

The Geologic Time Scale Related to the Calendar

YearEvent Age Time in Year

Earth formed 4.6 by Jan. 1

First single-celled organism

3.2 by mid-April

Oxygen in atmosphere 2.0 by mid-July

First cell with nucleus 1.0 by Oct. 12

First vertebrates 625 my

Nov. 10

First land plants 340 my

Dec. 3

First reptiles 220 my

Dec. 13

First mammals 155 my

Dec. 18

Grand Canyon downcutting

10 my Dec. 31, 5 A.M.

Early hominids 3 my Dec. 31, 6 P.M.

Your birth 18 Dec. 31 (0.05 seconds before midnight)