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Transcript of 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)