Plate TectonicsPlate Tectonics

Ch 17Ch 17

Mountain View Hypothesis for Ring of Fire

16%

12%

10%

8%6%6%

5%

5%

4%

4%

3%

3%

2%2%

1%1%1%1%1%1%1%1%1%1%0%0%0%0%0%0%0%0%

weather

plate tectonics

ocean depth

shape of the world

Conspiratory Animals (bunnies,sharks, whales, penguins, elephants)Activity of People

population

God

sumo wrestlers

obesity

Destroying the planet

mountains

moon, sun & solar system

Earth Flattulence

ocean temperature

Godzilla and other monsters

movies / rock stars

ice bergs

car accidents

rock slides

teenage romance

gold rush / mining

color of grass

magnetic forces

land is sinking

shuttle launch

animal massuese

color of water

trees

oceans are getting bigger

air plane crash

rivers

FactsFacts

South America moving away from South America moving away from Africa at 2-3 cm/yearAfrica at 2-3 cm/year

Hawaii is moving NW 8-9 cm/yrHawaii is moving NW 8-9 cm/yr Mount Everest growing 5 cm/yearMount Everest growing 5 cm/year

Early TheoriesEarly Theories

Late 1500 Abraham Ortelius (map Late 1500 Abraham Ortelius (map maker) noticed the fit of the maker) noticed the fit of the continents in the Atlantic Ocean.continents in the Atlantic Ocean.– Proposed N & S America broke off of Proposed N & S America broke off of

Europe and Africa by earthquakes and Europe and Africa by earthquakes and floodsfloods

Late 1800s Eduard Suess (geologist) Late 1800s Eduard Suess (geologist) proposed that the southern proposed that the southern continents were joined- continents were joined- “Gondwanaland”“Gondwanaland”

Alfred WegenerAlfred Wegener

German Scientist proposed in 1912 German Scientist proposed in 1912 “Theory of Continental Drift”“Theory of Continental Drift”

Scientific community believed ocean Scientific community believed ocean basins and continents were a permanent basins and continents were a permanent feature of Earth. feature of Earth.

Two flaws with Wegener’s theory caused Two flaws with Wegener’s theory caused them reject his hypothesis.them reject his hypothesis.– Cause of movement?Cause of movement?– How continents were moving through a How continents were moving through a

stationary ocean floor?stationary ocean floor?

Continental DriftContinental Drift

Proposed all continents were joined Proposed all continents were joined together in a single land masstogether in a single land mass– Pangaea (all – earth)Pangaea (all – earth)

Pangaea broke apart 200 million Pangaea broke apart 200 million years ago (Mesozoic)years ago (Mesozoic)

Began theory with puzzle like fit of Began theory with puzzle like fit of continentscontinents

EvidenceEvidence

Rock formationsRock formations– When Pangaea breaks apart large When Pangaea breaks apart large

structures (mtn ranges) would be structures (mtn ranges) would be separatedseparated

– Using this Wegener hypothesized there Using this Wegener hypothesized there would be similar rocks on either side of would be similar rocks on either side of the Atlantic Oceanthe Atlantic OceanMatching rocks in Appalachian Mountains, Matching rocks in Appalachian Mountains,

Greenland and Europe (more than 200 Greenland and Europe (more than 200 million years old)million years old)

EvidenceEvidence

FossilsFossils– Similar fossils of plants and animals that Similar fossils of plants and animals that

lived on land would have been found on lived on land would have been found on separated continentsseparated continents

– Wegener hypothesized that land animals Wegener hypothesized that land animals could not have swum great distances could not have swum great distances across the oceanacross the ocean

– The ages of the fossils confirmed the The ages of the fossils confirmed the break-up time periodbreak-up time period

EvidenceEvidence

ClimateClimate– By studying sedimentary rocks he found By studying sedimentary rocks he found

evidence of climactic changesevidence of climactic changesCoal beds in Antarctica meant that it was Coal beds in Antarctica meant that it was

once warm and rainyonce warm and rainyGlacial evidence in India, Australia, Africa Glacial evidence in India, Australia, Africa

and South America indicate thick ice capsand South America indicate thick ice caps

Seafloor SpreadingSeafloor Spreading

Confirmed Wegener’s theories in the Confirmed Wegener’s theories in the 1960’s1960’s

TechnologyTechnology– SONAR - sound waves used to map SONAR - sound waves used to map

ocean floorocean floor– Magnetometer – detects small changes Magnetometer – detects small changes

in magnetic fields of rocksin magnetic fields of rocks

OceanOcean

Vast underwater Vast underwater mountain ranges mountain ranges called mid-ocean called mid-ocean ridgesridges

Deep-sea trenches Deep-sea trenches are narrow long are narrow long depressions with depressions with very steep sides very steep sides (miles deep)(miles deep)

Ages of RocksAges of Rocks

Ages of RocksAges of Rocks

Ocean crust is much younger than Ocean crust is much younger than continental crustcontinental crust

Near ocean ridges crust is newNear ocean ridges crust is new In deep sea trenches crust is oldIn deep sea trenches crust is old Figure 17-7 page 450 (your textbook)Figure 17-7 page 450 (your textbook) Ocean sediments are much thinner Ocean sediments are much thinner

than on continents and increase with than on continents and increase with distance from ridgesdistance from ridges

MagnetismMagnetism

Paleomagnetism – Study of Earth’s Paleomagnetism – Study of Earth’s magnetic recordmagnetic record

Basalt – Iron rich rock forms ocean crustBasalt – Iron rich rock forms ocean crust– The iron in the rocks is always aligned with the The iron in the rocks is always aligned with the

magnetic poles of the earth (north & south just magnetic poles of the earth (north & south just like a magnet)like a magnet)

– When lava hardens into basalt, iron ions are When lava hardens into basalt, iron ions are permanently aligned, recording the magnetic permanently aligned, recording the magnetic history of the earthhistory of the earth

Magnetic ReversalsMagnetic Reversals

MagnetismMagnetism

Earth’s StructureEarth’s Structure

Crust- Rocky outer Crust- Rocky outer layer (5-35 Km) layer (5-35 Km)

Mantle- 82% of Mantle- 82% of Earth’s Volume, Earth’s Volume, made of silica and made of silica and molten rockmolten rock

Core- iron and Core- iron and nickelnickel

Earth’s Layers (Function)Earth’s Layers (Function)

Lithosphere (Ball of Rock) Crust and Lithosphere (Ball of Rock) Crust and Upper MantleUpper Mantle

Moho DiscontinuityMoho Discontinuity Asthenosphere (weak ball) Mantle, Asthenosphere (weak ball) Mantle,

rocks near melting point, allows rocks near melting point, allows lithosphere to movelithosphere to move

Mesosphere (middle ball) Very hot Mesosphere (middle ball) Very hot rock, capable of flow, more rigid rock, capable of flow, more rigid because of pressurebecause of pressure

Earth’s Layers (Function)Earth’s Layers (Function)

Outer Core- Liquid Layer, generates Outer Core- Liquid Layer, generates magnetic fieldmagnetic field

Inner Core- Solid because of high Inner Core- Solid because of high pressurepressure

Plate BoundariesPlate Boundaries

Divergent- (2 Divergent- (2 movements) places movements) places where 2 plates where 2 plates move awaymove away– Oceanic/Oceanic- Oceanic/Oceanic-

Mid-Ocean RidgeMid-Ocean Ridge– Continental/Continental/

Continental- Rift Continental- Rift ValleyValley

Plate BoundariesPlate Boundaries

Convergent (1 Movement)- Places Convergent (1 Movement)- Places where plates come togetherwhere plates come together

Classified by types of platesClassified by types of plates

Oceanic-OceanicOceanic-Oceanic

Subduction- Oceanic plate goes under Subduction- Oceanic plate goes under another plate, Recycles the rock, May form another plate, Recycles the rock, May form Island ArcIsland Arc

Oceanic-ContinentalOceanic-Continental

Oceanic plate goes under Continental Oceanic plate goes under Continental plate.plate.

Causes Costal Mountain Range and Arc of Causes Costal Mountain Range and Arc of VolcanoesVolcanoes

Continental-ContinentalContinental-Continental

Causes TALL Mountains to formCauses TALL Mountains to form

TransformTransform

Transform (across)- Transform (across)- deforms crust, long deforms crust, long faults.faults.

Usually Usually underwater, except underwater, except San AndresSan Andres

Causes of MovementCauses of Movement

Mantle Convection- Movement of warm Mantle Convection- Movement of warm and cool rock in mantle, similar to and cool rock in mantle, similar to conveyor beltconveyor belt

Causes of MovementCauses of Movement

Ridge Push- Weight of uplifting ridge Ridge Push- Weight of uplifting ridge pushes plate toward trenchespushes plate toward trenches

Slab Pull- Weight of Subducting plate pulls Slab Pull- Weight of Subducting plate pulls the plate into the mantlethe plate into the mantle