Plate TectonicsPlate Tectonics

Layers of the EarthLayers of the Earth

• CrustCrust– 1– 1stst layer is solid rock. The thinnest layer is solid rock. The thinnest layer.layer.

• LithosphereLithosphere – The layer that is the crust and – The layer that is the crust and the top of the mantle. the top of the mantle. Lithos Lithos means means ““rockrock””..

• AsthenosphereAsthenosphere – The layer just below the – The layer just below the lithosphere & is part of the upper mantle. lithosphere & is part of the upper mantle. Acts like a plastic, with low density. The Acts like a plastic, with low density. The layer that moves the crustal plates.layer that moves the crustal plates.

• MantleMantle – Layer of hot solid rock. The – Layer of hot solid rock. The thickest layer.thickest layer.

• Outer CoreOuter Core – Layer made of liquid iron and – Layer made of liquid iron and nickel. Is responsible for Earthnickel. Is responsible for Earth’’s s electromagnetic fieldelectromagnetic field..

• Inner CoreInner Core – Layer of solid iron and nickel. – Layer of solid iron and nickel.

Composition of the Composition of the LayersLayers

• The Earth becomes denser the The Earth becomes denser the farther you go inside.farther you go inside.

• The crust is made primarily of The crust is made primarily of siliconsilicon and and oxygenoxygen (silicates) as (silicates) as well as calcium (Ca) & sodium well as calcium (Ca) & sodium (Na).(Na).

• The mantle is primarily iron (Fe), The mantle is primarily iron (Fe), magnesium (Mg), aluminum (Al), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O).silicon (Si), and oxygen (O).

Electromagnetic FieldElectromagnetic Field• The Electromagnetic (EM) field is caused The Electromagnetic (EM) field is caused

due to the spinning iron and nickel in due to the spinning iron and nickel in the outer core.the outer core.

• The EM field protects Earth from harmful The EM field protects Earth from harmful electromagnetic waves in space. electromagnetic waves in space.

• The field also gives Earth its magnetism The field also gives Earth its magnetism (North & South Pole).(North & South Pole).

• The EM field changes each day. It The EM field changes each day. It constantly has to be measured all over constantly has to be measured all over Earth.Earth.

Form from electrons and protons. Form from electrons and protons. Held together by the magnetic Held together by the magnetic

field.field.

Crust FeaturesCrust Features• There are 2 types of crust – There are 2 types of crust – OceanOcean

& & ContinentalContinental. . • Ocean crustOcean crust is is mostmost dense and is dense and is

made mostly of basalt. Rocks tend made mostly of basalt. Rocks tend to be younger (no more than 200 to be younger (no more than 200 million yrs.)million yrs.)

• Continental crustContinental crust is is lessless dense dense and is made mostly of granite. and is made mostly of granite. Rocks tend to be the oldest on Rocks tend to be the oldest on Earth.Earth.

Plate TectonicsPlate Tectonics

• THEORYTHEORY - - The crust is brittle The crust is brittle and can break. The crust itself and can break. The crust itself is broken into plates.is broken into plates.

• These plates move due to These plates move due to convection currentsconvection currents in the in the asthenosphereasthenosphere..

A boiling pot illustrates A boiling pot illustrates the convection current in the convection current in a liquid. a liquid. Scientists hypothesize Scientists hypothesize that a similar action is that a similar action is happening in the happening in the asthenosphere.asthenosphere.

The The convecticonvection on current current moves moves the the plates plates slowly slowly over over time. time.

Overview of the actions at plate Overview of the actions at plate boundariesboundaries

The Theories…..The Theories…..

Various models of how the asthenosphere may be behaving.

Effects of Plate Effects of Plate TectonicsTectonics

• EarthquakesEarthquakes• VolcanoesVolcanoes• MountainsMountains• Continental Drift (Pangaea)Continental Drift (Pangaea)

Hot SpotsHot Spots• Hawaiian Islands are Hawaiian Islands are

the perfect examplethe perfect example• The Pacific plate is The Pacific plate is

slowly moving to the slowly moving to the NorthwestNorthwest

• Kauai formed first, and Kauai formed first, and as the plate has moved as the plate has moved over the hot spot, over the hot spot, Oahu, Molokai, Maui, Oahu, Molokai, Maui, and finally the big and finally the big island of Hawaii have island of Hawaii have successively formedsuccessively formed

• Yellowstone is also an Yellowstone is also an example of a hot spotexample of a hot spot

Hot Spots are huge plumes of magma that come from the deep mantle

Proving Plate TectonicsProving Plate Tectonics

• PaleomagnetismPaleomagnetism• Ocean DrillingOcean Drilling• Plate Boundary Evidence – Plate Boundary Evidence –

including mapping the ocean including mapping the ocean floorfloor

• Earthquake & Volcanic ActivityEarthquake & Volcanic Activity• SEISMIC WAVES!!SEISMIC WAVES!!

Using Seismic WavesUsing Seismic Waves

• These are These are devices devices which which detect detect seismic seismic waves.waves.

• The plate is The plate is placed in placed in front to front to create the create the waves. waves.

• The waves The waves give a give a profile of profile of the land.the land.

A A sledgehamsledgehammer can be mer can be used to used to generate generate the seismic the seismic waveswaves

PaleomagnetismPaleomagnetism• Rocks that align Rocks that align

with the current with the current magnetic field magnetic field have what we have what we call call normal normal polaritypolarity

• Rocks that align Rocks that align to the south to the south pole have what pole have what we call we call reverse reverse polaritypolarity

• The ocean floor The ocean floor is said to have a is said to have a ““zebra stripezebra stripe”” magnetic signalmagnetic signal

The zebra stripes are not visible to the naked eye, but only to a magnetometer as it is towed behind a ship

Ship

PaleomagnetPaleomagnetismism

• Yes, the magnetic signature of the rocks flip-flops, but the distances between each reversal are the same on either side of the mid-ocean ridge

• This allows geologists to conclude that sea-floor spreading is equal on either side of a mid ocean ridge

Compare these distances here and you find that they are identical

A BE E

BCC

Ocean DrillingOcean Drilling• The Deep Sea Drilling Project (DSDP) spent from The Deep Sea Drilling Project (DSDP) spent from

1968-1983 drilling 1092 sediment and basalt 1968-1983 drilling 1092 sediment and basalt cores in every ocean on earthcores in every ocean on earth

• It was found that fossils in the sediments closest It was found that fossils in the sediments closest to the ridges were younger than fossils found to the ridges were younger than fossils found further awayfurther away

This cross section of the Atlantic Ocean shows the topography that the DSDP found

Sediments near the ridge were found to be younger than the sediments near the continental margins

Ocean DrillingOcean Drilling• The ocean vessel The ocean vessel ““GLOMAR CHALLENGERGLOMAR CHALLENGER”” was the ship that was the ship that

gathered all the data for the Deep Sea Drilling Projectgathered all the data for the Deep Sea Drilling Project• DSDP has changed into the Ocean Drilling Program (ODP) DSDP has changed into the Ocean Drilling Program (ODP)

and continues to help us understand the oceans even to and continues to help us understand the oceans even to this daythis day

The The Glomar ChallengerGlomar Challenger was was named after the original oceanic named after the original oceanic science vessel, science vessel, ChallengerChallenger, of , of the 1800the 1800

Earthquake PatternsEarthquake Patterns• Well over 95% of all earthquakes occur along the current Well over 95% of all earthquakes occur along the current

plate boundariesplate boundaries• The map shows where earthquakes occur on an annual basisThe map shows where earthquakes occur on an annual basis• Do the patterns match up with anything youDo the patterns match up with anything you’’ve seen before?ve seen before?

The red dots represent earthquake The red dots represent earthquake activity. What is the relationship activity. What is the relationship with their location and plate with their location and plate boundaries?boundaries?

Types of BoundariesTypes of Boundaries

• ConvergentConvergent – boundaries moving – boundaries moving towardstowards each other. each other.

• DivergentDivergent – boundaries moving – boundaries moving awayaway from each other. from each other.

• TransformTransform – boundaries moving – boundaries moving side-by-side.side-by-side.

Divergent BoundariesDivergent Boundaries

Rio Grande Rift Valley

East Pacific Rise Mid Atlantic

Ridge

East African Rift Valley

Red Sea

Mid Indian Ridge

Evidence Evidence of of DivergenDivergence in ce in North North AmericaAmerica

Rio Grande Gorge – evidence Rio Grande Gorge – evidence of the North American plate of the North American plate pulling apart.pulling apart.

Convergent BoundariesConvergent Boundaries

Andes Mountains

Japanese Island Arc

Appalachian Mountains

Himalayan Mountains

Cascade Mountains

Ural Mountains

Philippine Island Arc

Aleutian Island Arc

Himalayan Mountains – Himalayan Mountains – picture from spacepicture from space

French AlpsFrench Alps

Transform BoundariesTransform Boundaries

San Andreas Fault

Continental DriftContinental Drift

• The theory that EarthThe theory that Earth’’s continents s continents move together and apart due to move together and apart due to the the moving crustal platesmoving crustal plates. . Developed by Alfred Wegener.Developed by Alfred Wegener.

• The supercontinent when all 7 are The supercontinent when all 7 are together is called together is called PangaeaPangaea..

• It take approximately It take approximately 225 million 225 million yearsyears for the continents to come for the continents to come together.together.

The EvidenceThe Evidence• Continental Jigsaw PuzzleContinental Jigsaw Puzzle – shorelines & – shorelines &

continental shelves fit together. continental shelves fit together. • FossilsFossils – fossils of animals and plants – fossils of animals and plants

matched on different continents that had matched on different continents that had no way of being transported across an no way of being transported across an ocean.ocean.

ExamplesExamples – – Glossopteris (fern) Glossopteris (fern) found in Africa, Asia, Australia, India, found in Africa, Asia, Australia, India, Antarctica, & South America; Antarctica, & South America; MesosaurusMesosaurus found in South America & Africa; found in South America & Africa; Marsupials in Australia & North AmericaMarsupials in Australia & North America

• Rock TypesRock Types – Mountain ranges that end – Mountain ranges that end at a coastline, then pick up on a at a coastline, then pick up on a different piece of land.different piece of land.

ExampleExample – Appalachians, Mt. range that – Appalachians, Mt. range that starts in the British Isles and then picks starts in the British Isles and then picks up in Scandinavia, Mts. in South up in Scandinavia, Mts. in South America that begin again in Africa.America that begin again in Africa.

• Ancient ClimatesAncient Climates – Glacial deposits – Glacial deposits were found in South America & Africa were found in South America & Africa that were identical; Evidence of lush that were identical; Evidence of lush forests in the Northern Hemisphere forests in the Northern Hemisphere such as in E. United States, Siberia, & such as in E. United States, Siberia, & Europe where it is now cold; South Europe where it is now cold; South Africa was situated over the South Africa was situated over the South Pole.Pole.

Plates Throughout Plates Throughout HistoryHistory

Plates Throughout Plates Throughout HistoryHistory

Plates Throughout Plates Throughout HistoryHistory

Plates Throughout History

Plates Throughout Plates Throughout HistoryHistory

Plates Throughout Plates Throughout HistoryHistory

Plates Throughout Plates Throughout HistoryHistory

Plates into the FuturePlates into the Future

Ok, Prove it…Ok, Prove it…• REMEMBERREMEMBER: The : The

four main reasons four main reasons that scientists give that scientists give to support the to support the theory of plate theory of plate tectonicstectonics– Earthquake DataEarthquake Data– Ocean Drilling Ocean Drilling

DataData– Hot SpotsHot Spots– PaleomagnetismPaleomagnetism