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Plate Tectonics Plate Tectonics

Plate Tectonics - PowerPoint Presentation

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Plate Tectonics - PPT Presentation

Evolution of the Earth Cracks in the Earths Crust The crust when it is solid acts as a heat insulator for the hot interior of the Earth The molten material in the mantle magma below the crust builds up tremendous heat and pressure ID: 367346

ocean plates plate crust plates ocean crust plate oceanic earthquakes tectonic moves move pangea floor magma mantle america ridges

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Slide1

Plate Tectonics

Evolution of the EarthSlide2

Cracks in the Earth’s Crust

The

crust

, when it is solid, acts as a

heat insulator

for the hot interior of the Earth.

The molten material in the mantle,

magma

, below the crust builds up tremendous heat and pressure.

The magma creates

convection currents

and rises to the surface.

These currents can crack the crust (both oceanic and continental)!Slide3

Tectonic Plates

These cracks separate the crust into

plates

(

huge sections of the Earth that moves relative to each other

).Lithosphere is responsible for tectonic plates because it adheres the crust to the mantle.Slide4

Plate Boundaries

Convergent Boundaries

Subduction

– when one oceanic plate plunges beneath another

Crust enters mantle, pressure cracks crust

Volcanoes

Ocean trenches

Continental Collision

- continental plates move toward one anotherThe crust moves upward, folds and buckles and breaks mountainsDivergent Boundaries – plates move away from each otherSeafloor spreadingMid-ocean ridgesTransform fault – plate moves sideways from each other, slide past each otherearthquakesSlide5

SubductionSlide6
Slide7

Convergent PlatesSlide8

Convergent PlatesSlide9

Seafloor Spreading

Magma rises to the oceanic crustal surface

forms mid ocean ridges.

As the lava cools, it forms new seafloor and features: rift valleys; seamounts; abyssal hills (volcanic peaks)

As new material reaches the surface, the plates are

pushed apartSlide10
Slide11

Seafloor Spreading cont.

Earth’s longest mountain chain

47,000 miles long running down the middle of the Atlantic Ocean (surfacing at Iceland), around Africa, through the Indian Ocean, between Australia and Antarctica, and north through the Pacific Ocean.

Running along the top of this chain of mountains is a deep crack, called a rift valley. It is here that new ocean floor is continuously created.

As the two sides of the mountain move away from each other, magma wells up from the Earth's interior. It then solidifies into rock as it is cooled by the sea, creating new ocean floor.

The mapping of the seafloor also revealed that these huge underwater mountain ranges have a deep trench which bisects the length of the ridges and in places is more than 2000 meters deep.

Seismic studies show that the mid-oceanic ridges experience an elevated number of earthquakes. All these observations indicate intense geological activity at the mid-oceanic ridges.

The speed at which new ocean floor is created varies from one location on the ocean ridge to another.

Between North America and Europe, the rate is about 2.2 inches/yearAt the East Pacific rise, which is pushing a plate into the west coast of South America, the rate is 12.6 inches/yearSlide12

Transform PlatesSlide13

Transform Plates

San Andreas

FaultSlide14
Slide15

Why do the Plates Move?

No single idea explains everything but we can identify several forces that contribute to the movement of the plates.

Slab pull

The sinking of the cooled dense oceanic plates pulls on the rest of the plate

Ridge rises

The material deposited on the top of the ridge slides downs from the rise pushing on the plate

Convection

Movement within the mantle could be part of the driving force behind the motion of the plates.Slide16

Tectonic Plates

Earth’s crust is broken into about 19 piecesSlide17

Earthquakes

Tidal waves or Tsunamis result when a large section of the sea floor

suddenly moves

and therefore displaces a massive amount of water.Slide18

Earthquakes

Location of worldwide earthquakesSlide19

Tectonic Plates

EarthquakesSlide20

Tectonic Plates

VolcanoesSlide21

Pangea

What is Pangaea?

Pangaea was a super continent at one time.

200 mill years ago, plates shifted enough to cause movement.

Scientists use the similarity of rock types and fossil types that date to the same age to support their theory that the continents were connected to form a super continent.Slide22

PangeaSlide23

Pangea

The break up

of PangeaSlide24

Where are we going?

We appear to be headed for another super

continent as North America, South America,

Asia and Australia converge in the

ever shrinking Pacific OceanSlide25