CONTINENTAL DRIFT Alfred Wegener proposed the theory · PDF fileThe Theory of Plate Tectonics ... evidence that support this theory ... crustal plate is likely to do at a boundary

new tectonics powerpoint.notebook

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September 30, 2015

Mar 122:00 PM

http://www.youtube.com/watch?v=RiHRI_Z2Kgs

Mr. Lee layers of the earth song

http://www.youtube.com/watch?v=gyT8Xs6Abk

Mr. Parr plate tectonics song

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Theories:CONTINENTAL DRIFT

This theory stated that all the continents in the world were joined together a long time ago.

The great big super continent (which he called Pangaea) cracked apart into several big pieces and slowly, over time drifted to their present locations.

This theory supposed that Pangaea was whole 250 million years ago when the world was populated with dinosaurs and other extinct creatures

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Scientists believe it looked like this

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1. Landforms: (mountians, coal fields)

2. Fossils: (Mesosaurus, Lystrosaurus, Glossopteris)

3. Climate: (glacier deposits and scratches, fossilized warm/cold "typical" plants and animals)

4. Fit of the continents: Continents look like they fit together

A famous scientist, Alfred Wegener, proposed the theory of continental drift. He believed that by gathering data on

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Fossil evidence6

http://www.youtube.com/watch?v=RiHRI_Z2Kgs

http://www.youtube.com/watch?v=gyT8Xs6Ab-k


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September 30, 2015

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Alfred WegenerInuit guide

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http://www.youtube.com/watch?v=3dbTauY0Vog

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Climate evidence

http://www.youtube.com/watch?v=EkjRLjkCcb0&feature=relatedGreat continental drift video

http://www.youtube.com/watch?v=3dbTauY0Vog

http://www.youtube.com/watch?v=EkjRLjkCcb0&feature=related


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September 30, 2015

Feb 38:33 AM

Why Wegener was a reject.....

or....

Why Wegener's theory was rejected and he died cold and alone on an ice shelf in Greenland....

He couldn't explain HOW the continents got to their present location....that wasn't done for another 30 years

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Wegener's evidence:

1. Fossils of Glossopteris and Messosaurus are found to match up on either side of vast oceans.

2. Ancient climates are recorded in the rock in glacial striations and coal deposits that match up on continents that match up on either side of vast oceans.

3. Landform evidence shows that huge mountain ranges that are the same age, same rock, and same shape fit together on different continents that are separated by vast oceans.

4. The continents seem to fit together like gigantic puzzle pieces. When you put them together, fossils, climate markings, and landforms seem to fit together and line up as if they were made when the continents were all attached.

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Poor Alfred!......

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Proof that Wegener was right!!!!!

This was a new theory... it was based in Wegener's original data of 1. Fit of continents2. Fossils3. Landforms4. Climate

BUT.....Tried to explain HOW the continents were capable of moving

http://www.youtube.com/watch?v=NYbTNFN3NBo&feature=related

Feb 39:57 AM

The Theory of Plate TectonicsProposed in the 50's and 60's

What is the theory?

"...is a theory that describes the formation, movement, and interaction of ... plates."

The theory explains the geological processes that take place (largely on the ocean floor) to make the plates move

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There are 3 Primary pieces of evidence that support this theory....

1. Location of earthquakes and volcanoes

2. Age of the ocean floor

3. Magnetic polarity of ocean floor

http://www.youtube.com/watch?v=NYbTNFN3NBo&feature=related


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September 30, 2015



Sep 2812:25 PM

Like we have discussed

Earth's crust is

broken into big

chunks called

"plates".

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Sometimes these "plates"

move towards each other,

sometimes away from

each other, sometimes

they scrape past each

other.


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September 30, 2015

Nov 98:37 AM

Imagine a million little rubber duckies floating in a pool

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Well...this isn't quite a million but you get the idea..

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Yahooo more duckies!

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All rightlast duckie picture!

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Anyway,

As you swish your arms around in the water you create currents in the pool. Those currents cause the duckies to zoom around in the pool.

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The plates that make up the crust are like the duckies! As currents in the asthenosphere move around, the plates of the crust move too!!! (because the crust touches the asthenosphere)


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September 30, 2015

Nov 98:46 AM

Sometimes the duckies move toward each other

Sometimes the duckies move away from each other

Sometimes the duckies scrape past each other

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But before we go any farther, let's talk density!

Understanding density, will greatly help our understanding of what a lithospheric/crustal plate is likely to do at a boundary and why

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There are 2 kinds of crust:1. Oceanic

2. Continental

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Oceanic crust is very thin, while continental crust is very thick (that's why it isn't covered by water like the oceanic crust is! :) You can see the difference in thickness from the

pictures below:

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A lot of people might make the mistake in thinking that thickness is related to density.

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The best way to think about the density of Earth's crust is to think of continental crust as thick styrofoam: Buoyant and "light", while thinking of oceanic crust as a thin slab of metal: Nonbuoyant and Dense


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September 30, 2015

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Now imagine trying to float both of these things on the surface of the water in a pool. The water in the pool is kind of like the mantle in this example

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By thinking of the crust this way, it becomes easier to imagine what happens at plate boundaries when these types of crust meet at convergent boundaries

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There are three (3) primary type of boundaries

1. Divergent: Two plate moving away from each other.

*common features of diverging plate boundaries include midocean ridges (if diverging is taking place on the ocean floor rift valleys earthquake activity (usually found along the "fracture zones at midocean ridges volcanic activity (lava flows)

Feb 48:11 AM

Convergent boundaries: Where two plates are moving toward each other.

There are 3 types of convergent boundaries...

1. Oceanic/oceanic convergent (subduction)

* common features of oceanic/oceanic subduction include..1. deep sea trenches2. volcanic island arcs3. earthquakes

...remember when two plates move toward each otherthe denser plate will be subducted, in this case it will be the older, colder oceanic plate

2. Oceanic/continental convergent (subduction)...remember oceanic plates are ALWAYS more dense than continental plates so the oceanic plate will ALWAYS subduct

* common features of oceanic/continental subduction include1. deep sea trench2. volcanoes along the coast of the continent3. earthquake activity

3. Continent/continent (COLLISION)...remember continental plates are "light" and NEVER subduct so when they converge neither plate will be subducted. Instead they will collide together and get crumpled and folded into huge mountains

* common features of continental/continental convergence include

1. high continental mountain chains2. earthquake activity



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September 30, 2015


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Transform boundary (two plates scraping horizontally past each other

* common features of transform boundaries

1. earthquake activity

...also known as fracture zones along the midocean ridge


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September 30, 2015




What causes the plates to move?* they're huge!* they're heavy! * what force is so strong that it is capable of moving these gigantic slabs of heavy rock?!!!!!

Three (3) theories for forces that can cause plate movement

1. Mantle convection: convection currents in the mantle, heated from belowby the core shunt the lithospheric plates around likerafts in an ocean

Upwelling areas are associated with diverging boundariesDownwelling areas are associated with converging boundaries


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September 30, 2015

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Like the flow of the "lava" in a lava lamp

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Ridge push: Occurs at midocean ridges

molten rock that rises from the asthenosphere at divergent boundaries wells up into the crack caused by diverging plates. the rock is quickly hardened, but much hotter than the surrounding rock, so it occupies a greater volume, causing it to be elevated above the sea floor.

Colder rock farther away from the M.O.R is colder and therefore more dense (occupying less volume). This denser rock "pulls" on the younger rock pulling it away from the M.O.R.

Associated with diverging plates

a.k.a gravitational sliding...thought to have the least force for moving the lithospheric plates

Feb 49:24 AM

Slab pull occurs at subduction boundaries

associated with converging (subduction) boundaries

the process of subduction forces a cold, dense plate into the mantle. The subducting plate is denser than the surrounding material so continues to sink deep into the mantle as it melts... as this happens it pulls the rest of the plate down with it. (at the same rate new oceanic material is being created at the opposing diverging plate, so the lithospheric plate continues to be created and destroyed in an neverending cycle. very much like a conveyer belt in a grocery store

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So..........if the plates are moving so slowly, how do we actually KNOW that they are moving at all?.......

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good, oldfashioned surveying


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September 30, 2015

Feb 39:02 AM

satellite data

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section 4

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Mountains show evidence of past subduction or collision boundaries (convergence)

Age of the rocks on the ocean floor

Magnetic record of the igneous basalt reveals the latitude of the continent or ocean floor when the lava hardened

Fossils reveal ancient environments

Evidence of glaciation indicates high latitude or high altitude

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http://earth.rice.edu/mtpe/geo/geosphere/topics/plate_tectonics/plate_future.mov

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this is what north america looked like 4.7 4.0 billion years ago...how did it change so much????

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Ancient continents were much smaller. They have slowly grown as the earth has evolved and changed. there are 4 main kinds of growth material that have added land to the original continents (cratons)

http://earth.rice.edu/mtpe/geo/geosphere/topics/plate_tectonics/plate_future.mov


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September 30, 2015

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bound on all sides by major faults.

The rocks and fossils found on the terrane do not match the continent on which it has been attached

The magnetic record in the terrane does not match the continent on which it is attached

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Ahhhh....we love the layers of the earth! They're so dynamic and mysterious


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September 30, 2015

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September 30, 2015

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Feb 38:57 AM

SubductionWhat is subduction? It's when an oceanic plate gets pulled into the mantle at a convergent boundary

This is where the crust gets distroyed!

Documents

CONTINENTAL DRIFT Alfred Wegener proposed the theory · PDF fileThe Theory of Plate Tectonics ... evidence that support this theory ... crustal plate is likely to do at a boundary