plate tectonics and continental drift.notebook · plate tectonics and continental drift.notebook 1...

plate tectonics and continental drift.notebook

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March 27, 2014

Feb 310:12 AM Feb 37:48 AM

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

Feb 38:27 AM Feb 38:33 AM

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

1. Landforms: (mountians, coal fields)

2. Fossils: (Mesosaurus, Lystrosaurus, Glossopteris)

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

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


Alfred WegenerInuit guide


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March 27, 2014


Feb 38:38 AM

Fossil evidence

Feb 38:36 AM

Feb 38:39 AM

Climate evidence

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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March 27, 2014

Feb 38:39 AM

Poor Alfred!......

Feb 38:33 AM

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

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

Feb 310:03 AM

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



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March 27, 2014


Mar 268:19 AM

Remember the layers of Earth???

Feb 38:40 AM

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

Mar 268:20 AM

Well the thinnest layer, the crust, is somewhat more complex than you may originally think, considering it's so darn thin....

Mar 268:21 AM


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March 27, 2014

Mar 268:02 AM

Styrofoam VS. Metal

Mar 268:24 AM

Because of the density differences between the types of crust, it will have a HUGE effect on how it moves on the asthenosphere.

Mar 268:25 AM

Because continental crust is so buoyant, it will never get subducted, or pulled down into the mantle. It's like trying to keep a piece of Styrofoam submerged under water

Mar 268:27 AM

Feb 48:02 AM

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 38:46 AM


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March 27, 2014

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

Feb 38:57 AM



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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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


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


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March 27, 2014

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

Feb 49:07 AM

Feb 39:08 AM

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

Feb 39:02 AM

good, oldfashioned surveying

Feb 39:02 AM

satellite data

Feb 39:06 AM


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plate tectonics and continental drift.notebook · plate tectonics and continental drift.notebook 1...

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