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Continental Drift Theory. What is Continental Drift Theory? Continental drift theory: Proposed by Alfred Wegener that all the continents were once together as one super continent named… Pangaea (1 Earth / Land). Continental drift theory. How long ago was Pangaea last together.

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continental drift theory1

What is Continental Drift Theory?

Continental drift theory:

Proposed by Alfred Wegener that all the continents were once together as one super continent named…

Pangaea (1 Earth / Land)

Continental drift theory

How long ago was Pangaea last together.

Pangaea was last together 250 Million Years ago

How did they break up?

Wegener could never show how it broke up, he thought they floated apart on the ocean like boats on the water (they drifted with help from waves)


What proof did he have?


1) Continents fit together like a puzzle

Then when you line them up:

2) Mountains match up

3) Rock types match up

4) Plant fossils match up (Glossopteris)

5) Animal fossils match (Mesosaurus)

6) Glacial deposits match

7) Past climates match


Laurasia (Northern Half)

Panthalassa Sea

(1 large Ocean)


(Southern Half)

Pangaea's first split was North and South (like the U.S.)

cdt lab

Purpose – Learn about Continental Drift Theory

Data – Map of Pangaea (label its parts)

10 ?’s

Con –

What is CDT (continental drift theory)?

Research Wegener (find new info).

What were his proofs?

What was Pangaea ?

(give its parts: Northern, southern, large ocean)

How long ago was it last together?

What was Wegener missing?

CDT lab

What did plotting Earth Quakes show?

Plotting Earth quakes revealed the Earth was not 1 solid outer crust. It is made of plates.

(Most appear at plate boundaries, so do volcanoes)

What are plates?

Plates are Large broken up pieces of the Earths crust (Lithosphere).

~ 8 major plates and several minor

other discoveries

Zebra banding: Iron acting as a compass in rock shows the North and South pole have been flipping.

They also appear in a matching pattern on both sides of the Atlantic

Other Discoveries

Using Sonar a Large Mt. Range is found to run down the center of the Atlantic. (Mid Atlantic Ridge)

Rock close to the ridge (in the center of Atlantic) is newest. Far rocks (on both sides by the continents… S. America/Africa) are 250 million years old.


How can this be explained.

Sea floor spreading: theory by Hess (A geologist in the Navy) that the Sea floor is young rock <250 million years old.

Rock is getting created in the center at the Mid Atlantic Ridge and is being pushed outwards.

This is growing the Atlantic Ocean.

Sea floor spreading proves the plates are moving apart

plate tectonics

Putting all this new information together?

Plate tectonics is the movement of Earths Plates. And what happens at their boundaries.

It is CDT + Plates + Sea Floor Spreading

Plate Tectonics

How do plates move?

Plates move due to convection currents in the mantle.


Why do Continents move?

Continents move because they ride on top of the plates.


Layers of the Earth.

  • 1) Core (center): 2 parts
  • A) Inner core (Solid Iron and Nickel)
  • B) Outer core (Liquid Iron and Nickel)
  • 2) Mantle: flowing molten (melted) rock
  • Convection currents move mantle around
  • Lava = molten rock on surface
  • Magma = molten rock under the surface

2B) Asthenosphere – upper part of the mantle,

called plastic mantle because it flows like heated plastic (continents ride on this)

3) Lithosphere – The crust & Rigid Mantle

Ocean crust – Basalt (bass, salt)

d= 3.0g/cm3

Continental crust – Granite (counter tops)


Ocean crust is more dense

the earths interior

What clues do we have about the inside of the Earth if we have never been down there?

To infer about the interior of the Earth we use:

1) Meteorites:

They have iron & nickel cores.

If we started from the same

materials we should have

an iron and nickel core too.

*Shows composition

The Earths interior

2) Earthquakes –

Earthquakes send seismic waves through the Earth. Based on their actions, we can infer a solid and liquid core.

*shows state of matter


3) Lava.

By studying lava you are studying material that was inside the Earth.

*shows hot interior

types of plate boundaries

How can plates move in relation to one another.

Plates can move in 3 ways to each other

1) Divergent – divides or moves apart

2) Convergent – Comes together

3) Transform – Slide past each other

Types of PLATE Boundaries

What happens at a Divergent Boundary?

At a divergent boundary:

1) Plates move apart

2) Plates grow (addition of Lava)

3) Ridges are pushed up

4) Rift valleys are created (Rift ~ Ripped)

These occur on continents too

convergent boundaries

What happens when continental plates with the same Density crash?

Convergent boundaries

When 2 continental plates with the same density converge they buckle up and make mountains like the Himalayas, (Everest is where India collided).


When an ocean plate collides with a continental plate it goes under due to density.

This creates a deep trench in the ocean where the plates meet.

Coastal mountains form where the continental plate rides over and buckles.

The subducted oceanic plate melts, creates magma and volcanoes form.

The oceanic plate is destroyed.


Transform Boundaries:

Many plates slide slowly past each other unfelt. Over time land forms may no longer match up.

If plates get stuck, they will build pressure until they slip and create an Earthquake

(California San Andreas Fault).


What happens at Divergent Boundaries?

Divergent Boundaries: Plates move apart, new ocean plates created, Mid Ocean Ridges, Rift Valleys.

What happens at Convergent Boundaries?

Convergent Boundaries: Plates crash, Mountains, Ocean Plate destroyed, Deep ocean Trenches, Volcanoes.

What happens at Transform Boundaries?

Transform Boundaries: plates slide past each other, Earthquakes.