Plate Tectonics &

Continental Drift• What is continental drift?

• What is plate tectonics?

• What is the difference?

• What are plate boundaries?

Continental Drift

Alfred Wegner is a famous German Scientist who first thought that atone time all of the land masses of theworld were one large continent. He named

this great land mass Pangaea.

Wegner’s theory of continental driftstated that Pangaea split apart andthe one large continent became thecontinents that we know today.

The continents are still in constant motion.

Alfred Wegner had solid proof that his theory was accurate. He couldn’t prove what force was great enough to move the great continent of Pangaea apart, so his theory was rejected.

• Fossils- he used fossils to help prove his theory because he found fossils of dinosaurs on two continents that are now separated by oceans. These creatures could never have swam across the ocean and survived so they must have been together at one time so they could have walked across.

• Climate- he found proof of tropical plants in Antarctica and glaciers in Africa. This helps prove his theory because the current climate would not be able to sustain these findings.

• Land forms- Wegner found that the current continents fit together like a puzzle and that if you could push some continents together the mountain ranges line up.

1. Who was the scientist who came up with the theory that all the continents were at one time one large continent?

A) Glossopteris B) Wilson C) Wegner D) Continental

2. Select the item below that did NOT help support the theory of Continental Drift.

A) climate B) landforms C) fossils D) clouds

3. Scientists widely accepted the theory of Continental Drift when it was first introduced.

True False

Plate Tectonics• Many years after Wegner’s

theory of continental drift was rejected scientists took another look at his theory and developed a new theory which better explained how the continents could be moving.

• Wegner proposed that the continents were just floating on the ocean and moving that way. Through plate tectonics the idea of how the plates move was well explained. The world is made up of a number of large plates that float on the asthenosphere. The convection current in the asthenosphere is causing the plate movement.

• These plates move due to the convection currents in the asthenosphere.

• When one plate moves it effects all of the other plates. These plates either contain land, ocean or both.

• We can not feel this movement because it occurs over millions of years. The amount of movement in the plates annually is measured in centimeters.

4. Plate tectonics was the theory that: A) Only the land moves around the Earth.

B) The land and oceans were on a number of plates that float on top of the asthenosphere.

C) Dinner plates should always be brought to the sink and rinsed off.

D) The dinosaurs helped to move the great landmasses.

5. The plates floating on top of the asthenosphere move due to:

A) Convection currents B) Snow storms

C) The density of the core D) They are so light

Plate Boundaries

• Transform boundaries

• Divergent Boundaries

• Convergent Boundaries

Transform Boundaries

• Along transform boundaries, crust is neither created nor destroyed.

• This is a place where two plates slip past each other, moving in opposite directions.

• Earthquakes occur frequently along these boundaries.

Divergent Boundaries• The place where two plates move

apart or diverge, is called a divergent boundary.

• Most divergent boundaries occur at the mid ocean ridge.

• Divergent boundaries also occur on land. When a divergent boundary develops on land, two of Earth’s plats slide apart.

• A deep valley called a rift valley is formed

Convergent Boundaries• The place where two plates come

together, or converge, is called a convergent boundary.

• When two plates converge the result is called a collision.

• When two plates collide the density of the plates determines which one comes out on top. If the plates are crust to crust generally a mountain will be formed,

• There can be any combination of plates that collide, crust to crust, ocean to ocean or crust and ocean.

6. The type of boundary where there is a collision of plates is called:

A) Transform B) Divergent C) Convergent

7. The type of boundary where two plates slip past each other is called:

A) Transform B) Divergent C) Convergent

8. The type of boundary where two plates move apart is called:

A) Transform B) Divergent C) Convergent

That’s all folks