Aim: How do Continents Drift?

Do Now:

- Take the “Continental Drift Theory” reading from the back of the room.

- After reading the short article, answer the questions on the back.

- You will have 5 minutes for this task.

The Continental Drift Theory

1. Wegener believed the landmasses could all fit together.

2. Wegener did not have enough hard evidence or proof to support his ideas.

3. It took until the 1960’s for new evidence to emerge.

4. Fossils of Glossopteris (a fern plant) are found on many continents. Scientists think the seeds were too large to be carried by wind, and therefore, could not explain how it traveled the great distances between the continents today. This indicates the continents must have been closer.

5. Fossils of Lystrosaurus (swamp-dwelling hippo-like creature) are found on many continents. Scientists do not believe this creature could have swam the great distances between the continents today. This indicates the continents must have been closer.

I. The Continental Drift Theory

- proposed by Alfred Wegener - theorized that the continents

floated around the planet and moved through the oceans.

* ~ 300 mya the continents were all together forming what was called Pangaea = “All Land”

Formation of Pangaea (~300mya)

II. Evidence for Continental Drift

1. The Continental Puzzle

continents fit together like a giant puzzle

2. Matching Fossils- Fossils of the same organisms (plants and animals) are found on different continents.

3. Rock Types and Structures- different mountain ranges across the ocean have the same rock composition and age.

Present (2013) 250 Million Years ago

Pangaea

III. Rejecting a Hypothesis

- Most scientists rejected Wegener’s hypothesis because he could not explain how the continents moved.

But all the evidence

existed and is true!

After hearing about this theory and seeing compelling evidence, what

questions do you have about Wegner’s Continental Drift Theory?

IV. A New Theory Emerges

Theory of Plate Tectonics suggests that the Earth’s surface is composed of rigid plates that move, carrying the continents. (uses Wegner’s evidence)

Closure

Will the continentscome togetherand form a singlelandmass?

- YES – but not for a very long time (about 300 million years).

Plate Tectonics