Continental Drift

Continental Drift

Review of Wegener's hypothesis

Alfred Wegener

Alfred Wegener noticed that South America and Africa appeared to fit together like puzzle pieces. He was certainly not the first person to notice this. But he was intrigued by the idea and thought a lot about it. He wondered if the two continents were once joined and then moved apart? He set out to find evidence to support or refute this idea.

Open Ended

Wegener noticed the continents looked like they fit together. What did he wonder?

Evidence for Continental Drift

• Continent Fit

• Fossils

• Rocks

• Climate

• Glacial

Multiple Select

What evidence did Wegener have that the continents were once joined together?

• Fossils

• Fit

• Rocks

• Climate

• Glacial

Fossil Evidence

Wegener found fossil evidence that the continents were once joined. The same type of plant and animal fossils are found on continents that are now widely separated. These organisms would not have been able to travel across the oceans. So how did the fossils get so far apart?

Open Ended

Why is it strange to find fossils of the same plants or animals on continents that are very far away from each other?

Rock Evidence

Wegener found rocks of the same type and age on both sides of the Atlantic Ocean. He thought that it could not be a coincidence! He said that the rocks must have formed side by side. These rocks then drifted apart on separate continents.

Rock Evidence

Wegener also matched up mountain ranges across the Atlantic Ocean. The Appalachian Mountains were just like mountain ranges in eastern Greenland, Ireland, Great Britain, and Norway. Wegener concluded that they formed as a single mountain range. This mountain range broke apart as the continents split up. The mountain range separated as the continents drifted.

Multiple Choice

Why is it strange that the mountains in Europe are the same type as the mountains in eastern North America?

• It shows that they must have once been the same mountain range and were somehow split apart

• It shows people love to ski all over the world

• It shows that mountains are everywhere

Climate Evidence

Coral reefs are found only in warm water. Coal swamps are also found in tropical and subtropical environments. Wegener discovered ancient coal seams and coral reef fossils in areas that are much too cold today. 

Multiple Choice

Why is it strange to find fossils of coral reefs in COLD places on Earth?

• Coral reefs are pretty cool.

• Coral live in WARM climates, not cold.

• Coral is so colorful.

Glacial Evidence

Glaciers are found in very cold climates near the poles. The evidence left by some ancient glaciers is very close to the Equator. Did glaciers once exist near the equator? Wegener knew that this was extremely unlikely!

Multiple Select

True or false, Glaciers are slowly moving.

• True

• False

Seems good to me...what the heck?

Despite all of this evidence Scientists REJECTED Wegener's theory!!

Why, you may be asking? Well, Wegener was missing one very important explanation.

He couldn't explain HOW the continents could just move around. That's kind of a big deal...

Multiple Choice

Why did scientists end up rejecting Wegener's theory of Continental Drift?

• He had too much evidence.

• They didn't really like him.

• He couldn't explain HOW the continents moved.

• Wegener was a crazy little man.

Summary

• Alfred Wegener made an observation. Africa and South America appeared to fit together like puzzle pieces.

• Wegener then asked an important question and set about to answer it. Were the continents once joined and then they drifted apart?

• Wegener's evidence included the fit of the continents, the distribution of ancient fossils, the placement of similar rocks and structures on the opposite sides of oceans, and indicators of ancient climate found in locations where those climates do not exist today.

• In the end, scientists rejected Wegener's theory because he couldn't explain HOW the continents moved.

Open Ended

State the theory of continental drift.