Continental Drift

Observation

• Have you ever noticed how South America and Africa seem to fit together? If you have, you aren't alone.

• Write about what you noticed

What is Continental Drift

• The breaking up and moving apart of the rock plates that the continents sit on.

Sir Francis Bacon

• The first person to notice “continental drift” in the 17th century.

• Pangaea: the name of this “supercontinent”

• 200 million years ago the Earth's continents were joined together to form one gigantic land mass

The Super Continent “Pangaea”•Millions of years ago began to move apart•Continents are still drifting!!!•The Earth's surface is constantly moving and reforming, but so slowly that you or I can't observe it ourselves.

Continental Drift 170,000,000 years ago

Continental Drift 100,000,000 years ago

Continental Drift 50,000,000 years ago

Continental Drift Today

Evidence Supporting Continental Drift

• Alfred Wegener found evidence

1. Shapes match

2. Species match

3. Rocks match

4. Ice match

The Shapes Match

• The continents look as if they were pieces of a giant jigsaw puzzle that could fit together to make one giant super-continent.

• The bulge of Africa fits the shape of the coast of North America

• Brazil fits along the coast of Africa beneath the bulge.

The Plants and Animals Match

• Wegener noted that plant fossils of late Paleozoic age found on several different continents were quite similar.

• This suggests that they evolved together on a single large land mass.

• Fossils have been found on the matching coastlines of South America and Africa, which are now widely separated by the Atlantic Ocean.

The Rocks Match

• Broad belts of rocks in Africa and South America are the same type. These broad belts then match when the end of the continents are joined

The Ice Matches

• Glacial striations on rocks show that glaciers moved from Africa toward the Atlantic Ocean and from the Atlantic Ocean onto South America.

• Such glaciations are most likely if the Atlantic Ocean were missing and the continents joined.

Why Few People Believed

• Wegener's Continental Drift theory was not readily accepted by the science community of his day.

• It was difficult to conceive of large continents plowing through the sea floor to move to new locations.

• What kind of forces could be strong enough to move such large masses of solid rock over such great distances?

Wegner Makes a Comeback

• Recent evidence from ocean floor exploration and other studies has rekindled interest in Wegener's theory, and lead to the development of the theory of plate tectonics.

Continental Drift Cartoons