Drifting Continents Chapter 5 Section 3

Continental Drift Alfred Wegener (1910) hypothesized that all the continents were once joined together as one landmass (Pangaea) and have since drifted apart. Many scientists did not agree with him, so Wegener went out to find support for his hypothesis.

Evidence of Continental Drift What Alfred Wegener found

Continents looked like they fit together

Mesosaurus fossils found on S. America and Africa Mesosaurus fossils found on S. America and Africa. Fresh water reptile not likely to have swum across ocean.

Glossopteris fossils found in Africa, Australia, India, S Glossopteris fossils found in Africa, Australia, India, S. America, and Antarctica. Not likely to find this fern in so many different climates

Warm weather plant fossils found in Greenland Glacial deposits and grooved bedrock found in S. America, Africa, India, and Australia

Similar rock structures found in U.S., Greenland, and W. Europe

Even though Wegener had all this information, scientists did not accept his theory

Sea Floor Spreading Chapter 5 Section 4

What we found out after Wegener died Sea floor spreading - Ocean floor rocks are no older than 200 million years old - Continental rocks are as much as 3 billion years old - Rocks nearest the mid-ocean ridges are the youngest

Sea-floor spreading

Rock record shows reversed polarity in iron containing minerals

Subduction When one plate moves beneath another plate