Continental Drift

A.    The Idea of Continental Drift

1.      In 1910 German scientist Alfred Wegener formed a hypothesis that the Earth’s continents had once been joined together in a single landmass and have since drifted apart.

2.      Wegener named the landmass Pangaea, meaning “all lands”, and existed about 300 million years ago.

3.      Over tens of millions of years, Pangaea began to break apart.

4.      The pieces of Pangaea slowly moved toward their present-day locations, becoming the continents of today

5.      This idea of slow-moving continents is known as continental drift.

B.  Evidence of Continental Drift

1.      When the continents are pieced together to form Pangaea, mountain ranges and other landforms provided evidence for continental drift.

2.      The fossils of the reptiles Mesosaurus and Lystrosaurus and a fernlike plant called Glossopteris have been found on widely separate landmasses.

3.      Evidence from climate change

a.       An island in the Arctic Ocean contains fossils of tropical plants which could indicate that the land mass was once near the equator.

b.      Rocks in mild climates have glacial scarring indicating that these areas once had climates cold enough to produce glaciers.

c.       It was Wegener’s contention that Earth’s climate has not changed, but that the positions of the continents have changed.

C.  Opposition to Continental Drift Theory

1.      Because Wegner could not identify the cause of continental drift, most geologists rejected his idea.