DRIFTING CONTINENTS

THE THEORY OF CONTINENTAL DRIFT

• Alfred Wegener was a German scientist who was curious about the relationship of the continents on Earth. • Wegener formed a hypothesis that stated that all

the continents had once been joined together in a single landmass and have since drifted apart.• Wegener called this supercontinent Pangea and it

existed about 300 million years ago.• Over tens of millions of years ago, Pangea began

to break apart and the pieces slowly moved toward the location they are today.

• Wegener’s idea that the continents slowly moved over Earth’s surface became known as continental drift. • Wegener gathered evidence from different

scientific fields to support his ideas about continental drift. • He studied landforms, fossils and evidence that

showed how Earth’s climate had changed over many millions of years.

EVIDENCE FROM LANDFORMS

• Mountain ranges and other features on the continents provided evidence for continental drift. • Wegener pieced together maps of Africa and

South America and noticed remarkable things such as matching mountain ranges .• A mountain range running from east to west in

South Africa lines up with a mountain range in Argentina. • European coal fields match up with similar coal

fields in North America.

  

EVIDENCE FROM FOSSILS

• Wegener also used fossils to support his argument for continental drift.

• A fossil is any trace of an ancient organism that has been preserved in rock.

• Glossopteris was a fernlike plant that grew all over about 250 million years ago.

• Fossils of Glossopteris have been found in rocks in Africa, South America, Australia, India and Antarctica which are continents far away from each other.

• This convinced and proved that Wegener’s theory of continental drift was correct.

EVIDENCE FROM CLIMATE

• Wegener also used evidence of climate change to support his theory of continental drift. • The island of Spitsbergen lies in the Arctic Ocean

where it is very cold and ice covered with a harsh polar climate. • Tropical plant fossils have been found on

Spitsbergen proving that at one point, it was a warm, tropical place. • Scientists have also found that at the time

Spitsbergen was tropical, South Africa was cold.

• Deep scratches in rocks showed that continental glaciers covered South Africa.• According to Wegener’s theory, Earth’s climate

has not changed. Instead, the positions of the continents have changed. • As a continent moves closer to the equator it

becomes more tropical and warm. As a continent moves toward the poles, it becomes colder.

REVIEW:

• What were the three types of evidence Wegener used to support his theory of continental drift?

• Explain Wegener’s theory of continental drift:

• How did Wegener use evidence based on fossils to support his theory that the continents had moved?