2. • In 1910, Alfred Wegener
developed the hypothesis
that all the continents had
been joined together in a single
land mass and have drifted apart.

3. • This single land mass was called
Pangaea (latin for “all lands”)

4. • The idea that the continents are
slowly drifting apart is known as
continental drift.
•He published his evidence in a book
called Origin of Continents and
Oceans in 1915.

5. Evidence From Landforms
• Wegener pieced together maps that
showed mountain ranges that
matched up in South Africa and
South America.
•European coal mines matched up
with coal mines in North America.

6. Evidence From Fossils
• A fossil is a trace of an organism that has
been preserved in rock.
• Fossils for Mesosaurus
and Lystrosaurus were
found in places now separated by oceans.
• Neither reptile could have swum long
distances across salt water.

7. Evidence From Fossils
• Another example was
Glossopteris which is a fernlike
plant that lived 250 million
years ago. It was found in rocks
in Africa, Australia, India and Antarctica.
• The seeds of this plant could not have
been carried by the wind and are too fragile
to survive an ocean trip.

8. Evidence From Fossils
• Wegener concluded that fossils of the
reptiles separated by an ocean that they
could not have swum and the widespread
occurrence of the fern’s fossils supported
his hypothesis of continental drift.

9. Evidence From Climate
• Spitsbergen is an island in the Artic Ocean north of
Norway.
• The island is ice-covered with harsh polar
climates.
• Fossils of tropical plants were found on this island.
When these plants lived 300 million years ago, the
island must have had a warm and mild climate.
•Wegener concluded that the island must have been
located near the equator.

10. Evidence From Climate
• Geologists also found evidence that at the same
time it was warmer in Spitsbergen, it was much
colder in South Africa.
• There is evidence that continental glaciers once
covered South Africa.
•Continental Glaciers are thick layers of ice that
covered hundreds of thousands of square
kilometers.
•The climate of South Africa today is too mild to
have sustained continental glaciers.

11. Explanations
• Wegener also attempted to explain how
the drift took place and offer a new
explanation for how mountains form.
• He thought that when the drifting
continents collide, their edges fold or
crumble.
•The folding continents slowly push up
huge chunks of rock to form mountains.

12. Scientists Reject Wegener’s Hypothesis
• What forced or pulled the continents
apart?
• Geologists would have to reject their
own theories of how mountains form.
• Geologists in the early 1900 thought
that the Earth was cooling and shrinking.

13. Scientists Reject Wegener’s Hypothesis
• According to this idea, the crust would
wrinkle all over the Earth.
• Mountains are formed in narrow bands
along the edges of the continents.
• Wegener’s theory was rejected until in
the 1950’s when new evidence about the
Earth’s structure caused scientists to
reconsider the hypothesis.