Alfred Wegener first proposed the theory of continental drift in 1910, suggesting that the continents were once joined together in a supercontinent called Pangaea. Wegener provided three lines of evidence to support his theory: the matching shapes of continental coastlines, matching fossil distributions across continents, and evidence that past climates did not match current continental positions. While his theory was initially rejected due to the lack of a mechanism, it was later supported by the discovery of seafloor spreading in the 1960s, which provided a process to explain how and why continents move over Earth's surface.

1. Continental Drift Theory

2. Alfred Wegener (Vegener)
• As a young scientist,
Wegener was curious
about Earth’s continents.
• In 1910, Mr. Wegener
formed a hypothesis
which stated all the
continents were once
joined together in a giant
landmass.
• He named this landmass
PANGAEA.

3. Theory of Continental Drift, which
states that parts of the Earth's
crust slowly drift atop a liquid
core.

4. Wegener used 3 types of evidence
to prove his theory!
1.Evidence from landforms
2.Evidence from fossils
3.Evidence from climate

5. Evidence from landforms
• The shapes of the
continents seemed to
fit together.
• Mountain ranges and
other features also
lined up.

6. EvidenceEvidence from landformsfrom landforms
The ‘jig-saw’ puzzle

7. The ‘jig-saw’ puzzle
Evidence from landformsEvidence from landforms

8. Evidence from Fossils
• Fossils from one
continent matched
fossils from other
continents.
• Wegener used both
plant and animal
fossils.
Glossopteris: a fern found
on the southern
continents
Mesosaurus: a
freshwater swimming
reptile found in Africa
and South America

9. Long swim for Mesosaurus

10. fossil matches
Evidence from Fossils

11. Evidence from Climate
• Wegener looked at
certain areas on Earth
and their climates
• He noted that the
fossils he found on
certain sections of
Earth did not match
the current climate
Glacier scratches in S.
Africa

12. At first nobody believed Alfred Wegener’s
theory…..
WHY ??!??
He could not prove how or
why the continents moved.

13. Sea Floor Spreading

14. • Seafloor spreading is the
movement of two oceanic
plates away from each
other, which results in the
formation of new oceanic
crust (from magma that
comes from within the
Earth's mantle) along a a
mid-ocean ridge.
Ocean floor spreading was
first suggested by Harry
Hess and Robert Dietz in
the 1960's.

15. • As the plates move apart,
the rocks break and form a
crack between the plates.
• Earthquakes occur along
the plate boundary.
Magma rises through the
cracks and seeps out onto
the ocean floor like a long,
thin, undersea volcano.

16. The magma meets the water, it cools and
solidifies, adding to the edges of the
sideways-moving plates
As magma piles up along the crack, a
long chain of mountains forms gradually
on the ocean floor. This chain is called
an oceanic ridge.

17. Oceanic Ridge

18. The ocean floor gradually extends and the
size of these plates increases.

19. • Seafloor spreading helps explain
continental drift in the theory of plate
tectonics.
• Basaltic magma rises up the fractures
and cools on the ocean floor to form
new sea floor. Older rocks will be
found further away from the spreading
zone while younger rocks will be
found nearer to the spreading zone.

20. • An example of an
oceanic ridge is
the Mid-Atlantic
Ridge. It is one
part of a system of
mid-oceanic ridges
that stretches for
50,000 miles
through the world's
oceans.

21. ..END…