Continental Drift Drifting Continents Continental drift is the idea that continents are moving very slowly, parallel to Earth’s surface. Alfred Wegener.

Continental Drift

Drifting Continents

• Continental drift is the idea that continents are moving very slowly, parallel to Earth’s surface.

• Alfred Wegener proposed that the continents slowly drifted to their present-day locations over millions of years.

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Pangaea

• Approximately 255 million years ago, the continents were one big landmass named Pangaea.

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Evidence for Continental Drift

• Four major pieces of evidence:

1. Fit of Continents

2. Fossil Evidence

3. Rock types and mountain ranges

4. Climate evidence

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1. Fit of the Continents• Africa and South America fit together like a

puzzle.

2. Fossil Evidence

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• Wegener used fossil evidence from a fossil of a fern called Glossopteris.

3. Rock Types and Mountain Ranges• Ancient rocks on the continents match up when you

assemble the continents as Pangaea.

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• Some mountain ranges appear as if they were once connected.

4. Climate Evidence

• Sedimentary rocks record clues about climate.

• The ancient climate of certain locations was very different from the present-day climate.

– Tropical plants in Greenland, glaciers in Africa

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Hypothesis Rejected• Wegener proposed that the same forces of gravity that

produced tides moved the continents.

• Scientists rejected this hypothesis because they did not accept Wegener’s explanation of how the continents moved.

• New technology gathered additional evidence that supported the continental drift theory. (p.172)

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