1. Chapter 17 Plate Tectonics
Section 17.1 Drifting Continents

2. Drifting Continents
Earth’s surface appears unchanged during a human lifetime.
On the geologic time scale Earth’s surface is changing at a rate to great to imagine.

3. Early Observations
Matching coastlines of continents on the opposite side of the Atlantic Ocean suggested that the continents were once part of a larger single continent.
Eduard Suess called the large single continent Gondwanaland

4. Continental Drift
Introduced by German scientist named Alfred Wegener in 1912.
The hypothesis states that the Earth’s continents were joined as a single landmass
The landmass broke apart about 200 million years ago
The continents slowly moved into their present position.

5. Pangaea
Modern reconstruction of Pangaea, ca. 255 million years ago

6. Evidence of Continental Drift
Wegener supported his hypothesis of continental drift with rock types, fossils and ancient climatic data
Location of sedimentary rock
Coal in Antarctica places it closer to the equator
Glacial deposits found in Africa, India, Australia, and South America suggests they were closer to the poles.

7. Hypothesis Rejected
Wegener hypothesis was not accepted at first because he couldn’t explain how the continents moved or what cause their motion.
After Wegener died in 1930, his continental drift hypothesis was shelved until the 1960s when it was revisited because of new evidences.