Transcript Continental Drift - Junction Hill C

The Theory of
Continental Drift
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Continental drift was proposed by Alfred Wegener
He used the following ideas to support his theory:
1. The fit of the continents
2. The distribution of fossils
3. Similar sequence of rocks
4. Ancient climates
5. The wandering of the Earth's polar regions
• Wegener used his observations to hypothesize that all
of the present-day continents were once part of a single
supercontinent called Pangaea
The Fit of the Continents
animation
• Fossils of the same species were found
on several different continents.
• For example, Glossopteris, a fern, was
found on the continents of South
America, Africa, India, and Australia. If
the continents are reassembled into
Pangaea, the distribution of Glossopteris
can be accounted for over a much
smaller area.
Distribution of Similar Fossils
Continental Drift - Rock Sequences
Continental Drift - Glaciation
Sea-Floor Spreading
• In 1962, Harry Hess proposed that new ocean
floor is formed at the mid-ocean ridges. The
ocean floor is produced by magma that rises
from the Earth’s interior.
• Hess suggested that the ocean floor moved
away from the ridge and plunged into an
oceanic trench along the continentals.