Download Continental Drift

Continental Drift
Alfred Wegener
• Proposed that the
continents were once
joined as a
supercontinent called
Pangaea.
• Pangaea= Greek for
“all the Earth”
Wegener’s Evidence for
Continental Drift
1. Similar Rock Types
Wegener found rocks
of similar
composition and age
on Africa and S.
America
Wegener’s Evidence
2. Fossil Evidence
Same species of land
animals found on
opposite sides of
Atlantic Ocean
Wegener’s Evidence
3. Climate Evidence
 Coal deposits and fern
fossils in Antarctica
 Glacial deposits in India,
S. America, Africa,
Australia
hint: These locations
must have once been at a
different latitude (further
north or south!)
Wegener’s Evidence
4. Mountain Belts
Similar mountain
ranges on different
continents now
separated by water
Wegener’s ideas were rejected because…
he couldn’t explain how or why the
continents drifted
Possible explanations
• Rotation of Earth
• Physicists “No way!”
• Continents plow
through ocean crust
• Fractures?
Proof of Continental Drift
1940’s-50’s using
SONAR &
magnetometers:
Mid-Ocean Ridges
(MOR’s) = spreading
centers
Deep-Sea Trenches