Transcript Continental Drift

Continental Drift
Chapter 9.1
The Continental Puzzle
• For 300 years, people noticed that the
continents looked like pieces of puzzle
• In 1915, Alfred Wegener proposed that all
the continents had been joined together to
form one continent called, Pangaea.
• This hypothesis was called “Continental
Drift”.
Evidence for Continental Drift
• Matching Fossils
• Rock Types
• Ancient Climates
Evidence #1: Matching Fossils
• Several fossil organisms found on different
landmasses that could not have crossed
the ocean
• Ex: Mesosaurus, a fresh water reptile has
fossil remains in South America and Africa
• Ex: Glossopteris, a plant fossil found in
South America, Africa, and India
• Ex: Lystrosaurus, a land reptile. S.A. &
Africa
How did they get there?
• Some thought that maybe the animals had
crossed on land bridges that are now
underwater.
• However, there are no signs of any land
bridges in the Atlantic Ocean
• Wegener concluded that the landmasses
had been joined in the past.
Evidence #2: Rock Types
• If the continents were once part of
Pangaea, the rocks found in a particular
region on one continent should closely
match in age and type the adjoining region
• Matching types of rocks in several
mountain belts that are separated today
be oceans are evidence of continental
drift.
Rock Type Example
• The Appalachians in North America and
the Mountains in the British Isles and
Scandinavia
• Rocks in those mountains are the same
age and type
• Form a continuous belt if you put North
America next to Europe.
Evidence #3:
Ancient Climates- Glaciers
• Between 220 mya and 300 mya ice sheets
covered large areas of the Southern
Hemisphere- South Africa, South America,
India, Australia.
• If the continents had not moved, then the
ice would have had to move from the sea
to land (very unusual)
• The ice movement makes more sense if
Pangaea had been connected with
Antarctica
Ancient Climates- Tropical Swamps
• Between 220 mya & 300 mya there were
tropical swamps in North America, Europe,
and Siberia.
• Because it was warm in these areas at this
time, Wegener decided that there was not
an ice age causing the glaciers.