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.