About a hundred years ago, Alfred Wegener suggested that the continents were once joined in one supercontinent, Pangaea, and have drifted apart. His evidence included the way the coasts of South America and Africa fit together like jigsaw pieces, matching rock layers on both sides of the Atlantic, and fossils of the same land reptile, Mesosaurus, found in both continents. It could not have swum across an ocean.
Many scientists rejected the idea because Wegener could not explain what moved the continents. Later, mapping of the sea floor found ridges where new crust forms, and rocks either side record the Earth's magnetic field flipping in matching stripes. This evidence led to the theory of plate tectonics.
Worked example
How do Mesosaurus fossils support continental drift?
- Mesosaurus lived in fresh water and could not cross an ocean.
- Its fossils are found in both South America and Africa.
Answer:So the two continents must once have been joined.
Key words
- Pangaea
- the supercontinent of about 250 million years ago
- continental drift
- the idea that continents move
- evidence
- observations that support or reject an idea
- sea-floor spreading
- new ocean crust forming at ridges
New questions every time.
NGSS-referenced: MS-ESS2-3