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Alfred Wegener: Father of Continental Drift
Pangaea, matching coastlines, and the road to plate tectonics
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Alfred Wegener was a German scientist who proposed in 1912 that Earth’s continents had slowly moved over geologic time. He argued that the continents were once joined in a supercontinent called Pangaea, which later broke apart and drifted to their current positions. His idea mattered because it challenged the belief that continents and ocean basins were fixed in place. Although many scientists rejected his explanation during his lifetime, his evidence helped launch a major change in Earth science.
Wegener used several lines of evidence, including the matching shapes of continental coastlines, identical fossils found on widely separated continents, and similar rock layers and mountain belts across oceans. His main weakness was that he could not identify a convincing force strong enough to move continents through solid rock. In the 1960s, new evidence from seafloor spreading, magnetic stripes, earthquakes, and ocean trenches led to the theory of plate tectonics. Plate tectonics explained continental drift by showing that continents ride on moving plates of Earth’s lithosphere.
Key Facts
- Alfred Wegener lived from 1880 to 1930 and proposed continental drift in 1912.
- Pangaea was a supercontinent that existed roughly 300 million years ago and began breaking apart about 200 million years ago.
- Continental drift states that continents have changed position over time instead of staying fixed.
- Key evidence included matching coastlines, fossils such as Mesosaurus and Glossopteris, and similar rock formations on different continents.
- Wegener’s hypothesis was not widely accepted at first because he lacked a strong mechanism for continental motion.
- Plate speed = distance moved / time, and modern plates commonly move a few centimeters per year.
Vocabulary
- Continental drift
- The idea that continents have slowly moved across Earth’s surface over geologic time.
- Pangaea
- The ancient supercontinent that included most of Earth’s landmasses before they separated.
- Plate tectonics
- The modern theory that Earth’s lithosphere is divided into moving plates that interact at their boundaries.
- Fossil correlation
- The matching of similar fossils in different places to infer past connections between landmasses.
- Seafloor spreading
- The process in which new oceanic crust forms at mid-ocean ridges and moves outward on both sides.
Common Mistakes to Avoid
- Saying Wegener proved plate tectonics in 1912, which is wrong because he proposed continental drift before the mechanism of moving plates was understood.
- Using only the fit of coastlines as evidence, which is incomplete because Wegener also used fossils, rocks, mountains, and climate clues.
- Thinking continents plow through ocean crust by themselves, which is wrong because continents are carried as part of larger tectonic plates.
- Assuming rejection of Wegener’s idea meant his evidence was useless, which is wrong because much of his evidence later supported plate tectonics.
Practice Questions
- 1 South America and Africa are moving apart at an average rate of 3 cm per year. How far apart would they move in 10 million years? Give your answer in kilometers.
- 2 A fossil species is found in matching rock layers in eastern South America and western Africa. If the rocks are 250 million years old, what does this evidence suggest about the positions of the continents at that time?
- 3 Explain why Wegener’s continental drift hypothesis became more accepted after scientists discovered seafloor spreading and patterns of earthquakes and volcanoes.