Alfred Wegener supported his theory of continental drift (which later contributed to plate tectonics) with several key pieces of evidence:
- Fit of the Continents: Wegener observed that the coastlines of continents such as South America and Africa fit together like pieces of a jigsaw puzzle, suggesting they were once joined as a single landmass he called Pangaea
- Fossil Evidence: Identical fossils of extinct plants and animals were found on continents now separated by oceans. For example, fossils of the reptile Mesosaurus were found in both South America and Africa, and fossils of Lystrosaurus were found in Africa, India, and Antarctica. These species could not have crossed oceans, indicating the continents were once connected
- Geological Similarities: Wegener noted matching rock types, mountain ranges, and geological structures on continents now far apart. For instance, the Appalachian Mountains in North America closely match mountain ranges in Greenland, Ireland, and Norway, implying they were once part of a continuous range
- Climatic Evidence: Glacial deposits and striations were found in now tropical or temperate regions such as South Africa, India, and Australia, while fossils of tropical plants were discovered in Antarctica. These climate anomalies made sense if continents had moved from different latitudes
Though Wegener lacked a mechanism for how continents moved, his multidisciplinary compilation of evidence from geography, paleontology, geology, and climatology laid the foundation for the modern theory of plate tectonics, which was later supported by discoveries such as seafloor spreading
