lesson
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If you look closely at a world map, the eastern edge of South America looks like it could lock right into the western coast of Africa.
In 1912, German scientist Alfred Wegener noticed this fit and proposed continental drift, the idea that Earth's continents were once joined as a single giant landmass and slowly moved apart over millions of years.
He named this ancient supercontinent Pangaea, which comes from Greek words meaning "all lands."
📊Interactive before-and-after slider showing the jigsaw fit of continents. On the left side, modern world map showing South America and Africa separated by the Atlantic Ocean. A draggable slider handle lets the student pull South America east to show it fitting neatly into the African coastline like two puzzle pieces. Include clear labels 'South America' and 'Africa' and a highlighted glowing boundary where the continental shelves match.
Coastline shapes were a great clue, but critics argued it was just a coincidence. What solid clues did Wegener find buried in the dirt to prove these lands were once touching?
Fossil Evidence Across Oceans
Wegener found identical fossils of creatures that could never cross an ocean scattered across continents separated by thousands of miles of saltwater.
For example, Mesosaurus was a small freshwater reptile whose bones appear only in eastern South America and southwestern Africa. Because it lived exclusively in fresh lakes and rivers, it could not have swum across the vast, salty Atlantic Ocean.
He also found fossils of Glossopteris, a tree with heavy seeds too large to be carried across oceans by the wind, preserved across South America, Africa, India, Australia, and Antarctica.
📊An interactive map showing southern Pangaea (Gondwana) assembled together. Four distinct colored ribbon bands stretch smoothly across the joined landmasses: an orange band for Mesosaurus (South America to Africa), a green band for Glossopteris (spanning South America, Africa, India, Antarctica, Australia), a purple band for Cynognathus, and a yellow band for Lystrosaurus. Hovering or clicking each ribbon reveals a small illustration of the fossil organism and a short label explaining its habitat.
Some scientists at the time thought these animals crossed ancient "land bridges" that later sank into the sea. But rock density physics proves large continental bridges cannot simply sink into the dense ocean floor without leaving a trace.
Fossils showed that life was connected, but what about the actual ground beneath these animals' feet?