The Jigsaw Continents
Do South America and Africa fit together like puzzle pieces?
Over 100 years ago, a scientist named Alfred Wegener noticed something strange: if you look at a map, the east coast of South America and the west coast of Africa look like they could fit together, like two puzzle pieces. Nobody believed him at first — but he turned out to be right.
Drag the slider through 300 million years and watch the Atlantic Ocean close up — see if you can spot the ancient mountain belt stitching the two continents together once it does.
Colour = height: green and tan for low land, brown and white for mountains. Blue is ocean.
Why does this matter?
The jigsaw fit was one of the very first clues that continents move at all. Wegener also noticed matching fossils and matching rock layers on both sides of the ocean — evidence that only makes sense if those two lands were once joined.
The mountain range you can see stitching South America to Africa in the oldest map is real too: it’s the ancient root of the same mountain-building event that also raised the Appalachians in North America — one continuous belt, later torn apart by the Atlantic Ocean opening between them.
How do scientists actually know where continents used to be?
Wegener could only compare shapes — coastlines, fossils, rock layers. Today scientists have a much more precise clue hiding in the ocean floor itself. When new sea floor forms at a spreading ridge, the cooling rock locks in the direction of Earth’s magnetic field at that exact moment — and every so often, over millions of years, Earth’s magnetic field actually flips, north and south swapping places.
That leaves a barcode-like pattern of stripes frozen into the sea floor on both sides of every ridge, perfectly mirrored, getting older the further out you go. By measuring those stripes — plus fossils, rock ages, and other real measurements — scientists can wind the plates back like a movie in reverse and calculate exactly where they must have been at any age. That’s the same kind of real reconstruction every map in this suite is built from.
Try it yourself
- Drag slowly from Today back to 300 Ma: at roughly what age does the Atlantic Ocean stop looking like an ocean at all?
- Look at the oldest and newest maps: which parts of the coastlines line up most closely? Is it a perfect fit everywhere, or just in some places — and why might a 300-million-year-old coastline not match up exactly, even when the reconstruction is right?
- Wegener didn’t have satellites or computers — just maps, fossils, and rocks. What other clues do you think he might have used?