Jigsaw fit of continents
Also called: Bullard fit · Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Class 11, Ch 4 "Distribution of Oceans and Continents"
Meaning
The jigsaw fit of continents is the idea that the coasts on the two sides of the Atlantic look like matching puzzle pieces. This suggests they were once joined. It was the earliest clue for continental drift. Abraham Ortelius, a Dutch map maker, noticed it in 1596. Sir Edward Bullard later tested it by computer. He did not use today's shoreline, which changes as sea level rises and falls. Instead he used the 1,000-fathom depth line on the continental slope, which marks the true edge of a continent. The fit was almost perfect. NCERT dates the work to 1964, and Bullard, Everett and Smith published it in 1965.
Example
The bulge of Brazil in eastern South America fits neatly into the Gulf of Guinea on the west coast of Africa. That is where the two continents once lay side by side.
Don't confuse with
- Rocks of the same age across oceans: The jigsaw fit is about the shape of continents. The rock evidence is about the age and type of rocks matching across the ocean.
Related concepts
- Rocks of the same age across oceans
- Radiometric dating
- Tillite
- Fossil evidence for continental drift
- Mesosaurus