The similarity in outline of the coastlines of eastern South America and West Africa had been noted for some time. The best fit is obtained if the coastlines are matched at a depth of 1,000 metres below current sea level.

Eastern South American and West African
coastlines show the best jigsaw fit

Image: from OU S267 How The Earth Works: Block 2 How Plate Tectonics Works p7

Any areas where there are gaps or overlaps may be explained by :

• Coastal erosion since continental separation
• Coastal deposition since continental separation
• Rises in sea level (eustatic change) since continental separation
• Changes in land level (isostatic change) since continental separation

Geological fit