The coastline and surface of Aldabra
The atoll is made of reef limestone dating back to the Pleistocene, with irregular striation, holes and prominent on the eastern side and sand dunes on the south coast. The coastline is characterized by undercut cliffs and irregular coral formations, the "champignons".
The land surface comprises limestone of about 125,000 years age, which has uplifted many times above the sea level. The surface conditions are crisscrossed and riddled with pot holes and pits, and well-preserved coral and mollusc fossils can be found in the limestone across the atoll, many retaining their original coloration. In the eastern zone of the lagoon, though the surface is continuous, sediment beds are also seen.