For Rodrigues, the youngest island in the archipelago (at least for the emerged part), its formation began about 1.5 million years probably by a volcanic eruption on a ridge at the eastern edge of the Mascarene Plateau. Around the same time, the final form of the Reunion Island was materialising.
Even now, you can see the many basaltic protrusions, multilayer stacks of lava flows or typical formations in the shape of organ pipes that are visible in many places confirming the volcanic origin of the island of Rodrigues. The typical calcarénitic formations assume the existence of a huge lagoon even before the shaping of the island as it is today.
Finally, following a drop in sea level, wind piled sand on the emerging cone and created a system of dunes that acidic leachate from the rain and rotting plants from the surface,have transformed the interior into coarse sandstone. The exploitation of stand stone for building purposes is now prohibited.
Later, a rise in sea level has led to the release of these calcarénitic dunes. In this tender and easily soluble material, considerable internal cavities were formed such as caves one would find in limestone platforms.The sea is responsible for shaping those exposed to the waves to form an irregular coastline dotted with numerous coves.