The oldest geological formations of St. Martin are thought to date back 50 million years. These formations consist of sedimentary layers measuring 2000 metres (6,560 ft) in depth and are partly raised above sea level by movements of the Earth’s crust.
The alternating layers consist of siliceous and calcareous material, interspersed with lava flow and accumulations of volcanic ash. These formations are evident in the central hills but most spectacular along the coast of Point Blanche in the south. In a period of later tectonic activity, lifting and erosion occurred again, creating masses of large and small boulders.
About 20 million years ago, a coral platform developed around the island to form Lowlands in the northwest. Many limestone formations are evident in that region.