St. Martin, like most other Caribbean islands, was formed by volcanic action. As the Caribbean plate moves volcanic activity occurs at its trailing edge and magna from the earth's core swells up from the rifted crust.
Millions of years ago, St. Martin, together with St. Barths in the East and Anguilla in the North, formed one landmass. Tectonic activity caused the mass to break apart to form the islands as they are today.
Volcanic activity ceased eons ago but the materials deposited formed basalt, porphyrite, diorite and the volcanic andesite, materials that along with coral reefs formed the hills, lagoons, valleys and beaches. The hills, valleys and wetlands are ecosystems that support varying plant and animal species and each carries inherent aesthetic value.