Along the plate margin is a deep underwater rift valley, which runs between Cuba and Jamaica. This feature is quite close to the Cuban coast to the south of the Sierra Maestra, with water plunging to 6,000 meters deep only a few miles offshore. The northern coastline is gradually emerging from the sea. Old coral reefs have been brought to the surface, so that much of the northern coast consists of coral limestone cliffs and sandy beaches. By contrast the southern coastline is being gradually submerged, producing wetlands and mangroves, with fewer sandy beaches than the north of the island.
Limestone's of various types cover about two-thirds of the island.
In most areas, there is a flat or gently rolling landscape. There are three main mountain areas in the island. Another mountainous area in central Cuba includes the Escambray mountains north of Trinidad, a double dome structure made up of igneous and metamorphic rocks, including marble. Older rocks include marble, and other metamorphic. All rights reserved.