Petite Martinique islet is a triangular-shaped islet with a double facies located in the northern part of Baie du Robert. It presents a first brecciated facies formed of hyaloclastites, that is to say fragmented volcanic rocks produced during the sudden encounter of a lava flow with water. This is covered by a second facies of massive flows. The morphology of the islet is convex in its eastern part and concave in its western part occupied by a cove with very fine and worn sand. This protected site, classified as neither too degraded nor too preserved, is the subject of increased measures of preservation on its southern and south-eastern fringes prohibited to visitors.