The Lesser Antilles and Aves Ridge
The island-arc complex of the Lesser Antilles (Fig. 1) borders the eastern margin of the Caribbean plate where the latter meets and is underthrust by the western Atlantic Ocean floor. The continuity of the topographic features, the seismicity, and the gravity anomalies from the Greater Antilles through the Lesser Antilles and into northern Venezuela establishes the existence of an active tectonic belt through these areas. The main physiographic feature of the Lesser Antilles is the crustal upwarp which is a relatively narrow ridge from Grenada to Guadeloupe but from there northward becomes a nearly flat-topped platform. Islands along the eastern margin of this platform are composed of Eocene to Oligocene volcanics and minor intrusives capped extensively by Miocene limestones, while the western margin is bordered by a chain of younger, Plio-Pleistocene volcanoes.