The geology of the Grenadines can be divided into two main areas of interest. First are the reefs and second is the volcanics.

The reefs receive world wide attention as some of the most beautiful and healthy reef ecosystems around the world. The classic reef ecosystem found in the Grenadines is located in the Tobago Cays. On the eastern side of the Tobago Cays is the Horse-shoe Reef. The reef constantly has waves breaking over it, and there are strong currents which flow over and around the reef. Further discussion of the Tobago Cays reef can be found in our Transect Project.

The volcanism is responsible for the genesis of the islands. The Grenadines are dominated by basalt and basaltic andesite volcanism. These lavas differ from those of St. Vincent to the north, and the famous Soufriere volcano. They differ in that the Grenadines basalts are rich in incompatible elements while St. Vincent's basalts are low in incompatible elements.

There is a stratigraphic range from the Middle Eocene to Recent found in the Grenadines. This is the largest stratigraphic range found in the Lesser Antilles. In general the Grenadines are more closely related to Grenada than St.Vincent. This is explained by the fact that there is a continuous shallow bank between the Grenadines and Grenada. In the Grenadines the Lesser Antilles older arc is exposed. It has an age of Eocene to Oligocene. Also in the the Grenadines the younger arc of the Lesser Antilles is superimposed on the older arc. It has an age of Miocene to Recent.