St Vincent and the Grenadines - 1.

Subduction of the North American tectonic plate under the Caribbean plate gave rise to the volcanic arc of the Lesser Antilles, east side of the Caribbean plate .

The volcanic arc of the Lesser Antilles - external and internal arc - doc in Geology of France - The archipelago of the Lesser Antilles - SVT Grenoble M.Dubernet

The volcanic arc of the Lesser Antilles actually consists of two volcanic arcs.
The oldest dated from the Eocene to the late Oligocene (~ 55 Ma) , and the most recent , dated to the early Miocene (< 5 Ma) to the present, is superimposed on a proto- arc belonging to the Caribbean Mesozoic arc .

Volcanic activity presents two significant deficiencies , each lasting from August to October Ma
The first interruption accompanied the opening of the Paleocene basin of Granada, with the formation of an oceanic crust in the southern part of the basin. The second interruption, at the end of the Oligocene , is the result of a major tectonic event: the collision with an aseismic active Atlantic ridge.
The subduction geometry of the volcanic line was modified in its northern half , with the jump to the west, from the outer arc towards the inner arc. In Neogene, the non- active subduction has lower but significant effects on the tectonics and volcanism of this arc .

                                            A postcard from the Grenadines

The part of the volcanic arc that interests us today is located south of it , between the islands of St Vincent and Grenada : the Grenadines islands .

The main islands are (from north to south): Bequia, Baliceaux , Mustique, Canouan , Mayreau , Tobago Cays , Union and Petit St. Vincent.

         The arc of the Lesser Antilles south - The Grenadines ... between St Vincent and Grenada

Administratively, "Saint Vincent-and-the Grenadines " form a Commonwealth kingdom, independent since 27 October 1979. The formal head of this state is the Sovereign of the United Kingdom of Great Britain and North Ireland, currently Queen Elizabeth II. She does not reside in the country and is then represented by the Governor General of Saint Vincent and the Grenadines .

The Grenadines are marked by two phenomena: the trainer volcanism and a reef ecosystem.

                  The Grenadines - Carriacou / White island - photo Farhad Vladi / Panoramio
The Grenadines - Carriacou / White island - basalt columns at the tip of the island - photo Geoforum
 

The volcanism gave there basalto-andesitic products . The volcano- tourism is featured in Soufriere St. Vincent , north of the Grenadines, which leaves to the Grenadines islands only his turquoise sea, islands with steep cliffs that plunge in the sea, the white sandy beaches and a rich flora and fauna ... a little paradise, well preserved, and sometimes reserved only for billionaires, as Musquito island , frequented by the jet set and the British Royal family. To visit by leaving carried by the trade winds, between December and May, in the dry season !

                  The Grenadines - The Tobago Cays - photo Charterworlds

Five reefs are near the Tobago Cays , including Horseshoe reef , Egg reef and Worlds End reef. The Tobago Cays have served as a backdrop to the film Pirates of the Caribbean, and remain one of the most beautiful spot of diving and surfing .

                            The Grenadines - islets and reefs of the Tobago Cays.

Sources :

- The lesser Antilles island arc  - by Ph.Bouysse, D.Westercamp & P.Andreieff - link

- The lesser Antilles island arc: structure and geodynamic evolution

- University of Windsor - The Grenadine islands - link

- Géologie de la France - L'archipel des petites Antilles - SVT Grenoble M.Dubernet

- About Mustique - link