The Story of a Volcanic Island in a Subduction Zone

Grenada is part of the Lesser Antilles volcanic island arc. It has a mountainous interior with a mixed topography of high peaks and deep, narrow valleys. 

Photo taken December 2013 during my cruise to the Caribbean. In the image you can see the mountainous landscape of Grenada.

Today Grenada looks like the above image, but how did it come to be?

About two million years ago, Grenada was a submarine volcano located along what is now known as the Lesser Antilles subduction zone. A subduction zone is a convergent boundary between two tectonic plates where the more dense plate is subducted, or sinks, under the less dense plate. In the Lesser Antilles subduction zone, the oceanic crust of the South American Plate is being subducted under the oceanic crust of the Caribbean Plate. As the South American Plate is subducted, it losses volatile materials that partially melt the mantle of the overriding plate. This generates magma that extrudes through the lithosphere of the Caribbean Plate because it is less dense, resulting in volcanic eruptions. 

This ongoing process created a chain of volcanic islands, including Grenada, called the Lesser Antilles island arc.

Example image of a subduction zone forming an island arc.

http://www.london-oratory.org/chemistry_folder/Revision/Earth&Rocks/New/student%20workbook%203.htm

Map of the Lesser Antilles showing Grenada as part of the island arc. 

http://whatscookinginyourworld.blogspot.com/2010/05/day-15-barbados-fried-grouper-with-cou.htm

There are two active volcanoes of note in Grenada that are part of the volcanic chain.

Image showing where Kick 'em Jenny and Mount Saint Catherine are located in the Lesser Antilles volcanic arc.
http://www.thedominican.net/articles/platpays.htm

Kick 'em Jenny is a submarine volcano located 8 km off the coast of Grenada. It is the most active volcano in the Lesser Antilles, erupting about every ten years. For now, there isn't much immediate danger from the volcano since it is too deep for eruptions to reach the surface. However, due to its rate of ascension it may rise above sea level in the next 100 years or so.

Underwater image of Kick 'em Jenny
https://www.youtube.com/watch?v=6EEj0Maq4q0

Mount Saint Catherine is the youngest of the five volcanoes in Grenada. It is a stratovolcano, so called because it is made up of different layers, or strata. This type of volcano is common in subduction zones. It has not erupted in recorded history, but there are signs of volcanic activity in that area from as long ago as two million years, during the Pliocene Period. There is a slim chance that the volcano may erupt, but for now it poses little threat to the inhabitants of the island.

Panorama image of Mount Saint Catherine
http://www.panoramio.com/photo/85189254

References:

http://en.wikipedia.org/wiki/Caribbean_Plate

http://en.wikipedia.org/wiki/Subduction

https://www.youtube.com/watch?v=6EEj0Maq4q0

http://en.wikipedia.org/wiki/Lesser_Antilles

http://en.wikipedia.org/wiki/Grenada

http://www.renewton.plus.com/geology/talks/2012/Tale%20of%20two%20islands/index.htm
http://en.wikipedia.org/wiki/History_of_Grenada
http://en.wikipedia.org/wiki/Island_arc
https://www.oas.org/dsd/publications/Unit/oea51e/ch06.htm