Intro:
The Maldives in recent years has had several changes in its geophysical state due to
The Maldives has the 7th biggest coral structure in the world with that being
Darwin's theory was the coral structures that comprise of over 65% of the islands land mass surround and grow around the submerged volcano. His theory was backed by the theory of plate tectonics in which the islands are actually built on not one but several ridges of volcanoes! Due to the subduction of the string of volcanos and the oceanic plates underneath the atoll. The islands long ago submerged slowly from the surface. The landmass we see today was then created slowly through time from decaying coral composition.
The picture above is the structure of the coral composition of the islands.
Coral Reefs:
As the volcano starts sinking the atoll provides the perfect photic zone for coral to thrive in.
My fascination with the Maldives was that these Atolls were created by the gradual growth of dead organisms which are coral. Coral Reefs are composed of Calcium Carbonate (CaC03 which is produced mainly by polyps.) These polyps can be created from the underwater biological structures of dead organisms which have decayed. In our case the polyps which make up the structure of the Atolls live in tropical regions up to 50 meters deep. The reason being is because these structures need copious amounts of sunlight in order to allow photosynthesis to happen. Without photosynthesis most of the underwater organisms cannot convert light into chemical energy. Particularly this abundance of life is commonly found in an area which is called the photic zone.
The anatomy of a sea sponge
Why its cool:
Well now that I have bored you with all this science talk the real reason why this is all so interesting is because the coral structures are truly beautiful with lively colors and exotic shapes. What you should know is that most of these organisms the photosynthesis that occurs in this region is truly special. By using a combination of photosynthesis and having an abundance of zooxanthellae (which are algae organisms that nourish the coral reefs) it gives the coral compositions different textures and shapes which make the structures we all see today.
The coral structure off of Mulaku Atoll.
Why it's relevant to physical geography/geology:
We all know that the atolls we see today are actually the surfaces which are composed of coral composition. But underneath are strings of volcanoes that were mentioned earlier. Due to subduction in that region the oceanic plates are actually shifting very slowly which means that the island is actually sinking. As time goes on these coral compositions deposit calcium carbonate surrounding the area they are inhabiting. Time passes and the coral composition starts to build up on calcium carbonate. So now the last piece of the puzzle is the molding of this island. This "drum roll" magical mysterious force that creates this awesome island is what is called Bio-erosion. Bio-erosion is what exactly what the name is which is a biological force which can be from fish, waves, sponges to anything that can break down the coral structure and help settle these fragments to create reef structures and lagoons. As these structures build up the coral starts to surface. As the polyps die from the surfacing the fragments of the coral reef die and harden creating limestone.
As we can tell the calcium carbonate deposits are building around the island creating a ring shape.
Sources:
http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Geography_of_the_Maldives.html
http://www.fao.org/docrep/010/ai387e/ai387e03.htm
Pictures:
http://darwin-online.org.uk/
http://coralreefcreator.files.wordpress.com/2012/09/p1230062.jpg
http://en.academic.ru/pictures/enwiki/77/Maldives_small_island.jpg
https://geoarchitecture.wordpress.com/2013/08/15/made-ground-2-bio-geology/coral_polyp/#main
https://geoarchitecture.wordpress.com/2013/08/15/made-ground-2-bio-geology/darwin-coral-atolls/#main
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