Ritchie’s archipelago lies a little east of Port Blair. This group of islands includes Havelock and Neil Islands, often considered to have some of the best beaches in the world. The white sand beaches, the clear water and the warm sunshine seem appropriate to the quiet lifestyle of the locals. I could imagine myself settling down to months of slow life here.
Walking along the soft sand one occasionally comes across patches of rubble like the one you see in the photo above. They are pieces of broken coral, the bones of the sea, piled up in these little boneyards. When I saw them I began to wonder about the geological processes which form these little bits of paradise. Although coral reefs are spread across the world, their total area is about that of the state of Maharashtra. In terms of area, this is one part in a thousand of the world’s oceans, but it contains a fourth of all ocean life!
Our understanding of coral islands such as Neil and Havelock comes from Darwin, the master of careful scrutiny and understanding. He figured that such islands are volcanic. In the shallows around these new islands corals begin to accumulate. As the volcanic cone subsides, the corals grow upwards and outwards in the shallow waters. If their upward growth keeps pace with the sinking of the island, then eventually they form the wonderful reefs we saw around the islands (there is a brain coral at the bottom of the photo on the right). Too slow, and they would become drowned reefs. The volcanic rocks which supported the initial growth are also visible around these islands, as you can see in the photo above. The coral reef system is young, only about ten thousand years old.
The Andaman islands have been through a geological catastrophe about a decade ago. The 2004 Indian Ocean earthquake which generated a devastating tsunami was centred near these islands. You can see its devastating effects on the coral ecosystem even today. The sea bed rose by almost a meter, popping a large area of corals above the water and killing them. The great diversity that one sees in scuba dives off the coast of these islands is a fraction of what was there even as recently as 2001. Coral reefs are also sensitive to a variety of easily avoidable man-made perturbations: dumping of untreated organic waste such as sewage and chemicals from agricultural runoffs and even sunscreen. A little awareness for the next few decades would be enough to let this ecosystem recover.