The geology of paradise

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.

Coral boneyard, Laxmanpur beach, Neil Island, Andaman

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!

Rocks on Sitapur beach, Neil Island, Andaman

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.Corals around Neil Island, Andaman 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.

Dead coral, Bharatpur beach, Neil Island, Andaman

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.

The geology of birdwatching in the Andamans

On the descent into the airport at Port Blair I looked out at an unfamiliar town and got a quick impression of lots of wetlands around it (see the featured photo). The Andaman islands are closer to Thailand than to India, but remain on Indian time. As a result, the sun sets by 5:30 in December. The Family and I did not want to lose this first afternoon on the islands. Shaktivel had promised to meet us at the airport so that we could go birding immediately. It turned out that he’d planned to take us to the wetlands I saw from the air. This is called Sippighat.

Sippighat in Port Blair is being reclaimed

It is a wonderful area for water birds. In the first few minutes we had a couple of lifers. But then I noticed that there were trucks dumping mud into the waters in an attempt to reclaim it. Shakti told me that this was farmland until the 2004 Indian Ocean earthquake dropped it below the level of the sea. I hadn’t bothered to look at the geology of the Andamans till then. But now it clicked.

We were on an island which sits at the geologically active boundary between the Indian and Eurasian plates. Three or four million years ago, their collision fractured the plates and created the Burmese and the Sunda microplates. This tectonic activity threw up the island chains. The slow subsiding of the extinct volcanic cones has created the wonderful coral reefs which I saw first from the air. Even now, as the Indian plate is sinking under these volcanic islands, elastic strain is being built up in the continental plates.

Sunset in Sippighat, Port Blair

This strain was partly relieved by the 2004 earthquakes along the Indo-Burman plate boundary. The Andaman islands were repeatedly shaken by enormous after-shocks, each a major earthquake on its own. Sippighat and its wonderful birds (which I will list later) were just the first consequence that we saw. A dry account of the geological catastrophe of 2004 can still inspire awe. A five minute period, almost exactly twelve years ago, shifted the islands downwards by about a meter and changed rice fields into the watery landscape where we now stood.

The calm swampy land glowed in the light of the setting sun. Continental plates shifted catastrophically to create the seemingly peaceful photo you see above: a landscape full of egrets, plovers and bitterns. It would take me the better part of a week to begin to appreciate how much ecological stress persists even today. But this impoverished ecology is much more diverse than what I normally see in Mumbai.