Sanjeev Sanyal - The Incredible History of India’s Geography

I f someone asked you to point out where India is on the world map, youd probably do it in a jiffy. There it is, jutting into the Indian Ocean with Sri Lanka forming a teardrop beneath its land mass. The image is a very familiar one. But what if you were told that the Indian subcontinent was not always located where it is today? That it was once attached to Africa and Madagascar?

This is a fairly new discovery. For a long time, till the early twentieth century, people thought that continents were fixed land masses. But in 1912, a geologist called Alfred Wegener came up with the theory of continental drift.

Continental drift is the movement of the continents across the ocean bed. Now dont look down at your feet to see if you are movingthis drifting happens very, very slowly, over hundreds of millions of years!

Wegener expanded on this idea in his book The Origin of Continents and Oceans, which was published in 1915. He argued that the present continents all came from one single land mass that later drifted apart. While this sounded strange to people at that time, it explained why the world map looks like a jigsaw puzzle with different countries and continents appearing like they could fit into each other. These countries are far apart but their outlines seem like they could be joined together.

It took nearly fifty years for Wegeners arguments to be scientifically proved! In the late fifties and sixties, a great deal of new geological data established what Wegener had suspected: the earths crust is a patchwork of plates and these plates are moving relative to each other. This led to the modern theory of plate tectonics.

Here is how scientists believe it all happened...

A billion years ago, there was a supercontinent called Rodinia. It was probably located south of the equator but we are still not sure about its exact shape or size. This supercontinent broke up around 750 million years ago and the various pieces, i.e. continents began to drift apart. This period is loosely called the Pre-Cambrian period. There were only single-cell organisms like bacteria alive then.

Did you know?

The Aravalli Range in India is thought to be the oldest surviving geological feature anywhere in the world! These mountains were once very tall, maybe as tall as the Himalayas, but over hundreds of millions of years, they have been eroded down to low hills and ridges. The northernmost point of the Aravallis is the North Ridge near Delhi University. Farther south, near the Gujarat-Rajasthan border, these short hills turn into mountains again. The Guru Shikhar peak at Mount Abu rises to 1722 metres above sea level and is considered to be a sacred place. The Rajput warrior clans claim that their ancestors arose from a great sacrificial fire on this mountain! Despite the significance of the Aravallis, they are under threat today because of reckless mining and quarrying.

Fossil records show that around 530 million years ago, there was a sudden appearance of a large number of complex organisms on the earth. This is called the Cambrian Explosionbut remember that were talking in geological terms. This explosion took millions of years to happen. Over the next 7080 million years, a whole new array of life forms evolved. While all of this was happening, the continental land masses began to reassemble and, about 270 million years ago, fused into a new supercontinent called Pangea.

How did the new world look? As you can see, the Indian craton is wedged between Africa, Madagascar, Antarctica and Australia.

A craton is a large, stable block of earth which forms the centre of a continent.

It was on Pangea that the dinosaurs appeared 230 million years ago. But the earth was still restless and Pangea began to break up around 175 million years ago, during the Jurassic era. It first split into a northern continent called Laurasia (consisting of North America, Europe and Asia) and a southern continent called Gondwana (Africa, South America, Antarctica, Australia and India). You might have heard of the Gond tribe of central Indiawell, this is where the name comes from!

A large number of dinosaur remains have been found in Raioli village of Balasinor Taluka, Gujarat. The site was identified in 1981, and going by the thousands of fossilized eggs found there, it appears to have been a popular hatchery for dinosaur mothers. The fossilized bones of a previously unknown dinosaur, 2530 feet long and two-thirds the size of the Tyrannosaurus Rex, were also discovered. This dinosaur has been named Rajasaurus Narmadsensisthe Lizard King of the Narmada!

It is believed that, first, India, Antarctica and Madagascar separated from Africa around 158 million years ago and then, 130 million years ago, India and Madagascar separated from Antarctica. Around 90 million years ago, India separated from Madagascar and drifted steadily northwards, towards Asia. As this happened, the land mass passed over the Reunion hotspot, causing an outburst of volcanic activity. This hotspot is currently under the island of Reunion in the Indian Ocean and the eruptions it caused then, mostly in the Western Ghats near Mumbai, created the Deccan Traps.

When we say eruptions, its not the conical sort of eruption that you may associate with volcanoes. These eruptions are more like a layer-by-layer oozing that created the stepped, flat-topped outcrops that geologists call Traps. (In the late seventeenth century, Shivaji and his band of Maratha guerrillas used this unique terrain to wear down the armies of the Mughal emperor Aurangzeb. The Traps lived up to their name on that occasion!) In geological terms, this volcanic episode did not last very longjust 30,000 years. But it was a dramatic phenomenon and might well have led to the extinction of the dinosaurs.

As India continued its northward journey, it collided with the Eurasian plate 5560 million years ago. This collision pushed up the Himalayas and the Tibetan Plateau. And the process is still not over! The Himalayas are rising even now by around 5 mm every year, although erosion reduces the actual increase in height. This region is considered to be seismically unstable, meaning that it is prone to frequent and powerful earthquakes.