THE STORY OF CONTINENTAL DRIFT

In the year 1911, Alfred Wagener, a geophysicist and meteorologist, looked at the world map a bit differently. He visualized what if the continents are actually like different pieces of a big puzzle. He tried matching the coastlines of different coastlines and Voila! It worked. The continental shelf of the Americas fit closely to Africa and Europe. Antarctica, Australia, India and Madagascar fit next to the tip of Southern Africa. He presented an extraordinary hypothesis about matching coastlines of the continents across the world – The theory of continental drift. Continental drift means that our continents are moving around the earth at a very low speed, but when we look at a bigger time scale, like millions of years, the drift is significant.

Remember our last discussion on seismicity of Indian subcontinent? We came across subduction zones and plate boundaries. Now we can delve deeper into the root of these intimidating scientific terms – plate tectonics – the mechanism of continental drift. Now, let’s get back to Alfred Wagener in 1911. He noted a few similarities in the shape and location of our continents. Apart from the continents fitting together like a jigsaw puzzle, he found that similar fossils were discovered in South America, Africa, Antarctica and Australia. He analyzed the geology of mountain ranges on both sides of the Atlantic Ocean and concluded they are structurally similar and have same type of rocks. However, the observational evidences he presented were met with heavy criticism from geologists of that era. Reason, the mechanism behind the plate tectonics was missing. What was causing the continents to drift and float on the Earth’s surface? He could not explain. After a few years of struggle, his hypothesis remained a hypothesis.

It wasn’t until 1950s that development in magnetism and several expeditions across Atlantic Ocean and India showed that Wegener was indeed, right. The Atlantic Ocean seafloor was found to be spreading, i.e. new ocean floor was being created. This resulted in a paradigm shift in the field of geology and earth sciences. Unfortunately, Wegener could not live to see himself being recognized as the founding father of one of the major scientific revolutions of the 20th century. Now with the advent of GPS, we can monitor the movements of continents in real time. It is now possible to revisit prehistoric and future continental positions based on the current movement.

Discovery of continental drift opened new doors to understand several aspects of earth’s interior, two of them being earthquakes and volcanism. Continental drift occurs due to movement of the tectonic plates around the earth. Tectonic plates are large landmasses floating over molten magma. They meet at plate boundaries and these boundaries are the most earthquake prone regions in the world. If we look at the Pacific Ocean, we find that the continents of Asia, Australia, North America and South America roughly encircle it and contain many plate boundaries and large volcanoes. This region is popularly called as Pacific Ring of Fire. It’s not a mere coincidence or God’s wrath, that Japan, West coast of USA, New Zealand and Indonesia receive earthquakes throughout the year.

Indian subcontinent has always been the favourite amongst the geologists. There are several features which make it unique among all tectonic regions. Until 140 million years ago India was sitting comfortably with Madagascar near African East coast. Then, it started drifting towards Asia and began colliding with Eurasian plate about 55 Million years ago. The result is seen in the form of the Himalayas. Well, the journey from Africa to Asia wasn’t devoid of catastrophic events. India passed over several magma plumes, i.e. the regions where earth releases magma/lava from its interior which deposited and solidified over the course of time. We know these deposits as the famous Deccan Traps and other smaller plateau regions, like Rajmahal. It is speculated that probably the Indian plate was moving at the fastest rate compared to the other plates, at around 20 cm/year. It is also theorized that melting of rocks because of these plumes released massive amount of volcanic gases which caused extinction of dinosaurs. We are sitting on a region which has such a deep rooted history. It is not wrong if we say that the earthquakes we witness in and around India nowadays, are not random. Their script was written millions of years ago.

As we finish this, seismologists have already warned of a great earthquake considering the recent earthquake swarms in and around Delhi.

Let’s wait and watch, and be prepared.

2020 couldn’t be more despicable.