One Big Happy Continent
Although we are still searching for answers about Earth’s existence and the organisms that have lived on Earth, what we are certain about and have been taught about since we first started studying geography is that all the nations that are separated by boundaries and oceans were part of one big happy continent called Gondwana or Gondwanaland.
Gondwana was a supercontinent that covered much of the Southern Hemisphere, was in existence since the Neoproterozoic era (550 million years ago). It started breaking up during the Jurassic period (180 million years ago). This separation was brought about by the opening of the Drake Passage. The Drake Passage is a body of water that lies between the South American Cape Horn, Chile, and the South Shetland Islands of Antarctica. This passage separated South America and Antarctica.
Around 120 million years ago, a part of the supercontinent broke off and slowly migrated toward the north at a speed of 5 centimeters per year. But something happened, and the piece of land started gaining speed around 80 million years ago. It started approaching north at about 15 centimeters per year which is twice as fast as the fastest modern tectonic drift. This little speed racer called India collided with Eurasia about 50 million years ago and gave rise to the Himalayas.
Scientists have struggled for years to find out the reason for India’s sudden change in speed. Thankfully, geologists at MIT offered an answer to this question back in 2015. According to them, India was pulled northward by a combination of two subduction zones. Subduction zones are regions inside the Earth’s mantle where the edge of a tectonic plate sinks under another tectonic plate. When one plate sinks, it pulls with it any connected landmasses. Toxic.
That is why geologists believe that two such sinking plates caused India to be pulled northward with twice the power, which is why India drifted so quickly. The geologists even found relics of what may be two subduction zones by sampling and dating rocks that lay in the Himalayan region. They also developed a model of a subduction system and determined that India’s drift velocity could have depended on two factors in the system. One is the width of the subducting plates, and the other is the distance between them. If plates are narrow and far apart, that would cause India to drift at a faster rate.
The group also incorporated the measurement obtained from the Himalayas into their model and found that the subduction of two plates may have indeed driven India to drift at high speed towards Eurasia around 80 million years ago.
Leigh Royden, professor of geology and geophysics in MIT’s Department of Earth, Atmospheric and Planetary Sciences, said that “In earth science, it’s hard to be completely sure of anything, but there are so many pieces of evidence that all fit together here that we’re pretty convinced.” Royden and his colleagues, which included a fellow professor named Oliver Jagoutz and others from the University of Southern California, published their result in the journal Nature Geoscience.
Royden says, “When you look at simulations of Gondwana breaking up, the plates kind of start to move, and then India comes slowly off of Antarctica, and suddenly it just zooms across – it’s very dramatic.”
Shift Not Cause By Volcanos
Scientists believed that in 2011, they found the driving force behind India’s fast drift. According to them, the reason was a plume of magma that rose up from the Earth’s mantle. This plume created a jet-like force of volcano underneath India, causing the subcontinent to drift at such a high speed. However, when other scientists tried to prove this scenario, it was found that any volcanic activity would have lasted for at most 5 million years which is far from the 30 million years that took India took to reach Eurasia.
In 2013, Royden and his team, along with 30 students, trekked through the Himalayas. There they collected numerous rocks and took paleomagnetic measurements in order to determine the origin of the rocks. After research, it was found that almost 80 million years ago, an arc of volcanoes was formed near the equator, which was in the middle of the Tethys Ocean at the time.
A volcanic arc is a sign of a subduction zone, and the group later identified a second volcanic arc to the south of the first one. This was the place from where India first broke away from Gondwana. This data confirmed the team’s theory that the two subducting plates: a northern oceanic plate and a southern tectonic plate that caused India’s drift to Eurasia. And kids, that is ‘How India Met Your(Asia)’