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The Great Continental Drift

Written by Sheeba Manish

The Mother Of All Continents:

All of the continents drifting apart? It sounds fantastic, but there was a time in the Earth’s evolution there was just one big  land mass. No separate Asia, Africa, Australia, Americas or Europe. All of them together as one big chunk. This continental block was known as Pangaea or all earth. Over time (millions of  years) this land mass started to drift apart and took on the positions that we see today. A German geologist Alfred Wegener proposed the theory of the Continental Drift. He noticed how the continents all fit into each other, not unlike a jigsaw puzzle. No one believed him. Watch his story below:

Proving The Earth Was Pulled Apart

Proving that the Earth was in fact, one big land block that broke into separate masses was not easy to prove. Wegener’s theory was discounted by the scientific community. It took Marie Tharp, a cartographer and Bruce Heezen, a geologist to prove him absolutely right. How was Wegener’s theory proved right?

Scientists of the ocean or oceanographers began using echo soundings to plot data points on the ocean floor. What’s that you say? Ships emitted sonar signals that bounced on hitting the ocean floor. The time used for the signal to come back was used to plot the depth of the sea at that level. Tharp used these points to plot a map of the sea floor. The points when plotted, together showed a vast mountain chain under the ocean floor. Tharp and Heezen plotted data points all along the floors of the oceans of the world and sure enough, the mountain range was there in them all. The range ran for 60,000 km all around the globe. It came to be known as The Great Atlantic Ridge.

220px-tharp__heezen

Marie and Bruce with their findings

Tharp noticed in her findings that the  ridge  seemed to have a consistent chasm along it, which could have only happened if it were pulled apart. This pulling apart led to the continents being separated and moving away, resulting in the continental drift. The Royal Institution has made a wonderful animation detailing how the Continental Drift theory came to be proved.

How Did It Happen:

Pangaea broke into Laurasia in the north and Gondwanaland in the south. A sea named Tethys separated them. Upheavals in the northern hemisphere led to the Caledonian and Hercynian mountains being formed. Hot dry weather and the erosion of mountains covered with iron oxide gave this land mass the name of The Red Continent. The first vertebrates took birth here.

Meanwhile,  in the southern hemisphere, Africa, Madagascar, India and Antartica stay ensconced together like a baby in a mother’s womb. With the passage of time- 76 million years ago – there were many small changes as the southern half started to slowly unravel.

In the last phase of the Earth’s development, lasting 65 million years humans were born. The Alpine range of mountains took their final form. This period is split into Tertiary and Quaternary periods.

In the Tertiary period, Europe was overrun by the sea, right up to Russia and ate into the outlying parts of Africa and America. Upheavals of the earth’s crust saw the formation of the Himalayas and Pyrenees mountains. In the Quaternary period, the Earth started to cool down. Ice sheets covered several parts of the Earth, including current day Russia, England and North America. This then alternated with a period of warming. This cold/hot/cold cycle took place at intervals over the next millions of years. It led to the formation of the arctic, temperate and tropical zones.

pangaea_to_present

With the passing of years and more data, the Continental Drift theory has been proved right over and over again. It also shows how flora(plants) and fauna(animals) which simply couldn’t have crossed over oceans, but could have walked over land can be found on different continents today.

pangea

Today, it may seem like we are all very different thanks to the different continents we live in. There was a time when all of Earth’s land was joined and in it were sown  the seeds of species and cultures, whose variants we see today because of  the great continental drift.

Image sources: Wikipedia Commons

Many thanks to Rebecca Junell for pointing me in the direction of the Royal Institution’s animation on Marie Tharp.

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