The Journey of the Continents

Have u ever observed our world map and wondered why the shape of the continents

are unique and why there are similarities between certain coastlines of different continents? We all know that there are 7 continents and 5 oceans on earth, but it hasn't always been like this. There is a theory stating the concept of a supercontinent and its called  Continental Drift Theory. Let's have a brief look at this theory, its evidences and draw backs. 

Continental drift describes one of the earliest ways geologists thought continents moved over time. The below map displays an early supercontinent called "Pangea", which eventually moved to form the continents we know today. There are several evidences that encouraged the revolutionary theory of continental drift which is originally given by Alfred Wegener in 1912.

Evidences for Continental Drift Theory :

• Tectonic Plates : There are 2 kinds of crusts depending on the composition : Continental crust and  Oceanic crust. Continental crust is inherently lighter where as oceanic crust is created at the spreading centers which drives the system of plates in a chaotic manner resulting in Orogeny (An event that leads to both structural deformation and compositional differentiation) and areas of isostatic (Equilibrium in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses) imbalance. The location of the present elevated landmasses like mountains, plateaus coincides with this theory.
• Fossils : Different fossils of similar plants and animals are found across various locations in different continents suggesting that they were once joined.
• Complementary Coastlines : We can see several continents as pieces of a jigsaw puzzle. If we carefully have a look at the world map we can arrange different continents together. One such clear example is the South America and Africa. The complementary arrangement of the facing sides of these two continents look similar and obvious that they got separated from a single piece of land due to the tectonic forces.
• Glaciers : The widespread distribution of Permo-Carboniferous glacial sediments of Africa, South America, Antarctica, Australia, India, Madagascar and Arabia.  The continuity of these glaciers act as major evidence for the existence of the supercontinent Pangea. 

There are some more evidences for Continental Drift Theory and thus is acceptable by many organizations. But the acceptance for this theory hadn't been an easy task. During the period of 1930- 1950, different researchers like Vening-Meinesz, Umbgrove, Arthur Holmes and many others stated concepts that were close to the continental drift theory. Around 1947, a bunch of scientists found that there is floor of the seabed beneath the sediments of Atlantic Ocean which were chemically and physically different from the continental crust. This led to the conclusion that new ocean floor was being created and due to the magnetic variations across the ocean floor during world war two, scientists realized that "New magma from within the earth rises through the weak zones, where the polarity changes are observed in the magnetic patterns and erupts along the crest of the new ridges to create new oceanic crust. This new crust is magnetized by earth's magnetic field which undergoes occasional reversals. This new crust displaces the magnetized crust apart which is known as conveyor belt hypothesis". In later decades, the mid-oceanic rifts were discovered and the plate tectonics ,striping  became self-evident.

Drawbacks of Continental Drift Theory :

Wegener failed to explain why the drift started during the Mesozoic era(~250 million years ago) and what is the mechanism that could start such a massive continental movements. There are also debates that gravitational forces, forces due to earth's spin etc.. are too weak to move the continents, so what's the mystical force that drove the continents apart to their present locations? 

It has been 109 years since this theory was proposed by Wegener, yet it still has several researches going on and there are several interesting books related to the origin of continents and drift theory. There are also theories stating that present continents are still moving and might come together again after several million years.

I hope you found this article interesting :)