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Did the earth always look as it does today?

                             

No, since its origin about 4.8 billion years ago, our planet has undergone a lot of changes. The initial ball of fire cooled down and the surface slowly turned solid, today we know that the Earth’s crust is divided into several plates, which move continuously. Entire continents have been displaced and mountains, islands, and new seas have been formed or have disappeared. Even the flora and fauna have evolved over time. Many species have become extinct and new ones have been discovered. This development of the Earth over billions of years is known as the history of Earth.

                         

How many plates does the Earth’s crust have?

The relatively sold Earth’s crust-and a part of the layer that lies below it-is divided into seven large and more than ten smaller plates. These plates float over the hot, viscous layer, which is constantly in motion- like boiling soup. These flushes of heat in the Earth’s interior are known as ‘convection cells’. At places where the convection currents push the rocks upwards, the crust often breaks and gives rise to a new crust. For example, the mid-ocean ridges in Atlantic and Pacific oceans.

 


Who discovered the continental drift?

This discovery is credited to the German geologist Alfred Wegener. He not only discovered that the coastline of South America fits very well against that of Africa but also showed that the fossils in both the coastal regions are similar. He also proposed another idea: about 300 million years ago there must have been a single, continuous landmass that somehow broke up and gave rise to several parts- the tectonic plates. The continents on these plates drifted away from one another and then rejoined the way they are today. Thus, landmasses were displaced, and their position is changing even today. The tectonic plates are still moving at a speed of around 6 cm per year.

                         

How are mountains formed?

 Mountains are formed in two ways. When the tectonic plates move, they collide against each other. When the heavy oceanic part of the plate collides with the continental part, it submerges below it. The Andes, for instance, were formed in this way. The other way is when two continents collide with each other; the plates bend at the point of contact and fold up steeply. The Himalayas and the Alps were formed in this way around 35 million years ago and are counted among the ‘young’ mountains of the world. Old mountains, such as the Black Forest or the Harz mountains are lower ranges because their peaks have been worn down by rain, ice, and wind over time. 

 


How are new seas formed?

Seas arise at places where the Earth’s crust cracks open due to expansion. Around 200 million years ago the Atlantic was formed in this way. Today in East Africa, a crack from Malawi to Ethiopia has formed as a result of the eruption of a volcano. If the soil sinks further, water from the oceans will enter the region to give rise to a water body. This has already happened in the case of the Red Sea, the continuation of the East African rift system. If the plate continues to expand, then at some point of the time it breaks completely giving rise to a long mid-ocean volcanic ridge.

                      

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