Category The Earth, Earth Science, Planet Earth

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.

The relatively solid 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 the Atlantic and Pacific oceans.

The word ‘atmosphere’ means a gaseous cover enveloping a planet. Without atmosphere life would not have been possible on the Earth: One-fifth of the atmosphere is oxygen and four-fifths is nitrogen. Like the Earth’s interior, the atmosphere too is made up of several layers. All animals and plants live in the lowermost layer of the atmosphere called the ‘troposphere’. All weather phenomena take place in the troposphere. Even aeroplanes fly in the outer edge of the troposphere. The stratosphere, the mesosphere, the ionosphere, and the exosphere lie above the troposphere. 

Gravity is the force of the Earth that attracts every object towards itself. From our perspective this force always acts downwards. For a long time people did not believe that the Earth is round because then the people ‘underneath’ the sphere would have actually fallen down. In 1687, a physicist, Isaac Newton, proved that the force of gravity always acts towards the centre of the Earth. On the Earth, the force of gravitation always acts ‘downwards’ irrespective of Eskimos in the Arctic region, people in Europe or inhabitants of Australia. 

About 3000 years ago people believed that the Earth was flat. But people wondered why ships disappeared at the horizon. Sailors too returned from journeys and were proof that ships did not fall off the edge of the Earth. The simplest explanation was: the Earth must be round. The final proof came in the year 1522 after the expedition of Ferdinand Magellan, who was the first to sail around the Earth.

Caves and mines go only up to 1-2 km inside the Earth. Even the deepest wells of the world, such as the one 12 km deep in the Russian Kola Peninsula or the 9-km-deep one in the Upper Palatinate, hardly scratch the Earth’s crust. One can ‘look’ deep inside the Earth in the aftermath of earthquakes or by creating nuclear explosions. The explosions generate sound or seismic waves. They also throw off rock particles. By measuring their intensity and timings, scientists discover the composition of the Earth’s interiors.