How was the Earth formed?

               Our Earth was born around 4.6 billion years ago. Like the Sun and other planets, it was also formed out of the clouds of dust and gases. However, before turning into present shape it was a fireball surrounded by an atmosphere of burning gases. At that time it revolved round the Sun in the form of a hot spherical body. Hundreds of years later, it gradually started moving away from the Sun while still revolving round it. As it moved farther and farther from the Sun, its temperature kept on decreasing. It started cooling off and its outer layer changed into a crust. With the hardening of this crust, cracks developed in it and molten material from inside started coming out. Over a period of millions of years, this molten material gave birth to mountains and valleys. 

          As time passed by, the thick layer of hot gases enveloping the Earth cooled off and turned into clouds. These clouds rained on the Earth for a long time. Rain-water accumulating in the low-lying areas of the Earth turned into the oceans. With the passage of time, there were upheavals due to which its surface was raised high or pressed down. This produced many volcanoes. Slowly it became calm and the seas and mountains took their definite shapes.

          Subsequently, around 570 million years ago, micro-organisms started developing on the Earth. In the first 345 million years, marine (aquatic) animals came into existence. As more time passed, the aquatic animals also underwent changes.

          In the next phase of evolution, the great reptiles – creatures crawling on the Earth – came into existence. And finally around a million years ago man was born through evolution.

          Today, Earth has all the favourable conditions required for the existence of has an atmosphere absolutely essential for the living beings.