Our planet Earth was formed about 4.5 billion years ago. In the beginning, when the Earth was very different from what it is now. BISE Lahore Board Matric Date Sheet 2014 There was no air and no water bodies on the earth’s surface. It is generally recognized research scientists that the sun, planets and moons in our solar system were all formed from the solar nebula. We can determine the solar nebula as a huge mass of spiral cloud of dust and various types of hot gases.
Key components of the solar nebula were elements hydrogen and helium gases, and there were some other heavy elements too. Solar nebula began its reduction of about 4.6 billion years ago, BISE Lahore Board 10th Class Date Sheet 2014 probably due to the shock wave caused by a stellar explosion in a neighboring region. During compression, the temperature went down and he started to spin very quickly. As a result of cooling, and faster rotation is reduced, the external portion of the cloud has been separated from the main body. Solar system was formed from one of these separate rings of a gas cloud. Ring or disk further reduced and a dense cloud of warmed center to form the sun, whereas the outer part of the ring grouped together under the influence of gravity to become protoplanets. One of these clusters gases created planet Earth. This ball full of hot gases was by now cooled so that all the gases were in it condenses to a liquid or lava. During the period, with a further decrease in temperature, the lava hardens and led to the formation of Earth’s crust. BISE Lahore Board 9th Class Date Sheet 2014 During solidification, the liquid heavy metal such as iron, descended from the center due to the high density forming the core of the earth. The remainder of lava formed the Earth’s layer, which lies just below the crust.
Due to the cooling of the Earth, a large amount of steam escaped from its crust. As a result, volcanic eruptions, BISE Gujranwala Board Matric Date Sheet 2014 significant amounts of steam and different kinds of gas were also produced. Geologists believe that a good amount of water on Earth has been imported during her encounters with several comets that contained ice. When the temperature of the Earth was very high, all the water remains in the vapor state and surrounded the Earth’s surface. Then, when the earth’s temperature dropped, all the steam condenses to form clouds. BISE Gujranwala Board 10th Class Date Sheet 2014 The resulting rainwater had accumulated in the crater formed on the surface of the Earth by the impact of comets smashing. This led to the formation of the oceans.
At an early stage, the Earth’s atmosphere is composed of hydrogen and helium gases. But, as the Earth’s gravity was not so strong that she could not hold on to these light gases, and they were lost in space. Later, BISE Gujranwala Board 9th Class Date Sheet 2014 the effect of collisions with comets enriched the earth with water , as well as many other important gases such as carbon dioxide, methane , nitrogen, ammonia and other gases discharged from volcanic eruptions and collisions with comets also contributed to the formation of a new atmosphere above the Earth . Free oxygen was not available in the new environment, it was either related or some other hydrogen elements. The ozone layer is absent in the newly formed atmosphere. As a result, the earth’s surface has been exposed to ultraviolet radiation. BISE Multan Board Matric Date Sheet 2014 A significant amount of free oxygen in the atmosphere was detected only after a life form come to earth when photosynthesis process oxygen is supplied to the atmosphere.
According to the theory of geology, the current continents were formed due to fragmentation of the huge, single land mass. The earth’s crust consists of several large sheets of solid rock floating on the liquid mantle. Molten rock from the Earth’s mantle is in constant motion due to convection heat that occurs deep inside her. Owing to this inward movement, some of the plates constantly slide along the edges (most) relative to the other. BISE Multan Board 10th Class Date Sheet 2014 This is kind of continuous motion of one plate separate from each other. Shards of sushi and then walked away from the other and caused the division of the world. It is believed that the mountains were formed when one plate crustal pushed him from the other and as a result of pressure thrust part of land up.
All information about how the Earth was formed in this paper is based on various studies conducted by geologists, cosmologists, etc. BISE Multan Board 9th Class Date Sheet 2014 Changes that we discussed here took place on planet Earth gradually over several million years. Geological features of the Earth provided suitable conditions for the evolution of life on the planet, which appeared in the course of billions of years of education. Nevertheless, the human species came into existence much later.
