How was the earth created?
The Earth, at the beginning, was very different from what it
is now. It did not have any atmosphere or water bodies. The common belief of
scientists is that our planet earth was formed some 4.5 billion years ago. The sun,
the planets and their satellites in our solar system were all formed due to the
contraction of solar nebula. Solar nebula, from which our solar system is said
to have formed, was a huge mass of spiral cloud made up of dust particles and
various types of hot gases. The constituent elements of the solar nebula were
mainly hydrogen and helium and some other heavier elements. Solar nebula began
its contraction about 4.6 billion years ago. During the contraction process,
its temperature came down and it began to rotate very fast. As a result of
cooling, shrinking and rapid rotation, the outer part of the cloud got detached
from the main body in the form of rings.
How was the physical structure of the Earth formed?
Each of the detached rings cooled and shrank further. Then, gradually the separated rings clustered together to form a globe. This globe or ball of hot gases was by now, cooled so much that all the gases in it were condensed to liquid form or lava. Over a period of time, with further decrease in temperature, the lava solidified to form the crust of the Earth. During the process of solidification, the heavy metals like iron, in their liquid form, descended to the center due to high density, forming the core. The remaining separated lava formed the mantle, which lies just below the crust. In this way, the layered structure of Earth was formed.
How were the oceans of the Earth formed?
Due to the cooling of earth, large amounts of steam escaped from its crust. As a result of the eruptions of volcanoes, substantial amounts of steam and various types of gases were also released. Geologists believe that a good amount of water was imported to the Earth during its collisions with several comets that contained ice. When the temperature on the Earth was very high, all the water remained in vaporous form above the atmosphere. Then, as the temperature on Earth decreased, all the steam condensed to form clouds. The resulted rainwater got accumulated in the craters formed on the surface by the impact of smashing of comets. This led to the formation of the oceans.
How was the atmosphere of the Earth formed?
The impact of collisions with comets enriched the Earth with water as well as many other essential gases like carbon dioxide, methane, nitrogen ammonia, etc. The gases discharged from volcanic eruptions and collisions with comets led to the formation of the new atmosphere over the Earth. Free oxygen was not available in the new atmosphere; it was either bound by hydrogen or some other elements. The ozone layer was absent in the newly formed atmosphere. As a result of which, the Earth's surface was exposed to ultraviolet radiation.
How were the continents of the Earth formed?
According to theories of geology, the present-day continents were formed due to fragmentation of a huge, single mass of land. The broken pieces of land masses then drifted away from each other. The Earth's crust comprises a number of large plates of solid rock floating on the liquid mantle. The molten rock of the mantle is in constant motion due to convection of heat that occurs deep inside it. Due to this internal motion, some of the plates are constantly sliding at the edges (more commonly) in relation to others. This kind of movement detached one plate from another and caused the drifting of the continents. It is believed that the mountains were formed when one plate of the crust pushed the other, and the resultant pressure thrust a part of the land upwards.
All the changes that contributed to the creation of the Earth, as we know it today, happened very gradually over a period of a few million years. These geological features of the Earth made it suitable for evolution of life on the planet.