The formation of the earth is still a mystery today, even with all the advancements in science. Scientists have yet to come up with a definitive answer to how the earth was formed but there are two main theories out there in terms of formation of the planets. One relates to planets such as earth while the other explains the formation of bigger plants in the solar system.
The Core Accretion Theory
This theory explains the formation of planets such as earth with terrestrials. The theory goes back 4.6 billion years and claims that at that point in time, the solar system was nothing but gas and a cloud of dust. With the inclusion of gravity to the solar nebula, materials in it began to spin eventually forming the sun.
With the formation of the sun, small particles and materials began to clump and were bonded together with the help of gravity. The sun helped by taking way lighter elements like helium and hydrogen which left heavy material that replicated rocks. However, this was only the case with planets close to the sun. For those further away, the elements remained which allowed them to be bigger.
In terms of the earth, the core formed first, with the elements binding together forming a rocky surface. While the materials that were dense sinking to the center and the lighter materials forming the crust. This was the time when the magnetic field of the earth was formed.
When the earth was formed, some scientists believe that a large body collided with it which led to a chunk of the mantle being dislodged into space. While asteroid and comets are not as common today, it is predicted that they were common back then when the solar system was young. As far as the formation of mountains and volcanoes goes, those were formed through friction and collision resulting in the release of gases in the atmosphere.
While this theory works for planets such as the earth, it doesn’t really fit well with planets that are more like gas giants. For those planets, we have a second theory known as disk instability model. However, we will not get into those theories since it is hard for it to explain how the earth was formed. Since earth, has living creatures on it, the core accretion theory is more likely how it was formed.