The earth was formed about 4.5 billion years ago. During the existence it went through a set of stages of development, turned from the heated sphere into the only planet known to mankind inhabited by living organisms.
Instruction
1. Emergence of the earth is directly connected with formation of the Solar system. Certainly, all theories about emergence of Earth are only hypotheses which are constantly reconsidered on the basis of new data. At the moment the main is considered a hypothesis of formation of planets of the Solar system including Earth, from the gas-and-dust cloud rotating around the Sun.
2. About 4.6 billion years ago thanks to gravitational collapse from a part of a cloud of interstellar dust there was the Sun which became the center of a new planetary system. Around the Sun the disk was formed of substance of a gas-and-dust cloud. This disk with high speed rotated around the Sun, particles in it constantly interacted, consolidations in a disk made a start and connected, created, thus, it gradually broke up to separate parts, so-called planetezimal.
3. The largest planetezimal began to attract other clots of matter and were condensed under the influence of gravitational forces. The solar system during the formation had an appearance, other than present, it included about 100 protoplanets, but the system was much less by the sizes, than now. Protoplanets faced, forming the planets known to us now including Earth, in the same time also satellites of planets, for example the Moon were formed.
4. Originally Earth had very big temperature, that is substance on it was in the melted state and violently mixed up, more dense metals fell down, forming a metal kernel, silicates rose up, forming a cloak. The metal kernel made possible emergence in the planet of magnetic field.
5. Gradually the planet was cooled, the volcanic activity decreased, in the atmosphere a large amount of water collected. Cooling of the planet led to formation of earth crust. About 3.8 billion years ago on Earth there were first living organisms, the biosphere which radically influenced further development of the planet was formed.