The first stage is the formation of the earth's sphere, and its time limit is about 4600 ~ 4200ma ago. The earth when it was born 4.6 billion years ago is very different from the earth in 2 1 century. According to scientists' inference, at the beginning of the earth's formation, it was a hot ball composed of hot liquid substances (mainly magma). With the passage of time, the temperature of the earth's surface has been decreasing, and the solid core has gradually formed. Dense matter moves toward the center of the earth, and less dense matter (rocks, etc.). ) floats on the surface of the earth, thus forming the earth whose surface is mainly composed of rocks.
The second stage is Archean and Proterozoic. Its time limit is 4200-543Ma. The earth constantly releases energy, and the steam, carbon dioxide and other gases released by the continuous eruption of high-temperature magma constitute a very thin early atmosphere-primitive atmosphere. With the increase of water vapor in the primitive atmosphere, more and more water vapor condenses into small water droplets, and then gathers into rainwater and falls to the surface. In this way, the primitive ocean was formed.
The third stage is Phanerozoic, with a time limit of 543Ma. Phanerozoic lasted relatively short, but during this period, biology flourished, geological evolution was very rapid, and geological processes were rich and colorful. In addition, geological bodies are distributed all over the world and widely preserved, which makes it possible to observe and study them well, become the main research object of geological science and lay the basic theory and knowledge of geology.
Human scientists have been able to reconstruct information about the earth's past. The material in the solar system originated 4,567.2 million 600,000 years ago, about 4,540 million years ago (the error is about 65,438+0%), and the earth and other planets in the solar system began to see the earth in the solar nebula, which is a universe formed by gas and dust left over from the formation of the sun? Disc-shaped-internally formed. Through the process of accretion, the earth has been completely formed after 1 to 20 million years. From the initial melting state, the outer layer of the earth cooled and solidified into a solid crust, and water began to accumulate in the atmosphere. The moon formed late, about 4.53 billion years ago. A celestial body (usually called Theia) with a volume equivalent to Mars and a mass of about 65,438+00% of the Earth had a fatal collision with the Earth. Part of the mass of this celestial body is combined with the earth, part of it splashes into space, and enough matter enters orbit to form the moon. The released gas and volcanic activity produce primitive atmosphere, and the water carried by asteroids, larger protoplanets, comets and celestial bodies outside Neptune increases the water content of the earth, and condensed water produces oceans. The brightness of the newly formed sun is only 70% of that of the sun, but there is evidence that the early ocean is still liquid, which is called the weak young sun paradox. The combination of greenhouse effect and higher solar activity increases the temperature of the earth's surface and prevents the condensation of the ocean.
There are two main theories of mainland growth: stable growth in modern times and rapid growth in early history. Studies show that the second theory is more likely, that is, the early crust grew rapidly, followed by long-term stable continental regions. In the last few hundred million years on the time scale, the earth's surface constantly reshaped itself, and the mainland constantly formed and split. Occasionally, a supercontinent will be formed in the continent where the surface moves. About 750 million years ago, Rodinia, the earliest known supercontinent, began to split, and later it merged into Pangea from 600 million to 540 million years ago, and finally it began to split 65.438+800 million years ago.