The earth (from the sun) is the inner planet with the largest mass and density, and it is also the only known planet with geological activities and life [89]. Its liquid hydrosphere is unique among terrestrial planets and the only planet with plate activity. The earth's atmosphere is completely different from other planets, and it has been changed by existing organisms into an atmosphere of 2 1% free oxygen.

It has a natural satellite-the moon, which is the only large satellite in the solar system owned by a terrestrial planet.

7 1% of the earth's surface is covered with water, which is called ocean or lake or river, and the rest are continents and islands composed of land plates, with rivers, lakes and other water sources distributed on the surface. There is ice in the Antarctic ice sheet and the North Pole.

The main body includes lithosphere, mantle, molten metal outer core and solid metal inner core. There is a geomagnetic field generated by the outer core. Surrounded by gas, it is called the atmosphere, and its main components are nitrogen, oxygen, carbon dioxide and argon.

Extended data:

Birth and evolution

4.6 billion years ago, the earth was born. The evolution of the earth can be roughly divided into three stages.

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 to 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 all over the world and widely preserved, so they can be observed and studied, which is the main research object of geological science, and the basic theory and knowledge of geology have been established.

References:

Baidu Encyclopedia-Earth