How old is the earth?

The earth was formed about 4.5 billion years ago. This rocky planet was originally just dust floating in space, which originated from the big bang at the end of the life of a huge ancient star.

Since its formation, the earth can also be divided into five generations: Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic. Some generations are further divided into several "periods", for example, Paleozoic is divided into CAMBRIAN, Ordovician, SILURIAN, Devonian, Carboniferous and Permian from far to near; Mesozoic is divided into Triassic, Jurassic and Cretaceous; Cenozoic is divided into tertiary and quaternary. This is the roughest division of the earth's historical period, which we call "geological age". People in different geological ages have different characteristics.

The primitive lithosphere, hydrosphere and atmosphere were formed on the earth's surface 2.4 billion years ago. But at that time, the crust was very unstable, volcanic activity was frequent, magma was everywhere, the ocean was vast, and the land was all bare mountains. This is an important era of iron ore formation, and the lowest primitive life began to appear.

From 2.4 billion years ago to Proterozoic 600 million years ago. At this time, most of the earth is still covered by oceans. Later, a large area of land appeared on the earth. "Proterozoic" refers to the primitive era, when algae and marine invertebrates appeared.

600-250 million years ago was Paleozoic. "Paleozoic" refers to the era of ancient life. At this time, thousands of animals appeared in the ocean, and marine invertebrates flourished unprecedentedly. Later, fish-shaped animals appeared, and fish multiplied in large numbers. A fish crawling on its fins appeared and landed on land, becoming the ancestor of terrestrial vertebrates. Amphibians also appeared. Ferns have appeared on the land in the northern hemisphere, some as high as 30 meters. These tall and dense forests later became big coalfields.

Mesozoic, from 250 million years ago to 700 million years ago, lasted about 65438+800 million years. This is the era of reptiles. Dinosaurs once ruled for a while, and then primitive mammals and birds appeared. Ferns are decreasing and being replaced by gymnosperms. The lush plants and huge animals in Mesozoic later turned into many huge coalfields and oil fields. Many metal deposits were also formed in Mesozoic.

Cenozoic is the latest stage in the history of the earth, with the shortest time, only about 70 million years. At this time, the face of the earth has been basically similar to today's situation. A new generation of angiosperms has developed greatly, and all kinds of herbivorous and carnivorous mammals have flourished unprecedentedly. The great development of nature creatures finally led to the emergence of human beings, and the ancient apes gradually evolved into modern people. It is generally believed that human beings appeared in the Quaternary, about 2.4 million years ago.

The earth where human beings live has evolved step by step to the present and gradually formed today's face.

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