When did the earth originate?

The systematic scientific research on the origin and evolution of the earth began in the middle of the eighteenth century, and many theories have been put forward so far. The popular view now is that the earth, as a planet, originated from the primitive solar nebula 4.6 billion years ago. Like other planets, it has experienced some similar physical evolution processes such as accretion and collision. At the beginning of embryo formation, the temperature was low and there was no layered structure. It is only because of the bombardment, radioactive decay and gravitational contraction of the original earth that the temperature of the earth gradually rises. With the increase of temperature, the materials in the earth become more and more plastic, and local melting occurs. At this time, under the action of gravity, material differentiation begins, heavier materials outside the earth gradually sink, lighter materials inside the earth gradually rise, and some heavy elements (such as liquid iron) sink to the center of the earth, forming a dense core (seismic wave observation shows that the outer core of the earth is liquid). The convection of matter was accompanied by large-scale chemical separation, and finally the earth gradually formed the present crust, mantle and core.

In the early stage of the earth's evolution, the primitive atmosphere completely escaped. With the recombination and differentiation of matter, various gases in the earth rose to the surface through volcanic eruption to become the second generation atmosphere, and later, due to the photosynthesis of green plants, it further developed into a modern atmosphere. On the other hand, the internal temperature of the earth rises, which makes the internal crystal water vaporize. With the gradual decrease of surface temperature, gaseous water condenses and falls to the ground to form hydrosphere. About three or four billion years ago, single-celled organisms began to appear on the earth, and then gradually evolved into various organisms until advanced organisms like humans formed a biosphere.

Detailed division of Cenozoic era (unit: million years)

Paleogene Paleocene 65-53

Eocene 53-36.5

Oligocene 36.5-23

Miocene 23-5.3

Pliocene 5.3- 1.8

Quaternary Pleistocene 1.8―0.0 1

Holocene 0.0 1- modern

The stage of crustal development on the earth

1

Archaean-Proterozoic

Weak crustal activity; Marine sediments are absolutely dominant; Some ancient plots were formed at the end of the period.

2

Sinian Period

Marine sediments are dominant; The ancient platform was formed.

three

Cambrian-Ordovician-Silurian

Caledonian movement and marine deposits still dominate; Finally, the Caledonian geosyncline folds and swells.

four

Devonian-Carboniferous-Permian

Hercynian movement, relative expansion of land; At the end of the period, many geosynclines rose, the northern continent united, and the southern continent began to disintegrate.

five

Triassic-Jurassic-Cretaceous

Yanshan movement, the disintegration of the southern continent and the extensive activities of the northern continent; The area around the Pacific geosyncline rises into mountains.

six

Tertiary Paleocene, Eocene, Oligocene, Miocene and Pliocene.

Himalayan orogeny, paleoplatform and paleofold are widespread; The ancient Mediterranean belt and the outer belt around the Pacific Ocean rise to mountains.

seven

Quaternary Pleistocene, Holocene-Neotectonic period

The difference fluctuates significantly and glaciers are widely distributed.

The development stage of the animal kingdom on earth

1 Archaean

The lowest primitive creatures came into being.

Cambrian-Ordovician-Silurian

The era of marine invertebrates

3 Devonian

Fish times

4 Carboniferous-Permian

Amphibian age

5 Triassic-Jurassic-Cretaceous

Reptile age

6 tertiary industry

Mammalian age

7 Quaternary

Human age

The development stage of the plant kingdom on the earth

1 Archaean

The lowest primitive creatures came into being.

2 Sinian-Cambrian-Early Ordovician

Age of seaweed

3 Early Ordovician-Carboniferous-Early Permian

Age of terrestrial spore plants

4 Early Permian-Triassic-Jurassic-Middle Cretaceous

Age of gymnosperms

5 Middle Cretaceous-Tertiary-Quaternary

Angiosperm age

The epidemic period of some creatures on the earth.

1 Earth astronomical period

2 Archaean Pre-Sinian

Seaweed, sponge

Ancient 3 yuan: Sinian

Seaweed, sponge

Paleozoic: CAMBRIAN

Keywords seaweed, sponge, brachiopod, marine forest, trilobite,

Ordovician: algae, sponges, corals, brachiopods, sea lilies, sea buds, starfish, trilobites,

Silurian algae, sponges, corals, brachiopods, sea lilies, sea buds, starfish, trilobites, nautilus,

Devonian: algae, sponges, corals, brachiopods, sea lilies, sea buds, starfish, trilobites, fish scales, nautilus,

Carboniferous: algae, sponges, corals, brachiopods, sea lilies, sea buds, starfish, trilobites, sand fish, fish scales, nautilus,

Permian: algae, sponges, corals, sea lilies, trilobites, sand fish, fish scales, nautilus.

5 Mesozoic

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