Geological periods in chronological order. Geological history of the Earth

The history of planet Earth already totals about 7 billion years. During this time, our common house has undergone significant changes, which was the result of changing periods. Geological periods in chronological order reveal the entire history of the planet from its very appearance to the present day.

Geological chronology

The history of the Earth, represented in the form of aeons, groups, periods and epochs is a certain grouped chronology. At the first international congresses of geology, a special chronological scale was developed that represented the periodization of the Earth. Later this scale was supplemented with new information and changed, as a result, now it reflects all the geological periods in chronological order.

The largest subdivisions in this scale are eonotimes, eras and periods.

Earth formation

Geological periods of the Earth in chronological order begin their history precisely with the formation of the planet. Scientists came to the conclusion that the Earth was formed about 4.5 billion years ago. The process of its formation was very long and, perhaps, started 7 billion years ago from small cosmic particles. Over time, the gravitational force grew, along with it the speed of bodies falling on the emerging planet increased. The kinetic energy was transformed into heat, as a result of which the Earth was gradually heated.

The core of the Earth, according to scientists, was formed over several hundred million years, after which the gradual cooling of the planet began. At present, 30% of the Earth's mass is contained in the molten core. The development of other shells of the planet, according to scientists, has not been completed so far.

Precambrian aeon

In the geochronology of the Earth, the first eon is called the Precambrian. It covers the time 4.5 billion - 600 million years ago. That is, the lion's share of the history of the planet is covered first. However, this eon is divided into three more - Katarchey, Archaean, Proterozoic. And often the first of them stands out as an independent eon.

At this time, the formation of the earth's crust, land and water. All this took place during active volcanic activity throughout almost the entire aeon. Shields of all continents were formed in the Precambrian, but traces of life are very rare.

Katarchean Eon

The beginning of the history of the Earth - half a billion years of its existence in science is called Katarche. The upper boundary of this eon is at the level of 4 billion years ago.

Popular literature draws us Katarchei as a time of active volcanic and geothermal changes on the surface of the Earth. However, in reality this is not true.

The Katarchean eon is a time when volcanic activity was not manifested, and the surface of the Earth was a cold inhospitable desert. Although quite often there were earthquakes that smoothed the landscape. The surface looked like a dark gray primary substance covered with a layer of regolith. The day at that time was only 6 hours.

Archean eon

The second major eon of the four in the history of the Earth lasted about 1.5 billion years - 4-2.5 billion years ago. Then the Earth did not yet have an atmosphere, so there was still no life, however, the appearance of bacteria occurs in this eon, because of the absence of oxygen, they were anaerobic. As a result of their activities today we have deposits of natural resources, such as iron, graphite, sulfur and nickel. The history of the term "archaea" originates in 1872, when the famous American scientist J. Dan proposed it. The Archean eon, unlike the previous one, is characterized by high volcanic activity and erosion.

The Proterozoic Eon

If we consider the geological periods in chronological order, the next billion years was taken by the Proterozoic. This period is also characterized by high volcanic activity and sedimentation, and erosion continues over large areas.

There is a formation of the so-called. Mountains of Baikal folding. At present they are small hills on the plains. The rocks of this aeon are very rich in mica, non-ferrous metal ores and iron.

It should be noted that in the Proterozoic period the first living creatures appeared - the simplest microorganisms, algae and fungi. And by the end of the aeon there are worms, marine invertebrates, mollusks.

Phanerozoic eon

All geological periods in chronological order can be divided into two types - explicit and hidden. The Phanerozoic refers to the obvious. At this time there is a large number of living organisms with mineral skeletons. The epoch that preceded the Phanerozoic was called hidden because its traces were practically not found because of the absence of mineral skeletons.

The last about 600 million years of the history of our planet are called the Phanerozoic eon. The most significant events of this eon are the Cambrian explosion, which occurred about 540 million years ago and the five largest extinctions in the history of the planet.

The eras of the Precambrian aeon

During the Katarchean and the Archean there were no universally recognized eras and periods, so we will skip their consideration.

The proterozoic consists of three great eras:

Paleoproterozoic - i.e., ancient, including siderium, riassic period, orosiria and stateria. By the end of this era, the oxygen concentration in the atmosphere has reached a modern level.

Mesoproterozoic - medium. It consists of three periods - calima, ectazias and steny. In this era, algae and bacteria have reached their peak.

Neoproterozoic - a new one, consisting of a line of thorns, cryogenic and Ediacar. At this time, the first supercontinent Rodinia is being formed, but then the plates again parted. The coldest glacial period passed in an era called mesoproterozoic, during which most of the planet froze.

Era of the Phanerozoic Eon

This aeon consists of three great eras, which differ sharply from each other:

Paleozoic, or the era of ancient life. It started about 600 million years ago and ended 230 million years ago. Paleozoic consists of 7 periods:

1. Cambrian (on the Earth a moderate climate is formed, the landscape is low-lying, during this period all the modern types of animals originate).
2. Ordovician (the climate on the whole planet is warm enough, even in Antarctica, while the land is considerably submerged.) The appearance of the first fish occurs.
3. The Silurian period (the formation of large intracontinental seas is taking place, while the lowlands are becoming more arid due to the land rising, the development of fish continues.) The Silurian period is marked by the appearance of the first insects).
4. Devon (the appearance of the first amphibians and forests).
5. Lower Carboniferous (dominance of ferns, distribution of sharks).
6. Upper and middle Carboniferous (appearance of the first reptiles).
7. Perm (most ancient animals die out).

Mesozoic, or the time of reptiles. The geological history of the Mesozoic era consists of three periods:

1. Trias (seed ferns die out, gymnosperms dominate, first dinosaurs and mammals appear).
2. Jura (part of Europe and the western part of America is covered with shallow seas, the appearance of the first toothed birds).
3. Chalk (the appearance of maple and oak forests, the highest development and extinction of dinosaurs and toothed birds).

Cenozoic, or the time of mammals. It consists of two periods:

1. Tertiary. At the beginning of the period predators and ungulates reach their dawn, the climate is warm. There is a maximum spread of forests, the oldest mammals are dying out. Approximately 25 million years ago there appeared anthropoid apes, and in the Pliocene epoch a man appears.
2. Quaternary. Pleistocene - large mammals are dying out, human society is born, 4 glacial periods occur, many species of plants die out. The modern era is the end of the last glacial period, the climate gradually acquires the present species. The rule of man on the whole planet.

The geological history of our planet has a long and controversial development. In this process there was a place for several extinctions of living organisms, glacial periods were repeated, periods of high volcanic activity were observed, there were eras of the primacy of different organisms: from bacteria to humans. The history of the Earth began about 7 billion years ago, it was formed about 4.5 billion years ago and just less than a million years ago a person ceased to have competitors in all wildlife.