The history of planet Earth is already about 7 billion years old. 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 timeline
The history of the Earth, presented in the form of eons, 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. Subsequently, this scale was replenished with new information and changed, as a result, now all geological periods are reflected in it in chronological order.
The largest units on this scale are eonotems, eras, and periods.
Earth Formation
The geological periods of the Earth in chronological order begin their history precisely with the formation of the planet. Scientists have concluded that the Earth formed about 4.5 billion years ago. The process of its formation was very long and, possibly, began even 7 billion years ago from small cosmic particles. Over time, the force of gravity grew, along with it increased the speed of bodies falling on an emerging planet. Kinetic energy was transformed into heat, resulting in a gradual heating of the Earth.
The core of the Earth, according to scientists, was formed over several hundred million years, after which the gradual cooling of the planet began. Currently, the molten core contains 30% of the mass of the Earth. The development of other shells of the planet, according to scientists, has not been completed so far.
Precambrian Aeon
In geochronology of the Earth, the first aeon is called Precambrian. It covers a time of 4.5 billion - 600 million years ago. That is, the lion's share of the history of the planet is covered first. However, this aeon is divided into three more - cathars, archaea, and Proterozoic. Moreover, 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 happened during active volcanic activity throughout almost the entire eon. Shields of all continents were formed in Precambrian, but traces of life are very rare.
Catharic eon
The beginning of the history of the Earth - half a billion years of its existence in science is called catarchea. The upper boundary of this aeon is at around 4 billion years ago.
Popular literature portrays catarchees as a time of active volcanic and geothermal changes on the surface of the Earth. However, in reality this is not true.
The Catharheon aeon is a time when volcanic activity did not appear, and the Earth's surface was a cold inhospitable desert. Although quite often earthquakes occurred 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 main eon of 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, therefore there was no life yet, however bacteria appeared in this aeon, due to the lack 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 it was proposed by the famous American scientist J. Dan. Archean aeon, unlike the previous one, is characterized by high volcanic activity and erosion.
Proterozoic Aeon
If we consider the geological periods in chronological order, the next billion years took Proterozoic. This period is also characterized by high volcanic activity and sedimentation, and erosion continues on vast areas.
The formation of the so-called. mountains of Baikal folding. Currently, 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 during the Proterozoic period the first living creatures appeared - the simplest microorganisms, algae and fungi. And by the end of the aeon, worms, marine invertebrates, mollusks appear.
Phanerozoic aeon
All geological periods in chronological order can be divided into two types - explicit and hidden. Phanerozoic is explicit. At this time, a large number of living organisms with mineral skeletons appear. The era preceding Phanerozoic was called hidden because practically no traces of it were found due to the absence of mineral skeletons.
The last about 600 million years of the history of our planet are called the Phanerozoic aeon. The most significant events of this aeon are the Cambrian explosion that occurred about 540 million years ago and the five largest extinctions in the history of the planet.
Era of the Precambrian Aeon
There were no universally recognized eras and periods during the catarchea and archaea, so we will skip their consideration.
Proterozoic consists of three large eras:
Paleoproterozoic - that is, ancient, including siderius, the Riasian period, orozirius and stateria. By the end of this era, atmospheric oxygen concentration has reached a modern level.
Mesoproterozoic - medium. It consists of three periods - potassium, ectasia and stenium. In this era, algae and bacteria have reached their greatest prosperity.
Neoproterozoic - a new one, consisting of tonia, cryogeny and ediacaria. At this time, the formation of the first supercontinent - Rodinia, occurs, but then the plates parted again. The coldest ice age took place in an era called mesoproterozoic, during which most of the planet froze.
Era of the Phanerozoic aeon
This aeon consists of three great eras, dramatically different from each other:
Paleozoic, or the era of ancient life. It began about 600 million years ago and ended 230 million years ago. The Paleozoic consists of 7 periods:
- Cambrian (a temperate climate is formed on Earth, the landscape is low, during this period all modern types of animals are born).
- Ordovician (the climate on the whole planet is quite warm, even in Antarctica, while the land is sinking significantly. The appearance of the first fish).
- Silurian period (the formation of large inland seas, with the lowlands becoming arid due to the rise of the land. The development of fish continues. The Silurian period is marked by the appearance of the first insects).
- Devon (the appearance of the first amphibians and forests).
- Lower Carboniferous (dominance of ferns, shark distribution).
- Upper and middle carbon (the appearance of the first reptiles).
- Perm (most ancient animals die out).
Mesozoic, or reptile time. The geological history of the Mesozoic era consists of three periods:
- Triassic (seed ferns die out, gymnosperms dominate, the first dinosaurs and mammals appear).
- Jura (part of Europe and the western part of America is covered with shallow seas, the appearance of the first toothed birds).
- Chalk (the appearance of maple and oak forests, the highest development and extinction of dinosaurs and toothed birds).
Cenozoic, or the time of mammals. Consists of two periods:
- Tertiary. At the beginning of the period, predators and ungulates reach their dawn, the climate is warm. The maximum distribution of forests takes place, the oldest mammals die out. Approximately 25 million years ago, apes appear , and in the Pliocene epoch man appears.
- Quaternary. Pleistocene - large mammals die out, human society is emerging, 4 ice ages occur, many species of plants die out. Modern era - the last ice age ends, gradually the climate takes on its current form. The primacy of man on the entire planet.
The geological history of our planet has a long and contradictory development. In this process, there was a place for several extinctions of living organisms, ice ages repeated, periods of high volcanic activity were observed, there were era of 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, man ceased to have competitors in all wildlife.