The age of Earth contains about 7 billion years. During this time the planet changed, sometimes practically to unrecognizability. Significant changes in Earth are called the geological periods. With their help it is possible to consider the history of the planet since the birth so far.
What is geological chronology
The chronology is the story of the planet divided into the periods, eras, groups and ions. The geological chronology was developed rather recently. The chronology was presented on one of the first international congresses of geology. The chronological scale showed division of history of the earth into the periods. Over time the geological chronology changed and complemented. Now the chronology is considered full because in it all stages of development of Earth found reflection in a consecutive order.
As the mother Earth was formed
Formation of the planet - the very first stage in geological chronology. Scientists managed to prove that Earth was finally created 4.5 billion years ago, but its true age is much more high. Formation of the planet - long process. Scientists consider that on it about 3 billion more years left.
The planet was formed of small space particles. Gravity increased, the speed of space bodies which were attracted by future planet gradually increased. Energy created heat, gradually heating the planet.
The first formed Earth kernel. Scientists assure that it was created not less than several hundred millions of years. Because of slow cooling of a kernel, other mass of the planet was formed by less dense. A kernel of the planet are about 30% of all mass of Earth. The science considers that other covers still were not created up to the end.
The Precambrian became the first eon in geological chronology of Earth. It is divided into three groups: Hadean, Archean, Proterozoic. Scientists quite often allocate the Hadean in a separate eon.
The Precambrian era is time before emergence of life. There was a formation of earth crust, and then division into the land and waters. Earth crust could be formed, thanks to volcanic activity. Besides, at the end of the Precambrian boards of those continents which exist now were formed.
The Hadean is the beginning of history of Earth. The upper bound of this ion - 4 billion years ago. In literature the Hadean Eon is described as an era of the changes of the planet which happened thanks to volcanic changes of a surface and landscape of Earth, but it is not absolutely right.
- it is impossible to call the Hadean time of manifestation of volcanic activity. The surface of the planet was the cold place reminding the desert. From time to time earthquakes shook the planet. They did a landscape softer and smooth. The surface was dark gray and regolitovy, there was a slow stratification of soil.
Day during the Hadean Eon did not exceed six hours.
Duration of this eon was about 1.5 billion years. The atmosphere at the planet so far was also not planned. Respectively, life on Earth was not observed too. However, then there was its origin. The first bacteria appeared during the Archean Eon.
If not activity of these bacteria, now on Earth there would be no many natural minerals: gland, sulfurs, graphite and many others.
Erosion and strong volcanic activity are typical for the Archean.
During the Proterozoic the erosion became more severe. At the same time, volcanic activity formation of precipitation did not decrease, began.
During the Proterozoic Eon, mountains which resemble hills more now were formed. Mountains which were formed in this period of time are famous for minerals and ore of different breeds of metals.
Also the Proterozoic was time when the first living beings on Earth appeared: the simplest microorganisms and mushrooms. On them evolution within an eon did not end. By the end of an era invertebrates, worms and mollusks began to appear.
The Phanerozoic is interesting that during this era the majority of living organisms with a mineral skeleton appeared. Cambrian explosion which led to one of the largest extinctions of life which happened on the globe became the most significant event of a fanerozoysky era.
Era of a Precambrian eon
In katarkheysky and archaean eon there are no conventional periods, and therefore scientists consider only an era of the Proterozoic Eon consisting of three Ayr.
This era includes four more periods: Siderian, Rhyacian Period, oroziriya and stateriya. When the Paleoproterozoic Era came to an end, oxygen concentration in the atmosphere of Earth became close to what we see in the present.
The Mesoproterozoic Era became time of development of bacteria and seaweed. Scientists divide this era into three periods: kalimy, ektazy and steny.
This era became the latest to a Precambrian eon. During the Neoproterozoic Era there was a formation of the continent Rodiniya which does not exist now any more because plates of a landscape dispersed again.
The Neoproterozoic Era - time of the coldest Ice Age in the history of Earth. During it almost all planet froze, having destroyed many living organisms.
Era of the Phanerozoic Eon
The Phanerozoic Eon consists of three eras: Paleozoic era, Mesozoic and Cenozoic.
The Paleozoic is considered an era of ancient life. This era consists of eight periods:
- During the period, modern animal species as the landscape was already created arose, and the climate became temperate.
- The climate during this period became warmer in comparison with the Cambrian. The land plunges into water stronger, and the first fishes appear later.
- This period is characteristic creation of the large seas. The land rises, and the climate becomes more droughty. Fishes continue the development and also the first insects appear.
- During this period the woods begin to be formed, the climate becomes temperate. On Earth, Amphibia appear.
- Lower carbon fabrics. There is a distribution of sharks. Pteridophytes of a plant are most widespread on the planet.
- Average carbon fabrics. This period became the beginning of life of reptiles.
- Top carbon fabrics. Reptiles continue to develop and inhabit Earth.
- Universal extinction of ancient animals.
Mesozoic era is known as time of reptiles. This era consists of three periods:
- There is an extinction of seed ferns. Their place is taken by gymnospermous. All of them extend on a planet landscape stronger. Later there is an appearance of mammals and dinosaurs.
- There are first zubaty birds. In Europe, and then and in America the shallow seas are formed.
- There is the maximum development, and then extinction of dinosaurs and zubaty birds. Gymnospermous plants lose domination. There are oak and maple woods.
Cainozoic era - time of mammals. In it there were only two periods:
- The climate becomes warm. Hoofed animals and predators develop more and more promptly. The woods extend more and stronger, and the most ancient mammals slowly die out. Instead of them anthropoids begin to appear.
- There is an extinction of large mammals, and human society only begins origin. There are four more Ice Ages because of which the majority of plant species dies out. After the last Ice Age the climate becomes on modern. The person takes the predominating position, suppressing other life forms on Earth.
It is possible to call the geological history of our planet contradictory. Organisms developed in the millennia then completely to disappear because of climate changes. They were succeeded by new life forms, but history repeated. And only the mankind managed to be late long enough.