It is believed that the Earth took 7 billion years to become what we know and see it today. Over the entire period of its existence, our planet has accumulated countless secrets, especially about its primary formation. Scientists from around the world, studying the earth's crust, collect information about all sorts of significant changes that have ever occurred on the surface of the Earth. Such data are sorted in chronological order and are called geological chronology.
Occurrences and development
At that time, when religious teachings dominated about the divine act that was involved in the formation of the Earth, there was also an opinion about the young age of our planet and the Universe as a whole (it was believed that they formed simultaneously during literally two days about 6 thousand years ago) . This idea was unconditionally accepted by ancient people before the advent and rapid development of such exact sciences as astronomy, chemistry and physics.
Over time, thinkers of antiquity and scientists who lived in the Renaissance expressed their more realistic point of view on how the Earth was formed. According to their assumptions, based on the versatility of changes in the surface and bowels of the planet, the history of its existence significantly exceeds 6 thousand years. Modern scientists from around the world have come to the conclusion that the Earth was finally formed more than four billion years ago. It is worth saying that not everyone agrees with this statement, because they believe that this figure is too high.
Planet Earth BC
This temporary concept gained fame thanks to the trouble of the Honorable Benedictine monk. He used the expressions "our era" and "BC" in his treatises, after which, since 731, most countries of Western Europe switched to a calendar with such a countdown. These changes also affected the geological chronology, which are divided into two unequal periods. The first, the ancient part, dominated the planet much longer than the second, because it was at that time that the origin and development of nature from the smallest living organisms to the vast oceans took place.
The earth BC experienced long and grand changes in order to create the most comfortable living conditions for a modern person. Long-term studies of the earth's crust provided scientists with the opportunity to form a general idea of the formation of our planet as a whole and the origin of life.
Precambrian
The geochronological table begins with the Precambrian eon, which existed on Earth from 4.5 billion to 600 million years ago. During this period, primarily the formation of the earth's crust took place, and later water and land. Active volcanic activity took place throughout the eon.
Catharheus
This period is often referred to as one of the three parts of Precambrian. This is probably an erroneous opinion, since the Cathar-eon has practically nothing to do with its predecessor. At this time, there were no manifestations of volcanic activity, but instead a cold desert dominated the surface of the Earth.
There was only six hours in the days of the Catharhean eon. This period was often accompanied by earthquakes smoothing the landscape. Then the territory of the Earth was covered with regolith - the primary substance of a dark gray color.
Archaea
The author of this term in 1872 was one of the American scientists. Archaea differs from catarchea in the appearance of erosion and a large number of volcanoes. During the time of the Archean eon, which lasted 2.5 billion years, the process of evolution began on our planet.
Despite the fact that there was still no atmosphere, the appearance of anaerobic bacteria that existed in the absence of oxygen occurred. Natural resources such as sulfur, iron, nickel and graphite were formed as a result of the activity of the first living organisms.
Proterozoic
The geological events of this aeon are marked by the formation of mountains with the so-called Baikal folding. Over time, they turned into small hills. Proterozoic rocks were rich in iron, ore and non-ferrous metals. As for the formation of life, this aeon is characterized by the appearance of simple microorganisms, fungi, and algae. At the end of the Proterozoic occur the occurrence of mollusks and worms.
In turn, Proterozoic includes three long-term eras:
• Towards the end of the Paleoproterozoic, atmospheric oxygen concentration occurs at a modern level.
• During the Mesoproterozoic, which consists of potassium, ectasia and stenia, algae and bacteria reach their peak development. Proterozoic differs from other eras in the coldest period, during which ice covered most of the Earth.
• Neoproterozoic includes three stages: tonium, cryogeny and ediac. The periods of the era are characterized by the formation of the first continent - Rodinia, whose slabs soon again dispersed.
Phanerozoic
This aeon completes the geochronological table. Phanerozoic is characterized by a clear period of the appearance of a large number of living organisms having mineral skeletons. The preceding Proterozoic aeon is called hidden, because no traces of life developing at that time were found.
During the Phanerozoic, such large-scale events as the Cambrian explosion (about 540 million years ago), as well as the 5 largest extinctions of living things in the entire history of the Earth, took place.
The era of the Phanerozoic aeon
The first of the three parts of the Phanerozoic is called the Paleozoic. It is considered the era of ancient life and is divided into seven stages:
• Cambrian is characterized by the formation of a temperate climate. The geological dates of this period are marked by the absence of any changes in the landscape; instead, the origin of modern animal species occurs.
• Ordovician . At this time, a warm climate spread throughout the globe, including in Antarctica. Significant sinking of land and the occurrence of fish are also noted.
• The Silurian period is characterized by the formation of inland seas and arid lowlands.
• Devon has a time of the appearance of forests and the first amphibians.
• Lower Carboniferous is characterized by a significant distribution of sharks and ferns.
• Upper and middle carbon.
• Perm - the time when the extinction of most ancient animals took place.
Mesozoic is the second part of the Phanerozoic eon, which includes three periods: the Triassic, Cretaceous, and Jurassic. This period of time is characterized by the appearance, development and extinction of dinosaurs and toothed birds. The geological dates of the Mesozoic are marked by the shallow seas covering the territory of Western America and part of Europe. During this period, the first maple and oak forests formed on Earth.
The third part of the Phanerozoic eon is called the Cenozoic, or the time of mammals. In turn, the era of new life is divided into two stages:
• Tertiary . The beginning of the period is characterized by a warm climate, the development of predators and ungulates, and at the same time the extinction of ancient mammals. Forests spread as much as possible across the planet. About 25 million years ago, apes appeared. A little later, in the Pliocene era, the first people arose.
• The Quaternary phase has four ice ages. At this time, the disappearance of large mammals and the emergence of human society. At the end of the fourth ice age, the climate took on its current form. From the Quaternary stage, the primacy of man on the whole territory of the Earth is firmly established, which lasts until the present moment.