Proterozoic era: the thorny path of earth evolution

2024 Author: Henry Conors | [email protected]. Last modified: 2024-02-12 02:44

The Proterozoic era, which lasted approximately two billion years, played an important role in shaping the world as we know it now. This longest geological period, which occupied almost half of the total history of the planet, was marked by a series of epochal events that reversed the earth's evolution.

It was the Proterozoic era that was "noted" by an increase in water masses in the hydrosphere so that the first seas began to merge into a single ocean on a planetary scale, the level of which eventually reached the tops of ocean ridges. This first tectonic-geochemical milestone was marked by a sharp increase in the degree of hydration of the oceanic lithospheric crust (due to excessive saturation of rift zones with large masses of s alty ocean water). This process took about six hundred million years. And this played a crucial role in the subsequent formation of the relief of the ocean floor.

The Proterozoic era replaced the most ancient historical stage, the Archean. The climate with the beginning of a new era began to change significantly. The surface of the planet, which in the Archean period was a practically bare, cold and lifeless desert with frequent glaciations, underwent significant changes towards the middle of the Proterozoic (in the direction of warming).

At the same time, there was a significant saturation of the atmosphere with oxygen, which radically changed the direction of the evolutionary development of biological organisms. Scientists have already called this fateful event, which occurred about two billion years ago, the “oxygen catastrophe”. This period is characterized by the emergence of the first unicellular aerobic organisms (since the oxygen concentration in the air mixture was sufficient to ensure their vital activity). It was then that most of the species of anaerobic organisms died out, for which molecular oxygen turned out to be fatal. Which, to a large extent, predetermined the further vector of evolutionary development.

During this gigantic time span, microorganisms and algae flourished. Sufficiently intensive processes of formation of almost all sedimentary rocks that marked the Proterozoic era proceeded with the direct (and very active) participation of these life forms.

Eukaryotes, which supplanted the "backward" prokaryotes from the evolutionary scene, also formed when the Proterozoic era began. Air-breathing animals, by the way, appeared on the planet in the same historical period. Most of the fauna of the late Proterozoic era was alreadyrepresented by multicellular eukaryotic forms. The end of this era may well be called the "age of jellyfish", which then prevailed on the planet. At the same time, annelids (progenitors of mollusks and arthropods) arose.

The Proterozoic era was a grandiose historical period during which the eukaryotic cell began to reign supreme. Primitive unicellular and colonial forms of life began to be replaced by highly organized multicellular creatures. Life itself has become an important factor in geological evolution. Living organisms began to take an active part in changing the composition and shape of the earth's crust, they became the basis of its upper layer - the biosphere. Photosynthesis came to Earth, the importance of which cannot be overestimated. It was he who changed the composition of the atmosphere so much, saturating it with a huge amount of oxygen, that it became possible for the development of higher heterotrophic organisms - highly organized animals.

Thus, optimal conditions were created for the arrival in this world of the highest form of life - a man who was destined to change the face of the planet in a short moment of his existence (only 500 thousand years - one instant by the standards of geology!) beyond recognition. And, at the same time, to give the concepts of "life" and "evolution" a completely new meaning …