The Precambrian era is the era that covers most of the history of the Earth , starting from the creation of the planet approximately 4.5 billion years ago until reaching the appearance of the different forms of life, complex and multicellular, almost four billion. years later. The Precambrian is considered the oldest of the geological ages , which are marked by different layers of sedimentary rock . These layers of rocks located over millions of years have an important recordpermanent with respect to the Earth’s past, including also the fossilized remains of plants and animals buried when the sediments formed .
What is the Precambrian era?
The Precambrian era is one of the major periods on earth. In geology , it is the first stage in the formation of the earth and it was the moment in which the first forms of primary life of antiquity began to emerge .
- What happened in the Precambrian era
- Periods of the Precambrian era
- Fauna of the Precambrian era
What happened in the Precambrian era
The earth was more than 600 million years old when life began. The planet, after being molten, had cooled, developing a solid crust and oceans had arisen created from the water vapor in the atmosphere . Many scientists think that these early seas were responsible for giving rise to life, with hot, mineral-rich volcanic vents that catalyzed chemical reactions on the surface to shape the first cell membranes .
The Precambrian was a period in which important geological modifications occurred . Scientists believe that volcanic activity was responsible for sending carbon dioxide and water vapor into the proto atmosphere , causing a drop in temperature which caused the rocks to solidify.
The first living organisms to emerge in the Precambrian era were microscopic bacteria , which according to the fossil record were born about 3.4 billion years ago. As multiplied and ended his supply of energy , bacteria sought an alternative energy source. Then new varieties appeared that harnessed the power of the sun through a biochemical process known as photosynthesis , a movement that would eventually lead to simple plants and that opened the planet to animal life .
The atmosphere at that time had no oxygen but it managed to be released from the seas as a by-product of photosynthesis by cyanobacteria . Gas levels gradually increased. About 800 million years ago, oxygen levels reached about 21 percent and in this way began to give life to more complex organisms. The oxygen-rich ozone layer also established itself, protecting the Earth’s surface from harmful solar radiation .
The main characteristics of the Precambrian era are the following:
- The hydrosphere was formed and also the atmosphere.
- The first continental nuclei appeared, which were called by the name of cratons.
- There was a period of great ice age .
- Different glacial periods emerged alternated with other periods of a desert character.
- It occupies 88% of the history of the earth.
- The most important geological modifications occurred.
- Volcanic activity dumped carbon dioxide and water vapor into the proto-atmosphere.
- The rocks solidified on the ground.
- Oxygenation of the atmosphere occurred.
- The first life forms began to emerge on earth.
Periods of the Precambrian era
The periods of the Precambrian era were as follows:
- Hadic Aeon : it was a period that took place in the Precambrian period that was between 4,500 and 3,800 million years ago. At this stage there was a great meteoric bombardment and the Earth , the Moon and the lithosphere were formed .
- Archaic Eon : this stage covers the phase that goes between 3,800 and 2,500 million years and was the stage in which the first continents arose and was the moment in which plate tectonics originated .
- Proterozoic Eon : it was the period between 2,500 and 540 million years. At this stage it was the moment in which the first continents emerged that together gave shape to the Pangea , it was the moment in which the first eukaryotic cells appeared and when the Ozone layer was formed .
The prevailing climate in the Precambrian era was very unstable and much colder than in the Archaic. It was in this period that the largest ice ages known throughout the history of the Earth occurred, which were caused mainly by the existence and disposition of the supercontinent Rodinia , which did not allow heat to be properly distributed .
Fauna of the Precambrian era
It is difficult to know exactly which animals lived during this time as fossils have only been found in small quantities. This is due to the alteration of the sedimentary rocks after the period. The fossils that have been found indicate that there were protozoa , bacteria , coelenterates and algae .
During the Precambrian era the first forms of plants appeared. You could mainly find algae , which although they do not belong to the plant kingdom, had some similar characteristics. They also helped to carry out photosynthesis .