you were geological

Geology

2022

We explain what they are and what are the geological eras. Also, what are the eons, periods, epochs and the geological table.

The soil layers demonstrate the climatic, geological and biological conditions of each era.

What are geological eras?

The geological eras of the Earth are the different formal temporal units into which geological time is divided and organized, that is, the history of the formation of our planet. Its duration corresponds to each erathem, which is the time it takes for the rocks of a specific layer of the earth to form. I usually.

Geologic eras are the intermediate units between geologic eons (major category) and geologic periods (minor category). All this according to the Geological Time Scale (GTS) managed by specialists in the field.

The geological eras are evidenced from the fossil record and the constitution of the sedimentary layers of the Earth crust, and allow us to classify and temporarily date the findings we make through excavations, such as fossils, rocks or minerals.

The duration of each era can be highly variable, from a few hundred million years to almost a thousand, depending on the case. There are ten distinct eras, from the end of the hadic eon, the initial and undifferentiated stage of the Precambrian supereon, around 4.6 billion years ago.

The division of the Geological Time Scale into eras began in the 19th century, when the pioneers of the geology and the paleontology began their excavation work and research, and faced the need to classify the layers of the Earth.

They noticed that the difference between one layer and another responded to certain climatic, geological and even biological conditions, so that by digging deep, you were going back in geological time. The first three eras identified belong to the Phanerozoic eon, and are the eras that comprise the life on the planet: Paleozoic, Mesozoic and Cenozoic.

The geological table

As with the rest of the classifications of the Geological Time Scale, the definition of eras responds to conventions of scientists and specialists in the field, since the history of the planet is really a continuity.

However, thanks to this series of conventions, it was possible to establish the Geological Table or Geological Time Scale, which is a diagram ordered and hierarchical in which all the divisions of the history of the planet are detailed:

  • Aeons. The major division of the lapses of weather, occasionally organized into even larger supereons. Two eons are recognized: Phanerozoic (beginning 541 million years ago and leading up to today) and Precambrian (beginning with the formation of the Earth and culminating in the explosion of the Earth). life in the seas), although the latter can also be understood as a supereon, containing three different eons: Hádic (4,600 to 4,000 million years ago), Archaic (4,000 to 2,800 million years ago) and Proterozoic (2,500 to 635 million years ago). of years).
  • Ages. Of which we have been speaking, that constitute the large-scale divisions of each eon, comprising a few hundred million years each.
  • Periods (or systems). Which are the most specific divisions of each era, in which there were important changes in the biota (life) of the moment.
  • Epochs. Subdivisions of the periods, which attend to the general characteristics of The fauna and the flora in that period of time.

What are the geological eras?

The Phanerozoic Eon is the last one and is divided into the Paleozoic, Mesozoic and Cenozoic eras.

As we said before, there are ten geological eras, comprised of four different eons:

  • Hadic Aeon. It does not present division into eras, since it is too remote a time and too primitive conditions in the formation of the planet, as to leave salvageable and studyable evidences.
  • Archaic Aeon. It comprises four different geological eras:
    • It was Eoarcaica. It begins 4,000 million years ago and ends approximately 3,600 million years ago. Its name comes from the Greek words Eo ("Sunrise") and Archios ("Ancient"), and it is where the oldest known rock formations formed. It is possible that life appeared in its earliest cellular forms in this era, but there are no fossil records to prove it.
    • It was Paleoarchic. It begins 3.6 billion years ago and ends 3.2 billion years ago, and is the era from which the oldest known fossil forms come, such as bacteria and others organisms primitive photosynthetic (anoxygenic, that is, they did not yet produce oxygen).
    • It was Mesoarchic. It begins 3.2 billion years ago and ends 2.8 billion years ago. This era witnessed the formation and fragmentation of the first supercontinent, called Vaalbará, and the first ice age in history.
    • It was Neoarchic. It begins 2.8 billion years ago and ends 2.5 billion years ago. It is the era in which microorganisms they started the photosynthesis oxygenic, that is, producing oxygen, forever changing the composition of the atmosphere planetary.
  • Proterozoic Aeon. It comprises three distinct eras:
    • It was Paleoproterozoic. It begins 2.5 billion years ago and ends 1.6 billion years ago. This era begins with a gigantic environmental change known as the Great Oxidation, a consequence of sustained photosynthesis by cyanobacteria in the sea. The main mountain belts that still survive today also emerged.
    • It was Mesoproterozoic. It begins 1.6 billion years ago and ends about 1 billion years ago. In it there is the rupture of the Columbia supercontinent and the formation of another called Rodinia, as well as the substantial beginning of the fossil record, with red algae and colonies of cyanobacteria.
    • It was Neoproterozoic. It begins about 1 billion years ago and ends about 542 million years ago. The most extensive glaciation known in the geological record takes place here, in which the so-called "Snowball Earth" was formed. Towards its end the first appear multicellular organisms, among them the first aquatic animals.
  • Phanerozoic Aeon. It comprises three different eras, which are:
    • Paleozoic era. Also called the Primary Era, it begins about 541 million years ago and ends about 252 million years ago. Its name comes from the Greek and means "ancient life", because in this era the most primitive forms of higher life known from the fossil record arose.It begins after the disintegration of the supercontinent Pannotia and culminates with the formation of another so-called Pangea, dominated by the first reptiles and by plants relatively modern, like conifers.
    • It was Mesozoic. Also known as the Secondary Era, it begins about 251 million years ago and ends just 68 million years ago. Its name, as in the previous case, means "intermediate life", since it is where most of the ancestors of modern life forms appear. In this the reign of the dinosaurs takes place, from their beginnings to their dramatic extinction, and also great orogenic events, such as the gradual fragmentation of Pangea and the positioning of the continents roughly at your current location.
    • It was Cenozoic. Also called the Tertiary Era, it began about 66 million years ago and continues to this day. Its name, in a similar way to the two previous cases, means “New life”, since the world in this period of time reached its current configuration and the forms of modern life emerged, that is, the reign of the mammals. The first higher primates appear in their last 30 million years, and among them the human being, just 200,000 years ago.
!-- GDPR -->