All geological periods and their characteristics

geological eras

Geologic eras serve as intermediate classifications that exist between geologic eons, which represent a major category, and geologic periods, categorized as minor ones. This classification aligns with the Geologic Time Scale (GTS) used by experts in the discipline.

Many people don't know all geological periods and their characteristics, so we are going to dedicate this article to telling you the details about each geological period, each Eon and each geological era in our history.

What are geological eras?

past geological time

Earth's geologic eras represent distinct formal time units that categorize and structure geologic time, reflecting the historical development of our planet. The length of each era aligns with its corresponding erathem, which denotes the duration required for rocks within a particular soil layer to develop.

The geological eras They are indicated by the fossil record and the composition of the sedimentary strata within the Earth's crust., which allows us to classify and temporally date our discoveries from excavations, including fossils, rocks and minerals.

The length of each era can vary significantly, from several hundred million years to nearly a thousand, depending on specific circumstances. There are ten distinct eras, beginning with the conclusion of the Hadean eon, which represents the initial, undifferentiated phase of the Precambrian supereon, approximately 4.600 billion years ago.

The segmentation of the Geologic Time Scale into distinct eras began in the 19th century, when the first geologists and paleontologists undertook their excavation and research work, finding the need to categorize the Earth's strata.

Variations between the layers were found to correspond to specific climatic, geological and even biological conditions, indicating that digging deeper could lead back in geological time. The three initial recognized eras are part of the Phanerozoic eon, which encompasses the eras that constitute life on Earth: Paleozoic, Mesozoic and Cenozoic.

Geological table

geology over time

The Geologic Table, like other classifications within the Geologic Time Scale, reflects the conventions established by scientists and experts in the discipline, since the history of the planet is fundamentally characterized by continuity.

However, thanks to this series of conventions, it became possible to build the Geologic Table, or Geologic Time Scale, which serves as an organized, hierarchical representation detailing all divisions of Earth's history.

  • Eons represent the most extensive divisions of time., sometimes categorized into even larger supereons. There are two recognized eons: the Phanerozoic, which began 541 million years ago and extends to the present, and the Precambrian, which begins with the formation of the Earth and concludes with the emergence of life in the oceans. The Precambrian can also be considered a supereon, spanning three distinct eons: the Hadean (spanning from 4.600 to 4.000 billion years ago), the Archean (4.000 to 2.800 billion years ago), and the Proterozoic (spanning from 2.500 to 635 million years ago).
  • Eras represent significant subdivisions within each eon., and each era spans several hundred million years.
  • Periods (or systems) represent the most precise subdivisions of each era, during which significant transformations took place in the biota (life) of that time.
  • Epochs represent divisions within periods, which reflect the general features of the fauna and flora characteristic of that specific time period.

What are the different geological eras?

characteristics of geological time

As mentioned above, there are ten geological eras categorized within four distinct eons.

  • Hadean Eon. This period does not show a division into distinct eras, as it represents a very ancient era and is characterized by excessively primitive conditions in the formation of the planet, leaving no evidence that can be recovered and analyzed.
  • El Archaic Aeon It spans four distinct geological eras:

Eoarchean Era. This period begins 4.000 billion years ago and ends approximately 3.600 billion years ago. The term is derived from the Greek words Eo, meaning “dawn,” and Archios, meaning “ancient.” It is during this era that the oldest known rock formations were created. While it is conceivable that life arose in its earliest cellular forms during this time, there is no fossil evidence to support this claim.

Paleoarchean Era, which began 3.600 billion years ago and concluded 3.200 billion years ago, marks the period during which the earliest known fossil forms arose. These include bacteria and other primitive photosynthetic organisms, specifically those that were anoxygenic, meaning they had not yet begun to produce oxygen.

Mesoarchean EraSpanning from 3.200 billion years ago to 2.800 billion years ago, this era was marked by the formation and subsequent fragmentation of the first supercontinent known as Vaalbara, as well as the occurrence of the first ice age in recorded history.

Neoarchic Era spans from 2.800 billion years ago to 2.500 billion years ago. This period marks the beginning of oxygenic photosynthesis by microorganisms, a process that generates oxygen and significantly altered the composition of the Earth's atmosphere.

  • El Proterozoic Aeon consists of three separate eras:

Paleoproterozoic Era. This era began 2.500 billion years ago and ended 1.600 billion years ago. It was marked by a major environmental transformation known as the Great Oxidation Event, which resulted from the photosynthetic activities of cyanobacteria in the oceans. In addition, the major mountain ranges that remain today were also formed during this period.

Mesoproterozoic Era. This era began approximately 1.600 billion years ago and ended around 1.000 billion years ago. During this time, the supercontinent known as Columbia broke apart, giving rise to another supercontinent, Rodinia. In addition, this period marked a significant beginning of the fossil record, which features red algae and cyanobacteria colonies.

Neoproterozoic EraThis era began approximately 1.000 billion years ago and ended about 542 million years ago. During this period, the geological record indicates that the most significant glaciation occurred, leading to the formation of what is known as the "snowball Earth." As this period drew to a close, the first species of multicellular organisms emerged, including the first aquatic animals.

  • Phanerozoic Eon. This eon consists of three distinct eras, which are:

Paleozoic era, also known as the Primary Era, spans from about 541 million years ago to about 252 million years ago. The term is derived from Greek and translates as "ancient life", as this period witnessed the emergence of the earliest known higher life forms recorded in fossils. It begins after the fragmentation of the supercontinent Pannotia and concludes with the establishment of another supercontinent, Pangaea, which was characterized by the dominance of early reptiles and relatively modern flora, including conifers.

Mesozoic eraThe Middle Ages, often referred to as the Secondary Era, began approximately 251 million years ago and concluded about 68 million years ago. The term "middle life," like its predecessor, reflects the importance of this period, as it marks the emergence of many of the ancestors of contemporary life forms. This era encompasses the dominance of the dinosaurs, from their inception to their eventual, dramatic extinction, along with major orogenic events, including the gradual breakup of Pangaea and the alignment of the continents into positions resembling their present configurations.

Cenozoic era, often referred to as the Tertiary Era, began approximately 66 million years ago and persists to the present. The term itself translates as "New Life", similar to the nomenclature of previous eras, reflecting the period during which the Earth reached its contemporary configuration and the rise of modern life forms, particularly the dominance of mammals. In the past 30 million years, the first higher primates appeared, with humans emerging just 200.000 years ago.

I hope that with this information you can learn more about all the geological periods and their characteristics.


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