It is necessary to know that the time of the Earth is not divided only into Ages. Experts divide it into:

• Eon. An eon is each of the divisions that comprises about 1,000 million years, but this amount can be much more or less. There are 4 eons, of which the Hadic, the Archean and the Proterozoic comprise what was previously called “Precambrian”, corresponding to the 4 million years before hard-shelled animals appeared.
• Was. Subdivision of the eons, divided into periods. Each era is concerned with a specific flora and fauna.
• Period. It is each one of the divisions of the Ages. For example, the Paleozoic era is divided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods.
• Epoch. Subdivision longer than an Age but shorter than a Period. It helps to specify the conditions of a certain moment. Example: the Holocene and the Pleistocene are epochs of the Quaternary Period, which in turn is part of the Cenozoic Era.
• Age. Subdivision of an era. Rupelian and Chattian are the names of the ages of the Oligocene epoch.

Knowing each of the eons can make it easier to understand the ages. So, the characteristics of the eons are as follows:

• Hadic. This is the oldest aeon, during which the Earth endured the onslaught of numerous asteroids, which caused the outer layers of the planet to melt and the atmosphere and oceans began to vaporize. It ranges from the formation of the Earth, approximately 4.5 billion years ago, to about 4 billion years ago.
• Archaic. Second oldest eon. It started about 4 billion years ago and ended about 2.5 billion years ago. There was great volcanic activity; much of the archean rocks are igneous or metamorphic. It exhibits the first evidence of primitive life on the planet.
• Proterozoic. It ranges from around 2,500 million years to approximately 542 million years ago. During this time, the atmosphere accumulated a large amount of oxygen compared to previous eons, the first recorded ice ages occurred and life forms acquired a more Each type of memory has its own operation, although all of them cooperate to carry out a complete memorization process. This is complex development, while the first multicellular organisms emerged.
• Phanerozoic. It extends from about 542 million years ago to the present. The most important thing that happened at this time is the appearance of the first hard-shelled animals and the abundance and diversity of these organisms. About 542 million years ago, during the Phanerozoic, the first hard-shelled animals appeared.
• Eoarchaic. It is that first part of the Archaic Eon that includes the time after the earth’s crust solidified. It dates from 4,000-3,600 million years ago. Despite the recently solidified crust, it is probable that some areas were still occupied by lava or molten material.
• paleoarchaic. It started 3.6 billion years ago and ended about 3.2 billion years ago. From this era dates the oldest known form of life: primitive bacteria.
• Mesoarchaic. dating? 3,200-2,800 million years ago. There was a supercontinent named Vaalbará , which began to form about 3.6 billion years ago, but broke up precisely during this era.
• Neoarchaic. It dates from 2,800-2,500 million years ago. Photosynthetic organisms began to release an enormous amount of oxygen, which years later proved toxic to most of the prevailing anaerobic (capable of surviving without oxygen) organisms.
• Paleoproterozoic. Start: 2,500 million years. Term: 1,600 million years. It is at this time that the Great Oxidation Event or the Oxygen Catastrophe occurred, as a result of the high levels of oxygen released during the Neoarchaic, which ended the life of most of the anaerobic beings that existed.
• Mesoproterozoic. The second era of the Proterozoic Eon occurred 1,600-1,000 million years ago. There was an advanced development of the continental plates and the evolution of sexual reproduction, a fact that allowed the growth of more complex organisms.
• Neoproterozoic. It is the third and last era of the Proterozoic, and dates from 1,000-542 million years. It is possible that the first multicellular beings developed in this era, as the fossils found seem to suggest. Another striking aspect of the era is the number of important glaciations that occurred; the ice was able to reach areas close to the equator.

The closest geological Ages in time:

Paleozoic

 It spans from 542-251 million years ago and culminates just as Pangea emerges as a supercontinent. During this era the Earth went through a series of momentous geological and climatic changes, as well as a rapid development of animals and the definitive colonization of the mainland.

A large number of trilobite fossils come from the Paleozoic, marine arthropods whose body was divided into 3 well-differentiated lobes. Molluscs and corals also abounded, and amphibians became larger. Already towards the end of the age the development of the reptiles began. In short, the animals diversified to compose the large groups that are already known: amphibians, reptiles, fish, etc.

The climate was likely to have been warm and humid, although by mid-era it had become slightly drier. The Ordovician and Silurian were characterized by the greenhouse effect, while the Cambrian, initially mild in climate, became hotter over its course. The oxygen level increased, while the carbon dioxide levels decreased. Also at the end of the Paleozoic appeared the first plants with seeds, still very primitive.

Mesozoic

It is popularly known as the ” age of dinosaurs”.”, “age of reptiles” or “age of cycads” due to the dominance of this flora and fauna at such a time. It started about 252 million years ago and ended 66 million years ago. Between the limit of the Permian and Triassic periods, a mass extinction of up to 96 percent of marine species and 70 percent of terrestrial vertebrates occurred.

At the end of the era, the mass extinction of the Cretaceous-Tertiary period occurred, an event in which around three quarters of plant and animal species disappeared. Despite these extinction events within its boundaries, the Mesozoic experienced dominance by land, water, and air by dinosaurs and reptiles. The first birds appeared, the cnidarians expanded and the gymnosperms saw their numbers increase. Towards the middle of the era the first angiosperm plants appeared. Birds and mammals evolved from reptiles.

The weather could have been hot and dry. Africa and South America were separated from the then Antarctic-Australia mass and the Indian and Atlantic oceans became more outlined. Pangea was divided into two continents, one to the north, Laurasia, and one to the south, Gondwana. At the end of the Mesozoic, the mainland looked quite similar to today’s continents.

Cenozoic

It started 66 million years ago. It is the “age of mammals” due to the expansion and diversification that they experienced. The climate turned colder and glaciations occurred at the beginning of the Quaternary period.

The continents moved and gradually occupied the position in which they are today, while the movement of the earth’s crust was intense and numerous mountain ranges that persist today, such as the Carpathians and the Alps, developed. Birds and insects diversified to the point of forming the current groups. Mammals adapted to various environments (terrestrial, aquatic and aerial) and reached a superior development.

There were already whales, primates, marsupials, cats, monotremes and other animals that are now extinct, such as the so-called saber-toothed tigers. The dominance of angiosperm plants contrasted with the poor diversity of gymnosperms, of which conifers were the most abundant. As herbaceous plants spread across the land, the first savannahs and grasslands were formed.