The 4 stages of the EARTH: from its formation to the present

Since its formation 4.5 billion years ago, the Earth has undergone numerous changes and transformations. This vast period of time is difficult to conceive on a human scale... The history of humanity is just a brief sigh compared to the geological time in which the existence of the planet that is our home is measured. In this lesson from a TEACHER we will go through the different stages of Earth from its formation to the present.

Index

1. What are the stages of Earth?
2. Hádic, the first of the stages of Earth
3. Archaic, the second stage of the Earth
4. Proterozoic
5. Phanerozoic, another of the stages of the Earth

The geological time it is difficult to imagine on a human scale, since geological changes take place over very long periods of time. To better understand the duration of the different stages of the Earth, it is very useful to change the timescale of the history of the Earth using a time period that is easy for us to imagine, such as the duration of a day.

If the history of the earth is represented within the 24 hours that lasts a day, the genus homo would appear 38 seconds before midnight, and our species (Homo sapiens) would have been inhabiting the planet for only 4 seconds. Thus, geological history covers very long periods of time that are measured in units that include millions of years: the Eons.

The largest division of the geologic time scale is the Eon, which in Greek means eternity. Unlike other temporal units or divisions, eons do not have a fixed duration, but are established based on relevant geological events or arbitrarily. These long periods of time are divided, in turn, into smaller periods, the geological eras; which, in turn, are divided into Periods and, these in Epochs.

Thus, the history of the Earth is divided into four great periods or eons that have different durations. Here is a summary of the stages of Earth and then we will analyze them in detail:

• Hádic: this eon includes the period of time that goes from the formation of the Earth 4,600 million years ago to 3,800 million years. The first eon of Earth's geological history represents 13% of total geological time.
• Archaic: It covers the period between 3.8 billion years and 2.5 billion years. This period of time represents 33% of the total existence of planet Earth. During this period, the presence of oxygen in the Earth's atmosphere was insignificant and, instead, methane (CH4) and carbon dioxide (CO2) were abundant.
• Proterozoic: The third eon of Earth's geological history begins 2.5 billion years ago and ends 544 million years ago. That represents 42% of the total geological time and is the longest period. About 800 million years ago the Earth entered a period of tectonic and environmental changes. The oxygen concentration increased, which could open the door to the appearance of larger animals.
• Phanerozoic: It is the eon that goes from the end of the Proteozoic, 544 million years ago to the present. It is the shortest Aeon in the history of the Earth with a duration that represents only 12% of the total. It is a stage in the geological history of the Earth marked by the acceleration in the evolution of living beings that During this stage in the history of the planet they will acquire increasingly complex forms and will conquer all ecosystems. There are also great changes in the climate and in the distribution of the emerged lands at this stage.

The main information about this initial stage of the Earth is provided by the astronomical data and the information obtained since the beginning of the space age allows us to deduce how old the solar system and our planet are.

This is a period for which little information is available, since there are practically no remains of minerals formed during this stage, which have survived to this day. The rocks that emerged at that time were almost entirely destroyed in later stages.

However, although scarce, there are a few samples of minerals belonging to the Hadic. They are small silicate crystals called zircons, which were discovered in river sediments, in Australia, at the end of the 20th century. These small crystals are 4,300 million years old and are proof of the existence of water on the planet in the initial stages of the Earth's existence, since these crystals only form when water interacts with minerals in the rocks.

The birth of planet Earth 4.6 billion years ago

As we have already commented, the first period of the geological history of the Earth it starts 4.6 billion years ago, during the period of formation of the solar system in which the formation of our planet also took place. Earth was formed during formation of the solar system by aggregation of fragments that were joined together by the attraction effect of gravitational forces.

This mass of incandescent rock slowly cooled, acquiring the characteristic structure of rocky planets, with a core of molten metal, a mantle and a solid crust. However, it was not a training process free from violent episodes, on the contrary. The Earth, during her period formation suffered very important cataclysms, among which the one that gave rise to the formation of the Moon 4.533 million years ago.

Thus, the newly formed Earth was an ocean of incandescent magma surrounded by an atmosphere turbulent silicate vapor, which was constantly bombarded by large rocky meteorites and masses of ice.

Formation of the Moon 4.533 million years ago

Moon was formed by the impact of Tea, a protoplanet the size of Mars, against Earth. The impact evaporated the protoplanet and formed an atmosphere of rock and metal that revolved around the Earth. The objects that formed this great cloud of rock and metal were united by the attraction of the forces of gravity until giving rise to the Moon.

Formation of the early atmosphere 4.1 billion years ago

After the first 500 million years, the Earth stabilized and its crust slowly solidified. At the same time, the gases that were released from the interior of the planet, through volcanic activity. These gases accumulated and formed a proto-atmosphere which consisted mainly of water vapor, ammonia and methane. It is estimated that the concentration of greenhouse gases, such as methane, must exceed 90%.

Great meteor shower 3.9 billion years ago

3.9 billion years ago there was an intense shower of rock and ice meteorites that affected the solar system and produced numerous impacts on the Earth and the Moon. Large ice meteorites that struck the Earth's surface contributed enough water to create oceans. This episode of great cataclysms marks the end of the Hadic Aeon.

Image: The directions of change

Archaic is another of the stages of the Earth that you should know. It lasts from 3,800 million years ago to 2,500 million years. At this stage there is already a more important geological record; Are the oldest rocks on the planet and we find them in Greenland and the northwestern region of Australia.

Specifically in the Isua greenstone belt and in the Pilbara region, respectively. These are rocks of metamorphic origin. These rocks have a composition that indicates a shallow marine environment. In these rocks they have been found stromatolites (They are fossil formations that indicate the presence of bacterial life).

This Aeon is characterized by the appearance of first forms of life, after the formation of the oceans.

Episode of major volcanic eruptions 3.6 billion years ago

At this time of the beginnings of the planet's existence, large volcanic eruptions took place with the emission of large amounts of lava, which when solidifying on the surface of the planet gave rise to the appearance of large islands that, later, will give rise to the continents.

Appearance of microbial life forms 3.5 billion years ago

During the Archaic, the first life forms appeared on Earth. These are prokaryotic organisms, possibly it was cyanobacteria, which were photosynthetic bacteria anoxygenic, that is, they carried out a photosynthesis process that did not involve the production of oxygen (O2). They were bacteria that proliferated in shallow marine environments (shallow waters).

Formation of the first protocontinents 3,000 million years ago

3,000 million years ago, the emerging heat from the interior of the Earth was still very high, This caused an enormous amount of magma eruptions and fragmented the primitive lithosphere into multiple small fragments. It may be that the first continents were not much larger than Iceland.

Some authors consider that the first supercontient appeared and decomposed during the Archaic Aeon. This supercontinent is called Vaalbara and it is assumed that it was formed about 3.6 billion years ago and fragmented about 2.8 billion years ago.

This stage of the Earth is characterized by the great evolutionary leap that the appearance of the eukaryotic cell and the multicellular life forms. The biological evolution that takes place in this stage has as a consequence the radical transformation of the composition of the earth's atmosphere, with the phenomenon known as the great oxidation.

Appearance of the first supercontinents 2,000 million years ago.

During the Proterozoic it is believed that a series of supercontinents. The first of them that receives the name of Columbia or Nuna, finished forming about 2,000 million years ago and fragmented about 1,600 million years ago. The fragmentation of the supercontinent Nuna probably took place due to increased magmatic activity. Later, about 1.1 billion years ago, a new supercontinent called Rodinia formed that began to disintegrate about 200 million years ago.

Transformation of the atmosphere 2.5 billion years ago:

Took place the great oxidation and the first mass extinction. During the Proterozoic Eon, the first oxygenic photosynthetic bacteria (which produce oxygen as a result of photosynthesis) and subsequently the first eukaryotic cells also photosynthetic. The oxygen produced by these organisms accumulates in the hydrosphere and in the atmosphere. In this way, the Proterozoic atmosphere accumulates significant amounts of oxygen. The presence of oxygen in water and air could be responsible for the first mass extinction.

First Great Ice Age: The Hureonian Ice Age 2.4-2.1 billion years ago

Although it is not known with certainty what were the causes that produced this first great glaciation, most researchers consider that it was due to the metabolic activity of the first bacteria responsible for the great oxidation that transformed the atmosphere. The change in the composition of the atmosphere led to a drastic decrease in greenhouse gases such as methane (CH4) and carbon dioxide (CO2).

The disappearance of greenhouse gases it would have caused the planet's temperature to decrease. Nor is it known with certainty what was the cause that caused the end of this ice age. It was probably due to a period of intense volcanic activity that caused the planet's temperature to rise.

Appearance of the first eukaryotic cells (with nuclei) 1,800 million years ago

Eukaryotic cells appeared as a result of the prokaryotic cell evolutionwhich gave rise to a hybrid when a primitive prokaryotic cell "engulfs" a primitive bacterium without actually digesting it. This bacterium incorporated into the new eukaryotic cell evolved to give rise to the mitochondria (a membranous organelle responsible for supplying energy to the cell).

Appearance of the first multicellular forms 600 million years ago: marine flora and fauna.

The appearance of the more complex eukaryotic cells with greater organizational capacity, gave rise to the appearance of organisms formed by sets of cells (multicellular organisms) such as green and red algae, polyps, jellyfish, corals, and sponges. It is in all cases aquatic life forms.

The last Aeon of Earth's stages begins 544 million years ago and it reaches the present day. It is a period characterized by the evolution of living beings, and by increasing its diversity. It is also a period with great climatic changes.

Biological evolution

The evolution of living organisms in this stage is very important, for many aspects. It is a stage in which living organisms begin to take much more complex forms and their diversity greatly increases. Notable events include the following:

• Appearance of vertebrates about 545 million years ago. During this period the appearance of marine vertebrate organisms took place. However, millions of years must have passed before the appearance of complex vertebrate animals such as fish that populated the oceans about 460 million years ago. Their appearance led to an increase in the complexity of food chains and ecosystems.
• Appearance of terrestrial organisms 450 million years ago: After 3,000 million years, life leaves the oceans to colonize the terrestrial environment and continental waters, both by plant organisms and by animals.
• Five great mass extinctions: Four of the five mass extinctions that occurred during the Phanerozoic are now considered to have been due to major volcanic eruptions, the last one, which led to the extinction of the dinosaurs 66 million years ago, was due to the impact of a meteorite. In all cases it led to the disappearance of a significant number of species that changed the course of the evolution by allowing other organisms to occupy empty ecological niches and start their expansion.

Formation and fragmentation of the supercontinent Pangea

During the Phanerozoic Eon the last of the supercontinents is formed: Pangeathat began to fragment 200 million years ago to give rise to the current continents.

Big changes in the weather

The Phanerozoic Eon was a period in which great successive climatic changes took place including several glaciations. At the beginning of this stage, the land had a dry climate that became warmer and more humid. And, in successive periods they were alternated glaciations, in which there were drastic drops in temperature; with interglacial periods in which the temperature was warm.

If you want to read more articles similar to Stages of the Earth, we recommend that you enter our category of Astronomy.

• Andrew H. Knoll. (1991). The end of the Proterozoic eon. Paleontology. Research and Science. Barcelona: Scientific Press S.L
• Jan Osterkamp (2021). When there were no mountains on Earth. Geology. Research and Science. Barcelona: Scientific Press S.L
• Abigail C. Allwood. (2017). Signs of life in the oldest rocks on Earth.. Barcelona: Scientific Press S.L.
• J. Brendan Murphy, R. Damian Nance. (2004). The formation of supercontinents. Research and Science. Barcelona: Scientific Press S.L.
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• James O. McInerne and Mary J. O'Connell. ( 2017). New data on the origin of the eukaryotic cell. Research and Science. Barcelona: Scientific Press S.L.