EARTH IS THE AIM 7 , Mu and the other worlds ; Chapter 5: History of the Planet Earth

Mu and the other worlds

Chapter 5: History of the Planet Earth

 

 

The Origin of Life on Earth

Although there are still many unanswered questions, one begins to glimpse the origin of life on Earth

Life appears on Earth probably about 4.3 billion years ago

 

The numerous collisions of meteorites and comets with the Earth brought us the water of the primitive oceans

These meteorites and comets that came to plant on its soil also contained particles that seeded the Earth

Some of these particles have proved to be able to evolve towards the living

 

We will try to reconstruct this long and beautiful story

But we must begin with the beginning, that is, with the history of our planet in the Universe

 

The Universe and the Sun

The age of the Universe is estimated at about 13.8 billion years   The generally accepted theory of its formation, is the Big Bang:

The Universe was a concentrate of energy that suddenly exploded

 

This was the beginning of its expansion

As it moved away it cooled and some of this energy became material

This material is at the origin of galaxies, stars and other celestial bodies such as nebulae

 

The galaxy of the Milky Way formed about 13.21 billion years ago

About 4.6 billion years ago a Milky Way star exploded into a supernova that sent a shock wave over a nebula

It collapsed into a cloud of gas

Part of this cloud has turned into an accretion disk, creating the solar system

 

This disc was a cloud of dust, rocks and gas

Most of these materials were concentrated towards the center of the disk and began to heat up

This rise in temperature triggered the nuclear fusion of hydrogen to transform it into helium

As the kinetic contraction increases further, about 4.57 billion years ago, the central cluster becomes a star:

Our Sun

 

The Earth and the Solar System

The rest of the materials of the solar disk, by collisions and accretions creates protoplanets

About 4.56 billion years ago, one of these becomes the Earth

As the Earth continues to be bombarded by asteroids, comets and other celestial bodies, it began to burn from inside because of the heat caused by these successive shocks

 

During the first forty million years of the Earth, the iron and nickel contained in this molten mass melted and flowed towards the center of the planet to form by contraction a solid nucleus

The residual liquid iron then creates a magnetic field around this nucleus, which will ensure the protection of the planet against cosmic rays

 

Massive_Smash-Up_at_Vega

NASA / JPL-Caltech: Artist’s concept of a celestial body of the moon   http://www.nasa.gov/multimedia/imagegallery/image_feature_1454.htm   Photo Wikipedia public domain: Originalwana, Cmlisse, Bot

 

Then about 4.533 billion years ago, the Earth was struck by Theia

It was a planet of the size of Mars, also formed by accretion, substantially on the same orbit as the Earth

The same orbit, different sizes involving different orbital speeds:

The collision was inevitable

 

The ejected pieces then formed a ring around the Earth which by accretion became the Moon

This impact changed the axis of the Earth in an inclination of 23.5 ° which created the seasons on our planet

With a 0 ° axis, there would be no season

The impact also accelerated the rotation of the Earth and thus initiated the tectonics of the plates

 

The eons

The eon is a time interval corresponding to the division of the geological time scale   The history of the Earth is divided into four eons

 

Radiometric dating, that is to say the measurement of the residues of the radioactive elements still present, makes it possible to delimit the different era, thanks to the known disintegration times

Eons are used as a time scale for all planets

 

The first three eons cover the first 4 billion years of Earth’s history and are grouped into a super eon:   The Precambrian

 

The three eons of the Precambrian of the Earth are:

The Hadean, from – 4.56 to – 4 billion yearsThe Archean, from – 4 to – 2.5 billion years

The Proterozoic, from – 2.5 billion years to – 541 million years

 

The last eon of the Earth is:

The Phanerozoic, from – 541 million years to the present day

 

The Hadean

The Hadean begins with the formation of the Earth, about 4.56 billion years ago and ends 4 billion years ago

Hadean comes from Hades, god of hell, given the state of the surface of the Earth at that time

This eon corresponds to the stabilization of the Earth

 

During the Hadean, the magmatic ocean and the metallic nucleus differentiate and the continental crust forms

After this separation, atmospheric pressure was around 200 bar

The oceans could thus begin to form as soon as the surface temperature became less than the critical temperature of the water, ie below 350 ° C at such a pressure   This water precipitated the formation of the rocks and the tectonics of the plates was able to start, which allowed the differentiation of the continental and oceanic crusts

 

Towards 4.3 billion years, the conditions necessary for the emergence of life are gathered

In 2015 , carbon inclusions of organic origin have been discovered in the Jack Hills area of Western Australia and have been dated of – 4.1 billion years

In 2017, fossilized microorganisms found in the Nuvvuagittuq greenstone belt in Quebec were dated from – 3.77 to – 4.28 billion years

These discoveries confirm the origin of life on Earth as early as the Hadean

 

The Archean

Archean comes from the Greek Arkhē, meaning:

Beginning or origin

Before the recent discoveries, emergence of life on Earthwas admitted to be

4 billion years ago

 

The Archean decomposes into four eras:

The Eoarchian, from – 4 to – 3.6 billion years , is the era of appearance of prokaryotes

The Palaeoarchaean, from 3. 6 to 3.2 billion years ago ,is the era of the earliest known

life form with the discovery of a bacterium of 3.46 billion years old

The Mesoarchy, from – 3.2 to – 2.8 billion years , is the era of appearance of stromatolites

The Neoarchy , of – 2.8 to – 2.5 billion years, is the era of the formations of most of the rocks, but some older rocks are dated from the Hadean

 

During the Archean, the energy of the Sun received on the Earth was 25 to 30% less than today

There was quite no land

Most of the rocks formed during the Archean

The two main types of rocks are metamorphic rocks and magmatic rocks   Metamorphic rocks originate from sedimentary rocks amalgamated by high temperatures and pressures

The magmatic rocks are due to the volcanic activity which was much more important than nowadays

 

The absence of rocks of more than 3.8 billion years would be due to the collision of the Earth with a large number of meteorites or comets between 4.1 and 3.8 billion years during the great bombardment

The impacts probably removed all traces of anterior rocks

 

The Proterozoic

Proterozoic comes from the Greek meaning:

Before the animal

It goes from – 2.5 billion years to – 541 million years

 

It is divided into 3 era:

The Paleoproterozoic

The Mesoproterozoic

The Neoproterozoic

 

The Proterozoic is characterized by a very quick continental accretion leading to the creation of the supercontinent of the Pangea and the mountains

 

The oxygen content in the air, which is only 1 to 2% at the beginning of the Paleoproterozoic, will then increase gradually and this event is called:The Great Oxidation

 

From the beginning of the Paleoproterozoic one observes the first glaciations At the Neoproterozoic, appeared soft-body organisms

Trilobite fossils have been discovered in rocks dating from the late Neoproterozoic, which allows to date their appearance from the late Precambrian

 

The Phanerozoic

The Phanerozoic comes from the Greek meaning: visible animal   It covers the last 541 million years until today and tomorrow   As the name suggests, it will end when we cease to exist …

 

The Phanerozoic is divided into three eras:   The Paleozoic, from – 541 to – 251 million years   The Mesozoic, from – 252 to – 66 million years

The Cenozoic, from – 66 million years to the present

 

At the beginning of this era, life forms are limited to bacteria, algae, sponges and other unknown organisms

Then we see the appearance of small animals with shells

It is the beginning of the biodiversity with the appearance of terrestrial plants, the evolution of fish and their conquest of the earth, and then the evolution to the present fauna and flora

 

Towards the end of the Paleozoic, during a period called Carboniferous, large forests of plants are formed which will become layers of coal

 

During this era, the tectonics of the plates will separate the Pangea to form the present continents

 

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About DOUGLAS MOONSTONE

money is the human predator
This entry was posted in Archean, eons, Hadean, History of the Planet Earth, Phanerozoic, Proterozoic, The Earth and the Solar System, The Universe and the Sun, Theia, Uncategorized. Bookmark the permalink.

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