Hadean Eon

The team.

We will speak to you of one of the divisions in the geological temporal scale, denominated Hadean is the first division of the Precambrian or era geological. It begins at the time when the Earth formed about 4560 million years ago and ends 4,000 million years ago, when the Archaic era began.

To know more about this division or geological stage, let us see some of its characteristics and start with the etymological meaning of the word Hadean.

The Hadean

Etymology.

Etymologically, the word Hadean comes from the Greek word Hades.

Hades, in addition to naming the Greek god, also designates the Greek underworld.

As the Greek underworld was covered with fire, water, deads, monsters and titans, the Hadean Eon is related to a stage of heat and confusion.

In this way, the underworld is compared to the infernal conditions prevailing on Earth at that time, since the planet had just formed and was still very hot due to three things:

First, due to its recent accretion, whose theory suggests that the planets were formed by condensation of small particles of cosmic dust into large bodies.

Second, thanks to the abundance of short-lived radioactive elements.

And finally, by the frequent collisions with other bodies of the Solar System.

Characteristics

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The Hadean Eon is characterized by Earth’s initial formation from the accretion of dust and gases and the frequent collisions of larger planetesimal.

This means that the rocks collided and made a larger one, until forming the planet.

Hadean rocks

The oldest dated rocks on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history. Such rocks are exposed on the Earth's surface in very few places. Some of the oldest surface rock can be found in the Canadian Shield, Australia, Africa and in a few other old regions around the world. The ages of these felsic rocks are generally between 2.5 and 3.8 billion years. 

In the last decades of the 20th century geologists identified a few Hadean rocks from Western Greenland, Northwestern Canada, and Western Australia.

The oldest dated zircon crystals,enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of 

the Narryer Gneiss Terrane of Western Australia,  Ga—around 200 million years after the hypothesized time of the Earth's formation.

The oldest dated zircon crystals.

Atmosphere and oceans

A sizeable quantity of water would have been in the material that formed the Earth. Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. Hydrogen and helium are expected to continually escape (even to the present day) due to atmospheric escape.

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