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Hadeon Eon

            The Hadeon Eon, sometimes considered part of the Archean Eon, marked the formation of Earth. Little was known about this time because the evidence on Earth from this Eon had not been preserved due to the planets ever changing geology and climate. At this time, earth would be considered a Class E planetoid, after it had grown to around 10,000 km in diameter. The surface would have been either completely or partially molten, and temperatures would have been extremely high. There would be little to no solid rock on the surface, until the planet could cool down.

            Due to accretion, the surface was under a constant bombardment of meteorites, and volcanism was extensive. As the crust began to cool into solid rock, the surface would crack to allow for heat of the molten rock below to escape. This was due to a high geothermal gradient, causing a decreased heat flow from the surface to outer space than we see today. Also, the bombardment of meteorites impacting the earth tore holes into the surface allowing even more molten rock to poor through. This process would go on for hundreds of thousands of years, and was known as the late heavy bombardment, which ended approximately 3.8 billion years ago.

            Although surface temperatures were extremely high, sporadic detrital zircon crystals dated as far back as 4.3 Billion Years Ago indicate that at least by this time earth had some oceans or seas. During this time it is believed that Earth went through a rapid cooling phase where the crust began to solidify, allowing for water to condense on the surface. The crust would still be partially molten, however temperatures on the more solid and rocky continents would have been cool enough for shallow seas to form. This period most likely came to an end when the Late Heavy Bombardment began around 4.1 Billion Years Ago, causing breaks in the solid surface allowing for molten rock to once again cover most of the surface.


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