Re: Early Earth likely had continents, was habitable, according to new study

George wrote:
> http://www.eurekalert.org/pub_releases/2005-11/uoca-eel111605.php
>
> Hafnium is found
> in association with zircon crystals in the Jack Hills rocks, which date to
> almost 4.4 billion years ago.
> "These results support the view that the continental crust had formed by
> 4.4-4.5 billion years ago and was rapidly recycled into the mantle"
>
Perhaps, it was the oceanic crust that was formed 4.4 b.y. ago. To form
zircons, or any other silicates, requires oceanic depths around 2 km.
The early continental rocks date to the great oxygen surge of
2.2 b.y.a., the time of Banded Iron Formation and carbonate deposits.
This was the time when oceans receded enough to expose patches of
oceanic crust to an oxygenated atmosphere. The recession (destruction)
of oceans was due to U.V. splitting of water into oxygen and hydrogen,
with hydrogen escaping into space. Blue and orange are hydrogen,
green is oxygen:
http://66.102.7.104/search?q=cache:zBRrPKSaxEIJ:www.astro.washington.edu/endsofworld/+%22The+ultraviolet+glow+of+hydrogen+escaping+from+the+Earth%22&hl=en

John Curtis.

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