Monday, June 29, 2009

Primordial crust

I never learned about this in my college geology course ("Rocks for Jocks," we called it), but stone has been found that dates to the very origins of our planet. Called primordial crust, the rock was formed when the hot magma that covered the earth cooled during the Hadean period. The first specimen (2nd photo) was found in Northern Quebec, Canada, and is estimated to be 4.28 billion years old. A second specimen has just been located in Orissa state, India, and dates to 4.3 billion years ago. Another ancient rock (3rd photo) - an ophiolite, or piece of oceanic crust embedded in a continent - was found in Greenland in 2007 and dates back 3.8 billion years. (Note that I have indexed this post with fossils, although the rock does not have remains or traces of ancient organisms. Fossilized bacteria has been found from 3.8 billion years ago.)

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