At 3.96 billion years old, this gneiss is one of the oldest known Earth rocks. The Earth is 500 million years older still, but little record of that early time has survived our planet's geologic activity.
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Title: Acasta Gneiss
Location: Northwest Territories, Canada, North America
Rights: This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws. http://www.si.edu/termsofuse