The Oldest Rocks, The Pictures

See Main Post: The Oldest Rocks, so far.

The Nuvvuagittuq Belt on the coast of the Hudson Bay in Northern Quebec.
Credit: Science/AAAShttp://www.livescience.com/environment/080925-oldest-rocks.html

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Richard Carlson, Geochemist, Dept. of Terrestrial Magnetism, Carnegie Institution of Washington

Radioactive elements trapped within zircons provide precise ages, but Dr. Carlson and his collaborators at McGill University and the University of Quebec have not found any zircons in the Quebec bedrock. Instead, they determined the age of the rocks from the amounts of neodymium and samarium, two rare earth elements.

Dr. Carlson said the skeptics might be correct that the bedrock could be younger rocks formed out of older material. “The age is pretty certain,” he said. “The interpretation of the age is less certain.”

If the rocks are as old as claimed, the significance would be that “they’re not dramatically different from rocks you would find today in Japan or places like that,” Dr. Carlson said.

In fact, their chemical signature looks most similar to ocean floor that has been pulled under continents, Dr. Carlson said. That suggests that the process of plate tectonics, reshaping and moving continents, could have already started on the very early earth.

At the very least, the existence of solid rock 4.28 billion years ago would run counter to the traditional image of the young earth as a roiling cauldron of magma oceans, a view that is falling by the wayside among researchers as more geological data is unearthed.

http://www.nytimes.com/2008/09/26/science/26rock.html?hp

 

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Don Francis, McGill Univerity 

 

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Australia’s Zircon Crystals

The bits and pieces of rocks that make up the Jack Hills rock formation are ancient—over 3 billion years old. Individual crystals of zircon within the rocks are 4.4 billion years old, only 150 million years or so younger than the age of the Earth itself. These crystals are the oldest fragments of the Earth yet found. (Photograph copyright Bruce Watson, Rensselaer)

http://earthobservatory.nasa.gov/Study/Zircon/

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