Saturday, September 27, 2008

Geologists Find Oldest Rock: That's Pretty Old

Geologists Don Francis and Jonathan O'Neill of Canada's prestigious McGill University have pushed the estimated formation of the Earth's crust back by hundreds of millions of years with the discovery of a patch of Nuvvuagittuq greenstone at least 250 Million years older than anything previously dated.

As the BBC science page reports:

"Before this study, the oldest whole rocks were from a 4.03 billion-year-old body known as the Acasta Gneiss, in Canada's Northwest Territories.

"The only things known to be older are mineral grains called zircons from Western Australia, which date back 4.36 billion years."

Over the billions since it first formed, most of the Earth's crust has been crushed into particles too small to be recognizable or forced back down into the mantle by plate tectonics where it returns to a molten state.

Which brings us to the important question: this rock is old. We know that. Rocks are old in general, and this one, superlatively so. But is it older than dirt?

The answer is yes.