Science

MELISSA BLOCK, Host:

From NPR News, this is All Things Considered. I'm Melissa Block.

MICHELE NORRIS, Host:

And I'm Michele Norris. Geologists say they've discovered some rock in Canada that may be the oldest in the world. The rock may have formed soon after the birth of our planet, as NPR's Nell Greenfieldboyce reports.

NELL GREENFIELDBOYCE: The Earth started its life about four and a half billion years ago. At first, scientists think it was like a big, hot blob of magma. Then it began to cool and formed a rocky crust. Geologists would love to find samples of those early rocks to help them understand what the Earth was like back then and how the continents emerged. But it's not easy to look this far back into the past because the planet's surface is constantly changing.

Scientists have found some ancient rocks. One, in Canada's Northwest Territories, is known to be about 4 billion years old. But now, researchers say they may have something even closer to Earth's beginnings. Jonathan O'Neil is a geologist with McGill University in Montreal. He knows this is a bold claim.

BLOCK: Of course, there is going to be controversy. I'm expecting that.

GREENFIELDBOYCE: To get to this rock, he has to take a plane up to a remote Inuit village. Then he takes a canoe down the Hudson Bay to a spot on the tundra where the flat bedrock is exposed.

BLOCK: When you actually walk on the rock, it's kind of special just to think, well, I could walk here like 4.3 billion years ago, and I would probably walk on the same rock.

GREENFIELDBOYCE: That's because the rocks may have formed that far back. In the journal Science, O'Neil and his colleagues present evidence that suggests the rocks could have emerged just a few hundred million years after Earth began. John Valley, a geologist at the University of Wisconsin-Madison, says scientists have expected that they should be able to find rocks from this early time period.

GREENFIELDBOYCE: And we've always been puzzled by our failure to find them. So the question then arises, were the earliest rocks completely destroyed by some unusual process? Or do these early relics really exist, and we just don't know how to recognize them?

GREENFIELDBOYCE: This new study used an unconventional dating technique that's previously been used on meteorites. Valley says it looks like this method should be able to help scientists identify sections of the Earth's early crust.

GREENFIELDBOYCE: Possibly, there are even rocks as old as 4.3 billion years. And if that's correct, then they may hold the key to timeless questions about the evolution of the Earth and possibly even the emergence of life.

GREENFIELDBOYCE: He says life can only exist under certain conditions. So finding the earliest rocks could help geologists understand when exactly the Earth became friendly enough for life to evolve. Nell Greenfieldboyce, NPR News.

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