4.3 billion years ago, Earth was just a boiling blob of molten rock and lava that only just started to cool down enough to start having a solid crust. Earth has changed a lot since then, and with all the natural processes breaking down earth’s rocks in the rock cycle, it’s hard to imagine whether we even have any of earth’s original crust left.
Well, a duo of Geologists from the University of Ottawa have found just that: a chunk of rock from Earth’s original crust. It was found at Northwestern Quebec in Canada, around the Eastern shore. It is a basalt rock enveloped within a layer of granite that Jonathan O’Niel and Richard Carlson believe to be underneath Earth’s first oceans.
Source: Youtube, Popular Mechanics
They were able to trace this ancient rock’s age by using a “scientific technique that’s relatively new, only about 10 years old,” says O’Niel. The technique involves tracking the decay of an isotope called Samarium-146. This isotope was only existed in the early Earth for a short period of time- only up until 4 billion years ago. After that, Samarium 146 no longer occurred naturally on Earth, and has decayed into another isotope of Neodymium. They then study the ratio of the different isotopes of Neodymium of the rock, as newer rocks that were melted and hardened several hundreds of times had a different ratio of these isotopes than rocks that were much, much older.
Somehow, they were able to find basalt that they’re pretty sure is part of Earth’s original crust, somehow surviving the billion year trip unscathed. The rock perfectly “fits the composition of the precursor rock we believe formed everything around it,” O’Niel says.
Don Francis, another Geologist at McGill University has agreed that the rock is likely a part of the original crust as well. “It may indeed represent very early [4.3 billion year old] basaltic crust,” he confirms.
That’s all the confirmation O’Neil’s needed. “It’s an original piece is basaltic crust, I’m convinced it is,” he says.
Their findings were published in the journal Science.