Close-up of 2.7 billion years old continental crust from Nunavik, northern Quebec. Martin Simard 
 
 For rocks, time on Earth can be rough. Over billions of years, they might be crushed, eroded, melted, and transformed from what they once were. A rock might have started out as a piece of the planet’s original crust, but 4.3 billion years later, it’s been so changed that no one would know. Aging hurts. 
 
 But two scientists believe they have found a piece of rock that includes components of the Earth’s original crust, as they report in Science. It’s the most direct evidence ever found of how the crust on this planet was composed when it first formed. 
 
 The scientist, Jonathan O’Neil and Richard W. Carlson found the rock in question in Canada, on the eastern shores of the Hudson Bay. Parts of the rock, a granite, are 2.7 billion years old—relatively young, as ancient rocks go. O’Neil and Carlson used a cutting-edge technique, though, to track the decay of samarium-146, an element present only in the early days of the planet, into neodymium isotopes. The neodymium signature of the rocks suggests that the granite was formed directly from the Earth’s original crust. 
 
 What that means is that this section of the original crust, likely a type of basalt, hung out for 1.3 billion years unchanged, before a melting event turned it into granite. That has implications for scientists’ understanding of the development of plate tectonics: if the crust could spend 1.3 billion years in tact, there might not have been much movement of the newly birthed crust. 
 
 The challenge now is to find more instances of this same signature—places where the Earth’s crust has only gone through limited transformation from its very first state. 

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 Around 4.3 billion years ago, a planetary blob of hot molten rock named Earth cooled just enough to start forming a crust. Billions of years later, humans evolved. And now, two of those humans have discovered that a chunk of that original crust is actually still around on the surface today. 
 
 A duo of geologists led by Jonathan O'Neil at the University of Ottawa have just announced the discovery of an ancient chunk of Earth's original crust. It was found near the eastern shore of the Hudson Bay in Northwestern Quebec, in Canada. The rock is a basalt, which O'Neil's team believes was, at one point, underneath the Earth's first oceans. It is surrounded by a cocoon of granite rock that O'Neil and his fellow researcher, Richard Carlson of the Carnegie Institute for Science in Washington D.C., say is also just one geological step away from Earth's original crust. The geologic findings were published today in the journal Science. 
 
 "I think that it's a piece of the original crust. It was cooked, but I think it's still very close to what it used to be," O'Neil tells Popular Mechanics. 
 
 Ancient Fingerprint 
 
 This fascinating research is based on a "scientific technique that's relatively new, only about 10 years old," says O'Neil. Only a handful of geology labs across the globe are using it. 
 
 The technique is basically a method of aging rocks by tracking the decay of an isotope called samarium-146. This isotope is interesting because it existed on Earth only for a short period of time after the planet formed—up until around 4 billion years ago. By then all of Earth's samarium-146 had decayed into another isotope of the element neodymium, and it's now functionally extinct on our planet. 
 
 "It was cooked, but I think it's still very close to what it used to be." 
 
 By studying the ratio of different flavors of neodymium in a given rock, you can gauge how far removed that rock is from rocks that formed during Earth's early cooling. Newer rocks that have melted and reformed a dozen times since the dawn of Earth will have a slightly different ratio of neodymium isotopes. 
 
 Near the shores of the Hudson Bay way up in Canada, O'Neil's team analyzed a collection of granite rocks that we know (through other dating methods) are only 2.7 billion years old. Now, granite cannot have be part of Earth's original crust because you have to form granite by melting and reforming other rocks. But the samarium-146 decay of the granite they discovered strongly suggests it is only one step removed from Earth's original crust. What we the researchers think happened, O'Neil says, is that after 1.3 billion years of existing on the surface, part of Earth's original crust was forced underground, where the intense heat and pressure forged it into the granite we see today. 
 
 The First Crust 
 
 Researchers Jonathan O'Neil and Don Francis returning to camp with backpacks full of rock samples. Alexandre Jean 
 
 This discovery alone would be an impressive find. If you know a sample of rock is only one step removed from Earth's first crust, terra primum, then "by studying the makeup of these rocks, you almost piece together the DNA, so to speak, of these old continents," says O'Neil. 
 
 But alongside these firstborn granite rocks, O'Neil's team also found a basalt that they believe actually is the original crust—which somehow survived its multi-billion-year trip underground relatively unscathed. It's a basalt rock, and it perfectly "fits the composition of the precursor rock we believe formed everything around it," he says. That is, the ratio of neodymium isotopes exactly fits what the geologists would expect to find in Earth's original crust. 
 
 Don Francis, a geologist at McGill University who was not involved in the research, agrees that the find really does look likely to be part of Earth's original crust. "It may indeed represent very early [4.3 billion year old] basaltic crust," he says. 
 
 That's music to O'Neil's ears. "Its an original piece is basaltic crust, I'm convinced it is," he says. 

 The eastern shore of Canada's Hudson Bay. The rocks visible here are 2.7 billion years old, but their precursors may have formed some of the earliest crust on Earth. 
 
 Rocks from the eastern shore of the Hudson Bay in Canada contain elements of some of Earth's earliest crust, new research finds. 
 
 The rocks themselves are granites that are 2.7 billion years old, but they still hold the chemical signals of the precursor rocks that were melted and recycled to form the rocks that exist today. The new study, published online today (March 17) in the journal Science, finds that these precursors formed around 4.3 billion years ago. 
 
 The Earth is 4.6 billion years old, and the astronomical impact that formed the moon took place about 4.5 billion years ago. That makes the precursor rocks to the Canadian granites among the earliest crust after the moon-forming impact, said study leader Jonathan O'Neil, a geoscientist at the University of Ottawa in Canada. [Photo Timeline: How the Earth Formed] 
 
 The new research is an attempt to peek back into the Hadean eon, a mysterious and rather molten phase of Earth history. The Hadean begins with Earth's formation and ends about 4 billion years ago, and very few geological remnants of this era remain. Most rocks from the Hadean were long ago recycled back into the planet's mantle. 
 
 "Rocks that are 3.6 [billion] to 3.8 billion years old or older, we can count them on the fingers of our hand, basically," O'Neil told Live Science. "We have a very limited amount of rock sample to understand the first billion years of Earth history." 
 
 A close-up of 2.7 billion-year-old granite from the Hudson Bay. These rocks are apparently the second generation of rocks on Earth: Their parent rock was around 4.3 billion years old. Credit: Isabelle Lafrance 
 
 The granites found north of Canada's Hudson Bay don't date to the Hadean, but they do butt up against the Nuvvuagittuq greenstone belt, a formation thought to contain the oldest known rocks on Earth, between 3.8 billion and 2.48 billion years old. (The only older geological material are small mineral grains called zircons from Australia's Jack Hills, but the original rocks that held those grains have long since weathered away.) 
 
 Some scientists think that both the Jack Hills zircons and the Nuvvuaguittuq greenstone belt contain traces of the earliest life on the planet, though those findings are controversial. 
 
 O'Neil and his co-author, Richard Carlson of the Carnegie Institution for Science, were interested in the 2.7-billion-year-old granites because they knew that rocks of that sort had to be formed by a "parent" rock that had been buried and partially melted before reforming. The question was, how old was that parent rock? 
 
 To find out, the researchers turned to samarium-neodymium dating, a method that uses ratios of different variations of those two rare-earth elements to determine age. One molecular variation, or isotope, of samarium, samarium-146, no longer exists on Earth: It all underwent radioactive decay within the first 500 million years of the planet's history, O'Neil said. 
 
 Samarium-146 decays into neodymium-142, so any rock that formed after the first 500 million years of Earth's history holds the same ratio of neodymium-142 to other neodymium isotopes. Any rock that shows variation in this neodymium ratio must have formed in the first 500 million years of Earth history, the researchers said. 
 
 Outcrops of 2.7 billion-year-old granite. The rocks that were recycled to form this granite likely formed about 4.3 billion years ago and then persisted as oceanic crust for more than a billion years before becoming submerged and partially melting. They then reformed into the rocks still present today. Credit: Jonathan O'Neil 
 
 It was just that sort of variation that scientists found in the Hudson Bay rocks — a deficit in the neodymium-142 to neodymium-144 ratio compared with modern rocks. 
 
 "It means their parent rock had to be very old," O'Neil said. The researchers also found that the parent rock was likely basaltic oceanic crust rather than dry land. 
 
 The researchers estimate that the parent rock was 1.5 billion years older than the modern granites that survive today. That's interesting not just because the parent rock was some of the earliest crust on Earth, O'Neil said, but because the parent rock stuck around for so long before it was recycled. Today's oceanic crust persists at the surface for only about 200 million years before being pushed back into the mantle and partially melted, O'Neil said. The parent rock of the Hudson Bay granites stayed at the surface for more than a billion years before being recycled, five times as long as today's oceanic crust survives. 
 
 Original article on Live Science.
– Remnants of the planet’s original crust have been unearthed in Quebec, according to a study in Science. The remnants date back about 4.3 billion years and were found embedded in younger granite near Hudson Bay, reports Live Science. While the granite itself is only 2.7 billion years old, the researchers analyzed it for chemical signals of a "parent rock" that had previously melted and been recycled into another form. Popular Mechanics reports that the team used a new and rarely used scientific technique that tracks the decay of a specific isotope, and were thrilled by what they found. "I think that it's a piece of the original crust," says lead researcher Jonathan O'Neil of the University of Ottawa. "It was cooked, but I think it's still very close to what it used to be." The larger granite formation is part of Earth’s second crust, but the geologists believe the parent rock is basalt, or oceanic crust. According to O’Neil, modern oceanic crust usually stays above the surface for 200 million years. It is then forced back into the mantle, where it melts partially. The parent rock the team found in Hudson Bay’s granite, on the other hand, remained at the surface for more than a billion years before being recycled. Atlas Obscura calls it "the most direct evidence ever found of how the crust on this planet was composed when it first formed." (Scientists say they've found an eighth continent.)