Rocks dating back to the Earth’s Hadean Eon, first discovered in 2008, have now had their age confirmed at at least 4.16 billion years, offering scientists a rare window into the planet’s earliest history shortly after its initial cooling.
Following Earth’s formation 4.5 billion years ago, the planet gradually cooled into a somewhat finished, yet ever-evolving world. These ancient rocks represent the only surviving fragments of crust from that distant period. While the rocks are not quite as old as the earliest estimates of 4.3 billion years, they still hail from the planet’s formative years.
Hadean Eon Rock Samples
“It’s not a matter of ‘my rock is older than yours’,” said co-author Jonathan O’Neil, a geologist at Ottawa University. “It’s just that this is a unique opportunity to understand what was going on during that time.”
The rocks were discovered in a region of Northern Canada known as the Nuvvuagittuq Greenstone Belt. This formation consists mainly of material that began as volcanic basalt before being transformed by Earth’s tumultuous history. Geologists have found only a handful of rock samples dating back 3.8 billion years or older. The next oldest after Nuvvuagittuq comes from Canada’s Acasta gneiss formation, dated to about 4 billion years old.
What sets Nuvvuagittuq apart is that its samples are firmly rooted in the Hadean Eon, while the Acasta rocks straddle the boundary between the Hadean and the subsequent Archaean Eon. Another remnant of Earth’s earliest crust comes from tiny zircon crystals embedded in younger rocks from Western Australia, dated to 4.4 billion years ago.
The Nuvvuagittuq Greenstone Belt
The Nuvvuagittuq Greenstone Belt forms the oldest exposed rocky landscape on Earth. However, tensions have arisen as efforts to extract samples have altered the terrain, prompting the local Inuit community to restrict access to the area earlier this year.
The land is managed by the Pituvik Landholding Corporation on behalf of the Inuit. The group has barred further research at the site, citing previous damage to the landscape. Only previously collected samples can now be studied. Their concerns stem from large-scale removals that left visible scars and from reports of individuals selling samples for over $10,000.
“It’s unfortunate, but I would do the same,” O’Neil said of the community’s decision.
Dating The Nuvvuagittuq Samples
The initial 2008 dating relied on tracking the decay of samarium-146 into neodymium-142. Since samarium-146 disappeared from nature about 4 billion years ago, this method provided an estimate. However, some researchers argued that contamination from younger crust could have skewed the results.
In the latest study, scientists analyzed younger molten rock that had intruded into the Nuvvuagittuq formation. By studying these later formations, they could establish a minimum age for the entire belt. The team used two isotope decay systems: samarium-146 into neodymium-142, and samarium-147 into neodymium-143. Both methods yielded the same result: 4.16 billion years, strengthening confidence in the rock’s age.
Debating the Hadean Results
“If you don’t agree with this, then you need a very speculative, intricate model to get to the same answer,” said O’Neil.
Even so, some scientists remain cautious. Bernard Bourdon, a geochemist at the University of Lyon, noted, “I would be happy if these rocks were truly Hadean, but I think we still need to be cautious.”
Others are more convinced. Richard Carlson, a geochemist at Carnegie Science, said the findings “provide a new data set that hopefully can advance this discussion.” He believes the evidence strongly supports the age determination.
Overall, the confirmation of these ancient rocks not only deepens our understanding of Earth’s earliest history but also highlights the challenges and responsibilities of studying such precious remnants of our planet’s past.
The paper “Evidence for Hadean mafic intrusions in the Nuvvuagittuq Greenstone Belt, Canada” appeared on June 26, 2025, in Science.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.