Along the eastern coast of Hudson Bay in Quebec, Canada, near the Inuit community of Inukjuak, lies a band of volcanic rock with a striking mix of dark and light green hues, dotted with pink and black specks. Recent scientific analysis has revealed that these rocks are the oldest known on Earth. Using two separate dating techniques, scientists determined that rocks from the Nuvvuagittuq Greenstone Belt in northern Quebec are approximately 4.16 billion years old, dating back to the Hadean eon. This era, named after the Greek god of the underworld Hades, reflects the intense and hostile conditions believed to have existed on early Earth.

The study suggests that the Nuvvuagittuq Greenstone Belt contains some of the planet’s earliest crust—the solid outer layer of Earth. These rocks are mostly altered basaltic volcanic rocks, which means they have undergone changes due to extreme heat and pressure. Basalt is a typical volcanic rock. The rocks tested were identified as "intrusions," meaning they were formed when molten rock (magma) forced its way into older rock layers and then solidified underground. Researchers analyzed the decay of radioactive elements samarium and neodymium within these rocks, and both methods yielded the same result: an age of 4.16 billion years.

Further chemical analysis of these rocks could provide rare insights into Earth's earliest conditions, a period still largely unknown due to the scarcity of ancient physical evidence. According to University of Ottawa geology professor Jonathan O’Neil, who led the study published on June 26 in Science, these rocks provide a unique glimpse into how Earth’s first crust formed and the geological forces at play at the time.

O’Neil explained that the rocks might have solidified when rain—evaporated from ancient oceans—fell onto molten surfaces. Since some of these rocks originated from minerals precipitated from early seawater, they could help scientists understand the composition and temperature of the first oceans and the environment that may have supported the beginnings of life. Previously, the oldest known rocks were from Canada’s Northwest Territories, dating to around 4.03 billion years. Although older zircon crystals (about 4.4 billion years old) have been found in western Australia, these are individual mineral grains, not entire rock formations.

The Hadean eon spanned from Earth's formation around 4.5 billion years ago until about 4.03 billion years ago. During its early stages, a major impact likely led to the creation of the Moon. But by the time the Nuvvuagittuq rocks formed, Earth had started to resemble the planet we know today. O’Neil noted that, despite the name, Earth wasn’t a completely molten sphere throughout the Hadean. By about 4.4 billion years ago, it had already developed a solid crust, probably made mostly of basalt, and was covered by shallow, warm oceans. The planet also had an atmosphere, though quite different from the one we breathe now.

There had been debate over the age of the Nuvvuagittuq rocks. A 2008 study produced mixed results, with some samples dated at 4.3 billion years and others between 3.3 and 3.8 billion years. O’Neil explained that the discrepancies likely came from one method being more affected by later heating events, which distorted the results. With the latest study using two consistent dating methods, the age of the intrusion rocks is now confidently set at 4.16 billion years. Since these intrusions formed within older volcanic rock, the surrounding rock is estimated to be around 4.3 billion years old, aligning with earlier research.