Oldest rock pushed back to 4.28 billion years
A new study by McGill University geologist Jonathon O’Neil reports the discovery of basalt rocks from northern Quebec that date to a record 4.28 billion years ago – a time when the planet was still a primordial hellscape of gnarled volcanic slag, steaming oceans, and a heavy sky filled with screaming incandescent bombs from space.
Dating from a period just after the accretion of the planet and the formation of the Moon, these are the oldest intact Earth rocks ever found. Older mineral particles have been found, dating to 4.36 billion years, but those were individual grains of rare and long-lasting minerals like zircon, and were found inside much younger whole rocks.
Unlike meteorites and the Moon, very few rocks on Earth’s surface date from the accretionary dawn of the planet. Our world has wind and water and plate tectonics, all of which constantly recycle surface materials. Finding rocks from such a primal phase of Earth’s formation tells us not only what the planet was like back then, they give us crucial information about how rocky planets like ours form, and how quickly, elsewhere in the universe.