The Crater
At the North Pole Dome in the Pilbara of Western Australia — some of the oldest, least-disturbed crust on Earth — a field of shatter cones marks where something enormous struck. Shatter cones are distinctive striated fractures that form only under the instantaneous pressure of an impact; their presence settles whether. The hard part was when — and “when” turned into a three-way fight.
2.77 → 0.4 Ga · ~half of Earth's history
Match the neighbor, or date the wound
Match the rock next door
A second team found two shatter cones in rock they read as Mount Roe Basalt — dated ~2.77 Ga — and reasoned the impact had to be younger than the basalt it sat in. Reasonable logic. But it pinned the age only to a window from 2.77 billion to 400 million years: roughly half of Earth's history.
Date the wound itself
Kirkland's team dated minerals that grew in the impact’s aftermath — skeletal, impact-modified zircon regrown in the post-shock heat, corroborated by apatite that crystallized as hot fluids moved through the shattered rock. Two mineral systems agreed: 3.024 billion years, give or take seven million.
This is the Caliper Room’s whole lesson, in plainer light than the proton. Field correlation dates a thing by what it sits beside — here, a basalt the shatter cones appeared to lie within. Legitimate, but it inherits all the uncertainty of “next to.” Direct dating reads the clock inside the shocked rock itself — the zircon and apatite reset by the heat and fluids the impact drove through the rock. One method gave an answer two billion years wide; the other gave an answer you could sign.
The Resolution
Kirkland’s team’s direct date — 3.024 Ga ± 7 million years — makes the strongest case yet for the oldest impact on record. If it holds, it pushes Earth’s oldest known impact structure back by roughly 800 million years over Yarrabubba (the previous holder at ~2.23 Ga), and makes the North Pole Dome the only recognized impact crater from the Archean eon — the age when Earth’s first continents were forming. On direct-dating grounds the two-billion-year field-correlation window gives way to a clock read straight from the shocked rock — though, as the dated note below records, the younger-age camp has not conceded.
The 3.024 Ga direct date is the newest and, on method, the strongest evidence — but it has not closed the fight. The dated zircon and apatite grew in hydrothermal fluids driven through the shattered rock, and the open question is whether that mineral growth marks the impact itself or a later fluid pulse. Alec Brenner and Aaron Cavosie (the Science Advances field-correlation team) still read the shatter cones as sitting in ~2.77 Ga Mount Roe Basalt — which would make the impact younger — and lean to the later-fluids reading. Kirkland’s team answers that the case doesn’t rest on zircon alone: shocked quartz, matching apatite ages, and no known regional heating event at that time. So direct dating now leads and the record claim stands on the best current evidence — but two teams still disagree, and the reveal isn’t unanimous. The honest state of the caliper, dated.
The room this belongs to
Sources — go verify
Background: the original ~3.47 Ga claim (Kirkland, Johnson et al., Nature Communications, Mar 2025) and the field-correlation rebuttal placing the impact younger than the ~2.77 Ga Mount Roe Basalt (Brenner, Cavosie et al., Science Advances, Jul 2025) — a dispute still open as of July 2026; previous record holder Yarrabubba ~2.23 Ga (Erickson et al., Nature Communications 2020).