The tale of the oldest rock found in the United States reads a little bit like one of those silly bar jokes. You know the kind, where four geologists, one of them from Wyoming, walk into a bar and start chatting about who has the oldest rock.

In this case it wasn’t a bar, it was Zoom, and there were no beers.

“It was just this sort of idle (question), ‘Which one of us studies areas that have the oldest rock?’” Frost said. “It was almost like a chat, not quite over beer, but that kind of thing.”

Frost’s candidate was rocky crust in Wyoming with bits of the mineral zircon that she has dated back to 3.82 billion years.

“But the way we interpreted that rock, the result was that the rock itself was a bit younger,” Frost said. “So, it was more like 3.45 billion years old. It had just picked

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