The United States’ oldest known rock has existed for at least 3.6 billion years

The United States’ oldest known rock has existed for at least 3.6 billion years

More than just a cool bit of trivia, the finding raises questions about our understanding of Earth’s history.

An altered sign in the Minnesota River Valley proudly proclaims "the oldest rock in the world." Built in 1975, it marks a Gneiss of 3.8 billions – at least scientists have thought. It turns out that it is not the oldest rock in the world (since 2019, that [...]