Rocks are time capsules, storing clues about Earth’s history. A research team from the University of Göttingen and GFZ Helmholtz Centre for Geosciences studied cherts, sedimentary rocks formed from silica-rich mud buried deep under the ocean. While these rocks didn’t reveal clear signs of ancient climate, they did provide crucial insights into heat flow from the Earth’s interior to the ocean floor.

By analyzing oxygen isotopes-16O, 17O, and 18O-in cherts from the Shatsky Rise plateau in the western Pacific, the team discovered that younger oceanic crust allows more heat to pass through, while older crust releases less as it cools over time. Using their own calculation model and confirming results with global ocean data, the researchers measured ancient heat flow for the first time.

Lead author Oskar Schramm said this breakthrough helps understand Earth’s surface conditions up to 3.5 billion years ago. The next step is investigating unusual isotope patterns in some cherts, potentially influenced by volcanic ash.

The findings were published in the journal Geology (2025).