Ancient Rocks Unveil Early Continents, Crust Recycling

New research suggests Earth's earliest times were more geologically diverse than previously thought.

Published on Feb. 4, 2026

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New research led by scientists at the University of Wisconsin–Madison has uncovered chemical signatures in ancient zircon minerals that suggest parts of the early Earth formed continents and recycled crust through subduction far earlier than previously believed, challenging long-held models of a rigid, unmoving "stagnant lid" in Earth's first 500 million years.

Why it matters

The findings have potential implications for the timing of the origin of life on Earth, as the evidence for early continental crust formation and subduction suggests the planet's surface may have been habitable much earlier than the oldest known microfossils.

The details

The study, published in the journal Nature, is based on chemical analyses of ancient zircons found in the Jack Hills of Western Australia. Measurements of trace elements within the zircons using a powerful instrument called the WiscSIMS revealed chemical signatures consistent with subduction and continental crust formation during the Hadean Eon, more than 4 billion years ago. This contrasts with zircons from South Africa that show a more primitive mantle-derived signature.

  • The study analyzed zircons from the Hadean Eon, more than 4 billion years ago.
  • The oldest accepted microfossils are about 3.5 billion years old.

The players

John Valley

A professor emeritus of geoscience at the University of Wisconsin–Madison who led the research.

University of Wisconsin–Madison

The institution where the research was conducted.

WiscSIMS

A powerful instrument housed on the UW–Madison campus that was used to analyze the microscopic zircon grains.

Jack Hills

A region in Western Australia where the ancient zircon samples were found.

South Africa

Another region where Hadean zircons with a more primitive mantle-derived signature have been found.

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What they’re saying

“They're tiny time capsules and they carry an enormous amount of information.”

— John Valley, Professor Emeritus of Geoscience

“What we found in the Jack Hills is that most of our zircons don't look like they came from the mantle. They look like continental crust. They look like they formed above a subduction zone.”

— John Valley, Professor Emeritus of Geoscience

“I think the South Africa data are correct, and our data are correct. That means the Hadean Earth wasn't covered by a uniform stagnant lid.”

— John Valley, Professor Emeritus of Geoscience

What’s next

The researchers plan to continue analyzing additional zircon samples from the Jack Hills and other ancient rock formations to further refine our understanding of the early Earth's geological diversity.

The takeaway

This research challenges long-held models of a rigid, unmoving "stagnant lid" in the early Earth, suggesting the planet's first 500 million years were more geologically complex, with evidence of subduction, continental crust formation, and potentially habitable surface environments much earlier than previously thought.