Cosmic rays turned ancient sand into a geological time machine

The international research team was led by Curtin's Timescales of Mineral Systems Group at the School of Earth and Planetary Sciences, working with collaborators from the University of Göttingen and the University of Cologne. The scientists examined microscopic zircon crystals collected from ancient beach sands.

Zircon is among the most durable minerals found on Earth. Because it can withstand weathering, erosion and long journeys through rivers and coastlines, zircon grains can survive for millions of years while preserving information about their geological history.

Inside these zircon grains is a rare gas known as krypton. The gas forms when minerals near the Earth's surface are struck by cosmic rays (high-energy, charged subatomic particles from space).

By measuring the krypton trapped inside the crystals, the researchers were able to estimate how long the zircon grains remained near the surface before eventually being buried. This measurement acts like a "cosmic clock," allowing scientists to determine how quickly or slowly ancient landscapes eroded and shifted over extremely long periods.

A New Way to Study Ancient Landscapes

Lead author and Adjunct Curtin Research Fellow Dr. Maximilian Dröllner, who is also affiliated with the University of Göttingen, said the method makes it possible to investigate landscapes that are far older than scientists could previously analyze. The findings could help researchers better understand how the Earth's surface might respond to future climate changes and tectonic activity.

"Our planet's history shows climate and tectonic forces can control how landscapes behave over very long timescales," Dr. Dröllner said.

"This research helps us understand what happens when sea levels change and how deep-seated Earth movements influence the evolution of landscapes."

The study revealed that when landscapes remain tectonically stable and sea levels stay high, erosion slows significantly. Under those conditions, sediments can remain near the surface and be repeatedly reworked for millions of years.

Why These Findings Matter for the Future

Co-author and Timescales of Mineral Systems Group lead Professor Chris Kirkland said the results not only shed light on how Earth's surface has evolved over billions of years but may also inform future planning and land management.

"As we modify natural systems, we can expect changes in how sediment is stored in river basins and along coastlines and continental shelves," Professor Kirkland said.

"Our results show that these processes can fundamentally reshape landscapes, not just coastlines, over time."

Links Between Climate, Sediment, and Mineral Resources

Co-author Associate Professor Milo Barham, also part of the Timescales of Mineral Systems Group, noted that the research has important implications for understanding Australia's mineral resources.

"Climate doesn't just influence ecosystems and weather patterns, it also controls where mineral resources end up and how accessible they become," Associate Professor Barham said.

"Extended periods of sediment storage allow durable minerals to gradually concentrate while less stable materials break down, explaining why Australia hosts some of the world's most significant mineral sand deposits.

"Understanding these links is critical as demand for these minerals continues to grow, as it provides a long-term perspective that can improve models used to predict future environmental and resource outcomes arising from changes to these sediment systems."

The study, titled "Ancient landscape evolution tracked through cosmogenic krypton in detrital zircon," was published in PNAS.