A new study provides evidence that extreme aridity in the hyperarid core of the Atacama Desert began approximately 45 million years ago, thus significantly earlier than previously assumed. The findings refine current models of desert formation and offer new perspectives on the long-term evolution of one of Earth’s most extreme environments.

The Atacama Desert in Chile | © Benedikt Ritter-Prinz

For the past decades, scientific consensus placed the onset of Atacama Desert aridity in the Early to Mid-Miocene (approximately 10-20 million years ago). Using a novel and extensive dataset, the research team now shows that hyperarid conditions were already established shortly after the global cooling, approximately 45 million years ago, that followed the Early Eocene Climate Optimum (EECO), pushing the timeline of extreme dryness back by around 20 million years. The study was published in Nature Communications under the title “Evidence for Eocene aridification of the Atacama Desert’s hyperarid core“ with colleagues from the Scottish Universities Environmental Research Centre in Glasgow, and the Goethe University Frankfurt.

“Our results indicate that the todays hyperarid core of the Atacama Desert has established since the Mid- to Late-Eocene, indicated by extremely low surface activity,” says Dr. habil. Benedikt Ritter-Prinz from the Institute for Geology & Mineralogy at the University of Cologne. “This makes it one of the longest continuously dry regions on Earth and forces us to reconsider how and when such extreme environments develop.”

Unprecedented Evidence from Earth’s Oldest Surface Clasts

The study is based on cosmogenic nuclide exposure dating, a method that measures rare isotopes formed when cosmic rays interact with minerals at Earth’s surface. The team analysed quartz clasts and quantified concentrations of 21Ne (and partially 10Be), which accumulates only while rocks remain exposed to cosmic rays, i.e. on the Earth surface.

By examining 135 samples, far more than typical studies, the researchers obtained the highest cosmogenic nuclide concentrations of 21Ne ever reported. These exceptionally high values indicate that surface clasts in the Atacama have remained largely undisturbed on the surface for tens of millions of years.

“In more temperate regions, precipitation drives erosion and sediment transport, constantly reshaping the landscape,” explains Prof. Tibor Dunai (University of Cologne). “In contrast, the Atacama’s hyperarid core, with less than 2 millimeters of annual rainfall, shows extraordinarily slow surface processes. The landscape is effectively preserved over geological timescales.”

The findings also provide a revised framework for understanding the mechanisms behind Atacama Desert aridity. While the uplift of the Andes and the influence of the cold Humboldt Current remain important, the study suggests these factors primarily intensified and expanded existing dry conditions rather than initiating them.

Instead, the onset of hyperaridity appears linked to global climate cooling following the EECO, which likely reduced moisture availability in an already semi-arid region. Over time, tectonic and oceanographic changes reinforced and extended these conditions, shaping the desert as it exists today.

The study further highlights that aridity evolved unevenly across the region, emphasizing the importance of spatial variability in long-term climate development.

Linking Landscape Evolution, Climate, and Life at the Dry Limit

The research is closely connected to the goals of the Collaborative Research Centre 1211 “Earth Evolution at the Dry Limit” (CRC1211) at the University of Cologne, which investigates how life and Earth surface processes co-evolve under extreme water limitation.

Water is the defining feature of a habitable planet, yet large parts of Earth exist under severe water scarcity. In such environments, both biological activity and surface processes are strongly constrained, and their interactions remain poorly understood. The Atacama Desert, as one of the driest places on Earth, provides a natural laboratory to explore these relationships.

“Our findings establish a robust long-term climatic framework for one of the most water-limited regions on Earth,” says Dr. habil. Benedikt Ritter-Prinz (University of Cologne). “This is essential for linking the evolution of landscapes with the evolution and adaptation of life under extreme conditions.”

In arid to hyperarid systems, rare and short-lived increases in water availability can leave lasting imprints on the landscape. These transient events may also influence biological colonization and evolution, although such links are still not fully resolved. By extending the record of hyperaridity back to 45 million years, the study provides a crucial temporal context to investigate how climatic fluctuations, surface processes, and life interact at the limits of habitability.

The results of the recent study contribute to a broader effort to identify thresholds for biological colonization, understand tipping points in Earth surface systems, and reconstruct long-term climate histories in extreme environments. They also support emerging research into evolutionary lag times, species adaptation to changing climates, and the interplay between geological processes and biodiversity.

With its large dataset and record-setting cosmogenic nuclide concentrations, the study establishes a new benchmark for investigating long-term landscape stability and climate evolution.

“This work highlights how extremely slow Earth surface processes can operate over tens of millions of years,” says Dr. habil. Benedikt Ritter-Prinz. “It opens new avenues for understanding the relationships between climate, landscapes, and life in the most extreme environments on our planet.”