Extreme aridity in the hyperarid core of the Atacama Desert began about 45 million years ago

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Previously, scientists assumed that the aridity of the Atacama Desert began in the early to middle Miocene, around 10 to 20 million years ago. Using a novel and extensive dataset, the research team now shows that so-called hyperarid conditions developed shortly after the global cooling around 45 million years ago that followed the early Eocene Climate Optimum (EECO). The extreme aridity of the Atacama Desert thus apparently began around 20 million years earlier than previously thought.

Picture of Atacama Desert. Image credit: Benedikt Ritter-Prinz | University of Cologne

The study, “Evidence for Eocene aridification of the Atacama Desert’s hyperarid core,” was published in the journal Nature Communications in collaboration with scientists from the Scottish Universities Environmental Research Centre in Glasgow and Goethe University Frankfurt.

“Our results suggest that the hyperarid core of the Atacama Desert has been forming since the middle to late Eocene, which can be deduced from extremely low surface activity,” said Dr. habil. Benedikt Ritter-Prinz from the Institute of Geology & Mineralogy at the University of Cologne. “This makes it one of the oldest permanently arid regions on Earth and challenges previous ideas about when and under what conditions such extreme environments develop.”

Unprecedented evidence from Earth’s oldest surface clasts
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The study is based on dating using cosmogenic nuclides. This method detects rare isotopes that are created when cosmic radiation strikes and reacts with minerals on Earth’s surface. The team analyzed fragments of quartz—so-called quartz clasts—and determined the concentrations of 21Ne (and, in some cases, 10Be). These are only accumulated as long as the rocks on Earth’s surface are exposed to cosmic radiation.

By examining 135 samples – far more than in other studies – scientists were able to detect the highest concentrations of cosmogenic nuclide 21Ne ever measured on Earth. These exceptionally high values suggest that the clasts on the surface of the Atacama Desert have remained virtually unchanged for millions of years.

“In more temperate regions, precipitation drives erosion and sediment transport, constantly reshaping the landscape,” explained Professor Tibor Dunai of the University of Cologne. “In contrast, the hyperarid core of the Atacama Desert, with less than 2 millimeters of annual precipitation, exhibits extraordinarily slow surface processes. The landscape remains virtually unchanged over geological timescales.”

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

Instead, the extreme aridity apparently began with the global cooling following the EECO, which further reduced the already low humidity in the region. Over time, tectonic and oceanographic changes intensified and expanded these conditions, thus shaping the desert as it exists today.

The study also highlights that the drought developed unevenly in the region, thus underlining the importance of spatial variability for long-term climate development.

Linking landscape development, climate and life at the arid edge
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The research directly builds on the goals of the Collaborative Research Centre 1211 “Evolution of Earth and Life under Extreme Drought” (SFB 1211) at the University of Cologne, which investigates how life and processes on the Earth’s surface develop under extreme water scarcity.

Water is the most important prerequisite for a habitable planet. Yet, many regions of the Earth suffer from severe water scarcity. In such environments, both biological activity and surface processes are severely restricted; their interactions are still poorly understood. The Atacama Desert, one of the driest places on Earth, provides a natural laboratory for investigating these relationships.

“Our results establish a solid long-term climatic framework for one of the most water-scarce regions on Earth,” said Dr. Benedikt Ritter-Prinz of the University of Cologne. “This is crucial for understanding how landscapes evolve and how life adapts to extreme environmental conditions.”

In arid to hyperarid regions, rare, short-term periods of increased water can leave lasting changes to the landscape. Such events can also influence biological colonization and evolution, although these relationships are not yet fully understood. By reconstructing hyperaridity over a period of up to 45 million years, this study provides essential temporal context for analyzing the long-term interactions between climate development, Earth’s surface processes, and life under extreme aridity conditions.

The study contributes to identifying thresholds for biological colonization, better understanding tipping points in Earth’s surface processes, and reconstructing long-term climate trajectories under extreme environmental conditions. It also supports new research approaches to evolutionary lag times, the adaptation of species to changing climates, and the interplay between geological processes and biodiversity.

With its extensive dataset and record-breaking concentrations of cosmogenic nuclides, the study sets new standards for the investigation of long-term landscape stability and climatic developments.

“This work shows how extraordinarily slowly processes can occur on the Earth’s surface over periods of tens of millions of years,” said Dr. Benedikt Ritter-Prinz. “It opens up new perspectives on the interactions between climate, landscapes and life in the most extreme environments on our planet.”

Citation
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The study Evidence for Eocene aridification of the Atacama Desert’s hyperarid core was published in Nature Communications. Authors: Benedikt Ritter-Prinz, Steven A. Binnie, Finlay M. Stuart, Derek Fabel, Richard Albert, Volker Wennrich & Tibor J. Dunai

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