Hyperarid Core of the Atacama Desert Has Been Extremely Dry for 45 Million Years

A groundbreaking new study has revealed that the Atacama Desert, long acknowledged as one of the driest places on Earth, has endured hyperarid conditions for an astonishingly longer period than previously estimated. This research, published in the prestigious journal Nature Communications, pushes the onset of extreme dryness back to approximately 45 million years ago, during the Mid- to Late-Eocene epoch. This finding challenges decades of scientific consensus which located the beginning of the desert’s aridity to the Early to Mid-Miocene, about 10 to 20 million years ago, thereby reshaping our understanding of the desert’s climatic and geological evolution.

The international research team, including scientists from the University of Cologne and the Scottish Universities Environmental Research Centre, employed cosmogenic nuclide exposure dating, particularly focusing on isotopes like neon-21 (^21Ne) and beryllium-10 (^10Be). This sophisticated method leverages the interaction of cosmic rays with quartz clasts exposed on Earth’s surface, enabling precise dating of how long rocks have remained undisturbed. Their unprecedented dataset, comprising 135 samples—far exceeding typical sample sizes—yielded the highest ever recorded concentrations of ^21Ne. These levels indicated remarkably little surface disturbance, revealing that the Atacama’s hyperarid core has experienced near-continuous surface stability over tens of millions of years.

Such a finding is extraordinary because it highlights the astounding stability of landscape processes within the desert. Unlike more temperate regions where erosion and sediment transport driven by precipitation significantly reshape terrain, the Atacama’s annual rainfall averages less than two millimeters. This extreme lack of moisture drastically suppresses geological surface activity, preserving Earth’s oldest exposed surface clasts, and reflects minimal physical or chemical weathering. According to lead researcher Dr. habil. Benedikt Ritter-Prinz from the University of Cologne’s Institute for Geology & Mineralogy, these findings cement the Atacama as one of the longest-standing hyperarid environments on our planet.

Previous hypotheses attributed the formation of the Atacama’s extreme dryness primarily to tectonic uplift of the Andes and the cooling effects of the Humboldt Current. While these factors remain influential, this study proposes that the initial trigger for hyperaridity stemmed from a global climate transition following the Early Eocene Climate Optimum (EECO), a period marked by substantial global cooling approximately 45 million years ago. This climatic shift likely reduced moisture availability across an already semiarid region, setting the stage for sustained desertification that tectonic and oceanic mechanisms subsequently amplified and extended.

Importantly, the research reveals spatial heterogeneity in the expansion of aridity across the Atacama region. This uneven progression underscores the complexity of climatic and geological interactions that shape large-scale desertification, emphasizing the necessity of evaluating localized conditions alongside broader global climate trends. The study therefore provides a nuanced framework that connects long-term climate change with regional geological evolution and geomorphological processes.

Beyond earth sciences, this research holds profound implications for understanding the delicate balance between climate, landscape dynamics, and biological systems in the most water-limited ecosystems. The Collaborative Research Centre 1211 “Earth Evolution at the Dry Limit” at the University of Cologne, which assesses co-evolution of life and Earth surface processes under extreme aridity, recognizes the Atacama Desert as a natural laboratory. It presents an exceptional opportunity to investigate how life adapts, persists, or vanishes in the face of prolonged environmental stress, spanning millions of years.

Water scarcity fundamentally constrains biological activity and geomorphological processes in hyperarid zones. Episodic and short-lived increases in water availability—though rare—can leave indelible marks within both soil and rock records, potentially triggering pulses of colonization, evolution, and surface alteration. By demonstrating that the Atacama’s hyperarid state extends back 45 million years, this study provides critical temporal context to interpret such transient events, shedding light on the interplay between climatic perturbations, geological stability, and ecological resilience.

The extraordinary preservation of surface clasts with minimal erosion challenges prevailing paradigms concerning landscape dynamics, revealing that geological processes in hyperarid environments operate on timescales that far exceed those observed in more temperate climates. This realization opens new avenues for using cosmogenic nuclide analysis not only to reconstruct paleoclimate but also to explore thresholds and tipping points in Earth’s surface systems under extreme aridity. Moreover, it aids in identifying lag times in evolutionary adaptation and the biogeographical limits of life.

This milestone advances our comprehension of how hyperarid environments evolve, stabilizing geological formations over tens of millions of years while interfacing complexly with global climate systems. It further substantiates the hypothesis that climate cooling following the EECO was a pivotal driver of desertification—modulated and intensified by tectonic uplift and oceanic changes. Such insights enrich scientific narratives about Earth’s climatic history and enrich predictive models related to future desertification under global change scenarios.

Crucially, the research underscores the value of large-scale multi-sample approaches in enhancing the resolution and reliability of cosmogenic nuclide data. By meticulously analyzing an extensive suite of samples, the scientists achieved unprecedented precision in dating and interpreting landscape exposure ages. Such methodological rigor sets a new benchmark for the field and promises to extend our understanding of other ancient climatic transitions and preserved terrestrial surfaces worldwide.

In conclusion, this landmark study reveals that the Atacama Desert’s hyperarid core has persisted with minimal surface disruption since the Mid- to Late-Eocene, turning it into an unmatched natural chronicle of long-term earth surface stability under extreme dryness. The insights delivered by Dr. Ritter-Prinz and colleagues eloquently demonstrate how climatic shifts, geological forces, and biological resilience intertwine in shaping our planet’s most inhospitable yet scientifically invaluable landscapes. This opens fresh pathways for interdisciplinary research at the crossroads of geology, climate science, and evolutionary biology.

News Publication Date:
20-May-2026

Web References:
http://dx.doi.org/10.1038/s41467-026-73422-4

Keywords

Atacama Desert, hyperaridity, paleoclimate, cosmogenic nuclide dating, neon-21, beryllium-10, Eocene epoch, landscape stability, desert formation, Early Eocene Climate Optimum, tectonics, Humboldt Current, long-term climate evolution