The landscape has effectively been preserved on geological timescales
In the stillness of the world's driest place, ancient pebbles have quietly held a secret that rewrites Earth's climatic memory. Researchers from the University of Cologne and Scotland's SUERC Centre have determined that the Atacama Desert's hyperarid core has persisted for at least 40 million years — twice as long as science had accepted — tracing its origins not to the rise of the Andes or shifting ocean currents, but to a global cooling that followed the Early Eocene Climate Optimum. This discovery asks us to reconsider not only how deserts are born, but how landscapes can lock themselves into states of near-eternal stillness, becoming archives of deep time written in stone.
- The established 15-to-20-million-year timeline for the Atacama's formation has been overturned, forcing a fundamental rethinking of desert genesis and long-term climate stability.
- Cosmogenic nuclides trapped in undisturbed quartz pebbles revealed concentrations so extraordinarily high that they point to surfaces frozen in place for tens of millions of years — a geological clock no one had thought to read this way.
- The Andes uplift and cold ocean currents, long credited as the desert's creators, are now recast as amplifiers of an aridity that was already ancient when those forces took hold.
- A self-reinforcing feedback loop — where hyperarid soils absorb scarce rainfall, prevent erosion, and deepen over time — helps explain how the Atacama has sustained its extreme dryness across incomprehensible spans of time.
- The extended timeline reframes the Atacama as a living laboratory for studying life at the edge of habitability, evolutionary adaptation under near-impossible water scarcity, and the thresholds at which biological colonization becomes possible.
Beneath the Atacama Desert's surface, in pebbles that have barely shifted in tens of millions of years, lies evidence that rewrites the story of Earth's driest place. A team from the University of Cologne and Scotland's SUERC Centre for the Isotope Sciences has found that the Atacama's hyperarid core has been locked in extreme dryness for at least 40 million years — roughly double the timeline scientists had previously accepted.
For decades, conventional wisdom held that the desert formed between 15 and 20 million years ago, shaped by shifting ocean currents and the rising Andes. The new research, published in Nature Communications, suggests those forces didn't create the desert — they only intensified conditions already long in place. The aridity appears to have begun during the Mid- to Late-Eocene, coinciding with global cooling that followed the Early Eocene Climate Optimum.
The evidence comes from quartz pebbles scattered across the desert's flat core. Cosmic rays striking surface minerals create rare isotopes called cosmogenic nuclides; by measuring two of these using high-sensitivity mass spectrometers in East Kilbride, Scotland, researchers determined how long the pebbles had rested undisturbed. The concentrations were extraordinarily high — consistent with surfaces essentially frozen in place for tens of millions of years. In wetter climates, rainfall constantly reshapes landscapes. In the Atacama's hyperarid core, the land barely changes at all.
This stability is reinforced by the desert itself. Hyperarid soils absorb what little rain falls, preventing runoff and erosion. Over millions of years, these soils thicken and strengthen, locking the landscape into a state of apparent hibernation: the drier it becomes, the more stable it grows, and the more stable it grows, the drier it remains.
The implications reach beyond geology. The Atacama is a natural laboratory for understanding life at the absolute limits of habitability, and pushing the record of hyperaridity back to 45 million years provides crucial context for studying how organisms adapt when water becomes almost impossibly scarce. The findings also suggest that extreme environments don't arise from a single cause, but from complex interactions between global climate, local geography, and feedback loops capable of holding a landscape unchanged across timescales that dwarf human civilization.
Beneath the surface of the Atacama Desert, in pebbles that have barely moved in tens of millions of years, lies evidence that rewrites the story of how Earth's driest place came to be. A team of researchers from the University of Cologne and Scotland's SUERC Centre for the Isotope Sciences has found that the hyperarid core of the Atacama—the region so dry it receives less than two millimeters of rain annually—has been locked in extreme dryness for at least 40 million years. That's roughly double the timeline scientists had previously accepted, and it fundamentally changes how we understand the formation of deserts and the long-term stability of Earth's most inhospitable environments.
For decades, the conventional wisdom held that the Atacama Desert took shape somewhere between 15 and 20 million years ago, a product of shifting ocean currents and the rising Andes Mountains. But the new research, published in Nature Communications, suggests those mechanisms didn't create the desert at all—they merely intensified conditions that were already in place. The extreme aridity appears to have begun during the Mid- to Late-Eocene epoch, coinciding with a period of global cooling that followed a brief warm spell called the Early Eocene Climate Optimum. Dr. Benedikt Ritter-Prinz of the University of Cologne, who led the study, described the implications plainly: the hyperarid core of the Atacama is now understood as the longest continuously dry region on Earth, a designation that forces scientists to reconsider when and how such extreme environments actually develop.
The evidence comes from an unexpected source: quartz pebbles scattered across the flat surfaces of the Atacama's core. When cosmic rays from space strike minerals at Earth's surface, they create rare isotopes called cosmogenic nuclides. By measuring two of these isotopes—21Ne and 10Be—using high-sensitivity mass spectrometers at SUERC's facility in East Kilbride, Scotland, researchers could determine how long these pebbles had been sitting undisturbed on the surface. The concentrations they found were extraordinarily high, consistent with surfaces that had remained essentially frozen in place for tens of millions of years. In wetter climates, rainfall constantly reshapes the landscape, eroding bedrock and moving sediment. But in the Atacama's hyperarid core, where water is almost nonexistent, the landscape barely changes at all. The pebbles become a kind of geological clock, recording the passage of deep time through their chemical composition.
Professor Fin Stuart of SUERC explained the significance: because the landscape has been so effectively preserved on geological timescales, the pebbles themselves become a new tool for measuring long-term climate change. They reveal not just that the desert is old, but that it has remained stable in its extreme aridity for an almost incomprehensible span of time. This stability is reinforced by a feedback loop built into the desert itself. The soils that develop in hyperarid regions have remarkable properties—they absorb what little rainfall does fall, preventing runoff and erosion. Over millions of years, these soils thicken and strengthen, further stabilizing the landscape and locking it into a state of apparent hibernation. The drier it becomes, the more stable the surface grows, and the more stable it grows, the drier it remains.
The extended timeline has implications far beyond desert geology. The Atacama serves as a natural laboratory for understanding life at the absolute limits of habitability. Water defines a habitable planet, yet vast regions of Earth exist under severe water scarcity, where both biological activity and surface processes operate at a crawl. By pushing the record of hyperaridity back to 45 million years, the study provides crucial temporal context for investigating how life adapts when water becomes almost impossibly scarce. Rare and brief increases in water availability—events that might seem insignificant in a wet climate—can leave lasting marks on the landscape and influence whether organisms can colonize and evolve in such places. The study opens new avenues for understanding evolutionary lag times, how species adapt to changing climates, and the intricate dance between geological processes and biodiversity at the edges of what life can endure.
The findings also reshape how scientists think about climate tipping points and the thresholds at which biological colonization becomes possible. They suggest that extreme environments don't simply appear in response to a single mechanism or event, but develop through complex interactions of global climate patterns, local geography, and feedback loops that can lock a landscape into a particular state for tens of millions of years. The Atacama, in its ancient stillness, becomes a window into how Earth's surface can remain fundamentally unchanged across timescales that dwarf human civilization. It is a place where time moves differently, where a pebble can rest undisturbed for longer than our species has existed, and where the story of how deserts form has only now begun to be fully told.
Citações Notáveis
The hyperarid core of the Atacama Desert was established in the Mid- to Late-Eocene, indicated by extremely low surface activity. This makes it the longest continuously dry region on Earth and forces us to reconsider how and when such extreme environments develop.— Dr. Benedikt Ritter-Prinz, University of Cologne
The extremely dry core of the Atacama Desert has less than 2 millimeters of rainfall per year, thus surface processes operate extremely slowly. Consequently, the landscape has effectively been preserved on geological timescales since the climate became hyperarid.— Professor Fin Stuart, SUERC
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that the Atacama became hyperarid 40 million years ago instead of 15 or 20 million years ago? Isn't a desert still a desert?
The difference is about causation. We thought we understood why the Atacama formed—ocean currents shifted, mountains rose, and the desert followed. But if it was already hyperarid before those things happened, then those mechanisms didn't create the desert. They just made it worse. That changes everything about how we think deserts form.
So what actually caused it, then?
That's the question the study opens up. The timing suggests global cooling after a warm period triggered it. But the mechanisms are still being worked out. What's clear is that once hyperaridity set in, the landscape locked itself into that state through feedback loops—soils developed that prevented erosion, which meant the surface stayed stable, which meant the dryness persisted. It became self-reinforcing.
How did they figure out something happened 40 million years ago? That's an impossibly long time to measure.
Cosmic rays. When they hit minerals at the surface, they create rare isotopes. The longer a pebble sits undisturbed, the more of these isotopes accumulate. By measuring them in pebbles from the Atacama's core, they could see that the surface had barely moved in tens of millions of years. In a wetter place, rain would constantly reshape things. But in the Atacama, nothing moves, so the pebbles become a clock.
And what does this tell us about life in extreme places?
It gives us a much longer timeline to understand how organisms adapt to almost no water. If the Atacama has been hyperarid for 40 million years, then any life that exists there has had 40 million years to evolve under those conditions. It also means that brief wet periods—which might seem trivial—could have outsized effects on evolution and colonization. We're only beginning to understand those relationships.
Is the Atacama unique in this way?
It's the most extreme example we know of. The longest continuously dry place on Earth. But the methods they used—measuring cosmic isotopes—could be applied to other ancient landscapes. It opens a new way of reading Earth's climate history written in stone.