The Americas experienced their own Vesuvius-style volcanic eruption 21.9 million years ago, devastating a portion of Chile worse than Pompeii.
A new study in Science Advances highlights the work of University College London Earth Sciences researchers analyzing a mountain of ancient volcanic rock covering an area six times the size of the Chilean capital, Santiago.
The Lauca Caldera erupted to cover the area in molten ignimbrite rock up to a kilometer deep. That ancient volcanic hellscape buried the region’s terrain but, ironically, preserved it from typical erosion, providing important clues for modern climate researchers.
Modeling Volcanic Activity
“This landscape was buried by a giant volcanic eruption – a little like Pompeii, but on a vastly larger scale,” said lead author Dr Byron Adams, based at UCL Earth Sciences. “Instead of covering a town, hot mixtures of volcanic ash, rock fragments, and gas swept across an entire landscape, engulfing the terrain beneath them.”
Using detailed computer models, the UCL Earth Sciences team produced hundreds of possible landscapes to explore what the region may have once looked like. Detailed data on how rivers cut through landscapes to form mountain ranges informed predictions of what lies beneath the massive ignimbrite deposits. The researchers concluded that a low-relief landscape, such as foothills, most likely existed there at the time.
“Pompeii shows how volcanic eruptions can freeze a moment in human history. This study shows that much larger eruptions can also freeze moments in Earth history, burying whole landscapes beneath volcanic deposits and preserving clues to how mountains were being built before the eruption,” Adams said.
“We cannot dig down to see the buried landscape, but we can use the shape of the volcanic blanket and what we know about how rivers shape mountains to infer what is hidden beneath it.”
The Volcanic Andes
The findings indicate that this portion of the Andes, the world’s longest continental mountain range, rose very slowly, by only about an inch per century. At a faster rate, the landscape beneath the volcanic deposits would not fit the researchers’ models, and the slopes would have been much steeper.
The work provides new evidence in a longstanding debate among geologists over whether the Andes rose rapidly in the last few million years or developed more gradually over a much longer period. Earlier mineral analyses of the Andean range produced similar estimates based on records of temperature changes preserved in the rocks as they cooled while moving toward the planet’s surface.
“This approach gives us a new way to look back at Earth’s history. Current methods to estimate the speed at which mountains build look at chemical ‘clocks’ in the rock, but these are limited to specific moments in time. Our method can estimate rock uplift over a much longer period,” Dr. Adams said. “In this case, we estimate it would have taken millions of years to produce the subdued landscape we infer prior to the eruption.”
Other mountain ranges around the world, such as the Himalayas, can move even faster, rising several millimeters or even centimeters each year.
Climate Implications
While the team’s work covers only the middle of the Andes’ history, it still provides interesting support for the slow-movement hypothesis. For years, researchers have worked to understand how the Andes developed, as they strongly influence global and regional climate.
By better understanding the Andes, climatologists have a more complete data set to piece together the complex problem of global climate change.
“What’s particularly exciting about this study is that it gives us a new way of piecing together that history, concluded co-author Dr Frances Cooper, also based at UCL Earth Sciences. “The same approach could be applied to volcanic deposits elsewhere in the world, helping us reconstruct landscapes buried for millions of years.”
The paper, “Landscapes Buried Beneath Large-Volume Ignimbrites Reveal Preeruptive Uplift Rates,” appeared in Science Advances on September 11, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.