A volcanic event that occurred 22 million years ago has provided scientists with a detailed glimpse into the early development of the Andes mountain range. Originating from the Lauca Caldera in present-day northern Chile, the eruption deposited a thick layer of ignimbrite—a rock formed from pyroclastic flows consisting of hot ash, gas, and rock fragments. This process is analogous to the eruption of Mount Vesuvius that buried Pompeii in A.D. 79, though on a significantly larger scale.
According to a study published on September 11 in the journal Science Advances, the volcanic blanket preserved the topography of the region as it existed millions of years ago. The data indicates that the landscape prior to the eruption consisted of rolling foothills rather than steep, jagged peaks.
“Pompeii shows how volcanic eruptions can freeze a moment in human history,” said Byron Adams, a geomorphologist at University College London. “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.”
While researchers cannot excavate the buried terrain, they analyzed the shape of the ignimbrite deposit and applied knowledge of fluvial erosion patterns to reconstruct the original slope. Adams and his team determined the initial slope of the volcanic flow was approximately 1.5 degrees. By calculating the rate of landscape erosion, the team estimated the speed at which the crust was uplifting as the Nazca Plate subducted beneath the South American continental plate.
The analysis revealed that the crustal uplift rate before the eruption did not exceed 0.16 miles (0.26 kilometers) per million years, characterizing the process as remarkably sluggish. These results align with previous research utilizing mineral formation in rocks to date crustal movement.
The findings contribute to a long-standing geological debate regarding the timeline of the Andes’ rise. Adams noted that while some theories suggest the mountains remained low for tens of millions of years before rising rapidly in the last six to 10 million years, this study supports the alternative view of gradual, consistent growth.
“Our findings, which cover a large part of the middle of that history, support the slow but steady hypothesis,” Adams stated. Researchers suggest this analytical method could be applied to other major mountain ranges globally to further understand orogenic processes.
The Pompeii comparison is spot on. It’s wild that a catastrophic eruption can actually preserve history instead of destroying it.
Twenty-two million years ago, the area was just rolling foothills. Hard to imagine the scale of that uplift since then.
Does this mean we could apply this method to the Himalayas? That would be groundbreaking for understanding global tectonics.
I always thought the Andes rose quickly. This slow and steady theory really challenges what I learned in school.
Fascinating how they used erosion patterns to reconstruct the ancient landscape. Nature’s own time capsule!