A massive volcanic eruption that occurred in northern Chile approximately 21.9 million years ago blanketed an entire landscape in a cataclysmic event reminiscent of Pompeii, preserving ancient terrain that reveals the Andes mountains rose slowly. According to a study published by researchers, the prehistoric eruption buried valleys and hills under layers of volcanic rock reaching up to 3,300 feet thick, creating a natural time capsule.
The Cardones Ignimbrite Eruption and Its Scale
The devastation stemmed from the ancient Lauca Caldera in the far north of Chile, a massive depression formed when the earth’s crust collapsed during an explosive volcanic episode. According to geologists, this event produced the Cardones ignimbrite, which stands as the largest deposit among a series of explosive volcanic markers in the region. Earth scientist Byron Adams of University College London, who led the research team, likened the event to the historic destruction of Pompeii. As Adams noted in an interview with Earth.com, hot mixtures of volcanic ash, rock fragments, and gas swept across the entire terrain on a vastly larger scale than the Roman disaster. The resulting volcanic rock deposits total more than 300 cubic miles, or 1,260 cubic kilometers, leaving an upper surface that originally tilted gently to the west at an angle of roughly 1.5 degrees.
Reconstructing Ancient Tectonic Uplift Rates
Because volcanic debris thins as it travels away from its source vent, the landscape buried beneath it could not have featured slopes steeper than the surface of the deposit itself; otherwise, towering peaks would have pierced through the blanket. This physical constraint allowed the research team—which included Frances Cooper of the University of Bristol, Clementine Walsh, and Katharine Cashman of the University of Oregon—to utilize a specialized computer model. The simulation replicated river networks carving into a landblock measuring approximately 14 miles on each side. By running the model 560 times with varying combinations of rock uplift speeds and erosion resistance, the scientists determined that the underlying landmass rose no faster than roughly an inch every century.
Comparative Tectonic Rates and Mountain Growth
The calculated uplift rate of an inch per century stands in sharp contrast to modern rapidly eroding mountain belts. In Taiwan, for instance, tectonic rock uplift and surface erosion proceed at roughly 16 to 24 inches per century. While an inch a century appears slow on a human timescale, Adams explained that the steady accumulation drives long-term geological transformation. Mountains do not simply rise like elevators; instead, as tectonic forces push rock upward, surface erosion simultaneously strips material away. When erosion matches the pace of tectonic uplift, the actual surface elevation of a mountain range remains remarkably stable over millions of years, according to the researchers’ findings.
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