A new study of volcanic rocks in Colombia suggests Central and South America collided earlier than scientists previously thought, offering new clues about the tectonic forces that helped shape the Americas.
The research, published in Earth and Planetary Physics, found that the strongest phases of collision-related deformation had largely ended before about 10 million years ago. The findings provide a new timeline for the tectonic forces that shaped northern South America.
Victor A. Piedrahita led the study, with J. Li serving as corresponding author. An international team of geoscientists also contributed to the research.
Volcanic rocks preserve magnetic clues
Researchers examined rocks from the Combia Volcanic Province in central Colombia. The rocks formed during the late Miocene, about 12 million to 6 million years ago, when the South American Plate was interacting with the continental portion of Central America.
Ancient rocks can preserve evidence of tectonic events for millions of years. A recent study of rocks on the Greek island of Crete similarly reconstructed a tectonic history stretching back about 130 million years.
The team used magnetic fabric analysis to study the orientation of magnetic minerals within the Colombian rocks. The method can help scientists determine whether a rock’s internal structure formed during volcanic activity or was later altered by tectonic forces.
Geological map of the study area with the three studied stratigraphic sections of the Combia Volcanic Province. pic.twitter.com/WOnX6lRHdd
— Tom Marvolo Riddle (@tom_riddle2025) September 9, 2026
“Volcanic rocks can preserve a remarkably detailed record of geological processes,” Piedrahita said. “Their magnetic fabrics help us determine whether deformation occurred before, during, or after the rocks were emplaced.”
Many of the rocks retained their original magnetic fabrics. Researchers linked these patterns to processes such as magma movement and volcanic debris flows.
If strong tectonic deformation had occurred later, it likely would have altered those patterns. Instead, the rocks showed little evidence of widespread deformation during the late Miocene. Some sites contained signs of tectonic changes, but they were relatively weak and geographically limited.
Major deformation happened earlier
The results suggest that the strongest crustal shortening in the Northern Andes had already occurred before the late Miocene. “Our data indicate that the most significant collisional events between Central and South America occurred earlier than we previously thought, mainly during the Oligocene-middle Miocene,” Piedrahita and Li said. “By the time these volcanic rocks formed, tectonic deformation had become weaker and more localized.”
Such plate interactions can transform landscapes over millions of years. The geological history of Greece offers another example of how subduction, collision and faulting can build mountains and reshape entire regions.
New timeline for the Northern Andes
The findings could help scientists refine models of how the Northern Andes formed and changed over millions of years. They could also improve understanding of how interactions between tectonic plates shaped the geological development of the Americas.
The study also highlights the value of magnetic fabric analysis. Magnetic patterns preserved in volcanic rocks can provide evidence of ancient tectonic activity, especially in regions where other signs of deformation are difficult to identify.
Similar geological processes continue to shape volcanic regions today. Santorini’s volcanic landscape, for example, developed through repeated volcanic activity linked to tectonic plate movement beneath the eastern Mediterranean.
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