🧲 Magnetism proves it: The Andes are much older than previously thought

A new geological study sets the record straight on the formation of the Andes mountain range.

Research published in Earth and Planetary Physics indicates that the main episodes of collision between tectonic plates likely occurred earlier than models suggested, thereby altering our understanding of the evolution of this imposing mountain chain.


To reach this conclusion, scientists examined ancient volcanic rocks located in northern Colombia. These formations, dating from the Late Miocene and 12 to 6 million years old, constitute a record of the forces that shaped the region.

The team used an analysis of the "magnetic fabric" (see below) to reconstruct this past. This method examines the orientation of magnetic minerals in the rocks, which makes it possible to distinguish structures of volcanic origin from later deformations caused by plate movements.

The results are clear: many rocks retain their original magnetic fabric, linked to magma movement or volcanic flows. Consequently, tectonic alteration during the Late Miocene appears weak, indicating that the intense phase of continental collision had essentially ended before this period.

This chronological adjustment refines current models on the genesis of the Andes. It allows for a better understanding of how plate interactions sculpted the landscapes and, at the same time, demonstrates the value of magnetic methods in volcanic environments for tracing geological history.


This approach could find applications in other mountainous regions. It paves the way for comparable work aimed at understanding tectonic processes on a global scale.

Magnetic fabric analysis

This geophysical technique is based on studying the alignment of magnetic minerals in rocks. When volcanic rocks form, their minerals align according to the conditions of the moment, such as the direction of magma flow. By scrutinizing this orientation, researchers can determine whether the rock was deformed by tectonic forces after its solidification.

Magnetic fabric acts like a fingerprint left by geological events. A uniform and consistent orientation generally reflects the initial volcanic process. Conversely, distortions or reorientations signal a later modification, often due to plate movements or continental collisions.

This method is particularly effective in volcanic areas, where rocks cool quickly, thus preserving precise snapshots. It helps to date deformation phases and better understand the sequence of tectonic events, offering a complementary tool to other geological techniques.

Concretely, the analysis requires carefully collected samples measured in the laboratory. The collected data contributes to reconstructing past histories, like that of the formation of the Andes, by providing clues about the chronology and intensity of the forces involved.