UCSD - University of California - San Diego

06/16/2026 | Press release | Distributed by Public on 06/16/2026 15:41

How Mountains are Really Made

Published Date

June 16, 2026

Article Content

Scientists have discovered that the southern Andes Mountains don't rise slowly and steadily as previously thought. Instead, the range builds itself in short, powerful "pulses" every few million years.

A research team led by Tomas Capaldi, a geoscientist at UC San Diego's Scripps Institution of Oceanography, reports that it has identified a new mechanism explaining how mountain belts can expand far into continents and why these pulses repeat over time. Their study appeared June 9, 2026 in the journal Nature Communications.

"Mountain belts leave behind measurable "vital signs" in their volcanic, structural, and sedimentary records. In this study, we tune into the heartbeat of the Andes," said Capaldi.

Scripps geoscientist Tomas Capaldi points to the surface rupture fault of the 1944 San Juan, Argentina earthquake.

By looking at volcanic histories, rock records, and the sediments that accumulate in nearby basins, the researchers uncovered the importance of the development and progressive shift of volcanism on mountain building. The spatial migration of volcanism toward the continental interior weakens the Earth's crust and sets off rapid episodes of deformation.

"We find that when volcanic activity shifts inland, it weakens the Earth's crust and triggers rapid episodes of mountain building," said Capaldi. "This reveals a repeating pattern behind the rise of the Andes and shows how deep-Earth processes can reorganize quickly enough to reshape landscapes, Earth resources, and seismic hazards across South America."

Tracking how volcanoes shift over time may even give clues about future mountain-building episodes and associated earthquake risks.

This work was co-authored by Brian Horton (University of Texas at Austin), Chelsea Mackaman-Lofland (University of Tennessee, Knoxville), Gustavo Ortiz (Universidad Nacional San Juan), and Facundo Fuentes (Independent consultant), and was supported by the National Science Foundation.

Read the study in Nature Communications: "Inboard advance of arc magmatism regulates mountain building in the Andes."

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