Beneath the snow-capped peaks and drifting ash clouds of Popocatépetl, one of Mexico’s tallest and most active volcanoes, lies a hidden world that until recently was known only by tremors and instinct. For centuries, only the surface — the smoke, the eruptions, the rumbling of the earth — hinted at what churned within. Today, thanks to the painstaking work of scientists from the National Autonomous University of Mexico (UNAM), we have our first three-dimensional glimpse inside this majestic and enigmatic giant.

Popocatépetl, affectionately called “El Popo,” dominates the landscape southeast of Mexico City, looming over valleys where some 25 million residents live within 100 kilometres and could be affected by a major eruption. Despite its prominence, researchers lacked a high-resolution image of its interior — a gap that limited understanding of how magma moves beneath its surface.

Over five years, a dedicated team of geophysicists and volcanologists ascended the volcano’s slopes before dawn, hauling heavy seismic equipment and enduring harsh weather and volcanic activity. They carefully placed 22 seismographs around the edifice, more than the dozen previously used, measuring ground vibrations hundreds of times per second. That seismic data — rich but complex — was then interpreted using artificial intelligence to distinguish between different types of underground tremors and infer the materials, temperatures, and states of rock and magma deep below the crater.

The result is a first-of-its-kind 3D cross-sectional map that extends roughly 11 miles (18 km) beneath the crater, revealing a more intricate structure than the simple magma chamber often illustrated in textbooks. Instead of a single reservoir, scientists found multiple magma pools at varying depths, with greater concentrations toward the volcano’s southeast side. These magma bodies — pockets of molten rock waiting, shifting, and occasionally rising — are separated by layers of solid rock and other materials, helping explain how tremors propagate and how pressure might build before an eruption.

Making this underground landscape visible is not only a scientific milestone but a practical one. A detailed image of where magma accumulates and how it moves can improve eruption forecasts and give authorities better information when making safety decisions for nearby communities. El Popo’s activity is ongoing; it has been erupting intermittently since 1994, producing ash, gas, and lava domes that can collapse and trigger further outbreaks.

The work has been as much a human journey as a scientific one. Researchers spoke of the volcano as a “natural laboratory,” teaching them through direct observation and shared experience — from the first camp set at 12 500 feet in pine groves to the ash-strewn upper flanks where sediment and rock give way to stark volcanic terrain. These field challenges, including damaged equipment and the constant risk of explosions, only deepen the significance of the images they have produced.

As the detailed 3D mapping is published and shared with the broader scientific community, it opens new questions as well as answers. Why do tremors occur more frequently on one flank? How do different magma pools interact over time? And how might future eruptions begin deep beneath the surface? These are the mysteries that scientists will continue to explore, guided now by the clearer — if still awe-inspiring — vision of what lies beneath Popocatépetl’s surface.

In the end, the interior of a volcano is more than molten rock and seismic waves; it is a reminder of Earth’s restless heart — powerful, inscrutable, and profoundly alive.

AI Image Disclaimer “Visuals are created with AI tools and are intended for conceptual depiction only.”

Sources • Associated Press via multiple outlets • Yahoo News • UNB News (science coverage)