What’s inside Mexico’s Popocatépetl volcano? Scientists obtain first 3D images

POPOCATÉPETL VOLCANO, Mexico (AP) — In the predawn darkness, a team of scientists climbs the slope of POPOCATÉPETL VOLCANO of mexico Popocatépetl volcano is one of the most active volcanoes in the world and its eruption could affect millions of people. Its mission: To understand what’s happening underneath the crater.

A group from the National Autonomous University of Mexico climbed to the top for five years. volcano with kilos of equipment, facing the risk of data loss due to bad weather conditions or volcanic eruption and used artificial intelligence Analyzing seismic data. The team has now created the first three-dimensional image of the interior of the 17,883-foot (5,452-meter) volcano; This tells them where magma is accumulating and will help them better understand their activities, ultimately helping authorities better respond to eruptions.

Marco Calò, professor and project leader in the vulcanology department at UNAM’s Institute of Geophysics, invited The Associated Press to accompany the team on the final expedition before the publication of his research on the volcano.

underground movement

Inside an active volcano, everything is in motion: rocks, magma, gas and groundwater. They all produce seismic signals.

Detailed maps of the interiors of many of the world’s volcanoes that pose a risk to humans already exist, but these maps are not available. Popocatepetl, That’s despite the fact that about 25 million people live within a 62-mile (100-kilometer) radius and that homes, schools, hospitals and five airports could be affected by an explosion.

Calò said other scientists took some early images 15 years ago, but they showed contradictory results and did not have enough resolution to see “how the volcanic structure was built” and where magma accumulated in the first place.

His team increased the number of seismographs from 12 provided by Mexico’s National Disaster Mitigation Center to 22 to cover the entire perimeter of the volcano. Although only three people can raise the alarm about an emergency, many more are needed to understand what is behind these emergencies.

The devices measure vibrations in the ground 100 times per second, said Karina Bernal, 33, a PhD student and researcher on the project. artificial intelligence adapting algorithms developed for other volcanoes.

“I taught the machine about the different types of tremors at El Popo,” so they could catalog the different types of seismic signals, he said.

Scientists gradually began to deduce what kind of material was found where, in what condition, at what temperature and at what depth. They later managed to extract the map.

The result is much more complex than the volcano drawings most seen in school, with a main vent connecting the magma chamber to the surface.

This first three-dimensional cross-sectional view goes 11 miles (18 kilometers) below the crater and shows what appear to be various magma pools of varying depths, interspersed with rock or other material, toward the southeast of the crater.

A “majestic” giant

Popocatépetl emerged in its current form in the crater of other volcanoes more than 20,000 years ago and has been active since 1994; It spews smoke, gas and ash more or less every day. The activity periodically creates a dome over the main vent, which eventually collapses, causing an explosion. The last one was in 2023.

Calò, a 46-year-old Sicilian, talks passionately and trivia about El Popo, which Mexicans call the volcano.

He explains that its height can change due to eruptions, and describes how Popocatépetl had its own “little Pompeii” in the first century, when Tetimpa, a village on its flanks, was buried in ash. In the early 20th century, it was human actions using dynamite to extract sulfur from the crater that caused an eruption. Although El Popo emits more greenhouse gases than almost any other volcano, its emissions are still a small fraction of those produced by humans near Mexico City.

Calò has studied volcanic activity on his computer for years, but said trying to “figure out how something works without touching it” was frustrating.

This changed with Popocatépetl, a volcano he describes as “majestic.”

touching a volcano

After walking for hours on the volcano’s flank, Calò’s team sets up camp in a pine grove at about 12,500 feet, a safe spot against pyroclastic eruptions because the trees have managed to grow to a significant height.

Further up the mountain, trees and shrubs give way to ash and sediment.

During the rainy season, they must pass through a lahar, a mixture of rock and ash that turns into a dangerous mudflow that washes away everything in its path. Now, the dry clearing offers a spectacular view: to the east, Pico de Orizaba, Mexico’s highest volcano and mountain, and La Malinche, the inactive volcano; to the north, Iztaccíhuatl, a dormant volcanic peak known as the “sleeping woman.”

The sounds of Popocatépetl seem to amplify with echoes at night. A rocket-like explosion may sound like it’s coming from a single direction, but the smoke coming out of the crater belies the true source.

Karina Rodríguez, a 26-year-old graduate student on the team, said that when the volcano is more active, small tremors in the ground and even ash falling like rain can be heard. On dark nights, the rim of the crater glows orange.

A natural laboratory

Having direct knowledge of the volcano gives a much more objective idea of ​​the limits of analysis, Calò said.

“We have a natural laboratory here,” he said. “It is very important to be able to understand what is happening inside the volcano and provide detailed, reliable information to residents.”

At 13,780 feet (4,200 meters), backpacks filled with computers, gas analysis equipment, batteries and water begin to weigh more and their speed slows.

Dark and hot ash dominates the landscape here.

The team excavates equipment at a seismography station and celebrates that the equipment is still working. They download their data and re-embed it.

The “volcanic bomb”, a rock five feet in diameter and weighing tons, points the way and gives an idea of ​​what the beginning of an eruption might mean. That’s why the upper part of the volcano is restricted, although not everyone cares. In 2022, one person died after being struck by a rock about 1,000 feet (meters) from the crater.

A bottle of tequila near a rocky alcove known as El Popo’s belly button points to some of the traditions surrounding the volcano, including the annual pilgrimage to what some see as a connection point with the underworld.

The urge to keep climbing

Calò’s face falls as he digs into one of the last seismic stations. The last recorded data is from months ago. Battery died. Sometimes mice chew on the machines’ cables, or an explosion causes more serious damage.

The project has reached some certainty and, if repeated, will allow analysis of changes that will help authorities make better decisions when explosions occur.

But Calò says that, as always in science, it also raises new questions that they should try to address, such as why tremors are more frequent on the southeast side (where more magma accumulates) and what consequences that might have.

This was the last expedition before the publication of years of work to map the interior of the volcano. Watching the volcano’s internal movement in 3D on a computer screen is worth all the effort.

“That’s what pushes you to start another project and keep climbing,” said graduate student Rodríguez.