POPOCATEPETAL VOLCANO, Mexico (AP) — In the predawn darkness, a team of scientists climbs the slopes of Mexico’s Popocatepetal volcano, one of the most active in the world and whose eruption could affect millions of people. Its mission: find out what’s going on beneath the crater.
For five years, a group from Mexico’s National Autonomous University has climbed the volcano with kilograms of equipment, risking data loss due to bad weather or volcanic eruptions, and used artificial intelligence to analyze the seismic data. Now, the team has created the first three-dimensional image of the interior of the 17,883-foot (5,452-meter) volcano, which tells them where magma accumulates and helps them better understand its activity, and ultimately, help authorities better respond to eruptions.
Marco Calo, professor and project leader in the Department of Volcanology at UNAM’s Geophysics Institute, invited The Associated Press to accompany the team on its final expedition to the volcano before its research is published.
underground movement
Inside an active volcano, everything is moving: rocks, magma, gases and fluids. All of this generates seismic signals.
Most of the world’s volcanoes that pose a risk to people have detailed maps of their interiors, but not Popocatepetal, despite the fact that about 25 million people live within a 62-mile (100 km) radius and that homes, schools, hospitals and five airports could be affected by eruptions.
Other scientists took some preliminary pictures 15 years ago, but they showed conflicting results and “didn’t have enough resolution to see how the volcanic edifice was building” and, above all, where the magma accumulated, Calò said.
His team increased the number of seismographs from 12 provided by Mexico’s National Disaster Prevention Center to 22 to cover the entire perimeter of the volcano. Although only three people can warn of an emergency, much more is needed to understand what lies behind those emergencies.
The devices measure vibrations in the ground 100 times per second and generate data that Karina Bernal, 33, a doctoral student and researcher on the project, processes to adapt algorithms developed for other volcanoes using artificial intelligence.
“I taught the machine about the different types of tremors that occur in El Popo” and they were able to catalog different types of seismic signals, she said.
Little by little, scientists began to guess what kinds of materials were where, in what conditions, at what temperatures, and at what depths. Later they were able to map it.
The result is more complex than most volcano diagrams seen in school, with a main vent connecting a chamber of magma to the surface.
This first three-dimensional cross-sectional image goes 11 miles (18 km) below the crater and shows what appear to be different pools of magma at different depths, with rock or other material between them, and more numerous to the southeast of the crater.
A “majestic” giant
Popocatépetl emerged in its current form more than 20,000 years ago in the crater of another volcano and has been active since 1994, spewing plumes of smoke, gas and ash more or less daily. The activity periodically forms a dome over the main vent, which eventually collapses, causing an explosion. The last one was in 2023.
Calo, a 46-year-old Sicilian, speaks passionately about El Popo, the way Mexicans treat volcanoes with trivia.
He explains that its elevation may have changed due to eruptions and how Popocatepetal had its own “little Pompeii” in the first century when a nearby village, Tetimpa, was buried in ash. In the early 20th century, it was human actions – using dynamite to extract sulfur from the crater – that triggered the eruption. And although El Popo emits more greenhouse gases than almost any other volcano, its emissions are still a small fraction of those generated by humans in nearby Mexico City.
For years Calò studied volcanic activity from his computer, but trying to “understand how it works without touching anything” grew a sense of frustration, he said.
That changed with Popocatépetl, a volcano he describes as “majestic.”
Touch the volcano
After hours of walking along the side of the volcano, Calò’s team sets up camp in a pine grove at an altitude of about 12,500 feet, a place apparently safe from pyroclastic eruptions, as the trees have managed to grow to a significant height.
A little higher up the hill, trees and scrub give way to ash and sediment.
They must cross a wave made up of a mixture of rock and ash that becomes dangerously muddy during the rainy season, washing away everything in its path. Now, the dry clearing offers a spectacular view: to the east Pico de Orizaba—Mexico’s tallest volcano and mountain—and the dormant volcano La Malinche; To the north, Iztaccíhuatl, a dormant volcanic peak known as the “Sleeping Woman”.
The sounds of Popocatépetl seem to multiply at night with echoes. A rocket-like explosion may seem to come from one direction, but the plume of smoke from the crater obscures the true source.
Karina Rodríguez, a 26-year-old master’s student on the team, said you can hear small tremors in the earth or rain like ash when the volcano is more active. On dark nights, the rim of the crater glows orange.
Natural Laboratory
Having direct knowledge of volcanoes provides a more objective sense of the limits of their analysis, Black said.
He said, ‘Here is a natural laboratory. It is “very important to be able to understand and give residents detailed, reliable information about what is happening inside the volcano.”
At 13,780 feet (4,200 m), their backpacks filled with computers, gas, batteries and equipment to analyze water begin to weigh more and their pace slows.
Grey, dark and hot, dominate the landscape here.
At the seismographic station, the team digs out the equipment and pretends it’s still working. They download its data and restore it again.
A “volcanic bomb,” a rock a yard and a half in diameter and weighing a ton, marks the path and signifies the beginning of an eruption. This is why the top area of the volcano is restricted, although not everyone notices. In 2022, a man died after being hit by a cliff 300 yards (meters) from the crater.
A bottle of tequila near a rocky hollow known as El Popo’s Belly Button hints at some of the traditions surrounding the volcano, including an annual pilgrimage that some consider a point of connection with the underworld.
Drive to continue climbing
While digging one of the last seismic stations, Calò’s face fell. The latest registration data is from months ago. Battery died. Sometimes rats chew through machine wires or explosions cause more serious damage.
The project has provided some certainty and if repeated will allow analysis of changes that will ultimately help authorities make better decisions when eruptions occur.
But Calò says, as is always the case with science, it has also generated new questions that they will have to try to address, such as why earthquakes occur more frequently towards the southeast – where there is more accumulated magma – and what the effect might be.
It was the last expedition before their years of work to publish a map of the volcano’s interior. Watching the inner workings of a volcano in 3D on a computer screen makes all the effort worthwhile.
“It inspires you to start another project and keep climbing,” said Rodriguez, a master’s student.
