Airports temporarily closed, flights canceled, classes suspended in nearby schools.
The Popocatepetl volcano in Mexico has been attracting all eyes for several days for the impressive images it offers in the form of ejections of incandescent material and explosions, as well as large exhalations of smoke and ash that reached nearby towns and made the authorities activate the emergency protocols.
Popocatepetl is fully active. However, this is not new since the “smoking mountain” – in the Nahuatl language – restarted its activity at the end of 1994. In fact, this is the sixth time since 2000 that the yellow phase 3 precautionary alert has been issued and is still in effect today.
For this reason, scientists are calling for calm and to follow official recommendations based on the 24-hour monitoring of the volcano also known as “el Popo” or “Don Goyo”.
“The current behavior of Popocatepetl is slightly more intense than it has been on previous occasions, but nothing disproportionately different. It is within what we have observed since it was activated,” emphasizes Juan Manuel Espíndola, a researcher at the Geophysics Institute of the National Autonomous University of Mexico (UNAM).
Based on previous experiences, the expert predicts that the volcano’s current activity will continue in the form of ash expulsions and sporadic explosions, but that they could progressively decrease in intensity and “decline” over the next few weeks.
“It’s like the equivalent of a sick person who is in intensive care and is being monitored. He may remain stable, move into a dangerous phase, or be definitively discharged,” he compared.
“Now we are in the observation phase and there is no information that the volcano is moving to a more dangerous phase. There is no evidence of that,” the expert emphasized.
“Don Goyo” has been offering impressive images like this one for several days.
Together with Espíndola, BBC Mundo tells you seven facts about Popocatépetl, one of the most active volcanoes in Mexico and with which the inhabitants of this area have lived for thousands of years.
- One of the most dangerous in the world
Popocatepetl is considered one of the most dangerous volcanoes in the world due to its proximity to densely populated areas.
Popo” is located in central Mexico, between the states of Morelos, Puebla and Estado de Mexico, and less than 100 km from the capital, Mexico City.
Therefore, it is estimated that a large eruption could affect some 25 million people living within a 100 km radius around the volcano, where there are schools, hospitals and airports. The town of Santiago Xalitzintla is the closest, being only 12 km from the crater.
Popocatepetl is also part of the so-called Pacific Ring of Fire, which borders the Pacific Ocean with a length of about 40,000 km.
This ring is considered the most extensive and active seismic region, where 75% of the world’s volcanoes are concentrated and where most of the earthquakes have their epicenter.
This map shows the danger zones for pyroclastic, mud and lava flows in the areas surrounding the volcano.
- Formed in the crater of other volcanoes that collapsed.
In fact, Popocatépetl is not the only volcano that is part of the so-called Sierra Nevada of Mexico.
Next to it there are other great volcanoes such as Iztaccihuatl, also known as “The Sleeping Woman” and with which, according to a popular legend, she swore eternal love.
What is proven is that, in the more than half a million years it has been active, it has presented several stages of growth that formed at least three other volcanoes before it.
These were destroyed by huge eruptions: Nexpayantla more than 400,000 years ago, Ventorrillo about 23,000 years ago, and Fraile about 14,500 years ago. The modern cone of Popocatepetl is formed on the remains of these volcanoes.
- “Not sleeping” since 1994
Although many believe that Popocatepetl has erupted now, the truth is that the images it leaves these days are only an episode within a period or eruptive event that began at the end of 1994.
Before that, “don Goyo” had been “dormant” for about 70 years since its last activity in the 1920s.
This has led some experts to point to a sort of behavioral pattern in which the volcano could reactivate approximately every seven decades, then be active for a while and go back to sleep.
According to Espíndola, “the problem is that the life of volcanoes is very long and this needs to be studied in greater detail over a long period of time to see if this pattern holds true”.
“And, in the case of volcanoes, this behavior is vague, so the current data does not allow us to reach with certainty that conclusion that it will be activated every 70 years,” he disagrees.
Experts rule out that there is currently evidence pointing to an increase in danger due to the volcano’s activity.
- Stratovolcano
For all these reasons, “Popo” is classified as a stratovolcano. That is, it is composed of different layers that have been formed in each of the many phases of its long eruptive life over thousands of years.
“Those layers are of different types and could have been formed by lava flows, pyroclastic material…”, explains Espíndola.
“This is how the volcanic edifice is formed and that is why the stratovolcanoes are so tall and large: because they have been built in different stages of massive emissions,” he adds.
With a crater 900 m in diameter and an altitude of 5,452 m above sea level, Popocatépetl is the highest volcano in Mexico after the peak of Orizaba or Citlaltépetl.
Residents of Santiago Xalitzintla received on Tuesday a protection kit against ash fall from “Popo”.
- Among the top 5 gas emitters in the world
A 2013 UNAM investigation placed Popocatepetl among the five volcanoes in the world that emit the most gases into the atmosphere.
That study estimated that 30 megatons of gases were expelled by “don Goyo” between 1994 and 2008. Its most important emissions are sulfur dioxide and carbon dioxide, as well as water vapor.
Far from what it may seem at first sight, experts assure that the efficient expulsion of gases helps to avoid other more serious problems and that their ventilation contributes in some way to “clean” or free the internal conduits of the volcano.
“That is so as long as there is no more material coming from inside the volcano, because that would be noticed in a more intense seismicity,” Espíndola qualifies. “But so far nothing like that has been noticed.”
- An enigma in its interior
The truth is that the interior of Popocatépetl, as with all volcanoes, is an enigma.
Its large size and the difficulties in accessing it because it is active mean that its internal structure is little known, since the existing models for monitoring it are based, for example, on factors such as seismicity.
Espíndola explains that the guide we have to know something more indirectly about this subject is thanks to the location of earthquakes, which allows us to guess the area where the volcanic conduit is.
“But there is no volcano where you can have exact information. Even in the most studied ones, we only have some data about the conduits of the volcanic building, but the magma comes from many km deep under the earth… so there is no direct information, but the inference that provides us with some data such as earthquakes”, he assures.
Thousands of military personnel were deployed in case it was necessary to evacuate nearby areas, some of which were covered with ash.
- The most watched in Mexico
For all these reasons, it is not surprising that Popocatépetl is the most watched volcano in Mexico, with a team of 13 scientists from different specialties monitoring its activity day and night.
Currently, a group of cameras, sonic sensors, seismic and meteorological stations help monitor its activity around the clock by sending data to a control center located in southern Mexico City.
“This committee involves specialists who study different areas such as seismicity, emissions, geochemistry… and all that information is provided to the authorities, who have taken the issue seriously and are periodically informing the population of what they have to do,” says Espíndola.
“And that’s the important thing: to stay informed,” he concludes.
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