The white-capped volcano that looms over Mexico City emitted a terrifying low-pitched roar on Friday and spewed roiling towers of ash and steam as it vented the pressure built up by a massive chamber of magma beneath its slopes. Authorities prepared evacuation routes, ambulances and shelters in the event of a bigger explosion.
Even a large eruption of the 5,450m cone of Popocatepetl is unlikely to do more than dump ash on one of the world’s largest metropolitan areas, but the grit could play havoc with Mexico City’s busy airport, and tens of thousands of people in the farming villages on its flanks could be forced to flee.
Popo, as it is commonly known, has put out small eruptions of ash almost daily since a round of eruptive activity began in 1994. A week ago, the eruptions started growing larger and authorities slightly elevated the alert level for people living nearby.
Before dawn on Friday, the mountain moved into what appeared to be a new level of activity, spitting out dozens of ash clouds and shot fragments of glowing rock down its slopes while frightening the residents of surrounding villages with deep roaring not heard in a decade.
People in the village of Xalitzintla said they were awakened by a window-rattling series of eruptions. Mexico’s National Disaster Prevention Center said one string of eruptions ended in the early morning, then the volcano started up again at 5:05am, with at least 12 eruptions in two hours.
“Up on the mountain, it feels incredible,” said Aaron Sanchez Ocelotl, 45, who was in his turf grass fields when the eruptions happened. “It sounds like the roaring of the sea.”
A 1 million cubic meter chamber of magma is seething about 10km beneath Popocatepetl, Roberto Quaas, director of the disaster prevention center, said at a news conference laying out emergency preparations.
Scientists have no way of predicting whether the molten rock in the chamber will be slowly released, or erupt in a powerful explosion like one on Dec. 18, 2000, that sent up a plume of red-hot rock and forced the evacuation of thousands of people who live at the volcano’s base, Quaas said.
He compared the volcano to a bottle of champagne: “You could take the cork out quickly and all the gaseous material and liquid rushes out suddenly, or it could also happen slowly.”
However, he said: “We know that this lava dome, sooner or later, will be destroyed by internal pressure.”
Scientists have detected fracturing about 5.6km down, accompanied by small earthquakes measuring about magnitude 3.4, he said.
An iconic backdrop to Mexico City’s skyline on clear days, Popocatepetl sits roughly halfway between Mexico City and the city of Puebla — meaning about 25 million people live within a 96km radius of the volcano, Quaas said.
“These are figures that obviously alarm and concern us,” he said.
Mexican President Felipe Calderon and the governors of Mexico, Puebla and Morelos states that neighbor Popocatepetl said on a live national TV broadcast that they were keeping roads open around the mountain, preparing emergency shelters and making sure residents know the latest information about a potential eruption.
“It’s our obligation to stay alert, to stay on guard, so we can keep carefully following developments and have the opportunity to respond quickly, if needed, and efficiently, to whatever might happen,” Calderon said.