On Monday night, March 18, at about 9:38pm (2138 hours), the volcano Popocatepetl produced a violent explosion which rattled windows and doors in towns and villages miles away, and shooting balls of fiery rock arcing into the air to crash down onto the slopes of the mountain, as well as sending up a towering plume of ash 2.5 miles high.

Above is a news report showing footage of the explosion captured on a security camera, as well as additional footage containing the view from nearby towns and reactions from residents.

This blog post from almost exactly three years ago describes a 2016 eruption of Popocatepetl, as well as the legend of the warrior Popocatepetl and his beloved Ixtaccihuatl, and possible celestial aspects of that legend (which I well remember learning at the age of 14 or 15 in my high school Spanish class, along with the pronunciation of the Nahuatl names Popocatepetl and Ixtaccihuatl, which are quite beautiful and delightful to say once you learn how to pronounce them).

As that post explains, Ixtaccihuatl is thought to be extinct, while Popocatepetl was dormant for decades, before reawakening in 1991 in a series of eruptions which continue to this day.

Both mountains are categorized as stratovolcanoes, explained here in a post from Oregon State University, and both Popocatepetl and Ixtaccihuatl rise to elevations over 17,000 feet above sea level. As that post explains, stratovolcanoes can be extremely dangerous, because they are like plugs over a pressure cooker, which can suddenly vent steam and gas, or even explode in a violent "Plinian eruption" such as the eruption of Vesuvius (also a stratovolcano) in AD 79, discussed at length in this previous post.

The term "Plinian" for a catastrophic eruption comes in fact from the accomplished Roman lawyer and public figure Pliny the Younger, who wrote two letters to the historian Tacitus about twenty-five years after the event, describing the devastating eruption of Vesuvius that year.

This article, by lead investigator Dr. Chiara Maria Petrone, discusses the risks posed by Popocatepetl, which is ranked most dangerous of all volcanoes in Mexico and North America by "explosive activity and population threat." As that article explains, Popocatepetl and Ixtaccihuatl are located near one of the most densely-populated cities in the world, Mexico City, along with other surrounding towns and villages, some of them much closer to the slopes of the Popo volcano.

As the article explains, there are approximately 30 million people living within a 70 kilometer (43.5 mile) radius of Popocatepetl. To put that into perspective, New York City is the most populous city in the united states, with a population of about 8.6 million (Los Angeles is second, with a population of about 4 million). The entire state of Texas, the second-most populous state in the united states, has an estimated population of approximately 28 million. The entire state of Florida, the third most-populous, has a population of approximately 21.3 million and the entire state of New York, the fourth most-populous, has a population of approximately 19.5 million.

In other words, the population living within 43-and-a-half miles of Popocatepetl is greater than the entire population of any single u.s. state other than California (which has an estimated population of about 39.5 million), and the population living that close to the volcano is nearly as large as the population of the entire state of California!

Below is a screen-shot of a topo map of the region of Mexico City, showing the volcanoes Popocatepetl and Ixtaccihuatl, as well as surrounding towns, some of them much closer to the slopes of the mountains:

mexico city greater area popocatepetl 15 mi radius circle.png

In the above map, I have drawn a blue circle centered on the peak of the volcano Popocatepetl. This circle is 15 miles in radius (or 30 miles in diameter), or about 24 kilometers in all directions from the central cone of the volcano. There is also a smaller red circle inside the larger blue circle: this small red circle is only 2.5 miles in radius or 5 miles in diameter. The horizontal line running across the middle of the circle is blue for 10 miles on either side of the central cone of the volcano, then red for the final five miles of each side.

As this rather frightening scholarly article published in 2010 and examining the lethal effects of the Vesuvius eruption in AD 79 on human beings living in the towns of Herculaneum, Oplontis and Pompeii explains, the impact and lethal range of the pyroclastic density flows (PDCs) from the Plinian eruption of that year are still "widely debated." That article describes in some detail the conclusion of the authors that the lethal effects of the Vesuvius eruption resulted from intense heat rather than from the layers of ash and debris which later buried the residents and their cities under 50 to 60 feet of volcanic material.

The paper explains that the upper temperature bound for human survival is no higher than 200 degrees C (which is 392 degrees F), and that the people of  Oplontis were subjected by the fast-moving PDCs pouring down from Vesuvius to temperatures of around 600 degrees C (which is 1,112 degrees F), the people of Herculaneum were exposed to temperatures of around 500 degrees C (which is 932 degrees F), and the people of Pompeii were exposed to temperatures between 250 and 300 degrees C (which is 482 to 572 degrees F), all temperatures well above the survival boundary for human beings.

The paper goes on to note that the most powerful of the pyroclastic flows or PDCs of the AD 79 eruption of Vesuvius "reached distances exceeding 20 kilometers from the vent." While I am not a volcano expert, this would suggest to me that (at the very least) anyone living within the boundaries of the circle drawn above (which is 15 miles in diameter, or approximately 24 kilometers in all directions from the central cone of the volcano) should be evacuated if scientists believe there is any possibility of a Plinian eruption of Popocatepetl.