By Julie Etra

With 38 volcanoes, a dozen of them active, Mexico still only has the eighth most volcanoes in the world. It’s not the world leader in earthquakes, either. However, the mutual potential for for volcanoes and earthquakes to cause disaster hangs over the country like a pall of smoke.

Mexico’s Big Three Volcanoes

Popocatépetl, an active volcano, is the second highest peak in Mexico at an elevation of 5,393 m (17,694 ft), following the highest peak, Citlaltépetl (Pico de Orizaba) at an elevation 5,636 m (18,491 ft). It is affectionately known by its nickname “El Popo.” Its name is derived from the Nahuatl popōca, meaning “it smokes” and tepētl, meaning “mountain” or “smoking mountain.” Citlaltépetl is also derived from Nahuatl: citlal means “star” and of course tepētl = mountain. (There is a stationary store on Gardenia called Papeleria Citlalli, so now you know what it means.)

At an elevation 5,230 m (17,160 ft), Iztaccíhuatl is the third highest mountain in Mexico and occurs just north of El Popo. Its name means white woman in Nahuatl (iztāc = “white”; cihuātl = “woman”), since it resembles a woman lying on her back and is often snow-covered.

The three volcanoes are located to the east of Mexico City: Popocatépetl is about 70 km (43 miles) southeast of Mexico City, where the states of México, Morelos, and Puebla meet; on a clear day, it is easily seen from the city. Iztaccíhuatul is about 90 km (54 miles) from Mexico City. Pico de Orizaba, about 200 km (120 miles) from Mexico City, rises just west of the city of Orizaba at the border of the states of Puebla and Veracruz. Those who drive to Huatulco from the north easily see Popocatepétl and Iztaccíhuatul looking south from 150D; Pico de Orizaba is on your left as you leave the state of Puebla and enter Veracruz.

All three volcanos are steep-walled stratovolcanos, generally symmetrical and cone-shaped and with a 400 x 600 m wide crater. Stratovolcanoes are sometimes called composite volcanoes because of their composite layered structure, formed from successive eruptions (strato = layer in Latin). And all three occur along the Trans-Mexican volcanic belt, aka the Mexican “Ring of Fire,” which stretches across central Mexico from the Pacific Ocean to the Gulf of Mexico – route 150D runs right through the middle of the volcanic belt.

El Popo is geologically connected to Iztaccíhuatl, 12.9 km (8 miles) to the north through the Paso de Cortés; this is the high pass that Hernando Cortés and his men followed after their conquest of Cholula in 1519, on their way to conquer the capital of the Aztec/Mexica Empire, Tenochtitlán.

The two volcanoes are protected as they lie in the Izta-Popo Zoquiapan National Park, which runs north and south within the Sierra Nevada range (Sierra Nevada means “snow covered” [nevada] “mountain range” [sierra]). On the west side of the range the watershed provides snow melt and creek water to the Valley of Mexico (formerly Lake Texcoco). Until relatively recently, the three volcanoes were the only instance of glaciation – they had year-round snow/ice cover – in Mexico; in the 1990s, however, both the Glaciar Norte and the Glaciar del Ventorillo of Popocatépetl began to retreat, due to both warming conditions and increased volcanism. Although ice remains in some places, Popocatépetl’s glaciers were gone by 2001.

Popocatépetl is Mexico’s most active volcano with 15 eruptions recorded since 1519. On May 20, 2023, both Mexico City airports (Benito Juarez Mexico City International Airport [MEX] and Felipe Angeles International Airport [NLU]) had to close temporarily due to increased volcanic activity and ash fall. Most recently, on November 1, 2023, the cone exploded with gray ash. This activity is not unusual, and in fact we stopped to watch it smoking on our way from Mexico City to Puebla a few years ago, with the sun setting behind it. Spectacular. Iztaccíhuatl is dormant and has not erupted since 1868. Pico de Orizaba last erupted in 1846.

Legends of the Mexican Volcanos

The Legend of Popocatépetl and Iztaccíhuatl. Legend has it that these two mountains represent a young warrior and a young princess. Once upon a time in Mexico (but after the rise of the Aztec empire), a beautiful Tlaxcalan maiden princess named Iztaccíhuatl fell in love with a young Tlaxcalan warrior, Popoca. (Tlaxcala is now a small state southeast of Mexico City.) She was the most beautiful princess who ever existed, and he was one of the most handsome and brave warriors of his village.

The Tlaxacans sided with the Spanish during the conquest of 1519-1521 in an effort to end the costly tributes they paid to the sprawling Aztec empire with its centralized, wealthy capital of Tenochtitlán (basically, Mexico City). Before departing for the ongoing wars with the powerful Aztecs, Popoca asked the cacique (chief) of the village for the hand of the princess. This was granted under the condition that the young man return safe and sound.
Popoca left for battle, presumably with the forces of Cortés, while the princess waited impatiently for his return. Meanwhile a jealous, poison-tongued rival, also in love with the princess, lied to her, fabricating a story of how her beloved had died in battle. Overcome by grief and inconsolable through this treacherous deceit, she died from a broken heart. A short time later, Popoca returned victoriously from battle ready to take the hand of his betrothed, only to find that she had died.

It is said that the young man, dejected, wandered through the streets for days and nights contemplating a way to honor their great love for each other. He decided to build her a large tomb under the Sun and compiled 10 hills to build an enormous mountain. Once built, he took the inert body of his beloved and laid her on the top of the mountain. As he kneeled over her with a smoking torch in one hand, he kissed her one last time, watching her dream eternally.

Since then, they have remained together. Eventually snow covered their bodies, becoming the two snow-capped enormous volcanoes that will remain unchanged until the end of time. When the warrior Popoca, now the mountain Popocatépetl, remembers his beloved Iztaccíhuatl, his heart, which maintains the fire of eternal passion, trembles, and his torch ignites again. That is why, even today, the Popocatépetl volcano continues to spew plumes of smoke from its fumaroles.

The Legend of Pico de Orizaba. At the peak of the Olmec civilization lived a beautiful and brave warrior named Nahuani. She was always seen in the company of her best friend, an eagle named Ahuilizapan (in Nahuatl, the “place of the happy waters,” pronunciation reduced to “Orizaba” in Spanish). Their friendship was legendary, and Ahuilizapan was always with her in battle. Finally, Nahuani died in battle and such was Ahuilizapan’s sadness and pain, the eagle flew as high as she could and plummeted back down to earth, where she eventually became a mountain and then a volcano. After many years of relative tranquility, Ahuilizapan remembered the moment she lost her best friend and began to spew lava. This is the reason that even now people climb this peak as high as they can, leaving offerings to keep the eagle calm.

Geology and a Brief Lesson in Plate Tectonics

Or, why the southern coast of Mexico is particularly prone to earthquakes.

The rigid outer shell of the planet, known as the lithosphere, is fractured into seven or eight major plates (depending on how they are defined) and many minor plates (“platelets”). Where the plates meet, their motion in relation to each other determines the type of plate boundary, known as faults and fault zones. They can move side by side, known as a strike slip, and under adjacent plates, called subduction, and in all kinds of combinations of movement. The relative movement of the plates typically ranges from zero to 10 cm annually. Faults result in earthquakes, volcanic activity, mountain-building, and oceanic trench formation. The Trans-Mexican volcanic belt and associated volcanoes result from the the Pacific Plate and the smaller Cocos Plate subducting beneath the North American Plate.

Oaxaca lies over the convergent boundary where the Cocos Plate is subducted beneath the North American Plate. The rate of convergence in this part of the boundary is 60 mm per year, or six times what is typical. This boundary is associated with many damaging earthquakes along the plate interface, within the descending Cocos slab, and within the overriding North American Plate

The frequency of earthquakes along the Pacific coast of Mexico is increased by geologic activity in the Middle American Trench, a submarine depression that runs from below Baja California in Mexico to Costa Rica. This oceanic trench is a major subduction zone, containing the Pacific, Cocos, and Nazca Plates on the ocean side and the North American and Caribbean Plates on the inland side. The trench is 2,750 km (1,700 miles) long and 6,669 m (21,880 feet) deep at its deepest point.

The Tehuantepec Ridge runs straight (an unusual configuration) across the Cocos Plate and under mainland Mexico near the Oaxaca-Chiapas border. The ridge is an old fracture zone, a place where plates stick; many shallow subduction angles result in perfect conditions for frequent, strong Oaxacan earthquakes. Indeed, Oaxaca has had over 14,000 earthquakes in or near the region since 1995; a quarter of all the earthquakes in Mexico occur in Oaxaca, and no, there is no homeowner’s earthquake insurance that I know of.

Notable Mexican Earthquakes
Oaxacan earthquake of 1931. On January 14, 1931, a devastating earthquake with a magnitude of 7.8 struck the state capital, Oaxaca de Juárez. Oaxaca City was pretty isolated at the time, with only 35,000 inhabitants versus the current population of 300,050 (2014 census). The quake lasted about four minutes. Archives reported that 80% of the homes were destroyed, but a number of weaker tremors, or foreshocks, increasing in intensity, preceded the major quake, as opposed to aftershocks (replicas in Spanish). This tectonic warning allowed residents to flee their homes, resulting in only about 60 fatalities.

Mexico City earthquake of 1985 struck on September 19 at just after 7 a.m. with a magnitude of 8.0. (For reference, the strongest earthquake ever recorded was a magnitude 9.5; the Great Chilean Earthquake occurred in Valdivia, a town on the southern coast of Chile, on May 22, 1960.) The Mexico City seismic event caused serious damage to the Greater Mexico City urban area and at least 5,000 fatalities. A foreshock of magnitude 5.2 had occurred the prior May, the main quake was September 19, and there were two large aftershocks whose epicenters were in the Middle American Trench – more than 350 kilometers (220 mi) away.

The event caused between $3 and $5 billion USD in damage. Hundreds of buildings were destroyed and thousands more were seriously damaged. The degree of damage was due to the large magnitude of the quake, the size of the urbanized area, the lack of engineering in old structures, and the ancient, wave-amplifying lake bed on which Mexico City lies. This unstable substrate proides one of the ostensible reasons that President Andrés Manuel López Obrador halted construction of a new Mexico City airport in 2018).

Oaxacan earthquake of 2108. The hypocenter of this magnitude 7.2 earthquake was located 24.5 km (15 miles) deep, and the epicenter was about 37 km (23 miles) northeast of Pinotepa de Don Luis in northwest Oaxaca near the border with the state of Guerrero. (The hypocenter is where IN the earth the quake starts; the epicenter is ON the surface). The epicenter was in a rural area, with little reported damage to structures. A total of 14 people were killed as a result of a military helicopter crash surveying the damage, and not from the earthquake itself.

Oaxacan earthquake of 2020. The last big earthquake in Oaxaca occurred on June 23, 2020, with a magnitude of 7.5. The epicenter was between San Miguel del Puerto (north and west of Copalita) and the small village of Santa María Zapotitlán on the Isthmus. While it shook here in Huatulco, with over 200 replicas, it devastated the town of Juchitán de Zaragoza on the Isthmus of Tehauntepec, where older structures were not engineered to withstand strong earthquakes. The quake was felt by an estimated 49 million people as far south as Guatemala, with some tremors felt as far away as 640 kilometers (400 mi). Thousands of houses in Oaxaca were damaged and ten fatalities were reported. A tsunami warning was issued for southern Mexico and as far south as Honduras, but the tsunami did not occur.

Mexican construction requirements have been strengthened to avoid earthquake damage. When we designed our house in Huatulco almost 15 years ago, the plans had to be approved by FONATUR in Mexico City, at the federal level, and withstand an 8.0 quake. That’s a lot of rebar but we had no damage to the house other than a few superficial cracks.