© Christopher Earls Brennen


``These men set out and made every effort to climb to the
summit but without success on account of the thickness of
the snow, the repeated windstorms in which ashes from the
volcano were blown in their faces .... but they reached
very near the top, so near in fact that being there when
the smoke began to rush out, they reported it did so with
such noise and violence that the whole mountain seemed to
fall down ....''

Except from a letter to King Carlos V of Spain from Hernando
Cortés, dated Oct.30, 1520 (translated by J. Bayard Morris).


About 50 miles southeast of Mexico City, two massive volcanoes rise together out of the valley of the sun, reaching almost 18,000ft into the sky. The Aztecs called them the ``Smoking Mountain'' or Popcatépetl and the ``Sleeping Woman'' or Iztaccihuatl, and viewed them with awe and reverence. According to their legends, the warrior Popcatépetl fell in love with Iztaccihuatl who was the daughter of the emperor. After he had won a great victory against the enemies of the Aztecs, Popocatépetl resolved to return and claim her hand. However, his rivals sent forward word that he had been killed in the battle and, distraught, Iztaccihuatl died of grief. To assuage his pain, Popocatépetl built the two great mountains placing the body of Iztaccihuatl on one. He stands forever on the other, holding her smoking funeral torch aloft. Despite this association with their gods, Aztec belief did not forbid the exploration of these mountains and it is therefore possible that they climbed these peaks though no written or verbal record remains to confirm this. High on the side of Popocatépetl is a rocky projection known as the Ventorrillo on which were found the remains of a small enclosure that was built by the forerunners of the Aztecs about 900 AD. In the same vicinity, a number of artifacts including pieces of pottery, and parts of a jade necklace and obsidian knife were also found. In view of these relics it would be surprising if some young and adventurous Aztecs had not ventured up another three thousand feet to investigate the source of the noise and smoke.

Geologists tell us that, for the past 10,000 years, Popocatépetl has alternated between periods of vigorous explosive activity and periods of less effusive behavior. The activity has varied from mild steam-and-ash emissions to plinian eruptions accompanied by pyroclastic flows and surges. The current active period began about 1200 BP with an explosive eruption that enlarged the summit crater. Another explosion about 1000 BP produced a pyroclastic flow that descended the northern flank. The Aztec codices provide an historical record of many eruptions beginning with one in 1345 AD. Another large explosive eruption occurred in 1519 and another, perhaps, in 1663. Lava flows in the vicinity of the summit may also have occurred in historical time but cannot be attributed to specific eruptions. The last significant activity occurred in 1920-22 though minor ash clouds were observed in 1923-24, 1933, 1942-43 and 1947.

In March of 1519, Hernando Cortés landed in Veracruz at the start of his epic quest to conquer the land of the Aztecs. By chance, when Cortés arrived in Cholula (near Puebla) in October, 1519, Popocatépetl was erupting. In a letter to King Carlos V of Spain, Cortés described the scene:

``Eight leagues from this city of Cholula there are two marvellously high mountains whose summits still at the end of August are covered with snow so that nothing else can be seen of them. From the higher of the two (Popocatépetl) both by day and by night a great column of smoke comes forth and rises up into the clouds as straight as a staff, with such force that although a very violent wind continously blows over the mountain range, yet it cannot change the direction of the column.''

The Indians advised Cortés that it was not possible for anyone to reach the summit and survive. But, rising to the implicit challenge, the conquistador responded as described in the same letter:

``..., I was eager to know the secret of this which seemed to me not a little marvelous and accordingly I sent ten men such as were well fitted for the expedition with certain natives to guide them to find out the secret of the smoke, where and how it arose. These men set out and made every effort to climb to the summit but without success on account of the thickness of the snow, the repeated windstorms in which ashes from the volcano were blown in their faces, and also the great severity of the temperature, but they reached very near the top, so near in fact that being there when the smoke began to rush out, they reported it did so with such noise and violence that the whole mountain seemed to fall down; thereupon they descended, bringing a quantity of snow and icicles for us to see....''

The leader of this expedition was Diego de Ordaz who claimed that, contrary to Cortés's account, he had, in fact, reached the summit. A number of chroniclers of the time give credence to his version of the story. Ordaz claimed to have looked down into the spectacular crater on the summit and compared it to an oven in which glass is made. Cortés may have down-played Ordaz's accomplishments because of a developing rivalry between the two of them. King Carlos V granted Ordaz the right to include a volcano in the family crest, thus giving a seal of royal approval to Ordaz's account of the adventure.

During his legendary march from the coast, Cortés approached the Aztec capital by climbing the pass between Popcatépetl and Iztaccihuatl and the saddle, at an elevation of 12,000ft is now called Paso de Cortés. Two years later, in 1521, after his conquest of the Aztecs, the conquistador's army was running short of gunpowder and so Cortés dispatched Francisco Montano and four other men to climb Popocatépetl in an attempt to obtain sulphur from the crater. Unlike the earlier adventure, the story of this second expedition has been confirmed by historians and so must rank as the first known ascent of the mountain. With great publicity, Montano and his companions set out accompanied by Indians carrying supplies including ropes and blankets. A crowd of spectators gathered at the base of the volcano and waited with curiosity to see how matters would unfold. At the end of the first day, the expedition camped some distance above the snowline by digging a snow cave. However, during the night they were driven from their cave by sulphur fumes and the cold. Outside the night was black, the stars being obscured by the clouds and smoke. As they moved about to keep warm, one of the soldiers fell into a crevasse, from which he was lucky to be rescued unharmed.

At daylight they resumed their ascent only to be halted by a eruption that caused them to run for shelter from the falling debris. Though one soldier could not continue, the rest pressed on and eventually reached the crater at which moment another minor eruption took place. When the smoke cleared, they could see roiling pools of lava below. They cast lots to see who would venture down into the crater first and, appropriately, it fell to the leader, Montano, to be the trail-blazer. Thereupon, he was lowered by means of a makeshift rope, some 600ft down into the crater. Not only did he risk the possibility of failure of the rope, but also the very real hazard of asphyxiation, not to mention the risk of another explosive eruption. Apparently, he survived seven separate sorties into the inferno bringing back a load of sulphur each time. Another soldier then took over and, after six additional trips, they had accumulated some 60lbs of the sulphur that had motivated the expedition in the first place. This they hauled down the mountain to be greeted like conquering heroes. A triumphal procession accompanied them back to the capital where, it is said, that Cortés himself came out to greet them. However, this method of procuring sulphur was not the most efficacious and, in a later letter to the king, Cortés admits that it was easier to order shipments from Spain. However, Montano and his companions achieved immortality for the first documented ascent of Popocatépetl.

Thousands of climbers have reached the top of Popocatépetl since the days of Cortés and Montano and it is now such a well-travelled trail that even fairly inexperienced climbers can succeed without undue hardship or danger. A winding, asphalt road was built from the town of Amecameca (elevation 8070ft) right up to the Paso de Cortés at an altitude of about 12000ft. From this saddle, the road continues some distance up toward Popocatépetl, terminating at Tlamacas (12960ft) where several facilities have been built to serve both day trippers and climbers. In particular, the Vicente Guerrero Lodge provides dormitory accommodations and facilities for climbers and other vistitors. From Tlamacas, there are several standard routes by which to climb Popocatépetl, all of which we found described in R. J. Secor's book, ``A climbing guide to Mexico's volcanoes''.

After our succesful ascent of the Mountain of the Devil, Doug Hart and I began to to think about our next Mexican adventure and naturally started to consider an ascent of one of the large volcanoes. Eventually, these plans began to solidify and, with the help of one former Caltech student now resident in Mexico, Francisco Avila Segura, and one current Mexican student, Roberto Zenit Camacho, we made the necessary reservations. The party would consist of a Caltech graduate student, Garrett Reisman, Doug Hart and myself; Doug's wife Ann would accompany him but not climb the mountain. We arranged flights to arrive in Mexico City on Jan. 8, 1995, and made reservations at the Tlamacas lodge for at least four nights starting on Jan.10. We had allowed time for acclimatization and visualized the possibility of climbing both Popcatépetl and, a day or two later, Iztaccihuatl.

Date: Wed, 21 Dec 94 05:58:34 -0700
From: Francisco Avila Segura <>

Dear Dr. Brennen,
El Popocatepetl sent tons of ashes to the atmosphere today in the morning, it was not the usual `fumarolas' but something else, you should be aware of this when you come and ask around. Roberto tells me ......
I wish you the best of fun in mexico and a happy new year,

Sincerely Yours,

Date: Thu, 22 Dec 94 04:27:25 -0700
From: Francisco Avila Segura <>

Dear Dr. Brennen,
Last night 75000 people were evacuated from around Popocatepetl, so it may be quite serious. It has been trembling and having small (apparently) eruptions. I call the people in charge of the reservations in Tlamacas to ask for information but so far they have none.....


Date: Wed, 21 Dec 1994 22:18:05 -0700 (MST)
From: Global Volcanism Network <>
Subject: Popocatepetl, 21 Dec 1994

A UPI news story reports that three expolsions on the afternoon of 21 December (between 1330 and 1400 local time) caused ashfall in Puebla, about 45 km E. A resident was quoted as saying ``The street is all white, as if flour had been thrown.''
Servando de la Cruz (UNAM) was quoted as saying that the activity was similar to 1921 and in the 1940's, but that there was no other activity, and microseismicity was continuing ``in a very moderate manner''.
NBC News (USA) showed a few seconds of footage of the steaming volcano, apparently taken from a helicopter, tonight (21 Dec)........

Date: Thu, 22 Dec 1994 14:34:46 -0700 (MST)
From: ``Rick Wunderman, Global Volcanism Network''
Subject: Popocatepetl, 21 December Eruption

....... A 21 December Associated Press story by Lawrence Kootnikoff said Popocatepetl, ``spewed a column of roiling black ash Wednesday, dusting villages and farmland but causing no injuries.'' ``Television footage from traffic helicopters showed a dense column of ash belching from the summit. Reporters aboard the helicopters said the ash appeared to be blowing away from Mexico City to the southeast.''
A 21 December Reuter story stated Popocatepetl had ``five minor eruptions''. The story also noted that authorities estimated the mass of ash fall as about 5000 tons and that they had only evacuated a few people.

Date: Fri, 23 Dec 1994 16:47:45 -0700 (MST)
From: Rick Wunderman, Global Volcanism Network
Subject: Popocatepetl

....... A helicopter flight at 10:30 showed that most of the ash was issued near the lower rim of the inclined crater at the NE sector. A radial fissure could be observed on the NE flank of the cone. Some steam-producing vents could also be observed along the fissure, though the cloudy conditions makes this interpretation doubtful. Old cracks in the glacier appeared to have extended a significant amount toward the W.....
..... At this stage .... an evacuation of the most vulnerable towns and villages of the East sector of the volcano was started around 21:00 of December 21, and about 31,000 persons were moved during the night to shelters in safer areas.
...... As of Friday, 23 December, an AP report stated that the Puebla state government said 75,000 people would be evacuated from the countryside around the volcano. One of the evacuated towns, Santiago Xalitzintla, is located about 13km NE of the summit and sits along the road over the pass between Popocatepetl and Iztaccihuatl.

Date: Tue, 27 Dec 94 12:48:49 -0600 (CST)
From: Mena Iniesta Baltasar-IIM <>
To: Christopher Brennen <>
Subject: Roberto calling....

Dr. Brennen,
I've been following the news about Popo. The Tlamacas lodge has been closed. Twenty thousand people were evacuated. Reports from today's paper said that the volcano's activity hasn't increased in the last few days, but they are still under alert. It isn't clear when this alert state is gonna change. It is impossible to get to Tlamacas right now. Let me know what you think. Right now I wouldn't suggest you to come. It's unfortunate....


And so, just days before we were to embark on this adventure, the mountain baulked and we were forced to cancel our attempt to climb Popocatépetl. The volcano continued to rumble for several years and the lodge at Tlamacas remained closed. Thus, even if we had wanted, foolishly, to attempt the climb, the logistics would have been considerably more difficult. In fact, we did make preliminary plans to reschedule the trip the following year but cancelled again when it was clear that there was little change in the situation.

Date: Tue, 5 Mar 1996 16:58:49 MST
From: Global Volcanism Network <>
Subject: Popocatepetl Eruption, 5 March 1996

Eruption of June 1997

At 03:49:30 on March 5, an ash emission event was detected at Popocatepetl Volcano. A continous seismic signal of variable amplitude started abruptly at that time.... Mild ashfalls have been reported in the immediate area around the volcano, particularly in the North sector. During a helicopter reconnaissance flight, at 1200, ash deposits were confirmed, especially in the close neighbourhood of Tlamacas, and covering the snow cap. An ash and gas column about 800m high rising vertically could be seen, height at which it dispersed in a long plume towards the NorthEast. A sulphur smell could clearly be perceived near the crater. The emission of gas, steam and ash appeared to be generated from the same three sources in the eastern internal side of the crater that produced the 1994-95 activity. In general terms, this event seems very similar to that of December 21, 1994, but perhaps about an order of magnitude lower, and comparable to the levels of activity observed on December 26, 1994.
And from another source: After several months during which only fumarolic gases were being emitted at Popocatepetl it is now certain that emissions of ash resumed this morning. I just returned from a helicopter reconnaissance flight around Popo. The glacier and snow are entirely covered by ash, confirming statements made by direct witnesses who saw ash emissions this morning. From vents located at the base of the eastern inner crater walls a vigorous column of steam could be seen at 12.00pm from the helicopter. Seismograms indicate that the renewed emission of ash might have started this morning at 3.50am.

Date: Mon, 1 Apr 1996 13:39:54 MST
From: Hugo Delgado
Subject: Popo update

......On Friday (March 29), during a COSPEC flight, Lucio Cardenas, Juan Jose Ramirez and Hugo Delgado observed the appearance of a lava dome on the eastern side of the crater floor with an area of 400 sq. m. emplaced on the rim of the inner crater (a destroyed lava dome that formed during the 1920-1927 eruption). This lava dome was observed coming out from a source outside that inner crater but flowing into it. Today (April 1st) the dome was checked again and was observed filling up most of the inner crater (nearly 60 m deep) and increasing its area to nearly 600 sq. m. Close observation of the phenomena is planned through helicopter flights and COSPEC measurements besides the telemetered seismic and geodetic network.....

Date: Fri, 3 May 1996 14:19:32 MST
From: Claus Siebe
Subject: Popo update

On March 29 juvenile lava that started forming a viscous, presumably dacitic dome was first observed by Hugo Delgado during a COSPEC flight. Since then the dome did grow at a rapid rate. Emissions of ash along a NE-SW running fracture located at the SE inner wall of the main crater have also continued intermittently. Apparently, the emission center of the new domes is located between this fracture and the center of the small inner crater formed during the eruption in the 1920s. I did attend helicopter overflights on April 10, 12, 24 and 29. On all these occasions the gases emanating from the dome did not allow a clear view. The height of the dome was difficult to estimate but was at least 50 m. The dome was in addition growing horizontally.... By comparing pictures of the dome formed in the 1920s with the present dome it is absolutely clear that the present dome is by now already much larger...
On April 30 at 13.19pm local time a major explosion occurred at the new dome. A shower of ejecta was dispersed towards the NE. Maximum clast diameter was 0.5cm in the village of Xalitzintla, ca 12km NE of the crater, sand-sized ash fell in the city of Tlaxcala at a distance of 60km. Because of bad weather conditions, the explosion and accompanying phenomena were not recorded by the video camera aimed at Popo.
Yesterday, May 2nd, five mountain climbers were found dead a few hundred meters below the NE crater rim on Popos slopes. Their corpses were recovered by Civil Protection authorities and the first information regarding the possible cause of their death was due to lightning, because of severe burns. Latest information indicates that the climbers ascended the mountain in the early morning of April 30 and were reported missing the following day. In addition to the severe 3rd degree burnings, the corpses do also show severe injuries by contusions. It appears that the climbers could also have been killed by the explosion on April 30. Autopsies of the corpses should soon reveal the cause of death. During a helicopter flight this morning (May 3) I could clearly observe a depression at the surface of the new dome, near the SE inner wall of the main crater. In addition streaks of gravel and boulders were running down the NE outer slopes of the cone. These streaks of course material were 10 to 20m wide and a few hundred meters long and very close to the route of ascent to the mountain that is usually taken by most climbers.
It is absolutely possible that similar explosions will occur again in the near future for which reason mountain climbers should take the signs posted at Paso de Cortes seriously and not attempt (by no means) to get around the official prohibition to climb Popo....

Nature, Volume 388, 17 July, 1997:

On 30 June 30, Popcatépetl showered ash over Mexico City, about 72km away, in its largest eruption since 1927.......

It would be easy to overdramatize the possibility. Nevertheless it seems clear that we came close to the fate that befell those five climbers on April 30, 1996. And so, within the span left to me, it seems unlikely that I will ever get the chance to climb Popcatépetl. Some things are not meant to be. But it would please me greatly to believe that, someday, one of my young friends might remember to place my name in the cairn on the summit of the ``Smoking Mountain''.

Last updated 7/30/99.
Christopher E. Brennen