I’ve had the pleasure of visiting Guatemala three times, the first time was in 2005, the second time was in 2006, and the third time was in 2015, and it was the one thing I’m passionate about which drew me to Guatemala, volcanoes. Now Guatemala has a bunch of fascinating volcanoes but what we know about is that just 3 of them are active, they are Santiaguito, Fuego, and Pacaya. However, there is another volcano which often catches my eye and it’s not even active, it is Volcan Agua. What fascinates me the most about Agua is the near perfect conical shape dominating the landscape near the colonial town of Antigua (or Antigua Guatemala). Go up to Cerro de la Cruz which lies to the north of town and you’ll get a majestic view of that stratovolcano rising above Antigua and the surrounding area.
I made two attempts to climb Volcan Agua and on both occasions I failed to reach the top. The first attempt came in November 2005 when we made it as far as third of the way up but had to abort in the end as the locals coming down told us it was raining up there, two even warned us that there were thieves with machetes about. The second attempt came in December 2006 but this time at least I made it further, I made it as far as the upper slopes where the vegetation becomes grassland but the reason for aborting the climb was that we ran out of time and needed the light to descend. I was later told that I was just an hour away from reaching the summit crater area.
No historical eruptions have been known on Volcan Agua but it’s still an impressive cone dominating the surrounding landscape along with the twin volcanoes Acatenango and Fuego, it rises to 3760m asl. The settlements of Antigua and Ciudad Vieja lie to the north of the volcano, San Miguel Duenas lies to the northwest, Alotenango lies to the west-northwest, Palin lies to the southeast, and Santa Maria de Jesus (which lies at the foot of the volcano) lies to the northeast.
The northern half of the volcano is used for farming on the lower flanks especially for crops. Volcan Agua is also known as “Hunahpu” in the local Kaqchikel Mayan language.
The summit crater rim is mostly breached to the north-northwest, and a slight collapse scarp is visible on the upper flanks on the north face of the volcano.
The 1541 debris flow
One disaster did occur on Volcan Agua during 11th September 1541, although it wasn’t volcanic in origin. A huge mudflow came down the flank following a period of heavy rains and destroyed the old capital of Guatemala, Ciudad Vieja. Over 600 people were killed. The capital was later moved to what was to become Antigua Guatemala.
It was suggested that Volcan Agua once contained a crater lake at the summit and that a part of the crater rim had ruptured causing a huge flow of water to come down the flanks. However, a scientific paper by USGS suggested that it was more likely to have been caused by a slope failure similar to the event of 30th October 1998 in Nicaragua when a slope failure on the south flank of Volcan Casita caused a debris avalanche killing between 1,560 and 1,680 people and destroyed towns and settlements on the way.
Would Volcan Agua erupt?
I’ve been struggling to find information on the prehistoric eruptions of Volcan Agua so evidence of volcanic activity is limited. The symmetrical cone of Agua suggests that it is of a relatively young age. It is understood that there are six small pit craters on the northwest flank, I’m guessing that this must indicate failed flank eruptions. However, a couple of small cones are present on the south flank of the volcano which indicate successful flank eruptions did take place in the past.
Numerous explosive eruptions did occur on Agua in the past 80,000 years, the most recent occurred over 10,000 years ago. Ash deposits from Volcan Agua are present as part of the Los Chocoyos ash deposits located to the south of Guatemala City. If you are climbing the volcano then you will see that after the halfway point there is a gorge one has to descend into in order to get up on to the other side, and in that gorge grey deposits are exposed suggesting that pyroclastic flows used to occur often. I personally passed through this gorge myself during my hike up back in 2006.
The twin volcanoes of Acatenango and Fuego lie directly opposite Volcan Agua, they both erupted during historical times. As we know, Volcan Fuego is frequently active and always has been since the Spaniards first colonised the land which is now today’s Guatemala. Volcan Acatenango on the other hand, has only produced three historical eruptions in 1924-25, 1926-27, and 1972. The construction of the twin peaks of Acatenango dated back to 85,000 years ago whereas Volcan Fuego was constructed over an older edifice, Meseta. The construction of Meseta dates back 230,000 years ago before it collapsed some time ago. It could be that the triple volcanoes of Agua, Acatenango, and Fuego were in a period of high activity at the time and may have gone through activity shifting between volcanoes or erupting simultaneously.
Based on it’s Andesitic to Basaltic-Andesite conical profile, if Volcan Agua were to be erupting again then the activity most likely would consist of minor to moderate explosions of strombolian or vulcanian style with the odd pyroclastic flows. In a scenario where a large eruption would take place pyroclastic flows could occur, and the urban areas especially around the base of the north face of the volcano would be at risk as well as the inhabitants. The village of Santa Maria de Jesus which is located up the hill from Antigua to the south lies the closest to Volcan Agua. Many crops would be destroyed too. Not only would there be a risk of eruptive activity, there would be a risk of lahars to follow too. Whilst there’s a lack of reports of lahar activity on Volcan Agua, it is understood that Agua is prone to lahar activity.
Volcan Agua has shown to be capable of explosive eruptions which produce pyroclastic flows based on the evidence which is available, and even a parasitic vent eruption. However, it has not been known to display an ounce of volcanic activity during historical times, not even fumarolic activity. It has been known before for volcanoes to reawaken after centuries of inactivity but I believe it’s highly unlikely that Volcan Agua will erupt in the short term and even if some activity does get detected, then INSIVUMEH and CONRED will be on it like greyhounds. So I don’t want to sound alarmist.
Global Volcanism Program
Lahar Hazards at Agua Volcano, Guatemala – S. P. Schilling, J. W. Vallance, O. Matias, and M.M. Howell.