El Chichón 1982

A lesson on the clear signs of catastrophe that went unnoticed, and the importance of effective mitigation in unexpected situations

Introduction

El Chichón Volcano, also known as Chichonal, is a dome volcano located in the southeast of Mexico in the State of Chiapas. From its discovery in the early 20th century, El Chichón remained a relatively insignificant volcanic site with little information about its past activities (De la Cruz-Reyna and Martin-Del Pozzo 2009, 21). From March 28-April 4 of 1982, violent eruptions continued unexpectedly, creating the worst volcanic hazard in Mexico’s recorded history. While it has been known to the Mexican government and scientists that El Chichón was an active volcano, the eruption came as a complete surprise, thus preventing the government from providing effective mitigation to the damage that occurred (Tilling 2009, 3). Slow government response followed thereafter, and misinterpretations of the eruption activity caused additional damage to residents of Chiapas (Tilling 2009, 3). El Chichón’s pyroclastic flows and surges lead to 2000 casualties, and the destruction of an immediate 10km radius of the eruption site, as well as severe economic damages (De la Cruz-Reyna and Martin-Del Pozzo 2009, 22).

Location of various volcanoes in the country of Mexico. El Chichón is located in Chiapas, in the southern tip of Mexico. Map used is titled "Volcanoes", credit: Mexico_traveller_c

While the eruption of El Chichón in 1982 is not internationally recognized, its significance to the study of volcanism and how governmental institutions mitigate the effects of large natural hazards is highly influential. Before the 1982 eruption, El Chichón was barely studied except for testing for potential geothermal use. When El Chichón did show signs of future activity, it was ignored because the volcano was not considered to be a hazard to the surrounding area. This pertains to the lack of testing and the no known historical activity that El Chichón had. The lack of importance that El Chichón had before the 1982 eruption suggested that the Mexican government did not have sufficient supplies to deal with the oncoming damages. However, after the eruption, El Chichón became a heavily studied seismic area, leading to safer mitigation practices in many other volcanic regions. Scientists gained a better understanding of the preemptive signs of eruptions and prior histories of unstudied volcanoes.

El Chichón eruption, 1982

Before Eruption

Discovered in 1928, El Chichón was considered an active volcano of the post-Pleistocene period. El Chichón is considered a young volcano, as determined through its morphology and fumarolic activity, meaning that its formation and excessive gaseous emissions indicate newer development (Tilling 2009, 5). After the discovery of El Chichón in 1928, the site remained unstudied for upwards of 5 decades, not until the 1970s where the Comisión Federal de Electricidad evaluated the volcano for geothermal energy potential. In 1978, one study was conducted by Damon and Montesinos, which studied connections between volcanism and metallogenesis (Tilling 2009, 5). Prior to 1982, it was generally thought that volcanoes with no or very minimal history of eruptions were not a potential threat to surrounding environments, contributing to the ignorance of scientists and the government (Tilling 2009, 5). Scientists chose to ignore the increased seismic activity that occurred throughout 1981 and into 1982, which included small-magnitude earthquakes, increased stream temperatures, fumarolic activity, and constant rumbling noises (Tilling 2009, 5). No experiences, despite activity consistent and plentiful enough to be written about in a formal report, were ignored for around 2 years. As the date of the eruption neared, earthquakes around the seismic area increased in frequency and magnitude. One week before the onset of March 28, seismic activity was received at the Instituto de Geofísica (IGEF), however, due to the remote location of Chiapas, it was difficult to communicate to residents and local officials that there was suspicious seismic activity (De la Cruz-Reyna and Martin-Del Pozzo 2009, 23). The lack of communication as a result of the remote location of Chiapas insinuates that despite there being suspicious yet consistent seismic activity, it was still unimportant to warn the thousands of residents in the surrounding villages. Since experienced scientists believed that the El Chichón had no previous volcanic activity within recent history, the initial concerns were ignored. It was also not reported due to the unknown source of the activity. Despite it being the location of a proclaimed active volcano, it was a possibility that Karstic geographies in the area were receiving increased hydrogeologic stress, which explained the tremors (De la Cruz-Reyna and Martin-Del Pozzo 2009, 23). 

The Eruption

Near midnight at 23:15 on March 28, El Chichón first erupted, producing a phreatomagmatic eruption with a column about 18.5 km high (De la Cruz-Reyna and Martin-Del Pozzo 2009, 24). As a result, ashfall covered the surrounding areas, blanketing roads, buildings, and vegetation. Airports Villahermosa and Tixtla Gutierrez, 70 km north and south, respectively, forcefully closed in response (De la Cruz-Reyna and Martin-Del Pozzo 2009, 24). Damages and fatalities were not extensive, as pyroclastic flows or surges did not contribute to the March 28 eruption. Fatalities were estimated to be between 10 and 20 deaths, which is much smaller compared to the fatalities estimated for April 3 and 4. The cause of these first fatalities was likely due to roof collapse as a result of extensive ashfall (De la Cruz-Reyna and Martin-Del Pozzo 2009, 24). On March 30, the State of Chiapas recorded tremors at around 07:15, with two minor eruptions succeeding at 09:00 and 15:00 (De la Cruz-Reyna and Martin-Del Pozzo 2009, 24). These eruptions were recorded by seismographs. Minor tremors and eruptions continued from April 1-April 3 1982 but ended up ceasing activity on April 3.  

Direction and intensity of pyroclastic flow of El Chichón eruption. Map is titled "Simulación del Lahar de la erupción del volcán Chichonal" (1982). Credit: JulioPineda04

This map is a digital elevation model of the areas affected by the eruption. Shows the surrounding villages and their location, as well as the extent of the damage. Credit: (Tilling 2009, 8)

The night of April 3 at 19:35 as well as the morning of April 4 at 05:20, two incredibly violent explosions erupted from El Chichón. Despite both of them being of short duration, the power of the eruptions led to plumes of 32km and 29km in height, as well as pyroclastic surges along the entire perimeter of the volcano (De la Cruz-Reyna and Martin-Del Pozzo 2009, 24). The last two eruptions contributed mostly to the damages and casualties, with an estimated 1700-2300 killed and another 20,000 homeless. Activity after the eruption subsided; there was not much activity besides a small phreatic event on September 11, 1982 (Tilling 2009, 7). It is believed that the source of the eruption stems from subduction beneath the Cocos Plate and the North American plate, however, the collision is considered complex (De la Cruz-Reyna and Martin-Del Pozzo 2009, 21). Recently, it has been discovered that eleven major eruptions took place within the past 8,000 years, with intervals between 100 to 600 years (De la Cruz-Reyna and Martin-Del Pozzo 2009, 21).


Government Response

Up until the onset of the eruption in 1982, Mexico lacked any form of volcano or natural hazard management for when an emergency such as this arises. Due to this lack of management and government planning, it was extremely difficult to come up with a plan for specific natural hazards in the instance that evacuations and government aid were needed. The lack of government planning ultimately caused chaos amongst residents; there was no communication to the media about the situation nor was any plan broadcasted, so media outlets would provide conflicting and often exaggerated stories (Tilling 2009, 10). Mitigating the number of casualties and overall damages could have been possible if the Mexican government provided at the very least an adequate evacuation plan and proper medical care. Despite being aware of the topography of Mexico, specifically the remote location of Chiapas, as well as knowing about El Chichón's activity, there was absolutely no preparation for any form of emergencies for the entire country. From March 29-April 3, self-evacuation of Chiapas was advised by the government, as the extensive ashfall on March 28 led to hazards (Tilling 2009, 10). Because of the belief that the initial eruption would be the peak of the damage, it was advised that it would be safe to return to Chiapas, but this was not the case. There was little enforcement of evacuations, thus implying that the situation was not as serious as it really was (Tilling 2009, 10).

Many complications came with the lack of government aid during the eruption. Documentation, or a lack thereof, made it almost completely impossible to evacuate 22,000 people, especially with minimal military aid provided (Tillman 2009, 10). Evacuations were more so partial evacuations as opposed to total evacuations, which was the main contributor as to why the death toll was extremely high. Medical sites were set up in places that were not devastated by the initial eruption but were poorly located because of the pathways of later eruptions (Tillman 2009, 10). There were simply not enough resources for the damages that happened as a result of the eruption. Inconsistent messages were being relayed between government officials, providing inconsistent advice about what to do. This was a result of there being no prior experience in working with both short and long-lived eruptions (Tillman 2009, 11).


The Experience

Research teams and groups of scientists reached the State of Chiapas on March 29, 1982, the day after the initial eruption. The personal experience of scientists S. De la Cruz-Reyna and A.L. Martin-Del Pozzo were recorded while serving as researchers in Chiapas. Upon arrival, heavy ashfall was prevalent in the area, thus leading to poor visibility and leaving the residents in a state of shock and disbelief (De la Cruz-Reyna and Martin-Del Pozzo 2009, 26). While it caused widespread panic, De la Cruz-Reyna and Martin-Del Pozzo reported the news on the television as a “juicy gossip” story, rather than giving facts about what is happening and how to help. Villages in the Chiapas area, such as Guayabal and Colonia el Volcán were mostly abandoned; besides few farmers who needed to tend to their lands (De la Cruz-Reyna and Martin-Del Pozzo 2009, 27). While De la Cruz-Reyna and Martin-Del Pozzo observed the surrounding impacts of the initial eruption, they also conducted seismographic testing on El Chichón. Seismic operators studying El Chichón on March 29 expressed concern that the initial March 28th eruption was not the end of volcanic activity, however, while this was considered a fact among seismic professionals, scientists on the site refused to accept the seismologists’ word (De la Cruz-Reyna and Martin-Del Pozzo 2009, 27). De la Cruz-Reyna and Martin-Del Pozzo witnessed the eruptions on April 3 and 4, 1982, where on April 3, the seismograph detected strong surges, shortly then leading to the pyroclastic surge eruptions that caused the most damage. The intensity of the signals, which were shown on the seismographs to be saturated for 20 minutes and 2 hours, respectively, represented the strong eruptive columns and pyroclastic flow of each of the strong eruptions (De la Cruz-Reyna and Martin-Del Pozzo 2009, 28). After the eruptions, which were exponentially more violent than the previous, the surrounding State of Chiapas suffered many physical difficulties. Aerosol emissions from smoke and magma contributed to the deaths of residents, as well as temporarily reduced visibility and long-term respiration problems.

Pyroclastic flow of the eruption on April 3, 1982. Credit: S. De la Cruz-Reyna


Effects of El Chichón on Regional Environment

Traffic Jam due to the amount of ash on the roads. Traffic could not properly function due to the number of cars broken down on the road. Credit: S. De la Cruz-Reyna

The pyroclastic flows of El Chichón did leave some changes to the geographic region of Chiapas, as well as some environmental effects. When it comes to the physical structure of El Chichón, it was known prior to the eruption that there was a 2km wide Somma crater that had two domes, which totaled around 1260m, and a moat surrounding it where fumarolic activity was frequent (Macìas et al. 1996, 461). After the eruption, the pyroclastic surges destroyed the domes. What was left was a 1km wide crater with 200m high walls (Macìas et. al 1996, 461). Despite the removal of the dome having extremely negative effects on Chiapas’ population, it did help El Chichón with the reducing of pressure on the meteoric water and magma, thereby reducing more potential risks for volcanic events (Macìas et. al 1996, 468). The plumes from the eruption had asymmetrically deposited ash and debris, leaving lithic-rich and highly oxidized pyroclastic fall, as well as ash dunes around the site (Macìas et. al 1996, 469). In terms of temperature, the temperature in the region had dropped from 0.2-0.5ºC, until around 1985, three years after the eruption when the temperature warmed back to previous (Macìas et. al 1996, 469). Temperature drops were experienced globally. The temperature drops resulted from the plumes emitting atmospheric aerosols into the stratosphere, with minerals such as sulfur staying in the stratosphere for an extended period of time. Immediately after the eruption, visibility was minimal, and a faint foggy vision remained, but it did eventually return to previous conditions.

Crater of El Chichón after the eruption. Shows the extent in which the crater increased in size. Map titled " El Chichon (Chichonal), Mexico, April 1982" Credit: rwallace1_salisburyu


Future Preventative Measures

Preventative measures to mitigate the damages seen in El Chichón’s 1982 eruption did not exist until after the eruption and its aftermath had occurred. The first measure that was concluded was to perform sufficient geoscience studies after the discovery of new volcanoes. According to the volcanic eruptions of other volcanoes before El Chichón, young volcanoes with young morphology should have geologic dating studies (Tillman 2009, 13). Geologic studies on young volcanoes can determine the eruptive frequency, and by knowing this eruptive frequency, the long-term forecast and future activity of the volcano can be known (Tillman 2009, 13). Secondly, there should be mandatory baseline monitoring for high-risk volcanoes that is as high quality as the resources permit. Ideally, what baseline monitors should calculate is the real-time detection of volcanic activity, so that when suspicious activity actually happens, the baseline measurements studied over a long period of time can make it easier to indicate when irregular activity is present (Tillman 2009, 13). Activity in El Chichón was discovered to have been prevalent since 1979, 3 years before the eruption. If baseline monitoring was standard practice in the State of Chiapas, the government and scientists could have had ample time to prepare an alert for potential volcanic emergencies (Tillman 2009, 13). Prevalent baseline monitoring would have attracted attention to the situation, thus alerting the public and scientists. Previously, when irregular activity was taking place, the scientists at the site could not confirm or accept that the activity being recorded would result in an eruption. Presently, however, El Chichón has seismic monitoring (Tillman 2009, 13). In addition, hazard zonation maps should be available to show where eruptions may strike. If this is available, then emergency management can take place smoothly and effectively, which is contrasting to the 1982 eruption (Tillman 2009, 14). Lastly, it is detrimental to assume that the first eruption would be the only possible eruption. From March 29 to April 2, it was assumed that the eruption was over, mainly because of the drastically reduced activity levels after March 28th (Tillman 2009, 14). The majority of large eruptions last longer than a week, therefore, assuming that volcanic activity is a one-time release of years of built-up pressure would put many individuals at risk for their safety. Because of this incident, Mexico now has designated volcanologists and experienced specialists to handle the probability that El Chichón may erupt again. Technology today allows us to better communicate, especially in remote or distant regions, as opposed to communication in the 1970s and 1980s.

Palm trees destroyed by the ash fall after the March 28, 1982 eruption. Credit: A.L. Martin-Del Pozzo


Conclusion

The eruption of El Chichón from March to April of 1982 signified a necessary shift in which we study and present volcanological data. The eruption of El Chichón’s unexpected nature was not due to unexplained geological processes, but it was in fact the negligence of scientists and the Mexican government that prevented anybody from knowing the onset signs of volcanic activity. Because of this, 22,000 individuals in the State of Chiapas did not receive proper medical care or evacuation plans, nor did they receive accurate media information. After El Chichón’s eruption, it became standard to provide more testing on newer volcanic sites. Effective communication, educating the public through accurate information, and having adequate resources is the most important factor in mitigating the negative effects of potential natural hazards. Environmentally, El Chichón had expected effects on the atmosphere in the sense that the pyroclastic surges and eruption plumes catapulted sulfuric aerosols into the stratosphere, making the region slightly cooler for a short period of time until it returned to normal. From the first-hand experience of scientists at the site, it was evident that no preparation was remotely thought out regardless of whether the Mexican government or scientists were aware of what was going to happen. If anything, El Chichón taught the public to expect the consequences of natural hazards if you ignore the warning signs.


References

Tilling, Robert I. "El Chichón's" surprise" eruption in 1982: Lessons for reducing volcano risk." Geofísica internacional 48, no. 1 (2009): 3-19.

la Cruz-Reyna, De, and A. L. Martin Del Pozzo. "The 1982 eruption of El Chichón volcano, Mexico: eyewitness of the disaster." Geofísica internacional 48, no. 1 (2009): 21-31.

Macías, J. L., M. F. Sheridan, and J. M. Espíndola. "Reappraisal of the 1982 eruptions of El Chichón Volcano, Chiapas, Mexico: new data from proximal deposits." Bulletin of Volcanology 58, no. 6 (1997): 459-471.

El Chichón eruption, 1982

This map is a digital elevation model of the areas affected by the eruption. Shows the surrounding villages and their location, as well as the extent of the damage. Credit: (Tilling 2009, 8)

Pyroclastic flow of the eruption on April 3, 1982. Credit: S. De la Cruz-Reyna

Traffic Jam due to the amount of ash on the roads. Traffic could not properly function due to the number of cars broken down on the road. Credit: S. De la Cruz-Reyna

Palm trees destroyed by the ash fall after the March 28, 1982 eruption. Credit: A.L. Martin-Del Pozzo