This Volcano Erupted in 1991: You Won’t Believe What Happened Next!

By: Kristopher Bangsil, Xavier Bodensieck, Sabrina Chan, Andrew Cook, Abigail Ritz, and Helen Warfle

The story of the Mt. Pinatubo eruption began several months before the actual explosion. On April 2, 1991, a series of small explosions caused a fissure to open up on the side of the mountain, alerting geologists to the volcano’s reawakening. Because of this, scientists from the USGS Volcano Hazards Program along with the Philippine Institute of Volcanology and Seismology (PHIVOLCS) began a joint operation with the US military to create a seismic map and observatory to monitor the volcano. Using technology developed in 1981 to monitor the Mount St. Helens eruption, the scientists were able to predict that the volcano would erupt around June 15, and they were surprisingly accurate. On June 6, a series of volcano-tectonic earthquakes began to “puff up” the volcano – that is to say that the volcano was preparing itself for the eruption. Thus, on June 10, 15,000 people were evacuated from the area. On June 12, the first eruption occurred, spewing a twelve-mile high ash column and convincing the scientists the evacuation had been warranted. On June 15, exactly as the scientists predicted, the volcano exploded. The eruption was so large that a new, 1.6-mile wide caldera was formed at the top of the volcano. Valleys in the area were filled with volcanic flows of magma and rock, layered as thick as 660 feet and the ash column grew to reach as far as twenty-eight miles into the atmosphere.

Lest you think that this was the end of the eruption, a meteorological event contributed to the devastation of the eruption. During the same period of time of the second, more extreme eruption, Typhoon Yunya moved into the island, bringing with it high wind and rains. This contributed to the devastation in three main ways. The first is that the high winds helped spread the ash cloud far beyond the originally projected limits, with ashfall being reported as far away as the Indian Ocean. The second is that the rain-soaked and weighed down the already-fallen ash, resulting in the collapse of rooftops. The third is a phenomenon known as a lahar or a volcanic mudflow that is usually initiated by glacial melt or water displaced from a volcanic crater. Instead, the rainfall from the typhoon started many lahars that rolled down from Mt. Pinatubo, increasing the destruction even after much of the volcanic output of magma and rock was over.

It is in this aspect that the “end” of the eruption is called into question. For many years after the eruption, rains continued to initiate lahars made up of the remaining debris from the eruption, continuing to wreak havoc on the community below the volcano, illustrating that a single geologic event can continue to affect a community long after the supposed end of the ordeal.  

A long, but comprehensive overview of the eruption.

Ashfall from Mount Pinatubo eruption over former Clark Airbase, Philippines. Source

According to the NASA Earth Observatory, the Pinatubo eruption erupted with such force that its plume of ash and sulfur dioxide penetrated into the stratosphere. The eruption released about 15 million tons of sulfur dioxide into the stratosphere, forming a layer of aerosol particles that were spread across the globe over the next two years due to strong stratospheric winds. Sulfuric acid droplets spread across the Earth for years and with the lack of clouds within the stratosphere, there was no natural method to quickly filter the pollutants out.  This resulted in the cooling of the Earth’s surface over these two years as the particles scattered and absorbed incoming sunlight. In fact, the scientists were able to measure a drop in the average global temperature of about one degree Fahrenheit in the fifteen months following the eruption.

While the enormous scale of the eruption meant that certain effects were felt across the world, local communities — about 100 miles outside of Manila — closest to the volcano experienced the most extreme damage.  The volcano emitted so much magma that the land directly below the volcano could no longer support the rock above, and the structure collapsed within itself forming a caldera. Years after the initial eruption occurred, the ground around the volcano has still reached temperatures up to 900 degrees F. When water has come into contact with these patches of land, small explosions have resulted causing mudflows of volcanic material to spread to the surrounding area.

Aeta People

As a result, the eruption of Mount Pinatubo displaced almost the entire population of Aeta people, who are considered aboriginal by anthropologists.  The Aeta believed Mount Pinatubo to be a god, whom they worshipped; they thus believed the eruption to be a consequence of this god’s anger with geologists drilling the mountain for energy and rogue foresters clearing land around the volcano.

The Filipino government’s response to the disaster included attempts to “civilize” the Aeta victims. The lack and insensitivity and lack of cultural knowledge of Aeta customs and beliefs by officials handling the aftermath were well noted. The official response included rehabilitation and resettlement programs, with little input by the Aeta people. Ultimately, these attempts failed, as the Aeta people returned to their religious and ancestral land.

Despite the damages to the environment and indigenous populations in the Philippines, the global consequences of the eruption could have been worse in the long term. Although Typhoon Yunya triggered disasters outside of the immediate threats associated with an eruption, the rains had apparently suppressed chemical reactions in the stratosphere that prevented serious ozone damage. According to 2017 NASA funded research, the interaction between the volcano’s hydrogen chloride (chlorine gas) and CFCs in the atmosphere could have severely damaged the planet’s ozone layer. The rains from the typhoon suppressed the two chemicals’ mixing and prevented larger difficulties with the climate while damaging the local communities at the foot of Mt. Pinatubo. The combination of eruption and typhoon was devastating though another combination event is unlikely to happen again with the next major eruption sure to damage the ozone like Mt. Pinatubo didn’t.


In observation of the 25th year after the eruption of Mt. Pinatubo, the Center for Kapampangan Studies of Holy Angel University in Angeles, Pampanga opened the Mount Pinatubo museum. The museum informs and honors what happened to the homes and lives in the communities surrounding Mt. Pinatubo by providing both a mural timeline that chronicles Mount Pinatubo’s history, from centuries ago all the way to the 1991 eruption, as well as sculptures that are dedicated to the stratovolcano and its eruption. One such sculpture is Kapampangan artist Arnel Garcia’s “Lumud” (Drown), which chillingly depicts the faces of families buried in lahar (volcanic mudflow) along with ordinary everyday items such as TVs, bikes, electric fans, kettles, religious figures, etc with a pregnant mother in the center (this seems reminiscent of the description of the agonized faces emerging from the Earth’s core as Nassun passes over it in The Stone Sky). In the words of Stanley Baldwin, “It is both a chilling and gruesome reminder of the power of Mother Nature and a testament to the resiliency and spirit of the Filipino.” In another display stands two pieces of wood labeled as Pinatubo’s Petrified Trees. While the smaller tree trunk was buried twice when Pinatubo erupted 3,000 years ago and 600 years ago and still remains wooden, the bigger tree piece is now solid rock and is found to be much older than Mt. Pinatubo itself.

Looking into natural disasters surrounding and affecting indigenous peoples is incredibly important from a cultural point of view. These events impact small, often insulated cultures in a significant way. Not only do the elements of this natural disaster displace them physically from their ancestral land, but it also holds religious significance. And this aspect of disaster is not only limited to the Aeta of Pinatubo; many cultures around the world are tied to the land. Natural disasters affect often ignored indigenous cultures all around the world in cataclysmic ways.

Given the eruption of Mt. Pinatubo’s effects on global climate and travel, it became very visible to world media. Associated issues were able to draw attention to themselves by finding Mt. Pinatubo’s impact on them. The Aeta people of the mountain, suffering from the eruption and secondary disasters, gained visibility through their close relationship with the mountain as a part of their history and culture. Their understanding of the volcano through mythologies allowed for a view of the eruption outside of the scientific and loss based appraisals of the larger situation. The eruption was incredibly damaging to the indigenous population, but they were likely able to find recognition and respect in their unique relationship to the volcano and appeal to a less analytical and more social-based analysis of the eruption.

On a brighter note, the release of Pinatubo’s global sulfur aerosol cloud allowed scientists to research and understand atmospheric circulation better and thus improving their monitoring methods and allowing these scientists to forecast the global effects of another major eruption. However, some scientists have also pointed out that these advanced systems won’t reverse the contributions similar disasters have made to global warming. These scientists advocate for change by altering the atmosphere ourselves otherwise known as geoengineering. In the case of the atmosphere, atmospheric scientist Alan Robock states that “to halt global warming, humans would have to inject 100 million tons of sulfur dioxide into the atmosphere every year—that amounts to about five Pinatubo eruptions per year.” However, other scientists argue that the consequences are too risky and unrealistic. For instance, many scientists worry that we would never be able to fully control the effects of geoengineering the Earth. The possibility of destroying the ozone is too high for some to warrant injecting gases into the atmosphere. And yet, we’ve seen other “authorities” take this leap of faith in The Broken Earth in the form of the node maintainers. The node maintainers are the human form of geoengineering, where orogenes are used to change the natural processes of the Earth. In the trilogy, the issues of this interference are obvious on a human level but there are also geological concerns about relying on preventive measures to change the Earth. Scientists have argued that in our world, a better plan of action would be to stop using fossil fuels altogether instead of attempting to alleviate their negative consequences. The same can be said of the node maintainers, where it would be more beneficial to work towards an end to the Seasons, rather than using orogenes as slaves to mitigate the Earth’s wrath.

The connection to Jemisin’s work in creating the appendix of the Seasons is also worth exploring, as many of the Seasons described there share characteristics with the Mt. Pinatubo eruption. These include The Season of Teeth, caused by “…a supervolcanic explosion… Ash went upper-atmospheric and spread around the globe rapidly…” (The Stone Sky 401). The Choking, Madness, Heavy Metal, and Twin Seasons also share characteristics with the Mt. Pinatubo eruption, namely the atmospheric spread of ashfall, causing widespread darkness and cooling of the atmosphere. Jemisin has said that she did a lot of geologic research, mostly with Hawaiian volcanoes. Regardless of location, it is clear that she had major volcanic explosions like Pinatubo, and their resulting effects on climate, in mind when she created the Seasons.

How to conclude such an expansive topic? Researching just one volcanic eruption has allowed us to engage in the process of thinkING about such diverse topics as indigenous rights, climate change and potential solutions, the inspiration for the Fifth Seasons, and more. It is certain that the experience of writing this post and the eruption itself will help us to engage with the real-world implications of Jemisin’s work. Regardless, it is clear that the Pinatubo eruption is something that we will be continuing to consider during the rest of the course and beyond.

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