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Remembering Mount Pinatubo 25 Years Ago

The world’s largest volcanic eruption to happen in the past 100 years was the June 15, 1991, eruption of Mount Pinatubo in the Philippines.

Bursts of gas-charged magma exploded into umbrella ash clouds, hot flows of gas and ash descended the volcano’s flanks and lahars swept down valleys. The collaborative work of scientists from the U.S. Geological Survey (USGS) , and the Philippine Institute of Volcanology and Seismology (PHIVOLCS) saved more than 5,000 lives and $250 million in property by forecasting Pinatubo's 1991 climactic eruption in time to evacuate local residents and the U.S. Clark Air Force Base that happened to be situated only 9 miles from the volcano.

U.S. and Filipino scientists worked with U.S. military commanders and Filipino public officials to put evacuation plans in place and carry them out 48 hours before the catastrophic eruption. As in 1991 at Pinatubo, today the USGS is supported by The US Agency for International Development’s (USAID) Office of U.S. Foreign Disaster Assistance to provide scientific assistance to countries around the world though VDAP, the Volcano Disaster Assistance Program . The program and its partners respond to volcanic unrest, build monitoring infrastructure, assess hazards and vulnerability, and improve understanding of eruptive processes and forecasting to prevent natural hazards, such as volcanic eruptions, from becoming human tragedies.

mount pinatubo case study

Monitoring:  10 weeks before the eruption

At Pinatubo, the volcanic unrest began April 2, 1991, with a series of small steam explosions. In Manila, Dr. Raymundo Punongbayan, Director of PHIVOLCS, dispatched a team to investigate a fissure that opened on the north side of the volcano and was emitting steam and sulfur fumes. PHIVOLCS set up a seismograph and began monitoring earthquakes. Dr. Punongbayan also called his friend, Dr. Chris Newhall, at the USGS. The two scientists began working on how to get the USGS-USAID Volcano Disaster Assistance Program team to the Philippines to help monitor Pinatubo.

Three weeks later, Newhall, along with VDAP volcanologists Andy Lockhart, John Power, John Ewert, Rick Hoblitt and Dave Harlow, began unpacking 35 trunks of gear at temporary quarters on Clark Air Base. The seismic drum room was a maze of wires and cables; the daily drum roll of seismicity posted on the walls. Instrumentation was drawn principally from a permanent supply of specialized equipment kept ready for volcano crises under the auspices of the USGS Volcano Hazards Program and the joint USGS-USAID VDAP. They nicknamed the place PVO—the Pinatubo Volcano Observatory.

helicopter dropping off scientists and gear in open grassy field

With air assistance from the U.S. military, the PHIVOLCS-VDAP team installed seven telemetered seismic sites, two telemetered tiltmeters to measure ground deformation, and used a COSPEC (correlation spectrometry) instrument to measure sulfur dioxide gases that would presage arrival of new magma deep in the volcano’s plumbing. All efforts were focused on answering the questions — will Pinatubo erupt catastrophically, and when?

Volcanologists are first to admit that forecasting what a volcano will do next is a challenge. In late May, the number of seismic events under the volcano fluctuated from day-to-day. Trends in rate and character of seismicity, earthquake hypocenter locations, or other measured parameters were not conclusive in forecasting an eruption. A software program called RSAM (real-time seismic amplitude measurement), developed in 1985 to keep an eye on Mount St. Helens, helped scientists analyze seismic data to estimate the pent-up energy within Pinatubo that might indicate an imminent eruption.

There was no existing volcanic hazards map of the Pinatubo volcano, so one was quickly compiled by the PHIVOLCS-VDAP team to show areas most susceptible to ashflows, mudflows and ashfall. The map was based on the maximum known extent of each type of deposit from past eruptions and was intended to be a worst-case scenario. The map proved to forecast closely the areas that would be devastated on June 15.

mount pinatubo case study

Evacuation: 48 hours before the first ash eruption

The Clark Air Base sprawled over nearly 10,000 acres with its western end nestled in the lush, gently rolling foothills of the Zambales Mountains–only 9 miles (14 km) east of Mount Pinatubo. Military housing was located on the “Hill” closest to the volcano, with nearly 2,000 homes, elementary schools, a middle school, a new high school, a convenience store and restaurant. At the time, the population of Clark and nearby cities of Angeles, Sapangbato, Dau and Mabalacat numbered about 250,000. The PHIVOLCS-VDAP team developed an alert system and distributed it to civil defense and local officials as a simple means to communicate changing volcanic risk.

Senior base officials listened to daily briefings and put together plans to evacuate. Everyone agreed that if there were an evacuation, people must be moved to an area where they would be safe—not statistically safe, but perfectly safe. The location chosen was 25 miles (40 km) away at Naval Station Subic Bay and Naval Air Station Cubi Point.

Beginning June 6, a swarm of progressively shallower volcano-tectonic earthquakes accompanied by inflationary tilt (the “puffing up” of the volcano) on the upper east flank of the mountain, culminated in the extrusion of a small lava dome, and continuous low-level ash emission. Early June 10, in the face of a growing dome, increasing ash emission and worrisome seismicity, 15,000 nonessential personnel and dependents were evacuated by road from Clark to Subic Bay. By then, almost all aircraft had been removed from Clark and local residents had evacuated. The USGS and PHIVOLCS scientists did their own “bugout,” moving the monitoring observatory to an alternate command post located just inside the base perimeter near the Dau gate, an additional five miles (8 km) away from the volcano.

Distant view of erupting volcanic ash cloud rising over cars in parking lot in forground

On June 12 (Philippine Independence Day), the volcano’s first spectacular eruption sent an ash column 12 miles (19 km) into the air. Additional explosions occurred overnight and the morning of June 13. Seismic activity during this period became intense. The visual display of umbrella-shaped ash clouds convinced everyone that evacuations were the right thing to do.

Eruption: June 15, 1991

When even more highly gas-charged magma reached Pinatubo's surface June 15, the volcano exploded. The ash cloud rose 28 miles (40 km) into the air. Volcanic ash and pumice blanketed the countryside. Huge avalanches of searing hot ash, gas and pumice fragments, called pyroclastic flows, roared down the flanks of Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as 660 feet (200 meters) thick. The eruption removed so much magma and rock from beneath the volcano that the summit collapsed to form a small caldera 1.6 miles (2.5 km) across.

If the huge volcanic eruption were not enough, Typhoon Yunya moved ashore at the same time with rain and high winds. The effect was to bring ashfall to not only those areas that expected it, but also many areas (including Manila and Subic Bay) that did not. Fine ash fell as far away as the Indian Ocean, and satellites tracked the ash cloud as it traveled several times around the globe. At least 17 commercial jets inadvertently flew through the drifting ash cloud, sustaining about $100 million in damage.

With the ashfall came darkness and the sounds of lahars rumbling down the rivers. Several smaller lahars washed through Clark, flowing across the base in enormously powerful sheets, slamming into buildings and scattering cars as if they were toys. Nearly every bridge within 18 miles (30 km) of Mount Pinatubo was destroyed. Several lowland towns were flooded or partially buried in mud.

The volcanologists at the Dau command post watched monitoring stations on Pinatubo fail, destroyed by the eruption. They watched telemetry go down but then come back up – a sign that a pyroclastic flow was headed down valley and temporarily interfering with the radio links. They moved to the back of a cinderblock structure to maybe provide a little more protection from hot gas and ash; there was nowhere else for them to go. Fortunately, the flow stopped before it reached the building.

Damaged jumbo jet airplane covered in volcanic ash, with collapsed rear end

Aftermath: Adapting and learning

The post-eruption landscape at Pinatubo was disorienting; familiar but at the same time, totally different. Acacia trees lay in gray heaps, trees and shrubs were covered in ash. Roofs collapsed from the tremendous stresses of wet ash and continuing earthquakes. No matter which way one turned, everything looked the same shade of gray.

aerial view of Clark Air Force base showing base covered in volcanic ash, and some buildings collapsed

Most of the deaths (more than 840 people) and injuries from the eruption were from the collapse of roofs under wet heavy ash. Many of these roof failures would not have occurred if there had been no typhoon. Rain continued to create hazards over the next several years, as the volcanic deposits were remobilized into secondary mudflows. Damage to bridges, irrigation-canal systems, roads, cropland and urban areas occurred in the wake of each significant rainfall. Many more people were affected for much longer by rain-induced lahars than by the eruption itself.

By the end of 1991, and into 1992, more than 23 USGS geologists, seismologists, hydrologists, and electronics and computer specialists had each spent between three and eight weeks at Pinatubo and helped PHIVOLCS advise community and national leaders and those at-risk and studying the volcano to better understand what causes giant eruptions and how to forecast them, whether in the U.S. or abroad.

Much weaker but still spectacular eruptions of ash occurred occasionally through early September 1991. From July to October 1992, a lava dome grew in the new caldera as fresh magma rose from deep beneath Pinatubo. For now, the volcano is quiet, and the U.S. transferred Clark Air Force Base to the Philippine government in November 1991. The base has been repurposed as a trade and commercial center with large airport.

What would be different if the situation occurred today?  Consider that in 1991 there was no easy access to the internet, no connections to other data sets or scientists other than by telephone. The first popular web browser was a couple of years off, CD writers cost around $10,000, and scientific data and analysis were shared mainly by fax. The Pinatubo Volcano Observatory in 1991 was a self-contained unit; data from the monitoring network were radioed to it and the analysis was done by scientists on-site. Today, data received at PVO would be forwarded to colleagues in the U.S. and elsewhere for more sophisticated analysis with the results quickly transmitted back to PVO. Satellite data measuring ground temperatures, gas emissions, and inflation or deflation of the volcano would be sent to PVO where it would be integrated with other data sources to develop forecasts and inform hazard mitigation efforts. Tools and expertise would no longer be confined to what was physically at the observatory, but instead a global support group would be available to aid the response. Monitoring instruments have also improved greatly in performance while at the same time dropping in price and power consumption. There is no doubt that with the communication and monitoring tools available to us today, we would learn much more about the buildup to the eruptions and have more and better data to guide our decision-making.

For successful natural hazard mitigation, it all comes down to the right combination of monitoring data and scientific skill, and then just as important, scientists and public officials who are effective at communicating with each other and with the public who may be in harm's way. At Pinatubo, the quick deployment of monitoring instruments and preparation of a volcanic hazards map by the PHIVOLCS and VDAP team helped to better understand the precursors of volcanic activity and provided the basis for accurate warnings of impending eruptions. The willingness of base commanders, public officials and citizens to take the necessary precautions lessened the risk from this catastrophic eruption.

Learn more:

Pinatubo 1991 Case Study, Volcanic Ash Impact & Mitigation

The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines , USGS Fact Sheet 113-97

Benefits of Volcano Monitoring Far Outweigh Costs–The Case of Mount Pinatubo USGS Fact Sheet 115-97

FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines , edited by Christopher G. Newhall and Raymundo S. Punongbayan, 1996

NOVA: In the Path of a Killer Volcano , TV program

The Ash Warriors , by C.R. Anderegg

The International Association of Volcanology and Chemistry of the Earth's Interior’s (IAVCEI) video for crisis education

USGS-USAID Volcano Disaster Assistance Program

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Pinatubo 1991

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Mt. Pinatubo is a stratovolcano in the Philippines. June 15, 1991, it erupted, resulting in the second-largest eruption of the 20 th century. The ash plume height reaching more than 40 km (28 mi) high and ejecting more than 10 km 3 of magma , classifying it as plinian /ultra plinian eruption style and VEI 6 in eruption size.

A complicating factor in the dispersal of ash was at the same time as the eruption, Typhoon Yunna channeled the ash from the usual dispersal out to the ocean toward the island of Luzon. This combination gave rise to wet ash, increasing loading on structures with a large proportion of the 847 death toll due to roof collapse.

1991 Mt. Pinatubo eruption caused widespread impacts across societal, economic and environmental areas. Pyroclastic flows, lahars as well as the ashfall hazard all resulted in damage and casualties. The eruption cost $700 million in damage, $100 million of which was damage to 16 aircraft flying at the time of the eruption and $250 million in property with the rest a combination of agriculture, forestry and land.

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Internet Geography

The 1991 eruption of Mount Pinatubo

On 9 June 1991, Mount Pinatubo, a volcano in the Zambales Range, 80km (50 miles) north of Manila, capital of the Philippines, hit the headlines. It became one of the three largest eruptions in the world in the 20th Century. From the 9 June there were many eruptions (timeline of events). However, none matched that of 12 June. Ash turned day into night. The eruption caused the deaths of over 700 people. 200 000 buildings were destroyed.

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Original research article, volcanic risk mitigation that could have been derailed but wasn’t: pinatubo, philippines 1991.


  • Mirisbiris Garden and Nature Center, Sto Domingo Albay, Philippines

This is the story of a successful risk mitigation effort at Mount Pinatubo in 1991 that could easily have failed. The counterfactuals are the myriad of ways that the effort could have failed but didn’t. Forecasts for a large, VEI 6 eruption were the basis of 10, 20, 30 and, during the climactic eruption, even 40 km radius evacuations. Let’s use the metaphor of a train headed for the destination of successful mitigation, but that could have easily have been derailed or slowed and shunted off to a siding. Among the possible nodes of derailment: capability and trust between responding institutions; external distractions, both natural and man-made; early alert; scientific judgment of whether, when, and how big an eruption will occur; stochastic or unpredictable factors that can make even the best scientific judgment moot; optimal balance between caution and decisive actions, by scientists and civil defense alike; and effective communication between all parties. Potential derailments are detailed at each of these nodes for Pinatubo.


Mount Pinatubo (hereafter, Pinatubo), in the Philippines, produced a large, VEI 6 eruption on June 15, 1991—now known to be the 3rd largest eruption in the 20th century – smaller than Santa Maria 1902, about half the size of Katmai 1912, and one-third the size of the famous Krakatau eruption of 1883. Twenty-thousand indigenous Aetas lived on and near Pinatubo, and nearly 1 million lowland Filipinos and two large American military bases were severely affected. About 400 were killed in the eruption, while many thousands were saved by eruption forecasts and evacuations.

Some counterfactuals about natural hazards note events that might have been much bigger or much smaller than what actually occurred. Indeed, based on what we learned from the geologic record AFTER June 15, the climactic eruption could have been an order of magnitude larger or several of orders of magnitude smaller. Magnitude of natural events is a major uncertainty in hazard and risk estimation.

Rather than focus on a larger or smaller eruption, this paper focuses on a different question: How might the mitigation effort have failed? Our focus is on the mitigation effort, not on the natural event. This paper documents a number of different factors that could have derailed or slowed mitigation efforts related to the main eruption, on June 15, 1991. Interested readers can find additional details of pre-eruption events in Newhall and Punongbayan (1996a) and in Leone and Gaillard (1999) .

Newhall and Punongbayan (1996b) addressed the same theme as the current paper, but was written with shorter retrospect. Have the intervening years changed my earlier view of a “narrow margin of successful volcanic-risk mitigation?” No, quite the opposite. Narrow misses still occur. Reflections on Pinatubo and application of its lessons to other volcanoes have for me, reinforced the importance (and fragility!) of human factors—including teamwork, trust, and attention to two-way communication. I am glad to see social scientists and professional communicators joining “physical volcanologists” in crisis responses.

A reviewer’s comment bears special note: “ Imagining how an outcome may have changed if certain people had behaved differently or (non-volcanic) events had taken a different course may at first sight appear to be an indulgence with limited practical application. ” This is true, so I invite readers to generalize from the specific individuals and past events of Pinatubo to individuals and processes of your own teams. Individuals and their past experiences will change, but lessons learned from one crisis should also add to the cumulative body of experience for the next. Post-facto analyses of crisis response, and papers like this, can help. Newhall et al. (2021) includes lessons from Pinatubo for successful volcanic risk mitigation elsewhere.

An Analogy With Train Tracks With Destination of Successful Risk Mitigation

Figure 1 shows metaphorical train tracks with a number of nodes along the route at which a mitigation “train” could get derailed or shunted onto a siding and slowed. Each node is described below in details particular to Pinatubo, but readers might well imagine this as a generic train of other risk mitigation efforts they have known. A few of these factors were unique to Pinatubo; most were not.


FIGURE 1 . Metaphorical path of train to successful risk mitigation, without getting derailed or shunted to siding along the way. Details of the various waystations in the Pinatubo case are given in the text.

Capable Observatory and Civil Defense

Notwithstanding Hollywood portrayals of individual heroes who save the world, risk mitigation is generally a multi-institution and team effort. What institutions responded to Pinatubo? The first was the Philippine Institute of Volcanology and Seismology (PHIVOLCS), led by the late Dr. Raymundo Punongbayan. In 1991, PHIVOLCS was a relatively small agency which had, in the preceding decade, grown in capability and stature by responses to the eruption of Mayon Volcano in 1984 and to the M 7.8 Luzon earthquake of July 16, 1990. PHIVOLCS scientists had studied or were studying at universities in Manila and overseas, in the US, Japan, France, and New Zealand. Without direct crisis response responsibility, but with helpful geologic, geochemical, and drilling experience at Pinatubo, was the geothermal group of the Philippine National Oil Corporation (PNOC). Francisco “Jun” Delfin of PNOC provided valuable insights from PNOC’s geothermal exploration of Pinatubo in the mid-late 1980s. The US Geological Survey had a USAID-USGS funded Volcano Disaster Assistance Program (VDAP), envisioned after the eruption of Mount St. Helens in 1980, beta-tested with PHIVOLCS at Mayon in 1984, and strengthened after the Nevado del Ruiz disaster in 1985, well-equipped and ready to help upon request. The author was on a several-year bureaucratic assignment in USGS headquarters, but had prior ties with PHIVOLCS and VDAP. A high level of trust had already been built between PHIVOLCS and the VDAP group. Similarly, for civil defense matters, PHIVOLCS already a long-standing and strong collaboration and trust with the National Disaster Coordinating Committee (NDCC) and its operating arm, the Office of Civil Defense, led by Engineer Fortunato Dejoras. So, in the general picture, institutional capability and trust were quite good.

But it is easy to imagine that it might not have been as good. Eruptions of Mount St. Helens in 1980, Mayon in 1984, and Nevado del Ruiz in 1985 might never have happened, so advances after those and many other eruptions might not have occurred. Every eruption teaches new lessons, and there is no singular path toward critical new understanding, but the abovementioned three eruptions were high in our consciousness. The influx of capable young scientists into PHIVOLCS was certainly promoted by the 1984 Mayon eruption and the 1990 M7.8 Luzon earthquake. Likewise, the USGS and USAID would not have formed and funded VDAP without Mount St. Helens and Nevado del Ruiz; Dr. Norman Banks of USGS deserves credit for being an early and tireless advocate of VDAP. Mayon. Trust between VDAP and PHIVOLCS was surely aided by Dr. Punongbayan having done his PhD studies in Colorado, personal friendship with several USGS scientists, the author’s prior studies and family ties in the Philippines, and many a friendly discussion over beer.

At Pinatubo, Philippine and American militaries and USAID Philippines provided key logistical support. Neither PHIVOLCS nor USGS had much cash to commit to Pinatubo response, but logistics are expensive. We were concerned at first that our scientific response might become a political pawn in contentious negotiations for renewal of leases for the American military bases, but those who provided logistical help did so with almost no hint of politicization. Without the vehicles and drivers from USAID, and without the helicopter, housing, communications, and other support from US military, particularly the US Air Force at Clark Air Base before the eruption and US Navy and Marines at Subic Bay Naval Station after the eruption, and the Philippine Air Force both before and after the eruption, our scientific response would have been much slower and less effective. Where no roads were available, helicopters enabled us to reach sites and install instruments in hours, vs. days if on foot. When our team on the eastern side of Pinatubo ran out of cash (early on), being on Clark AB let us write IOUs and charge credit cards. When we needed closer looks from the air, helicopter and satellite support helped immensely.

The strength of these institutions and mutual trust was the engine that powered the train toward mitigation.

A sub header under institutional capability is the experience of team members, and, more explicitly, eruptions they have known. All volcanologists are strongly influenced by eruptions they have known, and also by what has been learned by colleagues at other volcanoes. Collectively, the team members at Pinatubo had a wide range of experience. One could list dozens, probably hundreds of scientific and response-related lessons that build the collective experience and knowledge of any team, and the counterfactual here is that one can also imagine dozens of those lessons that would NOT have been learned, or available to the Pinatubo team, had those earlier eruptions not occurred, or had the team members not been involved in those earlier eruptions or learned about them from scientific meetings and literature. Several of the key PHIVOLCS team members had valuable experience from Mayon; I had learned much about large silicic eruptions and deposits from Mount St. Helens and earlier work at Atitlán caldera, and Director Punongbayan had also visited Mount St. Helens. On the response side, the then-still-fresh eruption of Redoubt Volcano in 1989–90 had pushed me and other reluctant scientists to simplify our message into simple alert levels, drawing at that time from an earlier scheme suggested by the late John Tomblin for Rabaul Caldera in the early 1980’s. And our collective experience with the giant landslide and lateral blast at Mount St. Helens, though not likely at Pinatubo, was a constant reminder that “worst cases” really do occur, and must be foretold!

External Distractions, Both Natural and Man-Made

No volcanic crisis arises in a vacuum, and other events can be distractions. From Nature, the M7.8 Luzon earthquake of 1990 had commanded most of PHIVOLCS’ attention during the preceding year, and (earthquake-triggered) unrest at Taal Volcano, close to Manila, was demanding most of its time and resources up until, and even for a short time after, the first unmistakable signs of unrest at Pinatubo on April 2, 1991. It is easy to imagine that if Taal had erupted in early 1991 as it did in early 2020, or worse, PHIVOLCS would have been so preoccupied with Taal that Pinatubo would not have gotten the attention that it needed. Volcano observatories have limits to their logistical and staffing capabilities, and workloads need to be managed to avoid burn-out.

Potential man-made distractions included the contentious renegotiation between the US and the Philippines for Clark Air Base and Subic Bay Naval Station; focus by the author on organization of the first International Workshop of Volcanic Ash and Aviation Safety scheduled for July 1991; and focus by USAID Office of Foreign Disaster Assistance (OFDA) on post-Gulf War recovery in Kuwait. The first was a political minefield that both PHIVOLCS and the USGS wanted to avoid. Science and natural disasters are apolitical, and our responses should be too.

Another distraction was concern from USAID that USGS was using Pinatubo as an excuse for research under USAID funding. Initially, neither the USAID Mission Director in the Philippines nor OFDA in Washington supported the idea of VDAP help at Pinatubo, and USGS could not respond without USAID approval and support. It took phone calls and cables from the US Ambassador (Nicholas Platt), and 2 weeks, to get approval from USAID.

Another potential distraction was the ongoing New People’s Army (NPA) guerrilla movement. The NPA controlled the upper slopes of Pinatubo and was generally suspicious of both the Philippine or American governments. Since we had to do geological reconnaissance and install remote instrument stations on Pinatubo, using logistics from USAID and the Philippine and American militaries, we were concerned that our humanitarian purposes might be misunderstood and that our fieldwork might be blocked and radios taken for other purposes. Personal safety was also a concern. Appropriate contacts with the NPA explained who we were, what was happening, and why our work should proceed.

External distractions might well occur in any volcanic crisis. For example, in the runup to the eruption of Nevado del Ruiz, a bombing at the Supreme Court of Colombia was a major distraction for the national government. Eruption responses in 2020–2021 are all influenced by the COVID pandemic, and although technology is helping to backfill for in-person collaboration, no inanimate tool or AI can substitute for the personal relationships and trust that is required between scientists and decision-makers.

Early Alert

Every eruption after a repose of centuries will have recognizable precursors of indeterminate duration. Scientists will know that the fuse has been lit, but won’t know how long the fuse is. Time is of the essence. An early alert will help scientists to ramp up their monitoring and outreach activities. At well monitored volcanoes, the early alert will come from either ground-based or space-based instruments. At Pinatubo, there was no prior instrumental monitoring, but a small group of Aetas and missionary Catholic sisters living on the NW flank of Pinatubo noticed the small phreatic eruptions on April 2 and promptly went to Manila to report them to PHIVOLCS. What if they had not traveled promptly to Manila? That early alert gave extra days, perhaps even extra weeks of time for further preparations. In the final days of ramp-up to eruption, we were still desperately trying to convince officials, both American and Philippine, that it was time to move, and those extra days or weeks at the start were surely important at the end.

In the Philippines, local government officials (mainly, Mayors and Provincial Governors) have the main decision making authority for mitigation measures, sometimes acting on recommendations from national agencies. That system was already in place and functioning from the start of the Pinatubo crisis. The national Office of Civil Defense (Engr. Dejoras) organized a series of briefings for Governors and Mayors of the provinces surrounding Pinatubo, at which Dr. Punongbayan of PHIVOLCS laid out the hazards and started discussion of the potential need for evacuations. These briefings took place in May, early enough that the local government officials could make reasonable preparations.

Early in any episode of unrest, uncertainty will be high about the cause and about whether an eruption might follow. Most volcano observatories will err on the side of caution and respond immediately. If early unrest turns out to be a false alarm, little is lost, but if a response turns out to be too little or too late, much can be lost. The skepticism that we encountered at Pinatubo was both surprising and challenging but, in retrospect, understandable at any volcano that has not erupted in recent decades. Extra days of preparation, enabled by early alert, will be especially critical at long-dormant volcanoes.

Scientific Judgment of Whether, When, and How Big an Eruption Will Occur

Forecasting of eruptions is rarely simple. Volcanoes are complex systems with many processes, and volcanologists can observe only the surficial symptoms of unrest, not the actual subvolcanic processes themselves. We can study products of past eruptions to infer subvolcanic processes of previous eruptions at that volcano, but there is no guarantee that the same will be repeated. Interpretation of current seismic, geodetic, gas chemical, and other precursors starts with recognition of similar patterns from past eruptions, perhaps even globally, and then on qualitative or occasionally, quantitative interpretation of those precursors. In the case of Pinatubo, we knew that the volcano had not erupted for hundreds of years, so magma in the conduit had likely solidified. There was seismicity, at first 5 km NW of the summit and later, beneath the summit, but we had almost no deformation data (this was before the era of GPS and InSAR). A ten-fold increase in SO 2 emission, from 500 t/d to 5,000 t/d from mid to late May suggested that magma was involved and rising; then, a dramatic decrease in SO 2 emissions occurred in earliest June ( Daag et al., 1996 ).

There were, at the time, no guidelines about what precursors to expect for a VEI 6 eruption. No VEI 6 eruption had occurred anywhere in the world in the era of modern volcano monitoring. All we had was information about the range of precursor activity at moderately large VEI 4 and 5 eruptions, including some like Mount St Helens that were only marginally relevant. When one scales up to a VEI 6, does one simply look for the same, but stronger? In truth, no one knew.

Lessons learned partly at Pinatubo and partly elsewhere point out three potential misinterpretations of monitoring data. First, the earliest reports of earthquakes at Pinatubo, in August 1990 from the same Catholic nuns, were practically forgotten in attention to other aspects of the M7.8 event. After all, the whole central Luzon region had been shaken and stressed by the M7.8 earthquake. When seismicity began again in March 1991 and was determined in early April to be 5 km NW of the summit along a known tectonic fault, it might have been interpreted as being of tectonic origin had it not been for phreatic explosions that occurred just NE of the summit. We know now of many cases, globally, of volcano-tectonic (VT) earthquakes that occur along tectonic faults up to several tens of kilometers away from volcanoes, but are now traceable to local pressurization caused by magma intrusion and/or pressurization of a hydrothermal system beneath a volcano. Pressurization of any confined aquifer along a regional fault will be particularly effective at triggering such “distal VT” earthquakes ( White and McCausland, 2016 ; Coulon et al., 2017 ; McCausland et al., 2019 ). Ray Punongbayan deserves credit for thinking of a possible volcanic association even though the early April 1991 earthquakes were not directly beneath Pinatubo. We have known other instances in which distal VT swarms were dismissed by local scientists, in the Philippines and elsewhere, as being of purely tectonic origin and thus not of volcanological interest. Sometimes, these events are indeed mainly tectonic with secondary volcanic effects, but often, they reflect magmatic intrusion that triggers slip on nearby tectonic faults. At Pinatubo, early acceptance of a possible volcanic association gave added lead time for preparations, and an early call to VDAP rather than to those who work more in tectonic seismology.

A second possible misinterpretation could have occurred with respect to the sudden decrease in SO 2 emission between May 28 and June 5, 1991. Stemming in part back to a volcanic crisis at Soufrière Guadeloupe in 1976, SO 2 emission or lack thereof has been a point of considerable debate. At Mount St. Helens, very low SO 2 emission before May 18, 1980 was interpreted on April 6 by well-known volcanologist Haroun Tazieff, one of the Soufrière Guadeloupe protagonists, as indicating that Mount St Helens would not produce a serious eruption. We had interpreted the increase at Pinatubo through late May as indicating magma ascent, so did the sudden decrease mean that magma had stalled? We were puzzled but interpreted it as a temporary aberration, perhaps from quenching and sealing of the carapace of rising magma. Today, we know that might also have been from scrubbing of SO 2 into groundwater, or mechanical sealing of fracture permeability, or any combination of the three, so that a sudden decrease in SO 2 emission is actually a warning sign, not a reason to relax ( Stix et al., 1993 ; Fischer et al., 1994 ; Symonds et al., 2001 ). This lesson has been reiterated and reinforced elsewhere since 1991, so it is unlikely to be forgotten or misinterpreted in the future. But the generic lesson is this: There may well be other unrest in future crises that is puzzling and easily misinterpreted. The fact that volcanologists still debate the causes of unrest at other volcanoes, e.g., the role of shallow magma intrusions at Campi Flegrei ( Gottsmann et al., 2006 ; Aiuppa et al., 2013 ; Chiodini et al., 2016 ; Troise et al., 2019 ), is a reminder that unrest can still be misinterpreted.

A third possible misinterpretation involved geologic data. Forecasting the size of an impending eruption is even more difficult than the date or time of onset. At Pinatubo, geologic reconnaissance suggested that all previous eruptions were of VEI 6 or larger. Admittedly, we could have missed deposits from smaller eruptions. Had only a small eruption occurred, societal disruption would have been judged unnecessary and scientists would have been severely criticized.

Or, more ominously, our “worst case” scenario could have been too small, and evacuations could have been insufficient. We thought a VEI 6 was Pinatubo’s “worst-case scenario,” and showed that in a hastily prepared hazard map ( Punongbayan et al., 1996 ). Rick Hoblitt of the USGS suggested a possible underestimate based on field work just before the eruption in the Abacan River just outside Clark AB, but it was not until field work after the eruption that we confirmed the underestimate. The Inararo eruption of ∼81 ka left ∼25 km 3 (bulk volume) of deposits, and even the Crow Valley eruption of ∼5 ka left ∼10–15 km 3 of deposit, several times more voluminous than 1991 ( Newhall et al., 1996 ). What we underestimated was the degree to which, after a huge eruption, fresh deposition on alluvial fans will cover and hide the distal reaches of pyroclastic flows.

Were there any other geologic data that could have helped us to forecast the size of eruption? Volcanologists have long known of an association between repose time and size of an eruption that follows. With the benefit of hindsight, we now understand that the 1991 eruption of Pinatubo was as large as it was because of accumulation of “excess” volatiles in discrete bubbles even while the magma was in storage, 6–11 km deep ( Gerlach et al., 1996 ; Mori et al., 1996 ). The descriptor “excess” refers to volatiles from unerupted magma, above and beyond volatiles that saturate the erupted melt. Volatiles are supplied over time along with mafic magma, and when these were not erupted the volatiles accumulated in the upper part of Pinatubo’s dacite magma reservoir, well in excess of saturation, hence as discrete volatile bubbles. The ready availability of this discrete volatile phase, without any further time required to diffuse through melt, is a critical enabling factor for plinian eruptions. It appears that the 500–600 years since the Buag eruption was enough to supply excess volatiles to residual dacite melt beneath Pinatubo. Before the eruption, all we could say was that the latest repose was in the same order of magnitude as previous reposes, as gleaned from hastily collected and analyzed charcoal samples. It was plausible but certainly not proven that Pinatubo would produce another large eruption. Today, with the story of volatile accumulation better understood, we can understand that the 1991 eruption (low-end VEI 6) was among the smaller eruptions of Pinatubo because the ∼600 years repose was among the shortest known reposes—possibly because the 1990 earthquake triggered the eruption before it would have normally occurred. Since the 1991 eruption was at the low end of what might have occurred, our hazard maps turned out to be “just right.” Everything is clearer in hindsight than in the height of a crisis.

What if a larger “worst-case” Inararo or Crow Valley eruption had occurred? The lethal footprints of those eruptions were larger than we realized before the 1991 eruption. As many as several hundred thousand might have been killed. Global effects on climate would have been worse than those of Katmai or Krakatau, but less severe than those from Tambora (1815 CE) or Rinjani (1256 CE).

All of these lessons on forecasting eruptions, and many more, are now being integrated with physics-based models to improve forecasts even more (e.g., Kilburn, 2018 ; Poland and Anderson, 2020 ).

Stochastic or Unpredictable Factors That can Make Even the Best Scientific Judgment Moot

In any episode of magma ascent, there are various forces promoting and inhibiting ascent. A vigorous supply of magma from depth, high volatile contents, low viscosity and low density all promote ascent. Weak magma supply, degassing and associated increases in viscosity, impenetrable strata or density barriers, and tectonic clamping of faults inhibit magma ascent. Almost none of these are directly observable, yet any one or several can spell the difference between magma erupting vs. stalling as an intrusion. In popular jargon, these are tipping points. The balances between promotion and inhibition of magma ascent are delicate, and quite small changes can radically change the outcome. Since the small changes cannot be observed, there is an element of chance (toss of the dice) as to whether magma will erupt. Volcanologists have some ideas about how to tell the difference—e.g., rapid magma ascent and accelerating unrest favoring eruption—but there are cases where unrest simply stops, surprising both scientists and officials (e.g., Geshi et al., 2010 ; Poland, 2010 ; Moran et al., 2011 ).

Based on the fact that seismicity fluctuated but did not start systematic acceleration until early June, the magma rising at Pinatubo could have stalled without eruption anytime up until the end of May ( Harlow et al., 1996 ). Or, if pauses in the ascent were frequent and long enough, the magma could have degassed to the point that only effusive dome growth would occur, without any explosive follow-up. Indeed, the first magma that reached the surface on June 7 did exactly that—forming a dome visible only to those in helicopters—so volcanologists’ credibility was briefly challenged. Over the next few days, though, it became evident that only the vanguard magma was degassed, and that explosive eruptions would follow.

Another stochastic element also came into play in the final days before June 15: Typhoon Yunya (local name, Diding). While the typhoon itself was forecast a few days in advance by the Philippine weather bureau PAGASA, it posed exceptionally difficult challenges in mitigation. Scientists anticipated that ash loading would be exacerbated because wet ash weighs much more than dry. The solution would be to shovel or wash ash off roofs as quickly as it fell. But the last place that anyone wants to be during the combination of typhoon, heavy ashfall, and lightning, is on a roof, shoveling wet ash. Large buildings were natural places of refuge, but their large roof spans also increased the risk of roof collapse. Warnings were given but lost in the noise. Sadly, most of the ∼400 fatalities during the eruption were from collapse of wet-ash-laden roofs where people had taken shelter.

Optimal Balance Between Caution and Decisive Actions, by Scientists and Civil Defense Alike

Scientists are trained to be cautious in their interpretations, and to gather more data until a compelling story emerges. We must satisfy rigorous reviews to publish scientific papers. We demand of ourselves and others a high level of certainty, and that any remaining uncertainty be revealed and preferably quantified. No scientist should ever publish numerical values without including the “±,” typically 1 or 2 sigma standard deviation. A scientist who makes interpretations without enough data risks unshakeable scorn from the scientific community; a reputation as a “quick draw” or “loose cannon” will be difficult to overcome. Those who “cry wolf” too often will lose credibility.

At the same time, volcanic crises demand answers even before all of the data can be collected. A civil defense official or politician will need to make mitigation decisions, and will demand answers from scientists, often before the latter are comfortable making an interpretation. It is a clash of cultures. Scientists who respond to volcanic crises know the dilemma well, and do their best to balance caution vs. giving timely advice. We understand that officials need our advice, but we also need officials to understand that our advice comes with considerable uncertainty.

At Pinatubo, PHIVOLCS and USGS scientists in the field were struggling to understand and forecast activity. Scientists in the field were talking daily, sometimes even hourly, with Dr. Ray Punongbayan, Director of PHIVOLCS. Ray was responsible for nearly all public statements to officials and to the news media, and was also contributing to the science, particularly by air photo interpretation. He understood that the possible events were of such large size that there was no sense trying to fine-tune our advice. Advice needed to be simple and cover what we thought was the worst-case scenario. Ray also understood, better than most of the rest of us, that in the Philippine culture, scientists are expected to know the answer, not to still be searching for it, so it was better for his and our credibility for him to gloss over the uncertainties. He painted a clear, relatively simple picture, with bulls-eye radius-determined evacuation zones that ignored topography, and a jointly-developed alert level scheme that forecast the start of eruption to within the nearest 2 weeks and then 24 h. He succeeded well in this regard, and events later proved his simplifications largely correct. There were moments when those of us in the field thought, whoa, we don’t know that! And when Ray declared the highest alert level on June 9 some of us thought it was premature. But it was not premature for long, and it gave officials and residents several extra days to evacuate.

What if Ray had played the cautious scientist? Given events that transpired, he would have been late on his warnings. And if the volcano had not erupted? Well, it would have been a false alarm, and he could have lost his job. A Philippine weather forecaster lost his job for a lesser error. Ray knew the consequences, and took the personal risk to save others. I might not have lost my job, but I would have earned black marks for risking and “losing” so much of our volcano program’s discretionary budget over a non-eruption. Increasingly, since the L’Aquila earthquake of 2009 in Italy, volcanologists and other natural hazard scientists are also becoming more aware of legal risks in our professions, and the combination of legal threats and scientific scorn might be enough to scare some into being very cautious ( Bretton et al., 2015 ). It is not an easy balance to find.

Civil defense officials and politicians must find a similar balance. In their case, it is between taking adequate precautions without overly disrupting community life. Civil defense officials weigh the costs and logistical feasibility of risk reduction (evacuation, feeding costs, public impatience with community and business disruption) vs. the costs of not mitigating (principally, lives lost). Politicians will do the same, and also consider whether their actions improve or reduce their chances of reelection. Every decision about the timing or scale of evacuations requires officials to decide how much risk to accept. Officials rely on volcanologists to quantify the hazard, and on their political or social advisors to quantify what risks people are willing to take order to avoid disruptions of lives and livelihood. Although a few national standards of acceptable risk have been suggested (for example, Health and Safety Executive (UK), 2001 ), there is no widely accepted reference and most officials seem to base their decisions on semi-quantitative advice from volcanologists and on concerns from various stakeholders including residents and businesspeople.

Ideally, there might be a social contract between volcanologists, officials, and with citizens through their officials, that acknowledges uncertainties in eruption forecasts, discusses acceptable risk, and notes the possibility that one or more false alarms or missed alerts might occur as everyone strives to keep risk within acceptable limits. Where risk is to be quantified, scientists should ask decision-makers about what precision can be used, and whether there are key thresholds of risk that should be flagged. Community meetings help; social media, for all of their warts and noise, also offer some intriguing possibilities for getting the “pulse” of a community in the face of volcanic risk. Social scientists could play an important role by helping decision-makers judge acceptable risk.

Effective Communication Between all Parties

Effective communication between volcanologists, officials, traditional news media (not social media), and residents came into sharp focus after the Nevado del Ruiz disaster. There, much correct information had been sent, but not in forms that resonated with recipients. Volcanologists had provided traditional products like a 2-D hazard map and one-way briefings, but had not provided video or other more graphic depictions of the imminent hazard. There were also breakdowns in communication between neighboring political jurisdictions and, apparently, clergy had not been included. A summary of many cumulative communication failures may be found in Voight (1990) , and Colombian scientists are now much more aware of communication issues than they or any others were previously (Calvache et al., 2021).

At Pinatubo, we faced several challenges in communication ( Punongbayan et al., 1996 ; Newhall and Solidum, 2018 ). The first was time—everything we were doing, from installing monitoring stations to interpreting data and holding briefings and other outreach activities—was fighting against the clock. There were not enough hours in the day. Furthermore, our team was small and none of us was really trained or designated as a communicator. As mentioned earlier, Ray Punongbayan did an outstanding job, through a combination of scientific competence, ability to sketch and simplify, and personality. Others of us who were involved in communicating relied heavily on the rough cut of a video, Understanding Volcanic Hazards, made for the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) by the late Maurice and Katia Krafft after the disaster at Nevado del Ruiz. It illustrates each major volcanic hazard in graphic, even gruesome detail, and this video palpably helped us to convince skeptical audiences. This video was VERY helpful for those of us trying to explain such unfamiliar phenomena as pyroclastic flows, mudflows, ashfall, and the like. We showed and left copies of the Krafft video in nearly all of our briefings. Colleague Jack Lockwood and I also showed it to commanders of the US Pacific Forces in Hawaii, to get a green light for those at Clark AB to evacuate if needed.

In looking back, all of us at Pinatubo were doing everything we could to communicate, with everyone we met formally and informally. We briefed Aeta groups, political leaders from village to national levels, science teachers, Philippine and American military officials, and, informally, even a squad of the guerrilla New People’s Army then operating on Pinatubo. It was just barely enough, again evidenced by skepticism right to up to the eruption. We were not expert communicators. But in the end, our communications plus spectacular VEI 3 eruptions during clear weather on June 12 convinced most skeptics. What if we had a larger, well-trained communication team? We could have done better. We might have given better advice about wet ashfall and roof collapse. And what if Pinatubo had not produced a vanguard dome and VEI 3 eruptions but, rather, gone straight to the VEI 6? For sure, more Aetas would have died, as the evacuations were continuing right up through June 14 and early June 15.

Successful communication can hinge on just a single, critical message, delivered at a single, critical moment. But more often, it is an accumulation of many messages to many parties, spread over time. Many of these needed to be tailored to the audiences—upland farmers, politicians, and military commanders speak different languages and have different concerns. In Figure 1 , one node calls attention to the issue of communication, but in reality, it was not a single event but rather, a continuous process with many chances and degrees of success or failure. It is unlikely that any single miscommunication would derail the whole train, but many miscommunications could sure slow it down.

One miscommunication caused damage but, fortunately, no fatalities. Volcanologists anticipated that the eruption would be large, and also knew that large eruptions produce ash clouds that can blow thousands of kilometers downwind. Smaller eruptions from Galunggung Volcano (Indonesia) had done just that in 1982, causing engine failures in at least 2 jumbo jets, and similar eruptions from Redoubt Volcano (Alaska) had done the same in 1989–1990 ( Casadevall, 1994 ; Guffanti et al., 2010 ). Evidence was mounting that even distal ash could be dangerous for jet aircraft. International concern about ash hazard to aviation was driving a symposium on the topic, advertised and scheduled for early July 1991 in Seattle. Manila air traffic control and airlines operating out of Manila were aware that Pinatubo might erupt, but perhaps not of how far the ash might be blown downwind. More than a dozen Notices to Airmen (NOTAMS) were issued from April 12 up through June 15, the last few indicating closure of airways near Manila, and of the Manila airport. Meteorologists with access to near-real-time geostationary satellite images also knew of the hazard, and some were tracking the ash as it moved west from Pinatubo. To my knowledge, no Significant Meteorological Informations (SIGMETs) were issued with stronger wording about distant hazard, and airline operators were unprepared for the ash they would encounter far downwind from the Philippines. In retrospect, this was a multi-party communication failure, with insufficient warnings of distal ash but also insufficient attention from operators to the front-page stories about Pinatubo. Clearly, communication to other Flight Information Regions (FIRs) in Southeast Asia, and to pilots in those regions, was inadequate, and over a dozen planes flying over Indochina were damaged by ash ( Casadevall et al., 1996 ).

Since the time of Pinatubo, and especially in the past 2 decades, volcanologists have become much more aware of communication issues, and an excellent book by Fearnley et al. (2018) reflects this greater awareness and attention. Calvache et al. (2021) offer painful but valuable insights into the challenges of communication around Colombian volcanoes. Communication is a huge issue for which few volcanologists are well prepared. The sooner we bring in expert help, the fewer miscommunications will occur. These days, observatory teams are adding social media specialists, because of the potential for quick, one-way and even two-way communications with whole communities. The VHS and Beta videotape technology we used at Pinatubo is an ancient artefact compared to today’s options! On the specific miscommunication about ash hazard to aviation, there is now a vastly improved system, with nine Volcanic Ash Advisory Centers around the world, organized through the International Civil Aviation Organization (ICAO) and operating 24/7, in full communication with volcano observatories, meteorologists, air traffic control, and operators.

Concluding Remarks

Much of the literature of counterfactuals imagines disasters much worse than actually occur—worse either by nature or by human failures. The eruption of Pinatubo in 1991 was big enough to be a major disaster, and indeed did cause great immediate and subsequent damage, but the outcome could have been even worse without good forecasts or if mitigation measures were not undertaken. In retrospect, the eruption itself could have been up to several times larger, with major loss of life, or smaller than expected, with minimal damage other than to volcanologists’ credibility (and jobs!). Mitigation of effects from the 1991 eruption was largely successful, but along the “train tracks” toward that mitigation, many things could have derailed or sidetracked the train. A few were matters of Nature, such as stochastic influence on whether and how magma erupted, or external distractions, natural or human. Most, though, were matters of human response to the crisis, from matters of capability and trust, scientific interpretation, communication, and decisions made by civil defense and political officials. Many decisions were judgment calls, made under high uncertainty, and some required balance between reputational caution and taking personal professional risk in order to save others. When uncertainties are high, there is naturally a high chance of disproportionate response, either too small or too large, too soon or too late. It is a tribute to all involved at Pinatubo, especially to the late Raymundo Punongbayan, that the response was as successful as it was. There were many opportunities along the way for the Pinatubo mitigation train to derail, or be slowed down. No one should be complacent or overly confident in a situation like Pinatubo. Only a steady hand and attention to potential failures can steer the train to successful mitigation. Even with this special care, external factors can send a mitigation effort hurtling off the tracks! The mitigation team did (nearly) everything right, AND Pinatubo behaved as expected.

Data Availability Statement

The original contributions presented in the study are included in the article/Supplementary Materials, further inquiries can be directed to the corresponding author.

Author Contributions

The author confirms being the sole contributor of this work and has approved it for publication.

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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Punongbayan, R. S., Bautista, M. L. P., Harlow, D. H., Newhall, C. G., and Hoblitt, R. P. (1996). “”Pre-eruption hazard Assessments and Warnings,” in Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines . Editors C. G. Newhall, and R. S. Punongbayan (Quezon City, PHIVOLCS and Seattle: Univ of Washington Press ), 67–85.

Stix, J., Zapata, G., J. A., Calvache, V., M. L., Cortes, J., G. P., Fischer, T. P., Gomez, M., D., et al. (1993). A Model of Degassing at Galeras Volcano, Colombia, 1988-1993. Geol 21 (11), 963–967. doi:10.1130/0091-7613(1993)021<0963:amodag>2.3.co;2

Symonds, R. B., Gerlach, T. M., and Reed, M. H. (2001). Magmatic Gas Scrubbing: Implications for Volcano Monitoring. J. Volcanology Geothermal Res. 108 (1-4), 303–341. doi:10.1016/s0377-0273(00)00292-4

Troise, C., De Natale, G., Schiavone, R., Somma, R., and Moretti, R. (2019). The Campi Flegrei Caldera Unrest: Discriminating Magma Intrusions from Hydrothermal Effects and Implications for Possible Evolution. Earth-Science Rev. 188, 108–122. doi:10.1016/j.earscirev.2018.11.007

Voight, B. (1990). The 1985 Nevado del Ruiz volcano catastrophe: anatomy and retrospection. J. Volcanology Geothermal Res. 42, 151–188. doi:10.1016/0377-0273(90)90075-q

White, R., and McCausland, W. (2016). Volcano-tectonic Earthquakes: A New Tool for Estimating Intrusive Volumes and Forecasting Eruptions. J. Volcanology Geothermal Res. 309, 139–155. doi:10.1016/j.jvolgeores.2015.10.020

Keywords: mitigation, Pinatubo, eruption forecasting, trust, communication, counterfactual, volcano risk

Citation: Newhall C (2021) Volcanic Risk Mitigation that Could Have Been Derailed but Wasn’t: Pinatubo, Philippines 1991. Front. Earth Sci. 9:743477. doi: 10.3389/feart.2021.743477

Received: 18 July 2021; Accepted: 27 October 2021; Published: 17 November 2021.

Reviewed by:

Copyright © 2021 Newhall. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Chris Newhall, [email protected]

This article is part of the Research Topic

Reimagining the History of Extreme Events

Photo of volcano Mount Pinatubo erupting

Remembering Mt. Pinatubo

A conversation with nasa disasters program associate manager, john murray.

The second-largest volcanic eruption of the 20th century occurred at Mount Pinatubo in the Philippines on June 15, 1991. By far the largest eruption in the past 100 years to affect a densely populated area, Pinatubo produced high-speed avalanches of pyroclastic flows and a cloud of volcanic ash hundreds of miles across. Meanwhile, Typhoon Yunya brought cascading hazards such as flooding and fast-moving lahars when it arrived within 75 km of the volcano during the eruption’s peak activity.

The effects of Mt. Pinatubo’s eruption combined with Typhoon Yunya were devastating. The disaster impacted approximately two million people directly, primarily by widespread ashfall and damaged crops. Reports estimated  $700 million in damage , including $100 million of damages to aircraft flying at the time of the eruption, with the rest a combination of agriculture, forestry and land.

Photo of volcano Mount Pinatubo erupting

Still, because the eruption was forecast by scientists from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and the U.S. Geological Survey (USGS), civil and military leaders were able to undertake massive evacuations and measures to protect property before the eruption. Seventeen ships evacuated tens of thousands of U.S. Department of Defense civilian personnel and their dependents from Clark Air Base and U.S. Naval Base Subic Bay during "Operation Fiery Vigil." Those actions saved up to 5,000 lives and $250 million in property.

NASA Disasters associate program manager John Murray was there. At the time, he served on the Navy's newest aircraft carrier, the  USS Abraham Lincoln, which evacuated 4,400 people from the island in two days. Murray currently serves as an associate program manager for the Disasters program area of NASA's Earth Science Applied Sciences Program and the program's lead response and risk reduction coordinator at NASA's Langley Research Center. We caught up with him recently and asked if he would share some of his recollections of that momentous event 30 years ago and its implications that carry forward to today.

Headshot of John Murray

Q: Thank you for sharing your experience with us, John. What brought you to Mt. Pinatubo during the eruption?

A: At the time, I was Meteorology and Oceanography Officer for the USS Abraham Lincoln aircraft carrier battlegroup and a crew member on the Lincoln. Our weather office advised the ship, the embarked airwing and the admiral’s staff on weather and oceanographic matters. In addition, we put together forecasts for the battle group and conducted pilot weather briefings for aircraft sorties from the Lincoln, which normally cycled every 90 minutes or so, 24/7. We had deployed from Alameda, California and were en route across the western Pacific to the Persian Gulf when we were told to divert and evacuate all the military dependents that were stranded from the eruption of Mt. Pinatubo. The eruption was ongoing as we were steaming in. We had hoped to approach directly from the north to save time, but since Typhoon Yunya was threatening, we went into Subic Bay from the south through the San Bernardino Straits to avoid the storm.

Image: Tropical Storm Yunya arrives about 5 miles away from land in this image taken by the NOAA-12 satellite on June 14, 1991.  The eruption column from Mt. Pinatubo (in dark grey) can be seen through the storm's clouds. Credits: NOAA

Q: Did the weather briefings include things like ash clouds from volcanoes?

A: After Pinatubo erupted, definitely. When we went into the Philippines, we were very concerned about the potential for damage from volcanic ash, so we had an exclusion zone where we didn't fly. Our aircraft engines operated at about 1500 degrees (Fahrenheit), but volcanic glass melts at about 1200 degrees and can very quickly foul them and cause the engine to lose thrust or fail. It's also very abrasive and will score an aircraft windscreen, and in fairly short order, will turn it opaque. It's definitely a threat, so several days before we arrived, we took most of the aircraft into the hangers below deck. We wrapped the engines of the ones remaining on deck in tarps so no volcanic aerosols could contaminate them.

Q: Months before the “big” eruption, what signs told researchers that an eruption was imminent?

A: I wasn’t part of the group that monitored the pre-eruptive activity, so I wasn’t aware of any degassing or whether the size of the lava dome had begun to typically expand before the eruption. These days we use synthetic aperture radar from space to monitor the deformation of the Earth’s surface, so you can see the rate of expansion. We use instruments like the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite and the Ozone Mapping and Profiler Suite (OMPS) on the NASA/NOAA Suomi NPP and NOAA JPSS satellites to detect sulfur dioxide emissions before and after a major eruption. Thermal infrared observations from the latter two satellites also can show us where heat anomalies from magma in the lava dome are occurring. Back then, you had to rely mainly on seismic instrumentation and optical observations. Seismic instrumentation is important; it’s still the primary source of information to monitor volcanic activity. But I’m grateful for the increased insight that we have with Earth-observing satellites compared to 30 years ago.

Q: What did you see as you approached the Philippines?

A: We had to rely mostly on optical imagery to give us an idea of what was going on with respect to the eruption and its coincidence with the typhoon. For the eruption itself, we were receiving messages based on analysis done back in the states by the U.S. Geological Survey and their sources. Compared to today, the technology we had in the weather office was limited to teletype equipment and a Unix machine onboard the ship that received and processed (data from) NOAA Polar-orbiting satellites and ran a rudimentary plume model that wasn't designed to forecast volcanic ash movement. Approaching the island of Luzon, we observed the path where the typhoon intersected with the volcano with great concern. The eye (of typhoons and hurricanes) isn't always reflected at the same location on the ground as it is aloft; it's canted. From what I recall, as we were looking at the imagery, it looked like the volcano was erupting directly through the eye. This was the only information we had. The Navy had a meteorology office near Subic Bay that I'd visited in the past, but it had been effectively shut down because of all the ash fall.

Q: What did you see when you arrived?

A: As we pulled up pierside, it was an eerie experience. The ash had been accumulating over several days, so they had swept most of the roofs and taken road construction equipment and plowed the roads, much like you would plow the roads for snow. I'm from upstate New York, and when I was a kid, I'd look out my bedroom window and see snowbanks all the way down the street. It wasn't a nice bright white snowbank, but it looked much a typical winter scene after a real heavy snowfall. The volcanic ash was dull gray with some brown, and some of the roofs still had significant ash accumulation on top of them.

Ash covers the Subic Bay naval station following the eruption of Mount Pinatubo in 1991. Credits: U.S. Navy/SGT PAUL BISHOP

Q: What were the cascading dangers that Typhoon Yunya brought?

A: Yunya created a real humanitarian disaster. Much of the area around there became totally uninhabitable, so many local inhabitants who could evacuate had gone to other parts of the island. The rainfall was so heavy, however, that the night before we arrived, a large group of people who remained had sheltered in a gymnasium for protection from the hurricane. Once saturated, several feet of ash on the roof became like heavy concrete, and the roof collapsed. There were a significant number of fatalities from that. In addition, there were many structural failures off base due to the weight of the ash on buildings.  The combined effect of the water and the ash was devastating.

Q: Tell us more about the evacuation.

A: The evacuation was all of the military families from the Subic Bay Naval Station, Cubi Point Air Station, and Clark Air Force Base. Some of the military was redeployed to other areas, but the civilian dependents who couldn't get out on their own, had to be evacuated by us. We embarked many of these families on board the aircraft carrier and made two trips from Subic Bay south to the island of Cebu, where the Air Force was flying large transport aircraft out from an old airstrip left over from World War II.

We were taking thousands of people. Interestingly, people come with a lot of stuff, including pets! Down in the hangar bay, there are tie-down spots in the deck every 10 feet or so to secure aircraft. Many now had a dog carrier, cat carrier, or birdcage attached. The U.S. government is very supportive of military families and their dependents, so their pets were also taken on board. People had to go down periodically to comfort, feed, and clean up after them. In addition to a very unhappy Doberman giving birth to a litter of puppies under some yellow gear (aircraft tows), at least one other unusual situation also stuck with me. There were some local people who had been potentially stranded, and it appeared that a few hastily arranged marriages may have occurred. I recall a distraught young lady searching for her husband, and she didn't know his last name! There was no alternative but to get on the intercom like they do when a child wanders off in a department store to ask for a young newlywed named “Ricky” to please report to the quarterdeck because his wife was frantically searching for him.

U.S. military dependents board the nuclear-powered aircraft carrier USS Abraham Lincoln (CVN-72) on June 17, 1991, as they prepare to depart in the aftermath of Mount Pinatubo's eruption. Credits: U.S. Navy/Patrick Muscott

Q: Even with the success of the evacuations, there were still fatalities. The eruption disproportionately impacted the native Aeta, a small aboriginal tribe that numbered about 60,000 before the eruption. What can we do to protect the most vulnerable populations from events such as this?

A: In the more developed world, you can improve infrastructure, right? You don't always have those options in a lot of developing countries. So, the best you can do, I think, is to provide as much assistance is as you can both technically and on a humanitarian basis. The USGS has a Volcano Disaster Assistance Program (VDAP), which is one of our primary collaborators through the Disasters Program. They provide warnings and assessments in the event of a potential eruption or after one has occurred. In the US., the National Institute of Standards and Technology (NIST) has a group that works on building codes. They work closely with the insurance industry. There are parallels in the international community with the reinsurance industry working with different technical and engineering groups to provide consulting to improve infrastructure resilience and resistance to the impacts of things like volcanic eruptions–but more often for earthquakes, hurricanes and floods.

On the humanitarian side, NASA collaborates with a lot of different humanitarian organizations ranging from the Red Cross, FEMA (the Federal Emergency Management Agency, NOAA (the National Oceanic and Atmospheric Administration) the National Weather Service (NWS), National Guard units, the U.N. (United Nations), CEPREDENAC (the Coordination Center for Disaster Prevention in Central America and the Dominican Republic) and many, many other local, state, federal and international institutions to protect communities across the globe throughout the disasters cycle. Just this month, I’d note NASA’s role and support in the establishment of the newest volcano research supersite in Nicaragua , which will increase the region’s access to Earth observation data.

Q: In your role at NASA today, you are at the cutting-edge of volcano research technology. If the folks dealing with Mt. Pinatubo’s eruption in 1991 could have access to today's monitoring equipment back then, what–in your personal opinion–do you think they would wish for most?

A: I really think that the remote sensing capabilities we have from space are the big game-changer these days. Ground-based monitoring hasn’t changed all that much, although the technology is better. Obviously, communication is faster. We had extremely low-capacity communications lines compared to today. The big changes between now and then are instantaneous broadband communications via the internet and satellite remote sensing, primarily via radar sensors. We also didn't have the benefit of sophisticated plume trajectory models like NASA's Disasters Team uses today, such as NOAA's HYSPLIT model and the Langley Trajectory Model (LaTM).

When I was looking at Pinatubo imagery (in 1991), the area was tropical, and there was a lot of convection. It was tough to distinguish between the regular and ash clouds with the naked eye, so we had to be extra conservative. We couldn't take the risk if we couldn't tell the difference between ash, water and ice clouds. So, we had thousands of square kilometers of warning area in which ash was only a fraction of that area. Fast forward to 2007, work with the University of Wisconsin supported by NASA's Applied Sciences Program helped to improve our ability to differentiate between ash and ice clouds. So, now people can go in and look at multi-channel spectroscopy and very easily differentiate between the ash and the water clouds. The International Civil Aviation Organization  (ICAO), an agency of the  United Nations , has also set up a worldwide network of Volcanic Ash Advisory Centers, or VAACS, since the time of the Pinatubo eruption. I'm pleased to say that type of information (differentiating between ash and ice clouds) has been incorporated into the warnings that the VAACs provide.

Q: What other resources does NASA provide now to help people understand and make informed decisions about volcanos with increased confidence?

A: When you look at NASA, you must realize that we are a research agency. We don't have the same responsibilities as those who actually have to provide a forecast or have a statutory responsibility like NOAA for weather, or the USGS for geological information and hydrological information. What we really offer is information that fills critical gaps in technology and in science knowledge. Much of what we have is experimental in nature. Clearly, we have high confidence in many of the things that we produce because we understand the underlying science behind it. We're able to add value and insights based on cutting-edge technologies that may be under development and not yet part of the normal warning process. Our website and the Disasters Mapping Portal are good places to see how people use NASA products to inform disaster risk reduction and response.

Q:  Considering the next 30 years, what do you anticipate will be the next major innovation in volcanology research?

A: The launch of more Synthetic Aperture Radar satellites, such as the upcoming NASA/ISRO SAR ( NISAR ) mission scheduled to launch in January 2023, will be a game-changer. I could see hints of this advance in our NASA Disasters Program's recent use of the Japanese Space Agency's ALOS-2 satellite in monitoring the lava dome expansion of LaSoufrière volcano on the Caribbean Island of St. Vincent. We did this for several months before its eruption this past April. Increasing the frequency and number of observations like this may also aid the development of prediction models, which currently are only used for research purposes because they do not yet accurately predict the time or magnitude of an eruption. I'm also excited about the increasing involvement of the commercial sector in space, which will hopefully make observations such as these and others more ubiquitous in the future.

Q: What else comes to mind when reflecting on the significance of the Mt. Pinatubo eruption?

A: Everyone always thinks about the proximate spatial and temporal impacts of major eruptions, but in the long term, understanding the impact of volcanoes on climate change is another important aspect. Average global temperatures are normally cooler after significant eruptions because less solar radiation reaches the lower atmosphere in their aftermath. Sulfate aerosols a from the eruption plume ejected into the stratosphere and stayed there for more than five years. NASA’s Langley Research Center, where I’m based, played a key role in monitoring that using data from SAGE II . Mt. Pinatubo had a significant impact on ozone loss in the stratosphere and is the only major eruption we have on record showing the climate impacts of volcanoes. (Editor’s note: Because of the sunlight-absorbing effect of the aerosols in the stratosphere, scientists measured a drop in the average global temperature of about 1 degree F [0.6 degrees C] over the 15 months following the eruption.)

Ashfall from Mount Pinatubo's 1991 eruption covers vehicles near Clark Air Base in a snowlike blanket of tephra deposit on June 16, 1991. Credits: USGS/R.P. Hoblitt

Q: What final thoughts would you like to share with us?

A: Major eruptions generate public awareness of various societal vulnerabilities and other impacts, even climate change. They are often what motivates policymakers to engage the science community to redouble its efforts to close critical knowledge gaps to help understand, mitigate or prevent impacts of future events. However, it is essential not to wait for an imminent eruption to put focus on volcano research. It is always important to continue to strive to improve our science capabilities to observe, forecast, assess, respond, recover and reduce the risk for disasters.

  • Learn more about John Murray
  • Learn more about how NASA aids risk reduction, response, and recovery for volcanoes. 

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Looking back: When Mount Pinatubo blew its top

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This is AI generated summarization, which may have errors. For context, always refer to the full article.

Looking back: When Mount Pinatubo blew its top

MANILA, Philippines (UPDATED) – Leonor Pineda, a resident of San Fernando, Pampanga, could still remember the thrill she felt 27 years ago.

STEAM EXPLOSIONS. Steaming vents from different parts of Mount Pinatubo start to appear days before the cataclysmic eruption. Photo from Phivolcs

In April of that same year, Sister Emma returned to Phivolcs to report again about their new observation, this time, of steam explosions in some parts of Mount Pinatubo.

Seismic networks were then set up in the vicinity to locate the source of the swarms, according to Sevilla. Experts from the US Geological Survey (USGS) also came to help the agency.

THICK ASH. Eruption column from Mount Pinatubo on June 12, 1991. Photo from Phivolcs

Remembering the 1990 Luzon Earthquake

BURIED. A school buried by lahar flows. Photo from Phivolcs

Major lahar flows continued to affect nearby cities for the next 6 years. Even today, minor lahar flows still affect some provinces during the Habagat (southwest monsoon) season, Abigania said.

Early evacuation

Despite the extent of the destruction, the number of casualties from the Mount Pinatubo eruption was relatively low, according to Sevilla.

Given an increasing number of people living in areas near volcanoes, the death toll from volcanic eruptions in the 20th century could potentially reach thousands. Pinatubo, despite being one of the largest, had less.

Here is a list of some of the most devastating eruptions of the 20th century:

According to Phivolcs data, the 1991 eruption had affected about 1.25 million inhabitants. 717 people lost their lives – 281 of whom died indirectly from the eruption, 83 from lahars, and 353 from exposure to diseases at evacuation centers.

While a number of people died, reports say that about 5,000 lives were saved from the eruption.

“The people living in the lowlands around Mount Pinatubo were alerted to the impending eruption by the forecasts, and many fled to towns at safer distances from the volcano or took shelter in buildings with strong roofs,” according to the USGS report.

As early as April of that year, 2,000 people were already being evacuated, according to Phivolcs data.

“Sa volcano, ang magagawa mo lang diyan ay lumayo ka as far as possible. Hayaan mo lang siyang pumutok pero ang gagawin mo i-evacuate mo lahat ng mga nakatira doon as much as possible,” Sevilla said.

(With a volcano, what you can do is to just move away from it as far as possible. Just let it erupt but you should evacuate everyone as much as possible.)

Close coordination between government agencies and communities near the volcano also helped minimize the number of casualties.

“It really helped that the communities reported what they have observed. They knew their surroundings better, so the information coming from them were really important,” Abigania said. The inputs of experts have certain limits, unless, they too, will give their inputs, Abigania explained.

It would take centuries for Mount Pinatubo to erupt with that same amount of force again. But the Phivolcs reminds the public, especially those living near volcanoes to not become complacent.

mount pinatubo case study

MAP: Active volcanoes in the Philippines

Phreatic or sudden steam-driven eruptions can happen anytime, according to Phivolcs director Renato Solidum. This is why a number of active volcanoes already have designated a Permanent Danger Zone (PDZ), where human settlement is prohibited. (READ: When mountaineers climb active volcanoes )

So far, there are 5 active volcanoes in the Philippines with PDZs: Mayon (6 km), Taal (whole island), Kanlaon and Bulusan (4 km) and Hibok-Hibok (3 km). These volcanoes frequently erupt, according to Solidum.

“As long as the right ingredients are there – heavy and continuous rainfall plus old volcanic deposits – lahar flow is possible. That holds for any other active volcanoes that we have,” Abigania added. –  Rappler.com

Sources: Philippine Institute of Volcanology and Seismology, U.S. Geological Services, The New Wider World by Alison Rae, Neil Anthony Punnet, www.volcano.oregonstate.edu ,  www.volcanolive.com , various news websites

The Philippine Institute of Volcanology and Seismology (Phivolcs) is a partner of Rappler in Project Agos, a collaborative platform that combines top-down government action with bottom-up civic engagement to help communities learn about climate change adaptation and disaster risk reduction. Project Agos harnesses technology and social media to ensure critical information flows to those who need it before, during, and after a disaster.

Project Agos is supported by the Australian Government.

Editor’s Note: In a previous version of this story we said Nevado del Ruiz was located in Mexico. It is located in Colombia, instead. We have corrected the error .

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Mount Pinatubo Case Study (Effects (Economic (The eruption cost 700…

  • The formation of Mount Pinatubo begins with the formation of the chain of volcanoes, the Luzon Volcanic arc. A chain of volcanoes most likely means that a destructive plate boundary must have occurred there, which in fact is what actually happened. The denser oceanic philippine plate subducted under the less dense continental Eurasian plate. The more the philippine plate subducted, the hotter it got and the plate began to melt. This magma goes up through the cracks because of the pressure. The magma creates a row of volcanoes along the fault line
  • an earthquake with a 7.3 on the richter scale happened around 100 kilometers from the volcano, which moved the crust beneath Mt Pinatubo.
  • The eruptions damaged central Luzon, home to about 3 million people. 20,000 indigenous Aeta highlanders, who had lived on the slopes of the volcano, were displaced. About 200,000 people who evacuated from the area around Pinatubo before and during the eruptions have returned home but face the threat of lahars that have buried so many towns and villages. Those who didn't return home had to migrate to Manila
  • the authorities of the Philippine government moved over 60,000 people away from their homes.
  • 75,000 people evacuated. The US air force helped
  • Alert systems were put into place to warn of eruption.
  • The government created multiple shelters for disease control and long term aid
  • More than 400 people died during the eruption, 300 of them died of falling roofs whilst another 100 from mudflow. Disease that broke out in evacuation camps and the continuing mud flows in the area caused more deaths, bringing the total death toll up to 847 people.
  • Many of the school there had were destroyed and thus education was halted
  • The eruption cost 700 million US dollars
  • 650,000 people lost there jobs
  • 1.2 million homes distroyed
  • Heavy rainfall caused multiple buildings to collapse
  • Lots of infrastructure was destroyed
  • The airport had to shut down
  • The Farmland was destroyed by the ash and this made the farmlands useless, and many lost there jobs because of it
  • The volcano was so strong that it created a huge crater now known as lake Pinatubo as it filled up with water.
  • Fast flowing volcanic mudflows (lahars) caused a lot of erosion effecting many things like rivers bridges ect.
  • Volcanic ash is blown in all directions over very long distances, destroying fields and buildings.
  • The sulfur dioxide also caused acid rain which killed ecosystems and damaged buildings.
  • 20 million tons of sulfur dioxide were injected into the atmosphere in Pinatubo's eruption, and the release of the gas cloud around the world caused global temperatures to drop by 0.5°C
  • 15th June 1991
  • South East Asia, Philippines, the island of Luzon. It is in the middle of the Eurasian and Philippine plate it is part of the chain of volcanoes known as the Luzon volcanic arc.
  • On April 2nd the volcano showed signs of volcanic activity, which slowly became stronger. Sulfur dioxide started to be released by the volcano. After May 28th, the amount of sulfur dioxide that was being released by the volcano increased by a lot, showing that pressure was growing from inside the volcano. On June 15th, the eruption began
  • It generated an ash column that was over five km high
  • The eruption produced high-speed avalanches of hot ash and gas, mudflows, and a cloud of volcanic ash.
  • Mt Pinatubo is created by the Eurasian plate subducting underneath the Philippine Sea Plate. The two plates are responsible for the volcano's formation
  • EO Explorer


  • Global Maps

Global Effects of Mount Pinatubo

NASA Langley Research Center Aerosol Research Branch

Image of the Day for June 15, 2001

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Atmosphere Volcanoes

Mount Pinatubo vs Nevado del Ruiz

City of armero, colombia, 1985 (usgs photo).

Country: Philippines

June 15, 1991

Volcanic Explosivity Index (VEI)

Notable Features

• Largest Eruption to affect a densely populated area • Mud flows/avalanches were generated • Volcanic ash cloud of hundreds of miles was developed • Impacts of the eruption continue to this day.

Country: Colombia

November 13, 1985

• Second largest volcano-related disaster of 20th Century • Mud flows/avalanches were generated


Principal Area of Impact

Central Luzon Region

  • Population at Time of Event 6.339 Million Estimated (Region III – Central Luzon, 1990)

Previous Year's Gross Domestic Product (GDP)

$44.31 Billion USD (1990)

Previous Year's Gross Domestic Product Per Capita

$715.30 USD (1990)

• World Bank Group • 2010 Census and Housing Population, Philippines National Statistics Office

Armero /Central Colombia

  • Population at Time of Event 2.113 Million Estimated (Caldas and Tolima Departments, 1985)

$38.25 Billion USD (1984)

$1,299.45 USD (1984)

• World Bank Group • National Administrative Department of Statistics, Colombia

World Bank Group Indicator – Regulatory Quality (Percentile Rank): Not Available World Bank Group Indicator -Government Effectiveness (Percentile Rank): Not Available World Bank Group Indicator –
Rule of Law (Percentile Rank): Not Available World Bank Group Indicator – Voice and Accountability (Percentile Rank): Not Available World Bank Group Indicator – Political Stability and Absence of Violence (Percentile Rank): Not Available

World Bank Group Indicator – Control of Corruption (Percentile Rank): Not Available Transparency International Corruption Perception Index Score: Not Available Transparency International Corruption Perception Index Rank: Not Available


World Bank Group - GINI Index: Not Available Human Development Index Score (HDI): 0.586 (1990) Human Development Index Rank (HDI): Not Available

• World Bank Group • Transparency International • Human Development Report 1990

World Bank Group - GINI Index: Not Available Human Development Index Score (HDI): Not Available Human Development Index Rank (HDI): Not Available

• World Bank Group • Transparency International

Total Affected Population

  • Total Deaths 640
  • Injured Not Available
  • Homeless Not Available

Total Damage

$367.14 Million (In 2015 USD)

• EM-DAT • CPI Calculator

  • Total Deaths 21,800
  • Injured 5,000

$2.2 Billion (In 2015 USD)

With decades of perspective now on these two volcano hazard events, it is clear that the November 13, 1985 Nevado del Ruiz eruption and subsequent lahar (a mixture of ice, rocks, superheated mud, and other debris triggered by a volcanic eruption) qualifies as a true catastrophe for the city of Armero, its principal zone of human impact, of which only a remnant (and relocated) town remains. The June 15, 1991 Pinatubo eruption, however, qualifies as “only” a disaster for its principal impact area because scientific monitoring systems worked with a functioning public alert-warning-evacuation process to avoid massive life loss. Nevado del Ruiz and Armero 1985. Siting what would become the Colombian city of Armero on a solidified lahar from a documented 1845 volcanic event is a classic example of “in harm’s way” exposure, against which very little physical vulnerability reduction was taken or really could be, given its location. Showing precursors a few months earlier, the Nevado del Ruiz volcano erupted on the night of November 13, 1985, melting part of its icecap and sending a lahar down its upper valleys, destroying villages, and then down toward Armero in the larger valley below. The lahar trapped and killed – in minutes – most of the city’s pre-event population of approximately 30,000 (a total EM-DAT death toll of 21,800). Given the “fixed” location of its economic and infrastructure assets, Armero’s only practical risk reduction strategy was an alert-warning-evacuation system for its human population, which utterly failed. While Nevado del Ruiz was in fact being monitored pre-eruption, the technology was not real-time, and the meaning of the data was variously interpreted, misinterpreted, and even denied. As Voight (1990: 383) summarized: The catastrophe … was caused, purely and simply, by cumulative human error – by misjudgment, indecision and bureaucratic shortsightedness. In the end, the authorities were unwilling to bear the economic or political costs of early evacuation or a false alarm, and they delayed action to the last possible minute. Catastrophe was the calculated risk, and nature cast the die…. Armero could have produced no victims, and therein lies its immense tragedy. Pinatubo 1991. Mt. Pinatubo had been relatively dormant for more than 500 years, but after some earlier warning signs, it erupted massively on June 15, 1991, killing a reported 640 people (EM-DAT). Despite a relatively large human exposure that had built up over many decades in the predominantly agricultural areas around the volcano, where soil is exceptionally and attractively fertile, the Pinatubo case saw a very effective alert-warning-evacuation process. Based on real-time monitoring systems, national and international scientific communities, government decision-makers, local communities, emergency management officials, and the Philippine and U.S. militaries achieved an effective consensus and organized timely evacuations: As many as 20,000 lives were saved as a consequence…. Despite considerable uncertainties, the eruption was correctly forecast and more than 85,000 were evacuated…. Although about 200,000 were “permanently displaced” by lahars, only about 400 fatalities are attributed to lahars. Timely warnings from scientists and police helped to keep most people safe (GVM 2015: 18-19). As these two cases illustrate, not much can be done about volcano risk to most economic and infrastructure assets (they tend to be fixed in place, and vulnerability reduction options are limited in practical terms). For human population exposures, however, much can be accomplished because volcano eruptions usually show precursors. The key takeaway for our equation is thus about the importance to human life safety of effective and real-time monitoring and data interpretation, and then communication, coordination, credibility, and trust between (a) the scientific community, (b) emergency management officials, (c) political authorities, and (d) the likely most affected public. Cited References: Global Volcano Model (GVM). International Association of Volcanology and Chemistry of the Earth’s Interior Global volcanic hazards and risk, Technical background paper for the UN-ISDR Global Assessment Report on Disaster Risk Reduction 2015 - Richard S. Olson, Ph.D.

Within hours of Mount Pinatubo's explosive June 15, 1991, eruption, heavy rains began to wash the ash and debris deposited by this explosion down into the surrounding lowlands in giant, fast-moving mudflows called lahars. (Credits: USGS)

mount pinatubo case study

A huge cloud of volcanic ash and gas rises above Mount Pinatubo, Philippines, on June 12, 1991. Three days later, the volcano exploded in the second-largest volcanic eruption on Earth in this century. Timely forecasts of this eruption by scientists from the Philippine Institute of Volcanology and Seismology and the U.S. Geological Survey enabled people living near the volcano to evacuate to safer distances, saving at least 5,000 lives. (Credits: USGS)

mount pinatubo case study

The Luzon Region is where Mount Pinatubo is located, in the northern part of the country. (Credits: University of London Press, 1950, p 336)

mount pinatubo case study

Prior to the 1991 Mount Pinatubo Explosion, the Central Luzon Region was hit by a 7.8 Mw earthquake. The earthquake was strongly felt in Metropolitan Manila, destroying many buildings and leading to panic and stampedes and ultimately three deaths in the National Capital Region. Most of the fatalities located in Central Luzon and the Cordillera region. (Credits: midfield.wordpress.com)

mount pinatubo case study

A village devastated by a mud flow during the eruption of Mt. Pinatubo (Philippines) in June 1991. (Credits: Aventurier/Loviny/Gamma, Paris)

mount pinatubo case study

Map showing hazards expected from an eruption of Nevado del Ruiz, Colombia. Such a map was prepared by INGEOMINAS (Colombian Institute of Geology and Mines) and circulated 1 month prior to the November 13, 1985, eruption of Nevado del Ruiz. Map shows danger from mudflows in the valley occupied by the town of Armero, Colombia, as well as areas affected by the hazards that resulted from this eruption. Circle denotes 20-kilometer limit." (Credits: USGS)

mount pinatubo case study

Picture of City of Armero before the impact of lahars. Armero was located in northern part of the Tolima Department. (Credits: El Tiempo)

mount pinatubo case study

Prior to the Nevado del Ruiz event, between November 6th and 7th, the Justice Palace in Bogota was under siege by the M-19 guerrilla. Back in 1985, Colombia was in the middle of an internal conflict with the guerrilla and a drug war that affected the stability of departments and the government as a whole. (Credits: ElPais.com.co)

mount pinatubo case study

Many families were broken after the incident and children were left orphans. (Credits: El Tiempo)

Footage of Mount Pinatubo explosion from different locations. (Credits: Anonymous)

mount pinatubo case study

Clark Air Base in Philippines, located less than three miles from Angeles City. Footage from June, 1990. (Credits: SSgt Joe Hodges)

mount pinatubo case study

mount pinatubo case study

This is a video in June 1993 traveling north from Dau to Mabalacat towards Bamban. There used to be a bridge in Mabalacat to cross traveling north into Tarlac province. The bridge was destroyed. (Credits: Joseph Gaffney)

Mount Pinatubo effects throughout Philippines. Manila, the capital of Philippines, was affected by the ashes of the eruption, affecting residents, transport and communications. (Credits: )

mount pinatubo case study

The science behind a volcano. The Colombian Geological Service responsible agency conducts ongoing analysis of the Nevado del Ruiz Volcano. (Credits: Streva Project)

mount pinatubo case study

This documentary illustrates the nature of the eruption of the Nevada Del Ruiz Volcano in 1985 and the effect this eruption had on the surrounding areas.

mount pinatubo case study

mount pinatubo case study

Documentary with testimonies of survivors of the November 13 eruption of Nevado del Ruiz in Colombia. The explotion melted the volcano’s icecap, sending a wall of mud, rock and debris powering down the volcano’s slopes. This ‘avalanche’ killed 23,000 people, many woken from sleep only seconds before it hit. The harrowing imagery from this eruption sent shockwaves around the world, but 30 years on, it becomes easy to forget. Many people live far from the volcano in the lush plains and valleys, but they were inundated during that event. (Credits: Streva Project)

mount pinatubo case study

mount pinatubo case study

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Mt Pinatubo Case Study

This caused the shaking and squeezing of the Earth’s crust beneath the volcano. At Mount Punctuation, scientists recorded a landslide, some local earthquakes, and a short-lived increase in steam emissions from a pre-existing geothermal area, but otherwise the volcano seemed to be undisturbed.

In March and April 1991, however, magma started rising towards the surface from more than 20 miles (32 SMS. ) beneath Punctuation. This triggered more small earthquakes and caused powerful steam explosions that blasted three craters on the north side of the volcano.

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Thousands of mall earthquakes occurred beneath Punctuation throughout April, May, and early June 1991 , and many thousand tons of noxious sulfur doodle gas were also emitted by the volcano. Scientists had been able to forecast Pantsuit’s 1991 eruption and this resulted in the saving of many lives and much property. Commercial aircraft were warned about the hazard of the ash cloud from the June 15 eruption, and most avoided it.

Although much equipment was successfully protected, buildings on two U. S. Military bases in the Philippines–Clark Air Base and Cubic Bay Naval Station?were heavily damaged by ash.

Nearly 20 million tons of sulfur dioxide were injected into the stratosphere and the spread of this gas cloud around the world caused global temperatures to drop temporarily (1991-1993) by about 0. ICC.

About 20,000 Eat highlanders, who had lived on the slopes of the volcano, were completely displaced, and most still Walt In resettlement camps for the day when they can return home. About 200,000 other people who evacuated from the lowlands surrounding Punctuation before and during the eruptions have returned home but face continuing threats from Lars (minnows) Tanat nave already Durable numerous towns, villages Ana Title

On June 7th 1991, the first magma reached the surface of Mount Punctuation but because it had lost most of the gas contained in it on the way to the surface, the magma merely oozed out to form a lava dome. However, on June 12th, large amounts of gas-charged magma reached the surface and exploded in the volcano’s first spectacular eruption. When even more highly gas charged magma reached Pantsuit’s surface on June 1 5th, the volcano exploded in a massive eruption that ejected more than 5 cue. SMS.

Of volcanic material. The ash cloud from this huge eruption rose 22 miles (35 SMS. ) into the air.

A blanket of volcanic ash and larger pumice pebbles blanketed the countryside. Fine ash fell as far away as the Indian Ocean, and satellites tracked the ash cloud several times around the globe.

Huge avalanches of red hot ash, gas, and pumice fragments called parasitic flows roared down the sides of Mount Punctuation, filling the deep valleys with fresh volcanic deposits as much as 660 Ft. (200 m. ) thick. The eruption removed so much magma and rock from below the volcano that the summit collapsed to form a large volcanic depression or caldera 1. 6 miles (2.

5 SMS. ) across.

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  1. Remembering Mount Pinatubo 25 Years Ago

    The world's largest volcanic eruption to happen in the past 100 years was the June 15, 1991, eruption of Mount Pinatubo in the Philippines. Bursts of gas-charged magma exploded into umbrella ash clouds, hot flows of gas and ash descended the volcano's flanks and lahars swept down valleys.

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    1. Volcanic Eruption - Mount Pinatubo 1991: After 500 years lying dormant in June 1991 Mount Pinatubo erupted on the island of Luzon, it being the second biggest in the 20th century. It was caused by: The subduction of the Eurasian plate beneath the Philippines plate along the destructive plate boundary to the west of Luzon.

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    Learn about the second-largest eruption of the 20th century that occurred on June 12, 1991, at Mount Pinatubo in the Philippines, and its consequent impacts on buildings, infrastructure, agriculture and emergency management. Find out how the USGS and other agencies responded to the eruption and mitigated the ashfall hazard.

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  7. Lahars of Mount Pinatubo, Philippines, Fact Sheet 114-97

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    Nearly 20 million tons of sulfur dioxide were injected into the stratosphere in Pinatubo's 1991 eruptions, and dispersal of this gas cloud around the world caused global temperatures to drop temporarily (1991 through 1993) by about 1°F (0.5°C). The eruptions have dramatically changed the face of central Luzon, home to about 3 million people.

  9. Impacts of the Eruption of Mount Pinatubo on Surface Temperatures and

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  10. Volcanic Risk Mitigation that Could Have Been Derailed but Wasn't

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    Published. Tuesday, June 15, 2021. The second-largest volcanic eruption of the 20th century occurred at Mount Pinatubo in the Philippines on June 15, 1991. By far the largest eruption in the past 100 years to affect a densely populated area, Pinatubo produced high-speed avalanches of pyroclastic flows and a cloud of volcanic ash hundreds of ...

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  13. Cultural Influences on Disaster Management: A Case Study of the Mt

    This article analyzes disaster management before, during, and after the 1991 Mt. Pinatubo eruption in the Philippines. This was one of the biggest eruptions in the past century and one with important lessons for present-day disaster management. Different ethnic groups in the Philippines were affected by this disaster.

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  23. Mt Pinatubo Case Study

    Mt Pinatubo Case Study. This caused the shaking and squeezing of the Earth's crust beneath the volcano. At Mount Punctuation, scientists recorded a landslide, some local earthquakes, and a short-lived increase in steam emissions from a pre-existing geothermal area, but otherwise the volcano seemed to be undisturbed.