Black-and-white image of Mount St. Helens in 1980 with a billowing ash plume
A Plinian eruption column billows from Mount St. Helens on 18 May 1980. Credit: USGS/Robert Krimmel

Whakaari volcano in New Zealand erupted on 9 December 2019. Although experts had warned for weeks that the stratovolcano was showing signs of unrest, Whakaari remained open to tourism. Forty-seven people were reported to have been on Whakaari, or White Island, when the eruption happened. Twenty-one people have died.

A month later, Taal volcano in the Philippines erupted and spewed a 15-kilometer tall ash plume into the sky. Lava fountains, sulfuric gas, volcanic earthquakes, and more ash plumes followed. Nearly half a million people lived within the 14-kilometer radius danger zone, but only about 70,000 of those people are estimated to have sheltered in evacuation centers. The price of certified breathing masks inflated tenfold after the eruption. The Philippine Department of Agriculture estimated that ash has destroyed roughly US$60 million in crops. Some residents of Taal have lost everything.

It’s been 40 years since U.S. agencies have had to coordinate to keep a major continental eruption from becoming a public health crisis.

“We live on a very, very active planet volcanically speaking,” said Janine Krippner, a volcanologist at the Smithsonian Global Volcanism Program in Washington, D.C. “Those types of volcanoes and the eruption styles that we’ve seen now could absolutely happen in the United States in a wide range of sizes—from White Island being very small [to] Taal being a moderate eruption which has the potential to be bigger,” she said.

It has been 40 years since Mount St. Helens in Washington state erupted. On 18 May 1980, the event killed 57 people, including a volcanologist monitoring the ongoing activity. Since then the volcano experienced some sustained eruptive activity between 2004–2008, largely creating a lava dome beneath the surface, but occasionally sending up some ash. That means it’s been 40 years since U.S. agencies have had to coordinate to keep a major eruption on the mainland from becoming a public health crisis—and experts have found that it’s long past time for a more modern game plan.

It’s About Who You Know…

A lot of recent interagency work has focused on bringing volcano response plans in line with the newest science, response structures, and communication platforms.

Regional and state emergency divisions have kept an ongoing dialogue with the Cascades Volcano Observatory (CVO) on the hazards specific to their areas. The National Science Foundation, NASA, the U.S. Geological Survey (USGS), and the National Academies of Sciences, Engineering, and Medicine conducted a 2-year investigation about how to improve eruption forecasting. Volcanologists, too, have been developing a research coordination network to organize scientific investigations of an eruption, which will inform future response plans.

In 2018, the eruption of Kīlauea in Hawaii became a proving ground for some of these new response networks. Local response teams, USGS, the Federal Emergency Management Agency, and scientists worked together to gather and disseminate information to affected populations. Many of those involved consider the overall response a great success.

Volcano experts meet regularly to discuss eruption forecasting and hazard modeling. But there’s still more work to be done in understanding the health risks form volcanoes and coming up with action plans to mitigate those risks.

“A lot of valuable practical experience is being lost as people retire.”

In the current framework, response would start at the city level, the Centers for Disease Control and Prevention’s Agency for Toxic Substances and Disease Registry (CDC ATSDR) told Eos in a statement. “Local authorities could declare an emergency or disaster and likely would request state assistance. The governor of the state would request federal help if needed. The state request could prompt a presidential declaration and the National Response Framework would activate under the Federal Emergency Management Agency (FEMA).” The National Response Framework, a federal guide to disaster and emergency response, was not in place when Mount St. Helens erupted but has since been used to guide the response to eruptions in Alaska, Hawaii, and the Philippines, ATSDR said.

“At the eruption of Mount St. Helens in 1980…there were many agencies and thousands of individuals involved in all aspects of the disaster,” explained Peter Baxter, a volcano health expert at the University of Cambridge in the United Kingdom. Baxter, who was part of the response team in 1980, said that the eruption was an “unknown entity” in terms of the human health impacts and the practical challenges of ash deposits in community.

“People had to learn from scratch,” he said. “Although some of the lessons have been relearned at other volcanoes around the world since, a lot of valuable practical experience is being lost as people retire.”

“When you do disaster response work, you want to have relationships in place,” said David Damby, who researches the health impacts of eruptions at the USGS California Volcano Observatory in Menlo Park. “During a crisis it’s really hard to meet people and spin up a working relationship on the spot.” If an emergency manager needs a particular piece of information about an ongoing disaster, he said, the key to responding quickly is knowing ahead of time who holds that information.

…And Also What You Know

Before the Mount St. Helens event, the last time a major volcano had erupted in the conterminous United States was the 1914 Lassen Peak eruption in California. Unlike the very active volcanoes in Hawaii and Alaska, active volcanoes in the rest of the country erupt twice a century on average. That makes it difficult to predict the potential health hazards that stem from any one specific volcano.

Two white hands holding volcanic ash
This ash was collected in Randle, Wash., 39 kilometers downwind from Mount St. Helens, after the 1980 eruption. Credit: USGS/ D. Weiprecht

Mount St. Helens spawned a new field of science concerned with the health impacts of volcanoes in the short and long term. As far as case studies go, that eruption is still one of the most extensively studied to date, but it’s still just one example of the type of eruption that might take place. Volcanologists, out of necessity, study examples from around the world to learn more about what the next Cascades eruption might look like.

“There was an eruption of El Chichón in 1982 in southern Mexico, and 1,500 people died from pyroclastic flows,” said Carolyn Driedger. “People were not organizing. They had not built trusting relationships with their local communities at risk.” Driedger, a hydrologist and outreach coordinator at CVO in Vancouver, Wash., also witnessed and responded to the Mount St. Helens eruption.

Then came the eruption of Nevado del Ruiz, Colombia, in 1985 and the Armero tragedy, in which more than 20,000 people in the city of Armero died as a result of mudflows issuing from the eruption.

“Scientists came into [Armero] and tried to talk to local people, but…they weren’t trusted,” Driedger said. “There were vested business interests that were interfering with the messaging. The lahar came through.”

A lahar is a volcanic mudflow, Driedger explained. “It’s debris and mud and boulders and anything the flow can pick up and carry.”

“It was just your worst nightmare. It was a dark and stormy night…when the lahar came through; 25,000 people died.”

“It was just your worst nightmare,” she said. “It was a dark and stormy night, 11:30 at night, when the lahar came through; 25,000 people died. That showed us lahars are huge hazards and getting information about these hazards to people is so important.”

From the 1991 eruption of Pinatubo, Philippines, “we learned a lot about eruption prediction and how lahars can affect areas for generations after the initial occurrence,” Driedger said. “Now we know it’s not over when it’s over.”

Other scientific disciplines aid volcanic research, too. “There’s been a lot done on anthropogenic pollution, for example,” Damby said. “Understanding the impact of particulate matter on people’s health is something that we’re really tuned into because volcanic ash, at the end of the day, is particulate matter.”

Volcanologists have spent decades building a body of knowledge about how a volcanic eruption might make people sick. That knowledge can be of critical use to agencies and health professionals who don’t exclusively deal with volcanoes.

“If you’re a health professional who’s never dealt with a volcanic eruption before—which anyone in the U.S. who didn’t respond to 1980 Mount St. Helens is in that same boat—then it’s nice to be able to have the USGS say, ‘Here’s what we know. Here’s what problems might be. Here’s what we need to test for,’” Damby said.

Evolving Eruptions

Trees marked by a mud line left by a Mount St. Helens lahar roughly 7.6 meters (25 feet) deep
Mud lines on trees mark the height of lahars caused by the 1980 Mount St. Helens eruption. The geologist in this photo is 1.8 meters (6 feet) tall. Credit: USGS/Lyn Topinka

However, predicting an eruption’s hazards is not as easy as saying “Volcano X will produce Hazard X” and “Volcano Y will produce Hazard Y.”

“Volcanic eruptions can evolve,” Krippner said. “They can get bigger or smaller, or they can pause and then continue. The different hazards can change through that time as well and the extent of those hazards.”

Disaster mitigation plans work best when the people at risk understand those risks. “There are areas which are excelling at this, but generally speaking, every single aspect of volcanism seems to be misunderstood,” she said.

For example, simply using the word “smoke” instead of “ash” implies a different set of health hazards and protection measures. “I’d say everything—the terminology, what the hazards are, what they mean for people, what the impacts to people actually are, and how people can stay safe—every single aspect of volcanology has to be better understood by the community,” said Krippner. She noted that official communications about the 2018 Kīlauea eruption were superb.

“What we focus on the most, because it puts the most people in immediate harm’s way, is lahars,” said Brian Terbush, who heads the earthquake and volcano program at the Washington State Emergency Management Division.

“All of our volcanoes have a lahar potential and especially the larger ones with huge glacier cover that have river drainages that go into populated areas, such as Mount Rainier,” Terbush said. “About 80,000 people could potentially be at risk from the lahars.” That’s just those at risk from the most immediate lahars near Mount Rainier, Terbush said. Downriver lahars, some experts say, could endanger more than 100,000 residents, employees, and tourists.

“They are highly destructive,” Driedger added, “so it’s maybe less a health hazard and more a matter of life and death as to your getting out of the way.”

A map of Mount Rainier and the surrounding area marked with the level of potential lahar risk.
An eruption of Mount Rainier would cause lahars to sweep through the surrounding area and toward the Puget Sound. Many of the cities at risk for lahars plan and practice evacuation routes. Credit: USGS

And then, of course, there is volcanic ash. “When ash falls, everything that is covered is impacted and that includes the air,” she said. “Most of the time ash is a nuisance to people, but the people who already have compromised breathing are at risk just as they would be in a place with dense pollution or smoke in the air or a dust storm.”

Volcanologists and emergency responders are using ash dispersion models, like Ash3d, more often. These models use weather data from the National Oceanic and Atmospheric Administration (NOAA) to predict what areas might experience ashfall. Information from NOAA is also needed after an eruption has ended, when ash can be resuspended in the air by wind and continue to endanger people with compromised breathing.

“When an eruption is developing, it’s a very confusing time,” Krippner said. “There’s a lot of conflicting information. Scientists are figuring out what exactly is happening, how big this eruption might be, and what areas are being impacted. The groundwork needs to be done beforehand.”

It’s Not Over When It’s Over

There’s still a lot of work to be done assessing the long-term health impacts of an eruption, including the secondary health impacts that can occur long before or long after an eruption.

Lahar mud line on trees along a river after the Mount St. Helens eruption
A scientist stands on the bank of the Muddy River southeast of Mount St. Helens after the 1980 eruption. Lahars traveled along nearly 220 kilometers of river channels, downing trees and depositing sediment. Credit: USGS/Lyn Topinka

The sometimes-prolonged period of anticipation preceding an eruption can affect the mental health of emergency managers and the at-risk population. “Even before the lahar even happens…there’s the mental stress of knowing what can happen in your beloved community. I don’t discount that as a medical issue,” Driedger said.

Sometimes eruptions build up slowly over months, Terbush added, but sometimes they can escalate in a matter of hours (as happened with Taal). For emergency managers, “just the unpredictability of what’s actually going to happen in an eruption, unpredictability in the timeline and unpredictability of which hazards are going to be impactful… if people are activated and responding, especially media response for all that time, that is going to wear on everybody involved.”

And then there are the myriad of ways that ashfall, lahars, and, to a lesser extent, lava flows, damage critical infrastructure that protects public health. “All the health issues related to relocations—not just temporary evacuation but in many cases final relocation—all those health issues, mental and physical, are applicable with lahars,” Driedger said.

A satellite image of Taal volcano and the surrounding area covered by brown ash
In January 2020, an eruption of Taal volcano in the Philippines released tons of ash that blanketed the surrounding area (brown areas) and damaged US$60 million in crops. Credit: Contains modified Copernicus Sentinel data (2020), processed by ESA, CC BY-SA 3.0 IGO

Ashfall and lahars can cause power outages and leave hospitals and at-home medical devices without power. Wet ash slicks roads and reduces visibility, which can lead to car accidents. Ash can damage a plane’s jet engines, which can hinder evacuation and relief efforts, she added. Local transit authorities, the U.S. Department of Transportation, or the National Guard might aid an evacuation.

Toxic salts, or leachates, can form on ash while its still in the plume and then wash out into groundwater after ashfall. Livestock that eat contaminated grass or soil can get sick or die.

“When you impact personal economies or the economy of the community, you are impacting the health of the people within it.”

“It’s easy to just say ash is ash is ash,” Damby said. “But depending on the composition of the volcano that it erupted from, each ash sample will differ from every other ash sample erupted at a different volcano.” Ash particles around 2.5 and 10 micrometers in size are particularly bad for respiratory health.

Lahars sweep away bridges, buildings, cropland, and forests, and they can also threaten the local water supply for years. “Lahars are the lasting legacy of volcanic eruptions,” Driedger said. Lahar damage to water treatment plants can lead to higher disease rates. Sediment that is resuspended in water and moved down the valley can keep land unsuitable for settling for generations, she said. Agencies like the CDC, National Institutes of Health, U.S. Department of Agriculture, and Environmental Protection Agency might be called upon to assess land and water toxicity and help recovery efforts.

And although lava generally moves slow enough that people can get out of the way, lava flows “can gobble up plenty of good orchard and agricultural space that can impact people,” Driedger added. “When you impact personal economies or the economy of the community, you are impacting the health of the people within it.”

Plan, Practice, Educate, Communicate

In the time between the recent Whakaari and Taal eruptions, there were actually dozens of volcanoes erupting around the world. “So to only have two making the news in a month or so shows you how little people are actually aware of the amount of activity we have on this planet,” Krippner said.

High school students walk along an evacuation route
Students from Puyallup High School walk along their lahar evacuation route during a 17 May 2019 drill. Credit: © Washington State Military Department

Moreover, the unpredictability of eruption hazards presents a challenge for putting together an effective response plan, Terbush said. “Overall, there’s been a shift at the county and local levels with the recognition that any volcanic disaster is going to affect every area a little bit differently.” In areas that were affected by Mount St. Helens and those in the possible path of lahars, there is a cultural awareness of the dangers people might face.

“The city of Puyallup has been excellent [in volcano readiness],” Terbush said. “This is one of the [municipalities] immediately in Mount Rainier’s lahar zone. This past year they evacuated 9,000 students, did a full school drill of 20 schools.” The drill, which took place on 17 May 2019, was the largest volcano evacuation drill in U.S. history.

Volcano hazard work groups throughout the Cascade region bring emergency managers from local, regional, state, and tribal areas together with volcano experts to develop coordinated action plans. More cities every year practice lahar evacuation plans like Puyallup’s. Regional volcano observatories work with policy makers to make land use decisions that consider volcano hazards.

“Volcanic eruptions are pretty much out of the modern-day person’s personal experience.”

But Driedger argues that volcano awareness and preparedness cannot end at the borders of Washington and Oregon. “Volcanic eruptions are pretty much out of the modern-day person’s personal experience,” she said. “Earthquakes you can feel—you know what a rumble is. You understand the concept of flooding or of a wind storm or a snow storm. But with volcanoes, they’re so multifaceted. It takes an extra amount of effort for us to talk about it with people and get them to understand. They fail to recognize that an eruption in Alaska can affect them in Wisconsin.”

“We live in such a global society now, too,” she added. “People come to volcanic areas, and they don’t understand what the threats are….It’s the residents and it’s people who visit there, and it’s the taxpayers who are all funding risk reduction measures in some way or another.”

Raising the base-level understanding of volcano hazards, Krippner said, will also go a long way toward combating the deluge of misinformation that spreads around the globe at lightning speed. In a crisis, finding good information fast saves lives.

“If we have more sources of information that are consistent, easy to find, and [distributed] in more ways,” Krippner said, “and if we have people with larger followings out there that can point to these things rapidly, I think that would begin to solve the problem.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

13 March 2020: This article has been updated to more accurately reflect current and future analyses of the public health implications of a major volcanic eruption in the United States.


Cartier, K. M. S. (2020), U.S. readies health response for the next big eruption, Eos, 101, Published on 12 March 2020.

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