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Volcanologists discuss high-risk volcanoes

This village northeast of Sinabung volcano is covered in ash. Photo: Dr Richard Roscoe

Published February 6, 2014


Mount Sinabung, whose eruption over the weekend killed more than a dozen people and destroyed homes and farms, is just one of many volcanoes around the world that are located in populated areas.

Other examples include Mount Vesuvius in Italy, Popocatépetl in Mexico, the Cascade Volcanoes in the United States, and more.

UB volcanologists Michael Sheridan, professor emeritus of geology, and Alison Graettinger, postdoctoral researcher at the Center for GeoHazards Studies, talk about the risks surrounding some of the world’s most dangerous mountains and how communities in these areas can protect themselves.

Are there many volcanoes worldwide located in populated areas?

Michael Sheridan

MS: There are a lot of them. The International Association of Volcanology and Earth’s Interior considers this topic to be so important that they have meetings every few years called “Cities on Volcanoes,” and these meetings take place in actual cities that have the potential for massive damage or disruption in the case of an eruption.

Examples of such cities include Quito, Ecuador. Mount Rainier in the United States is also near the densely populated Tacoma/Seattle areas.

What hazards do communities near volcanoes face?

Alison Graettinger

AG: There’s quite a range. For people who live quite close, they may regularly be dealing with ash on their properties, on crops. You can’t hang your laundry outside so it can be quite the inconvenience even at a small scale.

As the eruption grows, the ash can poison livestock. You can have things like roof collapse due to ash buildup.

Some communities will be in the path of mud flows, which are called lahars — that’s an Indonesian word — and pyroclastic flows, which can reach up to 450 miles an hour. It’s not something you can run or even drive away from. That’s why it’s important to evacuate when you’re told to.

Why do people live around volcanoes?

AG: Those areas have very fertile farmland. The volcanic ash turns very quickly to fertile soil. In countries like Indonesia or Japan, there isn’t much land that isn’t volcanic. Worldwide, we have this constantly increasingly population that needs space and food, and that drives people into areas that are closer and closer to the volcanoes.

If your family lived there for generations, that’s your home and it’s something you don’t want to leave. It’s not a problem unique to volcanoes — people live in Tornado Alley and in earthquake zones.

Why are people reluctant to discuss the possibility of extreme eruptions?

MS: When extremely large events are infrequent, people don’t think that there is a likelihood that it could happen in their lifetime. They would say, “It will never happen while I’m still alive, so I’m not going to be worried about it.”

But such a disaster could actually happen at any time. That’s what I reported about Vesuvius, and that information caused a huge discussion in the Naples community.

Generally, what governments or managers want to hear is that small events are much more likely; they would rather not talk about the others because it could create a panic in local communities. Scientists must follow a narrow path here: Often, they must present the evidence that they determine to be valid, but avoid saying things that would undermine the local authorities’ ability to manage the crisis.

Why is it so difficult to forecast volcanic activity?

MS: Volcanic eruptions are one of the most complex natural phenomena that you can imagine. Weather is much easier to forecast than volcanoes, in terms of intensity, location, timing and duration.

Volcanologists can consider previous eruptive activity, but the actual volcano can always be a surprise: A new type of activity or phenomenon could happen like never before. One example is the 1980 “blast” at Mount St. Helens, where many people died even though the U.S. Geological Survey had a very cautious hazard-reduction plan.

AG: I try and avoid the word predict because that implies more accuracy than we can have. It’ll never be exact. What we do is we try to forecast reasonably: If you know what normal behavior is and you see changes, that can be a sign that something is about to happen.

In some case we don’t get much warning at all, and in some cases you may see signs a few days before. It can be tricky for local authorities because if you tell people to evacuate too soon, they can get very frustrated if they have to stay away for a long time.

What advances have been made in promoting safety in recent years?

MS: One of the major advances in assessing volcanic hazards is using advanced computation and probabilistic approaches to understand the hazards.

There’s a team of people at UB using new statistical models to look at the probability of different volcanic hazards affecting different areas around a volcano and the relative safety of specific sites surrounding a volcano. This kind of modeling can provide useful information for hazard planning and management, but it’s not an exact science.

How can people stay safe?

AG: If local authorities start closing areas, it’s very important to abide by those instructions. Sometimes people don’t want to leave — these are their homes — but it’s important to evacuate. Pyroclastic flows are very rapid so it’s best to be away from the area before they begin.

We have short memories as humans. We forget big storms; we forget when a long time has elapsed since the last big thing. If we don’t see it in our lifetimes or our parents’ lifetimes, it’s difficult to understand the scale of what could happen.

During an eruption that’s already occurring, staying out of valleys and finding high ground is the important thing.