Erupting to Applause

This story by Roger Slavens originally appeared in the Winter 2017 Issue of Georgia Tech's Alumni Magazine.

THOUGH VOLCANIC ACTIVITY of some form or another happens daily on our planet Earth, explosive eruptions of ash and pyroclastic matter—like those recently spewing from Bali’s Mount Agung—are a fairly rare occurrence. So it should be no surprise that Josef Dufek and his fellow volcanologists are excited by the opportunity to watch the fireworks and learn something new. An acclaimed expert on magma, fluid mechanics and the detonative dynamics of volcanoes, Dufek serves as professor and associate chair in the School of Earth and Atmospheric Sciences, where he teaches a number of courses and regularly leads students in field research. The Alumni Magazine thought it would be a blast to talk to Dufek about his work at Tech and find out if we’re all inevitably doomed to die under mounds of volcanic ash and lava.

1. WHAT'S YOUR SPECIFIC EXPERTISE WHEN IT COMES TO VOLCANO SCIENCE?

My training really is in fluid dynamics; in particular I’m trying to understand how fluids play a role in distributing energy—from the crust of the earth upwards. I look at the magma system below the ground and how it interacts with geothermal fluids and subsurface rocks. But probably the majority of my time is spent studying how volcanoes erupt, what causes them to erupt, and then—once they erupt—what the likely outcomes are. I’m most fascinated with explosive eruptions, like the one going on in Bali right now. 

2. HOW CAN YELLOW JACKETS PURSUE THE STUDY OF VOLCANOLOGY AT TECH?

We have an intro level class called Natural Hazards that’s fairly broad to start them off. But, more focused, we have a class called Physical Volcanology that really dives into the physics of volcanoes. It draws a lot of earth science majors but also many from engineering disciplines, most notably aeronautical engineers who are interested in how volcanic ash affects flight. We also teach a field course that’s called Field Methods in Volcanic Terrains that’s taught every year, and faculty and students travel to different volcanic sites every year. We often go to the Pacific Northwest, Northern Arizona and California, but we’ve also traveled farther afield to places like Mexico and Greece. 

3. IS THAT EVERYTHING?

Those are the big courses but there are many related offerings such as Geodynamics, that explores how large earth motions are dictated by energy in the earth, and an Intro to Geophysics class. I teach Fluid Mechanics as well. So there’s actually quite a breadth of things that touch upon volcanoes in one way or another. An undergraduate at Tech who is really interested in volcanoes would typically be an earth and atmospheric sciences major, and then could specialize in Geophysics.

4. WHAT'S INVOLVED WITH YOUR BIG RESEARCH PROJECT IN SOUTH AMERICA THIS COMING JANUARY?

Yes, in Chile. It’s a long-term project that involves a number of different U.S. institutions, but the main ones are Georgia Tech, Wisconsin and Cornell. It’s focused on one volcanic region called Laguna del Maule that first gained interest a few years ago because satellites found it evidence of sustained and dramatic uplift that might indicated volcanic activity. Our project aims to document that activity, and to try to understand better what will happen in the future in this region.

5. YOU MENTIONED THE EXPLOSIVE VOLCANO IN BALI, MOUNT AGUNG. WHAT'S GOING ON WITH THAT? WHY IS IT RECEIVING SO MUCH ATTENTION?

I’m not an expert on this particular volcano, but what’s happening is that magma is rising and volatile species—water, carbon dioxide, sulfur—are exsolving, creating a bubbly, low density magma. So you have this rapid change in density, and the change in buoyancy allows the magma to rise faster and faster, and then if it gets fast enough, it goes past the yield strength of the fluid, the magma, and it’ll break up or fragment. That’s when you get an explosive eruption that releases all that built-up pressure. 

6. IS THIS ERUPTION PARTICULARLY DANGEROUS?

Yes, because the material being released is extremely energetic. There are two main hazards to worry about. One, which is making the news now, is the volcanic ash that’s being expelled into the atmosphere. You can’t fly airplanes through it because the ash is rapidly quenched molten rock, which is really a glass. So if you have a plane up there in the ash, you’d be flying through glass shards, which you can guess would be bad for jet engines. The other hazard, which is why thousands of people are evacuating, is pyroclastic density currents. These are fast-moving, ground-hugging, deadly currents that are akin to a scalding hot avalanche. They’re turbulent, and they can move tens of meters per second—faster than you probably can drive down the roads there. It’s very hard to predict where these flows will go and they are much worse than effusive lava flows, which tend to move slower and more predictably. One other issue that becomes important in a place that gets a lot of rain, like Bali, is something called lahars, or mudflows. From this volcano, you’re ejecting tons and tons of really fine-grain material, and if you add a little water in, that kind of soup is a lahar. They are also very mobile and energetic and capable of causing much destruction in low-lying areas.

7. HOW COMMONPLACE ARE VOLCANOES LIKE THIS?

They’re pretty rare in terms of overall volcanic activity, but they get most of the news coverage. At any given moment, somewhere around the earth there’s something erupting, just not as grand as Mount Agung or in as populated a region.

8. WHAT'S ONE OF THE BIGGEST MISCONCEPTIONS ABOUT VOLCANOES?

Most people think of active volcanoes being these majestic mountains with colorful, relatively tranquil streams of lava flowing out of them, like the ones we have in Hawaii. But there’s a wide range of volcanic activity that doesn’t look or behave like that. The most dangerous ones are those like Agung that can explode violently and eject a lot of ash and create fast-moving, very destructive pyroclastic density currents.

9. WHAT'S THE UPSIDE OF VOLCANOES COMPARED TO OTHER NATURAL DISASTERS?

The thing that we do have an advantage over some other geophysical phenomena—say, earthquakes—is that we often have good warning signs that volcanoes will erupt. With earthquakes, scientists can make some long-term predictions about when faults are likely to fail, but the exact moments are pretty impossible to predict. Volcanoes generally give us more time to evacuate people and prepare for what’s about to come.

10. THERE'S A LOT OF TALK ABOUT SO-CALLED "SUPERVOLCANOES" AND THAT THEY COULD BE MANKIND'S DOOM. IS THAT TRUE?

“Supervolcano” is one of those terms with which volcanologists have a love-hate relationship. What people are talking about is something that’s massive in size and can produce a hundred to a thousand times the volcanic materials of, say, Mount St. Helens produced (about one cubic kilometer of volcanic material). We know that eruptions producing 100 to 1,000 cubic kilometers of material have happened in the past, just not in recorded human history. If you drive across the western United States, you almost certainly have driven by eruption deposits that document past volcanic activity on this scale—the evidence is there at Yellowstone National Park and all across southern Idaho in the calderas, many of which are now buried beneath potato fields. Researchers know that a so-called supervolcano will explode in the future, but there are no signs it will happen anytime soon, or even during our lifetimes. If Yellowstone did erupt on a massive scale right now, the volcanic ash would cool temperatures across the northern hemisphere and settle across the Midwestern U.S., probably destroying much of the country’s food production capabilities. There would be a domino effect globally, but it wouldn’t likely cause mass extinction or our ultimate doom.