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The myth of the ‘harmless’ volcano and other thoughts on yesterday's Mt. Etna explosion

The myth of the ‘harmless’ volcano and other thoughts on yesterday's Mt. Etna explosion


One of the most active volcanoes in the world

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Mount Etna Erupts In Southern Italy
Mount Etna erupting in 2002.
Photo by Marco Di Lauro / Getty Images

Mount Etna, Europe’s largest volcano, made headlines yesterday when an explosion injured at least 10 people. A BBC crew captured the moment in a harrowing video, showing scorching hot rocks and ash pelleting visitors. None of the injuries were serious — mostly bruises and burns — but the BBC science reporter Rebecca Morelle did tweet that it was “not an experience I ever ever want to repeat.”

Yesterday’s explosion on the Sicilian volcano was unexpected, but not unusual, says Marco Neri, a volcanologist and senior researcher at the National Institute of Geophysics and Volcanology in Catania, Sicily. Mount Etna is one of the world’s most active volcanoes, and since 2011 there have been about 60 eruptions, Neri says. Yesterday, some of that scorching lava got into contact with snow, causing the water’s near-instantaneous evaporation and resulting in the explosion of steam, ash, and rocks.

since 2011 there have been about 60 eruptions

Though Mount Etna isn’t considered a dangerous volcano, it shouldn’t be underestimated either, says Neri, who’s been working on the volcano for almost 30 years. Through the years, some eruptions have threatened the people living around Mount Etna. In 1928, the entire town of Mascali was destroyed. In the early 1990s, a particularly abundant lava flow had to be diverted by creating canals and walls to save the town of Zafferana Etnea. And in 2002, lava leveled many hotels and restaurants in the area.

“Mount Etna gives you a lot in terms of beauty and jobs, because it’s visited by millions of tourists every year,” Neri says. “But once in while, Etna wakes up, asks for the bill, and takes back part of what it gives.”

As the eruptions continue, The Verge spoke on the phone with Neri about why Mount Etna is so active, the danger it poses, and why it’s a perfect natural lab.

This interview has been translated from Italian, and has been edited for clarity and brevity.

What type of volcano is Mount Etna?

Etna is an extremely active volcano, one of the most active in the world. It’s also a very beautiful volcano, characterized by a very diversified and singular erupting ability. There are few volcanoes like Etna; in fact, it’s considered a sort of natural lab. For volcanologists, it’s a wonderful object to study. It’s also considered a harmless volcano [“vulcano buono”] — although the term is improper — because usually its volcanic activity doesn’t kill. Etna’s lava definitely inexorably destroys everything it meets, but it doesn’t kill. Instead, the volcano is a formidable magnet for tourists. For thousands of years, it’s created a kind of stone that’s been possible to excavate and use to build homes. To this day, it’s still an important reservoir of drinkable water. Inside the volcano, there’s a very rich aquifer that gives drinkable water to half of Sicily.

An image of erupting Mount Etna taken on March 16th by the European Space Agency. The surrounding snow has been processed in blue to distinguish from the clouds.
An image of erupting Mount Etna taken on March 16th by the European Space Agency. The surrounding snow has been processed in blue to distinguish from the clouds.
Image: ESA

What do you mean when you say that Mount Etna is a wonderful natural lab?

If you compare it to Hawaii, for example, Mount Etna is a volcano that has a much more variable activity. In Hawaii, there are always very fluid and steady lava eruptions. But Etna has all kinds of eruptions — from effusive eruptions, like in Hawaii, and explosive ones to phreatic eruptions, like the one we saw yesterday. This volcano is peculiar because it’s easy to study it and observe it. We can easily get basically to the top of the volcano by car, especially in the summer. In the winter the situation is a bit different because there’s lots of snow, but even then you just need to have a good pair of legs and you can basically get anywhere. So it’s a good laboratory because it has a very diversified activity — it shows us different types of eruptions — and it’s easily accessible from all of its sides. So we can install a lot of instruments, and even invent and test new instruments on the often-erupting Mount Etna.

What types of instruments does the volcano host?

“it tends to swell like a panettone inside an oven.”

We have very sophisticated and robust instruments, which have been used all over the world for a long time to test volcanic activity. We have seismic instruments, because when magma goes up the conduit, pushing against its walls, it produces fractures and vibrations that get measured. These volcanic tremors increase the closer you get to an eruption, so they’re a good precursor. We also have a sensor that measures the ground’s deformation, because when the volcano is close to erupting, it tends to swell like a panettone inside an oven. We have geochemistry sensors, because the gases always coming out of the top precede the arrival of magma. So by studying the variation of the gas composition, we can foresee what the volcano is going to do in the next days, weeks, and months. It’s really a multidisciplinary approach. In fact, in our institute we have geologists, but also engineers, geophysicists, mathematicians, computer engineers, and they all have a specific job to work together to monitor the volcano.

Why is Mount Etna so active?

Because Sicily is at the center of the Mediterranean Sea, and because the center of the Mediterranean — like Italy, Greece, and Turkey — sits above the meeting place between the African tectonic plate and the European one. This very complex clash of the two plates allows for the creation of volcanoes like Etna, like the Aeolian Islands, the volcanoes in the Lazio region, and also the mountain ranges like the Apennine Mountains and the Alps. The most evident result of this clash manifests itself through earthquakes — for example, the earthquake swarms that are happening right now in Central Italy. So Mount Etna is very active because of the geodynamic conditions of the Mediterranean region and of eastern Sicily that make it that way.

Mount Etna got a new crater recently. How did that happen?

Etna’s dynamics are really something exceptional

Etna’s dynamics are really something exceptional, especially in the last few years. Beginning in 2011, a new summit crater — called maybe with little creativity New Southeast Crater — began growing. This crater has produced at least 50 of the eruptions in the past six years. It’s been growing very rapidly. In about five and half years, it’s become a volcanic cone more than 300 meters high. The last two eruptions — the one that’s going on right now and the one that occurred a couple of weeks ago, and lasted about two and a half days — came from this new crater. The crater has a fracture at its base, from which a lava flow is pouring out, and it’s already moved about 2 kilometers (1.2 miles). The problem is that this lava isn’t flowing directly on the ground, but on a thick layer of frozen snow. [This is what caused yesterday’s explosion at almost 9,000 feet.] It’s a pretty known phenomenon on Mount Etna, because Etna is very active. When these eruptions happen in the winter, they can interact with the snow and produce these types of phenomena.

Mount Etna Erupts In Southern Italy
Members of the Italian Army Guardia di Finanza Mountain Rescue monitor the activity of Mount Etna, 2002.
Photo by Marco Di Lauro / Getty Images

Can Etna’s eruptions kill people?

You really have to try hard to die on Mount Etna. Or you have to be particularly unlucky. Lava flows give you time to escape. Finding shelter during explosions is hard, but again, you have to be very unlucky or very reckless to be hit by one of those explosions. If you get too close to the erupting New Southeast Crater, the risk of being hit on your head is very high, but no one would think of doing that, obviously.

“If a volcano decides to invade a territory, it would inexorably destroy it.”

That said, the fact that the volcano is considered harmless is a myth, because it can create lava flows from one of its side fractures and invade areas, even urbanized ones. About one million people live on Etna’s slopes. That means this is a very urbanized volcano, especially on its southern side. There are some areas in the volcano where erupting fractures open up periodically. If one of those opened up right now, tens of thousands of people would have to be evacuated. If lava invaded those areas, it would destroy everything. You can’t build anything to withstand a volcano. If a volcano decides to invade a territory, it would inexorably destroy it. But it leaves you the time to escape, so, after all, we can consider it a harmless volcano.

Volcanoes produce a lot of carbon dioxide. Is that bad for the environment?

Mount Etna definitely produces a lot of CO2, and especially a lot of SO2 [sulfur dioxide]. This information is often associated to pollution, but without volcanoes and without earthquakes, our planet would be dead because it wouldn’t have an atmosphere. The atmosphere we breathe today was produced by billions of years of volcanic activity, so let’s slow down when we say that volcanoes pollute. Volcanoes are our life. Without volcanoes, we wouldn’t be here having this conversation.