BJ Deming

Namesakes: Stromboli

Have you ever wanted to live in a lighthouse?

One of those helpful stations near heavily traveled sea lanes, that is, not something out of a sci-fi or horror story.

Now imagine that the light takes care of itself (because it is a volcanic drama queen that has been sparkling and popping bright lava bubbles at its summit, multiple times an hour, for at least a thousand years) and imagine that your job only involves fishing and growing food in the rich island soil, building a few villages using readily available materials, and gossiping with sailors who drop in for supplies on their way to or from southern Italy via the busy Strait of Messina.

Sweet!

Lots of tourists come, too, by ferry and by hydrofoil because, even though it sounds like a dream, this wonderful place exists in real life at the north end of the Aeolian Islands UNESCO World Heritage site (last week’s Sunday Morning Volcano — Vulcano — is the southernmost Aeolian Island).

Stromboli’s reliable lava bubble-popping spectacle is a tremendous draw.

However, life is never completely warm, fuzzy, and perfect — there is risk here, too.

Pieces of this island/volcano fall into the sea every now and then, causing tsunamis; the last time was in late 2002 — fortunately, not during the tourist season.

No one died and only six residents were injured.

Also, the light in this “house” is temperamental, sometimes exploding without warning.

The last time this happened was in 2019, and lucky sailors recorded it:

Some people on the island were not so lucky.

Life is good on Stromboli Island most of the time, but having to live with the uncertainty gets to residents.

— “It affects people’s mood. When the volcanic activity increases, you notice yourself getting nervous. It’s something common among locals.”

Hazards aside, why does the volcano blow lava bubbles?

Strombolian eruptions

Stromboli lends its name to this particularly dramatic eruption style.

Stromboli in February 2024. The summit is currently closed to visitors because of increased activity.

For seconds to many minutes at a time, a noisy, almost constantly sparking jet of volcanic gas rises a few hundred feet above the vent, along with intermittent bursts of what sometimes look like — and always are — lava-coated bubbles exploding in the volcano’s throat.

The breathtaking show slowly dies away, only to fire up for an encore several minutes to a few hours later — over and over again, until the supply of gas runs out.

Stromboli has been doing this almost daily for many centuries and shows no sign of stopping any time soon.

Volcanologists first recorded that gorgeous but peculiar type of eruption at Stromboli, around the turn of the twentieth century, and the name stuck.

Videos of Strombolian eruptions now come from around the world, not just Italy, since bubble forming/popping conditions are common to most active basaltic volcanoes.

For example, Mexico’s Popocatepetl sometimes alternates its usual vulcanian eruption style with some impressive strombolian episodes:

Probably an unusually gassy packet of magma, at just the right temperature and viscosity, entered the conduit.

And here are two craters at work side by side in the Cape Verde Islands:

At Stromboli, five vents currently are active, though volcanologists have observed as many as fifteen in the past. These vents go off inside three craters that happen to be conveniently located a few hundred feet below the natural viewing platform near Stromboli’s summit called Pizzo sopra la Fossa.

Below this crater terrace is the steep “Fire Stair” (Sciara del Fuoco), where lava and other igneous material occasionally runs down Stromboli’s barren flank to the sea. (This is also where landslides occur, as we’ll see in the next section.)

Fallout from bubble-bursting eruptions seldom reaches the Pizzo, although it is a dangerous place to be when Stromboli’s mood changes.

But never mind that now — we need to find out where the bubbles come from and why they pop.

Let’s answer the second one first. They pop for the same reason that balloons pop at high altitudes — the outside pressure is lower than the pressure inside the balloon.

Since we’re talking highly pressurized magma risen from great depths, pressure at or near Earth’s surface is low enough to pop a volcano’s bubble.

To get that bubble in the first place, conditions inside the volcano’s plumbing system must favor:

  • Formation of a large carbon dioxide gas bubble in the magma. (Do you really want to go into all the geochemistry and geophysics that explains how this happens? Me neither. Let’s just take it as a given that this does occur, especially at volcanoes with basaltic lava.)
  • A column of molten rock for the CO2 bubble to travel through and get coated by as buoyancy rapidly carries it up to the surface, where it bursts, sending blobs and bombs of incandescent material all over the vent area.

“Ooh! Aah!” echoes down from tourists on the Pizzo, whenever authorities let them go up there.

As mentioned, Stromboli is restless right now and the summit is off limits.

Stromboli is very carefully monitored. Authorities sometimes set restrictions so that these cries of wonder don’t turn into “Ooh! Aah! YIKES!”

It can happen.

Stromboli is typically in a steady state as shown by its pattern of multiple bubble bursts, averaging six per hour, but that rate is now up to twelve to fifteen per hour, according to Italian volcanologists.

It’s nice for viewing, but volcano experts know that this increase might not simply be a normal variation.

It might be a clue — the only one that this moody volcanic drama queen is likely to give — that a 2019-style paroxysm is on the way.

Lava flows and paroxysms

Once or twice a decade, Stromboli gets violent for reasons that geoscientists are still trying to understand.

There is little to no warning on monitoring instruments before one of these paroxysms, and it must be terrifying to be close to one, especially when you’re just expecting to see pretty Strombolian fireworks.

Sometimes people panic, injuring or even killing themselves in their hurry to get away.

That is how someone died during one of the last two Stromboli paroxysms, in 2019.

Earlier explosions also have murdered a few people with falling blocks, but most of the injuries reported in the Smithsonian’s Global Volcanism Program (GVP) extensive reports are burns from falling ash.

Okay, that is the grim stuff, so you won’t be tempted to ignore the restrictions and climb Stromboli on your own. Please don’t ever do that.

Pretty lava flows occur here, too — more than twenty of them in the last hundred years, originating from the crater terrace, which is really a small volcanic cone at the top of the Sciara (“Stair of Fire”).

The Sciara, on Stromboli’s northwest flank, is very important, according to volcanologists who also report that the volcano is much more complex in structure and history than it looks at first glance.

Let’s take their word for it and simply point out for now that Stromboli’s other major hazard besides paroxysms — landslides — also happen in the Sciara.

Now here is a video of the 2002-2003 eruption. It shows that 2002 Sciara landslide, as well as just about everything except a typical Strombolian eruption, including:

  • Lava flows
  • Explosive eruptions
  • One of the five strongest paroxysms in the last hundred years — 1919, 1930, 2003, and 2019 twice)
  • Major Sciara landslides that caused big tsunami waves that damaged island villages.

Italy’s National Institute of Geophysics and Volcanology (INGV, in Italian) produced it and it is very dryly narrated in English, but visually and despite the hazardous parts, this video is fun for reasons that are difficult to pin down.

Perhaps it is the incredible helicopter closeups of an erupting volcano; or the videography, especially from the summit, with the sea more than three thousand feet almost straight down below; or perhaps the very professional but human way these scientists approach the eruption.

There are even small outtakes in the end credits, including very shaky images during the landslide sequence (because these geologists knew that part of the Sciara was collapsing, that all of it could go, and that they were standing on its edge — they were running for their lives, but didn’t put that into the final movie!).

Keep an eye out for thanks to someone for their pasta sarde, too (sounds delicious!).

Monitoring:

INGV (English): https://ingv.it/en/stromboli

More information:

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Sources include:

Aiuppa, A.; Bertagnini, A.; Métrich, N.; Moretti, R.; and others. 2010. A model of degassing for Stromboli volcano. Earth and Planetary Science Letters, 295(1-2): 195-204.

Ball, J. 2024. Stromboli Volcano Italy. https://geology.com/volcanoes/stromboli/

Bonaccorso, A.; Calvari, S.; Garfì, G.; Lodato, L.; and Patanè, D. 2003. Dynamics of the December 2002 flank failure and tsunami at Stromboli volcano inferred by volcanological and geophysical observations. Geophysical Research Letters, 30(18).

European Space Agency. 2024. Stromboli Volcano: Historical Views. https://earth.esa.int/web/earth-watching/historical-views/content/-/article/stromboli-volcano/

Métrich, N.; Bertagnini, A.; and Pistolesi, M. 2021. Paroxysms at Stromboli volcano (Italy): Source, genesis and dynamics. Frontiers in Earth Science, 9: 593339.

Ripepe, M.; Rossi, M.; and Saccorotti, G. 1993. Image processing of explosive activity at Stromboli. Journal of Volcanology and Geothermal Research, 54(3-4): 335-351.

Tibaldi, A. 2001. Multiple sector collapses at Stromboli volcano, Italy: how they work. Bulletin of Volcanology, 63: 112-125.

Tinti, S.; Pagnoni, G.; and Zaniboni, F. 2006. The landslides and tsunamis of the 30th of December 2002 in Stromboli analysed through numerical simulations. Bulletin of Volcanology, 68: 462-479.

Wikipedia (Italian). 2024. Stromboli island. Autotranslated by Google: https://it-m-wikipedia-org.translate.goog/wiki/Isola_di_Stromboli?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Edited April 25, 2024.

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