Mount Etna


From a distance, Mount Etna in Italy looks like your basic volcano: tall (towering almost 11,000 feet above Catania, Sicily, in the image above), coming to a point, and showing lots of ancient lava flows on its slopes.

Looks can be deceiving.

Mount Etna actually is a two-for-one deal; a 1200-foot-high stratovolcano sitting atop the gentle curve of a roughly 9500-foot-tall, 36 x 24-mile-wide shield volcano (Hawaii’s Kilauea is another example of a shield volcano). (Oregon State University)

That’s a little mind-boggling. But then, so are many other Earth processes.

Here’s how geologists think the piggy-backing might have happened.

According to Oregon State’s Volcano World website (see references), around 15,000 years ago a series of violent Plinian eruptions at Shield Etna destroyed its summit, turning that into a deep caldera.

Since then, many intense eruptions have filled in the old caldera with Stratovolcano Etna, which continues to be active.

How do experts know this?

A window into Mount Etna’s interior structure opened up some ten thousand years ago, when part of this complex volcano’s east flank collapsed into the sea, forming the Bove Valley.

Sicily and other tsunami-prone Mediterranean shores were much less densely populated then, but that flank failure still must have been a regional catastrophe.

Getting back to our volcano stereotype, and how Mount Etna can’t be taken completely at face value, that’s not really a pointy top up there.

Oh, Etna did have a summit cone in the early 20th century.

Then the volcano changed its activity. As a result, today there are four summit craters.

More than one of these can erupt at any given moment, as this video shows:

Most of the action in this 2013 video — incredibly high lava fountaining, pyroclastic flows, and (at the end) giant gassy lava bubbles bursting — is at the New Southeast Crater. New Southeast Crater opened in 2007 but is actually part of the Southeast Crater (1971).

That second blast is from Etna’s Northeast Crater (opened in 1911).

Etna’s other two summit vents, not seen here, are Voragine (1945) and Bocca Nuova (1968). One of the Vacation Videos shows Voragine erupting in early 2020; the professional volcano photographer was standing on Bocca Nuova’s rim! (Please don’t try that yourself.)

Mount Etna’s changeable behavior, long history of observation (going back to 1500 BC), and accessibility make it a volcanologist’s dream.

And the hazards here, along with that valuable geologic archive of volcanic processes displayed at Bove Valley and elsewhere around Sicily, made Mount Etna an obvious candidate for the Decade Volcano program.

Hazards at Mount Etna

Etna sometimes has flank eruptions. These occur less often than summit activity, but the flank fissures open up at lower altitudes — down where people live.

Lava flows from these side vents have wiped out villages and farmlands more than once.

It isn’t easy to divert moving lava, but sometimes you can.

They even saved the village of Zafferana this way during the International Decade!

Nevertheless, Mount Etna’s intense and frequent activity regularly puts more than a million Sicilians in harm’s way.

As well, the volcano’s emissions interfere with air traffic and occasionally drop ash and noxious gases on places as far away as Greece and Libya.

Today, Mount Etna is one of the most heavily monitored volcanoes in the world. That’s especially good news in light of recent studies showing that its eruptions have been getting more frequent and more productive since the 1970s. (DelNegro et al.; Etna Observatory)

But Etna is good for Sicily, too, boosting the island’s economy in a big way.

Each year, tourists come by the thousands to watch the “big show.” During quiet times, they visit the summit and also explore the lovely human society that people have built on and around Mount Etna.

Vacation Videos:

This is the safest way to explore Mount Etna’s complicated summit:



The following way is dangerous to the point of suicidal. This incredibly beautiful video of Strombolian (gassy) explosions at Voragine Crater was taken in February 2020 by a professional — the rest of us should never get so close to an active vent:



Most visitors to Mount Etna prefer to do something like what’s shown in the following video (with or without the winery stop — the volcano supports many other types of agriculture and crafts, too):



Location:

37.748° N, 14.999° E, Sicily. The GVP Volcano Number is 211060.

Nearby Population:

Per the Global Volcanism Program website:

  • Within 5 km (3 miles): 78.
  • Within 10 km (6 miles): 3,291.
  • Within 30 km (19 miles): 1,016,540.
  • Within 100 km (62 miles): 3,052,770.

Current Status:

As of the time of writing, Aviation Code Orange or Red, depending on activity level.

Eruptions:

  • Eruption styles: Lava flows are the main hazard to people near Mount Etna (DelNegro et al.), though explosions can happen without warning near tourist areas. Etna also has frequent lava fountaining and Strombolian-style explosions that are gorgeous but can cause damaging local and long-distance ashfall.
  • Biggest recorded event: A Plinian eruption in 122 BC damaged Catania so badly that Rome’s Senate gave the city ten tax-free years.

    However, many experts regard the 1669 AD event as Etna’s most destructive eruption in recorded times.

    About one cubic kilometer of lava poured out of the volcano’s flank and traveled through an extensive complex of lava tubes (which kept it hot and flowing) all the way to the sea.

    I can’t verify the death toll, but lava covered at least nine villages and destroyed fields and vineyards. Besides messing up a medieval castle and adding almost a kilometer to the shoreline here, it also overtopped Catania’s wall, damaging some neighborhoods in the western part of the city.

  • Most recent eruption: Ongoing at Voragine, New Southeast, and Northeast craters.
  • Past history: See the GVP for some details of past eruptions.

    If you are into technical views of Mount Etna, this ArcGIS story also has more detailed technical information about its geologic history and hazards.

Monitoring:

The National Institute of Geophysics and Volcanology (INGV) and its Etna Observatory (Italian).

Mount Etna probably keeps observers at the Toulouse Volcanic Ash Advisory Center (VAAC) very busy.

This website has embedded INGV webcams as well as a couple of unofficial Etna cameras.

This is a chapter from my eBook “The Decade Volcanoes and Us,” which is on sale for only $3.50 through April 5th at Google Play and other online stores (not Amazon, though: unfortunately, you have to give them sole distribution rights in order to run a sale).

By the way, since the book was published, Etna has put on quite a show!

For example:



Featured image: Ben Aveling, via Wikimedia, CC BY-SA 4.0.


Sources:

Barberi, F., and Carapezza, M. L. 2004. The control of lava flows at Mt. Etna. (Abstract only) Washington DC American Geophysical Union Geophysical Monograph Series, 143: 357-369.

Branca, S., and Del Carlo, P. 2005. Types of eruptions of Etna volcano AD 1670–2003: implications for short-term eruptive behaviour. Bulletin of Volcanology, 67(8): 732-742.

Brown, S.K.; Jenkins, S.F.; Sparks, R.S.J.; Odbert, H.; and Auker, M. R. 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6: 15.

DelNegro, C.; Cappello, A.; Neri, M.; Bilotta, G.; and others. 2013. Lava flow hazards at Mount Etna: constraints imposed by eruptive history and numerical simulations. Scientific Reports, 3: 3493.

Etna Observatory. 2020. Mount Etna. http://www.ct.ingv.it/index.php/ricerca/i-vulcani-siciliani/etna (via Google Translate). Last accessed April 18, 2020.

Global Volcanism Program. 2020. Etna. https://volcano.si.edu/volcano.cfm?vn=211060&vtab=GeneralInfo. Last accessed April 18, 2020.

Lester, L. 2020. Et tu, Etna? https://eos.org/articles/podcast-et-tu-etna. Last accessed April 19, 2020.

Newhall, C. 1996. IAVCEI/International Council of Scientific Unions Decade Volcano projects: Reducing volcanic disaster. status report. US Geological Survey, Washington, DC. Retrieved from https://web.archive.org/web/20041115133227/http://www.iavcei.org/decade.htm

Oppenheimer, C. 2011. Eruptions That Shook the World. Cambridge: Cambridge University Press. Retrieved from https://play.google.com/store/books/details?id=qW1UNwhuhnUC

Oregon State University: Volcano World. 2020. Etna. http://volcano.oregonstate.edu/etna Last accessed April 18, 2020.

Sable, J.; Houghton, B.; del Carlo, P.; and Coltelli, M. (2001, December). Mechanisms for Basaltic Plinian Volcanism: A Quantitative Study of the Products of the 122BC Eruption of Mount Etna. In AGU Fall Meeting Abstracts.

Stenmark, J. 2020. GNSS and precise positioning to help understand movement in volcanoes. https://www.geospatialworld.net/blogs/a-major-eruption/amp/ Last accessed April 18, 2020.

Wikipedia. 2020. Aeolian Islands. https://en.wikipedia.org/wiki/Aeolian_Islands Last accessed April 18, 2020.

Wikipedia (Italian, via Google Translate): 2020. Catania https://it.wikipedia.org/wiki/Catania Last accessed April 18, 2020.

___. 2020. Etna. https://it.wikipedia.org/wiki/Etna

___. 2020. Linear system of eastern Siciliy. https://it.wikipedia.org/wiki/Sistema_lineare_della_Sicilia_orientale



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