Italy's Volcanoes: The Cradle of Volcanology

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Frequently asked questions about Etna
When was Catania last affected by an eruption of Etna?


If "affected" is understood in a broader sense, such as ash falls, then Catania is very frequently affected by eruptions of Etna. Between 1995 and 2001 ash fell on more than a dozen occasions in the city and beyond, and light ash falls again occurred in late March 2002. If "affected" means that the city was threatened or invaded by lava flows, then the answer is: in 1669. That eruption occurred from a crater at only about 850 m elevation, near the town of Nicolosi, and produced a voluminous lava flow which (after destroying fifteen smaller villages) arrived at the city walls of Catania one month after the beginning of the eruption. Initially the city walls deflected the flow around the southern part of the city into the Ionian Sea, but the failure of small portions of the walls eventually permitted lava to invade the city. Fortunately the lava lobes that entered the city were small and poorly fed, so that they destroyed relatively small parts of it; furthermore it was possible to stop the advance of these lobes by constructing barriers (made of the debris of buildings damaged by the lava) across the main access roads to the center of Catania.

It must be noted in this context that the 1669 eruption is often described in geology text books, touristic guides and newspapers as having caused the total destruction of Catania and the death of up to 20,000 of its inhabitants. This information is completely false. The main lava flow produced by the 1669 eruption did cause some damage in Catania but this was limited to the marginal western and southern parts of the city, and about 80% of the buildings were not harmed. None of the contemporaneous descriptions of the 1669 eruption mentions any fatalities, which they would have certainly done had there been people killed by the eruption. The total destruction of Catania (and many other towns in southeastern Sicily) and the death of about 16,000 people - two-thirds of its inhabitants at that time - was accomplished by a devastating magnitude 7 earthquake which was of tectonic origin and was not related to the eruptive activity of Etna.

Since 1669 there has been no eruption that even remotely threatened Catania; the nearest lava flow in this period came to within about 15 km of the city. However, geological mapping of the urban area of Catania in the late 1990s has revealed that the area now occupied by the city was almost completely covered by lava flows on six occasions during the past 5000 years: about 4500 B.C., in 693 B.C., in 425 B.C., in A.D. 252 (or 253), in the 12th century (this lava flow is often attributed to an eruption in 1381, but was emplaced about 200 years earlier), and in 1669. The most voluminous of these flows is that of 4500 B.C. and occupies much of the central portion of the city area, while the 12th century and 1669 flows essentially remained outside the city as it was in those days. Any future lava flow of similar dimensions would certainly cause extensive damage at least in the outskirts of Catania, but it is possible that the vast quantity of large buildings in those areas would provide a considerable obstacle to a lava flow and prevent it from invading the center of the city.

Next Question: Is there a risk that Etna might blow its top, like Mount St. Helens?

Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"

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