Italy has some of the most potentially hazardous volcanoes on Earth. The pair of Vesuvius and the Campi Flegrei around the Bay of Naples are a looming danger for over 3 million people when either of those volcanoes reawakens.
Etna, although not as directly hazardous as Vesuvius, is one of the most active volcanoes on the planet, and its explosive eruptions can impact air travel. New research in Geophysical Research Letters by Fabrizio Marra and others is suggesting we add another to the list of potentially perilous Italian volcanoes: the Colli Albani Volcanic District on the outskirts of Rome.
Now, the Colli Albani (also known as the Alban Hills) has already been identified as having a volcanic past. It consists of a large caldera (10 by 12 kilometers) that was likely created during the Colli Albani’s most active period from 608,000 to 351,000 years ago. That’s when it produced some massive explosive eruptions totaling over 280 cubic kilometers (67 cubic miles!) of volcanic debris.
Since then, activity has calmed down, with a period from 309,000 to 241,000 years ago that was dominated by strombolian eruptions and lava flows (think Etna). The area’s most recent activity has been mainly small explosive eruptions of less than 1 cubic kilometer each, forming small cones or maars (pits).
This change in behavior is good news for Rome, because the Colli Albani appears to be more regular in the spacing of its eruptions than most volcanoes. In their new study, Marra and team identify dormancy and recurrence intervals for the Colli Albani that, since 608,000 years ago, have varied from 29,000±2,000 to 57,000±4,000 years, averaging 41,000±2,000 years between eruptions and 38,000±2,000 years between periods of renewed activity (see below). If you look at the last 100,000 years (Caution: small sample size!),
Marra and others argue that the recurrence interval drops to ~31,000 years. Considering it has been 36,000 years since the last eruptions, they claim that the Colli Albani might be ready for new eruptions.
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