The Colli Albani is a dormant volcanic area located only 20 km southeast of Rome and, despite myths and legends that have suggested the occurrence of eruptions in ancient Roman times, it has remained completely quiet during the last 36,000 years; however, a growing body of independent geophysical indicators suggest that a new batch of magma is presently accumulating at several km of depth, and it may give rise to a new eruption in the next 1,000 years.
This is the result of a multi-disciplinary study conducted by a team of researchers of the Ingv, in collaboration with the Geology Department of the Sapienza University of Rome, the Istituto di Geoingegneria e Geologia Ambientale – CNR, and the Wiscar Laboratory of Madison University. By means of 40Ar/39Ar dating on the volcanic products the researchers have reconstructed the eruptive history of the Colli Albani during the last 600,000 years and have established that eruptive cycles occurred with a fairly regular average recurrence time, and that the time elapsed since the last eruption (36,000 years) overruns the recurrence time of 31,000 years observed in the last 100,000.
This means that the volcanic area is active and “ready” for a new eruption.
Moreover, new satellite (InSar) data covering the years 1993-2010 revealed ongoing inflation with maximum uplift rates of 2-3 mm/yr in the area hosting the craters of most recent volcanic activity, suggesting that the observed uplift might be caused by injection of new magma. Finally, the researchers have found geologic evidence for a recent (<2000 years) switch of the local stress-field from a previous compressive state, sealing fractures and faults representing potential pathways for uprising of deep fluids, to an extensional state favorable to magma uprising.
These observations highlight that the Colli Albani volcanic area is slowly waking up, and it may be affected by a new eruption in the next thousands years.