Two tsunamis hit Lake Iseo in medieval Italy, triggered by human-driven sediment buildup and earthquakes, according to a 2026 Nature Communications study.
Tsunamis in Lake Iseo, Italy
A study published in 2026 in Nature Communications reveals that two tsunamis struck Lake Iseo in northern Italy during the Middle Ages. The research, led by Denis Dutykh and Muhammad Naveed Zafar, connects these events to human activities that began in Roman times.Deforestation and sediment buildup
Deforestation, agriculture, and grazing since Roman times increased the amount of sediment reaching Lake Iseo by three times. This surplus created an unstable delta that eventually collapsed during earthquakes.Earthquakes caused delta collapse
The collapse of the delta during earthquakes on January 3, 1117, and December 25, 1222, generated tsunamis. Simulated wave heights for the 1117 event reached about 50 meters, and for the 1222 event, about 13 meters.Historical accounts and delta reform
A 12th-century manuscript describes a lake that left its bed, destroying many castles and fortresses. The delta reformed after the earthquakes, fed by the Oglio River. Today, a simulated wave would reach the northern shore in less than a minute.Modern risks and awareness
Lake Iseo remains less known compared to other Italian lakes, and tsunamis are not typically associated with it. The study highlights how human activity contributed to the conditions for these natural disasters, though earthquakes were the immediate triggers.
