Between 1343 and 1456 the island of Stromboli was the source of three great tsunamis, produced by a subsidence of the north-western flank of the volcano.
This is what emerges from an interdisciplinary study in which INGV participated, just published in Scientific Reports of the journal "Nature"
A collapse of the north-western flank of the Stromboli volcano, in the Aeolian archipelago, would be the cause of the three tsunamis that reached the coasts of Campania between 1343 and 1456.
This is stated by the study Geoarchaeological Evidence of Middle-Age Tsunamis at Stromboli and Consequences for the Tsunami Hazard in the Southern Tyrrhenian Sea, recently published in Scientific Reports (https://www.nature.com/articles/s41598-018-37050-3), which was attended by the National Institute of Geophysics and Volcanology (INGV), the Department of Earth Sciences of the University of Pisa, the Italian Universities of Modena-Reggio Emilia and Urbino, the National Research Council (CNR) , the City University and the American Numismatic Society of New York.
"The identification of Stromboli as the source of the tsunamis that occurred in 1343, 1392 and 5 December 1456" - explains Antonella Bertagnini, volcanologist of the INGV of Pisa and co-author of the work - "was possible thanks to an interdisciplinary which has fielded volcanological and archaeological skills. It was known that the island of Stromboli was capable of producing small-scale tsunamis (similar to the one observed on 30 December 2002)" - continues the expert - "however, this work brings to light, for the first time, the capacity of the volcano to produce, even in relatively recent times, tsunamis of a much higher scale and potentially capable of reaching even very distant coastal areas".
The main of the three events, which took place in 1343, would be the cause of the destruction of the ports of Naples and Amalfi, of which the poet Francesco Petrarca was an exceptional eyewitness. The writer was on a mission as an ambassador sent to the Neapolitan city by Pope Clement VI and recounted the incident in a letter, describing the tsunami as a mysterious and violent sea storm that occurred on November 25 of that year and which had caused the sinking of numerous ships in the port of Naples.
"By crossing different methodologies, techniques and skills", continues Bertagnini, "the study also allowed us to reveal how in the first half of the 1300s the island of Stromboli was inhabited and played an important role as a hub for the naval traffic of the crusaders coming from the Italian coasts , Spanish and Greek. Following the collapses responsible for the generation of tsunami waves and a contemporary and particularly intense eruptive activity of the volcano, the island was abandoned from the mid-1300s until the end of the 1600s, when it began its repopulation. The discovery therefore confirms the tsunami danger generated by Stromboli in the Southern Tyrrhenian Sea, although its precise quantification requires further studies aimed at recognizing and characterizing this phenomenon over a longer period of time".
The published research has an essentially scientific value, without immediate implications regarding the aspects of civil protection at the moment.
Extended
Large-scale landslides at volcanic islands are one of the most dangerous geological phenomena, able to generate tsunamis whose effects can propagate far from the source. However, related deposits are scarcely preserved on-land in the geologic records, and are often difficult to be interpreted. Here we show the discovery of three unprecedented well-preserved tsunami deposits related to repeated flank collapses of the volcanic island of Stromboli (Southern Italy) occurred during the Late Middle Ages. Based on carbon datings, on stratigraphic, volcanological and archaeological evidence, we link the oldest, highest-magnitude investigated tsunami to the following rapid abandonment of the island which was inhabited at that time, contrary to previously thought. The destructive power of this event is also possibly related to a huge marine storm that devastated the ports of Naples in 1343 (200 km north of Stromboli) described by the famous writer Petrarch. The portrayed devastation can be potentially attributed to the arrival of multiple tsunami waves generated by a major landslide in Stromboli island, confirming the hypothetical hazard of these phenomena at a regional scale.
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Figure 1 – (A) The island of Stromboli. The red rectangle indicates the studied area. The insert shows the position of Stromboli in the Southern Tyrrhenian Sea. (B) Aerial view of the island taken from the north (Google Earth image) with the position of the stratigraphic trenches dug to search for tsunami deposits and the archaeological site of San Vincenzo. (C) Detail of nearshore area, with trench locations (Map data: SIO, NOAA, US Navy, NGA, GEBCO, TerraMetrics, © 2018 Google).
Figure 2 – Images of the stratigraphic trenches located in Figure 1 (A) Trench 3, (B) Trench 2, and (C) Trench 1. The tsunami deposits are indicated with the abbreviations LTD (lower tsunami, 1343 AD; ITD intermediate tsunami 1392 AD and UTD 1456 AD). The abbreviations T1 and T2 indicate the deposits of paroxysmal eruptions which occurred respectively before and after the tsunami. (D) detail of the Upper tsunami deposit (UTd) and of the T2 deposit. The scale tool is 30cm long, the euro in (A) is 23,25mm. The red arrow in (A) points to a pottery fragment.