Environment: New study unveils “movements” of Ustica island, off the coast of Sicily
5/7/2018
An over 30 cm rise in the western part of Ustica due to 1906 and 1924 earthquakes: this is what emerges from a swim survey conducted along the 13 km of the island’s perimeter, as part of the ENEA/University of Trieste project Geoswim, foreseeing total mapping of 23 thousand kilometers of rocky Mediterranean coast
The western part of the island of Ustica (Palermo) has risen more than 30 cm, supposedly due to two earthquakes occurred in the first quarter of 1900. This is what emerges from the swim survey conducted to study erosion mechanisms and variations in the sea level along the 13 km perimeter of the island, conducted as part of the ENEA/University of Trieste international scientific Geoswim, also providing for the mapping of 23 thousand kilometers of rocky Mediterranean coast. The results were published in the prestigious international journal “Geomorphology[1]”.
The data on the rise of the western part of the island is based on the discovery- about 2 meters above the sea level-of some crustacean fossils usually living at sea level. Found in a cave on the west side of Ustica, these crustaceans called "dog's tooth" were covered with concretions similar to the stalactites formed by dripping. Thanks to sampling and carbon 14 analysis the crustaceans and the carbonate of the concretion were traced back respectively to 110 and 90 years ago.
“We were able to study all the 13 caves which hide and protect the most interesting data for understanding the history of the island, calculate the variations of the coast and sea level, analyze the mechanisms of erosion and formation of sea grooves, even georeferencing them, that is, combining them with the precise geographical and depth position", Fabrizio Antonioli, geomorphologist at the ENEA Climatic Modeling Laboratory, pointed out.
"In our studies we adopted the innovative method of snorkeling investigation, and conducted for the first time a complete survey of a volcanic island", Stefano Furlani, geomorphologist at the University of Trieste, said. "Furthermore, for the first time in the Mediterranean, some marine furrows, typical of the tidal zone, were discovered on some volcanic rocks in the southern part of the island, showing that the area under examination has been stable for at least 2 to 300 years, the time necessary to their formation ".
"The first seismic sequence which struck Ustica in the spring of 1906 lasted for twenty days and was accompanied by rumbles, rhombuses and electromagnetic discharges, with dramatic consequences for the community.
Even if the shocks did not exceed the 6th degree of the Mercalli scale, they caused collapses and injuries in private homes and public buildings, which forced locals to abandon the island for some time after a heated confrontation between authorities and scientists", said Franco Foresta Martin, Head of the Laboratory of Earth Sciences Museum Isola di Ustica, an institution dealing with educational activities, scientific dissemination and promotion of geo-volcanological research.
"We would like to conduct further investigations aiming at documenting a direct correlation among sea, earthquakes and coastal deformation, but also the need to re-evaluate the seismic risk of the Ustica area, which is subject to frequent medium-low earthquakes.", Foresta Martin concluded.
For more information please contact:
Fabrizio Antonioli, ENEA, Climate Modelling Laboratory, fabrizio.antonioli@enea.it
Franco Foresta Martin (Laboratory of the Earth Sciences Museum, Ustica) labmust.ustica@gmail.com
Stefano Furlani (Trieste University), sfurlani@units.it
[1] Paper : S. Furlani, F. Antonioli, D. Cavallaro, P. Chirco, F. Caldareri, F.F. Martin, M. Gasparo Morticelli, C.Monaco, A.Sulli, G. Quarta, S. Biolchi, G.M. Sannino, S. de Vita, L. Calcagnile, M. Agate (2017). Tidal notches, coastal landforms and relative sea-level changes during the Late Quaternary at Ustica Island (Tyrrhenian Sea, Italy). Geomorphology 299, 94-106. https://www.sciencedirect.com/science/article/pii/S0169555X17304282