Figure 1 – A: Morpho-bathymetric map of the study area depicting the Graham, Nerita and Terribile banks and the ten or so cones that form the “Graham Volcanic Field”, highlighted in the blue box and then in figure B. Extracted from Cavallaro & Coltelli, 2019.
Figure 2 – Camillo De Vito, 1831, Eruption of Ferdinandea Island
Figure 3 – Image extracted from “Views and Description of the late Volcanic Island off the coast of Sicily”, 1831, by George Walter Smythe. The original is preserved at the British Library.
Figure 4 – Anonymous print of Ferdinandea Island.
Location and maximum height: Sicily, 37°10'10”N, 12°42'09”E; = -9 m above sea level
Total area: ≈ 1.4 km2
Type of volcano: monogenic volcanic field
Prevalent types of eruptions: effusive, surtseyan
Current prevailing phenomena: gas emissions
Start of eruptive activity: 1831
Last eruption: 1831 (1863?)
Activity status: quiescent
What was once Ferdinandea Island is one of the various submerged volcanoes of the Mediterranean Sea which are located in the north-western sector of the Strait of Sicily. It is part of the “Graham Bank” (in international scientific literature called Graham Volcanic Field = GVF), a monogenic volcanic field composed of about ten cones, on average about a hundred meters high from the seabed, including the submarine one from which Ferdinandea Island arose. The cones are distributed along an alignment extending for about 12 km in a NS direction, located 40-50 km off the coast of Sciacca (AG).
Together with the islands of Pantelleria e Linosa Graham Bank is part of a largest volcanic field, little explored, which developed due to active extensional dynamics in the Channel of Sicily (Figure 1).
The submarine cone of Ferdinandea began to erupt on July 7, 1831 and gradually formed a volcanic cone about 65 m high above sea level, just under 300 m wide and with a perimeter of almost 1 km (Figure 2).
The eruption – which ceased in mid-August leaving a small crater in the centre mofette smoking and boiling – aroused a lively curiosity among the adventurers of the time who reached the area to observe and describe the phenomena. From these cruise observations were obtained both the prints depicting the volcano (Figures 3 and 4) both the geological samples of the erupted material which are still collected in some museums and research institutions.
The descriptions report widespread seismicity, a sea with “boiling water” and from which toxic fumes rose, as well as an explosive eruption visible from the ground (Sciacca, Menfi, Mazzara and Marsala). The island consisted of tephra (fine ash, lapilli and more or less dense scoria and blocks of lava, of a black-reddish color) which turned out to be highly crystalline, of basaltic type and enriched in sodium. On the basis of historical scientific descriptions, such as that of Professor Carlo Gemellaro of the University of Catania, and of the characteristics of the products, the eruptive activity can be defined as of type Surtseyian. Due to the poor coherence of the rocks it was made of and the absence of further eruptive activity, the island was eroded by the sea within a couple of months.
Today the Ferdinandea shoal, submerged at less than 9 meters from sea level, represents the wreck of the island and can be easily explored. In recent times, some rock samples have been taken thanks to the construction of a methane pipeline and investigations of the seabed have been carried out for scientific research.
Useful links:
https://volcano.si.edu/volcano.cfm?vn=211070 (Phlegraean Fields of the Sicilian Sea)
https://www.frontiersin.org/articles/10.3389/feart.2019.00311/full