Ustica, Metropolitan City of Palermo, Sicily, Italyi

Regional Level Types
Ustica	Commune
Metropolitan City of Palermo	Metropolitan City
Sicily	Autonomous Region
Italy	- not defined -

Ustica is a small commune embracing the homonymous island, situated in the Tyrrhenian Sea 52 km north of Capo Gallo, Sicily.

The volcanic island of Ustica is the remaining part of a seamount’s peak that emerged from the waters of the Tyrrhenian Sea. Its geological history includes an emersion stage with a subsequent evolution as coastal and subaerial environment. It shows pillow-lavas, hyaloclasta and volcanoclastic facies (which are typical of the interaction between magma and water) as well as subaerial lava flows. The numerous lava flows with a basic composition (after a long quiescence interval) were associated to trachytic products (even pumice blocks) of explosive eruptions, which caused the destruction of the northern part of the island. This depression was later filled in by several lava flows. Furthermore, several dike systems created further volcanic activities in various parts of the island, where tectonic tension features are found. The volcanic activity continued for about 600,000 years in the Middle and Upper Pleistocene with different emission points and changes in the geometry of the superficial eruptive system. When euptive events ended, marine erosion processes became predominant over the island’s constructive ones. The current morphology shows an intense marine abrasion, which has contributed to cancelling the original volcanic forms but has, at the same time, exposed sections of great interest.

From the volcanological point of view, the island is characterised by the presence of: two main volcanic edifices, Mt. Guardia dei Turchi and Mt. Costa del Fallo (ca. 500 ka in age) that produced lava flows and subordinate pyroclastic fall deposits; a tuff cone at Capo Falconiera (130 ka), and a number of small submarine/subaerial eruptive centres (e.g. Case Zacame, Contrada Spalmatore, and Secca Colombara). The hydrovolcanic tuff cone of the Capo Falconiera centre is situated on the eastern tip of the island, where steep erosion cliffs expose a section of this centre. The magmatism has been predominantly mafic, with a single trachytic eruption and dome emplacement at about 424 ka (Romano and Sturiale, 1971; Cinque et al., 1988; De Vita et al., 1998). Textures of mafic rocks are variably porphyritic with phenocrysts of plagioclase and olivine (forsterite) and sporadic clinopyroxene. Fe-Ti oxides are generally found as microphenocrysts in the most differentiated rocks. Plagioclase crystals are generally weakly zoned. Olivine (Fo_83-76) is the most abundant mafic phase. Trachytic pumices contain a few phenocrysts of alkali feldspar, plagioclase and a few biotite and Fe-Ti oxides set in a vesicular glassy matrix.

Fossils

This region is too big to display the fossil list, try looking at smaller subregions.

References

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Ustica
Wikidata ID:	Q192129
GeoNames ID:	6541326