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Geologically the Island of San Pietro is composed almost entirely of volcanic rock, with minor outcrops of Quaternary alluvial, aeolian and coastal deposits. In spite of its small size, the island boasts a wealth of geodiversity, with the occurrence of a variety of effusive magmatic rocks formed during the Oligo-Miocene volcanic cycle. During this cycle numerous units were emplaced as well as various, easily distinguishable types of volcanic rocks (rhyolite, rhyolitic ignimbrite, comendite, retinite, diaspore, etc.) and tuff (tuff, pyroclastite, cinerite, ect.), sometimes with spectacular domes, manganese bearing mineralizations, emission centres, lava flow surface structures, convolute flow structures and spectacular cliffs with columnar fracturing.
Detailed field surveys and laboratory investigations conducted using aerial photographs, orthophotographs and satellite images allowed to examine and classify those landforms attributable to geomorphological processes associated with water, weathering, wind and coastal dynamics. The geomorphological study enabled to identify a variety of volcanic and coastal erosion landforms (cliffs, rias-like bays, and coastal caves) some of unique geomorphological, landscape and scenic interest.
The marine environment was geologically-geomorphologically interpreted chiefly by examining the Side Scan Sonar data, supplemented with direct observations during underwater surveys. For the pericoastal areas (0-15 m), photograms and recently acquired satellite imagery were analysed. Side scan sonograms together with direct underwater observations were used to determine lithology of submerged rock outcrops, to reconstruct boundaries between different rock types, to detect evidence of tectonic lines, to determine the evolution of coastal and underwater relief forms, to identify the main sedimentary facies and evidences of sea level stand (palaeo shore line).
An underwater geological-geomorphological survey was conducted to determine diaclases direction, extent and nature of rock outcrops, boundaries, distribution of biocenoses and dispersion of different mobile sediment facies, height and direction of erosion ridges, depth of erosion gulleys, direction of seafloor sedimentary structures (ripples, megaripples and hydraulic dunes).
Data from land and sea surveys were interpreted in CAD and GIS environments, while final rendering was obtained using vector graphics software. The thematic map compiled, which also indicates and classifies geosites and geomorphosites, is a document of significant interest for evaluating coastal tourism potential, for planning geotourism itineraries in the island's interior and along the coastal perimeter and submerged coastal zone for promoting tourist demand and also for environmental management and assessment of the coastal landscape and for the prevention of pollution and climate change related environmental hazards.
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