GNGTS 2013 - Atti del 32° Convegno Nazionale

The eastern Ischia island: from Casamicciola to Punta della Signora. The eastern Is- chia coastal sector between the Casamicciola harbour (northern Ischia) to Punta della Signora (south-western Ischia) is mostly constituted by rocky outcrops, mainly nearshore, having a lavic and/or pyroclastic composition (Ispra, 2010). These outcrops are formed mainly of blocks having also great dimensions (more than 1 m 3 ), or by the seaward prosecution of lava flows or pyroclastic deposits. The remaining portions of sea bottom are formed by a wide cover of middle to fine-grained sandy sediments grading into gravels having a varying nature (lavic, pyroclastic and sometimes anthropic; Ispra, 2010). The sea bottoms from the east of Casamic- ciola to the Spiaggia degli Inglesi, to the west of Ischia harbour are characterized by artificial blocks having a varying nature and, in correspondence to the beach of Spiaggia degli Inglesi, by gravels grading into sands and gravels. At 2.5 m of water depth it occurs a volcanic dyke, N-S trending. The sea bottoms from the Ischia harbour to Ischia Ponte are characterized by artificial blocks in correspondence to the harbour and by wide outcrops of sands, often colonized by Posidonia oceanica (Gambi and Buia, 2003; Gambi et al. , 2003). From Ischia Ponte to the lavic coastal cliff of the Ischia Castle the sea bottom is formed of pelitic sands up to – 4 m, followed by sands colonized by mattes of Posidonia oceanica . From the Ischia Castle to Punta della Pisciazza, mainly sands occur at the sea bottom, at water depths among – 2 m and – 25 m, often colonized by mattes of Posidonia oceanica . In the coastal area surrounding Punta della Pisciazza lava blocks occur up to – 6 m of water depth, grading seawards into sands with mattes of Posidonia oceanica . The western Ischia island: from Lacco Ameno to the Maronti littoral. The western coastal sector of the Ischia island, from Lacco Ameno to the Maronti beach is characterized by two main morphologic types: high relief coasts, conditioned by the occurrence of rocky formations, directly adjoining the sea or separated by narrow beaches of gravels and pebbles; low relief coasts, in correspondence to reliefs retreated with respect to the present-day shoreline, allowing for the formation of coastal cliffs with sandy littorals, sites of an intense touristic activity. From the Lacco Ameno harbour to the Casamicciola harbour the sea bottom is characterized by a lowered area, developed up to 30 m of water depth, where an abrupt slope occurs. The sea bottom shows the occurrence of coarse-grained heterometric deposits, composed of blocks pertaining to the Epomeo Green Tuffs (Gillot et al. , 1982; Vezzoli, 1988; Ispra, 2010), often organized as sedimentary wedges having a variable extension. The M.te Vico and Zaro promontories face directly the sea with active rocky coastal cliffs. The submerged cliff represents the physical continuity of the Zaro lava flow along all the coastal belt, covered by detritic deposits at the toe of slope. The sea bottoms are characterized by large detritic accumulations composed of heterometric blocks and representing landslide deposits. From Punta Imperatore to Punta del Chiarito high relief coasts occur due to the outcrop of coherent lavic and pyroclastic successions. The sea bottom follows the articulated physiography of the emerged sector, characterized by rocky promontories. The base of the submerged slope is aligned with the structure of the continental slope and results close to some canyons’ heads, draining the coastal sediment supply. The Maronti littoral is characterized by a narrow beach of sands and gravels located at the foot of a partly inactive coastal cliff, whose elevated portion shows the outcropping of the Epomeo Green Tuffs. Physiographic and morphologic settings of the Ischia island. The study area includes several morphological ranges, each one characterized by a well defined elevation interval versus average slope (Fig. 1). The domain A1 includes the Ischia outcropping volcanic edifice at depth more than 0, characterized by an average slope range of about 20°-40°. The domain A2 represents an intermediate stage, acting as an according layer towards the continental shelf. The domain B is 228 GNGTS 2013 S essione 1.3