Coastal vs volcanic processes: Procida Island as a case of complex morpho-evolutive response

Abstract

The island of Procida (Gulf of Naples, Italy) is a site of considerable importance from a historical, cultural, and landscape point of view. The island is located along a volcanic active area in the mid-Tyrrhenian and owes its formation to several explosive eruptions started more than 70 ka BP. Presently, the entire perimeter of the island is bordered by cliffs, often articulated in an alternation of headlands and coves, sometimes with shallow sandy beaches at the base (pocket beaches). However, the presence of different orders of submarine terraced surfaces represents a significant clue to coastal response to former sea-level stands.This paper aims at reconstructing the main coastal changes that occurred in the area during the Holocene mainly driven by the interaction between the post-glacial sea-level rise, vertical ground movements (VGMs) of volcano-tectonic origin, and wave action. The coastal sector was investigated using a multi-techniques approach including direct and indirect methods, in order to obtain a detailed geomorphological characterization of the whole study area. In particular, data from direct coastal surveys were integrated with photo-interpretation of areal and satellite photos, morphometric analysis of high-resolution DTMs from Lidar and bathymetric data, interpretation of morpho-acoustic data, archaeological, geomorphological and geological sea-level markers. The geomorphological analysis of this multidisciplinary dataset resulted in the detection of the main morphological elements interpreted as evidence of ancient seascapes. In particular, three orders of paleo-shore platforms were mapped in the underwater sector, allowing the evaluation of as many phases of relative sea-level stand, at −23.2 m, −11.2 m, and − 4.2 m MSL dated at approximately 4.0, 2.0, and 1.0 ka BP. These coastal landforms were interpreted as the main consequence of a seacliff retreat, exacerbated by volcano-tectonic intermittent subsidence that favoured their poly-cyclic formation. However, the integration between the geomorphological and meteo-marine analysis allowed discriminating differentiated cliff backwearing responses between the western and eastern coastal sectors of the island, due to a prevailing occurrence of storms from the south-western sector. The proposed methodological approach focused on a multi-temporal geomorphological analysis applied to a multi-modal dataset, aims to comprehensive reconstruct the coastal response of a volcanic high rocky coast to the complex interaction between endogenous and exogenous forcing factors during the Holocene.