## 1 Introduction  
Landslides of different typologies and size can occur along active retreating coastal cliffs, where the gravity-induced processes often superimpose, in space and time, to marine processes in shaping the coastal slopes. Rocky coasts represent about 80% of coasts worldwide [1], and they represent a great part of coasts around the Mediterranean basin [2]. Rocky coasts have been broadly studied so far, representing zones with high economic, social, cultural, and touristic values. In particular, many studies focused on the factors controlling erosional processes along both hard and soft rock coasts [3], whereas other studies focused on the present morphodynamics, with a particular emphasis on the role of active landslides on the present evolution of the coastline and the associated hazards [4; 5]. Nonetheless, the understanding of the role of the slope shape and tectonic structures on the long-term morphoevolution of coastal slopes is crucial to enhance the awareness of slope instability on rocky coasts. Complex morphodynamics, implicating multiscale morphoevolutionary scenarios, often characterize rock slopes affected by extensive landslide processes. Mass Rock Creep (MRC) _sensu_[6], has been demonstrated to represent a critical process for the long-term morphoevolution of rock slopes in different geological contexts [7; 8; 9]. Large disruptive landslides may represent the ultimate stage of the MRC process that can culminate in paroxysmal events (like rock avalanches); nevertheless, these ultimate events are anticipated by gravity-driven deformations which represent the strain effect of the rock mass viscous rheology. When these deformations develop into abrupt and generalized slope failures, it is caused by an increasing strain rate over time [10]. In particular, threshold conditions can be reached when the stationary creep stage evolves into an accelerating creep stage [11; 12]. Generalized slope failures are typically associated to mass strength reduction due to rock mass damage, the latter occurring over time as an effect of viscous deformation [13; 14]. Catastrophic failures that occur in the accelerating stage of MRC process can progress rapidly into rock avalanches and slides that are generally due to the fragmentation of the involved rock masses throughout their propagation and emplacement [15]. Coastal slope processes can be prone to evolve in paroxysmal events [16; 17; 18] or can display a continuous slow activity associated with MRC process [19; 20; 21; 22]. Along rocky coasts, proneness to landslides needs to consider the relations between the cliff rheology and lithostructural setting, as well as external stresses [23; 24], such as rainfall, earthquakes, or storm sea waves. Furthermore, considering the coastal slope instability at a longer time scale, changes in sea level, occurring over a wide range of space-time scales [25], should be taken into account. The investigation of rocky coasts often represents a research challenge due to the accessibility of rock cliffs in all their portions. Remote sensing techniques from satellite imagery and aerial photos can be sometimes unhelpful due to cliff attitude and/or in the case of high-angle sloping coasts, as for example plunging cliffs. [26] proposes a methodological approach for the continuous acquisition of geological, geomorphological, hydrogeological, and biological datasets along rocky coasts based on a snorkeling approach. The latter is helpful for a detailed mapping of landforms and processes at the foot of the coastal slopes. [27] proposed a combined approach based on snorkeling-based and traditional fieldwork in the inland for a detailed mapping of the rocky coasts affected by gravity-induced slope processes. The rocky coast at the Conero promontory (Central Adriatic Sea, Italy) presents several features that account for the predisposing role of morphostructural setting on coastal landslide processes involving extensive rock slopes [28; 29].