*4.2. Geomorphological Setting of the Coroglio-Trentaremi Sea Cliff*

Geomorphological analysis has been addressed to the recognition of the predisposing factors that may cause landslides and cliff retreat, and the results are reported in the geomorphological map of Figure 6. The study area is characterized by high sea cliffs that are prone to retreat because of both their stratigraphical setting (alternation of poorly cemented pyroclastics and tuffs) and the occurrence of a dense net of sub-vertical fractures in the tuffaceous deposits.

**Figure 6.** Geomorphological map of the Coroglio-Trentaremi area.

The geomorphological map of Figure 6 highlights the diffuse presence of landslides, which have also been reported on Google Earth 3D view (Figure 7), where they have been classified according to the type of movement and the type of material involved. Moreover, flow-like landslides (yellow dots in Figure 7) affect the sectors of the Coroglio-Trentaremi sea cliff where post-NYT pyroclastics outcrop and with slope angle between 45◦ and 70◦, whereas rock-falls (red dots in Figure 7) occur in the NYT with slope angle between 70◦ and 90◦. We also mapped in Figure 7 the caves at the base of the sea cliff, which are mainly due to anthropic activities for the NYT extraction. The collected data clearly suggest

that the main factors influencing the types of landslide are lithology and slope degree (Figure 8). Flow-like landslides remain confined to the upper part of the cliff, where soft unconsolidated deposits rest on top of the NYT formation. The presence of hard/soft rock-types contacts along the sea cliff may also increase the possibility of detachment of rock falls because of selective erosion. Also, the presence of caves (both natural and artificial) plays a crucial role in the evolution of the sea cliff by identifying sectors more prone to instability because of the presence of vacuums that may enhance sea erosion at the base of the cliffs.

**Figure 7.** (**A**) Google Earth 3D views of the Coroglio-Trentaremi coastal sector. (**B**) Detail of the Coroglio sea cliff. (**C**) Detail of the Trentaremi sea cliff.

**Figure 8.** Main predisposing factors controlling cliff stability along the Posillipo promontory. Geological cross-sections are modified from Figure 5. Vertical lines in the NYT indicate sub-vertical fractures affecting this unit.

In Figure 9 we show some photos of the sea cliff that allow us to appreciate the size of the landslide bodies, which are up to some hundreds of cubic meters. Landslide bodies of different ages may also be appreciated because of the lack of vegetation, which testify for the high frequency of rock falls along this sea cliff. The tuffaceous deposits of the NYT are also locally affected by a very dense fractures network that shapes the sea cliff profile. Fractures are in many cases open, thus suggesting the possible occurrence of a landslide event in the near future (Figure 10).
