Rend. Online Soc. Geol. It., Vol. XX (2015), pp. 53-56, 3 figs. (doi: 10.3301/ROL.2015.13) © Società Geologica Italiana, Roma 2015 ABSTRACT The present work shows the preliminary data on the erosion rate estimation and weathering forms on the outcrop of the Neapolitan Yellow Tuff along the “Rupe di Coroglio” (Naples, southern Italy). This pyroclastic complex shows abundant alveolar and tafoni forms mostly related to salty seawater and salt spray processes that affect the western portion of the Posillipo hill. In this coastal environment, weathering forms such as alveolar, honeycombs or tafoni are very common producing from small to large deep cavities, development of which produces landslide phenomena. This area has been protected by consolidation interventions such as barrings, retaining walls and anchored structures. After 30 years from first interventions of consolidation, has been observed that some cables of the anchored structures protrude from rock escarpment with values between 5 and 12 cm. Based on these values an average erosion rate of 1.6÷4 mm/year was estimated. KEY WORDS: honeycomb, erosion rate, volcaniclastic tuffs, weathering. INTRODUCTION Mineralogical and petrographical transformations in the rocks are generally produced by weathering processes that further cause a considerable decay of the physical-mechanical properties of the original rock, predisposing the slope instability processes (e.g., Calcaterra et al., 2004; Ietto et al., 2012, 2013; Perri et al., 2011; Borrelli et al., 2014). Due to the combination of several predisposing morphological, lithological, tectonic and climatic factors, intense weathering and related slope instability and landslide events is very common. Furthermore, in coastal environment, weathering forms such as alveolar, honeycombs or tafoni are very common alteration phenomena, producing small deep cavities mainly in granitoid and pyroclastic rocks than in other rocks. Alveolar and tafoni weathering develops as a result of a number of different weathering processes involving soluble salts in most cases. The role of salty seawater and salt spray seems to be the most important factors for these weathering forms ( i.e., Doehne, 2002 and references therein). This paper shows the preliminary data on the weathering forms and erosion rates related to the weathering processes which affect the volcaniclastic tuff rocks forming the western edge of Posillipo hill (Naples, southern Italy), better known as “Rupe di Coroglio”. The southern portion of “Rupe di Coroglio” is 140 m high and jutting vertically to the sea; while in the northern portion the presence of a road along the hillside interrupts the vertical slope profile. Both hillsides are characterized by widespread weathering forms such as honeycombs and tafoni, due to weathering processes in coastal environment, and by frequent landslide phenomena ascribed to rock fall, rock topple and sliding processes, enhancing escarpment retreat. The geomorphological condition and the urban context of the “Rupe di Coroglio”, especially on its northern edge, indicate that stabilization and consolidation interventions were necessary along the landslide area. GEOLOGICAL FRAMEWORK The studied area is situated along the eastern edge of the Campi Flegrei caldera (fig. 1) and consists in thick pyroclastic deposits ascribed at the Neapolitan Yellow Tuff (Orsi et al., 1996). Weathering processes in volcanic tuff rocks of the “Rupe di Coroglio” (Naples, southern Italy): erosion-rate estimation and weathering forms Fabio Ietto (*), Francesco Perri (*) & Luciana Filomena (*) _____________________________________________________________________________________________________________________________________________________ (*) Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della Calabria, 87036 Arcavacata di Rende, CS; E-mail: lucianafilomena@hotmail.com Document type: Short note. Manuscript history: received 1 August 2014; accepted 1 September 2014; editorial responsibility and handling by Donatella De Rita, Rocco Dominici, Federico Famiani. _____________________________________________________________________________________________________________________________________________________ Fig. 1 – Topographic map of the Campi Flegrei caldera (Orsi et al., 1996 modified) with the Neapolitan Yellow Tuff outcrop and the studied area indicated in red (Coroglio headland is the “Rupe di Coroglio”). 33