Moving geosites: how landslides can become focal points in Geoparks

DOMENICO CALCATERRA1*, DOMENICO GUIDA2 , PAOLO BUDETTA3, PANTALEONE DE VITA1, DIEGO DI MARTIRE1 AND ANIELLO ALOIA4

1. Department of Earth Sciences, Environment and Resources, Federico II Naples University, Italy

Corresponding author: domenico.calcaterra@unina.it 2. Department of Civil Engineering, Salerno University, Italy

3. Department of Civil, Arch. and Env. Engineering, Federico II Naples University , Italy 4. National Park of Cilento, Vallo Diano and Alburni - Geopark, Italy

Abstract: - Landslides are both landforms and geomorphic processes contributing to the long-term landscape evolution and one of the deadliest sources of natural hazard which endanger lives, property and activities. Many people in the world have experienced historical coexistence with landslides and related hazard, adapting settlement location and typology, land use and best practices. At large, local cultural identity is strongly influenced by this adaptation, while, in a few cases, landslides are expressions of both geodiversity and cultural identity. In these cases, it seems appropriate to refer to “moving geosites”, where academic researches supported by geoparks provide insights to educational system and dissemination to the public administrations, both as geodiversity functioning and effective approach to landslide risk reduction by raising public awareness. Key-Words: Landslide, Geosite, Moving Geosite, Geodiversity, European Geopark Network, Cilento-Vallo di Diano-Alburni Geopark

1 Introduction A recent study carried out by ISPRA, the Italian Agency for Environmental Protection and Research (IFFI Project - Italian Landslide Inventory; [1]) inventories more than 485.000 landslides in Italy, distributed over all the twenty Italian regions. Among them, Campania region occupies a quite high position in this unenviable ranking, as regards landslide density, with 171 events/100 km2. In Italy, landslide risk and its mitigation have been organically treated for the first time with the Law no. 183/1989. However, it was only after the huge tragedy occurred at Sarno and in other four Campanian towns (160 death due fast-moving landslides) on May 5, 1998 that the above Law was fully accomplished, especially as regards to the implementation of the River Basin Authorities (RBAs), public bodies responsible for the governance of the hydrographic basins. RBAs, among their duties, have to carry out the “Basin Plan”, a comprehensive programme of land management projects, which include the Hydro-geomorphological Setting Plan (HSP) aimed at identifying areas exposed to landslide and flood risk, and at mitigating it within levels consistent with the existing land use, so as to safeguard human lives and reduce as much as possible the damage to material properties.

The territory of Cilento and Vallo di Diano Geopark originally fell under the jurisdiction of two RBAs (RBA Interregionale del Fiume Sele and RBA Regionale “Sinistra Sele”), which in 2012 have been unified, along with a third RBA, under a new RBA named “Autorità di Bacino regionale Campania Sud ed Interregionale per il bacino idrografico del fiume Sele”. Both RBAs have recently updated their HSPs; integrating the respective landslide-inventory maps, Figure 1 has been created. Here, slightly less than 13.500 landslides are represented, many of which never inventoried beforehand [2]. The Geopark’s landslides pertain to all the possible types recognized by modern classification schemes. According to the Cruden & Varnes’ landslide classification [3], rotational and translational slides are the most common phenomena, followed by complex movements; the latter, in turn, represent the widest ones, in terms of areal extent. Landslides cover about 300 km2 of the Geopark territory and are present in 78 out of the 82 municipalities belonging to the Geopark community. Laurino, Centola and Celle di Bulgheria are the municipalities where landslides affect more than 10 km2 of territory. Most of the inventoried landslides show an average intensity, which can be expressed as a maximum expected velocity from slow to

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moderate (from 5 × 10-5 to 5 × 10-1 mm/s). Consequently, according to the existing Italian laws and regulations, the Geopark territory is prevailingly affected by average landslide risk. During the 12th EGN 2013 Conference, organized by the Cilento, Vallo Diano and Alburni Geopark (CVDA Geopark), the following topic was discussed: “Geoparks, as innovative approaches to raise public awareness in natural geo-hazards, climate change and sustainable use of the resources”. In this context, according to the mission on “raising public awareness” about landslide hazard and risk, the aim of the CVDA Geopark is to convert some representative landslide areas into publicly accessible geosites. This action was considered as an effective way to strengthen general awareness and knowledge of all the possible relevant geological assets, singular geomorphological evolution and historical cohabitation experience about landslides [4]. Previous studies have addressed many efforts to assess landslide risk affecting geosites for geotourism accessibility (e.g. [5]), while minor attention was given in the literature as to consider a landslide as a geosite in itself (e.g. [6]). This paper discusses on conceptual premises, scientific definitions and institutional formalization of a new concept in geodiversity management: “moving geosite”. As to make the concept more perceptible, a few cases of “moving geosites” are described.

2 From Landslide to Moving Geosite The concept of landslide was effectively stated by Varnes [7] as “a downward and outward movement of slope forming materials composed of natural rock, soils, artificial fills, or combinations of these materials”. The same author simplified its previous definition, by reducing it to “a downward and outward movement of slope forming materials under the influence of gravity”. Cruden [8] further simplified such definition, stating that a landslide denotes “the movement of a mass of rock, debris or earth down a slope” As it occurs whenever a complex issue must be simplified, to classify landslides has been one of the main interests for researchers and professionals. Due to their intrinsic complexity, landslides cannot be easily classified following a rigid taxonomic system, as in the case of plants or animals, due to several difficulties (e.g. events not perfectly repeatable; occurrence of different causes, movements and morphology; involvement of

different geo-materials). This is the main reason why, as regards landslides, typological classifications, which subdivide phenomena into repeating patterns (“types”) characterized by some descriptors, got success with time. According to [9], any landslide can be classified and described by two nouns: the first describes the material and the second describes the type of movement (e.g. rock fall, debris flow). Additional aspects of a landslide need to be defined, especially when its hazard is considered. It is therefore convenient to indicate for a given landslide its “magnitude” or “intensity”, as “a set of spatially distributed parameters describing the destructiveness of a landslide”[10]. Despite such a straightforward definition, a univocal quantitative definition of “landslide intensity” is not available at present, since it can be quantitatively assessed only using a variety of parameters, such as aspected or actual maximum velocity, total displacement, volume of the involved mass, depth of the moving mass, etc.. Some of the above parameters, however, represent key-factors in the landslide hazard evaluation. Among them, the movement velocity is unanimously considered as an element which can be easily linked to human response, since the destructive potential of a landslide depends on its velocity [9] and [10]. Landslides from extremely rapid to very rapid, exhibiting velocities of the order of 5 m/s, are relevant in terms of danger to human life because corresponds to the speed of a person running and could be called “catastrophic velocity”. Slower movements (slow, very slow, extremely slow) usually cause only material damage, being characterized by rate of movements lower than 5 × 10-3 mm/s. In these cases, living with landslides is possible, especially when the phenomena are under control, by means of monitoring instruments (e.g.: inclinometers, piezometers, GPS, remote sensing). Many landslides show an intermittent behaviour during their long-term evolution, following the first-time activation. Long periods of very slow bulk deformations are interrupted by relatively short term, fast, partial or global re-activations. Return times of these re-activations can be very variable, from decadal to centennial or even millennial. When reactivations span from decadal to centennial, historical memory promotes the human cohabitation and coexistence with landslides. On the contrary, in case of very long return times, people could not rely on experience and tend to forget the past dangerous phenomena and the previously affected areas. In this case, it may be appropriate to associate usual monitoring activities with communication and public awareness focused on the most representative

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examples of reactivable landslides. The latter is, in general, one of the missions of the European and Global Geopark Network and, in particular, one of the main goals of the CVDA Geopark, by using distinctive and representative landslides as “moving geosites”. According to the commonly accepted definition a geosite can be defined as “a site location area or territory in which it is possible to identify a geological or geomorphological interest for conservation” [11]. Reynard [12] added that an active geosite allows the visualization of geological and geomorphological processes in action, whereas passive geosites testify past processes. Here, we tentatively introduce the concept of “moving geosite”, as an active geosite which changes its morphology and spatial position due to representative geological constraints and singular, long-term, geomorphological, gravity-driven slope processes, today in action and/or clearly observable on the ground and/or as effect on man-made structures. These processes, however, are not such as to endanger human lives but can threaten human property, thus allowing a geosite to maintain all its intrinsic value and to be publicly accessible. Accordingly, natural geomorphological phenomena such as slow-moving, monitored or historically documented landslides or retreating coastal cliffs can be classified as a moving geosite. Following [13], if the value of a geosite may be assessed on the basis of four groups of criteria: scientific, cultural/historical, aesthetic and/or social/economic, the proposed “moving geosite” can be well accepted as a new concept in geodiversity .

3. Prototypal Moving Geosite In the following, relevant cases of “complementary and focal moving geosites” are presented, by using an adapted meaning of “complementary and focal geosites” proposed by the Candidature Dossier by the Cilento Geopark. A “complementary moving geosite” means a location where the international value in geo-heritage is strictly connected to archaeological vestiges, as examples of risk, resources and climate change conditioning in past human land occupation. A “focal moving geosite” means a location where, in addition to previous characters, forms of geosite fruition and management are already in use, also in risk mitigation and resource protection. Among others, the cases of Velia-Ascea, Petrosia-Roccagloriosa, Caporra-Caselle, Civitella-Moio are relevant examples of Italic, Greek and Roman settlements, conditioned by geological constraints.

Severino di Centola, S. Giovanni a Piro, Gorga-Stio and Pisciotta are only a few examples of Middle Age villages, historically conditioned by distinctive geological settings and landslide evolution. In the following, location, geological and geomorphological sketches are presented, along with main geodiversity features of a few of the above cited moving geosites (Fig.1).

Figure 1. Landslide and Moving Geosite map of the Geopark (mod. from [2]). Legend: 1) Rockfalls/topple; 2) Diffused shallow slow deformation; 3) Diffused complex landslides; 4) Slow earth flow; 5) Rapid debris flow; 6) Complex landslide; 7) Rockslide; 8) Deep-seated gravitational slope deformation; 9) Lateral spread; 10) Rotational/translational slide. 3.1 Caporra-Laurelli-Caselle in Pittari This proposed “moving geosite”, is located along the south-eastern mountain slope of Mt. Centaurino (Fig. 2) and is geologically connected to the Main Geosite n. 113 “Ophiolithic Olistolites of Centaurino” of the “List of the Geosites”, Appendix “A” in [14]. Along the mountain slope sandstone-conglomerate successions crop out, and they are laying in unconformity above the paleo-depositional units consisting in marly-clayey successions. The first are related to the Cilento Group (one of the most distinctive geological unit of the CVDA Geopark) and the lasts to the Ligurian Units both referred to Thethian domains, over-thrusted on the Bifurto-Piaggine formations, referred to the Alburni-Cervati-Pollino Unit [15]. The Caporra landslide develops along the contact between the above mentioned units, affecting both the arenaceous successions overlying the pelitic ones.

3.1

3.4

4

3.3

3.2

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Fig. 2 – The Caporra moving geosite, modified from South Campania RBA Inventory map. Legend: 1: Rockfall/Topple; 2: Roto-Traslation Slide; 3: Debris flow; 4: Rapid Earth flow; 5: Earth flow; 6: Slow flow; 7. Complex landslide; 8: Deep Seated Deformation; 9: Soil creep; 10: Areas affected by diffuse rockfall/topple; 11: Diffuse landslides; 12: Mass creep; 12: Ridge; Moving geosite boundary.

It can be classified as rotational multiple slides, with sliding planes located at a depth of more than 10 m, evolving downslope as slow earth- and rapid debris flow. The landslide can be considered as “moving geosite” due to its representativeness of an uniform long-term trend observed in the widespread landslide evolution involving: i) mid-slope rotational slide as original triggering mechanism in the erosional knickpoint; ii) retrogressive landsliding toward watershed; iii) progressive disarticulation and remoulding of landsliding materials until their flowing phase. In such a long-term evolution, the landslide system alternates slow movements and slight changes in morphology over a time scale of decades with short monthly acceleration of the displacements and strong topographic modifications, as surface expression toward flow-like event. A progressive shortening of the reactivation phases causes the collapse of the landslide system and the emptying of the landslide basin. One of this past collapsing event destroyed the Italic and Roman settlements of Laurelli, currently managed as local archaeological site. The moving geosite is suitable for scientific and educational field applications of geomorphological survey techniques, mid-term morpho-evolutive and short-term landslide activity mapping, dendro-chrological analysis, topographic surveys and advanced geotechnical controls. Finally, the site is

easily accessible via the public road Caporra from Caselle in Pittari village, famous in the Geopark for its eno-gastronomy, where you can taste local products and enjoy the picnic areas closed to low-mineralized spring waters. 3.2 Moio della Civitella Moio della Civitella can be considered as a “moving town”, due to a number of dormant/active landslides which affect large portions of the urban area. The origin of Moio dates back to VI÷IV century BC, and some archaeological on the hilltop named Civitella remains on testify to these ancient periods. Nowadays, it is a small town of some 1700 inhabitants and it is composed of two urban centres, Moio and Pellare. From a geological point of view, the prevailing outcropping complex is represented by the Crete Nere-Saraceno Frm’s. [15], mainly made up of argillites with intercalated carbonate and silicoclastic arenites, often weathered at the outcrop. A Quaternary cover given by heterogeneous debris in a silty-clayey matrix closes the succession. As a consequence, several tens of mass-movements have been inventoried over the territory of Moio della Civitella, where complex landslides and rotational slides evolving to translational slides are the prevailing types (Fig. 3).

Fig. 3 – The Moio della Civitella moving geosite, modified from South Campania RBA Inventory map. For legend, see Fig. 2. The role played by landslides in the morpho-evolution of the area is well demonstrated by the outcomes of the IFFI project and South Campania RBA [1]. Many of these landslides are dormant,

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while partial reactivations are common during the rainy seasons. At Moio della Civitella, a multidisciplinary study is ongoing [17], [18]), based upon the integration of remote sensing-based methodologies and conventional ground-based techniques. Inclinometer soundings and topographic network constituted by over 100 benchmarks are available, along with some piezometers, and the related data are being collected since 2007. Moreover, in the same years a GPS network was installed, whose functioning has been, however, temporarily discontinued due to technical and financial problems. The ground-based monitoring has been supplemented with data coming from remote sensing techniques, represented by the processing of SAR images in the time-span 1992-2010. These data have been further validated through a critical inter-comparison with two detailed field surveys, carried out in November 2007 and December 2013 respectively. aimed at evaluating distribution and degree of the landslide damage to buildings according to the a classification already applied to several unstable towns in southern Italy ([19], [20], [21]. Thanks to the PS-technique, 345 permanent scatterers were identified [20], which allowed to detect average values of velocity up to 16.2 mm/year in the time span 1992÷2001, to be related to intermittently moving landslides affect various sectors of the urban settlements of Moio and Pellare. Di Martire et al. [22], adopting the Coherent Pixels Technique [23] recognized average displacement rates in the order of 5-10 mm/year, along a E-W direction, coherent with the ground data. Evidence of almost continuous surface displacements in the urban area were confirmed by both the monitoring network and the landslide damage survey. As for the latter, the damage pattern already observed in 2007 revealed a substantial worsening in 2013, especially in the southern and eastern part of Pellare. Moving from this previous knowledge, Moio dela Civitella can be considered as a place of absolute interest as to demonstrate the possibility to coexist with active geological phenomena.

3.3 S. Severino di Centola

Due to several rockslides and falls affecting cliffs overhanging the Medieval hamlet and the State Road “Mingardina”, the San Severino di Centola site can be considered an interesting example of Geosites exposed at high landslide risk. This fortified hamlet had been built in that position as to control the underlying valley of the Mingardo River,

where the main roads to the Policastro Gulf and Palinuro coast are located. The Medieval hamlet has been abandoned since the end of 19th century. The historical nucleus of San Severino and its most recent part, built downvalley, are both located on the northern slope of Mt. Bulgheria, made up of carbonate rocks belonging to the Campanian-Lucanian-Calabrian Platform, whose age range from Upper Triassic to Eocene [26]. In the area occupied by the Medieval hamlet thinly bedded, NNW dipping calcilutites and marly limestones crop out, along with fine-grained marly (“scaglia rossa”-like) intercalations (Fig. 4).

Fig. 4: Map of the S. Severino di Centola moving geosite. Legend: 1 Recent sandy–clayey deposits, 2 Bifurto formation, 3 calcilutites and marly limestones, 4 rockfall detachment line, 5 rock slide, 6 detected boulders, 7 path segments with bouncing

motion mode, 8 path segments with rolling motion mode.

In this area, the sub-vertical slope (about 85°) is crossed by several NW-SE and NE-SW oriented faults, many of which showing low angles; the whole carbonate rock mass is severely jointed, as a consequence of its involvement in the last tectonic stages, dated back to Upper Pliocene [24]. The medium-lower part of the slope, showing an elevation between 150 and 100 m a.s.l., is made up of thin beds of sandstones, intercalated with clayey marls. These lithotypes, showing a chaotic setting, are mantled by a weathered sandy-silty cover, a few metres thick. A normal fault, E-W oriented, is juxtaposed between the stratified calcilutites and the underlying flysch deposits. Downslope, where the new town of San Severino is located, slope angles become lower: here, debris and alluvial deposits crop out, along with made-ground

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deposits. Along the slope sector where the flysch deposits crop out, the former State Road no. 562 “Mingardina” runs with a very tortuous path, characterized by quite high longitudinal gradients. The road is characterized by the following: (1) only one single lane going in each direction without an adequate hard shoulder; (2) no ditches to retain any fallen rocks, allowing the material to spill out onto the road; and (3) a high degree of road curvature resulting in a small percentage of the decision sight distance. The road is not wide enough in most places to allow vehicles to overtake one another (especially buses and trucks) or vehicles travelling in opposite directions meeting up. The study area is affected by falls and planar slides, which involve the well stratified calcilutites. In the upper part of the slope, the discontinuities’ attitude and the rock mass intense jointing favour the detachment of rock volumes of variable size, which reach the road and the underlying urban area. Events of such kind occurred in 1980, 1992 and 2008, causing victims (1 in 1980), injured (in 2008) and road closures for several months. The triggering factor of the December 15, 2008 landslide was represented by the intense antecedent rainfall and the event can be classified as a planar failure occurred along the calcilutites’ bedding planes; the latter were crossed, laterally and upslope, by high-angle, high-persistence joints and by sub-vertical joints, showing a direction parallel to the slope face. The occurrence of two important joints, NW-SE oriented, contributed to subdivide the unstable mass in three parts, characterized by almost parallel sliding directions. The detached volume has been evaluated as large as about 4.000 m3; the landslide accumulation, made up of blocks up to 7 m3 and more, prevailingly stopped at the foot of the rock cliff. However, some blocks, bouncing and rolling along the medium-lower part of the slope, invaded the road, in some cases with a further downslope movement, which, in turn, allowed the unstable mass to reach the slope base. For the studied slope according to rockfall trajectories drawn by means of impact marks and boulder stopping points, two hazard scenarios have been proposed [25]. A first scenario was drawn on the basis of the trend of iso-kinetic curves. This trend was established interpolating energy values measured along several topographical sections. Furthermore, areas exposed to 30% and 70% frequency of block transits and endpoints were bounded. With reference to the Swiss Federal Guidelines [26], another scenario was prepared on the basis of possible kinetic energies due to rock falls with 100-year return periods. According to these approaches it is

possible to map-delineate zones of high, medium and low rock fall hazard. In the high and medium hazard zones, people are at risk of injury both inside and outside buildings. Damage to buildings should be expected, but not a rapid destruction as long as the construction type has been adapted to the present conditions. In the low hazard zone, people are at slight risk of injury. This zone is mainly an alerting domain. In Switzerland, these maps are basic documents for elaboration and improvement of Regional and Communal Master Plans for land use; planning, construction and transformation of buildings and infrastructures; granting of subsidies for building and development, as well as for slope stabilization and protection measures. In conclusion, this case-study allowed to verify results furnished by new rockfall hazard and risk methods, in order to map-delineate areas affected by rockfall trajectories and to design rockfall protection systems. As the increasing tourist number makes worse involuntary risk conditions of appealing but arduous resorts affected by active landslides, the San Severino geosite can be considered as an interesting case-history in order to demonstrate that the fruition cannot leave out of consideration the landslide hazard zoning and mitigation of risk conditions.

3.4 Gorga-Stio Along the western slopes of the Mount Tempa Casalicchio (818 m a.s.l.), located at the upper northeastern limit of the Alento River basin watershed (Cilento and Vallo di Diano Geopark, Campania region, southern Italy), clear geomorphological evidences lead to recognize the existence of a large landslide which involves completely the Gorga settlement (about 1000 inhabitants), belonging to the Stio Municipality. The morphological setting of the area as well as damages suffered by buildings, especially during a partial reactivation occurred during the ‘50s of the last century, indicate that the activity of the slope gravitational phenomenon can be guessed as comprised between the relict stage, at the scale of the whole slope, and the long-period dormant state, if considering the most mobile parts of the landslide body. This phenomenon was firstly studied in a preceding geological and engineering geomorphological analysis of the upper Alento River, which depicted a preliminary geological model and fundamental geomorphological features of the landslide. More recently, the updating of the geological knowledge [27], has given further details and characterizations of geological units

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constituting the Gorga and Stio surroundings. According to these results, the western slope of the Mount Tempa Casalicchio, from the top (818 m a.s.l.) down to the main valley of the Alento River (430 m a.s.l.), is characterized by basinal and turbidite series with a composite stratigraphic and structural setting, which can be simplified by the identification of principal engineering geological units, namely lithological complexes. The upper part of the Mount Tempa Casalicchio is constituted of a marly and calcareous lithological complex, belonging to the Torrente Trenico unit (Upper Eocene-Lower Miocene), which is superposed over an argillaceous and calcarenitic lithological complex, including the Genesio unit (Eocene). While the first is characterized by an almost regular downslope-dipping bedding, the second lithological complex shows stronger tectonic deformations due to polyphasic folding and shearing. Such lithological and structural features make the rock-mass of the latter lithological complex with a lower shear strength. The abovementioned units are overlaid by a regularly bedded turbidite arenaceous-pelitic complex, belonging to the Pollica Formation of the Cilento Group [15], which is supposed to be in lateral contact by a normal fault (Fig. 5).

Fig. 5: Engineering geological map of the Gorga moving geosite. Legend: 1) Current alluvial deposits; 2) Landslide deposits; 3) Arenaceous-pelitic lithological complex (Pollica Formation); 4) Marly and calcareous lithological complex (Torrente Trenico unit); 5) Argillaceous and calcarenitic lithological complex (Genesio member); 6) Fault; 7) Bedding attitude; 8) Complexly folded and shearing deformation of bedding; 9) Landslide main and secondary scarps; 10) Counterslope; 11) Depressed areas; 12) Roads; 13) Buildings. The morphological analysis of the unstable slope, carried out at 1:5,000 a scale, allowed to identify a number of principal and minor landslide structures and to formulate hypotheses about the evolution of the phenomenon and its kinematics. The landslide has an overall length measured along its median axis of about 1500 m and a height of 280 m (average slope angle of 11°). The remnants of the

main scarp are clearly distinguishable along the slope, between 710 and 720 m a.s.l., by the analyses of aerial photos and topographic anomalies, although their morphological appearance indicates clearly a relict state of activity. This is also confirmed by the advanced weathering of bedrock outcrops along the main scarp. Within the main body, a series of minor forms, such as depressions and counterslopes testify a composite spatial and temporal kinematic evolution of the landslide due to differential minor reactivations which involved lateral and frontal zones of the main landslide body. In particular, one of these morphological signs is extended across the Gorga settlement being presumably related to the recent reactivation occurred in the ‘50s of the last century, which caused severe damages to building in the town. In general, the relevant degree of dissection of the landslide accumulation zone in its terminal part as well as the negligible deviation of the Alento River path indicate a prolonged period of inactivity of this mass movement. On the basis of the preliminary geological model of the landslide, which is reconstructed by results of geological survey only (Fig. 5), the geological and structural predisposition to landslide occurrence can be recognized in the superposition of the marly and calcareous lithological complex over the argillaceous and calcarenitic one. This geometric and geo-mechanical conditions, along with the downslope dipping of bedding of the first member, led the triggering of the landslide with a complex style [37]. According to this evolutionary scenario, the landslide started as a rock slide and evolved in a rock-earth flow [3]. Further studies should be carried out to define in greater detail the geological model of the landslide, based also on borehole and geophysical data, in order to clarify the underground geometries and the possible involvement in the slope mass movement of a chaotic interval, which is often found at the base of the Cilento Group, as in the Caporra area (see par. 3.1. The Gorga landslide is of particular relevance in the Geopark because it represents a special case of geohazard related to a long-term dormant landslide, which is challenging to be assessed due to the difficult determinable recurrence of reactivation and complex kinematic modelling. For such scientific reasons as well as for historical value of the Gorga settlement, this area constitutes an emblematic example of “moving” geosite to be included among geosites of the Cilento Geopark, with the scope to increase awareness about geological risks and their management.

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3.5 Pisciotta-Rizzico In the Rizzico locality, Pisciotta Municipality (Cilento, Vallo di Diano and Alburni Geopark, Campania region, southern Italy), a slow-moving slope mass movement is known since several decades ago to have repeatedly damaged the provincial road SS 447 along a stretch with a length of about 600 m (Fig. 6).

Fig. 6 Aerial view of the Pisciotta Moving Geosite (modified from Google Earth, 2004). Damages consisted in slow vertical and horizontal deformations of the roadway and of the retaining walls as well as in slow opening of cracks in the road surface. Low velocities of displacement have allowed the continuous repairing of the road to maintain the vehicular traffic in a fairly safe condition. Since October 2013 the road SS 447 was definitively closed due to the excessive deterioration of road conditions which has prevented a safe vehicular traffic. Only in recent years the worsening of the morphological impact on the slope as well as the increase of road deformations led to recognize clearly the existence of a deep-seated landslide involving the whole slope of a secondary hill (237 m a.s.l.), facing westward, down to the Fiumicello Torrent valley (15-25 m a.s.l.). Moreover, a greater attention has been paid to this landslide after the recognition that a tunnel of a national railway is exposed to risk because crossing its foot. The landslide involves a turbidite series belonging to the Saraceno Formation (North-Calabrian tectonic unit), which is comprised of intercalated calcarenites, marls and argillaceous rocks, with a complexly folded structure. A recent study [28] reconstructed the kinematic evolution of the Pisciotta landslide by the examination of all available aerial photos, from 1943 to 2006. Moreover, quantitative analyses of ground deformations were executed both considering the progressive displacements of the road, by comparing available contour maps and

ortophotos in the period 1955-2006, and through a specific topographic monitoring carried out between September 2006 to March 2009 in the upper sector of the landslide. An engineering-geological model of the landslide was reconstructed by means of stratigraphic data derived by a campaign consisted of boreholes, inclinometer monitoring as well as geological and geophysical surveys (Fig. 6). The analysis of aerial photographs demonstrated the existence of an early stage of deformation since 1943 that has expanded progressively in the following years. Besides of the main scarp and the landslide flanks, other significant longitudinal and transversal cracks as well as positive or negative morphologies were clearly observed and mapped during the following years. A progressive depletion of the upper part of the slope, a bulging of the landslide foot and a progressive enhancement of the morphological impact of the principal landslide structures were reconstructed. The quantitative kinematic analysis based on the estimation of progressive displacements of the road (1955-2006) and on the topographic monitoring of optical targets allowed the assessment of ground deformations for about 53 years (1955-2009), with a total maximum displacement of the road of about 55 m and an average velocity of about 1 m year-1. The kinematic analysis showed a progressive and constant deformation, with a little increase of velocity after 1994. Average velocity of about 0.4 cm day-1, maximum values up to 1.3 cm day-1, after prolonged rainfalls, and minimum velocity of about 0.1 cm day-1, at the end of the dry season, were measured. These data allowed to classify the landslide across the very slow and slow velocity classes [3]. The monitoring of ground deformations also permitted to assess a composite kinematics of the landslide body that resulted with differential displacements, velocities and accelerations. The geological model of the landslide was found to be conditioned by specific stratigraphic and geo-structural constraints. The landslide involves an upper stratigraphic interval of the Saraceno Formation, with a dominant marly-argillaceous composition. The geostructural setting of the Formation is intensely folded and faulted but with a globally monocline attitude downstream dipping. The left flank of the landslide is set on a normal fault. Based on the reconstructed model and considering the variability of the depth of the rupture surfaces, assessed from 30 to 50 m, the depleted mass and the accumulation volume were estimated in the range 4 ÷ 6 × 106 m3. The almost uninterrupted state of activity, existing in the last seventy years at least, the slow kinematics, not yet

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evolved in a paroxysmal global failure stage, and the exposition to risk of a railway tunnel make this landslide a special case of geo-hazard to be analyzed further and to be taught in order to increase education and awareness about landslides and natural risks. For these reasons the Pisciotta landslide can be considered a scientific, didactic and educational “open laboratory” to be included among “moving geosites” of the Cilento, Vallo di Diano and Alburni Geopark.

4 Roscigno Moving Geosite Project The most representative “moving geosite” in the CVDA Geopark is Roscigno Old Village, also known as “the walking village” (Fig. 13). The old village, recognized as UNESCO Heritage, was completely abandoned since the early 20th century, due to a reactivation of a huge and complex slide-earth flow landslide, dormant since 4th century BC, when a previous reactivation affected the ancient, italic settlement (Fig. 7), located on Mt. Pruno hilltop.

Fig. 7 The Old Roscigno village moving geosite, modified from South Campania RBA Inventory map. For legend, see Fig. 2. Following the 2010 surrounding reactivations, an experimental, interdisciplinary, integrated and inter-institutional project, named “Roscigno Project”, is going to start, involving, among other institutions, the CVDA Geopark, as focal institutional support to the project [29]. The latter represents the first implementation of the Geopark Action Plan in providing a different perception of what usually is felt as hazardous, by using geodiversity as knowledge tool in public awareness raising.

5 Conclusions One of institutional mission of the territory recognized as Geopark by European and Global Geopark Network is the integration of the geoheritage with natural resources, hazard assessment and risk management. Since its institution and constitution time (1995-1998), the National Park of Cilento Vallo Diano and Alburni has dedicated great efforts in the bring together biodiversity conservation and geodiversity preservation. Starting from these activities, since CVDA Geopark assumed as “grand strategy” the integration between geosite recognition, fruition and functionality and geological hazard mitigation actions and natural resources conservation practice. According to the conclusions of the 12th EGN Conference, incoming results about the proposed concept “moving geosite”, could be shared with other landslide-prone geoparks around the world [29], where similar projects could be an additional issue of their core mission within research, education, dissemination and fruition actions addressed to awareness in risk management. References [1] ISPRA, Landslides in Italy, Special report

2008. Report n. 83, 2008, 32 pp.. [2] Calcaterra D., Di Martire D., Guida D.,

Landslides in the territory of Geopark. Geopark’s book n. 2, 11-21, National Park of Cilento, Vallo di Diano e Alburni, 2013, ISBN 978-88-907281-0-5.

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[7] Varnes, D.J., 1958, Landslide types and processes in Eckel E.B., ed., Landslides and Engineering Practice, Highway Research Board Special Report 29, NAS‐NRC Publication 544, Washington, D.C., 20-47.

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