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A model of caldera resurgence was applied to the Island of Ischia to explain uplift, volcanic activity and tectonics on Mount Epomeo, as well as historical seismicity and slow ground movements recorded for the past 2000 years. A two-dimensional mechanical model was utilized for the crust, which was considered to be an elastic plate overlying a laccolith. Geometric dimensions and mechanical parameters were constrained using geological, geophysical and geochemical data. We propose that a laccolith, with a diameter L of c. 10 km, and a depth of up to 1 km in the centre of the island, triggered the caldera resurgence after the Mount Epomeo Green Tuff eruption forming the caldera (55 000 a BP). A bending phase and a punched laccolith phase are thought to have caused the observed deformations in the caldera. These processes control the tectonics at the boundary of the Mount Epomeo resurgent structure, volcanic activity and dynamics of the island. process starting between 33 000 and 28 000 years ago, forming the Mount Epomeo block. Total uplift, deduced from the present height of marine deposits and eustatic variations, is 710 m on the southern flank and 920–970 m on the northern flank, with an average uplift rate of 2.3 and 3 cm a−1 respectively (Barra et al. 1992; Tibaldi & Vezzoli 2004). This resurgence of the central part of the island is thought to be associated with the input of new magma at shallow depths, which from 28 000 to 18 000 a BP produced volcanic deposits of significantly different composition from those of previous eruptions (Civetta et al. 1991; Petrini et al. 2001). The resurgent block of Mount Epomeo, dominating the central sector of the island, is roughly square, with sides about 4 km long. The edges of the block are marked by a system of faults with NW–SE, NE–SW and N–S strikes (Fig. 2). The faults on the northern side of Mount Epomeo have been active over the last 800 years as seismogenetic sources, as testified by historical data. Furthermore, the horseshoeshaped structure of Mount Epomeo, open towards the southeast, and the large hummocky deposits off the south coast of Ischia, recently recognized by marine surveys, are consistent with an avalanche involving the summit of the Mount Epomeo resurgent block and the southern onshore caldera flank (Luongo et al. 1995; Cubellis & Luongo 1998; Marsella et al. 2001; The island of Ischia is a 46 km2 volcanic field emerging at the western edge of the Bay of Naples (Fig. 1). This field represents the emergent part of a more extensive volcanic area developed mainly to the west of the island (Vezzoli 1988; Bruno et al. 2002). It consists of volcanic rocks deriving from a number of eruptive centres which have been largely destroyed or covered by subsequent activity and can now be identified only in part. The oldest outcrops date back to about 150 000 a BP, while the most recent eruption occurred in 1301–1302 AD in the eastern sector of the island (Vezzoli 1988; Civetta et al. 1991). During this period, five phases of activity have been distinguished and grouped in an older cycle and a younger cycle, whose transition is defined by the great alkali-trachytic ignimbrite eruption of the Mount Epomeo Green Tuff (MEGT) (55 000 a BP) which was accompanied by a caldera collapse (Table 1). Although the boundaries of the caldera are ill-defined, it has an approximately elliptical shape 10x7 km2 (Fig. 2), with the longer axis trending east–west (Tibaldi & Vezzoli 1998). The caldera depression was filled – at first in sub-aerial and subsequently in submarine conditions – by the MEGT, the tuffs of the Citara Formation (CF) (about 44 000–33 000 a BP) and subaqueous epiclastic and pyroclastic deposits, Colle Jetto Formation (CJF). These deposits were involved in an uplift 182 S. CARLINO ET AL. Fig. 1. Digital terrain model (DTM) image of the Bay of Naples. Ischia Island is located in the western sector. Table 1. Volcanic activity phases of Ischia Older cycle Phase 1>150 000 a BP Older major pyroclastic activity Pre-Mount Epomeo Green Tuff activity Phase 2 50 000–75 000 a BP Lava dome emplacement Phase 3 55 000–33 000 a BP Younger major pyroclastic activity Younger cycle Mount Epomeo Green Tuff Phase 4 29 000–18 000 a BP Explosive and effusive activity in the Citara Formation southwestern and southestern sector Phase 5 10 000 a BP to 1302 AD Prehistoric and historical activity Chiocci et al. 2002; Cubellis et al. 2004; De Alteriis et al. 2004; Tibaldi & Vezzoli 2004; Carlino & Cubellis 2005). In general, the models used to interpret resurgence processes for large calderas – the thrust of the magma in a shallow source due to an increase in pressure or due to vesiculation; regional detumescence; or heat transfer from the magmatic basin to the surface aquifer system (Smith & Bailey 1968; Marsh 1984; Luongo et al. 1991; De Natale et al. 2001) – appear inadequate to explain resurgence in calderas of modest size, as in the case of the island of Ischia. The complexity of the problem also emerges from analysis of the models proposed since the early twentieth century. Indeed, Rittmann (1930) proposed volcano-tectonic horst mechanism, i.e. uplift by the intrusion of a shallow laccolith, to explain the structure of Mount Epomeo. More recently, Fusi et al. (1990) and Tibaldi & Vezzoli (1998) proposed that the resurgent process of Ischia was produced by volumetric variations in the subsurface magma body. Orsi et al. (1991) suggest a simple-shear stress for the resurgence, in which the source mechanism is an increase in magmatic pressure in the upper part of a shallow magma chamber. Luongo et al. (1995) and Cubellis & Luongo (1998) used a punched laccolith mechanism to model the uplift of Mount Epomeo. Acocella et al. (1997, 1999) and Molin et al. (2003), according to similar experimental models, proposed that the resurgent doming of Mount Epomeo is due to a trapdoor uplift mechanism, with a hinge in the southeastern part of the island. To remove the arbitrariness of the above solutions for the resurgence of Ischia we impose 183 CALDERA RESURGENCE OF ISCHIA ISLAND geological boundary conditions within the solution to the problem of the ground deformation. General and specific boundary conditions are deduced by high-quality field-mapping data and geochemical and geophysical surveys of the island. The bending model for Mount Epomeo