Volcanology of Ischia (Italy)
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Journal of Maps ISSN: (Print) 1744-5647 (Online) Journal homepage: http://www.tandfonline.com/loi/tjom20 Volcanology of Ischia (Italy) Alessandro Sbrana, Paola Marianelli & Giuseppe Pasquini To cite this article: Alessandro Sbrana, Paola Marianelli & Giuseppe Pasquini (2018) Volcanology of Ischia (Italy), Journal of Maps, 14:2, 494-503, DOI: 10.1080/17445647.2018.1498811 To link to this article: https://doi.org/10.1080/17445647.2018.1498811 © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps View supplementary material Published online: 02 Aug 2018. Submit your article to this journal Article views: 83 View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tjom20 JOURNAL OF MAPS 2018, VOL. 14, NO. 2, 494–503 https://doi.org/10.1080/17445647.2018.1498811 Science Volcanology of Ischia (Italy) Alessandro Sbrana, Paola Marianelli and Giuseppe Pasquini Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy ABSTRACT ARTICLE HISTORY A volcanological map of the active Ischia volcanic field that includes Vivara Island is presented. Received 10 April 2018 The volcanological map is at the 1:10,000 scale and is based on 1:5000 field mapping, geological Revised 6 July 2018 CAR.G data, and new volcanological studies. Geological data are represented on the three- Accepted 6 July 2018 ff dimensional orographic background digital terrain model of the inland and o shore areas of KEYWORDS the volcanic field. This allows a better visualization of the main morphological, volcanic, and fi Volcanological map; volcanic geological structures. Six phases were identi ed on the basis of volcanotectonic events; the field; digital terrain model; 110 volcanic units were arranged following these evolutive phases, and a Ischia; Vivara; Italy volcanosedimentary apron unit was introduced. This volcanological map enables visualization of the volcanic evolution of the Ischia volcanic field and could be useful for the evaluation of volcano-related hazards in the area. 1. Introduction Pasquarè, & Vezzoli, 1982). In a more recent paper, Ischia Island represents the emerged portion of a wide Brown, Orsi, and De Vita (2008) detail the strati- volcanic field (Bruno, de Alteriis, & Florio, 2002; Orsi, graphic framework between 75 and 50 ka, highlighting Gallo, & Zanchi, 1991) extending from the continental that volcanism was very active in this period. slope (facing westward on the Tyrrhenian batial plain) New geological maps of the volcano were recently rea- to the continental volcanic area of Campi Flegrei. It is lized in the framework of the CAR.G Project (Regione part of the Phlegraean Volcanic District (Orsi, De Vita, Campania, 2011; Servizio Geologico d’Italia, 2018). & Di Vito, 1996), the most widespread active volcanic These maps significantly improve the stratigraphy of system of the Mediterranean area, developed inside the whole successions, absolute ages, the mapping of units, Campanian Plain half graben. The PVD formed fol- recognition of eruptive centers, and knowledge of the cal- lowing the opening of the Tyrrhenian basin, along a dera resurgence and of relations of uplift phenomena and system of regional transfer faults, affecting the Tyrrhe- related epiclastic forming around the resurgent block. nian side of the Apennine chain during the Neogene Deposits that are the result of sector collapse of resurgent Quaternary evolution of the area (Sartori, 2003; Scan- block flanks are traced and mapped both on land and in done, 1979); it comprises (Figure 1(A, B)) two big vol- the marine areas surrounding Ischia. canic fields, Ischia and Campi Flegrei, fed mainly by Based on the CAR.G data and on new volcanological evolved alkaline magmas and the minor volcanic field studies, an updated volcanological map of the Ischia vol- of Procida, characterized by trachybasaltic–shoshonitic canic field that includes Vivara Island was generated in monogenic tuff and scoria cones and minor lavas this study. Geological data were placed on the three- (Brown et al., 2014; D’Antonio et al., 2013; Paoletti, dimensional (3D) orographic background digital terrain D’Antonio, & Rapolla, 2013; and references therein). model(DTM)oftheinlandandoffshore areas of the vol- Previous detailed Ischia geological maps include the canic field. This enables a better visualization of the vol- 1:10,000 geological map of Rittmann (1930), Rittman canic structure. The design of the legend on the basis of a and Gottini (1980) and the 1:10,000 map of Vezzoli simplified lithology and of volcanological features, clar- (1988). The description of the Mt Epomeo resurgent ifies the reading of the map as well as the comprehension block as being a result of a volcanotectonic mechanism, of volcanological evolution of the field. Furthermore, the mapping of lahars, and the reconstruction of the normal faults related to caldera resurgence (induced by sequence of events were described in pioneering magma injection) were distinguished from regional and works of Rittmann. Recent volcanism is well detailed normal faults interesting the whole volcanic field. in Vezzoli (1988); in its geological map, a coherent stra- This new volcanological map should be very useful for tigraphic framework of the volcanic events is based on the following reasons. The intensely urbanized island is a complete dataset of absolute ages (Gillot, Chiesa, environmentally very fragile because its morphology CONTACT Paola Marianelli [email protected] Dipartimento di Scienze della Terra, Università di Pisa, via S. Maria 53, 56126 Pisa, Italy © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. JOURNAL OF MAPS 495 Figure 1. A: Phlegrean Volcanic District (Google Earth image). B: Phlegrean Volcanic District, view from Ischia. In the foreground Castello d’Ischia spatter cone, followed by the Vivara tuff ring, by Procida volcanic field, and in the background, continental Phle- grean Fields and Somma-Vesuvius volcano. C: Castello d’Ischia spatter cone, view from North. D: Porticello cliff (southeastern island), deposits of Secca d’Ischia offshore volcano (see Figure 2). E: Pietra Martone, Mt. Epomeo Green Tuff. In picture note the normal fault wall of the resurgent block and the scar of debris avalanche. and the activity of the volcano induce hazards related to 150 ka ago (Gillot et al., 1982; Vezzoli, 1988)tothe volcanic events, such as destructive earthquakes (the last present; the last erupted deposits (Arso lavas and pyr- occurred in 2017 causing several casualties (De Novellis oclastics) date to 1301–1302 AD (Rittman & Gottini, et al., 2018), formation of mud flows and landslides, sec- 1980). tor collapses and related debris avalanches linked to vol- Volcanism develops through the building of a volca- canotectonic uplift (De Vita, Sansivero, Orsi, & Marotta, nic field made mainly by monogenic volcanoes (tuff 2006) and subsidence phenomena, and general volcanic cones, scoria cones, spatter cones and spatter ramparts, deformation processes. lava domes and lava flows) dispersed over an area of 250 km2 (Figure 2). Volcanics have mainly trachytic compositions (Vezzoli, 1988), whereas trachybasalts 2. Volcanic field history and shoshonites characterize few deposits. Several pyr- Volcanic fields develop in both continental and mar- oclastic units emplaced during paroxysmal eruptions ine environments (Passaro, De Alteriis, & Sacchi, were mapped on the island and traced in submarine 2016). Volcanic successions outcropping on the Ischia areas up to the nearby Campi Flegrei volcanic field, Island register a long history, dating from more than which is covered by several of these volcanic units 496 A. SBRANA ET AL. Figure 2. Geological and structural sketch map of Ischia volcanic field. Deposits of debris avalanches and volcanic vents are high- lighted in marine areas. Location of toponyms (numbered dots) cited in the main text is also reported. (Sbrana, Fulignati, Marianelli, Boyce, & Cecchetti, (Main Map). The resurgence deeply influenced the 2009; Sbrana et al., 2011; Servizio Geologico d’Italia, morphology and geology of the volcanic field also 2018). Some of these, which occurred between 60 and with the formation of an epiclastic and volcanic 56 ka ago, are linked to the Ischia caldera formation apron all around Mt Epomeo. Several epiclastic units, (Brown et al., 2008; Carlino, Cubellis, Luongo, & interlayered with volcanic deposits, were identified Obrizzo, 2006; Sbrana et al., 2009; Vezzoli, 1988; and during the geological survey and were linked to sector references therein). collapses inducing debris avalanches, and accelerated The uplift of a resurgent block (Mt Epomeo) charac- erosion phases of the resurgent block. Several authors terizes the central portion of the caldera (Acocella & (Carlino, 2012; Carlino et al., 2006; Rittmann, 1930; Funiciello, 1999; Carlino, 2012; Carlino et al., 2006; Sbrana et al., 2009; and references therein) link the Orsi et al., 1991; Sbrana et al., 2009; Tibaldi & Vezzoli, resurgence of Mt Epomeo and the volcanic activity 2004 and references therein). This block, tilted south- around the block to a laccolith-shaped