ORIGINAL PAPER Active hydrothermal fluids circulation triggering small- scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece) Stefania Venturi 1,2 • Franco Tassi 1,2 • Orlando Vaselli 1,2 • Georges E. Vougioukalakis 3 • Heba Rashed 2 • Christos Kanellopoulos 4 • Chiara Caponi 2 • Francesco Capecchiacci 1,2 • Jacopo Cabassi 1,2 • Andrea Ricci 5 • Luciano Giannini 1,2 Received: 3 January 2018 / Accepted: 9 April 2018 Ó Springer Science+Business Media B.V., part of Springer Nature 2018 Abstract In 2001–2002, two ground collapses occurred in the island of Nisyros (Aegean Sea, Greece), which formed a 600 m long and up to 5 m wide fissure in the vegetated central part of the Lakki Plain caldera. The fissure was alternatively ascribed to tensional stress release and hydrothermal alteration. In this study, we present original data of diffuse CO 2 soil fluxes, soil temperatures, mineralogical and chemical composition of the caldera- filling deposits exposed on the fissure walls, and chemical and isotopic composition of interstitial soil gases collected from: the bottom of the fissure, the adjacent vegetated areas, & Stefania Venturi stefania.venturi@igg.cnr.it Franco Tassi franco.tassi@unifi.it Orlando Vaselli orlando.vaselli@unifi.it Georges E. Vougioukalakis gvoug@igme.gr Heba Rashed hebaafef.rashed@unifi.it Christos Kanellopoulos ckanellopoulos@gmail.com Chiara Caponi chiara.caponi@unifi.it Francesco Capecchiacci francesco.capecchiacci@unifi.it Jacopo Cabassi jacopo.cabassi@igg.cnr.it Andrea Ricci ricciandrea89@gmail.com Luciano Giannini luciano.giannini@gmail.com 123 Nat Hazards https://doi.org/10.1007/s11069-018-3318-8