hydrothermal system (IMAGE) Johannes Gutenberg Universitaet Mainz Caption Illustration of the hydrothermal system in the center of the caldera at Campi Flegrei from 2011 to 2013 (light yellow ellipse): the central reservoir expanded, increasing stress and producing earthquakes in 2019/2020. Credit ill./©: Simona Petrosino, Luca De Siena / CC BY Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.