Pumice Stone (IMAGE) Johannes Gutenberg Universitaet Mainz Caption Pumice stone from the 2014 explosive eruption of Kelud is shown. Credit photo/©: Mike Cassidy, JGU Usage Restrictions This image may only be used in connection with the press release "Cyclic change within magma reservoirs affects the explosivity of volcanic eruptions", published by Johannes Gutenberg University Mainz on November 30, 2016. License Licensed content 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.