Getting sediments from a lake (IMAGE) GFZ Helmholtz-Zentrum für Geoforschung Caption From a raft the team uses a hollow cylinder to punch through the lake bottom thus getting sediments with layers. The layers are called warves and preserve traces from historic developments and landscape changes, e.g. pollen or ashes. Credit Achim Brauer/GFZ Usage Restrictions Credit must be given to the creator. License CC BY 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.