Layers in Lake Sediment (IMAGE) GFZ Helmholtz-Zentrum für Geoforschung Caption Sediments from the bottom of lakes are often layered. The individual layers, called warves, preserve information from the past and can be "read" like tree rings. By identifying pollen or ashes, landscape evolution, climate and even political events can be traced. 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.