Zircon Crystal Showing 'Tree Rings' that Mark Heating Events (image) Arizona State University Share Print E-Mail Caption The lines crossing this zircon crystal diagonally near its center show where the NanoSIMS analyses were made. The dark concentric lines were produced by successive events in the magma, including the heating events this research focused on. The large black circle marks where a laser was used to analyze the isotopic composition of the zircon. Credit Photo by Allison Rubin Usage Restrictions No restrictions when used in connection with reportage on this story. Share Print E-Mail 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.