Lake Sediment Shows Fire History (IMAGE) University of Wyoming Caption University of Wyoming doctoral candidate John Calder holds sediment cores taken from Seven Lakes in the Mount Zirkel Wilderness Area of northern Colorado. Calder and his colleagues examined charcoal deposits in 12 lakes in and near the wilderness area, finding that wildfires burned large portions of that area during a documented spike in temperatures in North America starting about 1,000 years ago. Credit Bryan Shuman Usage Restrictions None 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.