Ancient Soils (image) University of California - Riverside Share Print E-Mail Caption This photo shows one-billion-year-old weathering profiles from Michigan. Ancient soils like these provide evidence for low atmospheric oxygen levels through much of Earth's history. Credit Noah Planavsky. Usage Restrictions None 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.