Mica Mine Unconformity (IMAGE) Dartmouth College Caption In Colorado’s Ladder Canyon, rocks that differ in age by about a billion years sit together across the Great Unconformity. Credit C. Brenhin Keller Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND 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.