Investigating the Orocopia Schist (IMAGE) University of Wyoming Caption UW Assistant Professor Jay Chapman teaches a winter-term field course in southern Arizona, during which students were able to investigate the Orocopia Schist in person. Chapman is the author of a new paper that suggests the rock originated as sand and mud subducted off the coast of California around 75 million years ago, then returned to the Earth’s crust by rising up through the mantle as enormous diapirs. Credit University of Wyoming Usage Restrictions None License Original 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.