Pulling Core (image) The Earth Institute at Columbia University Share Print E-Mail Caption Coauthor John Geissman of the University of Texas, Dallas, pulls a drilled-out core of rock used in the study. The drilling penetrated more than 1,500 feet, going back some 250 million years. Credit Kevin Krajick/Lamont-Doherty Earth Observatory Usage Restrictions Credit must be given. 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.