Mountains March (image) Brown University Share Print E-Mail Caption The rise of the Rockies extended from British Columbia to Nevada in three phases between 56 and 23 million years ago. The rising mountains dried out the interior, preparing mammals for a major climate change event 34 million years ago, researchers say. European mammals were not so prepared. Credit Courtesy of Eronen et. al. Usage Restrictions with credit 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.