Superior Craton, Canada (image) Rice University Share Print E-Mail Caption Water flowing over and eroding ancient rock exposed at the Superior Craton in Canada, represented here by the Scenic High Falls in Wawa, Ontario, holds clues to the development of Earth's atmosphere 2.7 million years ago. A study led by Rice University showed the sulfur record held by the rock marked the dramatic change in the planet's atmosphere that gave rise to complex life. Credit Tom Samworth/www.itsabouttravelling.com Usage Restrictions For news reporting purposes only. 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.