The Garbh Eileach Formation (IMAGE) University College London Caption Co-author Anthony (Tony) Spencer standing on the Garbh Eileach Formation. The rocks record a gradual transition from the warm tropical world of the Tonian period into the snowball Earth of the Cryogenian period. Credit Elias Rugen Usage Restrictions To be used with credit License Licensed 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.