Shear Zone (IMAGE) Brown University Caption The region in color denotes a shear zone where the continent of Gondwana slip atop proto-North America 300 million years ago. Credit Fischer Lab/Brown University Usage Restrictions None 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.