Development of the Isthmus of Panama (IMAGE) Max Planck Institute for Marine Microbiology Caption Development of the Isthmus of Panama. The Isthmus separates the Tropical Eastern Pacific Ocean from the Caribbean Sea. It closed about 2.8 million years ago. Credit Nathalie Renier Usage Restrictions Only to be used in the context of this publication and citing the correct copyright. 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.