Geologist challenges age of land bridge connecting Americas

Despite the belief that the strip of land connecting North and South America is older than dirt, it is actually quite young.

After analyzing data from rocks, fossils and genetic studies, a team of international researchers found the land bridge, known as the Isthmus of Panama, formed 2.8 million years ago. This finding contradicts recent studies arguing the land bridge came together anywhere from 6 to 23 million years ago, and it offers insight about the evolution and migration of animals in the region.

FIU geologist and paleontologist Laurel S. Collins is one of the 35 researchers who authored the study. She examined marine fossils to determine the rate at which the isthmus arose from the ocean.


A cargo ship in the Panama Canal passes through volcanic rocks that helped form the Isthmus of Panama. Credit: Aaron O’Dea

“The formation of the Isthmus of Panama happened recently enough that fossil and geochemical records are well preserved, so they can be read accurately at a fine chronological scale,” said Laurel Collins, a professor in the FIU Department of Earth and Environment and research associate with the Smithsonian Tropical Research Institute.

The study, led by the Smithsonian Tropical Research Institute, was recently published in Science Advances.

North and South America separated when the supercontinent Pangaea broke up round 200 million years ago. Eventually, the two landmasses slid back together. As they reconnected, a volcanic mound on the Caribbean tectonic plate collided with South America and rose above the ocean. The isthmus closed the seaway between the Pacific and Atlantic Ocean and connected North and South America.

Dubbed by researchers as the greatest natural experiment ever, the formation of the Isthmus of Panama was a pivotal event in the planet’s history, driving major changes at sea and on land. The bridging of the two continents allowed previously isolated land animals to migrate and plant seeds to be easily scattered by wind, water and the moving animals. It also intensified the Gulf Stream, a powerful ocean current originating in the Gulf of Mexico and stretching up along the North American eastern seaboard, which ultimately led to the formation the northern hemisphere’s ice sheets and glaciers. The separation of the oceans helped create ideal conditions for coral reefs to thrive in the warm clear waters of the Caribbean Sea. It also isolated marine species, including snails, clams and fish, and caused new species to evolve on either side. According to the researchers, knowing when the isthmus formed is critical to answering questions about the ecology, evolution and the origin of modern day plants and animals throughout the Americas.

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