Colombian scientists race to study once-forbidden territory before it is lost to development—or new conflict

Source: Science Magazine

TRIGANÁ, COLOMBIA—The rare travelers intrepid enough to find their way here to northern Colombia come for quiet beaches and coral reefs. Not Camilo Montes. After enduring a choppy motorboat ride across the Gulf of Urabá to this ramshackle village, he and three other geologists head into the jungle, seeking clues to a profound geological event that transformed the Americas.

The team hikes for 3 hours before reaching a spot where a creek spills gently over a mass of smooth, dark rock. They call out GPS coordinates and use rock hammers to chip off flecks, which they examine with magnifying glasses. There's no doubt about it: The rock and its pistachio-colored inclusions were formed as magma welled up and created the mountains of the Panama arc, which forms Panama and northern Colombia. "It's like a photo of when the magma was crystallizing," Montes says, bagging several kilograms of samples to take back to his lab. It's exactly what he came here hoping to find.

Montes, a geologist at the University of the North (Uninorte) in Barranquilla, Colombia, has studied rocks like these his entire career. He investigates the formation of Panama's volcanoes and their collision with South America, which linked the Americas and allowed ecosystems separated for millions of years to mingle. For decades, scientists have thought that the land bridge between the continents formed about 3.5 million years ago. Citing fossil evidence and the ages of volcanic rocks, Montes and others argue that the continents joined before 10 million years ago. If confirmed, the older date would change both how scientists analyze fossils from the two continents and how they calibrate the molecular clocks used to estimate when species diverged. "If the 3.5-million-year date is wrong, it could upend everything," says Susana Caballero, a biologist at the University of the Andes (Uniandes) in Bogotá. Dating the crystalline inclusions, Montes says, may influence that scientific debate.