Scientists have uncovered evidence that a vast tropical island once stood in the South Atlantic before sinking beneath the waves over 40 million years ago. The discovery, published in Scientific Reports, is reshaping Earth’s history while fuelling Brazil’s bid to expand sovereignty into international waters.
The site, known as the Rio Grande Rise, lies 650 meters below sea level off Brazil’s coast. Once thought to be a volcanic plateau, fresh analysis reveals bands of red tropical clay trapped between hardened lava flows proof that the landmass once stood above sea level, weathered by rain and supporting vegetation. “This clay didn’t come from continents or ocean currents,” said lead researcher Luigi Jovane of the University of São Paulo. “It formed in place, when the island was exposed to tropical weathering for millions of years.”
The region’s volcanic history dates back to the Eocene epoch, some 44 million years ago, when Earth was far warmer and the Rio Grande Rise may have towered up to 2,000 meters above sea level.
But the story is not just scientific. Brazil has formally requested the UN to extend its continental shelf to include the Rio Grande Rise, potentially giving it sovereign rights over the seabed. The area is believed to hold vast deposits of lithium, cobalt, nickel and tellurium minerals vital for electric vehicles and renewable energy.
The claim faces hurdles. The Rio Grande Rise lies beyond Brazil’s exclusive economic zone, under the jurisdiction of the International Seabed Authority (ISA). Brazil must prove geological continuity with its shelf and pass strict environmental impact studies before any mining begins. Scientists warn that the deep-sea ecosystems remain poorly understood. “We’re dealing with unique and ancient marine systems,” Jovane cautioned.
For geologists, the site is a rare record of Earth’s tectonic and climatic shifts, comparable to the Deccan Traps in India. For policymakers, it represents a strategic prize at the crossroads of science, resource competition, and international law. If Brazil’s claim succeeds, it could transform the nation into a major player in the global green energy race.