Despite ages of exploration, the planet still keeps many secrets. Until now, they included what may be a submerged island off the coast of Brazil. Researchers from the University of São Paulo (USP) studied this area known as Rio Grande Rise, which is a chain of seamounts and possibly a continental plateau basalt created from lava remnants. The Rio Grande Rise (RGR) has always been considered part of international waters, but now Brazil requested a border extension to include this sunken, mineral-rich island.
“A lost continent”
The Rio Grande Rise is estimated to be about 1,200 kilometers from Brazil. After a decade of studying this area, investigators believe it may have become the same size as Spain. Some people even refer to it as “a lost continent”. It was first discovered in 2018 while a team of British and Brazilian researchers explored the seafloor around this volcanic plateau. But over 2,100 feet below the surface, they found layers of red clay.
Evidence of a former island
“You just don’t find red clay on the seabed,” said Bramley Murton, a marine geologist who was on the expedition, to EOS. “The deposits looked like tropical soils.” Additionally, the team found many minerals in the soil typical of volcanic rock alterations. This includes goethite, hematite, kaolinite, and oxidised magnetite. This indicates the area wasn’t always underwater.
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“An island frozen in time”
In a 2023 study, the scientists examined the clay’s mineral makeup and decided it was formed by open-air weathering in tropical humidity and heat. This hints at the idea that this mass beneath the sea was once an island. “Imagine a lush tropical island slipping beneath the waves and lying frozen in time. That’s what we’ve uncovered,” said Murton, who was one of the co-authors.
“A Cretaceous version of Iceland”
Although it’s a recent discovery, the origin of the RGR dates back much farther. It reportedly began as a mantle plume under the mid-ocean ridge in the Atlantic creating a burst of volcanism. The rise that followed “started life as a Cretaceous version of Iceland,” said Murton. It would’ve been covered in vegetation. And keep in mind, the total area of Rio Grande Rise would’ve been five times larger than Iceland. As the volcanic eruptions lessened, the plateau drifted across the ocean, closer to South America, and submerged itself.
The proof is in the clay
“These red clays are exactly the same, chemically and mineralogically, as the red earth or terra roxa we find all over Brazil,” said Luigi Jovane, a marine geologist from the University of São Paulo, coauthor of the study, and lead investigator of the RGR. “We are confident that they represent the in situ, weathered upper surfaces of the lavas.” He therefore concluded that the red clays are “conclusive proof that this was once an island.”
Tens of millions of years old
In an official statement, Jovane further explained: “Geologically speaking, we discovered that the clay was formed after the last volcanic activity occurred 45 million years ago. The formation therefore dates from between 30 million and 40 million years ago. And it must have been formed as a result of these tropical conditions.” He added that Brazilian officials are requesting this former island become recognized as part of Brazil’s continental shelf.
A gold mine of minerals
RGR is desirable because of all of the resources it may offer. Earlier studies indicate it contains valuable minerals like tellurium, nickel, cobalt, and lithium. These materials may be key to sustainable technology that doesn’t depend on fossil fuel, making it even more alluring for potential owners. Therefore, Jovane states that a group of scientific experts are examining this ecosystem in detail to determine the sustainability and impact of extraction.
Brazil’s request for ownership
This area holds much economic potential. But it cannot be extracted since it is in international waters and thereby under the protection of the International Seabed Authority. It remains to be seen if Brazil’s petition to extend its continental shelf will be accepted. However, it will also need to prove it can mine sustainably. Although the country has legislation for mining on land, none exists for seabed mining international waters.
Consider sustainability
“To know whether resources can be viably extracted from the seafloor, we need to analyze the sustainability and impacts of this extraction,” Jovane said. “When you interfere with an area, you have to know how this will affect animals, fungi and corals, and understand the impact you’ll have on the cumulative processes involved.”
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