A lost continent off the coast of Brazil may have been found, scientists announced last week.
Granite boulders dredged from the seafloor off the coast of South America two years ago could be remnants of a long-vanished continent, according to Roberto Ventura Santos, the geology director of Brazil's Geology Service.
"This could be the Brazilian Atlantis," Santos told reporters, adding that he was speaking metaphorically and not claiming to have found the legendary sunken world. "Obviously, we don't expect to find a lost city in the middle of the Atlantic," he said.
Santos and his team speculated that the granite-a relatively low-density rock found in continental crust-belonged to a continent that was submerged when Africa and South America drifted apart and formed the Atlantic Ocean about 100 million years ago.
But Michael Wysession, an Earth and planetary scientist at Washington University in St. Louis, noted that granite can find its way onto the seafloor through other means. "There are pieces of granite in the middle of the seafloor that date to about 800 million years ago when we had a snowball Earth scenario and there were large pieces of rock embedded in ice rafts"-mobile glaciers, essentially-"all over the ocean," explained Wysession, who was not part of the discovery. "As those ice rafts were melting, large blocks of rock dropped down all over the seafloor."
A manned research submersible takes a rock sample from the seafloor near Brazil. Video still courtesy CPRM
Wysession thinks that because the ocean floor has been extensively mapped with satellites, it is unlikely that evidence for any major lost continent will be found. "There's nothing that big that's hidden down there," he said.
The Atlantis-like lost, hidden, or fantastic world is a common theme in fiction. There are J. R. R. Tolkein's Middle Earth and James Hilton's Shangri-La, not to mention Lewis Carroll's Wonderland. The original lost land, Atlantis, was first mentioned by Plato around 360 B.C. According to Plato, Atlantis sank into the earth and drowned beneath the seas. Real continents rarely disappear in such dramatic fashion. "Continents by definition are made of low-density rock and cannot be subducted deep into the earth," explained Staci Loewy, a geologist at the University of Texas at Austin.
Nonetheless, there are real "lost lands" like the Brazilian "Atlantis" that have disappeared from view because of rising seas or the geological upheavals of plate tectonics and erosion. "Parts of continents can be worn down by erosion, and fragments can be broken off and isolated as microcontinents when larger continents break apart," Loewy said.
Here are some actual "lost lands" discovered by science.
A supercontinent believed to have formed around 300 million years ago, Pangaea was an enormous landmass that later broke up to eventually form the continents we know today.
Scientists now think several other supercontinents-such as Kenorland, Columbia, and Rodinia-existed before Pangaea, but the shapes of these ancient land masses are unclear.
Rodinia, for example, was a supercontinent thought to have been formed about one billion years ago; it's believed that it subsequently broke apart to form Pangaea.
"Those pieces are now part of the modern continents, but they have been significantly altered by one billion years of plate tectonics and erosion such that reconstructing the supercontinent of Rodinia is very difficult," explained Loewy.
While they appear stationary, Earth's landmasses shift around over geologic time, carried across the planet's surface by the slow, grinding movement of enormous, shell-like plates.
"The surface of the earth is made up of a rigid layer called the lithosphere; the lithosphere is broken into numerous pieces referred to as tectonic plates," Loewy explained.
"These plates move around the surface of the Earth, colliding into each other, creating mountains such as the Himalaya and Andes; pulling apart from each other, creating volcanic ridges in the middle of oceans like the mid-Atlantic Ridge; and sliding past each other, such as in the San Andreas Fault in California."
All content for this article courtesy of the May issue of National Geographic. For full article and more photos, click here.
Unsettled weather will stretch across the United Kingdom on 27th November as millions set out in search of the best Black Friday deals on offer.Read Story >