Atlantis was a myth, but real-life lost lands do exist.
A manned research submersible takes a rock sample from the seafloor near Brazil.
by Ker Than
A lost continent off the coast of Brazil may have been found, scientists announced this 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."
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.
Pangaea
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."
Mauritia
Scientists earlier this year announced that they had found evidence of a
drowned "microcontinent" off the coast of Africa, near the island of Mauritius.
Sand
grains from Mauritius's beaches were found to contain fragments of the
mineral zircon that were between 660 and 2 billion years old—far older
than the island itself.
One theory is that the sand
grains are remnants of Mauritia, a lost microcontinent that once existed
off the coast of Africa and which was submerged when India broke apart
from Madagascar about 85 million years ago.
Microcontinents
are shards of land broken off from continents and supercontinents. The
distinctions among the three aren't clear-cut, however, and labeling a
landmass a continent or microcontinent can be arbitrary since there are
no precise size requirements for each term.
New Zealand, for example, is actually part of a large continental structure that includes the
Campbell Plateau.
"It's not all that different in size from Australia, but because most
of it is underwater, we call Australia a continent and New Zealand an
island," Wysession said.
Microcontinents can also merge into larger structures. For example, "the north African edge of the supercontinent
Gondwana
broke up into slices like the pieces of an apple, and each of those
[microcontinents] moved north to form southern Europe," explained
Louis Jacobs, a paleontologist at Southern Methodist University in Dallas, Texas.
Beringia
Though
Asia and North America are now separated by a thin strait, it is very
shallow—about 150 feet (46 meters) deep—and when sea levels are low,
such as during ice ages, the two continents are connected by a land
bridge known as Beringia.
According to a controversial
theory, humans heading east after leaving Asia some 40,000 years ago
found their way blocked by glaciers and were forced to
settle in Beringia for thousands of years until conditions thawed enough for them to continue to North America.
Less contentious is the theory "that the
Clovis people came over from Siberia to North America about 14,000 years ago," Wysession said.
Scotland's Hidden Landscape
In
2011, geologists studying ocean-mapping data stumbled upon a previously
unknown landscape now buried beneath more than a mile of marine
sediment off the coast of Scotland.
The
hidden landscape,
which had an estimated area of about 3,861 square miles (10,000 square
kilometers), had furrows cut by rivers and peaks that were once part of
mountains.
Scientists think it was briefly elevated
above the waves by geological processes about 55 million years ago but
became submerged again after about 2.5 million years.
