Antarctica's "Ghost" Mountains ExplainedAlps-like peaks created during breakup of ancient supercontinent, study says.
An illustration of buried mountains in Antarctica.
A 3-D image of Antarctica's Gamburtsev Mountains.
Illustration courtesy British Antarctic Survey
Richard A. Lovett
for National Geographic News
Published November 16, 2011
Stuck in a "deep freeze" for millennia, a mysterious mountain range deep under the Antarctic ice is finally coming to light.
The Gamburtsev Mountains appear to be part of a rift—a series of ridges that form where Earth's tectonic plates separate—that once stretched about 1,800 miles (3,000 kilometers) long, a new study says.
The rift may have been created about 250 million years ago, during the breakup of the ancient supercontinent Gondwana. That landmass included today's East Antarctica, India, Africa, and Australia, said study co-author Fausto Ferraccioli of the British Antarctic Survey in Cambridge, England.
Buried under about three miles (five kilometers) of ice, the Gamburtsev Mountains weren't even found until the mid-1900s, when Russian explorers recorded unusual gravity fluctuations emanating from beneath the ice. (See a high-resolution Antarctic map.)
Subsequent studies have revealed a giant range, on par with the European Alps, with the highest peaks rising nearly 15,000 feet (4,500 meters).
"These are the least understood mountain ranges on Earth," Ferraccioli said. "It is as exciting as exploring another planet."
Taking a Mountain MRI
An international team of geophysicists recently flew over the Gamburtsev Mountains and used radar to peer beneath the ice and take detailed gravitational and magnetic readings.
The radar shows the mountains' physical features, while the magnetic and gravity readings allow scientists to peer more deeply into the crust. Taken together, the three tools are like taking an MRI image of the mountains, from their surfaces all the way to their roots, said Ferraccioli, whose study appears tomorrow in the journal Nature.
(Related: "First Detailed Pictures: Antarctica's 'Ghost Mountains.'")
Based on this data, Ferraccioli's team pieced together a complex picture of the mountains' history.
Today, the Gamburtsevs appear to sit atop an older range, probably formed during a period of major supercontinental assembly, either 1.1 or 1.8 billion years ago, when East Antarctica was being assembled from smaller pieces, Ferraccioli said.
That ancestral range then eroded, but about a 20-mile-deep (32-kilometer-deep) root remained in the underlying mantle. (See "Scientists to Drill Earth's Mantle, Retrieve First Sample?")
Antarctic Mountains Put in "Deep Freeze"
Later, when the giant rift formed—as also occurred in East Africa's famous Rift Valley—the heat from Earth's interior warmed the material in the long dormant root, causing this material to expand and float higher in the mantle. (Learn more about the inside of the Earth.)
As a result, the mountains began to uplift again about a hundred million years ago, when the Indian continent broke off from Antarctica and started its northward migration to its present location.
Then, about 34 million years ago, the Antarctic ice sheet began forming.
"The whole [mountain range] was encased in ice and literally preserved in the deep freeze," Ferraccioli said.
"Otherwise they would have been eroded, and we wouldn't have seen much at all."
http://news.nationalgeographic.com/news/2011/11/111116-antarctica-mountains-mystery-ice-science-earth/
