International research team traces geological history of ice-buried range, including previously undiscovered evidence of rifting
By Summit Voice
SUMMIT COUNTY — A comprehensive study of a remote Antarctic mountain range buried by ice will help geologists understand how other mountain ranges form, and also fills in some of the missing pieces in the global tectonic puzzle, according to a team of scientists who found evidence of a vast tectonic rift beneath almost 10,000 feet of ice.
“It was very exciting and very difficult,” said Colorado-based U.S. Geological Survey researcher Dr. Carol Finn, co-author of the research being published this week in the journal Nature. “This was huge hole in the data sets,” she said, explaining that the history of the Gamburtsev Subglacial Mountains — buried beneath the vast East Antarctic Ice Sheet — shows that mountain-building can’t always be pinned to a single mountain-building event.
A seven-nation team of scientists explored the mountains during the International Polar Year (2007- 09) by using two twin-engine aircraft equipped with ice penetrating radars, gravity meters and magnetometers. By analyzing the new data, the researchers describe the extraordinary processes — which took place over the last billion years — that created and preserved a root beneath the mountains and the East Antarctic rift system, a 3,000-kilometer-long fracture in the earth’s surface that extends from East Antarctica across the ocean to India.
“It was fascinating to find that the East Antarctic rift system resembles one of the geological wonders of the world – the East African rift system,” said Dr. Fausto Ferraccioli, British Antarctic Survey. It provides the missing piece of the puzzle that helps explain the Gamburtsev Subglacial Mountains,” he said, adding that the rift system contains the largest subglacial lakes in Antarctica.”
“The interesting thing is, they look similar to the Rockies,” Finn said, explaining that the Antarctic Range is similar in length and width, but that the Rockies have been weathered, while the Gamburtsevs are preserved by the thick ice cover.
One billion years ago, before animals and plants evolved on Earth, several continents (or micro-continents) collided, crushing the oldest rocks of the Gamburtsev Mountains together. This event formed a thick crustal root extending deep beneath the mountain range. Over time these ancient mountains were eroded but the cold dense root was left behind.
Finn said geologists had wondered since the range was discovered in 1958 how such a youthful-looking range developed atop an ancient and seemingly dead base.
During their research, the team discovered that, about 250-100 million years ago — when dinosaurs walked the Earth — rifting paved the way for the supercontinent Gondwana to break apart, which included Antarctica, causing the old crustal root to warm, and resulting in a rebirth of the Gamburtsevs.
This rejuvenated crustal root, together with the East Antarctic Rift, forced the land upwards again to reform the mountains. Rivers and glaciers carved deep valleys and this helped uplift the peaks to create the spectacular landscape of the Gamburtsevs, which resemble the European Alps. The East Antarctic Ice Sheet, which formed 34 million years ago and covers 10 million square kilometers of the planet (an area the size of Canada), protected the mountains from erosion.
“The next steps will be to assemble a team to drill through the ice into the mountains to obtain the first rock samples from the Gamburtsevs. Amazingly, we have samples of the moon but none of the Gamburtsevs. With these rock samples we will be able to constrain when this ancient piece of crust was rejuvenated and grew to a magnificent mountain range,” said Dr. Robin Bell, of Columbia University’s Lamont-Doherty Earth Observatory.
“It is very fitting that the initial results of Antarctica’s Gamburtsev Province project are coming out 100 years after the great explorers raced to the South Pole,” said Alexandra Isern, program Director at the National Science Foundation. “The scientific explorers … worked in harsh conditions to collect the data and detailed images of this major mountain range under the East Antarctic Ice Sheet. The results of their work will guide research in this region for many years to come.”