November 17, 2011
Researchers Unravel Gamburtsev Mountains Enigma
Researchers funded by the National Science Foundation may have finally found how Antarctica´s Gamburtsev Subglacial Mountains were formed, a conundrum that has plagued scientists since they were first discovered in 1958.
The international team of scientists explored the subglacial mountain range -- buried under nearly 10,000 feet of ice -- during the International Polar Year (2007-2009) by using two twin-engine aircraft equipped with ice penetrating radar, gravity meters and magnetometers.After extensive analysis, the team believes the remarkably long geological history explains the formation of the mountain range where the Antarctic Ice Sheet first formed. Findings of their research are published in the journal Nature.
The extraordinary processes, taking place over the last billion years, created and preserved a root beneath the mountains and the East Antarctic rift system -- a 1,800-mile-long fracture in the Earth´s surface that extends from East Antarctica across the ocean to India.
Named after the Soviet geophysicist who discovered them, the Gamburtsev Mountains are 750 miles long, with jagged peaks up to 8,900 feet high intersected by deep troughs and valleys. The Gamburtsev Mountains are located at high elevation and on a continent that geologically is ancient and long free of the tectonic upheaval that typically builds mountains. Yet their sharp edges clearly demonstrate they are a youthful range barely touched by the erosive forces of wind, snow and water.
“The East Antarctic rift system resembles one of the geological wonders of the world, the East African rift system,” said lead investigator Fausto Ferraccioli of the British Antarctic Survey (BAS).
“It provides the missing piece of the puzzle that helps explain the Gamburtsev Subglacial Mountains. The rift system was also found to contain the largest subglacial lakes in Antarctica,” he added.
Long before plants and animals evolved on Earth, several micro-continents collided, crushing the oldest rocks of the mountain range 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.
Between 250 and 100 million years ago -- during the age of the dinosaurs -- rifting paved the way for the supercontinent Gondwana to break apart, which included Antarctica, causing the crustal root to warm. The rejuvenated crustal root, together with the East Antarctic Rift forced the land upwards again reforming the mountains.
Deep valleys were carved from glaciers and rivers helping to uplift the peaks to create the spectacular landscape of the Gamburtsev Mountains, which resemble the European Alps. Then, about 34 million years ago, when the East Antarctic Ice Sheet formed, it covered the Gamburtsevs and protected them from erosion.
“Understanding the origin of the Gamburtsevs was a primary goal of our International Polar Year expedition. 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 — and that it provides the missing piece of the puzzle that helps explain the Gamburtsev Subglacial Mountains. The rift system was also found to contain the largest subglacial lakes in Antarctica,” explained Ferraccioli.
“Resolving the contradiction of the Gamburtsev high elevation and youthful Alpine topography by piecing together the billion year history of the region was exciting and challenging,” said co-author Carol Finn of the US Geological Society (USGS).
“We are accustomed to thinking that mountain building relates to a single tectonic event, rather than sequences of events. The lesson we learned about multiple events forming the Gamburtsevs may inform studies of the history of other mountain belts,” she said.
“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 co-author, Dr Robin Bell of Columbia University´s Lamont-Doherty Earth Observatory.
“It is very fitting that the initial results of Antarctica's Gamburtsev Province (AGAP) 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 of the AGAP project 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.”
The International Polar Year is a concentrated effort by scientists from 60 nations to study the Polar Regions. NSF´s Office of Polar Programs manages the US Antarctic Program, through which it coordinates all US research and logistical support for science on the southernmost continent and its surrounding oceans.
The seven nation IPY/NSF team made up the Antarctica´s Gamburtsev Province (AGAP) project, consisting of scientists from Australia, Canada, China, Germany, Japan, the United Kingdom and the United States.
Scientists noted that the results of their research have a special significance in a year that marks the centennial of the achievement of the South Pole by Norwegian explorer Roald Amundsen.
Another polar expedition research team, led by Briton Robert F. Scott, laid the foundations for modern Antarctic science by making systematic scientific observations of various phenomena on the southernmost continent. Although Scott and his men never returned from their polar expedition, they did not abandon fossils and rocks gathered on their journey as a legacy to scientific exploration.
Image 1: A British Antarctic Survey aircraft equipped with the aerogeophysical platform flying over the AGAP-N field camp. The US, UK, Australian, German and Chinese flags show the nations that provided the main contributions to the airborne geophysics component of AGAP during IPY. Canadian and Japanese teams were deployed at the US camp at AGAP South.
Image 2: Researchers have probed the depths under Antarctic ice to reveal a map of the Gamburtsev Mountains (see inset to the right). Credit: Zina Deretsky, National Science Foundation, Gamburtsev topography by Abdulhakim Abdi, Lamont-Doherty Earth Observatory of Columbia University
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- Lamont-Doherty Earth Observatory