Mystery of 'ghost mountains' solved

Posted by Kate Taylor

Scientists have solved the mystery of how a mountain range as big as the Alps came to exist deep beneath the East Antarctic Ice Sheet.

The Gamburtsev Mountains were first discovered in 1958, buried under two miles of ice. And following an exploration of the mountains, using two twin-engine aircraft equipped with ice penetrating radars, gravity meters and magnetometers, the researchers say they've uncovered the process of how they came to be formed.

A billion years ago, before animals and plants evolved on Earth, several land masses collided, crushing the oldest rocks of the mountain range together, they say.

This formed a thick crustal root extending deep beneath the mountain range - which remained even after the ancient mountains were eroded.

Around 250-100 million years ago, rifting paved the way for the supercontinent Gondwana - which included Antarctica - to break apart, causing the old crustal root to warm.

This rejuvenated crustal root, together with the East Antarctic Rift forced the land upwards, reforming the mountains. The East Antarctic Ice Sheet, which formed 34 million years ago and covers 10 million square kilometers, protected the mountains from erosion.

"We are accustomed to thinking that mountain building relates to a single tectonic event, rather than sequences of events," says Dr Carol Finn from US Geological Survey.

"The lesson we learned about multiple events forming the Gamburtsevs may inform studies of the history of other mountain belts."

The next stage of research will be to drill through the ice and into the mountains, to obtain the first rock samples from the Gamburtsevs.
 
"Amazingly, we have samples of the moon but none of the Gambutsevs," says Dr Robin Bell of Columbia University.

"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."