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They wanted to visit it because previous surveys showed it is covered in moraines pushed into their present location from the ancient movements of the East Antarctica Ice Sheet.
“We use those mountains as a yardstick basically because as the ice sheet grows or shrinks, it goes up and down the sides of these mountains, and it leaves moraines as it does so,” Bromley said.
“We look for glacial deposits, and we use all manner of different means to figure out how old they are.” The team collected samples from these glacial deposits, also known as moraines, which are essentially piles of rocks, sand and dirt left behind by flowing ice.
By measuring the amount of cosmic radiation the rocks have been exposed to, the research team can map out the reach of ancient glaciers at different points in the past.
“My student and I are wading through them now, just crushing them in the lab, turning them into sand and pulling out the pyroxene crystals,” Bromley said.“We want to know what the East Antarctic Ice sheet did during the Pliocene because that was believed to be warmer than present,” Bromley said. As a glacier cascades across the landscape, rocks from nearby cliffs fall onto it and it picks up all manner of debris lying on the ground. The internal flow of the glacier gradually pushes that material to the edges of the ice where they fall out, forming moraines along the rim of the glacier.“That, at the moment, is the best analogue we have for the greenhouse future.” Their project is supported by the National Science Foundation, which manages the U. The site where the team traveled this season, Roberts Massif, is a series of ice-free peaks and cliffs that sticks out of the East Antarctic Ice Sheet at the head of Shackleton Glacier.Isolating these crystals is a time-consuming process, and the team likely will spend the better part of a year separating them from the rocks they collected.
Each time Bromley is done isolating the pure crystals from a sample, he transfers them to Gregory Balco at the Berkeley Geochronology Center to determine their ages.“If the rock is part of a moraine, it tells you when that ice was last at that limit.” Walking along the edges of the moraines, the team searched for rocks that look like they haven’t been disturbed since they were spit out of the ice.When they found ones that looks promising, they pulled out their chisels and hammers and chipped off a hunk of rock from the top.There, they’ve started processing them and grinding them up to their constituent parts.