“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.Powerful electromagnets then remove all of the iron material.Pyroxene crystals then have to be separated out using heavy liquids and then doused in a bath of 2 percent hydrofluoric acid to etch away any lingering groundmass.Every part of the Earth's surface is constantly exposed to a low level of cosmic radiation from energetic particles, mainly neutrons and protons, originating in outer space. But if you stack up enough mass in the path of a cosmic-ray particle, the incoming particle eventually hits one of the atoms that make up that mass and stops."This can be a problem for things like electronics." Balco 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.
“If you know the rate at which those nuclides are produced in the rock and you can measure how much you have inside the rock, then you can calculate how long that rock has been exposed on the hillside, exposed to the atmosphere,” Bromley said.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."If you are running a large data center with thousands of server computers, you have to worry about cosmic-ray impacts causing errors every now and then." In the outer layers of exposed rocks, cosmic-ray impacts break apart atoms and produce rare nuclides like beryllium-10 or helium-3, that are not produced by any other natural process.A thick enough layer of glacier ice also stops the cosmic-ray flux, shielding the rocks below from nuclide production. It never sees this cosmic-ray flux until the ice sheet spits it out at the side in one of these moraines,” Bromley said.