The Antarctic ice sheet sits like a shallow dome on the continent’s surface. Over eons, the weight of accumulating ice in the continental interior forces outlying ice down the dome’s slope and into the sea. No one really knows how long ice has covered Antarctica. Some geologists say that as recently as 3 million years ago, Antarctica had a relatively mild climate and was even forested. David Sugden thinks that’s unlikely, particularly in light of a recent expedition he made to the frozen continent. He discovered a fragment of a long-vanished glacier that appears to be at least 8 million years old.
Sugden, a geologist at the University of Edinburgh, was trying to date an ancient volcanic eruption in East Antarctica when he and his colleagues uncovered the old ice. They were in Beacon Valley, a boulder- filled area between glaciers, collecting volcanic ash from a seven-foot- deep, V-shaped fissure ...
