Glaciology emerged from being a descriptive branch of geology to an analytical branch of physics in the years surrounding the International Geophysical Year (1957–1958), as the result of field research in the polar regions. This period, roughly from 1950 to 1970, was dominated by tractor-train (convoy of specially designed vehicles pulling gear-loaded sleds) traverses, mainly over the Antarctic ice sheet, for collecting data on ice elevation and thickness, surface temperature, meteorology, mass balance, and geophysical properties of the bed. The goal was to understand ice sheet flow from the interior ice divides to the sea. This was also the time when the first core holes (ice cores) to bedrock were drilled at Camp Century, Greenland, and Byrd Station, Antarctica, providing the first long-term climate records. Analyzing these climate records became critical for understanding global climate change.