scientific discipline concerned with all aspects of ice on landmasses. It deals with the structure and properties of glacier ice, its formation and distribution, the dynamics of ice flow, and the interactions of ice accumulation with climate. Glaciological research is conducted with a variety of methods. The internal structure of glaciers, for example, is studied by means of radar sounding, while glacier movement is monitored by measuring the deformation of vertical boreholes or lateral tunnels dug into the ice. Estimates of ice accumulation over large areas are made with data secured by remote sensing (e.g., with satellite-borne infrared and multispectral scanners), and the successive annual layers in glacier ice are commonly differentiated by measuring oxygen isotope ratios.