glacier

A mass of ice of considerable thickness that forms on the terrain through the accumulation of snow and its subsequent compaction and recrystallization. The whole is endowed with slow movement, flowing downhill. Glaciers originate in a snow basin (cirque) formed in a high mountain area. As the ice mass (tongue) moves down the slope, it fractures and drags a large quantity of rocky material (moraine), eroding the valley through which it flows and widening it. The evolution of a glacier depends fundamentally on the behavior of air temperature and precipitation. At present, most of the Earth's glaciers are losing mass, with a consequent retreat, which is interpreted as a clear sign of global warming.