aciers

Glaciers (the standard term; aciers is a common misspelling) are large, persistent masses of ice that form on land from the accumulation, compaction, and recrystallization of snow over many years. They originate where snowfall exceeds melting, allowing snow to accumulate and transform into firn and, with increasing depth and pressure, into glacier ice. The weight of the ice causes it to deform and flow slowly under gravity, moving ice from higher, colder regions toward lower, warmer areas. This movement creates crevasses and seracs and shapes the surrounding terrain.

Glaciers occur in several forms, including valley glaciers that flow down valleys, ice sheets that cover large areas (Greenland and Antarctica), cirque and horn glaciers in mountainous regions, piedmont glaciers that spread at their termini, and outlet glaciers that drain ice sheets.

The health of a glacier is governed by its mass balance—the difference between annual accumulation and ablation. If accumulation exceeds ablation, the terminus advances; if ablation exceeds accumulation, it retreats. Glaciers sculpt landscapes by eroding rock, transporting material, and producing landforms such as U-shaped valleys, cirques, and moraines. They store climate information in ice cores and are sensitive indicators of past and present climate change. Glaciers are important sources of freshwater for many regions and can release large volumes of water through glacial lake outburst floods. They are monitored with satellites, ground surveys, radar, LiDAR, and GPS.

Globally, glaciers occur in high mountain regions and polar areas, including the Andes, the Alps, the Himalayas, Alaska, and Greenland and Antarctica. Many glaciers have retreated in recent decades as global temperatures rise.