Liustikud

Liustikud (glaciers) are large masses of recrystallized water that form on land from accumulated snowfall that persists for many years and slowly deforms and flows under its own weight. They originate when snow accumulates faster than it melts and is buried by newer snow, gradually compressing into firn and eventually into glacier ice. Glaciers move and deform plastically, advancing or retreating depending on the balance between accumulation and ablation (melting and calving) at their terminus. A common concept is the equilibrium line, above which snow persists and below which ablation dominates.

Glaciers come in several forms, including valley glaciers that flow down mountain valleys, ice sheets that cover large regions, cirque or bowl-shaped glaciers that occupy depressions, and piedmont or tidewater glaciers that spread at their ends. Surface features such as crevasses, seracs, and moraines arise from movement and seasonal melt.

Glaciers are important freshwater reservoirs and are sensitive indicators of climate change, with many experiencing retreat and thinning as temperatures rise and precipitation patterns shift. Melting and calving from glaciers add water to rivers and, for land-terminating ones that reach the sea, contribute to global sea-level rise.