What is a glacier?
A glacier is a large land-based mass of ice formed from compacted snow that moves under its own weight.
Definition and processes
Core concept Accumulated snow becomes firn and then dense ice. Gravity causes internal deformation or sliding at the base; the balance of accumulation and melting shapes glacier size. How it is studied Satellites, field measurements and mass-balance studies track motion and thickness. Moving ice transports rock and sediment and can sculpt valleys.
Applications and caveats
Why it matters Glaciers store freshwater and evidence of past climate. Melt timing affects downstream flow, while loss of land ice that reaches the sea can raise sea level. Common misunderstandings Sea ice formed on water differs from a glacier formed on land. A retreating terminus does not mean the ice stopped flowing forward; net loss and forward motion can coexist.