A glacier is a long-lasting mass of dense ice that continuously shifts under its own weight; it develops when the accumulation of snow surpasses the rate of ablation (melting and sublimation) over many years, often over centuries. Glaciers gradually deform and flow due to the stresses created by their mass, resulting in features like crevasses, seracs, and other distinct characteristics. They also erode rock and material from their base, forming landforms such as cirques and moraines. Glaciers exist solely on land and are separate from the much thinner ice found on seas and lakes, which forms on the surfaces of water bodies.
