A glacier is a large persistent body of ice. Originating on land, a glacier flows slowly due to stresses induced by its weight. The crevasses and other distinguishing features of a glacier are due to its flow. Another consequence of glacier flow is the transport of rock and debris abraded from its substrate and resultant landforms like cirques and moraines. A glacier forms in a location where the accumulation of snow and sleet exceeds its ablation over many years, often decades or centuries.