Kettles are landforms created by melted water from glaciers, a process called "fluvioglacial." When warming weather conditions cause a glacier to start melting, large blocks of ice can break off in a process called "calving." Rather than melting on the surface of the ground, the ice block can get partially or totally buried by dirt, rocks, and plant matter - the "sediment" carried in the glacier together with its ice content. This sediment piles up on the land where the glacier had been, a broad, smooth stretch called an "outwash plain" (or "sandur"). The kettle hole occurs when the exposed or buried ice block melts so that the surface of the sandur sinks. Multiple kettle holes can form near each other, and with the ridges and mounds of sediment around them the smooth surface of the sandur becomes irregular. Kettle holes can also occur in ridge-shaped deposits of loose rock chunks called "till."