A kettle is a depression or hole in an outwash plain formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of dead ice left behind by retreating glaciers, which become surrounded by sediment deposited by meltwater streams as there is increased friction. The ice becomes buried in the sediment and when the ice melts, a depression is left called a kettle hole, creating a dimpled appearance on the outwash plain. Lakes often fill these kettles; these are called kettle hole lakes. Another source is the sudden drainage of an ice-dammed lake and when the block melts, the hole it leaves behind is a kettle. As the ice melts, ramparts can form around the edge of the kettle hole. The lakes that fill these holes are seldom more than 10 m (33 ft) deep and eventually fill with sediment. In acid conditions, a kettle bog may form but in alkaline conditions, it will be kettle peatland.
Satellite image of kettle lakes in Yamal Peninsula (Northern Siberia), adjacent to the Gulf of Ob (right). The lake colors indicate amounts of sediment or depth.
A kettle in the Isunngua highland, central-western Greenland
A kettle pond in the Hossa hiking area, Suomussalmi, Finland
Numerous kettle lakes border the Denali Highway in Alaska
A glacier is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.
Glacier of the Geikie Plateau in Greenland.
The Taschachferner in the Ötztal Alps in Austria. The mountain to the left is the Wildspitze (3.768 m), second highest in Austria.
With 7,253 known glaciers, Pakistan contains more glacial ice than any other country on earth outside the polar regions. At 62 kilometres (39 mi) in length, the pictured Baltoro Glacier is one of the world's longest alpine glaciers.
The Quelccaya Ice Cap in Peru is the second-largest glaciated area in the tropics