only, that contribute to the shape of lakes. Grosse et al. (2013) summarize endogenous and exogenous elements that are key factors in orientation including: Redistribution of littoral shelves by wind creating insulation, arrangement of polygonal ice-wedges producing thawing, and erosion from fluvial channels causing inhomogeneous sediments. Drainage Before complete drainage, lake edges recede through retrogressive thaw slumps (RTS) and subaerial debris flows. Actual drainage may be triggered by fluvial erosion or expansion of adjacent basins at inland locations. In coastal areas, drainage may be due to coastal retreat leading to thermal abrasion or erosion due to wave action. More gradual drainage (partial or complete) may be caused by local permafrost degradation and erosion. Lakes stop growing once drainage initiated, and eventually depressions are filled by sediments, aquatic plants or peat. Another option for the fate of a drained thaw lake is that the active layer surrounding the lake deepens to below water level once ground ice is exhausted, allowing for a residual lake to remain. Gallery See more photos at Wikimedia Commons - Thermokarst. See also Retrogressive thaw slumps References External links Periglacial landforms Patterned grounds Permafrost