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Fast ice (also called ''land-fast ice'', ''landfast ice'', and ''shore-fast ice'') is sea ice that is 'fastened' to the coastline, to the sea floor along shoals or to grounded icebergs.〔Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag.〕 Fast ice may either grow in place from the sea water or by freezing pieces of drifting ice to the shore or other anchor sites.〔〔Kovacs, A.and M. Mellor. 1974. "Sea ice morphology and ice as a geologic agent in the Southern Beaufort Sea." pp. 113-164, in: ''The Coast and Shelf of the Beaufort Sea'', J.C. Reed and J.E. Sater (Eds.), Arlington, Va.: U.S.A.〕 Unlike drift (or pack) ice, fast ice does not move with currents and winds. The width (and the presence) of this ice zone is usually seasonal and depends on ice thickness, topography of the sea floor and islands.〔 It ranges from a few meters to several hundred kilometers.〔 Seaward expansion is a function of a number of factors, notably water depth, shoreline protection, time of year and pressure from the pack ice.〔 The topography of the fast ice varies from smooth and level to rugged (when submitted to large pressures). The ''ice foot'' refers to ice that has formed at the shoreline, through multiple freezing of water between ebb tides, and is separated by the remainder of the fast ice surface by ''tidal cracks''. Further away from the coastline, the ice may become anchored to the sea bottom — it is then referred to as ''bottomfast ice''.〔 Fast ice can survive one or more melting seasons (''i.e.'' summer), in which case it can be designated following the usual age-based categories: first-year, second-year, multiyear. The ''fast ice boundary'' is the limit between fast ice and drift (or pack) ice — in places, this boundary may coincide with a shear ridge.〔〔 Fast ice may be delimited or enclose pressure ridges which extend sufficiently downward so as to be grounded — these features are known as stamukhi. ==See also== *Anchor ice, also called ''bottom-fast ice'' *Ice bridge *Sea ice *Stamukha 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「fast ice」の詳細全文を読む スポンサード リンク
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