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a pileup of fragments of ice floes on the ice cover of seas, rivers, and lakes. Hummocks are caused by the lateral pressure of ice fields on one another and on the shoreline and shoals, which results in fragmentation of the edges of the fields. Hummocks are most common in the East Siberian and Chukchi seas and in the open part of the Arctic Ocean, where their height sometimes exceeds 8–9 m (in coastal areas it may reach 15–20 m).
Among the forms of hummock development that are distinguished are ridges (in solid drifting ice), barriers (hummock ridges on the margin of the shore ice, occasionally resting on the bottom), standing floes (ropaks), and stamukhi (individual pile-ups on shoals). The degree of development of hummocks is measured on a five-point scale; 0 indicates a completely smooth ice sheet, and 5 means that the ice sheet is completely covered with hummocks.