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a relief-forming process that occurs through the action of snow, primarily in polar, subpolar, and high-mountain regions. Necessary conditions for nivation are a fluctuation of the air temperature around the freezing point of water and the inflow of water from thawing névés. Under these conditions, rocks are broken down and small particles are carried away by the water. Larger fragments are removed from beneath névés together with water-saturated mud. This results in the formation under the névé of a hollow that often becomes a cirque. Nivation is most clearly manifested in areas where large amounts of snow accumulate, since the snow, during the warm season of the year, does not entirely melt away and remains in the form of névés.