Sastrugi, or zastrugi are sharp irregular grooves or ridges formed on a snow surface by wind erosion and deposition, and found in polar and temperate snow regions. They differ from sand dunes in that the ridges are markedly parallel to the prevailing winds.
Sastrugi are various surface irregularities resulting from wind erosion, saltation of snow particles and deposition. Smaller irregularities or this type are known as ripples (small, ~10 mm high), or wind ridges.
Larger features are especially troublesome to skiers and snowboarders. Traveling on the irregular surface of sastrugi can be very tiring, and can risk breaking equipment—ripples and waves are often undercut, the surface is hard and unforgiving with constant minor topographic changes between ridge and trough.