Sastrugi Sastrugi Sastrugi, or zastrugi, are sharp irregular grooves or ridges formed on a snow surface by wind erosion, saltation of snow particles, and deposition, and found in polar and open sites such as frozen lakes in cold temperate regions. The ridges are usually perpendicular to the prevailing winds; they are steep on the windward side and sloping to the leeward side. Smaller irregularities of 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
Surface wave detection by animals (short bursts of amplitude less than 100μm which contain many frequencies between 5 Hz and 190 Hz and are of short duration, as when an insect just touches the water rather than moves continuously at the surface). The other is continuous wave stimuli, which will contain many frequencies and in the wild are generated by fallen prey struggling at the water surface. It has been pointed out that "A lineatus" and other surface feeding fish are able to locate prey even if the waveform is only in click form (just touching the surface once, as when surfacing for air or