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 fish are still able to judge the distance of a wave’s source with only a single functioning neuromast when all others have been ablated. When presented with single-frequency or upward frequency-modulated waves, fish underestimate the distance of the wave source; this suggests the normal downward FM of capillary waves, which arises almost immediately in wave dispersion, is necessary for "A lineatus" to judge distance. This was confirmed in 1982 by presenting fish with waves with an artificially generated waveform so that at 7 cm the wave had the downward FM sweep of a wave 15 cm away, and fish responded