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 then back towards the other. Each neuromast has a preferred direction. This was shown in 1970 through ablation of all but one neuromast: fish then usually turned towards one range of directions regardless of where the stimulus came from. The direction sensitivity, as revealed via electrophysiology, shows a cosine function describing receptor firing intensity: accuracy depends on receptor orientation and arrangement and intensity-difference threshold. In 2011 it was shown that there are certain fleshy ridges around each neuromast that direct water flow. When these ridges were removed, the receptive field for each neuromast was much wider than that with intact