Sastrugi breaking equipment—ripples and waves are often undercut and the surface is hard and unforgiving, with constant minor topographic changes between ridge and trough. The words "sastrugi" and "zastrugi" are Russian-language plurals; the singular is "sastruga" or "zastruga". The form "sastruga" started as the German-language transliteration of the Russian word заструга (plural: заструги). A Latin-type analogica singular "sastrugus" is used in various writings on exploration of the South Pole, including Robert Falcon Scott's expedition's diaries and Ernest Shackleton's "The Heart of the Antarctic". Under the action of steady wind, free snow particles accumulate and drift like the sand grains in barchan
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