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 sensitive range of 75–100 Hz. Fish are also sensitive to waves generated within 7–30 cm of the fish’s location, though they can occur at any point within that radius. Because the water surface acts as a low pass filter, this radius is different for different wave frequencies: 70 Hz waves with 100μm peak-to-peak distance are subthreshold at 37 cm, and 140 Hz waves are subthreshold at 19 cm. Fish are able to tell apart concurrent waves of different frequencies when the frequencies are different by at least 15%, though at certain frequencies this difference can be as low as 8%.