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 for the first, a loudspeaker is set up facing the water surface, while a plastic disc covers the front of the speaker cone with a small hole in the center, allowing air to be pushed through the hole to stimulate the water surface in a pattern controlled by a square-wave generator. Alternatively, a small rod a few millimeters in diameter is dipped briefly a few centimeters into the water. Either setup can be moved around the tank to deliver stimuli at various locations. The loudspeaker setup offers the advantage that stimuli can be precisely controlled to mimic natural stimuli or