Experiments on the formation of wind-faceted pebbles

Ventifacts at the Pathfinder landing site

“…The link between their morphology and formation mechanism has been well documented in both field and laboratory studies [Blake, 1855;Kuenen, 1928;Schoewe, 1932;Sharp, 1949Sharp, , 1964Sharp, , 1980 that can act as wind shields. All of these requirements restrict ventifact formation to arid regimes.…”

Recent ventifact development on the central Oregon coast, western USA

“…Reasons for this may include the poorly defined and qualitative visual basis on which ventifacts are identified (Miotke, 1982), the range of possible time-scales (hours to millennia) on which ventifaction can take place (Kuenen, 1960;Miotke, 1982), and the relict nature of some ventifacts with respect to present-day winds (Schlyter, 1995). Ventifaction is also dependent on a range of environmental variables including wind approach angle and its constancy over time, sediment grain size and concentration in the windstream, and rock surface hardness (Schoewe, 1932;Lancaster, 1984;Greeley and Iversen, 1985), characteristics which are difficult to evaluate in the field. Accurately ageing ventifacts in the field is also necessary in order to quantify wind abrasion rates.…”

Wind Erosion in Drylands

“…Groove trends are typically parallel on near-horizontal surfaces and reflect the flow direction of the highest velocity winds (Laity, 1987). Maxson (1940) suggested that grooves and flutes are initiated by vortices and then modified by saltating sand grains, whereas Schoewe (1932) proposed that the skidding action of grains on hard, smooth surfaces might be important. Whitney (1978) put forward the idea that vortex pits coalesce into flute pits and pit chains, but pit chains have not been observed in the field.…”

“…To date, however, little work has been done in this area. The experimental work of Schoewe (1932) demonstrated that the rate of abrasion and angle of the abraded surface decrease over time. Work by Bridges et al (2010) on rock simulant targets abraded by sand in a boundary layer wind tunnel indicates that the surface of a rock is initially roughened, with the surface area-to-volume ratio increasing at a rate greater than log (2/3).…”