Morphologic characteristics and development of falling dunes, northeast Kuwait

Climbing and falling dunes in Valles Marineris, Mars

“…This morphology suggests slip face advancement occurs at a greater rate towards the center of the dune as compared to the flanks, presumably due to a higher velocity and/or more consistent airflow over the center of the dune. Three-dimensional models of airflow down terrestrial wadis support this notion, with higher wind velocity vectors near the center of the wadis and decreased wind flow on the flanks [Al-Enezi et al, 2008], potentially due to airflow separation of the walls.…”

“…[7] Falling dunes, found on the downwind side of large topographic highs, are formed by unidirectional down slope winds and gravity in two main environments ( Figure S1). One example of falling dunes is found in Kuwait, where size and morphology are largely influenced by the size, slope and orientation (with respect to the prevailing wind direction) of their host wadis, or desert valleys [Al-Enezi et al, 2008]. The slip face of these dunes may be parallel to wadi walls (resembling a linear dune morphology), arcuate, perpendicular to them (and crescent shaped), or absent altogether [Al-Enezi et al, 2008].…”

“…One example of falling dunes is found in Kuwait, where size and morphology are largely influenced by the size, slope and orientation (with respect to the prevailing wind direction) of their host wadis, or desert valleys [Al-Enezi et al, 2008]. The slip face of these dunes may be parallel to wadi walls (resembling a linear dune morphology), arcuate, perpendicular to them (and crescent shaped), or absent altogether [Al-Enezi et al, 2008]. Bed forms encountering mountainous areas with greater relief than wadis may form the falling dune class [Liu et al, 1999].…”

“…The underlying topographic slopes for climbing dunes are generally shallower (∼10°) than the slopes under falling dunes (∼25°) [Evans, 1962;Tsoar, 1983;Liu et al, 1999]. Falling dunes preferentially are transported down gullies (or wadis) as the path of least resistance, whereas climbing dunes may encounter and ascend either gullies or spurs [Koscielniak, 1973;Al-Enezi et al, 2008]. In addition, falling dunes may act as feeders for other dune forms within the trough or valley, whereas climbing dunes may allow sediment to escape from a topographic low [Bourke et al, 2004].…”

Volcaniclastic aeolian deposits at Sunset Crater, Arizona: terrestrial analogs for Martian dune forms

“…Dunes that approach a cliff or scarp from the upslope side may cascade over the steep topography and accumulate at the base as falling dunes (Greeley and Iversen, ). They range in size from a meter or two to hundreds of meters in height and width (Al‐Enezi et al , ). To the northeast and east of Sunset Crater, falling dunes occur in the lee of Woodhouse Mesa, in Deadman Wash near Doney Mountain, and along other escarpments (Figure ).…”