Geomorphology and origin of Yardangs in the Kumtagh Desert, Northwest China

Dong, Zhibao; Lv, Ping; Lu, Junfeng; Qian, Guangqiang; Zhang, Zhengcai; Luo, Wenhao

doi:10.1016/j.geomorph.2011.10.012

Cited by 60 publications

(65 citation statements)

References 23 publications

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“…Water‐driven erosional processes act as an important limiter of yardang height in OWSVRA. Our conclusion that water‐driven erosional processes are essential in yardang evolution at OWSVRA is consistent with the conclusions of prior studies (e.g., Brookes, , ; Dong et al, ). This result suggests that yardangs can be expected to be steeper, all else being equal, in more arid regions where water‐driven erosional processes are less efficient and hence where yardang height may only be limited by mass wasting.…”

Section: Discussionsupporting

confidence: 92%

“…Similar minimum‐drag concepts have been applied to subaqueous streamlined bedforms (e.g., Komar, , ). Yardang aspect ratios on Earth (de Silva et al, ; Dong et al, ; Hu et al, ) and Mars (Mandt et al, ) vary by 2 orders of magnitude (i.e., 2–200), however, suggesting that the minimum‐drag model of Ward and Greeley () requires further assessment. Evidence suggests that yardang aspect ratios may, in some cases, be controlled primarily by characteristics (e.g., the strikes, dips, and stratal thicknesses) of the substrate.…”

Section: Introductionmentioning

confidence: 99%

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Controls on Yardang Development and Morphology: 1. Field Observations and Measurements at Ocotillo Wells, California

et al. 2018

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Yardangs are streamlined hills formed in part by the erosive action of wind and wind‐blown sediments. Here we examine the controls on yardang development and morphology using the Ocotillo Wells State Vehicular Recreation Area (OWSVRA), California, as a study site. We measured the compressive strengths, strikes, and dips of bedrock strata, eolian sediment fluxes (including their vertical profiles and spatial variations around yardangs), and erosion rates derived from geologic constraints and multitemporal Terrestrial Laser Scanning (TLS). We used a combination of TLS‐based and airborne lidar‐based Digital Elevation Models (DEMs) to test the applicability of an asymmetric Gaussian function for characterizing yardang form and quantify the relationships among yardang lengths, widths, heights, spacings, and their controlling factors. Yardang aspect ratios are controlled by bedrock structural attributes, specifically by the tangent of the dip and the angle between the strike and the prevailing wind direction. Yardang spacings scale linearly with yardang width. Yardang heights increase as the square root of width such that larger yardangs tend to have gentler side slopes. Sediment fluxes reach a maximum in the troughs among yardangs, consistent with the hypothesis that yardang development involves the focusing of wind and wind‐blown sediments into troughs. The vertical distribution of eolian sediment flux follows a power law with an exponent of −2.5, a result consistent with an advection‐diffusion‐settling model of transport near the saltation‐suspension transition. Erosion rates are several mm/yr over time scales of ~100 and ~106 years.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Controls on Yardang Development and Morphology: 1. Field Observations and Measurements at Ocotillo Wells, California

et al. 2018

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“…The analyses of this paper and the companion paper demonstrate the important role played by water‐driven processes, including freeze‐thaw‐driven creep, rain splash, and interrill and rill erosion. This conclusion is not novel (e.g., Brookes, , ; Dong et al, ). However, the numerical model demonstrates quantitatively how the efficiency of water‐driven erosional processes controls yardang morphology, that is, the value of the topographic diffusivity, D topo , features prominently in many of the key equations of this paper.…”

Section: Discussionmentioning

confidence: 80%

Controls on Yardang Development and Morphology: 2. Numerical Modeling

Pelletier

2018

JGR Earth Surface

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Here I present a set of mathematical modeling results, constrained by the results of the companion paper, aimed at improving our understanding of yardang development and controls on yardang morphology. The classic model for yardang development posits that yardangs evolve to an aspect ratio of ≈4 in order to minimize aerodynamic drag. Computational fluid dynamics model results presented here, however, demonstrate that yardangs with an aspect ratio of 4 do not minimize drag. As an alternative, I propose that yardang aspect ratios are primarily controlled by the lateral downwind expansion of wind and wind‐blown sediments focused into the troughs among yardangs, which can be quantified using previous studies of wall‐bounded turbulent jets. This approach predicts yardangs with aspect ratios in the range of 5 to 10, that is, similar to those of natural yardangs. In addition to aerodynamics, yardang aspect ratios are influenced by the strikes and dips of strata, as demonstrated in the companion paper. To better understand the aerodynamic and bedrock structural controls on yardang morphology, I developed a landscape evolution model that combines the physics of boundary layer flow and abrasion by eolian sediment transport with a model for the erosion of the tops and lee sides of yardangs by water‐driven erosional processes. Yardang formation in the model is enhanced in substrates with greater heterogeneity (i.e., alternating strong and weak strata). Yardang morphology is controlled by the strikes and dips of strata as well as the topographic diffusivity associated with water‐driven erosional processes.

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“…Dong et al (2011Dong et al ( , 2012 have described the physiographic settings and geomorphologic features of this desert region in detail. The oblique zibars are mainly distributed at the northeastern margin of the desert, and linear dunes with heights of about 10 m have formed in the northwest of this zone (Fig.…”

Section: Study Area and Methodsmentioning

confidence: 99%