Wind Erosion in Drylands

Laity, Julie E.

doi:10.1002/9780470710777.ch21

Cited by 17 publications

(22 citation statements)

References 102 publications

(242 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Grolier et al () found that wind‐streamlined yardang appears to have an aspect ratio value (length/width) of 3:1 or greater, which has been suggested to be a critical parameter to distinguish yardangs from other hills. In fact, their aspect ratios are associated with the duration for erosion, the strength of wind, and the competence of rock into which they are carved (Laity, ). On the basis of fluid mechanics and aerodynamical theoretical calculations, Fox and McDonald () found that the long‐ridge yardangs with large aspect ratio values are formed by strong skin‐friction drags, whereas yardangs with small aspect ratio values are formed by pressure drags.…”

Section: Yardangs In the Qaidam Basinmentioning

confidence: 99%

“…The orientation of yardangs is usually controlled by the local dynamical conditions. The long axes of yardangs sculpted by wind are largely subparallel to the direction of the prevailing wind, or the maximum wind velocity, whereas the orientation of yardangs formed or modified by ephemeral water may be consistent with the flow direction of the water (Hörner, ; Krinsley, ; Laity, ; Xia, ). If the yardangs were eroded by both processes, wind and water, then their orientations might exhibit an angle between them (Xia, ).…”

Section: Yardangs In the Qaidam Basinmentioning

confidence: 99%

“…Yardang is a geological term that was introduced by Hedin () when he traveled the Lop Nur, northwestern China, to define the streamlined, wind‐carved ridges that had been developed within lacustrine deposits. This term has now been extended to define wind‐carved ridge‐like features in general, whether highly streamlined or not (Halimov & Fezer, ; Laity, ). Typical yardangs occur mostly in large fields, and they are observed in arid to hyperarid regions that have sparse vegetation and annual precipitation less than 50 mm (Niu et al, ).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Geological Features and Evolution of Yardangs in the Qaidam Basin, Tibetan Plateau (NW China): A Terrestrial Analogue for Mars

et al. 2018

View full text Add to dashboard Cite

Wind‐eroded ridges known as yardangs are common in most arid desert regions on Earth, as well as on other planets, notably in the Medusae Fossae Formation (MFF) and Gale Crater on Mars. However, the formation and evolution of these various yardangs are not well understood, which, therefore, requires further studies by more terrestrial analogues. Here we report a detailed investigation of the terrestrial yardang fields in the Qaidam Basin, northeastern Tibetan Plateau, China. Most of them are distributed in the northwestern and central eastern parts, with dominant orientations northwest to north‐northeast and approximately west to east, respectively. Based on their morphologies and distributions, yardangs within the Qaidam Basin have been classified into 11 different types out of four main groups. Wind is the dominant driver of yardang erosion, but water, salt, and mass wasting may also have played important roles in their formation and modification. A four‐step evolution model, including embryonic, adolescent, mature, and receding stages, is proposed to reveal their formation and evolution in the basin. Meanwhile, yardangs in the MFF and Gale Crater on Mars have morphologic and geometric characteristics that show striking similarities to those in the Qaidam Basin. The fact that some yardang fields in MFF on Mars also show overlapping relationships suggests that they possibly have experienced a multistage evolution, during which the evolution processes may have been interrupted at some stages due to differences in the competence of rocks and/or the changes of the environment.

show abstract

Section: Yardangs In the Qaidam Basinmentioning

confidence: 99%

Section: Yardangs In the Qaidam Basinmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Geological Features and Evolution of Yardangs in the Qaidam Basin, Tibetan Plateau (NW China): A Terrestrial Analogue for Mars

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Laity () proposed that yardangs develop “when air enters a passageway established by a channel or fracture,” suggesting that the characteristic spacing of joints or first‐order fluvial channels are also a candidate length scales for the control of yardang morphology. However, many geomorphic studies of the past few decades have demonstrated that when an instability mechanism is at work, a macroscopic preexisting weakness such as a channel or fracture may not be necessary to initiate the feedback.…”

Section: Introductionmentioning

confidence: 99%

Controls on Yardang Development and Morphology: 2. Numerical Modeling

Pelletier

2018

JGR Earth Surface

View full text Add to dashboard Cite

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.

show abstract

“…), and rock lithology and size. Ventifacts develop with key characteristics that may include: 1) facets, which often abut at sharp keels; 2) polish; 3) differential erosion (etching, fretting or 'knobby' texture) caused by inherent inhomogeneities in the rock, such as inclusions or layering; or 4) features with essentially universal shapes (pits, grooves, flutes, scallops and, rarely, helical forms, see Sharp, 1949;Laity, 2009Laity, , 2011, only moderately influenced by specific material properties, such as rock lithology, hardness or vesicularity. This paper focuses on the development of ventifact features, motivated by our lack of understanding of the emergence and growth of these regular patterns.…”

Section: Introductionmentioning

confidence: 99%