TY - JOUR
T1 - Controls on Yardang Development and Morphology
T2 - 1. Field Observations and Measurements at Ocotillo Wells, California
AU - Pelletier, Jon D.
AU - Kapp, Paul A.
AU - Abell, Jordan
AU - Field, Jason P.
AU - Williams, Zachary C.
AU - Dorsey, Rebecca J.
N1 - Funding Information: I wish to thank Giovanni Coco, Tom Barchyn, Doug Sherman, and an anon ymous reviewer for comments that sig nificantly improved the manuscript. This study was supported by NSF award EAR-1323148. We thank the staff of Ocotillo Wells SVRA for permission to conduct field work in the park and for logistical support. We thank Michael Holt for assistance fabricating the MWAC towers. We thank Mike Himmerich of Borrego Springs, California, for maintaining CWOP station DW1021 and for helping us locate a long-term archive of the wind data from his station. Publisher Copyright: ©2018. American Geophysical Union. All Rights Reserved.
PY - 2018/4
Y1 - 2018/4
N2 - 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.
AB - 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.
KW - abrasion
KW - eolian
KW - yardangs
UR - http://www.scopus.com/inward/record.url?scp=85045881146&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85045881146&partnerID=8YFLogxK
U2 - 10.1002/2017JF004461
DO - 10.1002/2017JF004461
M3 - Article
SN - 2169-9003
VL - 123
SP - 694
EP - 722
JO - Journal of Geophysical Research: Earth Surface
JF - Journal of Geophysical Research: Earth Surface
IS - 4
ER -