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ABSTRACT Wind‐driven sediment transport drives significant landscape evolution in arid regions. Wind‐blown sand can form large dunes, or can erode exposed surfaces via abrasion. Previous works on aeolian abrasion have focused on the geomorphological features resulting from abrasion (for example, ventifacts and yardangs) through both field and wind‐tunnel experiments. However, relatively little attention has been given to how abrasion varies spatially as sand flux converges on a sand sink, such as a dune field. This work studied an arid landscape using field measurements and collected weather data to quantitatively measure how abrasion varies in space around the Ibex Dune Field. From March 2021 to October 2022, the wind conditions at two separate locations in the region were monitored, saltating sand flux was captured using fully rotating sediment traps, ventifacts were mapped along several transects, and abrasion‐related mass loss on mounted gypsum plaster samples was measured. These results suggest that the magnitude of abrasion is approximately inversely proportional to the distance away from the dune field, increasing in magnitude as sands converge and fluxes increase at the dune field sink. Comparison between modern winds and ventifact orientations suggests that additional complexity, not aeolian processes alone, may be shaping the morphology of surface cobbles. [ABSTRACT FROM AUTHOR]

Within the Greater Rocky Mountain Region, ventifacts have not been extensively studied, and little is known about various local relationships between rock type, wind regime, and associated ventifaction styles. The Killpecker Sand Dunes area of southwest Wyoming hosts several significant ventifact sites—including the site of this study, which focuses on Cretaceous Almond Formation outcrops along the south margin of the dune field. The ventifacts appear to be the product (at least in part) of Holocene winds, based on the freshness of ventifacted surfaces and their alignments with local wind directions. The ventifaction occurs on both fragments and in-situ bedrock sandstones exposed within and marginal to the dune field. This study, begun in 2020, demonstrates how ventifaction can be used to recognize local wind regimes within broader areas of atmospheric circulation. Analysis of regional wind regimes as they affect sand movement, and thus the formation of ventifacts, indicates a dominant release of wind energy from the southwest. Yet the most intense ventifaction in the study area at Killpecker dunes has been produced by northeast winds. It seems likely that topographic controls on winds in the study area, as well as local sand supply variations, have resulted in this strong ventifaction by northeast winds. This supports the idea that ventifacts may sometimes be a useful guide to understanding the history of a local wind regime, especially where there is no meteorological station. Ventifacts at the Killpecker dunes commonly have clusters of features that differ with increasing angles of sand impact. The angle of sand impact is the sum of the angle of descent of saltating sand (average 14 degrees) and the dip of the rock surface into the flow. Flat- to shallow-dipping (0 to 15 degrees) surfaces typically tend to polish, with a dominance of flute and scallop ventifaction features. In addition, terraces and scour pits around concretions on rock surfaces are common at this angle of exposure. Rock surfaces with moderate dip angles (16 to 30 degrees) into the sand flow direction tend to have an abundance of grooves. Where the rock surface dips at a steep angle (31 to 90 degrees), fretting is the dominant ventifaction feature. In the study area there are two ventifacted rock types. Type A ventifacted rocks are brownish (Munsell 10YR 5/4) laminated, commonly cross-bedded, mostly fine- to medium-grained sandstones of the Almond Formation. The interpreted depositional environment is a mixture of nonmarine, deltaic, and shallow marine sediments. Type B ventifacted rocks are commonly massive, gray, (Munsell 7.5YR 6/1) fine-grained, and highly calcareous. There are common shelly (molluscan) sandstones and thin limestones with occasional cross-bedding reflecting a more marine shoreline setting of this portion of the Almond Formation. Ventifacted surfaces are better polished on Type B sandstones than the Type A sandstones, and ventifaction features are more sharply delineated. Exposed shell fragments deflect or modify the shapes of flutes and grooves. Many large and small rocks, particularly flat-bedded sandstones, have broken in place—possibly due to the accumulated effects of the sharp diurnal temperature fluctuations at Killpecker—followed by ventifaction of daughter fragments. [ABSTRACT FROM AUTHOR]

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Ventifacts are rocks that have been shaped through abrasion by wind‐transported sediment. Their surfaces may be ornamented with characteristic microscale features that are replicated and overlain to form complex patterns. Compared to a large body of work on the transport of unconsolidated sediment in which the atmospheric boundary‐layer flow and sand cloud respond to perturbations in the developing topography, no experimental work to this date has addressed morphodynamic feedback at the particle scale in aeolian systems dominated by abrasion. This article reports on a case study in which laser Doppler anemometry was used in wind tunnel experiments to measure air flow and sand transport over a highly ornamented, tabular ventifact from the Taylor Valley, Antarctica. Periodicity characterizing the static microtopography of the ventifact was observed to be strongly imprinted on the kinetics of both the airflow and particle cloud when sampled along a transect of the ventifact aligned with flow in the wind tunnel matching the dominant sand transporting wind direction for the ventifact in situ. The vertical velocity component was especially well synchronized, with changes in elevation on the order of 2–4 mm. The horizontal component of particle velocity demonstrated an offset in the downwind direction associated with the large forward momentum of the saltating sand particles. However, submillimeter relief on the fixed ventifact surface was not sufficient to initiate kinetic feedback, as observed along a transect aligned normal to a series of elongated flute structures and the dominant sand transporting wind direction. The particle‐scale experimental results confirm that (i) abrasion of this ventifact principally occurred under a unimodal wind and sand transport regime of low‐moderate intensity, and (ii) relief arising from weathering, as governed by the ventifact's lithology, likely initiated development of the present‐day ornamentation. [ABSTRACT FROM AUTHOR]

In this study, we have investigated rock weathering phenomena in the central part of Dronning Maud Land, Antarctica. The area is characterized by low mean annual temperatures (−18 °C), strong katabatic winds, and minimal liquid water at the surface. Weathering features, including ventifacts, tafoni, and grus accumulations, are characterized through field observations, rock surface temperature measurements, and microscopic analysis. Abrasion by sand and ice particles transported by strong winds has locally resulted in ridge-shaped ventifacts and rock surfaces with elongated pits, furrows, and grooves. The abrasion-caused features, such as polished facets, keels, and grooves, indicate a northeast-facing wind direction, aligning with the present-day wind regime. The dominant weathering processes in coarse-grained intrusive rocks are oxidation and granular disintegration. Fe-oxidation induces cracking, increasing the porosity and enhancing susceptibility to further weathering. Additionally, temperature fluctuations on rock surfaces caused by solar radiation create thermal stress, which can lead to the formation of microcracks. These microcracks, formed due to thermal expansion, are likely to propagate through subcritical cracking, which is a slow, long-term process. Together, Fe-oxidation, thermal expansion, and subcritical cracking are important mechanisms contributing to long-term weathering and rock decay. Salt weathering, facilitated by snow and ice meltwater, particularly within tafoni, leads to flaking and disintegration of the parent rock. These findings shed light on the complex interactions shaping the geomorphology of central Dronning Maud Land and provide insights into long-term weathering processes operating in Antarctica's extreme environment. • New insights on rock weathering in a remote Antarctic location • Weathering and landscape evolution are greatly influenced by lithological properties. • Coarse grain size and Fe-oxidation control cracking and granular disintegration. • High daily temperature changes lead to thermal stress and subcritical cracking. [ABSTRACT FROM AUTHOR]

Soil erodibility is an essential parameter used in soil erosion prediction. This study selected the Liangshan town watershed to quantify variation in the vertical zonality of rill erodibility (kr) in China's ecologically fragile Hengduan Mountains. Soil types comprised of yellow–brown (soil A), purple (soil B), and dry‐red (soil C) in a descending order of occurrence from the summit to the valley, which roughly corresponds to the vertical climate zone (i.e. cool‐high mountain, warm‐low mountain, and dry‐hot valley sections) of the study area. With elevation, vertical soil zonality varied in both soil organic matter (SOM) content and soil particle‐size fractions. A series of rill erosion‐based scour experiments were conducted, using water discharge rates of 100, 200, 300, 400, 500, and 600 mL min‐1. Additionally, detachment rates (Dr) were measured under three hydrological conditions (the drainage, saturation, and seepage treatments). Results show that both Dr and flow shear stress (Ʈ) values increased as discharge increased. As elevation increased, the kr values decreased, while the vertical zonality of critical shear stress (Ʈc) values showed no obvious variation. The highest kr values were observed during the seepage treatment, followed by the saturation treatment then drainage treatment, indicating that variation in vertical hydraulic gradients could significantly alter kr values. This study also found that land‐use types could also alter kr and Ʈc values. Further research, however, is necessary to better quantify the effects of subsurface hydrological conditions and land‐use types on kr under different soil zonalities in China's Hengduan Mountains. © 2018 John Wiley & Sons, Ltd. This study selected the Liangshan town watershed to quantify variation in the vertical zonality of rill erodibility (kr) in China's ecologically fragile Hengduan Mountains. As elevation increased, the kr values decreased. The highest kr values were observed during the seepage treatment, followed by the saturation treatment then drainage treatment, indicating that variation in vertical hydraulic gradients could significantly alter kr values. This study also found that land‐use types could also alter kr and Ʈc values. [ABSTRACT FROM AUTHOR]

Flow velocity is fundamental in calculating related parameters of physical soil erosion models. It has been well known that rill flow velocity varies with developing rill form, which complicates and impedes the development of soil erosion models. In filed, rainfall erosion frequently occurs with pre-existing rills not damaged by tillage practices. However, the rill flow velocity in this case has received little attention. In this study, we investigated rill flow velocity regimes for both developing and stationary rills using 5 m-length plots in the laboratory. The experiments included two consecutive rainfalls, which had similar runoff rate. The first rainfall had an intensity of 90 mm h −1 , which generated well-developed rills; the second had an intensity of 60 mm h −1 and did not damage the rills formed by the first rainfall. The results show that, for a developing rill, rill flow velocity is higher in the lower slope than that in the upper slope, and rill flow velocity in the lower slope fluctuates much more over time as a result of the variation of rill morphology following rill development. With rill development, the rill flow velocity of the lower slope decreased responding to the stabilizing rill channel and exhibited a similar trend to that in upper slope. For a stationary rill, the rill flow velocities at both sections varied little over time, demonstrating that rill flow velocity is primarily influenced by rill morphology. Hence, the results suggested that the strength of fluctuation in rill flow velocity could be used to characterize the instantaneous intensity of soil erosion and active level of rill development. The channel of the stationary rill simply acted as transport pathways of sediment supplied by inter-rill erosion. The physical models of soil erosion should take into account the micro-topography on land surface related to the antecedently formed rills. [ABSTRACT FROM AUTHOR]

After wildfire a hitherto unexplained erosion process that some authors have called ‘miniature debris flows on hillslopes’ and that leave behind levee-lined rills has been observed in some regions of the world. Despite the unusual proposition of debris flow on planar hillslopes, the process has not received much attention. The objectives of this study were to (1) accumulate observational evidence of Hillslope Debris Flows (HDF) as we have defined the process, to (2) understand their initiation process by conducting runoff experiments on hillslopes, to (3) propose a conceptual model of HDF, and to (4) contrast and classify HDF relative to other erosion and transport processes in the post-wildfire hillslope domain. HDF have been observed at relatively steep slope gradients (0.4–0.8), on a variety of geologies, and after fire of at least moderate severity and consist of a lobe of gravel- to cobble-sized material 0.2–1 m wide that is pushed by runoff damming up behind it. During initiation, runoff moved individual particles that accumulated a small distance downslope until the accumulation of grains failed and formed the granular lobe of the HDF. HDF are a threshold process, and runoff rates of 0.5 L s − 1 2 L s − 1 were required for their initiation during the experiments. The conceptual model highlights HDF as a geomorphic process distinct from channel debris flows, because they occur on planar, unconfined hillslopes rather than confined channels. HDF can erode very coarse non-cohesive surface soil, which distinguishes them from rill erosion that have suspended and bedload transport. On a matrix of slope and grain size, HDF are enveloped between purely gravity-driven dry ravel, and mostly runoff driven bedload transport in rills. [ABSTRACT FROM AUTHOR]

We conducted a laboratory study on rill network evolution with detailed measurements under controlled experimental conditions. The concepts of fractal geometry, entropy and topology were used to quantify rill erosion intensity and morphology. The objectives of this study are to reveal rill erosion processes and rill network development under different rainfall intensities and to present some indicators to provide a quantitative description of rill morphology. A soil pan (5 m long, 1 m wide and 0.6 m deep with slope gradient of 20°) was subjected to three successive rainfall events under rainfall intensities of 66, 94 and 127 mm h − 1 . The results showed that rainfall intensity played a major role in rill erosion. The development of a rill network is most rapid under medium intensity rainfall; rainfall intensity that is too weak or too strong is not conducive to rill development. As rainfall duration increased under the same rainfall intensity, the values of soil loss, rill density, geomorphologic comentropy and nodes increased. Rill network development was slow at the early stage but became more rapid at a later stage. The results also indicated that the geomorphologic comentropy was the best basic morphological indicator of rill erosion, and the number of rill nodes was the best derived morphological indicator of rill morphology, which was followed in descending order by the fractal dimension, rill density and bifurcation ratio. [ABSTRACT FROM AUTHOR]

The Pleistocene environment of the New Jersey Pine Barrens has been interpreted as either cool and moist, with boreal forest, or cold and dry, with semi-desert conditions. The presence of ventifacts is often cited as perfunctory evidence for strong Pleistocene wind action and sparse vegetation. This study examines sites where ventifacts had been reported and identifies abundant pebble- to boulder-sized samples with a wide suite of erosional forms. Faceting occurred when the land was sparsely vegetated, allowing abundant wind-entrained abradants to etch gravel and rocks as a consequence of katabatic winds blowing off the nearby Laurentide Ice Sheet. Most ventifacts occur on upland surfaces and attest to geomorphic stability in this part of the region's otherwise low-relief landscape. Ventifacts were reworked and incorporated within deposits attributed to periglacial mass movement, particularly during climatic amelioration. Aeolian features such as pavement einkante, scallops and weathering pits can evolve only where sustained wind velocities are very high, sand sources are abundant and vegetation is absent. The Pine Barrens' ventifacts provide evidence of cold, dry and windy conditions and aid in the interpretation of landscape evolution. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The fragile landscape of the north European loess belt is prone to soil erosion due to soil properties and intense land use of the fertile region. Exact measurement of surface changes with high temporal and spatial resolution over large areas is necessary to quantify and understand rill and interrill erosion processes. High resolution aerial imagery, acquired by an unmanned aerial vehicle (UAV), is used to automatically generate precise digital surface models (DSMs) of high spatial resolution by applying structure-from-motion image processing tools. During an investigation period of ten months, a 600 m2 field plot is observed during four field campaigns. A stable reference system is established for multi-temporal comparison. The overall accuracy of the DSMs generated from UAV images is less than 1 cm, verified by comparison with terrestrial laser scanner (TLS) data. Furthermore, a method for automatic rill extraction and rill parameter calculation is developed, which enables objective rill description with cm-accuracy and -resolution. Soil surface roughness and rill development as well as volumetric quantifications are analysed for multi-temporal change detection. Surface changes during winter season are controlled by soil consolidation, crusting and sheet erosion. During rainy spring season sheet erosion and rill incision occur. Two thunderstorms in summer season cause dominant rill erosion. Erosion rills are more dominantly deepening than widening (from to 2 to 4 cm depth and from 17 to 23 cm width), resulting in average per rill erosion values of 0.03 and 0.07 m3 respectively. An orientation dependent lateral rill shift is revealed, implying rill widening in eastern direction due to dominant winds from the West. Volumetric quantifications indicate high erosion volumes, reaching up to 121 tha-1 during the summer events. Highest erosion volumes are due to rill erosion rather than interrill erosion. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Field descriptions of ventifacts sculpted in wind-abraded, Albian carbonate rock protrusions are presented in this study, as well as of the closely related, wind-influenced chemical weathering features that interfere or converge morphologically with them. Descriptions of two new ventifacts (“bows” and “pinnacles”) are presented. “Bows” compare to the hydrodynamic forward parts of ship hulls, whereas “pinnacles” are sub-circular rounded salients that form clusters in vertical rock faces turned to the wind. Additionally, “sidewall tafoni” are described in non-detrital rocks. The ventifacts are used to identify geomorphically effective winds and to deepen in the knowledge of wind-driven weathering and abrasion processes. These erosional forms (not reported so far in northern Spain) are currently active in sand-dominated beach environments under a humid, temperate climate. Inactive and reactivated forms variably erased by current coastal dynamics are also described. These share the orientation characteristics of the currently active ones, and are interpreted as reflecting unconstrained past wind conditions over decadal or longer timescales. In spite of their interest as paleoenvironmental indicators, the geomorphic associations described exhibit a low preservation potential in the area, and no fossil equivalents have been described so far in older (uplifted or submerged) Quaternary coastal platforms of northern Spain. [Copyright &y& Elsevier]

This study presents the comparison of experimental results with assumptions used in numerical models. The aim of the field experiments is to test the linear relationship between different hydraulic parameters and soil detachment. For example correlations between shear stress, unit length shear force, stream power, unit stream power and effective stream power and the detachment rate does not reveal a single parameter which consistently displays the best correlation. More importantly, the best fit does not only vary from one experiment to another, but even between distinct measurement points. Different processes in rill erosion are responsible for the changing correlations. However, not all these procedures are considered in soil erosion models. Hence, hydraulic parameters alone are not sufficient to predict detachment rates. They predict the fluvial incising in the rill's bottom, but the main sediment sources are not considered sufficiently in its equations. The results of this study show that there is still a lack of understanding of the physical processes underlying soil erosion. Exerted forces, soil stability and its expression, the abstraction of the detachment and transport processes in shallow flowing water remain still subject of unclear description and dependence. [ABSTRACT FROM AUTHOR]

Abstract: Ventifacts (wind-worn stones) are typical of terrestrial environments remained very long without any vegetation, under hot or cold climates. Therefore, within the sedimentary record, they can allow recognizing desert conditions, even where no aeolian dune deposits are preserved. There seems that, in the recent literature, pebbles and cobbles from various palaeoenvironments were mistaken for ventifacts. This may partly be explained by the scatter and relative scarcity of illustrations to which refer. The aim of this paper is to help recognizing ventifacts in the sedimentary record, based on a critical review of the diagnostic properties generally used, and on new studies permitting to suggest additional criteria. After an evaluation of the sedimentary contexts favourable to preserving ventifacts, the distinctive characters that could be seen on each one are treated in order of increasing alteration of the original appearance: surface features, medium-scale features (new types of pit especially), and general shape. Finally, the problem of distinguishing between ventifacts and aquafacts is approached. [Copyright &y& Elsevier]

Abstract: Surface textural features – pits, grooves, flutes, and scallops – of sand-blasted ventifacts have been attributed to various erosional mechanisms and to variations in material hardness. This study develops a numerical model of abrasion to examine feature formation by direct grain impacts. We demonstrate that abrasion by a continuous supply of impactors arriving from a single direction, each hitting the surface once, transforms existing cavities into transient features (similar to scallops, flutes, and pits), which shrink and eventually vanish. However, by incorporating additional impacts within the features from rebounding particles, persistent, continuously growing features emerge. We conclude that: (1) rebounding particles concentrate their effect within features, and therefore increase their size; (2) the development of features is sensitive to material type; and (3) the ultimate maximum feature scale is related to the size of the rock, and the size and velocity of impactors. Our model helps organize diverse ventifact field observations into an initial framework of pattern formation and confirms field and laboratory observations that the most common features are linear in wind-parallel directions. [Copyright &y& Elsevier]

Abstract: In the Western Pannonian Basin the widespread occurrence of ventifacts and large-scale deflation features indicate strong wind activity during the Quaternary. Pleistocene glaciations are probably the most important periods of wind erosion. However, age of the wind-polished rock surfaces exposed on different geomorphic horizons has remained unknown so far, although they can provide time constraints of landscape evolution. Measurements of 10Be concentrations along depth profiles of exposed wind-facetted rocks allow deriving local denudation rates of 3.46–3.88 m/Ma and exposure ages as old as 1.5 Ma. Regional denudation, which occurred mainly via deflation of the loose sediments, varies between 40 and 80 m/Ma. This study provides evidence that aeolian erosion in continental, periglacial areas of Central Europe played an important role in Quaternary landscape modification. [Copyright &y& Elsevier]

Rill erosion can be a large portion of the total erosion in disturbed forests, but measurements of the runoff and erosion at the rill scale are uncommon. Simulated rill erosion experiments were conducted in two forested areas in the northwestern United States on slopes ranging from 18 to 79%. We compared runoff rates, runoff velocities, and sediment flux rates from natural (undisturbed) forests and in forests either burned at low soil burn severity (10 months or 2 weeks post-fire), high soil burn severity, or subject to skidding of felled logs. The runoff rates and velocities in the natural sites (2.7 L min−1 and 0.016 m s−1, respectively) were lower than those in all the disturbed sites (12 to 21 L min−1 and 0.19 to 0.31 m s−1, respectively), except for the 10-month old low soil burn severity site where the velocity (0.073 m s−1) was indistinguishable from the natural sites. The mean sediment flux rate in the natural sites also was very small (1.3 × 10−5 kg s−1) as compared to the rates in the disturbed areas (2.5 × 10−4 to 0.011 kg s−1). The hillslope gradient did not affect the runoff or sediment responses. The sediment flux rates generally were greater in the initial stage of each inflow period than in the steady state condition, but there was no corresponding transient effect in runoff rates. Rill erosion modeling implications based on these data are presented in part 2 of this study. [ABSTRACT FROM AUTHOR]

Soil preservation from three glacial thermal regimes was examined in the Transantarctic Mountains (TAM) using the University of Wisconsin Antarctic Soils Database (http://nsidc.org/data/ggd221). Glacial thermal regimes included temperate (wet-based) glaciers from overriding of the TAM prior to c. 15Ma BP and subsequent polar (dry-based) glaciers. The glacial thermal regimes were distinguished from landform, sediment and erosional features. Buried soils were most common from deposition by dry-based glaciers (44 of 51 pedons). Several of these buried soils had a desert pavement intact with in situ ventifacts. Fifteen percent of the pedons contained recycled ventifacts in relict and buried soils that ranged from late Quaternary to Miocene in age, particularly in drift from dry-based glaciers (56 of 77 pedons). Overall 84% of the buried soils and 78% of the pedons with recycled ventifacts originated from dry-based glaciers. The proportion of soils with recycled clasts on a particular drift was greatest where the ratio of drift thickness to soil thickness (''recycling ratio'') was the least. These data illustrate the effectiveness of Antarctic dry-based glaciers in preserving underlying landforms and deposits, including soils. Moreover, the data imply that Antarctic glaciers have been recycling clasts for the past c. 15 Ma. These findings have important implications in selecting surface boulders for cosmogenic dating. [ABSTRACT FROM AUTHOR]

Abstract: The “seven-coloured earth” of Chamarel is a geological curiosity and a major tourist attraction of Mauritius. This is a small (∼7500m2) area of strikingly bare landscape showing well-developed rills and various shades of red, brown, grey, and purple. Curiously, it is located within a large, dense forest. Prevalent misconceptions are that the landscape formed due to a volcanic eruption, or from volcanic ash. Whereas the bedrock is undoubtedly an old volcanic rock (basalt), the colours are due to weathering of the basalt and the formation of secondary iron oxides and hydroxides in it, and the rilling is a result of deforestation and sheet erosion, i.e., human modification of the landscape. Such features, inadequately described in the literature so far, also occur in Papua New Guinea, and may be common in tropical, high-rainfall regions with volcanic bedrock. [Copyright &y& Elsevier]

The article discusses findings of a study which computed cumulative runoff and soil particles in a distributed model with Geographic Information System (GIS) using single flow (D8), multiple flow (MD) and combined flow (MDD) algorithms. To address the problem of soil loss in mountain agricultural landscapes, soil erosion by water should be assessed. Examples of landforms that describe processes of soil erosion by water included gullies, rills and gorges.

The article presents a study on the impact of soil erosion resistance (SER) to the rill and gully initiation points in Belgium. The findings of the study reveals that soil erodibility is one factor to determine the lengths of the concentrated flow paths. Moreover, the results show that SER can control the rill and gully initiation points.

Abstract: An area north of Lake Fryxell in the Taylor Valley, Antarctica, was surveyed to determine the frequency of occurrence of rocks that show strong evidence of wind abrasion and ventifaction, which is defined here as rocks having well-developed faceting, to define their relative abundance in this area of the ice-free McMurdo Dry Valley system and to provide an indication of the role of wind as a geomorphic agent in this area. The orientation of abrasion-caused features (facets, keels, and grooves) with respect to the present day wind regime is also described. Rocks were examined on five linear transects ranging from 300 to 510 m in length. A total of 1324 rocks were examined. On average, 60% of all rocks exhibited distinct wind abrasion features with polish being the most common feature and polished rocks were distributed equally between survey lines, suggesting abrasion was ubiquitous in the study area. Approximately 4% of the rocks had distinct facets and/or keels, and fine-grained ultramafic peridotite-type rocks produced the most finely-featured forms (i.e., sharp facet edges and keels). A larger percentage, ≈12.5%, had grooves. Grooves were typically associated with a tabular form of mafic diabase-type igneous rock. The distribution of faceted ventifacts and grooved rocks was not uniform for the five transects, suggesting that the distribution mechanism for the surface rocks and the source areas determined, to a large extent, what form of ventifact could be produced at a location. The orientation of the grooves and dip directions of the facets indicates the direction of the abrasive winds had a strong westerly component, which coincides with the modern wind regime of winter katabatic flows that move down valley toward the Ross Sea. The orientation of the facets and grooves suggests that the rate of formation of the ventifacts proceeds at a pace greater than other surficial processes (e.g., down-slope soil movement, cryoturbation), which should tend to remove trends in the facet and groove orientations, or that the down-slope movement of the surface is approximately perpendicular to the wind allowing preservation of the alignment. [Copyright &y& Elsevier]

Abstract: Terrestrial ventifacts – rocks that have been abraded by windblown particles – are found in desert, periglacial, and coastal environments. On Mars, their abundance suggests that aeolian abrasion is one of the most significant erosional processes on the planet. There are several conflicting viewpoints concerning the efficacy of potential abrasive agents, principally sand and dust, and the relationships between wind direction and ventifact form. Our research, supported by a review of the literature, shows that sand, rather than dust or other materials, is the principle abrasive agent on Earth and Mars. Relative to dust, sand delivers about 1000× the energy onto rock surfaces on a per particle basis. Even multiple dust collisions will do little or no damage because the stress field from the impact is much smaller than the spacing of microflaws in the rock. The abrasion profiles of terrestrial ventifacts are consistent with a kinetic energy flux due to saltating sand, not airborne dust. Furthermore, Scanning Electron Microscope images reveal surfaces that are fractured and cleaved by sand grain impact. With respect to their distribution, ventifacts are found in regions that contain sand or did so in the past, but are not found where only dust activity occurs. Contrary to some published reports, our evidence from field studies, analytical models, and wind tunnel and other experiments indicates that windward, not leeward, abrasion is responsible for facet development and feature formation (pits, flutes, and grooves). Leeward abrasion is confined to fluvial conditions, in which the high viscosity and density of water are able to entrain sand-size material in vortices. Therefore, ventifacts and abraded terrain provide an unambiguous proxy for the direction of the highest velocity winds, and can be used to reconstruct palaeowind flow. [Copyright &y& Elsevier]

Abstract: Rivers draining to the Great Barrier Reef are receiving increased attention with the realisation that European land use changes over the last ∼150 years may have increased river sediment yields, and that these may have adversely affected the reef environment. Mitigation of the effects associated with such changes is only possible if information on the spatial provenance and dominant types of erosion is known. To date, very few field-based studies have attempted to provide this information. This study uses fallout radionuclide (137Cs and 210Pbex) and geochemical tracing of river bed and floodplain sediments to examine sources over the last ∼250 years for Theresa Creek, a subcatchment of the Fitzroy River basin, central Queensland, Australia. A Monte Carlo style mixing model is used to predict the relative contribution of both the spatial (geological) sources and erosion types. The results indicate that sheetwash and rill erosion from cultivated basaltic land and channel erosion from non-basaltic parts of the catchment are currently contributing most sediment to the river system. Evidence indicates that the dominant form of channel erosion is gully headcut and sidewall erosion. Sheetwash and rill erosion from uncultivated land (i.e., grazed pasture/woodland) is a comparatively minor contributor of sediment to the river network. Analysis of the spatial provenance of floodplain core sediments, in conjunction with optical dating and 137Cs depth profile data, suggests that a phase of channel erosion was initiated in the late nineteenth century. With the development of land underlain by basalt in the mid-twentieth century the dominant source of erosion shifted to cultivated land, although improvements in land management practices have probably resulted in a decrease in sediment yield from cultivated areas in the later half of the twentieth century. On a basin-wide scale, because of the limited spatial extent of cultivation, channel sources are likely to be the largest contributor of sediment to the Fitzroy River. Accordingly, catchment management measures focused on reducing sediment delivery to the Great Barrier Reef should focus primarily on decreasing erosion from channel sources. [Copyright &y& Elsevier]

The article presents a study on the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogenous mine spoil on an angle of repose slope, and the ability of the SIBERIA erosion model to imitate the rill's spatial and temporal behavior. Results showed that while the overall hillslope morphology was captivated by the laser scanner, with the morphology of the rills being widely captured, the characteristics pf the rills were not well defined. Also, the digital elevation model produced by the laser scanner failed to capture the rill thalwegs and tops of the banks, delineating a range of ill defined longitudinal downslope depressions. The sensitivity of the SIBERIA model to changes in parameters and the relevance of the calibration process is also shown.

A pavement of faceted pebbles of haematite ore has been discovered in Amazonia. It occurs on the top of a lateritic plateau in Carajás, beside lakes and marshes where the available palynological data indicate dry periods during the Pleniglacial. The pebbles have pyramidal tops and characteristic polished facets. They are interpreted as ventifacts additionally worn by fluvial action. The possible occurrence of ventifacts may represent the erosional manifestation, hitherto unrecognised, of the Ice Age aridity recorded in these Amazonian lacustrine sediments. [ABSTRACT FROM AUTHOR]

The delineation of Geomorphic Process Units (GPUs) aims to quantify past, current and future geomorphological processes and the sediment flux associated with them. Five GPUs have been identified for the Okstindan area of northern Norway and these were derived from the combination of Landsat satellite imagery (TM and ETM+) with stereo aerial photographs (used to construct a Digital Elevation Model) and ground survey. The Okstindan study area is sub-arctic and mountainous and is dominated by glacial and periglacial processes. The GPUs exclude the glacial system (some 37% of the study area) and hence they are focussed upon periglacial and colluvial processes. The identified GPUs are: 1. solifluction and rill erosion; 2. talus creep, slope wash and rill erosion; 3. accumulation of debris by rock and boulder fall; 4. rockwalls; and 5. stable ground with dissolved transport. The GPUs have been applied to a 'test site' within the study area in order to illustrate their potential for mapping the spatial distribution of geomorphological processes. The test site within the study area is a catchment which is representative of the range of geomorphological processes identified. [ABSTRACT FROM AUTHOR]

Examples of ventifacts and forms of unusual patterned ground that differ in situation, characteristics and/or origin to types reported previously are described from the Falkland Islands, South Atlantic. The ventifacts, represented by clasts projecting from an eroding tillite shore platform, have been grooved by the passage of windblown sand. The patterned ground forms comprise stone polygons on clay loam regolith, stone polygons on peat, peat-filled desiccation cracks on peat, and clusters of on-edge clasts (stone packings) on a gravel beach. Aeolian transport of particles is considered responsible for the infill of the polygonal cracks. The clusters of on-edge clasts are thought to have developed as a result of wave action, in particular backwash and/or undertow. Although these features occupy small surface areas they provide useful information about local geomorphic processes and testify to the marked diversity of such features in nature. [ABSTRACT FROM AUTHOR]

Wind tunnel studies are integrated with field observations to better understand the processes and rates of rock abrasion on Earth and Mars and how these factors affect ventifact morphology. The wind tunnel work consists of controlled experiments at terrestrial and Martian pressures in which known fluxes of sand are blown onto abradable targets of various geometric shapes. Mass loss and dimensional changes are measured and shape evolution observed as a function of total sand flux, wind speed, target shape, and target composition. To provide ground truth to these experiments, the same types of targets were placed in a field plot at a Mojave Desert ventifact locality for 6 months and measurements and observations like those in the wind tunnel were made. Weather data recorded by a co-located station provided wind speed and direction during this time. These data and results from the abraded field targets were compared to flute directions of local ventifacts. Initial results from this work are: (1) initial rock shape controls the rate of abrasion, with steeper faces abrading faster than shallower ones, (2) targets also abrade via slope retreat, with intermediate angled faces becoming shallower (flatter) at a greater rate than initially flat or steep faces, (3) the direction of maximum velocity winds exerts a greater control on ventifact flute orientations than the direction of average velocity winds, (4) irregular targets with pits or grooves abrade at greater rates than targets with smooth surfaces, with indentations generally enlarging and faces becoming rougher with time, and (5) there are many similarities between the experimental and terrestrial ventifacts, as well as rocks interpreted as ventifacts on Mars. The pitted and faceted appearance of many Martian rocks is easily attributable to aeolian abrasion. Many Martian rocks appear pitted or vesicular, characteristics which our laboratory experiments show enhance abrasion. Although measured Martian wind speeds are generally below those necessary to induce saltation, occasional gusts above threshold may be sufficient for some rock abrasion. Ventifact formation is potentially a common geomorphic process on Mars provided there are sufficient supplies of sand and high velocity winds needed for saltation. [Copyright &y& Elsevier]

Reports that the unusual location of ventifacts, on a boulder-built jetty at the mouth of the Siuslaw River, Oregon coast, western USA, allows ventifact age and wind abrasion rates to be estimated with some precision. Consideration of historical shoreline position and the history of jetty construction and repair that suggests the ventifacts have formed since about 1930; Morphologically the ventifacts that are aligned south-to-north reflecting winter winds and sediment transport from the adjacent beach; Wind-parallel grooves and ridges with sharp, sinuous crests that are developed on inclined boulder surfaces on top of the jetty and reflect suspended sand transport in wind vortices; Deeply pitted surfaces on steep boulder surfaces nearest the beach that reflect impact by saltating sand grains; Southerly winds above the sand transport threshold that occur; Wind abrasion rates that are calculated; Estimate of ventifact age and ventifaction rate from a modern coastal environment.

Describes the formation of bedrock-cut ventifacts and Late Holocene coastal zone evolution in Donegal County, Ireland. Parameters associated with the formation of ventifacts; Occurrence and morphology of coastal ventifacts; Correlation of ventifacts characteristics with the context of Late Holocene environmental change.