Grasslands cover 40 % of the earth's surface and store 10 % of the global soil carbon stock. Their degradation weakens its capacity to support biodiversity, ecosystem services and human well-being, as well as soil carbon storage. Research on how different strategies affect soil carbon accumulation in South Africa's semi-arid regions, particularly the Free State, is scarce. This study aimed to establish land management strategies suitable for enhancing soil organic carbon (SOC) storage in South African grasslands. DAYCENT carbon model was used to simulate SOC under various management scenarios; soil samples were collected to parameterize the model and further analyse carbon amount in each soil type. Results indicate that Lixisols can store more carbon compared to other soil types, with higher carbon concentrations linked to soils with higher silt content, while less carbon was found in soils with high sand content such as Arenosols. Carbon was stored differently based on soil depth, with new carbon in shallow depths and old carbon in deeper layers. Simulation results suggest that grasslands with moderate grazing could enhance shallow carbon storage over time. The work suggests that native grassland has the potential to act as a significant carbon sink with improved management practices.

The west coast of South Africa is an arid region that has been shown to be emissive, but its dust sources have never been studied in detail. In this study, we present a dataset of the Moderate Resolution Imaging Spectroradiometer (MODIS)-detected dust source points in this region from 2000 to 2021 and the surface characteristics of these points. The results elucidate that most dust source points are located on Succulent Karoo shrublands, mining areas, or bare areas. Furthermore, the data show a significant increase in dust source points, which could mainly be attributed to shrublands becoming more emissive as a response to a prolonged drought from 2017 onwards. The Normalised Difference Vegetation Index (NDVI), Modified Soil Adjusted Vegetation Index (MSAVI), and albedo-based roughness indication (omega ns) of the study area confirmed a decrease in vegetation during this five-year drought. Understanding such tipping points for dust emissions as a result of drought and anthropogenic land use is relevant to understanding the future dust load.

Mineral dust dispersion plays a significant role in a variety of natural Earth system processes. This chapter focuses on the identification of major dust sources worldwide. Over the last 20 years a variety of Earth observation sensors have been utilized to identify sources of dust, chiefly by detecting atmospheric aerosols and individual plumes from the TOMS (Total Ozone Mapping Spectrometer), SEVIRI (Spinning Enhanced Visible and InfraRed Imager), MODIS (MODerate resolution Imaging Spectroradiometer) as well as Landsat records. The ability to map aerosols and source points is constrained by several limitations, but overall, has enabled the detection of major dust hotspots around the globe. Many of these have been subject to ground-based inquiries. While we focus on Southern Africa results, much of the world's dust originates from the Sahara and other arid regions. Emissions from high-latitude glacial outwash valleys and anthropogenic activities, such as mining are also noted. The chapter then summarizes the prevailing geomorphological conditions and processes which contribute to dust emissions for a variety of landscape settings and associated landforms. Field equipment and instrumentation used to characterize the nature of dust emissions are briefly introduced. These quantify aerosols in the atmospheric column, determine air quality and allow sampling for physical and geochemical particle analyses. Collectively these techniques provide some insight into the impact of dust. Our full understanding of the extent, nature and controls of mineral dust as well as its impacts at the global scale remain incipient. Results of global dust attribution and modelling efforts are still accompanied by uncertainties. Challenges are numerous and are hindered by the wide range of scales associated with dust research, which include coarse resolution Earth observation data, variable emission at the landform scale, as well as the heterogeneity of particles to name a few.

ABSTRACTAfrican elephants (Loxodonta africana) are megaherbivores of the African savannas requiring extensive ranges that can provide critical resources for their survival and reproduction at different spatiotemporal scales. We studied seasonal differences in home range sizes and daily distance to the nearest surface water sources by five male and 10 female African elephants in the eastern Okavango Panhandle in northern Botswana between 2014 and 2017. We hypothesized that (i) elephant home ranges would be larger in the wet than in the dry season (because critical resources tend to be less localized in the wet than in the dry season), (ii) the daily distance of the elephants to the nearest ephemeral surface water sources would be larger in the dry than in the wet season because many of the ephemeral water sources would be dry in the dry season and elephants would start moving towards permanent water sources such as rivers, and lastly (iii) that the differences in elephant home ranges and daily distance to water would differ between sexes. Our results showed that elephant home ranges were larger in the wet than in the dry season, and that they differed between sexes with female elephants having smaller home ranges in the late wet season. The mean daily distance to the nearest ephemeral surface water sources was larger in the dry than in the wet season. There was an inverse relationship between elephants' daily distance to permanent surface water and to ephemeral water sources. The findings indicate the need for large conservation areas and functional connectivity between landscapes to enable the highly mobile savanna elephants to access critical seasonal resources such as water and forage in semi‐arid savannas. Such landscapes are critical, especially in the face of climate change, when high air temperatures and droughts may exacerbate forage and water shortage and intensify human–elephant interactions in surrounding agroecosystems.

Sand and dust storms are natural environmental processes that occur at various scales and they can have significant ecological and social impacts. Globally, patterns of aeolian activities are changing, and on South Africa’s west coast a marked increase in dust emission was observed during a prolonged drought lasting from 2015 to 2022. This region, dominated by Succulent Karoo shrublands, experienced a decline in vegetation cover and shifts in vegetation states due to the combined effects of drought, grazing, mining activities, and wind erosion.This review examines the transition in vegetation cover, the environmental and anthropogenic processes driving these changes, and their relationship to increased wind erosion and dust emission. Key influencing factors include rainfall variability, grazing intensity, and the degrading effects of wind erosion, shaped by broader forces such as climate change and land-use practices like mining and limited crop farming. To synthesise these dynamics, we present a conceptual State-and-Transition Model (STM) that captures vegetation responses in arid ecosystems and integrates the feedback between vegetation loss, wind erosion, and dust emission. This research furthermore summarises the broader consequences of dust events, including soil degradation, public health risks, and off-site effects on ocean chemistry and marine ecosystems. Understanding the drivers of vegetation change and the role of human and climatic pressures is crucial for anticipating future atmospheric dust loads and managing the resilience of arid landscapes.

AbstractSoil erosion has been identified as an issue in South African farming for more than a century. Erosion of land surfaces by water or wind is a natural process which might be accelerated directly by human impact on land surface properties, e.g., vegetation and soils. An assessment of soil erosion risk indicates average soil loss rates two orders of magnitude larger than long-term soil formation rates. This challenging condition clearly underlines the need for continuous application of established policies and principles as well as emerging modes of conservation agriculture in farming activities in most parts of South Africa. In addition, conservation agriculture has been shown to have positive effects on the cost–value ratio, but diffusion and adoption of this innovative approach still meet resistance often founded in traditional faith and belief systems. However, to cope with challenges from global climate change, e.g., intensified extreme weather conditions (droughts and flooding), strengthened resilience of farming systems is required to i) meet increased domestic and global demand for food and ii) to put into practice sustainable management to diminish on-site and off-site damages from soil erosion on the way to reach sustainable development goals.

The temporal coupling of the structural evolution of the Kalahari Basin and the accumulation of the Kalahari Group sediments has been an accepted paradigm leading to the assumption that the Kalahari group sediments have been accumulating gradually since the mid-Cretaceous. Here we review the first actual ages for the Kalahari Group based on cosmogenic ages from six geological localities. These results demonstrate that Kalahari Basin infill was a more dynamic process than previously thought and that the Kalahari Group sediments are mostly Plio-Pleistocene in age (similar to 4 Ma to 1-2 Ma). The hiatus between the initial structural subsidence of the basin, during the Cretaceous, and the general young age of the investigated sediments, implies a dynamic landscape in which significant phases of erosion occurred during the Mesozoic and Cenozoic. The magnitude of erosion is manifested by the fact that in many locations Kalahari Neogene to Quaternary sediments overlie Precambrian basement. The age of the present infill of the Kalahari thus falls within the temporal range of the genus Homo. In light of this new understanding, we provide a review of the archaeological evidence from the Kalahari Basin and along its southern fringe. Initial hominin presence is found at Wonderwerk Cave during the Olduvai Event and there is subsequent high-density occupation along the southern fringe of the Kalahari Basin during the Acheulean and the Fauresmith. Middle Stone Age occupation is limited to localities of limited size and small artifact counts and it appears that the focus of human occupation, particularly in the later stages of the Middle Stone Age, shifts southward, including along the coastal regions.

The port and industrial zone of Saldanha Bay in South Africa accommodates activities related to the transport, processing, and production of commodities such as iron ore, manganese ore, and steel. The visible emission of dust from this area raised concerns for public health and to address this, the municipality has monitored the fine particulate matter (PM2.5) concentration and dust deposition since 2015. Here, this monitoring data served to assess spatial and temporal changes and to evaluate the potential contribution of industrial and meteorological processes to these changes. We observed high temporal variability in both PM2.5 concentration and dust deposition, and high spatial variation in dust depositions. Dust originated from local sources such as industry and traffic, but industrial activities could not explain the observed spatial variability, and concentration and deposition fluxes did not significantly increase over the years despite the extension of industrial activities. Meteorological factors such as rain, wind speed, wind direction, as well as topography exerted an important influence, but could also only partially explain the observed variability in both dust concentration and deposition. Furthermore, the PM2.5 concentration and dust deposition are not significantly correlated, which highlights the challenges in appropriate dust monitoring. It follows that such monitoring efforts, though meeting national standards, require improvement to assess risks accurately. Our study illustrates that in areas with such high complexity of industrial activities, the high variability of dust load and deposition must be considered to evaluate implications for public and environmental health, adherence to guidelines, and mitigation strategies.

Most protected area impact research that uses counterfactuals draws heavily on quantitative methods, data, and knowledge types, making it valuable in producing generalizations but limited in temporal scope, historical detail, and habitat diversity and coverage of ecosystem services. We devised a methodological pluralistic approach, which supports social science qualitative methods, narratives, mixed methods, and interdisciplinarity, to fully unlock the potential of counterfactuals in ensuring a place-based and detailed understanding of the socioecological context and impacts of protected areas. We applied this approach to derive possible counterfactual conditions for the impact of a montane protected area on 40 years of vegetation change in the Cape Floristic Region-a global biodiversity hotspot and UNESCO World Heritage Site in South Africa. We incorporated diverse methods, knowledge, and information sources, drawing on before-after protected area comparisons for inside and outside the protected area. A significant increase in shrubland vegetation (17-30%) was observed and attributed primarily to a decline in frequent burning for grazing. This also occurred outside the protected area and was driven by socioeconomic drivers and not by concerns over biodiversity conservation or land degradation. Had the protected area not been established the area would have seen intensification of cultivation and increased road networks, buildings, and water storage in dams. Our approach increased historical temporal coverage of socioecological change and contextualized assumptions around causality. Protected area impact evaluation should reengage in place-based research that fully incorporates pluralism in methodologies for constructing counterfactuals in a way that builds regional and global understanding from the local level upward. We devised 10 key principles for deriving counterfactuals grounded in methodological pluralism, covering aspects of collaboration, cocreation, inter- and transdisciplinarity, diverse values and lived experiences, multiple knowledge types, multiple possible causal mechanisms, social science qualitative methods, perceptions, perspectives, and narratives.

Water availability is the dominant driver of microbial community structure and function in desert soils. However, these habitats typically only receive very infrequent large-scale water inputs (e.g., from precipitation and/or run-off). In light of recent studies, the paradigm that desert soil microorganisms are largely dormant under xeric conditions is questionable. Gene expression profiling of microbial communities in desert soils suggests that many microbial taxa retain some metabolic functionality, even under severely xeric conditions. It, therefore, follows that other, less obvious sources of water may sustain the microbial cellular and community functionality in desert soil niches. Such sources include a range of precipitation and condensation processes, including rainfall, snow, dew, fog, and nocturnal distillation, all of which may vary quantitatively depending on the location and geomorphological characteristics of the desert ecosystem. Other more obscure sources of bioavailable water may include groundwater-derived water vapour, hydrated minerals, and metabolic hydro-genesis. Here, we explore the possible sources of bioavailable water in the context of microbial survival and function in xeric desert soils. With global climate change projected to have profound effects on both hot and cold deserts, we also explore the potential impacts of climate-induced changes in water availability on soil microbiomes in these extreme environments.

Establishing mineral dust impacts on Earth's systems requires numerical models of the dust cycle. Differences between dust optical depth (DOD) measurements and modelling the cycle of dust emission, atmospheric transport, and deposition of dust indicate large model uncertainty due partially to unrealistic model assumptions about dust emission frequency. Calibrating dust cycle models to DOD measurements typically in North Africa, are routinely used to reduce dust model magnitude. This calibration forces modelled dust emissions to match atmospheric DOD but may hide the correct magnitude and frequency of dust emission events at source, compensating biases in other modelled processes of the dust cycle. Therefore, it is essential to improve physically based dust emission modules. Here we use a global collation of satellite observations from previous studies of dust emission point source (DPS) dichotomous frequency data. We show that these DPS data have little-to-no relation with MODIS DOD frequency. We calibrate the albedo-based dust emission model using the frequency distribution of those DPS data. The global dust emission uncertainty constrained by DPS data (±3.8 kg m-2 y-1) provides a benchmark for dust emission model development. Our calibrated model results reveal much less global dust emission (29.1 ± 14.9 Tg y-1) than previous estimates, and show seasonally shifting dust emission predominance within and between hemispheres, as opposed to a persistent North African dust emission primacy widely interpreted from DOD measurements. Earth's largest dust emissions, proceed seasonally from East Asian deserts in boreal spring, to Middle Eastern and North African deserts in boreal summer and then Australian shrublands in boreal autumn-winter. This new analysis of dust emissions, from global sources of varying geochemical properties, have far-reaching implications for current and future dust-climate effects. For more reliable coupled representation of dust-climate projections, our findings suggest the need to re-evaluate dust cycle modelling and benefit from the albedo-based parameterisation.

Dust models are essential for understanding the impact of mineral dust on Earth's systems, human health, and global economies, but dust emission modelling has large uncertainties. Satellite observations of dust emission point sources (DPS) provide a valuable dichotomous inventory of regional dust emissions. We develop a framework for evaluating dust emission model performance using existing DPS data before routine calibration of dust models. To illustrate this framework's utility and arising insights, we evaluated the albedo-based dust emission model (AEM) with its areal (MODIS 500 m) estimates of soil surface wind friction velocity (us∗) and common, poorly constrained grain-scale entrainment threshold (u∗ts) adjusted by a function of soil moisture (H). The AEM simulations are reduced to its frequency of occurrence, P(us∗>u∗tsH). The spatio-temporal variability in observed dust emission frequency is described by the collation of nine existing DPS datasets. Observed dust emission occurs rarely, even in North Africa and the Middle East, where DPS frequency averages 1.8 %, (~7 days y-1), indicating extreme, large wind speed events. The AEM coincided with observed dust emission ~71.4 %, but simulated dust emission ~27.4 % when no dust emission was observed, while dust emission occurrence was over-estimated by up to 2 orders of magnitude. For estimates to match observations, results showed that grain-scale u∗ts needed restricted sediment supply and compatibility with areal us∗. Failure to predict dust emission during observed events, was due to us∗ being too small because reanalysis winds (ERA5-Land) were averaged across 11 km pixels, and inconsistent with us∗ across 0.5 km pixels representing local maxima. Assumed infinite sediment supply caused the AEM to simulate dust emission whenever P(us∗>u∗tsH), producing false positives when wind speeds were large. The dust emission model scales of existing parameterisations need harmonising and a new parameterisation for u∗ts is required to restrict sediment supply over space and time.

Maps generated from various data sources reveal ten new megafans in the northern Kalahari region where, until now, the Okavango had been the only one recognised. Seven megafans were generated by rivers flowing off the Bie Swell of southern Angola, east to the Zambezi basin and south to the Owambo basin. Only three (Okavango, Cuando, Zambezi) are apexed at shoulders of the Okavango Rift (northern Botswana). Unusually, the Cubango/Okavango River has given rise to two megafans: the upstream Cubango megafan, and the well-known Okavango megafan downstream. Avulsion behaviour of three rivers has also demonstrably shifted discharge between major basins over time: the Cassai has, at times, flowed north into the Congo basin; the Cubango flowed into the Owambo basin (Etosha dry lake), but now discharges into the Makgadikgadi basin (via the Okavango megafan); and the Kunene, which now flows to the Atlantic Ocean, at one time discharged into the Etosha pan. Recognising the existence of so many more megafans than previously appreciated, as well as their autogenic, avulsive dynamics, is an invitation to reconsider the regime of sedimentary sequence deposition in these basins, which may have erroneously been interpreted as resulting from climatic or other external forcing factors.

Abstract. Measurements of dust in the atmosphere have long been used to calibrate dust emission models. However, there is growing recognition that atmospheric dust confounds the magnitude and frequency of emission from dust sources and hides potential weaknesses in dust emission model formulation. In the satellite era, dichotomous (presence = 1 or absence = 0) observations of dust emission point sources (DPS) provide a valuable inventory of regional dust emission. We used these DPS data to develop an open and transparent framework to routinely evaluate dust emission model (development) performance using coincidence of simulated and observed dust emission (or lack of emission). To illustrate the utility of this framework, we evaluated the recently developed albedo-based dust emission model (AEM) which included the traditional entrainment threshold (u*ts) at the grain scale, fixed over space and static over time, with sediment supply infinite everywhere. For comparison with the dichotomous DPS data, we reduced the AEM simulations to its frequency of occurrence in which soil surface wind friction velocity (us*) exceeds the u*ts, P(us* > u*ts). We used a global collation of nine DPS datasets from established studies to describe the spatio-temporal variation of dust emission frequency. A total of 37,352 unique DPS locations were aggregated into 1,945 1° grid boxes to harmonise data across the studies which identified a total of 59,688 dust emissions. The DPS data alone revealed that dust emission does not usually recur at the same location, are rare (1.8 %) even in North Africa and the Middle East, indicative of extreme, large wind speed events. The AEM over-estimated the occurrence of dust emission by between 1 and 2 orders of magnitude. More diagnostically, the AEM simulations coincided with dichotomous observations ~71 % of the time but simulated dust emission ~27 % of the time when no dust emission was observed. Our analysis indicates that u*ts was typically too small, needed to vary over space and time, and at the grain-scale u*ts is incompatible with the us* scale (MODIS 500 m). During observed dust emission, us* was too small because wind speeds were too small and/or the wind speed scale (ERA5; 11 km) is incompatible with the us* scale. The absence of any limit to sediment supply caused the AEM to simulate dust emission whenever P (us* > u*ts), producing many false positives when and where wind speeds were frequently large. Dust emission model scaling needs to be reconciled and new parameterisations are required for u*ts and to restrict sediment supply varying over space and time. Whilst u*ts remains poorly constrained and unrealistic assumptions persist about sediment supply and availability, the DPS data provide a basis for the calibration of dust emission models for operational use. As dust emission models develop, these DPS data provide a consistent, reproducible, and valid framework for their routine evaluation and potential model optimisation. This work emphasises the growing recognition that dust emission models should not be evaluated against atmospheric dust.

Minimizing wind erosion on agricultural fields is of great interest to farmers. There is a general understanding that vegetation can greatly minimize the wind erosion taking place. However, after harvest, a low vegetation cover can be inevitable, whereby the amount of stubble that remains on a field is dependent on the crop type and land management. This study aims at quantifying the vulnerability to wind erosion of different crops, and the possibility to predict the vulnerability based on high precision aerial images. The study area was the semi-arid Free State, which holds large intensive agriculture on sandy soils. These croplands have been identified as the largest emitter of dust in South Africa. The main crop in the region is maize, but also sunflower, peanut and fallow fields are common land-use types. On these fields, the horizontal sediment flux, the saltation threshold, and aerodynamic roughness length were measured, and the soil cover was assessed using Unmanned Aerial Vehicle (UAV) imagery. The results showed a strong relationship between the soil cover and the sediment flux, whereby fallow and groundnut fields have the highest wind erosion risk. These results emphasize the great importance of soil cover management to prevent wind erosion.

Microbes have a dominant role in nutrient cycling processes in the world's deserts, where growth and activity are limited by the availability of water. In order to understand the dynamics of water availability in a desert system and how it may affect the soil microbiome, we analysed soil temperature and relative humidity fluctuations recorded between April 2018 and April 2020 across a precipitation gradient in the Namib Desert and compared them with recorded data from satellites and nearby weather stations. This allowed us to assess the possible impact of fog and rain events in terms of biologically-available water. Using published literature on the water activity limits for various physiological processes in microorganisms, we were able to infer the annual 'metabolic windows' for desert microbial communities across the longitudinal precipitation gradient. Specifically, soil surface microbial communities were estimated to have the capacity for active growth for an average of 184- 363 hours per year with the duration heavily dependent on intermittent rainfall events. During the relatively wet period of April 2018 - March 2019, the maximum growth window was found in the hyper-arid central region of the transect (approximately 100 km from the coast). During the dryer 2019- 2020 period, there was almost no predicted growth capacity in the hyper-arid region but substantial metabolic windows both near the coast and for the eastern inland areas, where water input comes in the form of fog and moist coastal air, and higher rainfall, respectively. As the first detailed study of the temperature and relative humidity characteristics of Namib Desert near-surface soils, this study provides valuable insights into the biogeography of microbial communities. In addition, the estimates for organismal functionality calculated in this study offer a baseline for future quantitation of the impacts of climate change on the functional capacity of desert soil microbiomes.

Determining the controls on aeolian dust emissions from major sources is necessary for reliable quantification of atmospheric aerosol concentrations and fluxes. However, ground‐based measurements of dust emissions at‐source are rare and of generally short duration, failing to capture the annual cycle. Here, we provide new insights into dust dynamics by measuring aerosol concentrations and meteorological conditions for a full year (July 2015–June 2016) at Etosha Pan, Namibia, a globally significant dust source. Surface deployed field instrumentation provided 10‐min averaged data on meteorological conditions, aerosol concentration (mg/m 3 ), and horizontal dust flux (g/m 2 /min 10 ). A Doppler lidar provided additional data for some of the period. 51 significant dust events were identified in response to strong E‐ENE winds. We demonstrate that these events occurred throughout the year and were not restricted to the austral winter, as previously indicated by satellite observations. Peak horizontal flux occurred in the spring (November) due to strengthening erosive winds and highly desiccating conditions increasing surface erodibility. We identify a strong seasonal differentiation in the meteorological mechanisms controlling dust uplift; low‐level jets on dry winter mornings (61% of all events), and cold pool outflows in humid summer evenings (39% of events). Significantly, we demonstrate a very strong bias toward the contribution of low frequency and high magnitude events, with nearly 31% of annual horizontal dust flux generated by only 6 individual events. Our study demonstrates how longer‐term (≈1 year), ground‐based, and at‐source field measurements can radically improve interpretations of dust event dynamics and controls at major source locations.

This chapter provides a short overview of geologicalGeological units that have surface expression along with the dominant landforms and landscapes of BotswanaBotswana. It introduces the western portion of the country which features young regional arenosolsArenosols and is home to few outcrops. This is often simply referred to as the Kalahari. The exception is the GhanziGhanzi RidgeRidge, a highly denuded PrecambrianPrecambrian Orogen, sitting between two regional, but largely concealed cratonsCraton. The lower-lying east is home to Archean hills and the countries major drainageDrainage network. The second part of the introduction covers the geomorphic settings associated with the various book chapters with much focus on the landscapes of the Kalahari, northern Botswana and eastern lowveldLowveld. Especially the north and northeast are home to a variety of fluvial systems, which include the Okavango, ZambeziZambezi Catchments and MakgadikgadiMakgadikgadi dry lakeLake. In conclusion, this chapter draws attention to the tertiary education of geomorphology in BotswanaBotswana.

SUMMARY This study explores the geomorphological expression and geological context of a normal fault scarp in a stable continental region (SCR) which we interpret as having failed in large (Mw >7) earthquakes. Records of such large normal faulting events in an SCR (or even in more rapidly deforming regions) are extremely rare, and so understanding this feature is of international interest. The scarp is exceptionally well-preserved due to the extensive calcrete/silcrete cementation. In areas where this cementation is reduced or absent the scarp is more diffuse, as expected for a feature formed by one or more paleoearthquakes. The exceptional preservation aids comparison with data sets based on scarps which have formed more recently. Our analysis is based on a high-resolution digital elevation model of the Hebron Fault scarp in southern Namibia using pan-sharpened Worldview-3 satellite stereophotos (0.31 m resolution). We make scarp height measurements at 160 locations providing improved estimates of the average displacement (5.9 m), maximum displacement (10.1 m), and the minimum fault length (45 km). No consistent evidence of lateral displacements in water courses or alluvial fan margins were found implying predominantly normal displacement. A newly described section in the northwest has en-echelon scarps consistent with a component of strike-slip motion that may be explained by its difference in strike from the central section. Most channels crossing the fault show a single knick-point. The displacement varies smoothly as it crosses a number of different generations of alluvial fan surfaces. No evidence of a multiscarp or a composite scarp were observed. We have therefore found no evidence for a mutiple-event origin for the scarp, although, this lack of evidence does not conclusively demonstrate a single-event origin. Published regressions, based on the limited data available for SCRs, suggest that the mean expected average displacement ($\bar{D}_{\rm av}$) for a faults of this length is 1.2–3.1 m implying that the scarp is likely to have formed in 2–5 events with an expected Mw = ∼7.1 though displacements in individual events may exceed these average values. Comparison with the regional geology and aeromagnetic data sets suggests that the fault reactivates a Mesoproterozoic ductile structure, the Nam Shear Zone, and that the location, orientation and segmentation of the scarp is controlled by the alignment of pre-existing structurally weak zones with the present-day stress regime. The fault has undergone repeated brittle reactivation, accumulating ∼110 m of vertical offset since the deposition of the Ediacaran-to-Cambrian Nama Group. This is less than expected from global compilations of total displacement and fault length data, suggesting that the fault rapidly attained its current length by recruiting an existing weak zone and is expected to accumulate displacement at a relatively constant length in the future.

Additional file 18. Table S7. Number of samples allocated for each country, and number of samples collected.