Search

Convex, soil-covered hillslopes are ubiquitous in various tectonic and climatic settings and their morphologic characteristics can be significantly altered by dust flux and chemical weathering. Carbonate hillslopes across the Eastern Mediterranean display a classic convex morphology despite high rates of dust deposition, which are apparently similar in magnitude to denudation rates and despite a highly soluble bedrock lithology. These high rates of dust flux and bedrock dissolution result in soil composition which is strikingly different from the underlying bedrock. In this study we apply a modified regolith mass balance equation which includes dust input and chemical depletion and utilize a combination of field work and geochemical methods (immobile and major elements, XRD) to estimate the fraction of dust-derived materials in the soil and the fraction of the soil that was lost via dissolution. Soil and bedrock were sampled at 7 Eastern Mediterranean study sites, across a prominent north-to-south gradient in both precipitation (250 to 900 mm yr−1) and dust flux (150 to 40 g m−2 yr−1) and compared with dust composition. Our results indicate that the dust fraction in the soil correlates with modern measurements of dust deposition rates and decrease from nearly 100% of the 2 mm) indicating that mechanical weathering of the underlying bedrock contributes to regolith formation and plays a role in shaping carbonate hillslopes. Using a commonly used soil transport model, we show that the observed dust fraction and chemical weathering can potentially account for a 50% change in hillslope curvature. Furthermore, the predicted steady state hilltop curvature, based on our results, fits well the observed curvature based on high-resolution LiDAR-derived topographic data. Our results highlight the potential importance of dust and chemical weathering in soil production formulations and hillslope evolution models and we propose that these contributors to soil mass balance could also be relevant for silicate terrain. In addition, we also demonstrate that the source material of Mediterranean soils varies with environmental factors such as rainfall, dust deposition rates and bedrock mechanical properties.

Quaternary loess covers desert margins and vast areas of the Negev, southern Israel. The Negev loess is among the best-studied desert loess, with research going back to the early 20th century. The contrast between carbonate rocks of the Negev and its silicate-rich coarse-silt loess allows determining the loess sources, learning the synoptic-scale paleoclimatology, and exploring processes of coarse silt formation. Here, we present an overview of new perspectives on the origins and climatic significance of the Negev loess, expand on how (a) coarse silts affected soils farther downwind, and (b) how the loess has now turned into an active dust source.The sources of the Negev loess are the (a) distal Sahara and Arabia delivering fine silts and clays, transported over thousands of kilometers, and (b) proximal sand dunes in Sinai and Negev, advancing and concurrently supplying the coarse silts to the loess accretion through eolian abrasion of sand grains. It was found that the coarse silts which compose the majority of the loess, commenced during the late middle Pleistocene – early late Pleistocene, coeval with the appearance of the advancing Sinai/Negev sand dunes and the first coarse silt accretion in regional soils; The main loess formation episode is ~95-10 ka, when the dunes appeared in the Negev. Within the loess, the dust mass accumulations rates (MAR), and consequently, soil formation rates, spatiotemporally vary according to specific site location and distance relative to the proximal sources. With increasing distance beyond the loess zone, both dust MARs and grain size gradually decrease; thus, whereas Mediterranean mountains located in central Israel, tens of kilometers downwind the loess, exhibit thick soils on top of the carbonate bedrock, the even wetter regions in northern Israel, located hundreds kilometers away from the loess, exhibit only thin soils. Thus, in Mediterranean regions located at the desert fringe, coarse silt influx is one of the main factors in determining the environmental sustainability, rather than only the precipitation amount.During the Holocene, dust MARs in the Negev were much lower than late Pleistocene ones, and loess was not formed. Recently, the Negev loess became a prime source of dust mainly due to anthropogenic interferences, contributing to the regional dust cycle, and thus, at present the loess zone is a dust source rather than a dust sink. Today, the Negev loess is a non-replenishable natural resource that is slowly eroding and disappearing from the landscape.

The present study sought to quantitatively characterize the live and dead benthic foraminifera communities of the deep southeastern Levantine basin of the Mediterranean Sea (33.4o–31.7 oN, 31.3o–34.9 oE; 100–1900 m water depth) and their relationships to environmental conditions. Box corer samples were collected at 50 sites between June and July 2013. The foraminiferal macrofauna (> 250 µm) were enumerated and identified (76% to the species level). Six live foraminiferal assemblages were identified, inhabiting six biotopes, the shelf margin (SM), two upper continental slopes (UCS1 and UCS2), the lower continental slope (LCS), the eastern bathyal plain (EBP) and the western bathyal plain (WBP). The dead communities were divided into four biotopes, generally compatible with the live ones, excluding the UCS2 and the EBP. The foraminiferal density in the various live biotopes was relatively stable across the studied area, excluding the UCS2 and EBP, unlike the density of the dead shells, which increased with depth. The number of taxa per biotope was estimated by rarefaction curves and compared to the observed numbers, with a decreasing number of live taxa with water depth. The alpha-diversity, which was evaluated in relation to the number of sampled individuals, reached an asymptote in all biotopes, with very low values in the WBP. The within-biotope heterogeneity was evaluated by the average Chao-Sorensen similarity index and by a beta-diversity index (exp(gamma diversity) - exp(alpha diversity)), revealing variable heterogeneities in both assemblages. Water depth, sediment grain size mode, CaCO3 (wt%), and clay fraction (wt%) were jointly but feebly correlated with live faunal composition.

We quantify the volumetric erosion of Israel's actively retreating Mediterranean coastal cliffs between 2006 and 2015 with airborne LiDAR. Our results reveal annual sand contribution of ~ 45,000 m3 from the coastal cliffs into the Nile's littoral cell (NLC), which amounts to ~ 50% of the annual long-shore sand transport previously measured at the northern termination of the NLC. Accordingly, we find that implementation of cliff-retreat mitigation engineering efforts planned for Israel's coastline can lead to a sand deficit in the NLC that may result in increased beach erosion.

The present study sought to quantify the infauna and environmental characteristics of the deep SE Levantine Basin, Mediterranean Sea (33.4–31.7 N, 31.3–34.9E; 100–1900 m water depth). Box corer samples were collected at 50 sites in June–July 2013. The infauna (>250 μm) were enumerated and identified to the lowest possible taxonomic level (~37 % to the species level). Three faunal assemblages were identified, inhabiting three biotopes, the shelf margin (SM), the continental slope (CS) and the bathyal plain (BP). The within-biotope heterogeneity was evaluated by the average Chao-Sorensen similarity index and the beta diversity (exp(gamma diversity)—exp(alpha diversity)), revealing values of 0.64–0.7 and 1.73–2.77, respectively, upon applying the pooled bathyal plain samples. The corresponding non-pooled samples revealed higher heterogeneity, with values of 0.26 and 6.27, respectively, likely due to insufficient sampling. The infaunal density in the various biotopes (geometric mean 59–2220 ind m− 2) exhibited a logarithmic decline with water depth. The estimated number of taxa per biotope was calculated by rarefaction analysis in relation to the sampled area and the number of sampled individuals, resulting in 203 (sampled area)−206 (number of individuals) (SM), 170–163 (CS) and 144–130 (BP) taxa. The rarified alpha diversity in relation to the sampled area revealed decreasing values toward the deeper biotopes. However, similar rarified alpha diversities were found in all the biotopes in relation to the number of sampled individuals. Water depth, sediment grain size mode, CaCO3%, and clay% were jointly correlated with faunal composition; water depth provided the single strongest correlate.

Soil thickness and soil texture, and their spatial variability at hillslope scales, are important inputs for hydrologic models. Recent studies have demonstrated that mechanistic models can accurately predict the spatial distribution of soil thickness in areas where soil thickness varies gradually along hillslope profiles. To date, however, these models have not been tested in arid regions, where soils are often thin and highly variable at small scales (i.e., 1–10 m) and where the influence of aeolian accretion on soil thickness and soil texture may be significant. In addition, most of the data available for the fraction of the soil derived from aeolian deposition (which can serve as a proxy for soil texture) originate from soils developed on stable depositional landforms; data for aeolian fractions from upland soils are scarce. In this study, we developed and tested a numerical model for the prediction of thickness and aeolian fraction of soils in arid upland areas. The model assumes a long-term balance between the rates of soil production from bedrock, aeolian accretion, and soil erosion. Rates of soil production are quantified in the model using the exponential and humped soil production functions, and soil erosion rates are quantified using the nonlinear depth- and slope-dependent transport functions, assuming that only the upper soil horizons (A + B) are capable of transport. The rate of aeolian deposition is assumed to be spatially uniform. We calibrated the three free parameters of the model at a site in the Mojave Desert with a granite lithology using a combination of 1) field-measured data for soil thickness and 2) estimation of the aeolian fraction in the soil using laboratory analysis of immobile element concentrations. We validated the model results in three nearby sites using a combination of measured soil thickness in soil pits and the presence/absence of soil, and laboratory analysis of the aeolian fraction of soil. The study area is characterized by generally thin soils (

During the past three decades, the U.S. armed forces have been called on repeatedly to operate in the deserts of the Middle East and southwest Asia. Avoiding locations susceptible to extreme dust emissions and other terrain-related hazards requires the ability to predict soil and terrain conditions, often from limited information and under dynamic environmental conditions. This paper reports the approach used to develop an integrated, predictive tool for forecasting terrain conditions to support military operations in desert environments at strategic, operational, and tactical scales. The technical approach relies on the systematic integration of desert landform parameters in geomorphic models for predicting terrain conditions. This integrated effort is performed in a geographic information system (GIS) framework using expert-based analysis of airborne and spaceborne imagery to identify terrain elements. Advances in earth science research have established that unique, predictable relations exist among landscape position, soils, vegetation, and geology. Furthermore, new instrumentation allows the collection of a wide range of environmental information to characterize surface and subsurface conditions. By integrating models and methods from geomorphology, soil science, climatology, and atmospheric science with remote sensing and other technologies, a predictive model can be developed to support military operations.

Jerusalem was hit by earthquakes several times in its history, in the course of which none of the holy sites of the three main faiths of the western world escaped damage. Intensities of the last ML 6.2, July 11, 1927 Dead Sea earthquake, reached MSK VIII in the Old City of Jerusalem and the surrounding villages. As future strong earthquakes are inevitable, the need for the evaluation of earthquake-related hazards is obvious. Only general geotechnical properties of the section exposed in the mountainous area of Jerusalem are available; therefore, the hazard assessment was conducted from a geological perspective. The hazards identified in this study are: (1) amplification of seismic acceleration due to soft rock and soil conditions; (2) amplification due to mountainous topography; (3) dynamic instability of natural slopes; and (4) potential failure of slopes that have undergone engineering development and were weakened due to damaging, steepening, overloading, and wetting beyond their natural state. We formulated relative grades of vulnerability for each of the hazards and delineated the zones that require further specific investigation. For practical use we constructed a summary map that combines the different hazard categories. Looking at the summary map, the ground at the central N–S axis zone across Jerusalem is the least vulnerable. The bedrock there is mostly hard carbonate, the topography is mild, and thus only the alluvial cover, if thicker than 3 m, should be considered sensitive. Yet although the natural hazard in this area is limited, the risk should not be underrated. Much of the city lies there, including buildings constructed before antiseismic codes were regulated, and traditional engineering practice should not be taken for granted as antiseismic proof either. Eastwards, the shear wave velocity (Vs) contrast between the hard and soft rocks as well as the notable topography in places, impose the potential for amplification. Slopes, either naturally or artificially cutting into the soft chalk, may expose the area to dynamic instability; thus, the ongoing extensive development of the city in this direction should certainly take into account all of this. West of the central axis, the potential of failure of both steep natural and urbanized slopes appears. Being a plausible direction for future urban expansion, these areas specifically call for careful environmental and engineering planning. For engineering purposes, however, a specific site investigation is still necessary. Nevertheless, the summary map established in this study sets up for Jerusalem, for the first time, a practical tool for environmental and municipal planning, emergency response planning, and civil protection.

More than a thousand sinkholes have developed along the western coast of the Dead Sea since the early 1980s, more than 75% of them since 1997, all occurring within a narrow strip 60 km long and

Mapping and dating of arid and semi-arid alluvial fans are of great importance in many Quaternary studies. Yet the most common mapping method of these features is based on visual, qualitative interpretation of air-photos. In this study we examine the feasibility of mapping arid alluvial surfaces by using airborne hyperspectral reflective remote sensing methodology. This technique was tested on Late Pleistocene to Holocene alluvial fan surfaces located in the hyperarid southern Arava valley, Israel. Results of spectral field measurements showed that the surface reflectance is controlled by two main surficial processes, which are used as relative age criteria: the degree of desert pavement development (gravel coverage %) controls the absorption feature depths, while the rock coating development influences significantly the overall reflectance of the surface, but its effect on the absorption feature depths is limited. We show that as the percent of the surface covered by gravels increases, the absorption feature depth of the common gravels, in this case carbonate at 2.33 μm, increases as well; whereas the absorption features depth of the fine particle in-between the gravels, decrease (hydroxyl and ferric absorption features at 2.21 μm, and 0.87 μm, respectively), as the fines are removed from the surface. Using these correlations we were able to map the surface gravel coverage (%) on the entire alluvial fan, by calculating the gravel coverage (%) in each pixel of the hyperspectral image. The prediction of gravel coverage (%) is with accuracy of ± 15% (e.g. gravel coverage of 50% can be predicted to be 35% to 65%). Using extensive accuracy assessment data, we show that the spectral based mapping maintained high accuracy degree ( R 2 = 0.57 to 0.83). The quantitative methodology developed in this study for mapping alluvial surfaces can be adapted for other surfaces and piedmonts throughout the arid regions of the world.

Activities of 26 Al and 10 Be in five chert clasts sampled from two beach ridges of late Pleistocene Lake Lisan, precursor of the Dead Sea in southern Israel, indicate low rates of chert bedrock erosion and complex exposure, burial, and by inference, transport histories. The chert clasts were derived from the Senonian Mishash Formation, a chert-bearing chalk, which is widely exposed in the Nahal Zin drainage basin, the drainage system that supplied most of the material to the beach ridges. Simple exposure ages, assuming only exposure at the beach ridge sampling sites, range from 35 to 354 ky; using the ratio 26 Al/ 10 Be, total clast histories range from 0Ð46 to 4Ð3 My, unrelated to the clasts’ current position and exposure period on the late Pleistocene beach ridges, 160–177 m below sea level. Optically stimulated luminescence dating of fine sediments from the same and nearby beach ridges yielded ages of 20Ð0 s 1Ð4 ka and 36Ð1 s 3Ð3 ka. These ages are supported by the degree of soil development on the beach ridges and correspond well with previously determined ages of Lake Lisan, which suggest that the lake reached its highest stand around 27 000 cal. years BP. If the clasts were exposed only once and than buried beyond the range of significant cosmogenic nuclide production, then the minimum initial exposure and the total burial times before delivery to the beach ridge are in the ranges 50–1300 ky and 390–3130 ky respectively. Alternatively, the initial cosmogenic dosing could have occurred during steady erosion of the source bedrock. Back calculating such rates of rock erosion suggests values between 0Ð4 and 12 m My � 1 .T he relatively long burial periods indicate extended sediment storage as colluvium on slopes and/or as alluvial deposits in river terraces. Some clasts may have been stored for long periods in abandoned Pliocene and early Pleistocene routes of Nahal Zin to the Mediterranean before being transported again back into the Nahal Zin drainage system and washed on to the shores of Lake Lisan during the late Pleistocene. Copyright  2003 John Wiley & Sons, Ltd.

The goal of this project was to develop an integrated, predictive tool for forecasting desert terrain conditions (soils, vegetation, dust emission potential, trafficability) to support military activities in desert environments. Results have led to the development of multiple approaches to utilize basic terrain data, including space borne and airborne remote-sensing data and imagery, to rapidly predict surface and subsurface terrain conditions over a wide range of scales. During FY2012, progress was made in the following areas: 1. Empirical research to directly study the impact of military vehicle activity on desert soils, and the changes in soil and surface structure that occur with increasing levels of use; 2. Ongoing research to further examine the sources of dust in Israel; 3. Further development of new more automated approaches for landform mapping, to offer faster and more objective alternatives to the standard expert-based methods; 4. Further development and application of soft computing methods for modeling dust emission potential and other soil properties on desert landforms; 5. Ongoing application of developed predictive mapping techniques, including creating maps of: a) salt-rich dust content for the entire country of Afghanistan; and b) PM10 dust emission flux from undisturbed surfaces across all USCENTCOM (U.S. Central Command) countries.

[1] Most wind erosion studies that characterize dust emission potential measure particulate matter smaller than 10 mm (PM10) for air quality purposes or atmospheric modeling. Because the PM10 size fraction is only a portion of the total range of fine‐grained particles potentially emitted from desert landforms, we modified the miniature Portable In Situ Wind Erosion Lab (PI‐SWERL) by adding a new instrument to measure total suspended particulate matter (TSP). The modified PI‐SWERL is capable of measuring TSP with diameters

Over the past several years, the coastal area around the declining Dead Sea has undergone a catastrophic collapse. One of the major expressions of this process is the sudden appearance of hundreds of collapse sinkholes, causing a severe threat to the future of this region. Here we review results and inferences obtained from a multidisciplinary research conducted since 1999. Observations were obtained by geological mapping, aerial photographs, drilling, groundwater geochemistry, seismic refraction and refl ection, and satellite radar interferometry. The suggested model for the formation of the Dead Sea sinkholes is based on the following observations: (1) presence of a thick salt layer (or layers) at depths between 20 and 50 m (depth of layer top), and sandwiched between aquiclude layers of clay and silt; (2) identifi cation of cavities within the salt layer in sinkhole sites; (3) presence of water undersaturated with respect to halite in aquifers confi ned beneath the salt layer; (4) composition of the groundwater in the salt layer that indicates salt dissolution; (5) association between sinkhole sites and land subsidence; and (6) formation of sinkholes along and above buried faults. These observations combine to suggest that the primary cause of sinkhole formation is dissolution of the salt layer by undersaturated groundwater. The interface between the Dead Sea brine and this groundwater migrated eastward due to the Dead Sea decline. Undersaturated water accessed the salt layer via faults that cut through the soft aquiclude layers. The opening of these conduit-faults is likely due to differential compaction of the aquiclude layers, explaining the correlation between the land subsidence and sinkhole sites. It appears that the decline of the Dead Sea level affects the formation of sinkholes in three ways: (1) opening the way to eastward migration of the fresh-saline water interface and thus to undersaturated groundwater, (2) generating differential compaction of fi ne-grained sediments, and (3) destabilization of underground cavities, which catalyzes their collapse.

[1] The Dead Sea (DS) pull-apart basin is one of the more seismically active segments of the DS Transform plate boundary. In the last decade, hundreds of collapse-sinkholes have been formed along the DS coastlines in Israel and Jordan, causing severe damage to the regional infrastructure. The formation of these sinkholes is attributed to the dissolution of a buried salt layer by fresh groundwater due to the drop of the DS and the associated groundwater levels. Here we show that the sinkhole distribution, combined with gradual land subsidence measured by radar interferometry (InSAR) track young fault systems suspected as active, concealed within the fill of the DS rift. This notion is supported by (1) sinkholes clustering along discrete lineaments with a striking trend similarity to that of the exposed rift-margin faults; (2) prominent discontinuities in seismic reflection profiles offsetting young sediments (several kyrs old) below sinkhole lines, and (3) straight boundaries of gradual subsidence features that coincide with or parallel sinkhole lines. Combined, the sinkhole lineaments and the InSAR measurements reveal a zigzag pattern of buried faults within the DS rift fill.