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During the 5th and 6th centuries, the economic hinterland of the city of Gaza encompassed a network of settlements that supplied the city with agricultural produce. Water was collected in underground cisterns from rooftops and courtyards. While almost nothing remained of the above-ground structures since the settlements collapsed, soil erosion exposed these cisterns, which now serve as well-preserved indicators of the location and levels of the houses - that supplied the water. The study examines to what extent the land abandonment in the late Byzantine - early Islamic period resulted in denudation and soil property changes. We hypothesize that the abandonment of settlements and agriculture intensified soil erosion and amplified gully development. Approximately 140 cisterns were mapped in the study area, mainly north of the ephemeral Nahal Gerar stream. The height of the cisterns above the ground was used to calculate the denudation rate (DR) since abandonment. Findings indicate that over relatively flat terrains (1–5 %), cisterns protrude 0.5–1.2 m above the surface. Considering abandonment in the 6th or 11th century, DR was calculated as 0.35–0.85 mm/yr or 0.5–1.2 mm/yr, respectively. Over steeper slopes (10–12 %), along river banks and incised gullies, extensive bank erosion occurred, leading to the exposure of cisterns up to 2.5 m; DR = 1.8 to 2.5 mm/yr, depending on the abandonment time. The settlements' distribution and the surface topography directly correlate: in settled areas, Terrain Roughness Index (TRI) values are higher compared to other areas with the same lithology and rainfall amount. Following abandonment, decaying houses resulted in the complete disintegration of mud bricks, increasing the proportion of fine soil fractions. Cisterns acted as sedimentation basins, trapping surface-derived sediments and debris, including degraded brick material. This process influenced the mechanical composition of soils, affecting soil erosion and land degradation. [Display omitted] • Water cisterns serve as well-preserved indicators of the surface level of Byzantine houses. • Land abandonment since the Byzantine period causes both soil erosion and soil accumulation. • Loess denudation rate at 1–5 % slope = 0.35–1.2 mm/yr; at 10–12 % slope = 1.8–2.5 mm/yr. • Decaying houses resulted in the disintegration of mud bricks, increasing the fine soil fractions. [ABSTRACT FROM AUTHOR]

Continuous sediment supply in the Aka-kuzure landslide scar, in the tectonically active alpine Southern Japanese Alps, was investigated using airborne light detection and ranging data in 2000, 2003, 2007 and 2012. In addition, we focused on the spatial variability of denudation patterns based on topographical analyses using DEMs. Denudation volume for the past 12 years reached about 10 6  m 3 and mean annual denudation rate ranged from 0.25 to 0.31 m/yr. Topographical analyses revealed that sediment supply in the scar consists of a combination of two denudation types, sporadic-deep and wide-thin. These denudation types have different roles in the topographical development of the landslide scar. Sporadic-deep type supplies less volume than wide-thin type but still contributes to channel development, as it mainly occurs on lower-order streams and tends to change the convex slope into a concave slope. In contrast, although denudation depth of the wide-thin type is thin, the area affected by this type extends to the whole landslide scar. Consequently, the wide-thin type accounts for most of the total volume lost, for which detachment by frost shattering is suggested as an important role. [ABSTRACT FROM AUTHOR]

This study characterizes significant changes in denudation and disasters in mountainous areas induced in the humid Chengdu Longmenshan region by the Wenchuan Earthquake in 2008. A study focusing on the Longxi-Baisha River Basin was conducted to investigate the amount of denudation triggered by specific flash flood and debris flow events in 2009–2014. The following results were obtained through a comparison of pre-seismic regional denudation rates and denudation characteristics of other seismically active mountain regions. (1) Regional denudation processes occurred in a wave-like process of initial increase then decline, with a peak exhibiting a hyperbolic attenuation trend. This trend indicates that the denudation rate in the Chengdu Longmenshan region is expected to return to the pre-seismic rate of 0.3 mm a −1 after 81 years. In 22 years after the earthquake (Year 2030), debris flow disasters are expected to be rare. (2) Disasters increased significantly in the Chengdu Longmenshan region after the Wenchuan earthquake, with an average of 29.5 people missing or dead per year (22 times greater than the pre-earthquake rate) and average economic losses of 192 million Yuan per year (1.6 times greater than the pre-earthquake rate). (3) The denudation process was jointly controlled by the quantities of loose solid material and precipitation after the Wenchuan earthquake. The amount of loose solid material influenced the extent of denudation, while vegetation coverage rates and soil consolidation determined the overall denudation trend in the region, and changes in precipitation led to denudation fluctuations. (4) The results can be used to analyze the relationship between the potential flash flood-debris flow disasters after earthquakes in the ancient Shu kingdom and changes in historical social settlements. The results can also be used to predict denudation processes and disaster risks from earthquakes in humid mountainous regions around the world, such as the southern slope of the Himalayas, Japan and the Taiwan mountains. [ABSTRACT FROM AUTHOR]

Mountains dominate global denudation fluxes of solutes to the oceans despite being only a modest portion of the Earth's surface. Determining the flux of material exhumed from mountains as dissolved load, however, requires careful measurement of ionic concentrations and discharge that may be hard to obtain. We reconstruct the dissolved load and total dissolved solids yield from pre-existing discharge measurements and 32-years on monthly water quality sampling in a headwater catchment in the Southern Alps/Ka Tiritiri o te Moana, New Zealand. The dissolved weathering yield of the Haast/Awarua River for 1971–2020 was 218 ± 48 t km−2 a−1. The flux of dissolved material from the mountain catchment has a seasonal signal, with higher TDS concentrations during winter, but greater chemical weathering yields during summer. Hydrographic behaviour is an important control of weathering yields with 70 % of dissolved load being transported during event flow. Variations in chemical weathering yields are sensitive to changes in stream flow associated with broader climate oscillations, which will have a direct effect on estimations of chemical weathering rates since dissolved flux is strongly correlated to changes in stream flow. • Flow-weighted approaches to estimating dissolved flux are consistent between hourly, daily, and monthly datasets • Seasonal variations of ionic load in rivers are a source of uncertainty in estimations of dissolved load • Event flow mobilised 70% of the dissolved load and is an important component to determining annual fluxes • The mean annual dissolved load for the Haast/Awarua River reconstructed from flow records is 218 ± 48 t km−2 a−1 • Long-term oscillations in rainfall distort long-term trends in dissolved flux calculations [ABSTRACT FROM AUTHOR]

Trees have the ability to distinctly determine soil evolution and hillslope processes through mechanical soil disturbances such as tree uprooting. Recent findings have resulted in new biogeomorphic state transition models for old-growth forests in the temperate climate zone. The situation in tropical forests, however, is mostly unknown. Here, we focus on determining short- (decades) and long-term (millennia) soil erosion rates and the biogeomorphic role of trees on hillslope dynamics in the species-rich Wanang primeval tropical forest, Papua New Guinea. We hypothesized that trees play a significant role in hillslope dynamics on a background of powerful soil erosion dominated by abiotic factors, and that this role has potentially intensified over the last decades. The long-term soil erosion was assessed using the meteoric 10Be levels in three soil profiles along the whole depth gradient along with one natural outcrop. The recent soil erosion rate was determined using 239+240Pu levels in the uppermost soil layers. The specific role of trees in hillslope processes was evaluated based on repeated tree censuses of 65,535 tree individuals, calculating the tree mortality rate and modeling the soil volume affected by uprooted trees and by the in situ decay of the root systems of broken trees. Soil erosion was 6.25 m3 ha−1 yr−1 over the long term and indeed did increase during the last decades. While this rate was significantly affected by trees, they were not the main factor, with circa 0.95 m3 ha−1 influenced annually by uprooting, and an additional 0.61 m3 ha−1 by the in situ decay of root systems. These results reflect a forest ecosystem that is currently in the biogeomorphic stage of biotic/abiotic feedbacks. [Display omitted] • Erosion in a primary tropical forest was 6.3 m3 ha−1 yr−1 over the last thousands of years. • The erosion rate has increased in the last decades in primary tropical forest. • Individual trees significantly affected hillslope processes and pedocomplexity. • The forest ecosystem is in the biogeomorphic stage of biotic/abiotic feedbacks. [ABSTRACT FROM AUTHOR]

Erosion rates of tropical landscapes are poorly known. Using measurements of in situ-produced 10 Be in quartz extracted from river and landslide sediment samples, we calculate long-term erosion rates for many physiographic regions of Panama. We collected river sediment samples from a wide variety of watersheds ( n = 35), and then quantified 24 landscape-scale variables (physiographic, climatic, seismic, geologic, and land-use proxies) for each watershed before determining the relationship between these variables and long-term erosion rates using linear regression, multiple regression, and analysis of variance (ANOVA). We also used grain-size-specific 10 Be analysis to infer the effect of landslides on the concentration of 10 Be in fluvial sediment and thus on erosion rates. Cosmogenic 10 Be-inferred, background erosion rates in Panama range from 26 to 595 m My − 1 , with an arithmetic average of 201 m My − 1 , and an area-weighted average of 144 m My − 1 . The strongest and most significant relationship in the dataset was between erosion rate and silicate weathering rate, the mass of material leaving the basin in solution. None of the topographic variables showed a significant relationship with erosion rate at the 95% significance level; we observed weak but significant correlation between erosion rates and several climatic variables related to precipitation and temperature. On average, erosion rates in Panama are higher than other cosmogenically-derived erosion rates in tropical climates including those from Puerto Rico, Madagascar, Australia and Sri Lanka, likely the result of Panama's active tectonic setting and thus high rates of seismicity and uplift. Contemporary sediment yield and cosmogenically-derived erosion rates for three of the rivers we studied are similar, suggesting that human activities are not increasing sediment yield above long-term erosion rate averages in Panama. 10 Be concentration is inversely proportional to grain size in landslide and fluvial samples from Panama; finer grain sizes from landslide material have lower 10 Be concentration than fine-grained fluvial sediment. Large grains from both landslide and stream sediments have similarly low 10 Be concentrations. These data suggest that fluvial gravel is delivered to the channel by landslides whereas sand is preferentially delivered by soil creep and bank collapse. Furthermore, the difference in 10 Be concentration in sand-sized material delivered by soil creep and that delivered by landsliding suggests that the frequency and intensity of landslides influence basin scale erosion rates. [ABSTRACT FROM AUTHOR]

Rock tablets of known weight were buried in the soil of a karst region in Central Spain to evaluate the carbonate weathering during a period of a year. The experiment was conducted at two different soil depths: 5–10 and 50–55 cm from the surface. The parental rock used in the experiment is composed of dolomite and magnesite with variable proportion of accessory minerals and minor elements. Soil mineral and chemical composition as well as its texture was also characterized. Meteorological conditions at the site together with temperature and CO 2 in both soil levels were monitored. Sets of tablets were retrieved after 6 and 12 months of the start of the experiment to account for seasonal weathering. Different lithologies do not exhibit significant differences in weathering, although a large inter-sample variability is attributed to variable size and distribution of the porosity. Results show an enhanced weathering during the wet and cold season that accounts for 78 ± 1% of the total annual weathering. Rock tablets examined under scanning electron microscopy prior and after exposure to natural environment show that most of the material lost occurred along cracks, edges or large pores. Although dissolution is a common process, most of the weathering is due to crystal detachment. Rock tablets at the depth of 5–10 cm were weathered 68 ± 1% more than those set at 50–55 cm from the surface. Higher soil moisture and concentration of CO 2 were found deeper in the soil, which likely enhanced the dissolution of carbonate. However, physical weathering dominated weight loss of rock tablets at both soil depths; especially at the 5–10 cm level where soil thermal and moisture cycles were more frequent and greater. Denudation rate calculated from the 12 months set provides values of 2.48 ± 1.07 μm/yr and 1.75 ± 0.66 μm/yr at the depths of 5–10 and 50–55 cm, respectively. Since the conditions at the average contact between soil and bedrock are similar to those at the 50–55 cm depth, we consider that this is a more reliable denudation rate for the studied location during the studied period. The calculated weathering rate suggests that denudation has a limited contribution to the thinning of bedrock over caves at this site. Therefore, we consider that the formation of unroofed caves in this region most likely results from the thinning of bedrock cover over caves due to collapse of blocks from their ceilings. [ABSTRACT FROM AUTHOR]

Landsliding resulting from large earthquakes in mountainous terrain presents a substantial hazard and plays an important role in the evolution of mountain ranges. However estimating the scale and effect of landsliding from an individual earthquake prior to its occurrence is difficult. This study presents first order estimates of the scale and effects of coseismic landsliding resulting from a plate boundary earthquake in the South Island of New Zealand. We model an M w 8.0 earthquake on the Alpine Fault, which has produced large ( M 7.8–8.2) earthquakes every 329 ± 68 years over the last 8 ka, with the last earthquake ~ 300 years ago. We suggest that such an earthquake could produce ~ 50,000 ± 20,000 landslides at average densities of 2–9 landslides km − 2 in the area of most intense landsliding. Between 50% and 90% are expected to occur in a 7000 km 2 zone between the fault and the main divide of the Southern Alps. Total landslide volume is estimated to be 0.81 + 0.87/− 0.55 km 3 . In major northern and southern river catchments, total landslide volume is equivalent to up to a century of present-day aseismic denudation measured from suspended sediment yields. This suggests that earthquakes occurring at century-timescales are a major driver of erosion in these regions. In the central Southern Alps, coseismic denudation is equivalent to less than a decade of aseismic denudation, suggesting precipitation and uplift dominate denudation processes. Nevertheless, the estimated scale of coseismic landsliding is considered to be a substantial hazard throughout the entire Southern Alps and is likely to present a substantial issue for post-earthquake response and recovery. [ABSTRACT FROM AUTHOR]

Extensive tracts of low-gradient topography in steep mountain ranges, either forming rangetop plateaus or terraced pediments on range flanks, are widely distributed in mountain belts around the world. Before the advent of plate tectonics, such populations of planar landforms were interpreted as vestiges of a post-orogenic raised peneplain, i.e., a low-gradient land surface resulting from the decay, during long intervals of base-level stability, of a previous mountain range that was subsequently raised once again to great elevations—thus forming a new mountain range. This two-stage model has been challenged by theories that advocate continuity in tectonic processes and more gradual changes in base level, and thus expect a more immediate and proportionate response of geomorphic systems. Here we present a global survey of erosion surfaces in mountain ranges and put existing theories and empirical evidence into a broad perspective calling for further research into the rates and regimes of long-term mountain evolution. The resulting library of case studies provides opportunities for comparative analysis and helps to classify the landform mosaics that are likely to arise from the interplay between (i) crustal regimes, which at convergent plate margins need be neither uniform nor steady at all times; (ii) radiation-driven and gravity-driven geomorphic regimes, which are mainly determined by crustal boundary conditions and climate; and (iii) paleogeography, through which clues about base-level changes can be obtained. We examine intracratonic and plate-margin settings, with examples from thin-skinned fold belts, thick-skinned fold belts, island-arc and other subduction-related settings, and bivergent collisional orogens. Results reveal that the existence of erosion surfaces is not a simple function of geodynamic setting. Although some erosion surfaces are pre-orogenic, evidence about their predominantly post-orogenic age is supported by apatite fission-track and helium rock-cooling signatures, stratigraphic age-bracketing, stream channel gradient patterns, and other direct or indirect dating criteria. It follows that many portions of mountain belts undergo unsteady, nonuniform post-orogenic landscape evolution trajectories, with intermittent opportunities for relief reduction. The resulting erosion surfaces remain preserved as signatures of transient landscape evolution regimes. We find that (i) occurrences of planar topography form populations of discrete, insular landscape units, only some of which could be interpreted as fragments of a fluvially dissected, and/or tectonically fragmented, regional peneplain. (ii) The post-orogenic time required for achieving advanced stages of relief reduction is variable, ranging from 3 to 70 Ma. (iii) Partly depending on whether the adjacent sedimentary basins were over- or underfilled, some erosion surfaces may have been controlled by raised base levels and may thus have formed at high elevations; however, in many cases they were disconnected from marine base levels by rapid surface uplift, thus acquiring their elevated positions in recent time. In some cases, subcrustal processes such as asthenospheric anomalies, and/or lithospheric slab tear or breakoff, explain extremely rapid, regional post-orogenic uplift. (iv) Overall, the conditions for achieving surface preservation in steep and tectonically active terrain are predictable but also quite varied and contingent on context. [ABSTRACT FROM AUTHOR]

Western Bhutan provides an ideal setting to understand the interplay between uplift, erosion, and fluvial sediment transport in an active mountain environment. Using in situ -produced 10 Be (49 samples) and 26 Al (5 samples) in fluvial sediment from nested catchments throughout the Puna Tsang Chhu drainage basin, we examine erosion rates in different geomorphic environments including two high-relief regions – a glacierized zone in the north and a high-rainfall zone in the south – as well as remnants of an uplifted, lower-relief paleosurface between them. The erosion rates roughly mirror this north–south zonation: lower rates (avg. 388 ± 32 m My − 1 , n = 16) prevail in the low-relief zone, roughly coinciding with lower-relief terrain where mean annual precipitation is ~ 1500 mm yr − 1 ; the highest rates (avg. 956 ± 160 m My − 1 , n = 13) are in the south (27.10°–27.35°N), where rainfall is > 4000 mm yr − 1 ; high rates (avg. 700 ± 62 m My − 1 , n = 15) also occur in the northern, glacierized region (27.70°–28.10°N). All 49 purified mineral separates used in this study contain measurable amounts of native 9 Be (up to 900 μg), violating the assumption of negligible 9 Be that is commonly made in the isotope dilution method used to quantify 10 Be. To correct for this native 9 Be, we use high precision, replicate measurements of 9 Be in each sample to calculate 10 Be concentrations from measured isotopic ratios. Neglecting native 9 Be would have led to erosion rate overestimates from <20% to >400%. The pervasive nature of 9 Be in these samples underscores the importance of quantifying the native 9 Be concentration in mineral separates used for cosmogenic 10 Be analysis. [ABSTRACT FROM AUTHOR]

Abstract: Landscape evolution in active orogenic regions is inevitably affected by the repeated strong earthquakes triggered by the corresponding active faults. However, the lack of adequate methods for the documentation and monitoring of mountain-building processes has resulted in a shortage of quantitative estimates of orogenic and eroded volumes. A strong earthquake and its associated co-seismic landslides represent a sudden pulse in landscape evolution in tectonically active areas. The 2008 Mw7.9 Wenchuan earthquake dramatically modified the topography of the Longmen Shan region. Based on topographic data before the earthquake and stereo pairs of post-earthquake remote sensing imagery, we derived pre- and post-earthquake DEMs (digital elevation models) of the three regions along the Longmen Shan Thrust Belt. By comparing the geomorphic features before and after the earthquake, we find that the Wenchuan earthquake smoothed the steep relief and caused a co-seismic uplift of the Longmen Shan region. The medium-relief regions increased; however, the high-relief regions decreased, indicating that the local relief is controlled by repeated strong earthquakes. The changed slope aspect indicates that the formation and modification of the east- and west-facing slopes are controlled by tectonic events in the Longmen Shan region, which might be associated with the regional stress field. However, the unchanged aspects of other slopes might be controlled by long-term erosion rather than tectonic events. The topographic changes, landslide volume and co-seismic uplift indicate that the greatest seismically induced denudation occurred in association with a thrust faulting mechanism and low-angle fault geometry. Our findings reveal that the local relief has been shaped by the localized, seismically induced high rate of denudation within the plateau margins, and that the formation of local relief is also related to tectonic events, especially the events that have occurred on low-angle faults. This study also indicates that the multi-temporal DEM differential method is valuable in detecting seismically induced topographic change. [Copyright &y& Elsevier]

Abstract: Southern Africa displays a high topography but paradoxically exhibits tectonic stability and low denudation rates. Here the present controls on denudation in southern Africa are investigated by comparing maximum denudation rates for Karoo dolerite surfaces in the region, determined from the abundances of cosmogenic noble gas nuclides (3He, 21Ne and 38Ar) in pyroxenes, with the predictions of a climate-dependent weathering rate model. In general, we find an excellent agreement in the value ranges of both datasets (<4m/Myr), and interpret this as evidence that present denudation in southern Africa is weathering-limited and climatically influenced due to an apparent absence of significant regional neotectonic uplift. The onset of this geodynamic coupling is unknown but may be of considerable antiquity, thus allowing for the prolonged tenure of southern Africa's inherited Cretaceous topography. [Copyright &y& Elsevier]

Abstract: Relationships between landslides and drainage network arrangement have been investigated by classical and quantitative geomorphological analysis in an intermountain valley (i.e. the upper valley of the Sinni River) of the southern Italian Apennines. The 120km2-wide test-area is characterized by very low grade metamorphic rocks (mainly shale) and associated crystalline-metamorphic rocks which underwent high exhumation and uplift rates during Quaternary times. We recognized and mapped 534 landslides through the stereoscopic interpretation of one set of 20 panchromatic aerial photographs 1:33,000 scale. Landslides were classified according to both type of movement and relative age. We detected and mapped 35 new landslides after a long rainfall period during the winter 2008–2009. The percentage of area affected by landslides (DL ) of the area has a high value (about 37%). Analysis of distribution of landslides areas within different age classes suggests that recent/present-day landslide distribution is strongly influenced by the legacy of widespread large and ancient landslides, probably generated within a different morpho-climatic setting. A quantitative geomorphological analysis of the drainage network has been performed to evaluate the influence of landslide processes on morphometric properties of the drainage network. In particular, the degree of hierarchical organization of the drainage network is assessed through the hierarchical anomaly density, a measure of the number of anomalous confluences (i.e. channels of u order not flowing in channels of order u +1) in drainage basins. On the basis of statistical relationships between morphometric indices of the drainage network and DL , we argue that the activity of more recent mass movements rather than very old landslides can act as a disturbing element within the development of the drainage network, generating anomalous confluences of the 1st order. Empirical relationships between suspended sediment yield and some geomorphic parameters of the drainage network allowed the estimation of short-term denudation rates in the study area. The comparison between uplift and denudation rates suggests that the landscape system has not reached a steady state between uplift and erosion, in which tectonic uplift can represent a disturbing element within the recent morphogenesis. On the basis of the data presented, (large) mass movements in the study area are mainly linked to the relief growth promoted by Quaternary tectonics, whereas litho-structural and morpho-climatic factors assume a minor role. [Copyright &y& Elsevier]

Abstract: Denudation processes and sediment transfer are investigated in a high-elevation, low-relief environment (eastern Altiplano, Bolivia) using 10Be, 26Al, and in situ 14C analysis in fluvial sediments. Concentrations of the long-lived nuclides 10Be and 26Al yield consistently low catchment-wide denudation rates of ~3–29mmky−1 (integrating over 21–194ky), which reflect the low geomorphic gradients and the discontinuity of fluvial transport along the eastern Altiplano margin. No significant correlation is recorded between denudation rates of individual catchments and morphological basin parameters (slope, area, elevation). This is attributed to the overall little variability in morphology. The agreement between the denudation rates and published modern sediment discharge data suggests steady landscape evolution of the eastern Altiplano from the latest Pleistocene until today. While 10Be and 26Al provide long-term estimates on sediment production, in situ cosmogenic 14C is used to trace short-term sediment storage. In situ 14C concentrations are comparatively low indicating that 14C decayed during alluvial storage over at least the past ~11–20ky. We assume storage at shallow depth (2m) and consider the influence of soil-mantled hillslopes on the in situ 14C concentration. Our results illustrate the importance of sediment storage even over short distances and demonstrate the potential of in situ 14C to study sediment routing and transfer times within drainage systems. However, this study also demonstrates that the long-lived 10Be and 26Al nuclides can provide adequate estimates on long-term denudation rates even if sediment transport is not fast but interrupted by several thousands of years of storage. [Copyright &y& Elsevier]

Abstract: The proportional contribution of low-, mid- and high magnitude rock slope failure orchestrates rock slope erosion and rockfall hazard in Alpine and Arctic environments. In this study, we compare sediment yield, geomorphic work and rock wall retreat of carbonate dissolution and five different magnitudes of rock slope failure in the steep Alpine Reintal trough valley. We combine a four-year rockfall collector measurement of 140Mg of fragmental rockfall, a 20th century scientific record of mid-magnitude rockfall as well as carbon-dating and a historical record of 15th to 19th century rock avalanche activity. The total rockfall sediment yield of 8.6 (±3.4)∗103 m3year−1 is dominated by high-magnitude rock avalanches (>106 m3: 62%) and low-magnitude debris falls (<10m3: 18%), while mid-magnitude boulder, block and cliff falls are less important. The magnitude signal contradicts studies on siliceous rocks where mid-magnitude rockfall dominates rock slope erosion. The geomorphic work released in the 17.3km2 large catchment by rockfalls (123 (±47) Wkm−2, i.e. 0.38 (±0.15) mmyear−1) and solute transport (34 (±18) Wkm−2, i.e. 0.05 (±0.03) mmyear−1) exceeds previously published Alpine values by one to multiple orders of magnitude. We hypothesise that the magnitude signal of enhanced small and high magnitude rockfall is characteristic for carbonate cliffs. The elevated porosity-related susceptibility to fragmentation and persistent carbonate dissolution along potential sliding planes are likely to favour both low- and high-magnitude rock slope failures. Here we show how the magnitude signal of rock slope failure influences rock wall retreat, geomorphic work, rockfall deposition and sediment connectivity. [Copyright &y& Elsevier]

Abstract: The work examines the timing and environmental conditions of floodplain sedimentation in the valleys of the upland Kłodnica and piedmont Osobłoga rivers in the Upper Odra River basin. A distribution of 52 14C-ages shows relatively high floodplain sedimentation at the Late Glacial–Holocene transition, more stable floodplain environments since the Early (in the Kłodnica Valley) and Middle Holocene (in the Osobłoga Valley) and a gradual increase in floodplain deposition in the Late Holocene (since <3.4kyr BP). Organic matter [OM] and mineral matter [MM] fluctuations were correlated with variables responsible for the activation of erosion (i.e. vegetation changes, human impact and hydrological events) as well as factors affecting the local record of sedimentation (i.e. valley morphology, hydrologic conditions and episodes of local erosion). A clear relationship is shown between an increase in alluviation and climate- or human-induced extension of unforested areas. The deposition of mineral-rich sediments increases rapidly during periods characterized by non-arboreal pollen values exceeding approximately 8% in pollen diagrams. On the other hand, the results obtained do not confirm significant interactions between Holocene changes in forest composition and alluviation. Despite the settlement of agrarian groups, the sedimentary record of human activity in the Osobłoga catchment is very poor during the Neolithic and early Bronze Age. A large-scale alluviation of the Osobłoga and Kłodnica valleys was initiated during the settlement of people of the Lusatian culture from the middle Bronze Age and escalated in the early Middle Ages and Modern Times. The deposition of products of soil erosion was limited to between ca. 1.9–1.2kyrBP, probably due to demographic regression during the Migration Period. Comparison of OM/MM fluctuations with phases of increased fluvial activity does not show a relationship between Holocene wetter phases and catchment sediment yield. Sedimentary episodes in the Upper Odra basin also show a low degree of correlation with the probability density curve of the 14C-ages. The results obtained in the Kłodnica and Osobłoga valleys indicate a strong to moderate correlation between the spatial distribution of the study sites and the origin of MM-rich deposits, but a weak correlation between the spatial distribution of the study sites and TOC content. Such a pattern suggests that OM/MM fluctuations relate predominantly to the changes in sediment yield, although morphological conditions have a significant impact on the capture potential of sedimentary basins during phases of alluviation. Additionally, high OM content is not a simple function of an increase in wetness of the sedimentary environment. On the other hand, hydrologically-conditioned hiatuses as well as erosion episodes impoverish the sedimentary record, complicating the consideration on the geochronology of deposits and making it difficult to calculate reliable accumulation rates. However, they do not reduce the value of OM/MM fluctuations as an indicator of alluviation events for a preserved series of sediments. [Copyright &y& Elsevier]

Abstract: We quantify spatial and temporal variations in denudation rates across the central Andean fold-thrust belt in Bolivia with particular focus on the Holocene. Measured and predicted 10Be cosmogenic radionuclide (CRN) concentrations in river sediments are used to (1) calculate catchment-averaged denudation rates from 17 basins across two transects at different latitudes, and (2) evaluate the sensitivity of Holocene climate change on the denudation history recorded by the CRN data. Estimated denudation rates vary by two orders of magnitude from 0.04 to 1.93mmyr−1 with mean values of 0.40±0.29mmyr−1 in northern Bolivia and 0.51±0.50mmyr−1 in the south. Results demonstrate no statistically significant correlation between denudation rates and morphological parameters such as relief, slope or drainage basin size. In addition, the CRN-derived denudation rates do not reflect present-day latitudinal variations in precipitation. Comparison to ∼130 previously published denudation rates calculated over long (thermochronology-derived; >106 yrs), medium (CRN-derived; 102–104 yrs), and short timescales (sediment flux-derived; 101 yrs) indicate temporal variations in denudation rates that increase between 0 and 200% over the last ∼5ka. CRN modeling results suggest that the CRN-derived denudation rates may not be fully adjusted to wetter climate conditions recorded in the central Andes since the mid-Holocene. We conclude that large spatial variability in CRN denudation may be due to local variations in tectonics (e.g. faulting), while large temporal variability in denudation may be due to temporal variations in climate. [ABSTRACT FROM AUTHOR]

Abstract: Recent work has demonstrated that glacial moraine erosion and soil mixing occur at rates high enough to influence chemical weathering processes and the determination of depositional ages. In this study, we complement previous moraine crest studies by investigating a 1.8-m-deep soil profile from the foreslope of a terminal, Bull Lake-age moraine (~140ky) in the Wind River Mountains (Wyoming, USA). Techniques applied include measurement of the grain size distribution, major element concentrations, and cosmogenic 10Be concentrations in quartz. Results suggest a 30-cm-thick moving soil layer overriding a previously eroded, mixed soil layer. Mass balance calculation based on the cosmogenic nuclide concentration in the different soil layers of the slope profile as well as a previously investigated crest profile suggests that one-third of the 30-cm-thick layer is coming from the crest area and two-thirds of the material from the eroding moraine slope. Foreslope denudation rates are 0.015 to 0.018mmy−1 based on the 10Be concentration of the lowermost samples and assuming a depositional age of 140ky. The 10Be concentration of the foreslope surface sample suggests a denudation rate of 0.020mmy−1 for the sediment source area. Analysis of major elements in a limited number of surface samples reveals that the immobile element Ti is enriched downslope, whereas more mobile elements are generally depleted downslope. The internal structure of a moraine foreslope is complex, and care must be taken in calculating moraine age and denudation rate with depth profiles. [Copyright &y& Elsevier]

Abstract: Previous studies of chemical weathering rates for soil developed on glacial moraines generally assumed little or no physical erosion of the soil surface. In this study, we investigate the influence of physical erosion on soil profile weathering rate calculations. The calculation of chemical weathering rates is based on the assumption that soil profiles represent the integrated amount of weathering since the time of moraine deposition. The weathering rate of a surface subjected to denudation is the sum of the weathering loss from the existing soil profile added to the weathering loss in the material removed by denudation, divided by the deposition age. In this study, the amount of weathered material removed since moraine deposition is calculated using the denudation rate estimated from cosmogenic nuclide data and the deposition age of the moraine. Weathering rates accounting for denudation since moraine deposition are compared to weathering rates based on the assumption of no physical erosion and on the assumption of steady-state denudation for the Type Pinedale moraine (∼21 ka) and the Bull Lake-age moraine (∼140 ka) in the Fremont Lake Area (Wind River Mountains, Wyoming, USA). The total weathering rates accounting for denudation are 8.15±1.05 g(oxide) m− 2 y− 1 for the Type Pinedale moraine and 4.78±0.89 g(oxide) m− 2 y− 1 for the Bull Lake-age moraine, which are ∼2 to 4 times higher, respectively, than weathering rates based on the assumption of no physical erosion. The weathering rates based on denudation since moraine deposition are comparable or smaller than weathering rates assuming steady-state denudation. We find the assumption of steady-state denudation is not valid in depositional landscapes with young deposition ages or slow denudation rates. The decrease in weathering rates over time between the Type Pinedale and Bull Lake-age soils that is observed in the case of no physical erosion is decreased when the influence of denudation on the total weathering rates is taken into account. Fresh unweathered material with high reactive mineral surface area is continuously provided to the surface layer by denudation diminishing the effect of decreasing weathering rate over time. [Copyright &y& Elsevier]

Abstract: The paper discusses methods and principles used to estimate dissolutional denudation rates in karst areas. Surface lowering can be measured directly by micro erosion meters or calculated from the mass loss in rock tablets exposed to dissolution in different environments. Indirect approaches are based on the measurements of solute load leaving the catchment area, geomorphological investigations and methods of cosmogenic nuclides, particularly 36Cl. Calculations based on the solute load measurements generally give higher denudation rates than direct measurements on the surface of limestone terrains. This can be explained by the fact that only about 30% of water''s dissolution potential is used on the exposed surfaces and the rest is done deeper in the fracture system. The role of endokarst dissolution is demonstrated with a denudation model of rock column where dissolution rate depends solely on the distance from the surface. The denudation rates of a uniform rock column approach maximal when the thickness of the removed rock is about twice an e-folding length for the dissolution rates. The model also gives possible mechanisms for differential denudation in regions with different infiltration intensity and fracture density. [Copyright &y& Elsevier]

Abstract: The long-term evolution of the East Greenland fjord region is investigated using geomorphological and stratigraphical evidence to: (1) assess the nature of landscape modification caused by late Cenozoic ice sheet glaciation; and (2) relate patterns of glacial landscape modification to first-order (i.e. continent-margin scale) topography and geology. Geomorphological and stratigraphical evidence demonstrates evolution of the first-order topography and incision of at least part of the present first-order fjord system by ∼55 Ma. This hypothesis is tested using apatite (U–Th)/He ages for samples from two bedrock profiles near Kong Oscar Fjord. The thermochronology supports landscape evolution before 55 Ma, followed by relative tectonic stability, because it indicates rapid denudation around the time of rifting that occurred prior to continental breakup (i.e. between ∼75 and 55 Ma). The nature of landscape modification caused by late Cenozoic glacial erosion appears to have been controlled by first-order topography and geology, with selective ice sheet erosion in areas of high-elevation Caledonian basement and apparently little glacial erosion of low-elevation Mesozoic sedimentary strata. Nevertheless, fjord morphometry demonstrates systematic evolution of the first-order fjord system from confined and overdeepened fjords in Caledonian basement to wider and disproportionately larger fjords in Mesozoic strata. The latter indicates that changes in lithological strength enabled the development of more efficient fjord morphology under full glacial conditions that may have promoted fast ice flow. [Copyright &y& Elsevier]

Abstract: The Southern Alps of New Zealand are the topographic expression of active oblique continental convergence of the Australian and Pacific plates. Despite inferred high rates of tectonic and climatic forcing, the pattern of differential uplift and erosion remains uncertain. We use a 25-m DEM to conduct a regional-scale relief analysis of a 250-km long strip of the western Southern Alps (WSA). We present a preliminary map of regional erosion and denudation by overlaying mean basin relief, a modelled stream-power erosion index, river incision rates, historic landslide denudation rates, and landslide density. The interplay between strong tectonic and climatic forcing has led to relief production that locally attains ∼2 km in major catchments, with mean values of 0.65–0.68 km. Interpolation between elevations of major catchment divides indicates potential removal of l01–103 km3, or a mean basin relief of 0.51–0.85 km in the larger catchments. Local relief and inferred river incision rates into bedrock are highest about 50–67% of the distance between the Alpine fault and the main divide. The mean regional relief variability is ±0.5 km. Local relief, valley cross-sectional area, and catchment width correlate moderately with catchment area, and also reach maximum values between the range front and the divide. Hypsometric integrals show scale dependence, and together with hypsometric curves, are insufficient to clearly differentiate between glacial and fluvial dominated basins. Mean slope angle in the WSA (ψ =30°) is lower where major longitudinal valleys and extensive ice cover occur, and may be an insensitive measure of regional relief. Modal slope angle is strikingly uniform throughout the WSA (φ =38–40°), and may record adjustment to runoff and landsliding. Both ψ and φ show non-linear relationships with elevation, which we attribute to dominant geomorphic process domains, such as fluvial processes in low-altitude valley trains, surface runoff and frequent landsliding on montane hillslopes, “relief dampening” by glaciers, and rock fall/avalanching on steep main-divide slopes. [Copyright &y& Elsevier]

Abstract: The argument in this paper is that the fundamental control on landscape evolution in erosional landscapes is weathering. The possibility of and evidence for instability in weathering at four scales is examined. The four scales are concerned with weathering processes, allocation of weathered products, the interrelations of weathering and denudation, and the topographic and isostatic responses to weathering-limited denudation (the regolith, hillslope, landscape unit, and landscape scales, respectively). The stability conditions for each model, and the circumstances under which the models themselves are relevant, are used to identify scale-related domains of stability and instability. At the regolith scale, the interactions among weathering rates, resistance, and moisture are unstable, but there are circumstances—over long timescales and where weathering is well advanced—under which the instability is irrelevant. At the hillslope scale, the system is stable when denudation is transport rather than weathering limited and where no renewal of exposure via regolith stripping occurs. At the level of landscape units, the stability model is based entirely on the mutual reinforcements of weathering and erosion. While this should generally lead to instability, the model would be stable where other, external controls of both weathering and erosion rates are stronger than the weathering–erosion feedbacks. At the broadest landscape scale, the inclusion of isostatic responses destabilizes erosion–topography–uplift relationships. Thus, if the spatial or temporal scale is such that isostatic responses are not relevant, the system may be stable. Essentially, instability is prevalent at local spatial scales at all but the longest timescales. Stability at intermediate spatial scales is contingent on whether weathering–erosion feedbacks are strong or weak, with stability being more likely at shorter and less likely at longer timescales. At the broadest spatial scales, instability is likely; although stability may be present at intermediate temporal scales if weathering–erosion feedbacks are weak. The distinction is important because stability is associated with convergent evolution whereby the effects of initial variations or disturbances are reduced over time as the landscape converges toward a stable equilibrium state. Instability, by contrast, indicates divergent evolution, increasing differentiation over time, and the persistence and growth of disturbance effects and initial variations. [Copyright &y& Elsevier]

Abstract: In recognition of the fundamental control exerted by weathering on landscape evolution and topographic development, the 35th Binghamton Geomorphology Symposium was convened under the theme of Weathering and Landscape Evolution. The papers and posters presented at the conference imparted the state-of-the-art in weathering geomorphology, tackled the issue of scale linkage in geomorphic studies and offered a vehicle for interdisciplinary communication on research into weathering and landscape evolution. The papers included in this special issue are encapsulated here under the general themes of weathering mantles, weathering and relative dating, weathering and denudation, weathering processes and controls and the ‘big picture’. [Copyright &y& Elsevier]

Water is well established as a major driver of the geomorphic change that eventually reduces mountains to lower relief landscapes. Nonetheless, within the altitudinal limits of continuous vegetation in humid climates, water is also an essential factor in slope stability. In this paper, we present results from field experiments to determine infiltration rates at forested sites in the Andes Mountains (Ecuador), the southern Appalachian Mountains (USA), and the Luquillo Mountains (Puerto Rico). Using a portable rainfall simulator–infiltrometer (all three areas), and a single ring infiltrometer (Andes), we determined infiltration rates, even on steep slopes. Based on these results, we examine the spatial variability of infiltration, the relationship of rainfall runoff and infiltration to landscape position, the influence of vegetation on infiltration rates on slopes, and the implications of this research for better understanding erosional processes and landscape change.Infiltration rates ranged from 6 to 206 mm/h on lower slopes of the Andes, 16 to 117 mm/h in the southern Appalachians, and 0 to 106 mm/h in the Luquillo Mountains. These rates exceed those of most natural rain events, confirming that surface runoff is rare in montane forests with deep soil/regolith mantles. On well-drained forested slopes and ridges, apparent steady-state infiltration may be controlled by the near-surface downslope movement of infiltrated water rather than by characteristics of the full vertical soil profile. With only two exceptions, the local variability of infiltration rates at the scale of 10° m overpowered other expected spatial relationships between infiltration, vegetation type, slope position, and soil factors. One exception was the significant difference between infiltration rates on alluvial versus upland soils in the Andean study area. The other exception was the significant difference between infiltration rates in topographic coves compared to other slope positions in the tabonuco forest of one watershed in the Luquillo Mountains. Our research provides additional evidence of the ability of forests and forest soils to preserve geomorphic features from denudation by surface erosion, documents the importance of subsurface flow in mountain forests, and supports the need for caution in extrapolating infiltration rates. [Copyright &y& Elsevier]

We measured 10Be and 26Al in 64 sediment and bedrock samples collected throughout the arid, 187 km2 Yuma Wash drainage basin, southwestern Arizona. From the measurements, we determine long-term, time-integrated rates of upland sediment generation (81±5 g m−2 year−1) and bedrock equivalent lowering (30±2 m Ma−1) consistent with other estimates for regions of similar climate, lithology, and topography.In a small (∼8 km2), upland sub-basin, differences in nuclide concentrations between bedrock outcrops and hillslope colluvium suggest weathering of bedrock beneath a colluvial cover is a more significant source of sediment (40×104 kg year−1) than weathering of exposed bedrock surfaces (10×104 kg year−1). Mixing models constructed from nuclide concentrations of sediment reservoirs identify important sediment source areas. Hillslope colluvium is the dominant sediment source to the upper reaches of the sub-basin channel; channel cutting of alluvial terraces is the dominant source in the lower reaches. Similarities in nuclide concentrations of various sediment reservoirs indicate short sediment storage times (<103 years).Nuclide concentrations, measured in channel sediment from tributaries of Yuma Wash and in samples collected along the length of the Wash, were used to construct mixing models and determine sediment sources to the main stem channel. We find an exponential decrease in the channel nuclide concentrations with distance downstream, suggesting that as much as 40% of sediment discharged from Yuma Wash has been recycled from storage within basin fill alluvium.Sediment generation and denudation rates determined from the main stem are greater (25%) than rates determined from upland sub-basins suggesting that, currently, sediment may be exported from the basin more quickly than it is being generated in the uplands. Independence of nuclide concentration and sediment grain size indicates that channels transport sediment in discrete pulses before rapidly depositing poorly sorted material, suggesting that differences in transport times for different size materials are minimal. [Copyright &y& Elsevier]