ancient runoff farming and soil aggradation in terraced wadi fields negev israel obliteration of sedimentary strata by ants scorpions and humans abstract ancient terraced fields in ephemeral stream valleys in the negev desert enabled farming based on runoff water from local rainfall the runoff was captured by stone terrace walls which were built across suitable wadis in various archaeological periods runoff floods added not only water to the fields but also fine sediment however alluvial stratification is usually absent in such terraced wadi fields why we addressed this question at the rural archaeological site of horvat haluqim in the central negev highlands our geoarchaeological excavations in area 3 of terraced field 12 revealed the existence of laminar alluvial stratification but only in the upper 5 cm micromorphology showed a gradual decline in the preservation of laminae with depth radiocarbon dating showed that the upper 50 cm of the terrace soil accumulated during the past 1300 years therefore the average aggradation rate seems about 0 4 mm year similar to modern sedimentation measurements we found evidence for bioturbation particularly by ants and scorpions in the terraced wadi fields at horvat haluqim scorpions evict the soil crumbs excavated from the subsoil on one side of the crescent shaped entrance to their burrows ants on the other hand place the excavated soil crumbs all around the entrance to their underground nest besides bioturbation human soil disturbance by farming is far more destructive to alluvial stratification hoeing and ploughing tillage can erase alluvial laminae from the surface to a depth of about 10 cm in one farming season clear evidence of ancient farming activities in area 3 was found in darker soil layers from a depth of 45 cm 92 cm laminar alluvial strata have not survived in these layers micromorphology revealed fine charcoal bone and pottery fragments interpreted as kitchen household refuse added as fertilizer to the aggrading soil surface in addition non burned dung fragments and non charred spherulites were found indicating also the use of animal dung as manure darker soil layers have a lower bulk density and a high porosity with an extremely large amount of fine pores probably ancient root channels of barley or wheat though runoff flows kept adding laminated alluvial layers to the aggrading terraced wadi fields the fine laminae initial facies did not endure the tooth of time they were gradually obliterated by bioturbation and or rapidly erased by human farming activities tillage and manuring so that laminae are non existent in the ultimate facies of the aggrading sediment soil in agricultural terraced wadi fields

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

magnitude frequency analysis of water redistribution along a climate gradient in spain abstract banded patterns in soils and vegetation form part of important discontinuities on semi arid slopes in spain at fine scales

volcano tectonic implications of 3 d velocity structures derived from joint active and passive source tomography of the island of hawaii 1 we present a velocity model of the onshore and offshore regions around the southern part of the island of hawaii including southern mauna kea southeastern hualalai and the active volcanoes of mauna loa and kilauea and loihi seamount the velocity model was inverted from about 200 000 first arrival traveltime picks of earthquakes and air gun shots recorded at the hawaiian volcano observatory hvo reconstructed volcanic structures of the island provide us with an improved understanding of the volcano tectonic evolution of hawaiian volcanoes and their interactions the summits and upper rift zones of the active volcanoes are characterized by high velocity materials correlated with intrusive magma cumulates these high velocity materials often do not extend the full lengths of the rift zones suggesting that rift zone intrusions may be spatially limited seismicity tends to be localized seaward of the most active intrusive bodies low velocity materials beneath parts of the active rift zones of kilauea and mauna loa suggest discontinuous rift zone intrusives possibly due to the presence of a preexisting volcanic edifice e g along mauna loa beneath kilauea s southwest rift zone or alternatively removal of high velocity materials by large scale landsliding e g along mauna loa s western flank both locations also show increased seismicity that may result from edifice interactions or reactivation of buried faults new high velocity regions are recognized and suggest the presence of buried and in some cases previously unknown rift zones within the northwest flank of mauna loa and the south flanks of mauna loa hualalai and mauna kea

wildfires in the late palaeozoic of central europe an overview of the rotliegend upper carboniferous lower permian of the saar nahe basin sw germany abstract fossil charcoal from a number of different sedimentary settings e g lakes floodplains tuffs tuffites is reported from the rotliegend late carboniferous early permian of the saar nahe basin in sw germany it is one of the largest carboniferous permian basins which developed during the late variscan in europe the sedimentary deposits encompass the carboniferous permian boundary thus enabling us to examine the development of fire regimes parallel to the reconstructed drop in atmospheric o 2 across this boundary the majority of the identified macroscopical charcoal remains belongs to the conifers or other gymnosperms maybe pointing to a more fire prone vegetation in the drier hinterland preferentially inhabited by these plants most wildfires especially those which took place during the deposition of the lower rotliegend late carboniferous have probably been ignited by lightning whereas in the upper rotliegend early permian an intense volcanism may have also acted as an important additional source of ignition in the lower rotliegend charcoals occur in nearly all sedimentary facies types whereas in the upper rotliegend charcoal has so far only been found in some volcanically influenced deposits the absence of charcoal in most sediments from the upper rotliegend may be explained by i low atmospheric oxygen levels leading to reduced fire frequencies ii a generally sparse vegetation cover iii the mechanical breakdown of macroscopic charcoal under the prevailing semiarid conditions

late triassic charcoal from petrified forest national park arizona usa fossil charcoal has been found in the late triassic chinle formation in petrified forest national park a location that is world famous for its silicified tree trunks the material consists of charcoalified secondary wood and has sufficiently well preserved plant anatomy to show it may be described as araucarian type although it does display some minor differences from the anatomies described for the silicified gymnosperm trunks in the park the presence of the charcoal proves that on occasion natural wildfires most probably ignited by lightning must have occurred in the chinle triassic palaeoenvironments with resulting impacts on the biota of those times it is currently impossible to estimate how often these fires occurred as the incidence of charcoal here and in the whole fossil record apart from the frequency of ancient fires also reflects the preservation and burial conditions of the material there is scant mention of triassic charcoal in the literature a notable absence given the abundance of charcoal that has been recorded in the carboniferous jurassic and cretaceous periods this lack of charcoal may support the theory that atmospheric oxygen levels were lower during the triassic than in the carboniferous

how many plates herein i address the current number of plates the number there should be and whether there is a pattern in the plate mosaic related issues are the optimal sizes and shapes of plates and spacings of ridges trenches and transform faults similar questions arise in studies of foams bubble rafts buckyballs mudcracks columnar jointing the tessellation of spheres and the planforms of convection in sphere covering problems and in dynamic problems pentagons replace the familiar hexagons the ground state of plate tectonics on a homogeneous planet may involve 12 plates with five nearest and five next nearest neighbors the plate mosaic may be a self organized network of plates and force chains which are readily reorganized by stress changes this paper starts with the premise that the mosaic may have simple and surficial explanations rather than convective or plutonic causes the study of the tessellation of earth can be called platonics to distinguish it from the idea that the lithosphere necessarily mirrors the planform of mantle convection

residual colluvio aeolian aprons in the negev highlands israel as palaeo climatic indicator abstract slope features treated previously mainly pedogenetically and described as alluvial terraces or as a catenary compound of stony loessial sierozem are shown to be remains of former colluvial loessial aprons the loess was deposited in the central negev during the uppermost pleistocene by dust laden rainstorms which triggered debris flows under conditions twice as humid as today during the holocene the aprons were selectively eroded by slope runoff resulting in a wide exposure of the basal slope truncation of the wadi fill and the final formation of the present day patchy slope morphology the dust laden rainy regime fits the last more humid period i e 70 000 10 000 yr b p

global coal gap between permian triassic extinction and middle triassic recovery of peat forming plants early triassic coals are unknown and middle triassic coals are rare and thin the early triassic coal gap began with extinction of peat forming plants at the end of the permian ca 250 ma with no coal known anywhere until middle triassic 243 ma permian levels of plant diversity and peat thickness were not recovered until late triassic 230 ma tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal bearing sequences are present also in early triassic rocks nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers insects or tetrapod herbivores which became cosmopolitan and much reduced in diversity across the permian triassic boundary instead we favor explanations involving extinction of peat forming plants at the permian triassic boundary followed by a hiatus of some 10 m y until newly evolved peat forming plants developed tolerance to the acidic dysaerobic conditions of wetlands this view is compatible not only with the paleobotanical record of extinction of swamp plants but also with indications of a terminal permian productivity crash from delta sup 13 c sub org and total organic carbon of both nonmarine and shallow marine shales 205 refs 3 figs more 3 tabs less

pedo sedimentary constituents as paleoenvironmental proxies in the sudano sahelian belt during the late quaternary southwestern chad basin abstract climate and environmental changes since the last glacial maximum in the tropical zone of west africa are usually inferred from marine and continental records in this study the potential of carbonate pedo sedimentary geosystems i e vertisol relics to record paleoenvironmental changes in the southwestern part of chad basin are investigated a multi dating approach was applied on different pedogenic organo mineral constituents optically stimulated luminescence osl dating was performed on the soil k rich feldspars and was combined with radiocarbon dating on both the inorganic 14cinorg and organic carbon 14corg soil fractions three main pedo sedimentary processes were assessed over the last 20 ka bp 1 the soil parent material deposition from 18 ka to 12 ka bp osl 2 the soil organic matter integration from 11 cal ka to 8 cal ka bp 14corg and 3 the pedogenic carbonate nodule precipitation from 7 cal ka to 5 cal ka bp 14cinorg these processes correlate well with the chad basin stratigraphy and west african records and are shown to be related to significant changes in the soil water balance responding to the evolution of continental hydrology during the late quaternary the last phase affecting the vertisol relics is the increase of erosion which is hypothesized to be due to a decrease of the vegetation cover triggered by i the onset of drier conditions possibly strengthened by ii anthropogenic pressure archaeological data from far north cameroon and northern nigeria as well as sedimentation times in lake tilla northeastern nigeria were used to test these relationships the increase of erosion is suggested to possibly occur between c 3 cal ka and 1 cal ka bp finally satellite images revealed similar geosystems all along the sudano sahelian belt and initial 14cinorg ages of the samples collected in four sites gave similar ages to those reported in this study consequently the carbonate pedo sedimentary geosystems are valuable continental paleoenvironmental archives and soil water balance proxies of the semiarid tropics of west africa

surface crusting in two alluvial soils of northen niger valentin c 1991 surface crusting in two alluvial soils of northen niger geoderma 48 201 222 surface crusting was studied in a sandy soil and a clay loam soil in northern niger in a subdesert to desert environment light microscopy electron microscopy image analysis and soil physics were used to study and explain different crusting processes in experimental plots two 1 m2 plots on each soil were subjected to rainfall simulation in the field under natural and tilled surface conditions this study demonstrates that kinetic energy of rainfall is the major crusting factor for the sandy soil waterlogging and subsequent slaking led to the formation of structural and depositional crusts in the tilled clay loam plot in this case a surface crust can be formed regardless of kinetic energy of the rainfall this was substantiated through double ring infiltrometer measurements in both soils infiltration was severely hindered by crusting the relationships of crusting to water and wind erosion were more ambiguous four types of crusts could be defined from this study in terms of structure genetic processes and properties it could also be demonstrated that crust control practices should take into account the texture of the original soil materials

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

the record of triassic charcoal and other evidence for palaeo wildfires signal for atmospheric oxygen levels taphonomic biases or lack of fuel abstract as wildfires are today important sources of disturbance in many terrestrial ecosystems it is of great interest to understand how different environmental parameters and fire activity interacted during past periods of the earth history fossil charcoal inertinites and pyrogenic polycyclic aromatic hydrocarbons pahs represent the only direct evidence for the occurrence of such palaeo wildfires in the present study a review of published data together with new data on the occurrence of fossil charcoal for the permian and the triassic is presented for a long time it has been speculated that an assumed lack of evidence for palaeo wildfires during the triassic should be explained by a large drop in atmospheric oxygen concentration following or during the end permian mass extinction event preventing the occurrence of wildfires however evidence for palaeo wildfires is relatively common in many middle and late triassic strata whereas such evidence is almost totally lacking from early triassic sediments the interpretation of this charcoal gap or depression is difficult as many factors e g atmospheric oxygen concentration taphonomical biases lack of sediments suitable for the preservation of macroscopic charcoal lack of fuel and ignorance of scientists may have influenced not only the production but also the preservation and recovery of evidence for palaeo wildfires during this period thus it is not clear whether this early triassic charcoal gap can also be seen as evidence for an assumed wildfire gap or not without any doubt further investigations on the early triassic record of charcoal and other evidence for palaeo wildfires will be necessary before this problem can be solved in fact it can be expected that the number of published records of early triassic evidence for palaeo wildfires will increase in the future as more and more scientist working on sediments of this age may become aware of the interest in fires from this time this will certainly make it possible to give a much better picture of the temporal and regional distribution of wildfires during this period in the future

comparative velocity structure of active hawaiian volcanoes from 3 d onshore offshore seismic tomography abstract we present a 3 d p wave velocity model of the combined subaerial and submarine portions of the southeastern part of the island of hawaii based on first arrival seismic tomography of marine airgun shots recorded by the onland seismic network our model shows that high velocity materials 6 5 7 0 km s lie beneath kilauea s summit koae fault zone and the upper southwest rift zone swrz and upper and middle east rift zone erz indicative of magma cumulates within the volcanic edifice a separate high velocity body of 6 5 6 9 km s within kilauea s lower erz and upper puna ridge suggests a distinct body of magma cumulates possibly connected to the summit magma cumulates at depth the two cumulate bodies within kilauea s erz may have undergone separate ductile flow seaward influencing the submarine morphology of kilauea s south flank low velocities 5 0 6 3 km s seaward of kilauea s hilina fault zone and along mauna loa s seaward facing kao iki fault zone are attributed to thick piles of volcaniclastic sediments deposited on the submarine flanks loihi seamount shows high velocity anomalies beneath the summit and along the rift zones similar to the interpreted magma cumulates below mauna loa and kilauea volcanoes and a low velocity anomaly beneath the oceanic crust probably indicative of melt within the upper mantle around kilauea s submarine flank a high velocity anomaly beneath the outer bench suggests the presence of an ancient seamount that may obstruct outward spreading of the flank mauna loa s southeast flank is also marked by a large anomalously high velocity feature 7 0 7 4 km s interpreted to define an inactive buried volcanic rift zone which might provide a new explanation for the westward migration of mauna loa s current swrz and the growth of kilauea s swrz

experiments in waterlogging and sedimentology of charcoal results and implications abstract fossil charcoal has a sporadic occurrence in sedimentary rocks since devonian time it is moderately common as a component of the organic material found in a wide variety of facies but there are also some notable concentrations which occur locally these occurrences have considerable palaeobotanical and palaeoecological value because the process of charring may result in excellent preservation of plant tissue if assemblages of charred material are to be used to interpret palaeoenvironments it is important to understand the behaviour of charcoal during transport from the site of the fire charcoal is an unusual sedimentary material because most fresh material floats but with prolonged immersion becomes waterlogged and sinks we carried out a series of waterlogging experiments on uncharred material and charcoal from a range of different plant types and tissues these show considerable variations in the rates of waterlogging of different charred and uncharred plant tissues and it is suggested that buoyancy contrasts are likely to result in separation during transport and deposition furthermore experiments in a flume tank have shown that the process of deposition of charcoal in sand is controlled by the rate of migration of bedforms which is in turn determined by depth flow velocity and sediment supply allochthonous assemblages of charred and uncharred plant debris will most probably be biased and not fully representative of the contemporaneous plants or vegetation the presence of charcoal concentrations may be used as an aid in interpreting palaeohydraulic conditions

paleoecology reconstruction from trapped gases in a fulgurite from the late pleistocene of the libyan desert when lightning strikes the ground it heats melts and fuses the sand in soils to form glass tubes known as fulgurites we report here the composition of co 2 co and no contained within the glassy bubbles of a fulgurite from the libyan desert the results show that the fulgurite formed when the ground contained 0 1 wt organic carbon with a c n ratio of 10 15 and a 13 c of 13 96 compositions similar to those found in the present day semiarid region of the sahel where the vegetation is dominated by c 4 plants thermoluminescence dating indicates that this fulgurite formed 15 k y ago these results imply that the semiarid sahel at 17 n reached at least to 24 n at this time and demonstrate that fulgurite gases and luminescence geochronology can be used in quantitative paleoecology

modelling runoff and erosion for a semi arid catchment using a multi scale approach based on hydrological connectivity runoff and erosion processes are often non linear and scale dependent which complicate runoff and erosion modelling at the catchment scale one of the reasons for scale dependency is the influence of sinks i e areas of infiltration and sedimentation which lower hydrological connectivity and decrease the area specific runoff and sediment yield the objective of our study was to model runoff and erosion for a semi arid catchment using a multi scale approach based on hydrological connectivity we simulated runoff and sediment dynamics at the catchment scale with the lapsus model and included plot and hillslope scale features that influenced hydrological connectivity the semi arid carcavo catchment in southeast spain was selected as the study area where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales respectively we elaborated the infiltration module to integrate these runoff sinks by adapting the parameters runoff threshold and runoff coefficient which were derived from a rainfall simulation database the results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale runoff and sediment yield for the scenario without agricultural terraces were respectively a factor four and nine higher compared to the current situation distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion sedimentation patterns

palaeoclimatic interpretation of the wood structures of the trees in the chinle formation upper triassic petrified forest national park arizona usa abstract typically the fossil woods in the upper triassic chinle formation in petrified forest national park arizona usa do not show annual growth rings but contain irregular growth interruptions similar to those found in trees now growing in the humid tropics these interruptions could be due to endogenous hormonal effects or to occasional local variations in water supply therefore it is conclucded that the late triassic fossil forests in the park lived in conditions that permitted continuous tree growth limited data from areas outside of the park suggests that similar conditions prevailed in adjacent areas in the southwestern united states during the late triassic although this region is reported to have been under the influence of a monsoonal circulation pattern during the late triassic the growth of the trees does not appear to have been greatly affected

sediment transport by runoff on debris mantled dryland hillslopes 1 hillslopes supply sediment to river channels and therefore impact drainage basin functioning and evolution the relationship between hillslope attributes and sediment flux forms the basis of geomorphic transport laws used to model the long term topographic evolution of drainage basins but their specific interactions during individual storm events are not well understood runoff driven erosion of coarse particles prevalent in dryland environments presents a particular set of conditions for sediment transport that is poorly resolved in current models in order to address this gap we developed a particle based force balance model for sheetwash sediment transport on coarse debris mantled hillslopes within a rainfall runoff model we use the model to examine how the interplay between hillslope attributes gradient length and grain size distribution and runoff characteristics affects sediment transport grain size changes on the hillslope and sediment supply to the slope base the relationship between sediment flux and hillslope gradient was found to transition from linear above a threshold to sigmoidal depending on hillslope length initial grain sizes and runoff characteristics grain sizes supplied to the slope base vary in a complex manner with hillslope attributes but an overall coarsening of the hillslopes is found to occur with increasing gradient corroborating previous findings from field measurements intense short duration storms result in within hillslope sediment redistribution and equifinality in sediment supply for different hillslope characteristics which explain the lack of field evidence for any systematic relationships our model findings provide insights into hillslope responses to climatic forcing and have theoretical implications for modeling hillslope evolution in dry lands

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

the ninole basalt implications for the structural evolution of mauna loa volcano hawaii lava flows of the ninole basalt the oldest rocks exposed on the south side of the island of hawaii provide age and compositional constraints on the evolution of mauna loa volcano and the southeastward age progression of hawaiian volcanism although the tholeiitic ninole basalt differs from historic lavas of mauna loa volcano in most major element contents e g variably lower k na si higher al fe ti ca ree and other relatively immobile minor elements are similar to historic and prehistoric mauna loa lavas and the present major element differences are mainly due to incipient weathering in the tropical environment new k ar whole rock ages from relatively fresh roadcut samples suggest that the age of the ninole basalt is approximately 0 1 0 2 ma although resolution is poor because of low contents of k and radiogenic ar originally considered the remnants of a separate volcano the ninole hills are here interpreted as faulted remnants of the old south flank of mauna loa deep canyons in the ninole hills eroded after massive landslide failure of flanks of the southwest rift zone have been preserved from burial by younger lava due to westward migration of the rift zone landslide induced depressurization of the southwest rift zone may also have induced phreatomagmatic eruptions that could have deposited widespread basaltic ash that overlies the ninole basalt subaerial presence of the ninole basalt documents that the southern part of hawaii island had grown to much of its present size above sea level by 0 1 0 2 ma and places significant limits on subsequent enlargement of the south flank of mauna loa

analytical model for a geomorphological instantaneous unit hydrograph the rainfall runoff modelling of a river basin can be divided into two processes the production function and the transfer function the production function determines the proportion of gross rainfall actually involved in the runoff the transfer function spreads the net rainfall over time and space in the river basin such a transfer function can be modelled using the approach of the geomorphological instantaneous unit hydrograph giuh the effectiveness of geomorphological models is actually revealed in rainfall runoff modelling where hydrologic data are desperately lacking just as in ungauged basins these models make it possible to forecast the hydrograph shape and runoff variation versus time at the basin outlet this article is an introduction to a new giuh model that proves to be simple and analytical its geomorphological parameters are easily available on a map or from a digital elevation model this model is based on general hypotheses on symmetry that provide it with multiscale versatile characteristics after having validated the model in river basins of very different nature and size we present an application of this model for rainfall runoff modelling since parameters are determined relying on real geomorphological data no calibration is necessary and it is then possible to carry out rainfall runoff simulations in ungauged river basins copyright c 2006 john wiley sons ltd

climate and surface properties hydrological response of small arid and semi arid watersheds abstract a positive relationship between annual rainfall and geomorphic processes runoff and erosion rates and environmental factors water regime soil and vegetation cover is often assumed for arid and semi arid areas with an annual rainfall in the range of 100 300 mm this assumption disregards the fact that changes along a climatic gradient at desert margins are not limited to purely climatic factors they are often accompanied by a parallel change in surface properties especially the relative extent of rocky or soil covered surfaces that differ greatly in their response to rainfall this raises the issue whether the change in surface properties along a climatic gradient enhances the assumed positive effects of rainfall increase or limits it the hypothesis advanced in this paper is that runoff generation and rate in arid and semi arid areas are primarily controlled by surface properties rather than by the absolute amounts of storm and annual rain amounts hydrological data collected at two instrumented watersheds located one in an arid rocky area and the second in a semi arid soil covered area support this hypothesis the implications of data obtained for runoff generation and flow continuity under changing climatic conditions are analyzed they point to the fact that the same regional climatic change may have different and even opposite effects on the hydrological response of different adjoining surface units this response is expected to be strongly controlled by the specific local surface conditions that prevailed in the area prior to the climatic change

submarine growth and internal structure of ocean island volcanoes based on submarine observations of mauna loa volcano hawaii a recent model for the submarine growth of hawaiian volcanoes indicates that these volcanoes are composed mainly of fragmental lava debris formed as lavas enter the ocean this model has major implications for locating earthquake hypocenters and for the landslide hazard potential of these and other ocean island volcanoes observations from submersible dives and analyses of volcanic glasses collected from the western submarine flank of mauna loa indicate that subaerially erupted pillow lavas are abundant at depths of 950 to 1900 m below sea level fragmental lava is an important component of ocean island volcanoes as witnessed during the most recent eruption of kilauea volcano but probably is the dominant lithology only in the upper 1 km of the submarine section a submarine dike complex was discovered 17 km west of the assumed axis of mauna loa9s southwest rift which indicates that its intrusive complex is much broader than previously suspected 20 km vs 8 km the great width of this dike complex may be a consequence of crustal unloading following the south kona landslide or a normal feature of hawaiian rift zones that was previously unrecognized

wildfires in the late palaeozoic of central europe the zechstein upper permian of nw hesse germany abstract fossil charcoal as the direct evidence of wildfires is present in most of the plant bearing deposits from the central european zechstein upper permian the charcoal content of upper permian sediments collected at the locality frankenberg geismar nw hesse germany is allochthonous and the shape of the fragments and the rounded edges indicate transport over relatively long distances charcoalified conifer needles are very rare and usually highly fragmented the anatomical diversity of charred wood is higher than that of the permineralised woods from the zechstein that have been described previously it is not yet clear whether this represents a higher diversity of natural taxa or anatomicaly different parts belonging to only a few taxa until now virtually nothing is known about the fire ecology of late palaeozoic conifer dominated upland vegetation the presence of charcoal indicates that these vegetation which grew under mesic to xeric conditions may have experienced more or less regular wildfires wildfires may have been relatively frequent during the late permian as compared to climatically comparable modern ecosystems

slope failure and volcanic spreading along the submarine south flank of kilauea volcano hawaii 1 new multichannel reflection data and high resolution bathymetry over the submarine slopes of kilauea volcano provide evidence for current and prior landsliding suggesting a dynamic interplay among slope failure regrowth and volcanic spreading disrupted strata along the upper reaches of kilauea s flank denote a coherent slump correlated with the active hilina slump the slump comprises mostly slope sediments underlain by a detachment 3 5 km deep extension and subsidence along the upper flank is compensated by uplift and folding of the slump toe which surfaces about midway down the submarine flank uplift of strata forming papa u seamount and offset of surface features along the western boundary of kilauea indicate that the slump has been displaced 3 km in a south southeast direction this trajectory matches coseismic and continuous ground displacements for the hilina slump block on land and contrasts with the southeast vergence of the rest of the creeping south flank to the northeast slope sediments are thinned and disrupted within a recessed region of the central flank demonstrating catastrophic slope failure in the recent past debris from the collapsed flank was shed into the moat in front of kilauea building an extensive apron seaward sliding of kilauea s flank offscraped these deposits to build an extensive frontal bench a broad basin formed behind the bench and above the embayed flank uplift and back tilting of young basin fill indicate recent and possibly ongoing bench growth the hilina slump now impinges upon the frontal bench this buttress may tend to reduce the likelihood of future catastrophic detachment

accuracy constraints of terrestrial lidar data for soil erosion measurement application to a mediterranean field plot abstract applications of terrestrial laser scanning tls to measure soil erosion are yet limited although this topographic mapping method allows for large area coverage with high resolution and reliable precision however restricting factors are accurate and stable references for multi temporal change detection and adverse scanning geometries at agricultural fields the plot is usually situated on gentle slopes provoking low viewing angles of the scanning device onto the surface which inherits the risk of high data noise in this study tls is exploited from a high tripod to measure soil erosion at an andalusian hillslope 2 1000 m2 in the mediterranean sediment yield reveals discontinuous pattern and tls is a promising method to quantify these surface changes a stable reference system is defined resulting in multi temporal registration accuracy better than 7 mm further an mm accurate calibration plot 60 m2 is designed to evaluate scan geometry and radiometry i e incidence angle footprint and intensity in dependence of distance related errors a lookup table is determined to correct systematic errors of the field data the andalusian field plot is captured during a winter season and during single precipitation events estimated erosion rates amount 10 and 2 4 t ha 1 respectively surface changes with magnitudes larger 1 5 cm are reliably measured tls can be implemented to estimate soil erosion with cm resolution if errors are carefully accounted for

ecogeomorphology in the australian drylands and the role of biota in mediating the effects of climate change on landscape processes and evolution

later stages of volcanic evolution of la palma canary islands rift evolution giant landslides and the genesis of the caldera de taburiente the islands of la palma and el hierro form the western end of the hotspot induced canary islands chain both islands are at present in the earliest and fastest shield building stage of growth and show many similarities with the hawaiian islands la palma shows two very distinct phases of volcanic construction 1 a pliocene submarine volcanic and intrusive series interpreted as an uplifted seamount at least 1500 m above present sea level and 2 a subaerial volcanic series erupted in the past 2 m y taburiente volcano initially formed the northern part of the island and then extended to the south forming a ridge cumbre nueva ridge that was partially destroyed about 560 ka by a giant lateral collapse the cumbre nueva collapse possibly involving 180 200 km 3 of subaerial volcanic material the northwest boundary of the cumbre nueva collapse formed a vertical scarp that enlarged by headward erosion formed the spectacular depression of caldera de taburiente cumbre vieja volcano a north south elongated rift forms the southern half of la palma and constitutes its last stage of growth including all eruptive activity in the past 125 k y detailed field observations mapping and high precision radiometric dating have allowed reconstruction of the growth and structural changes of the cumbre vieja volcano interactions between eruption rates coastal erosion and glacio eustatic sea level change allow stratigraphic subdivision of the edifice the structure of the volcano has been controlled for most of its history by a rift system with a clearly dominant north south and less distinct north east and north west volcanic rift zones the rift reorganization of the volcano to a single north south rift since 7 ka and the opening of faults during the 1949 eruption probably reflect increasing instability of the west flank of the volcano

linking spatial patterns of soil organic carbon to topography a case study from south eastern spain a key uncertainty in our understanding of the global carbon cycle is the lateral movement of carbon through the terrestrial system soils are the major storage of carbon in the terrestrial biosphere and the inventory of soil organic carbon soc is required for greenhouse gas inventories and carbon mitigation projects the aim of this study is to characterize spatial patterns of the concentrations of topsoil total organic carbon toc in a semi arid mediterranean area in south eastern spain and to assess their relationship to topography we adopt a remote sensing based approach for the spectral determination and quantification of toc with a complete coverage of bare soil surfaces digital terrain analysis and geostatistical techniques are applied to analyze the spatial patterns of toc at different spatial scales we show that accumulation of topsoil soc is dependent on topographic position at the landscape scale with highest values found in valley bottoms at the hill slope scale differences among terrain classes exist regarding the topographic controls on soc while positive correlation between the topographic wetness index twi and toc can be observed on steep slopes that correlation is not significant on wide pediments small scale spatial variability is large on ridges steep slopes and valley bottoms while soc distribution on pediments is relatively homogeneous these differences are most likely governed by the presence of vegetation patches and variable runoff and sediment transport rates among the terrain classes the successful application of hyperspectral remote sensing for the spatial estimation of soc concentrations suggests that it is a promising technique to advance soc inventories in semi arid and arid regions

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

the effects of igneous dike intrusion on organic geochemistry of black shale and its implications late jurassic jhuran formation india abstract this study documents the effects of igneous dike intrusion on organic geochemical parameters of a shallow marine originated late jurassic black shale av toc 2 2 wt in the kutch rift basin in western india the dike intrusion forms extremely to mildly altered meter scale zones around them the primary wrinkled micro texture of the shale is lost completely and organic matter is charcoalized in the extremely altered zone recording a rock eval tmax 458 c immature type iii kerogen dominating the unaltered shale records abundant coniferal biomarkers such as retene ent beyerane phyllocladane ent kaurane abietane labdane and norisopimarane besides n alkanes hopanes and steranes the transition from the unaltered rock eval tmax

conceptualization and scale in hydrology abstract it is argued that the levels of scale at which a meaningful conceptualization of physical processes is possible are not arbitrary and their range is not continuous formulations appropriate at a given level usually are not applicable at the immediately adjoining levels this is seen as one of the important reasons for the slow progress of hydrological science on basin scale since it is dominated by different effects than those observed at the immediately lower level of channel reaches and hillslopes which represent the focus of current hydrological research the search for an appropriate level of conceptualization can proceed either upward or downward along the hierarchy of scales both possibilities are discussed and an example of the downward route is given

hydrological responses and soil erosion potential of abandoned cropland in the loess plateau china recent changes in hydrological processes and soil erosion in the loess plateau china are immediate responses to cropland abandonment for revegetation which lead to a long term decrease in runoff generation and soil erosion however detailed hydrological responses and soil erosion changes have not been clearly evaluated in this study two issues were focused on the plot scale the first issue relates to changes in vegetation cover and soil properties during the early stages of revegetation given the occurrence of soil compaction it was hypothesized that runoff increased during this period and the soil erosion did not significantly decline even though vegetation increased the second issue is the effect of scale on runoff and soil erosion three plot groups of three vegetation types and two restoration stages were established for comparative experiments the results from these experiments confirmed that the soil compaction occurred during revegetation in this region greater runoff was produced in plot group that experienced both a longer restoration time and with higher vegetation cover such as groups 2 and 3 in this study than that with a shorter restoration time and lower vegetation cover group 1 in addition the total soil loss rates of all plot groups were rather low and did not significantly differ from each other this indicates that a reduction in runoff generation and soil erosion as a result of revegetation was limited in the early stages of restoration following the cropland abandonment with increasing plot area the runoff coefficient decreased for the plot group with a longer revegetation time groups 2 and 3 but gently increased for the one with a shorter restoration time group 1 in groups 2 and 3 soil loss rate decreased when plot area enlarged in group 1 it decreased before a plot area threshold of 18 m 2 was exceeded however the increase occurred when plot area crossed the threshold value in conclusion the high vegetation cover alone did not lead to reduction in the runoff coefficient during the early stages of revegetation when evaluating hydrological and soil erosion responses to revegetation the soil compaction processes should be considered additionally the effect of scale on runoff and soil erosion was found to be dependent on restoration extent and thus on restoration time c 2011 elsevier by all rights reserved

stratigraphic distribution and significance of a 15 million year record of fusain in the upper triassic chinle group southwestern usa abstract we document the occurrence of upper triassic fusain in northern arizona southern utah and northern new mexico in latest carnian to norian age alluvial strata of the monitor butte formation and the sonsela and painted desert members of the petrified forest formation chinle group the fusain identified by standard techniques of macroscopic and microscopic morphology and resistance to chemical oxidation is present at multiple stratigraphic horizons at several locations that are approximately correlative although separated by several hundred km the morphology of this fossil charcoal includes large partially charred silicified to coalified logs completely charred smaller limbs charcoal fragments reworked in fluvial deposits and particulate fusain disseminated in sediments the apparent rarity of fusain in triassic strata previously was cited as evidence for relatively low levels compared to modern of atmospheric oxygen and the consequent infrequent occurrence of wildfire during this time interval however our findings demonstrate a significantly greater abundance of fusain in upper triassic strata than previously acknowledged therefore we suggest that wildfire was not an unusual occurrence during the late triassic this conclusion supports recent experimental studies and geochemical models that indicate atmospheric oxygen levels at or above modern levels during the late triassic

forearc structure beneath southwestern british columbia a three dimensional tomographic velocity model 1 this paper presents a three dimensional compressional wave velocity model of the forearc crust and upper mantle and the subducting juan de fuca plate beneath southwestern british columbia and the adjoining straits of georgia and juan de fuca the velocity model was constructed through joint tomographic inversion of 50 000 first arrival times from earthquakes and active seismic sources wrangellia rocks of the accreted paleozoic and mesozoic island arc assemblage underlying southern vancouver island in the cascadia forearc are imaged at some locations with higher than average lower crustal velocities of 6 5 7 2 km s similar to observations at other island arc terranes the mafic eocene crescent terrane thrust landward beneath southern vancouver island exhibits crustal velocities in the range of 6 0 6 7 km s and is inferred to extend to a depth of more than 20 km the cenozoic olympic subduction complex an accretionary prism thrust beneath the crescent terrane in the olympic peninsula is imaged as a low velocity wedge to depths of at least 20 km three zones with velocities of 7 0 7 5 km s inferred to be mafic and or ultramafic units lie above the subducting juan de fuca plate at depths of 25 35 km the forearc upper mantle wedge beneath southeastern vancouver island and the strait of georgia exhibits low velocities of 7 2 7 5 km s inferred to correspond to 20 serpentinization of mantle peridotites and consistent with similar observations in other warm subduction zones estimated dip of the juan de fuca plate beneath southern vancouver island is 11 16 and 27 at depths of 30 40 and 50 km respectively

growth and persistence of hawaiian volcanic rift zones hawaiian volcanic rift zones are modeled by representing the rifts and adjacent volcano flanks as long ridges with the geometry of flattened triangular prisms the intrusion of dikes along the axis of a rift requires a mechanism to generate the appropriate dike trapping stress field within the prism possible factors that affect the state of stress in the prism include multiple dike intrusion along the ridge axis faulting and gravitational sagging of the topography in extreme models with very steep slopes and high poisson s ratio corresponding to the gelatin models of rift zones by fiske and jackson 1972 results of finite element calculations indicate that gravity induced stresses are sufficient to trap a dike into propagating within the prism and parallel to the rift zone as proposed by fiske and jackson however the mechanism does not work for gently sloping flanks or a more acceptable poisson s ratio of about 0 25 additionally trapping stresses in the gravity loading and density stratification models will not persist after a few dike injection episodes therefore in mature hawaiian rift zones with possibly thousands of dikes additional processes must act to control the stresses that permit continued dike intrusion and rift persistence it is proposed that accommodation to dike emplacement occurs by slip on deep faults possibly of the type proposed for the 1975 kalapana hawaii earthquake as suggested by others for this earthquake the faults could coincide with the contact of the volcano with the seafloor within the weak seafloor sediments such faulting not only provides a means for the flanks to adjust continuously to intrusions but also generates the stress patterns needed to constrain future dikes to propagate along the rift axis other possible faulting mechanisms such as shallow gravity slides and normal faulting of the flanks do not appear to favor rift zone persistence in this model the horizontal stress generated by a standing column of magma at the time of dike emplacement the stresses in the ridges and the fault strength are coupled this results in a feedback between the maximum height that magma can rise along the rift fault friction and fault width through this feedback the slope of the volcano flank is controlled by the fault friction when applied to kilauea volcano the model yields an estimate for the coefficient of fault friction as high as 0 39 assuming normal hydrostatic pore fluid pressure an implication of this model supported by other studies is that rift intrusion and lateral spreading could be major contributors to volcano growth

volcanic spreading on mauna loa volcano hawaii evidence from accretion alteration and exhumation of volcaniclastic sediments a transect of submersible dives across the submarine west flank of mauna loa volcano yields compelling evidence for volcanic spreading and associated hydrothermal circulation during volcano growth a frontal bench at the toe of the flank formerly thought to be a downdropped block of mauna loa contains a mix of volcaniclastic lithologies including distally derived siltstone mudstone and hyaloclastite the bench is overlain by bedded gravels and subaerially erupted pillow flows derived from local shoreline crossing lava flows the volcaniclastic strata in the bench were offscraped uplifted and accreted to the edge of the flank as it plowed seaward into the surrounding moat the accreted strata underwent significant diagenesis through deep burial and circulation of hydrothermal fluids expelled from porous sediments beneath the volcano timing constraints for bench growth and breakup suggest that catastrophic failure of the subaerial edifice ca 250 200 ka triggered volcanic spreading by reducing stresses resisting basal sliding and rift zone inflation increased eruptive activity and westward migration of mauna loa9s southwest rift zone gradually rebuilt the massive flank arresting slip prior to detachment of the alika 2 debris avalanche ca 120 ka

ant mounds as a source of sediment on citrus orchard plantations in eastern spain a three scale rainfall simulation approach abstract ants are widely found in mediterranean soils where they increase water infiltration rates by forming soil macropores during nest construction while higher water infiltration usually results in lower soil erosion rates new soil brought to the surface by ant activity could increase sediments available for erosion this could be especially important in intensively managed citrus orchards where surface mineral soil is exposed due to the lack of vegetation cover as a consequence of herbicide treatments in the summer of 2009 rainfall simulations of low frequency high intensity rainstorms were conducted in an orange orchard in eastern spain on plots that contained ant nests and adjacent paired plots without ant nests since soil erosion is a scale dependent process we used three plot sizes 0 25 m 2 1 m 2 and 12 m 2 to determine the effect of ant burrowing and nesting on soil and water losses ant nests decreased water losses from 22 5 at 0 25 m 2 to 10 6 at 12 m 2 but soil erosion rates were nearly double in areas with ant activity 0 56 to 0 59 mg ha 1 h 1 as compared to soil with no ants 0 31 to 0 36 mg ha 1 h 1 our results indicate that the presence of ants can increase soil erosion when rainfall intensity is greater than the infiltration capacity of the ant macropores

response of loess materials to simulated translocation by water micromorphological observations structural differences between loess material deposits produced by splash flow without splash and by rainwash i e combined splash and flow respectively were reported earlier mucher and de ploey 1977 deposits from splash alone proved to be non layered and had incurred almost no additional particle sorting deposits from flow without splash were well layered while individual laminae displayed excellent sorting rainwash produced poorly layered deposits with poorly sorted individual laminae only horizontal and subhorizontal bedding and no cross bedding were observed similar features appeared in samples from naturally layered loess deposits collected from excavations the present paper focuses on the granulometric character of the artificially created layers experiments normally involved the combined use of an erosion and a sedimentation flume slope angles of the flumes varied mainly form 0 25 to 4 degrees precipitation intensities varied from 7 to 120 mm per hour unit discharges ranged from 0 2 to 9 2 cm3 cm s flow was laminar or smooth turbulent either subcritical or supercritical froude numbers between 0 5 and 3 8 raindrop impact had little influence on the flow velocity and thickness of the surficial water film but it significantly increased transportation capacity and flow competence savat 1976 1977 undisturbed samples were collected during the experiments and impregnated with unsaturated polyester resin thin sections of 20 m thickness were studied under a polarizing microscope comparative observations were made on naturally layered loess materials during rainwash clay size particles are removed and exported whereas laminae with particles from 10 to 50 microns are more frequently produced than those with particles from 10 to 30 microns flow without splash produced relatively more laminae with grains smaller than 30 microns diameter striking in all samples is the absence of laminae composed of 30 50 m grains aggregates were only deposited by smooth turbulent flow either disturbed or undisturbed by raindrop impact in view of the experimental results the naturally formed loess deposits may be interpreted as follows the bulk of the loess from the excavation near tongrinne belgium was reworked under influence of turbulent rainwash only one sample contained laminae consisting of clay particles smaller than 10 m and of particles from 10 30 m respectively suggesting deposition from flow without splash this was taken from a gully infilling a gully fill from the excavation heverlee near leuven belgium is characterized by poorly sorted laminae dominated by the coarser silt fractions this suggests infilling under influence of turbulent rainwash

paleogeography as geological heritage developing geosite classification abstract geological heritage sites geosites are sites that contain information about the state and the dynamics of the earth paleogeographical paleoenvironmental geosites preserve paleoenvironments paleoecosystems and other relevant phenomena however the value of these sites can only be fully understood through professional interpretation of the observed features description of paleogeographical geosites in terms of the paleospace and the geologic time they encompass is challenging partially because of many uncertainties in the interpretations of a given geosite and in the paleogeographical paleobiogeographical and stratigraphical nomenclature these geosites can be classified on the basis of facies paleoecosystems ichnological value taphonomic patterns major events and catastrophes and geoarcheological potential that they exhibit some geosites comprise several subtypes and some are especially important for construction of paleogeographical maps moreover the paleogeographical geosite type always associates with other types of geosites 20 in total these combinations form complex geosites that contribute to geodiversity if information about the earth s past is especially valuable for a given complex geosite then the paleogeographical type is dominant

effectiveness of exceptional rainstorms on a small mediterranean basin abstract a comprehensive investigation of rainstorms and their consequent impacts on landscape evolution is geomorphologically important but only scant information may be available on exceptional events because parameters on synoptic conditions rainstorm landforms and hydrology for such events may be incomparable with previous knowledge we studied an exceptional storm on april 2 2006 in the ramot menashe region israel our investigation of rainfall landslides debris flows and channel suggests the effectiveness of such an event on the development of basin scale morphology the storm caused damage and casualties although it covered relatively narrow strips neither direct rainfall nor runoff measurements exist for the most severely affected area of ramot menashe but the geomorphologic evidence combined with high resolution meteorological radar data provides the basic understanding of the processes and hazardous conditions which prevailed at the time in the storm core based on estimation from meteorological radar data 263 mm of rain fell within 3 h with a maximum intensity of 220 mm h 1 for 10 min triggering both sporadic landslides at the soil bedrock contact on the upper slopes and widespread landslides at the fractured massive bedrock contact on the lower slopes the 1st order channels on the alternation of chalk and marl also underwent erosion and the produced sediment deposited on alluvial fans at the confluence with the main channel the specific peak discharges for catchment size of 0 3 10 km2 were 11 to 73 m3 s 1 km 2 higher than any recorded floods in the mediterranean climatic region of israel the effectiveness of the flood for geomorphic work represented by shear stress and stream power per unit boundary area reached 87 398 n m 2 and 212 2134 w m 2 respectively this kind of analysis can be applied to hazard prediction in other areas under similar geomorphological conditions

rift zone reorganization through flank instability in ocean island volcanoes an example from tenerife canary islands the relationship between rift zones and flank instability in ocean island volcanoes is often inferred but rarely documented our field data aerial image analysis and 40ar 39ar chronology from anaga basaltic shield volcano on tenerife canary islands support a rift zone flank instability relationship a single rift zone dominated the early stage of the anaga edifice 6 4 5 ma destabilization of the northern sector led to partial seaward collapse at about 4 5 ma resulting in a giant landslide the remnant highly fractured northern flank is part of the destabilized sector a curved rift zone developed within and around this unstable sector between 4 5 and 3 5 ma induced by the dilatation of the curved rift a further rift arm developed to the south generating a three armed rift system this evolutionary sequence is supported by elastic dislocation models that illustrate how a curved rift zone accelerates flank instability on one side of a rift and facilitates dike intrusions on the opposite side our study demonstrates a feedback relationship between flank instability and intrusive development a scenario probably common in ocean island volcanoes we therefore propose that ocean island rift zones represent geologically unsteady structures that migrate and reorganize in response to volcano flank instability

some aspects of the regional variation in the amount of available sediment produced by isopods and porcupines northern negev israel a recent study conducted in the sde boqer experimental site drew the attention to the possible influence of the burrowing and digging activity of some desert animals on the spatial variation of erosion rates over arid limestone slopes such activity provides loose soil aggregates which are easier to remove by shallow overland flows than is the compacted and crusted loessial soil in order to study the regional extent of available sediment amounts produced by the biological activity six plots were selected in the northern negev in the range of 65 mm to 310 mm average annual rainfall amount all plots had the same north facing aspect and the same lithologic composition their size varied from 1110 m2 to 5470 m2 available sediment produced was found to vary from 3 g to 70 g m2 increasing with rainfall amount the distribution of available sediment within each plot was not spatially uniform depending greatly on the spatial distribution of bedrock surfaces and soil cover the overall possible influence of the biotic activity on short term cycles of soil erosion over limestone arid slopes in the negev is discussed

hydrological processes in a small arid catchment scale effects of rainfall and slope length many studies have been concerned with the scale issue in geomorphology and hydrology most studies focus on the possibility of data transfer from small to large watersheds less attention has been given to the scale problem within very small watersheds where differences in slope length may seriously affect the spatial distribution and extent of runoff contributing areas to the channel it is usually assumed that runoff and erosion increase as slope length and angle increase however field observations in the negev highlands show positive relationships between slope length and deposition rates regardless of slope angles short hillslopes are devoid of colluvial mantle while thick colluvial deposits with well developed soil profiles indicative of long term stability are found at the base of long hillslopes the hypothesis advanced is that temporal variations in effective rainfall control the spatial structures of surface properties that further enhance the effects of temporal variations in rainfall long term monitoring of rainfall and runoff 1982 1998 conducted at spatial scales varying from few hundreds of m2 up to 0 3 km2 show a decrease in runoff at the hillslope scale the low efficiency of runoff and erosion processes on long hillslopes is because the concentration time required for continuous flow along such slopes is longer than the duration of most effective rain showers prevailing in the area field data lead to the notion that runoff and erosion models in which a positive relationship between slope length and angle and runoff and erosion rates is assumed should not be applied to arid and semiarid areas more attention should be given in latter areas to the complex hydrological relationships between rainfall scales and spatial scales the implications of data obtained regarding the spatial distribution of areas contributing to channel flow at a geological time scale and under changing climatic conditions are discussed

fossil charcoal as an indicator of palaeoatmospheric oxygen level charcoal results from incomplete combustion of plant material it is produced naturally by wildfire and being relatively tough and unbiodegradable it may be transported and incorporated into a variety of sedimentary environments wildfire requires adequate atmospheric oxygen for the combustion of plant fuel wood leaf litter fossil charcoal from the devonian onwards suggests that the oxygen level in the atmosphere has not fallen below 13 in this interval further the extreme flammability of even wet plant fuel at oxygen levels above 35 makes this the highest figure compatible with the occurrence of terrestrial vegetation

dynamic basis of volcanic spreading the established models of the structure and dynamics of a typical hawaiian volcano lead inevitably to a paradox finite element viscoelastic calculations using tecton melosh and raefsky 1980 1981 predict that a compressional stress field should characterize their upper flanks instead extension is observed the paradox is solved by postulating that volcanic evolution is determined by feedback processes related to growth and spreading of the volcanic edifice many examples of the process of spreading are documented in the geologic literature on volcanoes of a very broad size range and very different geologic settings the process is similar across many orders of magnitude in size the deformation of the substratum related to magma intrusion during lava dome building events is at the lower end of the scale the spreading of seafloor at oceanic ridges is at the higher end of the scale volcanoes may evolve from small constructs into huge shield volcanoes and perhaps into ocean plates key elements for volcanic spreading are 1 the existence of a weak basal layer and 2 a sufficiently high mass and magma influx to drive the process as the mass of a volcano grows it passes through five phases which may overlap repeat or be omitted building compressing thrusting intruding and spreading during the building phase the mass of a volcano does not significantly affect the stress field of the substratum primitive magmas are likely to be erupted as the mass increases the volcano subsides and becomes characterized by a compressional stress field which inhibits any further intrusion of magma into the volcanic edifice magma may differentiate in the crust allowing for large caldera forming eruptions to occur in the next phase thrusting begins on a decollement usually located at the foot of the edifice while the stress field on the upper slopes of the volcano remains compressional the stress at the base close to the center becomes extensional allowing the magma to intrude and differentiate at the base of the edifice a basal intrusive complex begins to grow explosive eruptions may be expected finally spreading of this complex creates an extensional stress field on the upper flanks of the volcano confining compression to the lower slopes of the edifice the extension allows primitive magma to erupt again at the summit the process of spreading seems to have a fundamental influence on the structural and magmatic evolution of volcanoes at every scale this process results from coupling and feedback between the gravitational and thermal fields thus studying this process may improve our understanding of the relation between structural dynamics and magma evolution and of the origin and evolution of volcanic seismicity and eruptions

the origin of mauna loa s nīnole hills evidence of rift zone reorganization in order to identify the origin of mauna loa volcano s n nole hills bouguer gravity was used to delineate density contrasts within the edifice our survey identified two residual anomalies beneath the southwest rift zone swrz and the n nole hills the n nole hills anomaly is elongated striking northeast and in inversions both anomalies merge at approximately 7 km above sea level the positive anomaly modeled as a rock volume of 1200 km3 beneath the n nole hills is associated with old eruptive vents based on the geologic and geophysical data we propose that the gravity anomaly under the n nole hills records an early swrz orientation now abandoned due to geologically rapid rift zone reorganization catastrophic submarine landslides from mauna loa s western flank are the most likely cause for the concurrent abandonment of the n nole hills section of the swrz rift zone reorganization induced by mass wasting is likely more common than currently recognized

three dimensional seismic refraction tomography a comparison of two methods applied to data from the faeroe basin this paper presents a comparison of two tomographic methods for determining three dimensional 3 d velocity structure from first arrival travel time data the first method is backprojection in which travel time residuals are distributed along their ray paths independently of all other rays the second method is regularized inversion in which a combination of data misfit and model roughness is minimized to provide the smoothest model appropriate for the data errors both methods are nonlinear in that a starting model is required and new ray paths are calculated at each iteration travel times are calculated using an efficient implementation of an existing method for solving the eikonal equation by finite differencing both inverse methods are applied to 3 d ocean bottom seismometer obs data collected in 1993 over the faeroe basin consisting of 53 479 travel times recorded at 29 obss this is one of the most densely spaced large scale 3 d seismic refraction experiments to date different starting models and values for the free parameters of each tomographic method are tested a new form of backprojection that converges more rapidly than similar methods compares favorably with regularized inversion but the latter method provides a simpler model for little additional computational expense when applied to the faeroe basin data bounds on two model features are assessed using regularized inversion with combined smoothness and flatness constraints an inversion of synthetic data corresponding to 100 data recovery from the real experiment shows a marked improvement in lateral resolution at deeper depths and demonstrates the potential of currently feasible 3 d refraction experiments to provide well resolved long wavelength velocity models the similarity of the final models derived from the two tomographic methods suggests that the results from the new form of backprojection can be relied on when limited computational resources rule out regularized inversion

imaging the crustal magma sources beneath mauna loa and kilauea volcanoes hawaii three dimensional seismic p wave traveltime tomography is used to image the magma sources beneath mauna loa and kilauea volcanoes hawaii high velocity bodies 6 4 km s in the upper 9 km of the crust beneath the summits and rift zones of the volcanoes correlate with zones of high magnetic intensities and are interpreted as solidified gabbro ultramafic cumulates from which the surface volcanism is derived the proximity of these high velocity features to the rift zones is consistent with a ridge spreading model of the volcanic flank southeast of the hilina fault zone along the south flank of kilauea low velocity material

identification of eroded areas using remote sensing in a badlands landscape on marls in the central spanish pyrenees abstract identification of erosion areas on a regional scale can be very useful for environmental planning and can help reduce land degradation and sediment yield to streams and reservoirs remote sensing techniques were used to determine erosion and erosion risk areas in a badlands landscape in the esera river catchment spanish pyrenees the size sparse vegetation cover and high erosion level in the badlands enabled good visual and digital discrimination relative to other land covers and surfaces the maximum likelihood algorithm was used for obtaining a spectral distance map to the bare soil signature characteristic of badlands on marls the roc receiver operating characteristic curve analysis was applied to this map for obtaining an optimum classification of the badlands two alternative classification thresholds were set to determine erosion areas and areas at risk of erosion two classification performance statistics the model s sensitivity and specificity were calculated as a means of expressing the uncertainty omission and commission errors associated to both maps most erosion risk areas coincided with low vegetation cover surrounding the badland areas

rifting recurrent landsliding and miocene structural reorganization on nw tenerife canary islands we studied mechanisms of structural destabilization of ocean island flanks by considering the linkage between volcano construction and volcano destruction exemplified by the composite teno shield volcano on tenerife canary islands during growth tenerife episodically experienced giant landslides genetically associated with rifting and preferentially located between two arms of a three armed rift system the deeply eroded late miocene teno massif allows insights into the rifting processes the failure mechanisms and related structures the semicircular geometry of palaeo scarps and fracture systems breccia deposits and the local dike swarm reconfigurations delineate two clear landslide scarp regions following an earlier collapse of the older los gigantes formation to the north the rocks around the scarp became fractured and intruded by dikes substantial lava infill and enduring dike emplacement increased the load on the weak scarp and forced the flank to creep again finally resulting in the collapse of the younger carrizales formation once more the changing stress field caused deformation of the nearby rocks a fracture belt formed around the scarp and dikes intruded into new concentric directions the outline size and direction of the second failed flank of teno very much resembles the first collapse we suggest structural clues concerning mechanisms of recurrent volcano flank failure verifying the concept that volcano flanks that have failed are prone to collapse again with similar dimensions

micromorphological fabrics and developmental stages of carbonate nodular forms related to soil characteristics abstract carbonate nodules often constitute the first stage of calcrete formation micromorphological analysis of carbonate nodules and nodular fabrics in different soil materials shows that their development is a function of several factors nature of the host matrix texture porosity carbonate and non carbonate clay distribution bulk density and the interactions among them different micromorphological stages therefore exist in different soil materials in calcareous medium textured soil materials the stages of nodule formation are related to the increase of the density of the nodule caused by the accumulation of microcalcites in such a soil material the following stages occur 1 microcalcites within the low to moderate density matrix 2 microcalcites of moderate to high density and moderately dense diffuse nodules parallel calcans may occur 3 microcalcites of high density with dense microcalcitic nodules during these stages the amount of non carbonate clay decreases but is homogeneously dispersed and disseminated with the microcalcites in general the size of microcalcites 1 8 m is inversely related to the clay content in non calcareous medium to fine textured soil materials secondary carbonate precipitates in intrapedal and or interpedal voids as large sparry crystals due to pedoturbation processes the nodules thus formed are subjected to recrystallization resulting in a microsparry pattern the development stages are 1 few calcans and crystal chambers 2 crystic nodules mainly of sparry crystals and an increase of calcans and crystic chambers 3 recrystallized nodules composed mainly of microspars in coarse grained materials secondary carbonates precipitate directly in voids as sparry crystals and the resulting nodules are of the crystic type the large crystals are often subjected to recrystallization in partly calcareous coarse grained materials with additions of calcareous dust particular micromorphological carbonate forms occur in the c horizon cutanic calciasepic fabric forms besides zones of crystic fabric which gradually become calciasepic in the b horizon and include the typical nodular forms of the calcareous medium textured soil material together with appreciable amounts of glaebular halos the processes leading to the formation of these stages occur essentially without a significant biogenic influence where carbonate segregation occurs as rhizomorphs surrounding active roots the fabric is always micritic even in coarse textural soil material

from plot to regional scales interactions of slope and catchment hydrological and geomorphic processes in the spanish pyrenees the hydrological and geomorphic effects of land use land cover changes particularly those associated with vegetation regrowth after farmland abandonment were investigated in the central spanish pyrenees the main focus was to assess the interactions among slope catchment basin and fluvial channel processes over a range of spatial scales in recent centuries most mediterranean mountain areas have been subjected to significant human pressure through deforestation cultivation of steep slopes fires and overgrazing depopulation commencing at the beginning of the 20th century and particularly since the 1960s has resulted in farmland abandonment and a reduction in livestock numbers and this has led to an expansion of shrubs and forests studies in the central spanish pyrenees based on experimental plots and catchments in large basins and fluvial channels have confirmed that these land use changes have had hydrological and geomorphic consequences regardless of the spatial scale considered and that processes occurring at any particular scale can be explained by such processes acting on other scales studies using experimental plots have demonstrated that during the period of greatest human pressure mainly the 18th and 19th centuries cultivation of steep slopes caused high runoff rates and extreme soil loss large parts of the small catchments behaved as runoff and sediment source areas whereas the fluvial channels of large basins showed signs of high torrentiality braided morphology bare sedimentary bars instability and prevalence of bedload transport depopulation has concentrated most human pressure on the valley bottoms and specific locations such as resorts whereas the remainder of the area has been affected by an almost generalized abandonment subsequent plant recolonization has resulted in a reduction of overland flow and declining soil erosion at a catchment scale this has caused a reduction in sediment sources and channel incision in the secondary streams at the regional scale the most important consequences include a reduction in the frequency of floods reduced sediment yields increasing stabilization of fluvial channels colonization of sedimentary bars by riparian vegetation and a reduction in the braiding index and stabilization of alluvial fans these results demonstrate the complexity and multiscalar nature of the interactions among land use and runoff generation soil erosion sediment transport and fluvial channel dynamics and highlight the need to adopt a multiscale approach in other mountain areas of the world

terrestrial laser scanning soil surfaces a field methodology to examine soil surface roughness and overland flow hydraulics smith m w cox n j bracken l j 2011 terrestrial laser scanning soil surfaces a field methodology to examine soil surface roughness and overland flow hydraulics hydrological processes 25 6 842 860

a review of charcoal analysis as a tool for assessing quaternary and tertiary environments achievements and limits abstract identification of charcoal fragments 2 mm using reflected light microscopy is routinely carried out to study former natural ecosystems assess changes in vegetation communities over time and identify the influence and patterns of behaviour of human populations on vegetation material studied comes either from archaeological horizons or soil profiles despite undeniable limits informative results have been obtained in the last 25 years mostly in southwestern europe where charcoal analysis has been widely applied in quaternary studies examples of these achievements are provided focusing on the major vegetation trends since the upper palaeolithic to the middle ages the techniques used for charcoal analysis in the reconstruction of quaternary vegetation are now being used to study tertiary charcoal and lignites the study of fossil charcoal can be a highly informative method for interpreting ancient ecosystems as species easily degraded may be preserved by charcoalification some results from the lower rhine embayment germany are presented here

spatial distribution of surface properties runoff generation and landscape development in the zin valley badlands northern negev israel in ltration tests soil mapping and soil property analysis were used to assess the effect of within storm rainfall conditions on spatial patterns of surface characteristics relevant for runoff generation continuity and erosion in the zin valley badlands runoff and erosion differ strongly between ridges and slopes soils at both locations are susceptible to sealing but on the sideslopes deep desiccation cracks inhibit continuous ow even during high magnitude rainstorms the discontinuous nature of runoff has a feedback on surface conditions erosion on the ridges maintains shallow soils prone to sealing while in ltration and deposition on the sideslopes enhance soil depth a prerequisite for stable desiccation cracks some runoff generated on the ridges is transmitted to the valley via rills on straight sideslopes rills are single and often discontinuous indicating limited frequency of continuous runoff along concave valley heads rill systems are well integrated and continuous concentrating runoff and reducing in ltration losses along slopes the longitudinal v shaped valley morphology of small catchments in the zin valley badlands re ects the long term effect of different erosion rates in valley heads and on sideslopes over time valley incision lengthened the sideslopes reducing the portion of annual rainfall that was runoff effective once sideslopes reached a critical length that inhibited frequent continuous ow a colluvium with an increased in ltration capacity developed reducing runoff frequency even further consequently erosion on the valley sideslopes decreased continuous ow from ridges to the valley channel remained more common in integrated rill systems in concavities and valley heads leading to more erosion and retreat of the valley heads the spatial patterns of runoff and erosion in the zin valley badlands demonstrate that landscape development is strongly affected by processes that lead to differentiation of soil properties on hillslopes with uniform lithology the patterns of surface characteristics and their role in landscape development are strongly dependent on rainfall conditions highlighting the need for geomorphologists to identify the dynamic spatial and temporal scales relevant for landscape development copyright 2004 john wiley sons ltd

new insights about the climatic and geologic control on the probability distribution of floods an application of the theoretically based distribution of floods recently derived by iacobellis and fiorentino 2000 was carried out with the aim of analyzing the climatic and geologic control on the distribution itself in particular 20 basins in a wide area of southern italy were considered these basins were classified by the use of a climatic index i depending on the average annual rainfall and on the potential evapotranspiration this index takes positive values in humid climates and negative values in dry zones with regard to the geology attention was paid to the watershed permeability during intense storms in each basin the pervious area was estimated after identification of three permeability classes the analyses demonstrated that the sign of the climatic index strongly discriminates the behavior of both the parameters a and e a the former representing for each basin the characteristic total abstraction rate and the latter being the expected value of the basin area contributing to the flood peak in dry zones a was found to decrease with increasing a and the ratio r e a a tended to decline linearly as the percentage of pervious areas increased on the contrary in humid zones the basin area did not seem to have any effect on a which was instead particularly sensitive to the climatic index moreover in these zones the parameter r was steadily low without showing any significant dependence on climate geology and morphology of the basin in this paper an interpretation of these results is indeed provided

an integrated analysis of the march 2015 atacama floods in march 2015 unusual ocean and atmospheric conditions produced many years worth of rainfall in a 48 h period over northern chile s atacama desert one of earth s driest regions resulting in catastrophic flooding here we describe the hydrologic and geomorphic drivers of and responses to the 2015 atacama floods in the salado river we estimated a flood peak discharge of approximately 1000 m3 s which caused widespread damage and high sediment loads that were primarily derived from valley fill erosion hillslopes remained surprisingly intact despite their lack of vegetation in the coastal city of chanaral flooding of the salado river produced maximum water depths over 4 5 m meters thick mud deposition in buildings and along city streets and coastal erosion the atacama flooding has broad implications in the context of hazard reduction erosion of contaminated legacy mine tailings and the atacama s status as a terrestrial analog for mars

the burrowing activity of scorpions scorpio maurus palmatus and their potential contribution to the erosion of hamra soils in karkur central israel abstract the burrowing activity of the scorpion scorpio maurus palmatus was studied on a 1200 m 2 slope of a so called hamra sandy soil in karkur israel the main results were 1 the scorpions excavate soil material after rain storms preparing this material for erosion processes by rain splash and rainwash 2 the burrowing activity stops in the dry summer and during cold days of the winter this means that scorpio maurus palmatus is preparing soil for erosion from one storm to the next and not from one season to the next as was previously thought further it was found that the amount of soil material excavated from the burrow is proportional to the size of the scorpion and that most of the mounds were deposited toward the upper part of the slope which means that part is washed back into the burrow itself

the nature and influence of fire in carboniferous ecosystems fusain occurs widely in carboniferous coals and sediments it is now recognised to represent charcoal and be the product of wildfire the occurrence of fire is partly constrained by atmospheric oxygen levels availability and nature of fuel and by aspects of climate rainfall and seasonability in particular the majority of fires in the carboniferous were probably started by lightning strikes or by volcanic activity experiments on the charring of modern plants has shown that the reflectance of charcoal and hence fusain is directly related to temperature of formation different fire types may yield fusain assemblages of differing reflectance spectrums but it may be significant that many modern charcoal assemblages yield only semifusinites as seen by reflectance microscopy the significance of these findings is assessed in relation to the use of fusinites and semifusinites as depositional indicators as interpreted from coal petrology fires may have a dramatic effect on ecosystems not only causing changes in vegetational succession but also severe erosion can occur following a major fire which can be traced in depositional systems in this paper we document three major carboniferous sedimentary systems affected by fire clastic sedimentary systems using extensive fusain deposits in mid lower carboniferous near shore sediments in donegal ireland volcanic systems using late early carboniferous volcaniclastic sequences in the midland valley of scotland and coal and coal bearing sequences in the upper carboniferous westphalian b of the pennine basin england in the later settings the influence of fire in peat formation and succession is assessed in addition data on the vegetational composition of charcoal assemblages is considered it is concluded that fire plays a major role in many carboniferous ecosystems

first known fire scar on a fossil tree trunk provides evidence of late triassic wildfire abstract fire scars are well known to fire ecologists and dendrochronologists worldwide and are used in dating fires and reconstructing the fire histories of modern forests evidence of fires in ancient forests such as fossil charcoal fusain is well known to paleontologists and has been reported in geologic formations dating back to the late devonian we describe what we conclude is a fire scar on a fossil tree trunk from the late triassic chinle formation of southeastern utah 200 225 ma the external features of the prehistoric scar match those of modern fire scars better than those of scars created by other kinds of wounding events the fossil specimen also exhibits a number of changes in wood anatomy similar to those reported in modern fire scarred trees including a band of very small tracheids that indicate growth suppression immediately associated with the scarring event an area with a tangential row of probable traumatic resin ducts and a significant increase in tracheid size following the scarring event that indicates a growth release no fire scar resembling those in modern trees has previously been described in petrified wood as far as we can determine the presence of a fire scar not only provides further evidence of ancient fires but also shows that at least some individual trees survived them indicating that fire could have been an ecological and evolutionary force in forests at least as early as the late triassic

morphological characterization of soil crust development stages on an experimental field abstract crust development on a loamy aquic hapludalf near paris was studied in an experimental field to which various fertilizers and amendments had been applied these treatments over a period of 57 years had induced a range of organic matter contents and exchangeable cation percentages the macroscopic aspects of the soil surface was closely monitored during crusting and microscopic characterization was carried out at every main crust development stage crusting followed a general pattern 1 sealing of the soil surface by a structural crust 2 development of a depositional crust even in the sodic plot where the depositional crust appeared especially early the structural crust developed first the change from the first stage to the second one mainly depended on a decrease in infiltrability due to the structural crust properties that induced micro runoff and puddling under rainfall structural crust development seemed to involve a coalescing process due to raindrop impact when moistening decreased soil cohesion this process developed much faster in the sodic than in the limed plot morphology of the depositional crust in particular microbedding and sorting could be related to the hydrodynamic behaviour of the soil surface abundance size and duration of puddles

stress field interactions between overlapping shield volcanoes borehole breakout evidence from the island of hawai i usa acknowledgments this pta2 borehole investigation was funded by the international continental scientific drilling program icdp and by vmapp volcanic margin petroleum prospectivity project vbpr dougalearth tgs in collaboration with the humu ula groundwater research project d a j and s p are partly funded through a norwegian research council centres of excellence project project number 223272 ceed we thank marco groh for the logging operations we thank two anonymous reviewers for the comments and suggestions we are particularly grateful to the associate editor mike poland for his valuable comments and his critical review that greatly improved the manuscript

rift zone abandonment and reconfiguration in hawaii mauna loa s ninole rift zone a new onshore offshore three dimensional seismic velocity model for the island of hawaii reveals a massive buried rift zone within mauna loa9s southeast flank introduced here as the ninole rift zone this feature extends more than 60 km south of mauna loa9s summit spans a depth range of 2 14 km below sea level and is the probable source of the 100 200 ka ninole volcanics in several prominent erosional hills the ancient rift zone may stabilize mauna loa9s southeast flank focusing recent volcanic activity and deformation onto the unbuttressed west flank the upper portion of the ninole rift zone appears to have migrated westward over time possibly triggered by landsliding causing its eventual abandonment in preference to mauna loa9s present day southwest rift zone subsequently the lower southwest rift zone broke away tracking rift intrusions along the trace of the kahuku detachment fault similar rift zone migration is thought to be under way at kilauea volcano and may one day lead to the abandonment of the east rift zone such rift zone reconfiguration is a reflection of changing stress conditions within growing volcanoes it is probably much more common than previously assumed and may enable the growth of large volcanic edifices such as mauna loa

sediment budget of high mountain stream channels in an arid zone high atlas mountains morocco abstract in an arid zone the sediment budget is predominantly dependent on runoff which is controlled mainly by the type of rainfall sediment budget calculation is one of the indirect methods of estimating channel morphodynamics this method is advised here since it is not possible to directly measure this important hydrological indicator of environmental dynamics this is because in small mountain catchments of an arid zone it is impossible to obtain flow rates due to factors such as the amount and size of transported rock debris as well as the episodic and sudden nature of precipitation events the research was conducted in 3 catchments 2 95 km2 7 39 km2 22 73 km2 situated within the boundaries of the basin of the upper dades on the southern slopes of the high atlas in morocco the rivers of these catchments tributaries to a trunk river dades are ephemeral and mostly bedrock depending on lithology of the geology three automatic weather stations were installed there precipitation events 10 mm 51 rains in 3 catchments were used in the analysis simple rainfall typology 3 types was devised for these events during the research period seasonally repeated 6 times measurements of topography were obtained from 21 cross section profiles of streams of different order these measurements formed a basis for calculating both the intensity of flow in ephemeral rivers max 69 6 m s and the sediment budget in 70 of analysed channel cross sections erosion was dominant the average change of the surface area of the cross section profile is 82 the maximum seasonal between measurements enlargement of the surface cross section erosion is as high as 128 the lower catchment which is predominantly composed of conglomerates distinctly shows the slightest changes of the cross section profile surfaces max 24 the average volume of channel material displaced at the measurement point is 1 07 m3 max 9 81 m3 there is evidence that not only high intensity rains but also less intense but longer lasting rains amounting to high precipitation totals type c may result in the highest channel sediment budgets differences between a catchment lithology composed of limestones and marlstones and that composed of conglomerates have only a minor impact on sediment budgets in the first and second order channels whereas in the channels of the third and fourth order this impact is much higher it was found that sediment budgets calculated for individual channels were higher for the catchments composed of limestones and marlstones than for those composed of conglomerates even though the catchments of different lithology may have had the same number of tributaries this suggests that the sediment supply from slopes is comparatively larger in the catchments dominated by limestones and marlstones

40ar 39ar geochronology of submarine mauna loa volcano hawaii 1 new geochronologic constraints refine the growth history of mauna loa volcano and enhance interpretations of the petrologic geochemical and isotopic evolution of hawaiian magmatism we report results of 40ar 39ar incremental heating experiments on low k tholeiitic lavas from the 1 6 km high kahuku landslide scarp cutting mauna loa s submarine southwest rift zone and from lavas in a deeper section of the rift obtaining precise40ar 39ar ages from young tholeiitic lavas containing only 0 2 0 3 wt k2o is challenging due to their extremely low radiogenic 40ar contents analyses of groundmass from 45 lavas yield 14 new age determinations 31 success rate with plateau and isochron ages that agree with stratigraphic constraints lavas collected from a 1250 m thick section in the landslide scarp headwall were all erupted around 470 10 ka implying an extraordinary period of accumulation of 25 mm yr possibly correlating with the peak of the shield building stage this rate is three times higher than the estimated vertical lava accumulation rate for shield building at mauna kea 8 6 3 1 mm yr based on results from the hawaii scientific drilling project between 470 and 273 ka the lava accumulation rate along the southwest rift zone decreased dramatically to 1 mm yr we propose that the marked reduction in lava accumulation rate does not mark the onset of post shield volcanism as previously suggested but rather indicates the upward migration of the magma system as mauna loa evolved from a submarine stage of growth to one that is predominantly subaerial thereby cutting off supply to the distal rift zone prior to 250 ka lavas with loihi like isotopic signatures were erupted along with lavas having typical mauna loa values implying greater heterogeneity in the plume source earlier in mauna loa s growth in addition to refining accumulation rates and the isotopic evolution of the lavas erupted along the southwest rift zone our new40ar 39ar results constrain the eruption of the ninole basalts from 227 to 108 ka and provide maximum estimates on the timing of the ka lae and south kona landslides

the role of topography and surface cover upon soil formation along hillslopes in arid climates abstract two north facing soil toposequences were selected from within the northern negev desert israel where average annual rainfall ranges from 70 to 200 mm both slopes are composed of an upper rocky and a lower colluvial section similar trends were found along both slopes a high salt content was characteristic of soils at the top of the slope salinity decreased downslope within the rocky slope section the opposite occurred along the colluvial slopes with salinity increasing sharply downslope at any location along the slopes the northernmost soil toposequence site 160 mm average annual rainfall represents from a pedological point of view an environment which is far more arid than its climatologically drier more southern counterpart the explanation provided for the variation of soil proporties at the scale of single hillslopes and at the regional scale is the same it is contended that water input into the soil and therefore leaching intensity is positively related to the ratio of bedrock soil cover rocky areas have limited infiltration thus yielding high runoff rates into adjoining soil covered areas and contribute to water concentration deeper infiltration and leaching intensity soil or sediment covered areas having relatively high absorption capacities will experience reduced runoff shallow infiltration and decreased water availability for leaching this leads over time to salt accumulation at a shallow depth the decrease in rock soil ratio downslope within the colluvium is therefore held responsible for the corresponding increase in salinity similarly the greater salinity of the soils in the northern site is explained by the fact that its rock soil ratio is lower than in the southern area the theoretical and practical implications regarding the relationship between climatic change and landscape evolution in arid areas are briefly discussed