the sedimentary structure of linear sand dunes linear sand dunes dunes that extend parallel to each other rather than in star like or crescentic forms are the most abundant type of desert sand dune1 but because their development and their internal structure are poorly understood they are rarely recognized in the rock record2 models of linear dune development2 3 4 5 6 have not been able to take into account the sub surface structure of existing dunes but have relied instead either on the extrapolation of short term measurements of winds and sediment transport or on observations of near surface internal sedimentary structures from such studies it has not been clear if linear dunes can migrate laterally2 7 8 here we present images produced by ground penetrating radar showing the three dimensional sedimentary structure of a linear dune in the namib sand sea where some of the world s largest linear dunes are situated these profiles show clear evidence for lateral migration in a linear dune moreover the migration of a sinuous crest line along the dune produces divergent sets of cross stratification which can become stacked as the dune height increases and large linear dunes can support superimposed dunes that produce stacked sets of trough cross stratification these clear structural signatures of linear dunes should facilitate their recognition in geological records

seven landslide dams of old seismic origin in southeastern sicily italy this paper focuses on origin morphology and evolution of seven landslide dams in southeastern sicily these landforms are part of a set of 146 landslides recently recognised in this area which was hitherto considered to have little or no slope instability southeastern sicily consists of a plateau the hyblaean mountains incised by canyons and surrounded by lower lands it is underlain mostly by subhorizontal moderately to well lithified carbonate rocks relief is low several lines of evidence justify the assumption of a seismic trigger for the landslides in this area 1 the geo climatic environment is not favourable to landsliding 2 low angle basal shear surfaces are very frequent 3 landslide distribution is consistent with the known magnitude distance relationships for earthquake induced landslides 4 historical documents testify to earthquake triggered slope instability and 5 a specific landslide can be exactly dated the phenomena illustrated here include six rock slides one with a debris flow component and one rock fall slip surfaces are mostly non circular landslide volume ranges from about 5010 3 to 3410 6 m 3 with reference to the costa and schuster geol soc am bull 100 1988 1054 classification of landslide dams five cases belong to type ii spanning the entire valley and two to type iv failures from both valley sides with frontal or side contact between failed masses with reference to crozier and pillans catena 18 1991 471 classification of landslide lakes all cases show a main valley lake while tributary valley back and supra lakes are sporadically present one damming is attributable to the 1693 earthquake with certainty another damming to the same earthquake with high probability three dams were reincised one breached or reincised one is slightly reincised and two more or less intact correspondingly five silting up deposits were reincised one is being reincised at present and two are still under formation d 2002 elsevier science b v all rights reserved

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

effect of slope failures on river network pattern a river piracy case study from the flysch belt of the outer western carpathians abstract landslides are important geomorphic agents in various mountainous settings we document here a case of river piracy from the upper part of the mala brodska valley in the vsetinske mts czech republic raca unit of the flysch magura group of nappes flysch belt of the outer western carpathians controlled by mass movement processes based on the field geological geomorphological and geophysical data we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley apart from the landslide processes the presence of the n striking fault accentuated by higher flow rates of the eastern channel as a result of its larger catchment area were the most critical factors of the river piracy as a consequence of the river piracy intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred deposits of two landslide dams document recent minimum erosion rates to be 18 8 mm ky 1 in the western captured catchment and 3 6 mm ky 1 in the eastern catchment respectively the maximum age of the river piracy is estimated to be of the late glacial and or the early holocene

temporal and spatial variability in dune reactivation across the nebraska sand hills usa the nebraska sand hills is a stabilized dune field on the great plains of north america although it is well known that this dune field like several others on the great plains last experienced widespread activity during the medieval climatic anomaly mca ad 900 1300 spatial variation in the timing and nature of drought development is poorly constrained to elucidate spatial trends in dune reactivation samples potentially representing mca activity across the sand hills were collected and dated using optically stimulated luminescence osl ages from the older part of the mca were obtained from eolian sediments in the northwestern sand hills while ages from later in the episode were obtained to the southeast suggesting a geographic trend in the timing of revegetation of the dunes near the end of the drought revegetation likely occurred to the northwest initially as a result of renewed moisture availability from a rising water table in the interdunes which serve as refugia for vegetation during times of drought vegetation then gradually spread to the southeastern sand hills an additional spatial trend in ages is apparent in the chronology of linear dune mobilization across the sand hills linear dunes in the northwest are superimposed on megadunes and originated during the last reactivation while linear dunes in the southeast are built around older cores of dunes and formed during several reactivations our geochronology reveals three episodes of eolian transport including the mca in the formation of linear dunes in the southeast

depth imaging of basalt flows in the faeroe shetland basin summary we use a grid of long offset seismic profiles to map the thickness of subsurface basalt flows that extend southeastward across the faeroe shelf offsets of up to 38 000 m were achieved using two seismic acquisition vessels towing multichannel streamers and shooting alternately wide angle reflections and refractions from the basalt and underlying strata allow us to build a velocity model down to the basement lewisian crust the velocity models give a first order picture of the geology of low velocity sediments of presumed early palaeocene and mesozoic age beneath the basalt flows they also provide a control for pre stack depth migration of the entire seismic data set thus allowing us to produce good depth images of the structure pre stack depth migration of selected wide angle arrivals such as those from the base of the basalt and the underlying basement produce strong reflection images that allow these interfaces to be identified unambiguously on the higher resolution images produced from the entire data set in particular we can distinguish between the primary and multiple reflections we thus use the very long offset arrivals to tag the velocities of the geological interfaces from which they are returned and hence to improve both the imaging and the interpretation of the basalt flows and the underlying structure

giant landslide triggerings and paleoprecipitations in the central western andes the aricota rockslide dam south peru abstract the central part of the western andes holds an exceptional concentration of giant paleolandslides involving very large volumes of rock material v km3 while those gravitational slope failures are interpreted consensually as an erosional response to the geodynamic activity of the andes relief formation and tectonic activity the question of their triggering mechanisms remains enigmatic to clarify the respective roles of climatic versus seismic forcing on the andean landslides new temporal constraints on paleo movements are essential here we focus on one of those giant slope failures the aricota giant rockslide that damned the locumba valley in southern peru we conducted fieldwork high resolution dem analysis and cosmogenic nuclide dating to decipher its development history and failure mechanisms our results point to the occurrence of two successive events a giant failure mobilizing a rock volume of ca 2 km3 first produced a dam at 17 9 0 7 ka considering its height of ca 600 m the aricota rockslide dam is one of the three largest landslide dams worldwide at 12 1 0 2 ka a second event produced ca 0 2 km3 of material and the rock avalanche debris spread out over the dam as the chronology of those two events is pointing to the two main paleoclimatic pluvial periods in this region heinrich stadial 1a and younger dryas we favor the interpretation of a climatic forcing at a regional scale the concomitant aggradation of alluvial terraces and fan systems along the nearby valleys highlights higher regional erosion sediments supply and mass wasting events during those paleoprecipitation events and strengthens this conclusion

morphometric analysis of aeolian bedforms in the namib sand sea using aster data the aster global digital elevation model gdem has made elevation data at 30 m spatial resolution freely available enabling reinvestigation of morphometric relationships derived from limited field data using much larger sample sizes these data are used to analyse a range of morphometric relationships derived for dunes between dune height spacing and equivalent sand thickness in the namib sand sea which was chosen because there are a number of extant studies that could be used for comparison with the results the relative accuracy of gdem for capturing dune height and shape was tested against multiple individual aster dem scenes and against field surveys highlighting the smoothing of the dune crest and resultant underestimation of dune height and the omission of the smallest dunes because of the 30 m sampling of aster dem products it is demonstrated that morphometric relationships derived from gdem data are broadly comparable with relationships derived by previous methods across a range of different dune types the data confirm patterns of dune height spacing and equivalent sand thickness mapped previously in the namib sand sea but add new detail to these patterns

tilt depth method a simple depth estimation method using first order magnetic derivatives aeromagnetic data are routinely presented as contour or color shaded maps of the total magnetic intensity tmi an interpreter s task is to identify features anomalies contained within the map and qualitatively and or quantitatively interpret them into geologic structures at depth if the map contains anomalies that have large magnetic intensities the bodies might be considered to have large magnetizations or to be at shallow depths small amplitude anomalies superimposed on these anomalies could be masked or even missed by an interpreter thus the task of the interpreter is to use the spectral content of the anomalies to try and resolve these ambiguities part of this process is also to obtain estimates of the depth and shape of the body causing the anomalies

a twenty one year record of surface change on a namib linear dune repeated surveying of two sites on a namib linear dune between 1980 and 2001 provides a 21 year record of dune surface change the surveys con rm the view that the dunes are not inactive relics but are responding to the present day wind regime they also provide no evidence that the dunes are migrating laterally examination of wind data for the survey period provides some evidence that the form of the crest of the dunes is actively responding to the natural year by year climate variability such that an increase in the frequency of easterly winds leads to the development of a double crested form while fewer easterly winds lead to a single crested form copyright 2003 john wiley sons ltd

rift related magmatism on magma poor margins structural and potential field analyses of the mesozoic notre dame bay intrusions newfoundland canada and their link to north atlantic opening abstract the magma poor newfoundland margin formed following lithospheric stretching rifting and breakup resulting in the separation of the grand banks from iberia and northern newfoundland from ireland mesozoic igneous rocks contemporaneous with rifting have been documented on and offshore newfoundland with later offshore magmatism occurring post breakup the notre dame bay magmatic province ndbmp is a jurassic cretaceous potentially rift related occurrence of igneous rocks onshore newfoundland that includes the gabbroic budgell harbour stock bhs and marginal lamprophyre dykes in addition to the nearby potentially related dildo pond intrusion dpi and leading tickles stock lts although the bhs is penetrated by wells it is poorly exposed at surface and the deeper structure remained unknown here results of field based mapping combined with inversion of full tensor gradiometry ftg and aeromagnetic data covering the bhs are presented although the ftg data are of a higher resolution than the magnetic data comparable results were obtained from these independent datasets we found that the dykes form clusters at the ends of density and susceptibility anomalies interpreted to be lobe like magmatic conduits furthermore potential field analysis has revealed the irregular geometry and southward dipping nature of the bhs in addition to the presence of multiple near surface anomalies that may correspond to dyke clusters or other igneous bodies structural analysis indicates that emplacement of the dykes was controlled by pre existing geological structures and that they have probably been deformed post intrusion potentially via the reactivation of pre rift faults the potential field investigations and observations of dyke margin lineations from field based structural analysis indicate that multiple dyke sources and bodies similar to the bhs may also exist finally this study demonstrates that magma poor margins such as the newfoundland margin may host significant volumes of extension related magmatic rocks challenging the concept of a distinction between magma rich and magma poor rifting

sedimentary architecture of an ancient linear megadune barremian neuquen basin insights into the long term development and evolution of aeolian linear bedforms linear aeolian bedforms are the most abundant bedform type in modern earth sand seas and are very common in our solar system despite their abundance the long term development of these bedforms and its impact upon the resulting sedimentary architecture in the geological record is still poorly understood the aims of this paper are to study the exposed record of an ancient linear megadune in order to discuss the factors that impact the development and sedimentary architecture of aeolian linear bedforms the outcrops of the ancient troncoso sand sea barremian neuquen basin argentina provide a unique opportunity to access a preserved megadune record with an external body geometry that unequivocally confirms its linear morphology architectural analysis of the bedform record reveals significant differences for several aspects of cross stratified set bodies and bounding surfaces and allows for the identification of three architectural complexes insights from deterministic models analysis of set body relative chronology and distribution suggest that complexes result from distinctive phases in bedform development it also clearly shows that the megadune s construction was achieved by expansion from a core where the oldest deposits are located and that its development was characterized by sustained growth and strong longitudinal dynamics factors that impact the development and architecture of linear bedforms are identified discussed and compared to bedforms of transverse dynamics finally a scheme of expected styles of sedimentary architecture for linear bedforms is presented this case study shows how growth can be a critical factor conditioning linear bedform architecture and indicates how the preservation of certain styles of sedimentary architecture in the geological record may not be as unusual as previously thought

lateral migration thermoluminescence chronology and colour variation of longitudinal dunes near birdsville in the simpson desert central australia the longitudinal dunes of the simpson desert in the vicinity of birdsville have been reworked largely during the holocene from dunes deposited up to 80000 years ago or earlier the widespread asymmetry of these roughly northward trending dunes with steeper eastern faces and more gentle western faces supports wind rose data showing sand transporting winds from the southwest obliquely intersecting the dunes while this suggests a change in the wind pattern since the dune field was oriented it does not indicate that the dunes are necessarily shifting leeward eastward as a consequence it is hypothesized that the direction of migration is controlled by the extent to which the dunes are vegetated relatively well vegetated dunes can accrete sand on their gentle stoss slopes and erode on their lee slopes causing them to shift westward and hence obliquely into the wind a condition that probably prevails in wetter regions and during episodes of relatively humid climate in contrast in very dry areas or during arid phases sand can move unimpeded up a sparsely vegetated stoss face and over the crest to form an avalanche or slip face on the lee side thereby causing the dunes to shift eastward despite evidence that longitudinal dune crests can shift laterally to some extent the dunes in the western part of the simpson desert have not migrated either westward or eastward more than 100m or so from their pleistocene cores aeolian transport and partial or complete removal of iron cutans from around quartz grains results in dunes of widely varying colour yet of similar age

a decade of surface change on a namib linear dune survey data from return visits to a linear dune in the namib desert provide information about change in dune form over a decade the data demonstrate that although change on these large features is slow there is none the less considerable movement over this time scale the dunes are therefore confirmed to be currently active and not pleistocene relics

late pleistocene eolian history of the liwa region arabian peninsula the liwa region of the united arab emirates is one of the most distinctive geomorphological features of the rub al khali desert of southern arabia characterized by a sharp crescentic boundary coincident with a n s elevation drop of 65 m with the transverse ridges in al q fa to the north liwa is an area of some of the world9s largest megabarchan dunes deep drilling of continuous cores has provided an opportunity to observe the internal structure and age of these two ergs subsurface stratigraphy is complex reflecting rapid facies transitions between dune and interdune sub environments most of the cored sediment is dominated by cross bedded and structureless sand units of inferred eolian transverse dune depositional origin a total of 56 optical ages for sand sized quartz grains extracted from these cores provide a chronological framework for deposition of the late quaternary ergs a marine isotope stage mis 5 erg is identified north of the liwa crescent in the al q fa region which reaches vertical thicknesses 100 m a mis 1 erg in the form of megabarchan dunes is recorded south of the liwa crescent this was deposited on a pre mis 5 land surface since ca 6 ka over a period of just a few thousand years contemporary bypassing of eolian sands via superimposed dunes in both al q fa and liwa appears to be in equilibrium with the current wind regime a consideration of a variety of factors that control the availability mobilization and preservation of eolian sediments and resulting bedforms leads us to infer that the system is not sediment supply or transport limited instead the system is preservation limited being controlled by a correlated combination of sea level and precipitation both of these factors are strongly linked to global climate variations in the eccentricity ca 100 ka band paradoxically the bulk of the preserved record of eolian activity in the southern arabian peninsula occurs within relatively humid interglacial phases rather than arid intervals evidence of eolian deposition during arid phases may not for the most part be preserved in large areas of the sand sea observed contrasts in the preserved record of eolian activity between al q fa and liwa and the wahiba sand sea may in part relate to contrasting eolian bedform morphology

late quaternary linear dune accumulation and chronostratigraphy of the southwestern kalahari implications for aeolian palaeoclimatic reconstructions and predictions of future dynamics abstract the linear dunes of the kalahari now largely inactive have long been identified as having potential palaeoenvironmental significance the application of optically stimulated luminescence osl dating to these dunes in the 1990s provided the first chronology of aeolian accumulation in this region though field methodologies and time consuming multiple aliquot laboratory protocols limited both the depth of sampling in dune bodies and the total number of samples dated in order to permit a more thorough investigation of the potential of these dunes to preserve long chronological records this intensive study presents 71 osl ages from the linear dunes of the southwestern kalahari at witpan south africa sampled with coring equipment at regular and frequent intervals down to bedrock the earliest sand accumulation recorded at witpan is at 104 ka and in spatially discrete locations other evidence of dune activity is recorded at 77 76 57 52 and 35 27 ka although an inherently discontinuous archive the linear dunes of the southwestern kalahari have the potential to record multiple phases of dune construction following the last glacial maximum there is near continuous evidence of dune building with a peak of accumulation recorded from 15 to 9 ka at five individual sites this latter period is generally recognised from other proxy evidence as being unusually arid in this region and such periods of dune activity are likely to be related to intensification of the continental anticyclone during the holocene accumulation has continued at most sites sampled albeit at a lesser intensity this may imply that these dunes are presently not far from thresholds of activation

formation of landslide dammed lakes during a wet period between 40 000 and 25 000 yr b p in northwestern argentina abstract new ams radiocarbon data from the deposits of landslide dammed lakes in the santa maria basin 26 s 66 w and the quebrada del toro 25 s 66 w in the eastern argentine cordillera show that important mass movements occurred during a wet period between 40 000 and 25 000 yr b p in addition to increased humidity during this time detailed analysis of annual layered lacustrine strata suggests enhanced inter and intra annual fluctuations in precipitation as compared to the present variations in sediment characteristics and diatom assemblages with mean periodicities of 2 to 5 and 10 to 14 years respectively suggest an influence of the el nino southern oscillation enso and the atlantic sea surface temperature dipole the atlantic dipole slightly increased rainfall every 10 14 years as at present in contrast the weak modern enso influence in this area differs from the past situation where rainfall increased significantly with enso type periodicities both increased humidity and seasonality are believed to have reduced thresholds for the generation of catastrophic mass movements in northwestern argentina

lateral migration of linear dunes in the strzelecki desert australia linear dunes in the strzelecki desert trend roughly south north sand transport which is toward the nne has caused the dunes to migrate eastward while they extend or migrate northward eastward lateral migration is evidenced by 1 asymmetrical shape of the dunes east facing slopes are several times as steep as west facing slopes 2 asymmetrical accumulation of loose recently transported sand relatively abundant on east facing slopes 3 asymmetrical outcropping of older semiconsolidated aeolian sand on the dune surface more abundant on west facing slopes and 4 east dipping foreset beds that underly the west facing flanks of some dunes dunes in the strzelecki desert are still active in the sense that sand is transported along and across many dune crests however the dunes are composed primarily of pleistocene strata indicating that the trend of the dunes was established before the holocene the obliquity of the dunes to the transport direction is not merely an aberration of the wind regime of the last few decades preferential accumulation of sand on east facing flanks indicates that the dunes migrated eastward several metres during the holocene moreover the west facing flanks of some dunes have experienced a minimum of tens of metres of erosion this asymmetric erosion and deposition were caused by dune obliquity and lateral migration that may have begun as early as the pleistocene dunes in the strzelecki desert and in the adjacent simpson desert display a variety of grossly different internal structures computer graphics experiments demonstrate that many of these differences in structure can be explained by different angles of climb of the dunes

longitudinal dunes can move sideways longitudinal dunes occur in all major sand areas in the world their dominant mode of migration or extension is considered to be either prevailing or resultant wind parallel the dunes extending downwind via accretion of the terminal nose in the qaidam pendi in northwest china a series of active longitudinal dunes extend downwind at 5 10 m yr 1 internal sedimentary structures examined in the dunes however display beds dipping in one direction rather than two opposed directions as is expected analysis of aerial photographs confirms that these dunes migrate laterally up to three metres per year whilst maintaining a symmetrical longitudinal dune morphology

forecasting where larger crustal earthquakes are likely to occur in italy in the near future a forecast of future occurrences of larger m 5 9 crustal earthquakes in italy is made on the basis of historic and instrumental seismicity and following a seismotectonic regionalization recently derived on the basis of geological evidence combined with earthquake epicenters and focal mechanisms completeness problems in the seismic catalog allow one to study only 20 regions out of 58 large crustal seismicity within each seismogenic region is modeled as either a periodic gauss process or a random poisson process according to the experimental coefficient of variation of the series of past occurrences in each region return times are estimated directly from the series of m 4 5 earthquakes if they are sufficient in number or from the gutenberg richter law applied to lower magnitude seismicity m 4 5 otherwise the immediate probability of an m 5 9 crustal seismic event is esti mated to be very low in all regions except southeastern sicily and appennino abrnz zese in the near future next 20 yr the estimated probability is high above 65 also in the appennino forlivese and naso capo d orlando regions in addition to detailed seismic risk reevaluations these regions represent the best bet for a program of intensive monitoring to gather a record of the process of strain accumulation and seismic release

stability of landslide dams and development of knickpoints the wenchuan earthquake triggered many landslides and numerous avalanches and created 100 odd quake lakes the quake lakes may be removed or preserved the removal strategy was applied to several large landslide dams which were dangerous because massive amounts of water pooled up in the quake lakes the dams could eventually fail under the action of dam outburst flooding potentially endangering the lives of people in the downstream reaches this paper studied the stability of landslide dams and the development of knickpoints by field investigations and experiments and analyzing satellite images the study concluded that if landslide dams were preserved they would develop into knickpoints and act as a primary control of riverbed incision and thus reduce the potential of new landslide the stability of landslide dams depends mainly on the development of the step pool system and stream power of the flood flow if a landslide dam consists of many boulders a step pool system may develop on the spillway channel of the dam which would maximize the resistance consume most of the flow energy and consequently protect the dam from incision the development degree of the step pool system is represented by a parameter s p which was measured with a specially designed instrument a preservation ratio of landslide dams is defined as the ratio of preserved height after flood scouring to the original height of the dam for streams with peak flood discharge lower than 30 m3 s the preservation ratio is linearly proportional to s p for rivers with a peak flood discharge higher than 30 m3 s 30 30 000 m3 s the minimum s p value for stable channel increases with log p in which p is the unit stream power for a landslide dam with a poorly developed step pool system s p is smaller than the minimum value and the outburst flood incises the spillway channel and causes failure of the dam for preserved landslide dams sediment deposits in the quake lakes a landslide dam may develop into a knickpoint if it is stabilized by long term action of the flow large knickpoints can totally change the fluvial processes and river morphology uplift of the qinghai tibetan plateau has caused extensive channel bed incision along almost all rivers for many rivers the incision has been partly controlled by knickpoints upstream reaches of a knickpoint have a new and unchanging base level this brings about a transition from degradation to aggradation and from vertical bed evolution to horizontal fluvial process multiple and unstable channels are prominent in the reaches upstream of the knickpoints if hundreds of landslide dams occurred simultaneously on a reach of a mountain river the potential energy of bank failure and the slope erosion would be greatly reduced and sediment yield from the watershed may be reduced to nearly zero the quake lakes may be preserved long term and become beautiful landscapes streams with long term unfilled quake lakes have good aquatic ecology

monitoring surface change on a namib linear dune in tackling the apparently intractable problem of linear dune initiation and maintenance there has been a move away from large scale deductive models to smaller scale field studies of individual dunes this paper reports a study of surface change on a large complex linear dune in the namib desert southern africa the dune surface responds to a markedly seasonal wind regime in summer westerly winds erode sand from the west flank of the dune and deposit it on the easterly lee side of the dune crest in winter this pattern is reversed easterly winds erode sand from the east slope and deposit it on the west slope the crest therefore moves back and forth some 15 m each year returning at the end of a year s cycle to its position at the beginning the position of the base of the dune appears to remain fixed even though sand is moving throughout the dune system the dune does extend northward along some resultant of the westerly and easterly winds despite relatively high levels of activity especially at the dune crest there is no evidence of the breakdown of the linear dune form the conclusion must therefore be that linear dunes can be maintained in bimodal wind regimes and are not necessarily related to unidirectional parallel regimes as others have suggested

bagnold s barchan a 57 yr record of dune movement in the eastern sahara and implications for dune origin and paleoclimate since neolithic times abstract discovery in 1980 of camp 18 of the 1930 bagnold expedition in northwestern sudan has resulted in an exceptionally long record of barchan movement from which an average rate of 7 5 m yr has been calculated measurements of the rate of dune advance since 1980 have not varied significantly indicating a state of quasiequilibrium exists the dune field is moving over an undulating sand sheet exhibiting various stages of holocene pedogenesis and containing neolithic sites the sand sheet overlies pleistocene alluvium with stronger stages of pedogenesis all of these deposits may be a significant source of dune sand wind blown grass fragments trapped by advancing slipfaces mark former slipface positions and indicate late holocene rainfall events which can be radiocarbon dated parabolic forms revealed by spot images at the windward ends of the dune fields are transitional to barchans suggesting sand accumulation in vegetation germinated during a holocene wet period in addition sand streaks from sand sheet undulations suggest that active eolian erosion of sand sheets contributes to the sand supply of dune fields pedogenesis during pluvial periods contributes to silt and clay fractions of bimodal sand sheet sediments from wind streaks on landsat images and an estimated average rate of dune advance positions of dune fields during past hyperarid periods can be estimated

a second look at western sinai seif dunes and their lateral migration abstract tsoar et al tsoar h blumberg d g stoler y 2004 elongation and migration of sand dunes geomorphology 57 293 302 reported that seif dunes in the western sinai desert did not migrate laterally between 1973 and 1999 if the planform sinuosities of the dunes are removed by filtering spatial averaging or linear regression however it is evident that the dunes did in fact migrate laterally roughly 13 m during this 26 year period the measured migration distance is 1 2 orders of magnitude greater than the rms co registration error tsoar et al determined for the first and last air photos that were used to map the dunes the western sinai dunes provide another example demonstrating that linear dunes can migrate laterally and they illustrate some of the difficulties in documenting systematic lateral motion lateral migration of a dune can be important geologically or geomorphologically even where migration is too slow to detect from repeated topographic surveys this article explains the wind conditions for the lateral migration of seif dunes in western sinai and the possible wind occurrences that would not lead to such a migration

euler deconvolution of gravity tensor gradient data tensor euler deconvolution has been developed to help interpret gravity tensor gradient data in terms of 3 d subsurface geological structure two forms of euler deconvolution have been used in this study conventional euler deconvolution using three gradients of the vertical component of the gravity vector and tensor euler deconvolution using all tensor gradients these methods have been tested on point prism and cylindrical mass models using line and gridded data forms the methods were then applied to measured gravity tensor gradient data for the eugene island area of the gulf of mexico using gridded and ungridded data forms the results from the model and measured data show significantly improved performance of the tensor euler deconvolution method which exploits all measured tensor gradients and hence provides additional constraints on the euler solutions

the palaeoenvironmental significance of dune size hierarchies the size of a dune is a function of many factors one of which is the length of the period of consistent wind regime under which it grew ephemeral dunes are defined as those that are adjusted to diurnal wind regimes meso dunes to annual wind regimes and mega dunes to wind regimes that persist for longer periods these longer periods could be major climatic cycles but there seem to be no dunes whose size reaches that allowed by the length of some of these periods there may therefore be a maximum size beyond which mega dunes cannot grow dictated by sand supply aerodynamic processes such as speed up or by the scale of the atmospheric boundary layer these concepts are tested on dunes in the wahiba sands in oman analysed from a landsat image it is hypothesised that a large set of megadunes here formed in the lgm that a smaller set of mega dunes may be of younger dryas age and that there is a meso dune series of holocene age

11 11 dune morphology and dynamics this chapter discusses the key types of sand dunes and how they can be classified and assesses the major controls on their development the processes of dune dynamics are reviewed leading to a discussion of the concept of equilibrium in solitary dune form recent advances in modeling are reviewed that show how interactions between dunes may result in equilibrium at the dune field scale rather than at the single dune scale

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

river patterns and their meaning abstract rivers are largely responsible for shaping the earth s continental landscapes river patterns the spatial arrangements of channels in the landscape are determined by slope and structure at site and sector scale channel morphology varies spatially and in time but river patterns and drainage texture or the frequency of stream lines per unit area together determine the intricacy or otherwise of topography most river patterns evolve through natural selection slope induces the formation of such patterns as parallel radial and distributary while structure produces straight angular trellis and annular arrangements once established patterns tend to persist nevertheless at many sites the usual patterns have been disturbed and patterns that are anomalous in terms of slope and structure have been produced by diversion tectonism volcanism glaciation mass movements and human activities by antecedence superimposition inheritance or underprinting by the persistence of deeply eroding rivers which encounter alien structures and by climatic change river patterns provide clues to underlying structure and to the chronology of events they have also proved significant in the search for minerals

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

depth estimation for magnetic gravity anomaly using model correction the tilt depth method has been widely used to determinate the source depth of a magnetic anomaly in the present study we deduce similar tilt depth methods for both magnetic and gravity data based on the contact and sphere models and obtain the same equation for a gravity anomaly as that for a magnetic anomaly the theoretical equations and the model tests show that the routine tilt depth method would result in unreliable depth estimation for deep sources this is due to that the contact model is no longer valid for causative sources under the condition in which the depths of causative sources are significantly larger than their horizontal lengths accordingly we suggest that the tilt depth derived from the contact model can be used to detect a shallow source whereas the tilt depth derived from the sphere model can be used to detect a deep source we propose a weighting method based on the estimated depths from both the contact model and the sphere model to estimate the depth for real data the model tests suggest that the determined depths from the contact model and the sphere model are shallower and deeper respectively than the real depth while the estimated depth from the proposed method is more close to the actual depth in the application to the weigang iron ore located in jiangsu province china the routine tilt depth method results in 76 relative error whereas the proposed method obtains the reliable depth estimation compared with the drill holes in addition the proposed method works well in the application for the shijiaquan iron ore located in shandong province china these results indicate that the proposed weighting equation is a general improvement

turbidite paleoseismology in the calabrian arc subduction complex ionian sea 1 the calabrian arc subduction system is part of the africa eurasia plate boundary is one of the most seismically active regions in the mediterranean sea and has been struck repeatedly by destructive historical earthquakes in this study we investigate the effects of historical earthquakes on abyssal marine sedimentation through the analysis of the turbidite record we collected gravity cores in tectonically controlled basins where the eastern mediterranean pelagic sequence is interbedded with resedimented units textural micropaleontological geochemical and mineralogical signatures reveal three turbidite events in the last millennium we dated the turbidite sequences from two different cores using different radiometric methods whereas the average time interval between successive turbidite beds was estimated from pelagic sediment thickness and sedimentation rates chronologies were refined through age modeling that provided age ranges 2 of each turbidite bed the results suggest that turbidite emplacement was triggered by three historical earthquakes recorded in the area i e the 1908 1693 and 1169 events their magnitude epicentral location and associated tsunamis support causative faults located in the ionian sea the source for all the turbidites as inferred from their mineralogy is the metamorphic basement outcropping in southern calabria and or northeastern sicily turbidite composition and cable breaks for the 1908 event have been used to infer likely traveling paths and seismogenic faults in the subduction system our findings suggest that ionian sea turbidites represent more than 80 of sedimentation and may be seabed archives of paleo earthquakes capable of reconstructing seismicity back in time during several earthquake cycles

new insights into magnetic derivatives for structural mapping magnetic and gravity derivatives can be likened to seismic attributes in that they can help define estimate the physical properties of the source structure causing the anomaly this contribution looks at the tilt derivative first reported in 1994 and more recently used to derive the local wavenumber 1997 we will show that the combination of the tilt derivative and its total horizontal derivative are highly suitable for mapping shallow basement structure and mineral exploration targets and that they have distinct advantages over many conventional derivatives we provide the simple theory behind the derivatives use a range of simple 2d models to illustrate their response and apply them to mapping a mineral target in namibia

magnitude and frequency of grain flows on a desert sand dune preliminary studies of the magnitude and frequency of lee side avalanches grain flows on a namib crescentic dune show that the frequency of grain flows for a given segment of the lee face is dependent on the wind speed and sand transport rate for the period preceding their initiation and the magnitude of the flows as described by their area is inversely proportional to the interval between flows and thus wind speed and sand transport rates these studies indicate the potential of using a simple digital video camera technique to document the magnitude frequency and geometry of grain flows on desert sand dunes

construction of component maps from aeromagnetic total field anomaly maps1 total field anomalies as defined from normal aeromagnetic surveys give good approximations of the anomalous components along the direction of the main geomagnetic field which is generally much larger than the anomalous field using the relations between vertical and horizontal components of the field the total field anomaly is related to any vertical or horizontal component and the corresponding horizontal and vertical derivatives an example from the siljan impact structure indicates that such directional filters may be applied to extract useful information from magnetic maps

interpretation of tensor gravity data using an adaptive tilt angle method abstract full tensor gravity gradiometry ftg data are routinely used in exploration programmes to evaluate and explore geological complexities hosting hydrocarbon and mineral resources ftg data are typically used to map a host structure and locate target responses of interest using a myriad of imaging techniques identified anomalies of interest are then examined using 2d and 3d forward and inverse modelling methods for depth estimation however such methods tend to be time consuming and reliant on an independent constraint for clarification this paper presents a semi automatic method to interpret ftg data using an adaptive tilt angle approach the present method uses only the three vertical tensor components of the ftg data tzx tzy and tzz with a scale value that is related to the nature of the source point anomaly or linear anomaly with this adaptation it is possible to estimate the location and depth of simple buried gravity sources such as point masses line masses and vertical and horizontal thin sheets provided that these sources exist in isolation and that the ftg data have been sufficiently filtered to minimize the influence of noise computation times are fast producing plausible results of single solution depth estimates that relate directly to anomalies for thick sheets the method can resolve the thickness of these layers assuming the depth to the top is known from drilling or other independent geophysical data we demonstrate the practical utility of the method using examples of ftg data acquired over the vinton salt dome louisiana usa and basalt flows in the faeroe shetland basin uk a major benefit of the method is the ability to quickly construct depth maps such results are used to produce best estimate initial depth to source maps that can act as initial models for any detailed quantitative modelling exercises using 2d 3d forward inverse modelling techniques

geomorphology of desert sand dunes a review of recent progress through the 1980s and 1990s studies of the geomorphology of desert sand dunes were dominated by field studies of wind flow and sand flow over individual dunes alongside these there were some attempts numerically to model dune development as well as some wind tunnel studies that investigated wind flow over dunes as developments with equipment allowed field measurements became more sophisticated however by the mid 1990s it was clear that even these more complex measurements were still unable to explain the mechanisms by which sand is entrained and transported most importantly the attempt to measure the stresses imposed by the wind on the sand surface proved impossible and the use of shear or friction velocity as a surrogate for shear stress also failed to deliver at the same time it has become apparent that turbulent structures in the flow may be as or more important in explaining sand flux in a development paralleled in fluvial geomorphology aeolian geomorphologists have attempted to measure and model turbulent structures over dunes progress has recently been made through the use of more complex numerical models based on computational fluid dynamics cfd some of the modelling work has also suggested that notions of dune equilibrium form may not be particularly helpful this range of recent developments has not meant that field studies are now redundant for linear dunes careful observations of individual dunes have provided important data about how the dunes develop but in this particular field some progress has been made through ground penetrating radar images of the internal structure of the dunes the paradigm for studies of desert dune geomorphology for several decades has been that good quality empirical data about wind flow and sand flux will enable us to understand how dunes are created and maintain their form at least some of the difficulty in the past arose from the plethora of undirected data generated by largely inductive field studies more recently attention has shifted although not completely to modelling approaches and very considerable progress has been made in developing models of dune development it is clear however that the models will continue to require accurate field observations in order for us to be able to develop a clear understanding of desert sand dune geomorphology

understanding linear dune chronologies insights from a simple accumulation model abstract dunefields are today often found in regions where environmental conditions are no longer conducive to widespread aeolian transport and deposition and are thus seen as potential archives of palaeoenvironmental information some dune types are more suitable for this purpose than others and linear dunes used here synonymously with longitudinal dunes have been most frequently employed they are commonly found in dryland and dryland marginal regions and they are apparently less migratory than some other dune forms thereby offering the potential for longer environmental histories most recent studies have employed optical osl dating surveys which directly date the emplacement of dune sands to attempt to produce a representative history of aeolian accumulation at a dunefield scale yet such studies have not always given due consideration to the geomorphology of linear dune accumulation although linear dunes do not rework their sand as readily as say barchans dunes it is clear that sand deposited during an aeolian event is likely to have been removed from elsewhere on the dunefield s surface for this reason all dune archives must be assumed to be discontinuous over long timescales the effect of sediment redistribution on dune preservation and thus palaeoenvironmental interpretation is difficult to observe and poorly understood we present a simplified probabilistic model to replicate deposition erosion of sand at a linear dune crest thus simulating the type of profile sampled in many field studies in order to produce a local accumulation history the modelled sand flux incorporates various feedbacks and the simulations are run with varying boundary conditions in which the simulated surface is assumed to be in equilibrium over the multi millennial timescales of the model s duration periodic instabilities in the landscape are generally well recorded by the modelled dune accumulation history particularly when the events involve the system as a whole briefly functioning out of an equilibrium state i e the probabilities of deposition and reworking are not equal however under forcing conditions where the probabilities are unchanged throughout the duration of the model run the results can show apparent structure within the data when sample sizes are low although at large sample sizes the preservation potential decays with burial age according to a power law the model confirms the importance of rigorous sampling strategies for such studies but also suggests that if such precautions are taken the reworking inherent to linear dune aeolian systems does not preclude their use as a quaternary palaeoenvironmental archive of environmental change

age and dynamics of linear dunes in the namib desert bristow c s duller g a t lancaster n 2007 age and dynamics of linear dunes in the namib desert geology 35 6 555 558 sponsorship american chemical society

impact of mass movements on geo and biodiversity in the polish outer flysch carpathians complex research was simultaneously done on the geological geomorphological and biocenotic features of landslide areas in the polish outer flysch carpathians the research allowed us to define the relations between the diversity of the landslide originating landforms and the biotopes occurring within them high geodiversity diversity of landforms soil and water of landslide areas allows for a mosaic network of extremely diversified natural habitats all of these natural habitats together are characterized by a specific biodiversity dependence between geo and biodiversity in landslide areas is connected with a specific co evolution which is related to the adaptation of the ecosystems to landforms comprehensive research of this relation to landslide areas would promote the necessity to protect the landslide areas unfortunately such research done in the carpathians is still sporadic the comprehensively documented landslide areas are especially valuable elements of the nature protection network within the carpathian euro region if made reasonably accessible they may be used for didactic purposes and in geotourism

width height and slope relationships and aerodynamic maintenance of barchans the allometric relationship between the height of barchan dunes and horn to horn widths is re examined the addition of new data from barchans in the namib desert and elsewhere confirms the relationship that the height of a barchan is approximately one tenth of the width of the dune height and width of the dune are closely linked to the three dimensional morphology of the dune in particular the relatively constant mean angles of around 11 at which the side slopes of the dune are maintained we suggest that the 3 d barchan form is directly controlled by aerodynamic processes constant feedback between three dimensional stoss face windward shape of the dune slipface height and horn to horn width and shear stress produces an equilibrium dune form

analyzing dune dynamics at the dune field scale based on multi temporal analysis of landsat tm images abstract studying dune dynamics at the dune field scale requires intensive fieldwork and a relatively huge dataset however this is not always possible with the high cost and the limited availability of data here we present a technique based on the analysis of multi temporal landsat tm images for studying the dynamics of different dune morphologies from five dune field sites around the world a pair of landsat tm images for each site has been used after performing several steps of image pre processing and enhancement i e image co registration radiometric calibration and histogram equalization rgb clustering is a commonly used algorithm for data compression and iso clustering in this study we implemented this technique as an unconventional change detection algorithm with 32 clustering partitions per band a bi temporal layerstack of the near infrared bands was the input for the rgb clustering process rgb clustering produced thematic maps that gave an immediate insight into the dune dynamics at the dune field scale given the availability of landsat images the technique gave the best results with dunes developed under uni directional wind pattern in addition it was also easier to detect migration of simple dunes than in compound or complex dunes these maps can be used as a bi temporal digital atlas of large dune systems and help in defining areas for detailed field measurements on dune dynamics and migration moreover it can be implemented in analyzing aeolian systems where field measurements are practically impossible i e large and extra terrestrial aeolian systems

palaeoenvironmental reconstructions from linear dunefields recent progress current challenges and future directions abstract this paper reviews recent progress in the use of linear dunes as geoproxies of late quaternary environmental change summarises the challenges facing their use and explores some potential solutions to these challenges large areas of the swathes of linear dunes which occupy the continental interior of southern africa australia and parts of central asia and southern america currently have limited or negligible aeolian activity they have been recognised as offering potential information about past environments for more than a century but only with the widespread application of luminescence dating during the 1990s did they realistically start to offer the prospect of being an extensive dateable proxy of late quaternary palaeoenvironments and possibly palaeoclimates dating aeolian dune sands with luminescence methods is generally although not always relatively straightforward over the past twenty years a large number 1000 of luminescence ages have been added to the global dataset yet there has also been significant criticism of some of the rationale underpinning much of the interpretation of the records derived at the landscape scale developments of arguably equal importance have come from improved geomorphological understanding based on the wider availability of remotely sensed data and the paradigm of dunefield evolution as a self organising complex system current challenges are identified in three key regions incomplete understanding of how the process geomorphology of linear dunes affect the accumulation and preservation of sediment a lack of clarity regarding the temporal and spatial scale of the response in a dynamic environmental setting and uncertainty surrounding the drivers of changing rates of net accumulation solutions to these challenges lie within diverse research methodologies certainly further field study is required with improvement required in understanding system responses to changing environmental stimuli at scales from sedimentological to landscape in parallel the full implications of complex systems approaches to aeolian geomorphology for linear dunes lag behind the adoption of the concept to some other dune forms e g barchans the relationship between observed dune complexity and age from field data complicates previous suggestions that dune patterning may be purely a function of development time parallel to this lies the need to improve interpretation of the results of dune geochronological studies a suggestion is offered which aims to test the statistical significance of dune accumulation time series by comparison with a modelled system with unchanging external forcing despite the initial promise of linear dune records as a revolutionary source of palaeoenvironmental information in drylands the outcomes to date have been coarse although still valuable in resolution perhaps the most valuable realization has been that geomorphological understanding of these widespread landforms is incomplete

morphometric evidences of recent tectonic deformation along the southeastern margin of the hyblean plateau se sicily italy abstract the present work focuses on the tectonic characterization of the southeastern portion of the hyblean plateau se sicily italy along the southeastern margin of this raised crustal block a clear recent antiformal deformation coupled with diffuse landscape rejuvenation affects the summit surface many studies using merely qualitative geomorphological approach refer the recent morphotectonic evolution of this region to motion along an active border fault located at the base of the well developed arc shaped avola mountain front this paper provides new insights resulting from the morphometric analysis across the avola region in order to detail on the relationships between the landscape geomorphic unsteadiness and the long term tectonic deformation we perform both drainage system and relief investigations consisting of the exploration of different geomorphic indices e g hypsometric integral topographic relief and dissection sl index ksn long profile analysis marine terraces age model definition field based geomorphological and structural surveys the results and the spatial distribution of morphometric indexes evidence the occurrence of two incipient nne trending en echelon fault segments here named cassibile noto fault responsible for the relief building along the southeastern border of the hyblean plateau the northern fault segment directly controls the northern portion of the avola mountain front whereas the southern segment diverges from the main scarp cutting through the low standing areas of the coastal plain in addition the centrifugal arrangement of fluvial captures and the half elliptical envelope of the downstream projections of coeval paleo long profiles as well as the distribution of pleistocene marine terraces well evidence the long term wnw ese trending low amplitude bow shaped deformation affecting the footwall of the cassibile noto normal fault we relate this convex upward trend to the late pleistocene

3d inversion of airborne gravity gradiometry data using cokriging abstractwe developed a new method for interpretation of airborne gravity gradiometry data based on cokriging inversion the cokriging method that we evaluated minimized the theoretical estimation error variance by using auto and crosscorrelations of several variables it does not require iterations and can easily include complex a priori information moreover the smoothing effects in the inverted density structure model can be reduced to a certain extent due to the anisotropy constrain in the covariance model we compared the recovered models obtained by inverting the different combinations of gravity gradient components to understand how different component combinations contributed to the resolution of the recovered model the results indicated that including multiple components for inversion increased the resolution of the recovered density model and improved the structure delineation moreover in the case in which the parameters of the variogram model are not well chosen cokriging with multicompon

the gradient tensor of potential field anomalies some implications on data collection and data processing of maps the full gradient tensor is presently not measured routinely onboard airplanes or on land this paper describes some improvements that can be made in strategies of data collection and in processing of potential field maps if such tensor measurements were available we suggest that in addition to producing for example standard total field anomaly maps the invariants of the tensor be mapped strikes of magnetic or gravimetric structures may be determined from minimizing the power in the first row and column of the tensor invariants can be looked upon as nonlinear filters enhancing sources with big volumes their lateral resolution is superior to that of the field proper and for a given resolution the flight altitude and separation between flight lines can be increased compared with the standard mode of operation in airborne surveys the distance between flight lines is normally much larger than the height above the ground this may introduce severe aliasing effects in the direction perpendicular to the

inconsistent patterns of historical seismicity and earthquake triggered landsliding in southeastern sicily an alarm bell in southeastern sicily the distribution pattern of earthquake triggered landslides is inconsistent with historically known seismic activity in particular historical seismicity has been stronger in the eastern sector while earthquake triggered landsliding is much more developed in the western sector and this contrasts with expectations this paper describes the patterns of seismicity and landsliding and tackles the problem of whether greater landsliding in the western sector may be due a to seismicity of the eastern sector or b to a high magnitude low recurrence seismicity generated in the western sector itself it is statistically shown that lithostructural characteristics of rock masses and geometry of hillslopes cannot justify either singly or jointly greater landsliding in the western sector if triggering earthquakes are generated in the eastern sector as a consequence it is possible that landsliding of the western sector is due to earthquakes generated locally but having higher magnitude and longer recurrence intervals than historically observed

geomorphic events and landform response in south eastern taranaki new zealand abstract south eastern taranaki is a tectonically rising area of hill country and marine terraces cut into plio pleistocene marine sediments in the north island of new zealand it is argued that the geomorphic development of the region is more satisfactorily explained with resort to concepts of dynamic metastable equilibrium and unsteady behaviour than by concepts of steady equilibrium behaviour the region is constantly adjusting in part or in whole to a spectrum of geomorphic events including sea level change tectonic uplift aeolian deposition large landslide triggering earthquakes deforestation and landslide triggering rainstorms the record of these events in terms of frequency and magnitude is established and the consequential landform response is discussed twelve high sea level events within the last 700 ka are recorded in the landscape each with associated phases of aeolian deposition large earthquakes with terrain forming capability occur on average once every 1000 to 10 000 years as a result of slope destabilization by recent deforestation erosion rates appear to have increased by three times their previous rate the agents involved in this process are rainstorms with a return period of about 10 years which during a single event can strip the regolith from 5 to 15 percent of hillslopes over areas of up to 100 km2

origin and morphology of barchan and linear clay dunes in the shuhongtu basin alashan plateau china abstract clay dunes are characterized by a relatively high content of silt and clay and are typically developed on the lee side margin of closed basins in arid and semi arid areas although they are widely distributed aeolian landforms on earth little is known about their development and distribution in asia our field investigations have identified for the first time the occurrence of clay dunes in the alashan plateau north china the clay dunes occur in three isolated lowland areas of the suhongtu sht basin and their morphologies barchans hooked barchans asymmetrical barchans and linear or seif dunes differ substantially from those of the well studied clay dunes in australia africa and north america these differences could be mainly attributed to the asymmetrical bimodal wind regime prolonged drought and sediment physical properties which indicate that dunes of any type can be formed in sand silt or clay based on the known evolution of the sht paleo lake basin and regional climate change we infer that the landscape of modern clay dunes in the desert of the alashan plateau does not predate mis 5 and probably formed during the late holocene analyses of grain size distributions and the contents of trace and rare earth elements combined with geomorphological characteristics indicate that the source sediments of the clay dunes are mainly local cretaceous tertiary and quaternary red fluvial lacustrine mudstone and sediments while the ultimate source is the weathered and denuded products of granitoids of the east altay mountains comparison of the morphology and alignment of the clay dunes with the prevailing wind pattern tends to support tsoar s 1984 model of the transition in dune shape from barchans to seif or linear dunes during 2003 2013 the seif or linear dunes of the sht basin migrated laterally and elongated northeastward at rates of about 2 4 m yr and 16 20 m yr respectively