karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

uplift history of the central and northern andes a review the elevation of the andean cordillera is a crucial boundary condition for both climatic and tectonic studies the andes affect climate because they form the only barrier to atmospheric circulation in the southern hemisphere and they intrigue geologists because they have the highest plateau on earth formed at a noncollisional plate margin the altiplano puna yet until recently few quantitative studies of their uplift history existed this study presents both 1 a review of the quantitative paleoelevation estimates that have been made for the central and colombian andes and 2 an examination of the source and magnitude of error for each estimate in the central andes paleobotanical evidence suggests that the altiplano puna had attained no more than a third of its modern elevation of 3700 m by 20 ma and no more than half its modern elevation by 10 7 ma these data imply surface uplift on the order of 2300 3400 m since the late miocene at uplift rates of 0 2 0 3 mm yr paleobotanical and geomorphological data suggest a similar uplift history for the eastern cordillera namely no more than half the modern elevation present by 10 ma no evidence exists for an exponential increase in uplift rate as has been interpreted from fissiontrack data these uplift rates mostly reflect mean surface uplift rather than rock uplift that is uplift of material points because little dissection of the western eastern cordillera has occurred south of lat 19 s and of the altiplano puna thus the central andean plateau appears to be young in the colombian andes paleobotanical data imply rapid uplift of the eastern cordillera between 2 and 5 ma at rates on the order of 0 6 3 mm yr however some of this uplift is likely rock uplift due to erosion driven isostatic rebound rather than mean surface uplift

petrogenetic evolution of arc magmatism associated with late oligocene to late miocene porphyry related ore deposits in ecuador we present a data set on the geochemical and isotopic composition of mineralized porphyry intrusions se riate intrusions and arc volcanic formations spatially associated with late oligocene to late miocene porphyry related ore deposits in ecuador our aim is to constrain the petrogenetic evolution of these arc magmas to evaluate geodynamic and tectonic impact factors on arc magmatism and to explore the metallogenic signifi cance of these parameters we distinguish four petrogenetic groups associated with the investigated magmatic centers indicating dif ferent paths of low and high pressure crustal magma evolution tertiary ecuadorian arc magmas which dif ferentiated at higher crustal pressures are commonly characterized by adakite like compositions related to fractionation and or restite equilibration effects of amphibole garnet titanite particularly in hydrous silicic melts without concomitant or subsequent major plagioclase fractionation trace element distribution patterns of arc magmas through time are broadly systematic and indicate that crustal magma differentiation progres sively extends to higher pressures from the late oligocene to the late miocene possibly related to crustal thick ening locally adakite like features possibly related to high melt h2o contents or accessory phase fractiona tion are already observed in the early miocene in a regional setting otherwise dominated by low pressure magma evolution compositional differences between mineralized porphyry intrusions and spatially associated seriate precur sor intrusions in ecuador mostly reflect regional scale changes in magma composition through time and are not observed if the relative emplacement age difference is small where porphyry intrusions are associated with shallow crustal batholith systems in northern central ecuador their emplacement is commonly late with re spect to batholith magmatism intrusive compositions indicate that porphyry parental melts mostly evolved at higher crustal pressures where metallogenically favorable melt preconditioning might possibly occur

counterclockwise rotation of late eocene oligocene fore arc deposits in southern peru and its significance for oroclinal bending in the central andes the results of a paleomagnetic study along the fore arc of southern peru 15 18 s and northern chile 18 19 s are reported from middle to late miocene ignimbrites 7 sites late oligocene to early miocene ignimbrites 72 sites paleogene sediments 20 sites and mesozoic and paleocene volcanics and intrusions 31 sites comparison of locality mean directions with expected paleomagnetic directions indicates vertical axis rotations ranging from 5 2 11 3 clockwise to 55 6 7 0 counterclockwise spatially the magnitude of counterclockwise rotations increases northward from 0 within the chilean fore arc south of 18 30 s to 45 north of 16 30 s in southern peru paleomagnetic rotations recorded in paleogene red beds decrease from late eocene to late oligocene whereas miocene ignimbrites display no evidence of rotation these new results confirm that the rotations recorded in the fore arc of southern peru were acquired at least before 15 ma and probably before 25 ma and thus prior to the late neogene shortening of the sub andes the onset of major andean shortening in the eastern cordillera during the latest eocene earliest oligocene is interpreted to have triggered the bending of the peruvian fore arc the region of the peruvian fore arc with the largest rotations appears to be the fore arc counterpart of the abancay deflection a remarkable ne sw offset in the axis of the eastern cordillera induced by a major regional preorogenic structure we underline that the abancay deflection should be seen as the northwestern boundary and therefore as a key element of the bolivian orocline

high resolution mapping of rock fall instability through the integration of photogrammetric geomorphological and engineering geological surveys abstract a semi quantitative methodology for rock fall susceptibility assessment is presented the test area is located along the amalfi coast sorrento peninsula southern italy which is characterized by high relief energy and very steep slopes made up of dolomite limestone of mesozoic age generally the cliffs are strongly jointed and affected by karst processes for this reason rock falls rock slides and more seldom topples are very frequent in the area the study took a multidisciplinary approach mixing classical field geology observations with typically geo mechanical ones and required the support of highly professional staff such as applied geologists experts in photogrammetric survey techniques and engineers for stabilization works planning the acquisition of the data involves a detailed large scale study scale 1 500 this methodology is mainly suitable for the study of single cliffs or slope with limited dimensions cartographic representation is a main problem in the study of a vertical cliff a frontal topographic survey terrestrial photogrammetry was first carried out after this different geo thematic maps showing the main geological geomorphological and geostructural information were elaborated and then compared allowing the elaboration of the triggering susceptibility map the semi quantitative proposed method has a good accuracy in the realization of the potential detachment area of rock falls in order to predispose stabilization works and to rationalize the disposal resources for the hazard mitigation in the unstable areas near human utilization urban centres roads etc

thermochronology geochronology and upper crustal structure of the cordillera real implications for cenozoic exhumation of the central andean plateau 1 structural mapping 40ar 39ar and fission track thermochronology u pb geochronology and basin analysis reveal rapid cooling during middle eocene late oligocene and late miocene pliocene exhumation in the central andean plateau of bolivia in the 4 6 km high cordillera real numerous granites and sw directed fold thrust structures define the central andean backthrust belt along the altiplano eastern cordillera boundary u pb zircon analyses indicate permo triassic granitic magmatism with less extensive magmatism of late oligocene age mapping reveals low magnitudes of slip 5 km depth the 26 ma quimsa cruz granite postdated most thrust structures suggesting that upper crustal shortening in the cordillera real had largely ceased by late oligocene time results of 40ar 39ar and fission track modeling help constrain the moderate to low temperature 350 c cooling history revealing two phases of rapid cooling from 45 40 ma to 26 ma and from 11 ma onward initial cooling coincided with middle eocene late oligocene deformation in the backthrust belt and associated deposition of coarse clastic sediments in the altiplano basin eocene oligocene exhumation of 7 5 km of upper crust is estimated on the basis of thermochronologic data rapid late miocene and younger cooling involved an estimated 3 5 km of exhumation and occurred in the apparent absence of upper crustal shortening these findings suggest that crustal shortening and resultant exhumation of middle eocene late oligocene age played a major role in construction of the central andes however for late miocene exhumation the importance of alternative nonshortening mechanisms is difficult to ascertain due to a poor understanding of subsurface structures we speculate that greater precipitation on the eastern edge of the central andean plateau north of 17 5 s was a key factor in driving rapid youthful exhumation of the cordillera real

volcaniclastic debris avalanche on motomachi area of izu oshima japan triggered by severe storm phenomenon and mechanisms abstract heavy rainfall and strong wind associated with typhoon wipha hit izu oshima island japan and triggered catastrophic landslides on the western slope of oshima volcano on 16 october 2013 these landslides were shallow but large in scale and the displaced landslide materials were characterized by rapid and long runout movement a massive landslide resulted in 36 people dead and 3 missing with 46 buildings being completely destroyed in the downstream area of motomachi district to understand the initiation and movement of these shallow landslides we surveyed the landslide area and found that in addition to heavy rainfall strong wind may also have played a key role in increasing the instability of the slopes we took samples from the source areas and examined their static and dynamic shear behaviors under naturally drained or undrained conditions test results showed that high pore water pressure can be built up and maintained within the displaced landslide material and increase landslide mobility even though the thickness of displaced landslide materials is 0 7 1 2 m this may then give a rational explanation on the fluidization process of the displaced landslide materials we also examined the windthrow features of trees subjected to different wind speed through monitoring the ground motion by seismometer and portable anemometer and then performed cyclic shear tests on the materials laying above the sliding surface the test results suggest that the windthrow may have promoted the buildup of excess pore water pressure within the saturated soil layer and thus favoured the occurrence of slope failure therefore it is suggested that in the prediction of shallow landslides on forested slopes subjected to heavy storm both the effects of rainfall and strong wind should be taken into account

influence of andean uplift on climate and paleoaltimetry estimates article i nfo article history recent elevation reconstructions of the andean plateau suggest a rapid 2 5 1 0 km rise of the central andes between 10 and 6 ma this rapid rise has been attributed to a catastrophic removal of a dense lithospheric mantle root beneath the andes however these findings are based on the assumption that climate did not change during deposition of paleoaltimetry proxies here we evaluate south american climate change due to andean uplift and its influence on interpretations of plateau elevation from climate sensitive paleoaltimetry data a series of experiments are presented using the regcm3 regional general circulation model rcm to characterize changes in andean precipitation amount surface temperature and wind direction vapor source as a function of changing plateau elevation results indicate that south american and andean climate changed significantly in response to plateau growth more specifically rising of the plateau results in up to a 900 mm increase in rainy season december january february precipitation over the plateau plateau uplift also results in a decrease in non adiabatic surface temperature of up to 6 5 c in addition to adiabatic cooling directly related to elevation change through the lapse rate finally the prevailing wind direction and the vapor source for precipitation switches from the south pacific ocean to the equatorial atlantic as plateau elevation increases above of its present day elevation taken together these changes in paleoclimate would have substantially depleted the oxygen isotopic concentration of paleoprecipitation through the cenozoic unless this climatic effect is taken into consideration paleoaltimetry reconstructions based on stable isotope methods may overestimate the rapid rise of the andes by up to several kilometers we conclude that some or all of the apparent rapid rise of the andean plateau from paleoaltimetry data could be an artifact of large changes in paleoclimate

quantitative radiometric and biostratigraphic calibration of the pennsylvanian early permian cisuralian time scale and pan euramerican chronostratigraphic correlation a quantitative biostratigraphic and radiometric calibration is presented for the pennsylvanian through early permian global time scale based upon high precision isotope dilution thermal ionization mass spectrometer id tims u pb zircon ages for interstratified ash beds in the parastratotype sections of the southern urals of russia twenty four ash bed ages in three outer ramp and basinal sections of the pre uralian foredeep bracket the biotic definitions of global stages and regional substages from the base of the upper pennsylvanian kasimovian stage to the base of the lower permian artinskian stage four additional ash bed ages in two sections of the eastern slope of the urals constrain the global bashkirian and serpukhovian stages quantitative stratigraphic methods conop9 are applied to a compilation of over 2000 bioevents in 22 stratigraphic sections supplemented by our dated volcanic horizons to refine the pennsylvanian early permian global time scale significant shifts in the duration of several stages are demonstrated ranging from one to six million years compared with prior estimates the unprecedented density of radiometric calibration points for the pennsylvanian permian transition provides a high resolution 0 1 ma global chronostratigraphic standard for testing and improving biostratigraphic correlations across euramerica we integrate radiometric ages biostratigraphic correlation and cyclostratigraphic tuning of major cyclothems to the long period 404 ka eccentricity cycle to elucidate the tempo magnitude and forcing of eustatic changes and cyclothemic deposition associated with the waxing and waning of gondwanan ice sheets and establish a pan euramerican chronostratigraphic framework for most of pennsylvanian and early permian time

debris slides rapid earth flows in the carbonate massifs of the campania region southern italy morphological and morphometric data for evaluating triggering susceptibility abstract this paper examines the morphological and morphometric properties of debris slides rapid earth flows which have occurred in pyroclastic deposits of the campania region over the last few centuries the slopes bordering the main carbonate massif of western campania are covered by several metres of pyroclastic deposits from the somma vesuvio volcano that due to the steepness of the slopes are easily eroded by surface waters and periodic debris slides rapid earth flows these flows are sudden and unpredictable and have caused both damage to the environment and loss of life over the last few decades after consulting scientific papers and historical documents the areas most recently affected by debris slides rapid earth flows were analysed through aerial photographs and a geological survey an inventory of 172 landslides was produced and landslides were mapped at a scale of 1 2000 for further geomorphological and morphometric analysis morphological analysis was primarily concerned with predisposing factors it confirmed that 86 of the slope failurecrowns developed in response to man made cuts and tracks 44 or due to the presence of cliffs 42 two different kinds of slopes are affected by debris slides rapid earth flows slopes lacking drainage basins and slopes cut by one or several drainage basins typical triangular shaped earth flows with a landslide mass located at the foot of the slope unchannelled debris slides rapid earth flows were found along the former slopes in contrast channelled debris slides rapid earth flows formed along the latter slopes these originated in the drainage divide area developed along the main water segment and invaded the alluvial plain far from the foot of the slope an intermediate group of flows started as triangular shaped and then became channelled morphometric analysis also investigated the parameters most commonly found in the literature slope angle of the crown and sliding zone crown altitude areal extent of the landslide together with other parameters apical angle of the crown zone and landslide body slope relief energy and potential zone of triggering this analysis identified critical values for the steepness of crown zones and for the steepness of the sliding zone critical values of the apical angle of the crown zone for mixed and unchannelled landslides were also established correlations among some of the investigated parameters were investigated in particular the relationships between slope relief energy and areal extent of landslides or the height of the landslide crown zone all the factors and parameters analysed in this paper can be used to identify areas which need to be stabilized or monitored and could be important for planning defensive measures of debris slides rapid earth flows

rapid uplift of the altiplano revealed through 13c 18o bonds in paleosol carbonates the elevation of earth s surface is among the most difficult environmental variables to reconstruct from the geological record here we describe an approach to paleoaltimetry based on independent and simultaneous determinations of soil temperatures and the oxygen isotope compositions of soil waters constrained by measurements of abundances of 13 c 18 o bonds in soil carbonates we use this approach to show that the altiplano plateau in the bolivian andes rose at an average rate of 1 03 0 12 millimeters per year between 10 3 and 6 7 million years ago this rate is consistent with the removal of dense lower crust and or lithospheric mantle as the cause of elevation gain

thickening the altiplano crust by gravity driven crustal channel flow 1 in the central andes crustal thickness is not well correlated to upper crustal shortening only little shortening is documented in the upper crust of the 60 65 km thick altiplano plateau whose thickening and uplift were delayed with respect to earlier and greater thickening in the adjacent western and eastern cordilleras because crustal thickness variations induce horizontal stress gradients and cause crustal flow a thickness dependent channel flow is modeled here and applied to the central andes in situ thickening is assumed for both cordilleras while the altiplano crustal thickening is generated by lateral flow from these overthickened adjacent domains a 8 1018 pa s viscosity channel is predicted for crustal thicknesses exceeding 45 50 km to match the estimated topographic evolution of the central andes thickening in the cordilleras was sufficient to generate a flow of 6 109 m3 per unit length toward the initially 30 35 km thick altiplano

triggering and predisposing factors for flow like landslides in pyroclastic soils the case study of the lattari mts southern italy abstract shallow flowslides debris flows and debris avalanches are rainfall induced landslides consisting in the shear failure of few metres of soils or in some cases even less than a metre which greatly increase downslope in volume and flow velocity the southern italian region of campania has been historically affected by such events involving pyroclastic soils mainly resting on steep carbonate slopes this paper deals with the analysis of factors influencing the occurrence of flow like landslides adopting the lattari mts in campania as a case study the results of two investigation campaigns carried out in the area allowed effective large scale geological and geotechnical characterization to be set up stratigraphic profiles mean physical properties and typical friction angles at the critical state for each soil layer were investigated the effect of suction on peak and critical shear strength whose drop is responsible for soil failure was analysed using detailed information on both the stratigraphic and geotechnical features of the soils involved in past flow like landslides typical triggering models were selected representing locally recurrent geomorphologic conditions at the basin scale the identified models were adopted for slope stability analyses carried out on four cross sections of flowslides occurring prior to the event to back analyse the triggering conditions from the evidence on the triggering mechanisms and the results of analyses the infinite slope approach is not always suitable to model slope stability conditions properly because the onset of landslides is also affected by local topographic and stratigraphic factors

stable isotope evidence for multiple pulses of rapid surface uplift in the central andes bolivia paleoelevation histories from mountain belts like the central andes of bolivia provide important constraints on the timing and geodynamic mechanisms associated with surface uplift we present new oxygen and carbon isotope data 18 o 13 c and 47 from oligocene miocene strata exposed in the eastern cordillera of the bolivian central andes in order to reconstruct both the deformation and paleoelevation history of the region prior to late miocene time paleosol carbonate in strata 24 ma have 18 o c values between 5 7 and 9 7 and 47 values indicating paleotemperatures of 32 42 c paleosol carbonate in strata ca 17 ma have 18 o c values between 11 6 and 13 8 and 47 values indicating paleotemperatures of 15 23 c these data interpreted within the context of recent paleoclimate topography models suggest oligocene early miocene 29 24 ma paleoelevations were between 0 and 1 5 km a s l while middle miocene ca 20 15 ma paleoelevations were 2 5 km a s l oligocene and miocene strata are relatively undeformed and overlap folded and faulted paleozoic rocks in this portion of the bolivian eastern cordillera indicating much of the change in elevation occurred after upper crustal deformation collectively data from the area record an initial period of upper crustal deformation and exhumation a subsequent period of sediment deposition and overlap and then an episode of surface uplift accompanied by negligible upper crustal deformation the disconnect between the timing of upper crustal deformation and the timing of surface uplift requires geodynamic processes other than upper crustal thickening to explain the oligocene miocene basin and elevation history in the eastern cordillera we propose accommodation for oligocene miocene strata was created in response to the formation and removal of negatively buoyant material in the lowermost crust and mantle lithosphere and the subsequent increase in surface elevation between ca 24 and 15 ma resulted from its removal other locations in the central andes record similar geological histories over different time periods suggesting spatial and temporal variation in the removal of lithospheric mantle documenting basin extent age and elevation history provides important constraints on the size and timescale of the geodynamic processes that control surface uplift

the january 10 1997 pozzano landslide sorrento peninsula italy abstract from 1997 to 1999 a huge number of slides often turning into extremely rapid debris earth flows repeatedly affected the late quaternary volcaniclastic deposits mantling the carbonate slopes of campania region italy the sorrento peninsula was the epicentral district of the 1997 regional slope instability crisis some hundred shallow mass movements took place during january 1997 in this area these were the last episode of a long series of slope failure events dating back to mid 18th century results from geological and geomorphologic surveys are presented landslide mechanism and triggering factors are analysed for the most important mass movement which occurred during the january 9 11 1997 regional event on january 10 1997 at about 8 15 pm a rainfall induced debris slide debris flow occurred at pozzano province of naples mainly affecting the 79 ad pyroclastic products following a j path the landslide destroyed a private house and invaded the state road no 145 this event resulted in four deaths 22 persons injured and road closure for about 2 months there was less than 200 mm of rainfall in the 72 h period prior to the landslide although intense precipitation had occurred during a preceding 4 month period however the slope failure event was not preceded by an extreme short term antecedent rainfall as already noticed in previous landslides of this type in campania finally following a preliminary geotechnical characterization of volcaniclastic soils a slope stability back analysis was carried out which adopted the classical infinite slope scheme this analysis gave further evidence of the role played by pore pressure in reducing the overall shear strength of pyroclastic soils

geochronologic and stratigraphic constraints on canyon incision and miocene uplift of the central andes in peru the deepest valleys of the andes have been cut in southern peru by the rios cotahuasi ocona and colca majes these canyons are late miocene landforms based on a new ignimbrite stratigraphy supported by 42 new 40ar 39ar age determinations obtained on plateau forming and valley filling ignimbrites between 19 and 13 ma a gently sloping surface bevelling the clastic wedge southeast of the developing mountain front was mantled by widespread ignimbrites after 13 ma this paleosurface was tilted up from 2 2 km a s l at the mountain front to 4 3 km a s l at the base of the pliocene and pleistocene volcanoes that crown the southwestern edge of the altiplano the canyons incised this topography after 9 ma while the dated base of younger ignimbrite valley fills suggests that these canyons had been cut down to near their present depths as early as 3 8 ma by 1 4 ma however the canyons had been almost completely refilled by 1 3 km thick unwelded pyroclastic deposits which were subsequently eroded valley incision since 9 ma at an average rate of 0 2 mm yr 1 is the response to topographic uplift after 13 ma combined with increasing runoff due to a wetter climate recorded after 7 ma although long term aridity generated an imbalance between high long term uplift rates and low plateau denudation rates the combination of aridity and volcanism still promoted canyon incision because episodic volcanic fills maintained a cycle of catastrophic debris avalanches and subsequent dam breakouts

nonuniform surface uplift of the andean plateau revealed by deuterium isotopes in miocene volcanic glass from southern peru abstract proposals for rapid late miocene surface uplift driven by large scale lithospheric removal beneath the central andean plateau have been based largely on temperature sensitive paleoaltimeters both the magnitude and mechanism of this proposed pulse of uplift have been challenged first climatic general circulation models support protracted uplift with predicted temperature and isotopic shifts enhanced by attainment of threshold elevations second tectonic models in which surface elevations are compensated by regional contraction and crustal thickening question the need for lithospheric removal and predict broadly coeval uplift of the entire plateau we present hydrogen isotope data using a novel temperature insensitive volcanic glass proxy from continuous well dated lower to middle miocene basin fill in the western cordillera of the northern plateau that show a rapid decrease in d values 62 8 at 19 16 ma with extremely negative values continuing into the pliocene we propose that the basin reached its current elevation by 16 ma 6 myr earlier than proposed for the central plateau the rapid decrease in d values is consistent with punctuated surface uplift of 2 2 3 7 km between 19 and 16 ma whereas the 3 7 km upper estimate assumes a static climate similar to modern the 2 2 km lower estimate conservatively incorporates modeled changes in the isotopic composition of precipitation associated with elevation change comparison of these results to existing paleoelevation estimates from the andean plateau facilitates a tentative reconstruction of earliest middle miocene paleotopography showing a central depression with flanking hinterland and thrust belt highlands this apparent pattern of nonuniform plateau uplift contradicts shortening proportional topographic growth over tens of myr we propose that temporally and spatially irregular surface uplift may be linked to pronounced local variability in crustal shortening and or piecemeal removal of dense mantle lithosphere insofar as these irregularities reflect the scale of heterogeneity for surface uplift processes available paleoelevation estimates point to a principal uplift mechanism that varies over relatively short

triggering mechanism and reactivation probability of loess mudstone landslides induced by rainfall infiltration a case study in qinghai province northwestern china rainfall especially rainstorm is a major factor in inducing loess mudstone landslides and plays an essential role in landslide reactivation the aim of the paper is to study the triggering mechanism and reactivation probability of a loess mudstone landslide induced by rainfall infiltration in qinghai province northwestern china according to the numerical model of elastic plastic mechanics the triggering mechanism of loess mudstone landslides was revealed then the reactivation probability of the potential landslide was evaluated by the combination of the limit equilibrium and monte carlo methods for one thing the relationship between water content and shear strength of media was analyzed based on the mechanical test of materials for another the effects of rainfall conditions were analyzed on the distribution of water content in the aerated zone with the two dimensional coupling model of unsaturated saturated seepage the results show that the shear strength of media is very sensitive to water content because of water rock interaction including hydration and dissolution besides the water content significantly increases at the interface between the loess and mudstone after the rainstorm occurring owing to the permeability heterogeneous of media and topographic feature which leads to the strength deterioration although the whole landslide is stable in the rainstorm conditions its middle part can be reactivated along the original sliding zone with high probability by a geomechanical model of sliding tension therefore the landslide reactivation is controlled by the water sensitivity of media the permeability heterogeneous of media the topographic feature and the original sliding zone especially the original sliding zone this research provides a valuable reference for the occurrence and reactivation of similar landslides

tectonic evolution of the central andean plateau and implications for the growth of plateaus current end member models for the geodynamic evolution of orogenic plateaus predict a slow and steady rise during crustal shortening and ablative subduction i e continuous removal of the lower lithosphere or b rapid surface uplift following shortening which is associated with punctuated removal of dense lower lithosphere and or lower crustal flow this review integrates results from recent studies of the modern lithospheric structure geologic evolution and surface uplift history of the central andean plateau to evaluate the geodynamic processes involved in forming it comparison of the timing magnitude and distribution of shortening and surface uplift in combination with other geologic evidence highlights the pulsed nature of plateau growth we discuss specific regions and time periods that show evidence for end member geodynamic processes including middle late miocene surface uplift of the southern eastern cordillera and altiplano associated with shortening and ablative subduction latest

late pennsylvanian early permian vegetational transition in oklahoma palynological record abstract the wabunsee carboniferous virgilian through sumner permian leonardian groups of oklahoma preserve a record of terrestrial and nearshore marine environments during glacio eustatic fluctuations caused by southern hemisphere glaciation this section with the pennsylvanian permian boundary firmly established in the red eagle formation on the basis of conodonts permitted study of vegetational change across the boundary interval the palynology of 43 productive samples from five cores in kay and osage counties in oklahoma was investigated palynomorphs were assigned to eight morphologic groups that also reflect climate preferences four distinct palynofloras are recognized the three transitions between them in the lower council grove middle chase and lower sumner groups are abrupt and in succession consistent with an interpretation of increasing seasonality aridity from latest pennsylvanian into the early permian none of these floristic transitions align with the conodont based boundary or with any lithostratigraphic group boundary these palynological data from oklahoma are in accord with previous data from kansas that also demonstrated no palynological shift at the boundary and increased seasonality aridity through this period comparison of the palynofloras from oklahoma kansas and the boundary interval of the pennsylvanian permian boundary type section in aidaralash creek in kazakhstan reveals differences in composition that suggest local to regional including climatically induced heterogeneities that may present an obstacle to confident palynologically based global correlations in fully terrestrial sections

precaspian isthmus emergence triggered the early sakmarian glaciation evidence from the lower permian of the urals russia abstract the sub meridional seaway that connected paleo arctic and paleo tethys basins was one of the most important geographical attributes of the late paleozoic pangean landscape paleogeography and paleoclimate existing models about the timing of the disconnection of the paleo arctic and the paleo tethyan oceans is controversial and poorly documented warm water benthic foraminifera wwbf were utilized to establish the precise timing of the closure of the urals precaspian paleo tethys seaway upts during cisuralian time the wwbf of paleo tethys and those of the ural precaspian basins during the gzhelian asselian display a considerably high level of similarity beginning from the sakmarian the faunas of these two regions became dissimilar suggesting a break in the connection between the paleo tethys and ural precaspian basins sedimentological evidence olistostromes and seismites of the final collision of the eastern ural kazakhstania scythian turan plates with the southeastern part of the russian platform during late paleozoic also supports the emergence of the precaspian isthmus at the asselian sakmarian transition oceanic currents in the precaspian and the southern ural basins before the sakmarian were directed northward and later changed to the south the biotic and sedimentologic features clearly suggest the upts closure and the origination of precaspian isthmus during the asselian sakmarian transition the abrupt changes in the oceanic circulation triggered changes in atmospheric co2 atmospheric circulation and possibly albedo feedback the emergence of the precaspian isthmus induced an increase in the poleward salt and heat transport towards mid to lower latitude gondwana and cathasia margins the warm water currents and moisture along the margins of gondwana caused a rapid increase in the precipitation necessary to build significant ice sheets during the early middle sakmarian

transformation of dilative and contractive landslide debris into debris flows an example from marin county california abstract the severe rainstorm of january 3 4 and 5 1982 in the san francisco bay area california produced numerous landslides many of which transformed into damaging debris flows the process of transformation was studied in detail at one site where only part of a landslide mobilized into several episodes of debris flow the focus of our investigation was to learn whether the landslide debris dilated or contracted during the transformation from slide to flow the landslide debris consisted of sandy colluvium that was separable into three soil horizons that occupied the axis of a small topographic swale failure involved the entire thickness of colluvium however over parts of the landslide the soil a horizon failed separately from the remainder of the colluvium undisturbed samples were taken for density measurements from outside the landslide from the failure zone and overlying material from the part of the landslide that did not mobilize into debris flows and from the debris flow deposits the soil a horizon was contractive and mobilized to flows in a process analogous to liquefaction of loose granular soils during earthquakes the soil b and c horizons were dilative and underwent 2 to 5 volumetric expansion during landslide movement that permitted mobilization of debris flow episodes several criteria can be used in the field to differentiate between contractive and dilative behavior including lag time between landsliding and mobilization of flow episodic mobilization of flows and partial or complete transformation of the landslide

assessment of landslide triggering factors and occurrence using morphometric parameters in geyraz basin tokat northern turkey the geyraz stream is one of the tributaries of the yesilirmak river located within the southern of middle black sea section and enters the main river at tokat city centre geyraz is a basin that has experienced numerous landslide events in this study morphometric parameters of areas prone to landslide occurrence were investigated and computed in gis these parameters included the dissection index hypsometric integral drainage density stream power index and compound topographic index first and second orders in addition rocks slopes and frequencies of first and second order streams in subbasins were considered and their correlations were examined the moderate 15 20 and high slope 20 25 values with primarily clayey rocks schist and flysch correspond to high di and hi values a maximum number of first and second order streams and high landslide occurrence while very steep slopes lead to low di values and a low density of landslides results show that former landslides occurred in areas with di values of 0 1 0 15 moderately steep and steep slopes a maximum number of first and second order streams high stream frequency on clayey rocks schist and flysch cti values of 60 100 and spi values of 75 85 in other words landslide events are triggered by higher drainage frequency on primarily clayey rocks intense fluvial incision and medium high steep slopes the location of agricultural land in the landslide area reflecting lack of vegetation cover is another landslide triggering factor thus the study area was ranked in six different classes and risk was rated as very low low medium medium to high high and very high determination of areas prone to landslide occurrence and their triggering factors is important for regional planning with respect to basin management and hazard prevention

implications for timing of andean uplift from thermal resetting of radiation damaged zircon in the cordillera huayhuash northern peru abstract the cordillera huayhuash is a north south oriented range along the drainage divide of the northern peruvian andes the range has high topography with peaks in excess of 5500 m and the second highest peak in peru nevados yerupaja 6617 m bedrock is dominated by folded mesozoic miogeoclinal rocks unconformably overlain by mid tertiary volcanics intruded by late tertiary granitic rocks and silicic dikes zircon fission track zft and u th he zhe dating of zircons along a west east transect elucidates the thermal evolution of exhumed and uplifted rocks the stability of fission tracks in zircons is a function of single grain radiation damage in samples with grain to grain variability in radiation damage resetting results in variable resetting and multiple age populations low retentive zircons lrzs which have a partly disordered crystalline structure have significant radiation damage and a low temperature of annealing ca 180 200 c high retentive zircons hrzs which are nearly cry

spatio temporal patterns of historical shallow landslides in a volcanic area mt aso japan abstract the evaluation of spatially and temporally distributed records of translational shallow landslides in heterogeneous watersheds provides insights needed to understand disastrous processes recurrent slope instability events occurred between 1953 and 1998 in two watersheds of mt aso western japan this paper investigates 1 the spatio temporal characteristics of translational shallow landslides dimensions numbers densities and area subjected to failure observed at a particular location 2 dem based landform characteristics elevation slope angles curvatures and their control on landslide distribution and 3 rainfall characteristics the evaluation of the landslide history consequences and characteristics of spatially and temporally distributed landslides are based on the series of inventory maps for years 1954 1977 1990 and 1998 geologically the watersheds consist of pyroxene olivine andesite basalt lava pyroclastics deposits gravel sand and clay deposits originated from takadake nekodake and washigamine volcanoes during 45 years 1953 1998 a total of 619 and 976 numbers of shallow landslides have been recognized in the sakurakigawa and furuegawa watersheds respectively repeated sliding denuded a total surface area of 0 372 km 2 in the sakurakigawa watershed representing 35 of the watershed area similarly slides denuded a total of 0 534 km 2 in the furuegawa watershed representing 12 of the watershed area for example storm events of june 1953 and july 1990 with rainfall intensities of 49 and 61 mm h 1 respectively triggered numerous landslides about 25 and 47 of sakurakigawa and furuegawa watersheds respectively still bears the potential to produce landslides landslides were commonly observed where thick unconsolidated tephra layers and pyroclastics rocks overlain by thin tephra bed existed and for a slope inclination range of 30 35

a late miocene subtropical dry flora from the northern altiplano bolivia abstract a variety of evidence suggests that the altiplano of the central andes the second highest and largest plateau on earth underwent significant uplift in the late miocene pliocene the most important datum supporting recent uplift is a collection of the 10 66 0 06 ma jakokkota flora from west central bolivia which implies a paleoelevation no more than 1600 1200 m today the site has an elevation of almost 4000 m in order to test the reliability of this estimate the present study analyzes a new collection of the jakokkota flora from a lacustrine unit that is 0 2 0 5 myr younger than the previously analyzed collection from a fluvial unit climate estimates based on leaf morphology for the two collections are statistically indistinguishable the combined flora has a mean annual temperature of 21 5 2 0 c and a mean annual precipitation of 550 180 mm the similarity of the climate estimates for the two floras suggests that there was not a significant climate change between them nor a significant bias in the leaf morphology due to differing taphonomic processes the climate estimate for the combined flora thus presents a representative picture of the late miocene climate of the northern altiplano if one assumes that the climate of the tropics has not changed significantly since the late miocene as is suggested by marine isotopic data then the paleoclimate of the jakokkota flora implies a paleoelevation of 1160 600 m thus the jakokkota flora supports the hypothesis of a young age for the altiplano

foreland uplift during flat subduction insights from the peruvian andes and fitzcarrald arch abstract foreland deformation has long been associated with flat slab subduction but the precise mechanism linking these two processes remains unclear one example of foreland deformation corresponding in space and time to flat subduction is the fitzcarrald arch a broad ne sw trending topographically high feature covering an area of 4 105 km2 in the peruvian andean foreland recent imaging of the southern segment of peruvian flat slab shows that the shallowest part of the slab which corresponds to the subducted nazca ridge northeast of the present intersection of the ridge and the peruvian trench extends up to and partly under the southwestern edge of the arch here we evaluate models for the formation of this foreland arch and find that a basal shear model is most consistent with observations we calculate that 5 km of lower crustal thickening would be sufficient to generate the arch s uplift since the late miocene this magnitude is consistent with prior observations of unusually thickened crust in the andes immediately south of the subducted ridge that may also have been induced by flat subduction this suggests that the fitzcarrald arch s formation by the nazca ridge may be one of the clearest examples of upper plate deformation induced through basal shear observed in a flat slab subduction setting we then explore the more general implications of our results for understanding deformation above flat slabs in the geologic past

abrupt changes in the rate of andean plateau uplift from reversible jump markov chain monte carlo inversion of river profiles abstract knowledge of the rate of surface uplift of the central andean plateau provides important boundary conditions for regional geodynamic models and paleoclimate reconstructions here we present a fully nonlinear inverse method to extract the rock uplift history of the central andean plateau from the cotahuasi river and its tributaries our approach is based on an analytical solution to the stream power model that relates elevation to rock uplift history under the assumptions of constant climatic conditions in space and time and spatially invariant rock uplift we use a bayesian framework that allows us to quantify the full state of knowledge of model parameters i e uncertainties trade offs the erosional efficiency defines the landscape response time and this must be determined using independent data therefore using thermochronometric data from the cotahuasi ocona canyon which record rapid fluvial incision at 13 10 ma we calibrate our results to infer a rock uplift history for the north central andean plateau we infer a pulse of rock uplift between 25 and 10 ma at rates as high as 0 25 km my however the rock uplift rate inferred during this pulse is not as high as is predicted if the central andean plateau grew as a result of loss of unstable lithospheric mantle therefore our results are more consistent with models requiring gradual uplift of the central andean plateau

uplift of the western margin of the andean plateau revealed from canyon incision history southern peru we explore canyon incision history of the western margin of the andean altiplano puna plateau in the central andes as a proxy for surface uplift u th he apatite data show rapid cooling beginning at ca 9 ma and continuing to ca 5 1 ma in response to incision a minimum of 1 0 km of incision took place during that interval the youngest apatite date and a volcanic fl ow perched 125 m above the present valley fl oor dated at 2 261 0 046 ma 40 ar 39 ar show that an additional 1 4 km of incision occurred between ca 5 1 and 2 3 ma thus we infer that a total of at least 2 4 km or 75 of the present canyon depth was incised after ca 9 ma u th he zircon data collected along the same transect imply that the western margin of the plateau was warped upward into its present monoclinal form rather than uplift being accommodated on major surface breaking faults

the hydro mechanical behaviour of unsaturated pyroclastic soils an experimental investigation abstract an experimental investigation into the hydro mechanical behaviour of a pyroclastic silty sand was carried out in the framework of a research project on flowslides in pyroclastic soils in the campania region italy undisturbed soil samples were taken from the subsoil layers of a test site on a limestone relief mantled by a pyroclastic unsaturated soil cover the lab investigation was focused on the hydro mechanical behaviour of a pyroclastic silty sand originated from the ottaviano eruption of the somma vesuvius volcano some 8000 years ago the main features of the hydraulic hysteresis domain were evaluated and the matric suction range showing the peak saturation rate with respect to suction was identified using water retention data obtained by means of evaporation and soaking tests the mechanical behaviour of ottaviano pozzolana emerged from stress path controlled triaxial tests on saturated specimens and stress path and suction controlled triaxial tests on unsaturated specimens average soil skeleton stress and matric suction were adopted as stress variables to present and interpret the experimental results the effects of the unsaturated state on isotropic compressibility and on critical state shear strength are presented and discussed

impacts of andean uplift on the humboldt current system a climate model sensitivity study 1 using both an atmospheric global circulation model and a regional oceanic model we assess the impact of the andes uplift on the humboldt current system hcs with three topographic scenarios for the andes we show that the uplift played a crucial role in shaping the lower troposphere dynamics over the pacific ocean and in turn affected the physical characteristics of the system our results show that the uplift has triggered a marked southward shift of the hcs changing the latitudinal position of coastal upwelling areas as well as the strength of the south pacific gyre our oceanic modeling experiments show that the latitudinal pattern of sea surface temperatures is dramatically modified with reduced andes with anomalies reaching up to 3 c we discuss the feedbacks of these changes on south american climate as well as the potential onset of an altitudinal threshold that would have had triggered these changes

response of meteoric δ18o to surface uplift implications for cenozoic andean plateau growth abstract the timing and magnitude of surface uplift provide important constraints on geodynamic models of orogen formation oxygen isotope 18 o and mass 47 isotopolog 47 compositions from terrestrial carbonate sediments have been used with modern isotope and temperature lapse rates to infer past surface elevations of the andes however these paleoaltimetry interpretations are contentious because variations in the oxygen isotope composition in meteoric water 18 o p are caused by changes in elevation orographic and regional climate here we use a limited domain isotope tracking general circulation model to simulate changes in 18 o p and isotopic lapse rates in response to andean surface uplift and to re evaluate 18 o and 47 changes in late miocene carbonates previously associated with rapid andean growth results indicate that andean surface uplift leads to changes in low level atmospheric circulation and an increase in precipitation along the eastern andean flank which influences isotopic source and amount effects simulated changes in andean 18 o p are not systematic with an increase in surface elevation but are instead a function of orographic thresholds that abruptly change regional climate a 18 o p decrease of 5 over the central andes and an increase in isotopic lapse rates up to 0 8 km 1 coincide with andean surface uplift from 75 to 100 of modern elevation these changes in the isotopic signature could account for the entire 3 4 18 o depletion in late miocene carbonate nodules and suggest an andean paleoelevation of 3000 m 75 of modern elevations before 10 ma

soil water balance in an unsaturated pyroclastic slope for evaluation of soil hydraulic behaviour and boundary conditions flowslides in granular soils pose a major threat to life and the environment their initiation in unsaturated soils is regulated by rainfall infiltration which reduces the matric suction and hence shear strength analysis of such phenomena is of strategic importance especially when it aims to mitigate landslide risk by means of early warning systems ewss in this framework physically based models need to reproduce the hydro mechanical behaviour of the slopes through numerical analyses whose main uncertainty concerns the hydraulic conditions at the boundaries of the studied domain and hydraulic conductivity functions of unsaturated soils hence consummate knowledge of both these factors is absolutely necessary for efficient predictions in this paper hydraulic boundary conditions and hydraulic conductivity functions are investigated at the scale of the slope through an application of soil water balance based on in situ monitoring at the test site of monteforte irpino southern italy meteorological data matric suction and soil water content measurements were collected over four years at the test site the soil water balance was analysed on a seasonal time scale with regard to the whole pyroclastic cover resting on the steep limestone substratum infiltration and runoff are estimated interaction between the soil cover and the substratum is investigated and the hydraulic conductivity functions operative at the site scale are defined

rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere abstract the oxygen isotopic compositions of carbonates deposited in the northern altiplano demonstrate a rapid change in late miocene time which we attribute to an increase in elevation rainfall samples over an elevation transect adjacent to the altiplano of northern bolivia display a systematic decrease in mean annual 18 o values and define a local 18 o vs altitude gradient r gonfiantini m a roche j c olivry j c fontes g m zuppi the altitude effect on the isotopic composition of tropical rains chem geol 181 2001 147 167 which we apply to paleo meteoric water values determined from carbonates age constraints from magnetostragraphy and paleoelevation estimates suggest surface uplift of 2 5 to 3 5 km occurred between 10 3 ma and 6 8 0 4 ma when the altiplano rose to its current elevation only the removal of dense eclogitic lower crust and mantle lithosphere can generate a change of this magnitude and rapidity this change coincides with an 30 decrease in the rate of convergence between the south america and nazca plates and the propagation of deformation into the eastern subandean zone which we infer to have resulted from the increase in the force per unit length applied by the elevated andean plateau to the surrounding lowlands

interplay of rheology and entrainment in debris avalanches a numerical study flow type landslides are a major global hazard they occur worldwide and are responsible for a large number of casualties significant structural damage to property and infrastructure and economic losses the features of debris avalanches are particularly important as they involve open slopes and affect triangular source areas when initial slides turn into avalanches through further failures or eventual soil entrainment in this paper the propagation stage of debris avalanches is numerically modelled to provide information such as the propagation pattern of the mobilized material and its velocity thickness and run out distance the use of a depth integrated model has the following advantages i it adequately accommodates the irregular topography of real slopes which greatly affects the evolution of the propagation stage and ii it is less time consuming than full three dimensional approaches the model is named geoflow sph and has previously been applied to theoretical experimental and re

late permian middle jurassic lithospheric thinning in peru and bolivia and its bearing on andean age tectonics abstract integrated studies and revisions of sedimentary basins and associated magmatism in peru and bolivia 8 22 s show that this part of western gondwana underwent rifting during the late permian middle jurassic interval rifting started in central peru in the late permian and propagated southwards into bolivia until the liassic dogger along an axis that coincides with the present eastern cordillera southwest of this region lithospheric thinning developed in the early jurassic and culminated in the middle jurassic producing considerable subsidence in the arequipa basin of southern peru this 110 ma long interval of lithospheric thinning ended 160 ma with the onset of malm earliest cretaceous partial rift inversion in the eastern cordillera area the lithospheric heterogeneities inherited from these processes are likely to have largely influenced the distribution and features of younger compressional and or transpressional deformations in particular the altiplano plateau corresponds to a paleotectonic domain of normal lithospheric thickness that was bounded by two elongated areas underlain by thinned lithosphere the high eastern cordillera of peru and bolivia results from late oligocene neogene intense inversion of the easternmost thinned area

quantifying the three dimensional effects of anisotropic soil horizons on hillslope hydrology and stability abstract rainfall induced shallow landslides cause significant damage involving loss of life and property many hydrological processes such as rainfall infiltration soil water dynamics and slope stability are controlled by unsaturated soil properties such as unsaturated hydraulic conductivity natural soils often exhibit a certain degree of anisotropy in hydraulic conductivity due to stratification and compaction mechanisms in soil formation processes in this paper we investigate the effect of soil hydraulic conductivity anisotropy shca on hillslope hydrology and stability using a three dimensional hydrological model coupled with a probabilistic infinite slope stability model the model is applied in two independent case studies the first aims to quantify the combined effect of different anisotropy ratios lateral normal saturated hydraulic conductivity and hillslope morphologies convex concave and planar on slope stability anisotropy ratios are assumed in this case higher than one 1 2 10 results show that increasing the anisotropy ratio from 1 to 10 anticipates the failure time from 12 to 9 h after the start of rainfall and that in concave morphologies the unstable area tends to be wider than planar and convex the second application aims to simulate the soil moisture dynamic and the probability of failure at different depths 100 500 and 900 mm of a stratified volcanic soil making leverage on the model flexibility to accommodate shca no assumptions are made on the anisotropy ratio in this case study our results based on model parameter calibration and verification against in situ soil moisture measurements during the year 2009 showed good model performance in simulating the soil moisture dynamic kling gupta efficiency higher than 0 78 and confirmed no failure for the simulated year the promising results support the aspiration that the physically based hydrological model can complement and improve the current predictions of landslide early warning systems

direction and timing of uplift propagation in the peruvian andes deduced from molecular phylogenetics of highland biotaxa abstract physical paleoaltimetric methods are increasingly used to estimate the amount and timing of surface uplift in orogens because the rise of mountains creates new ecosystems and triggers evolutionary changes biological data may also be used to assess the development and timing of regional surface uplift here we apply this idea to the peruvian andes through a molecular phylogeographic and phylochronologic analysis of globodera pallida a potato parasite nematode that requires cool temperatures and thus thrives above 2 0 2 5 km in these tropical highlands the peruvian populations of this species exhibit a clear evolutionary pattern with deeper more ancient lineages occurring in andean southern peru and shallower younger lineages occurring progressively northwards genetically diverging g pallida populations thus progressively colonized highland areas as these were expanding northwards demonstrating that altitude in the peruvian andes was acquired longitudinally from south to north i e in the direction of decreasing orogenic volume this phylogeographic structure is recognized in other independent highland biotaxa and point to the central andean orocline cao as the region where high altitudes first emerged moreover molecular clocks relative to andean taxa including the potato tomato group consistently estimate that altitudes high enough to induce biotic radiation were first acquired in the early miocene after calibration by geological and biological tie points and intervals the phylogeny of g pallida is used as a molecular clock which estimates that the 2 0 2 5 km threshold elevation range was reached in the early miocene in southernmost peru in the middle and late miocene in the abancay segment nw southern peru and from the latest miocene in central and northern peru although uncertainties attached to phylochronologic ages are significantly larger than those derived from geochronological methods these results are fairly consistent with coeval geological phenomena along the peruvian andes they strongly suggest that orogenic volume initially developed in the cao during most of the miocene until a breakthrough in the latest miocene allowed the northward propagation of crustal thickening into central and northern peru possibly by ductile crustal flow from the cao such a combined phylogeographic and phylochronologic approach to regional uplift opens perspectives to estimate the direction s and timing of acquisition of altitude over other cenozoic orogens

a scenario for late neogene andean shortening transfer in the camisea subandean zone peru 12 s implications for growth of the northern andean plateau precise knowledge of the timing of deformation in the subandean zone of the andean plateau is a prerequisite for deciphering the late neogene growth of the andean plateau in this paper we report new apatite fission track aft and vitrinite reflectance ro data for a regional balanced cross section of the camisea basin in the central peruvian subandean zone adjacent to the northern andean plateau the balanced cross section shows that the structure of this basin is characterized by a broad internal passive roof duplex and external thrust related anticlines the balanced cross section restoration shows 53 km 39 of total horizontal shortening we sampled paleozoic to cenozoic sedimentary strata for aft and ro analyses along the 4 km thick vertical profile of the mainique back thrust passive roof thrust the innermost preserved subandean structure young components of aft ages are spread between ca 6 ma and ca 24 ma a break in the slope in the aft ages determines the geometry of the miocene partial annealing zone and the exhumation of the mainique back thrust at ca 6 ma sequential restoration calibrated by aft and ro data indicates that the last 23 km horizontal shortening were accommodated by the camisea thrust system over the past 6 m y giving a mean shortening rate of 3 8 mm yr using this shortening rate for the first 30 km horizontal shortening we calculate that the andean shortening transfer into the peruvian subandean zone initially started at ca 14 ma this result suggests that the transfer of shortening from the northern andean plateau to the subandean zone occurred prior to the removal of dense lithosphere previously reported to have occurred between ca 10 ma and ca 7 ma we rather propose that the late neogene growth of the northern andean plateau mostly resulted from a continuous crustal shortening combined with lower crustal flow

a study of the correlation between electrical resistivity and matric suction for unsaturated ash fall pyroclastic soils in the campania region southern italy in the territory of the campania region southern italy critical rainfall events periodically trigger dangerous fast slope movements involving ashy and pyroclastic soils originated by the explosive phases of the mt somma vesuvius volcano and deposited along the surrounding mountain ranges in this paper an integration of engineering geological and geophysical measurements is presented to characterize unsaturated pyroclastic samples collected in a test area on the sarno mountains salerno and avellino provinces campania region the laboratory analyses were aimed at defining both soil water retention and electrical resistivity curves versus water content from the matching of the experimental data a direct relationship between electrical resistivity and matric suction is retrieved for the investigated soil horizons typical of an ash fall pyroclastic succession the obtained relation turns out to be helpful in characterizing soils up to close saturation which is a critical condition for the trigger of slope failure in such a regime the water content and the matric suction have small variations while electrical resistivity variations can be appreciated in a larger range of values for this reason besides suction measurements on very small soil volumes through classical tensiometers our analyses suggest the direct monitoring of in situ electrical resistivity values as an effective tool to recognise the hydrological state of larger and more representative soil volumes and to improve early warning of dangerous slope movements

building physically based models for assessing rainfall induced shallow landslide hazard at the catchment scale the case study of the sorrento peninsula italy the assessment of rainfall induced shallow landslide hazards at the catchment scale poses a significant challenge traditional empirical approaches for landslide hazard assessment often assume that

long term investigations on the pore pressure regime in saturated and unsaturated sloping soils abstract pore pressure changes play a major role in the stability of natural slopes whose safety factor value is usually much smaller than that generally accepted in any other geotechnical problem correct assessment of potential seasonal pore pressure distributions is therefore a crucial issue in slope stability analysis based on long term monitoring of some natural slopes this paper compares the pore pressure distribution recorded in saturated fine grained deposits and in shallow unsaturated granular covers both monitored in southern italy in spite of the expected differences the soils display some common features in particular from december to mid may wet period in all examined cases the pore water pressures are quite constant over a monthly scale thus an essentially steady state pore pressure condition establishes it is in this phase which is characterised by an essentially downward flux that the safety factor drops to its lowest yearly value finally a simplified method is adopted to model the steady state pore pressure during the wet period and to calculate the average rain infiltration in equilibrium with the steady state condition the results thereby obtained are compared with the findings of an advanced approach based on the hydrological balance

a 3 d geodynamic model of lateral crustal flow during andean mountain building although the andes are believed to have resulted mainly from crustal shortening the shortening history remains debated and appears to require lateral along strike crustal flow three dimensional viscous flow modeling shows that within geological uncertainties the andes may have been produced by either neogene shortening alone or with significant pre neogene shortening these scenarios require major along strike crustal flow and predict significantly different histories of uplift and crustal motion

response to comment on rapid uplift of the altiplano revealed through 13 c 18 o bonds in paleosol carbonates clumped isotope thermometry measurements of carbonate samples deposited in the bolivian altiplano as early as 28 5 million years ago and buried up to 5000 meters deep exhibit no relationship between burial depth and apparent temperature and largely yield temperatures within error of plausible earth surface conditions these results counter the predictions of sempere et al and support our previous conclusions regarding the uplift of the altiplano

mean annual temperature estimation based on leaf morphology a test from tropical south america abstract are models that predict mean annual temperature mat from leaf morphology applicable globally fifteen models that predict mat from leaf morphology were tested on thirty floral samples from tropical south america to determine the degree to which models based on published data that are primarily from other regions are applicable to floras from tropical south america the models included are based on regional data from north america south america and asia of the fifteen models tested five are simple linear regressions six are multiple linear regressions two are canonical correspondence analyses and two are correspondence analyses followed by nearest neighbor analyses for the seven modern floras with mat 21 c every model overestimates mat for the 23 modern floras with mat 21 c all models produce variable results without a systematic error the range of average model errors is 2 7 7 3 c while the absolute extremes of error are 0 and 15 1 c average 95 predictive confidence intervals range from 1 6 to 6 9 c predicted mat falls within the published standard error of the model for 0 67 of the south american test floras evaluating the seven sites with mat 21 c separately from the 23 sites with mat 21 c shows that no equation accurately estimates mat of the majority of low temperature sites but that four equations accurately estimate 50 of high temperature sites the results suggest that at least for sites of unknown or high elevation mean annual temperature of fossil floras from tropical south america may be better predicted from models based on the leaf morphology of tropical south american floras

paleoelevation reconstruction using pedogenic carbonates paleoelevation reconstruction using stable isotopes although a relatively new science is making a significant contribution to our understanding of the recent growth of the world s major orogens in this review we examine the use of both light stable isotopes of oxygen and the new clumped isotope 47 carbonate thermometer in carbonates from soils globally the oxygen isotopic composition 18 o of rainfall decreases on average by about 2 8 km of elevation gain this effect of elevation will in turn be archived in the 18 o value of soil carbonates and paleoelevation can be reconstructed provided 1 temperature of formation can be estimated 2 the effects of evaporation are small 3 the effects of climate change can be accounted for and 4 the isotopic composition of the carbonate is not diagenetically altered we review data from modern soils to evaluate some of these issues and find that evaporation commonly elevates 18 o values of carbonates in deserts an effect that would lead to underestimates of paleoelevation some assessment of paleoaridity using qualitative indicators or carbon isotopes from soil carbonate is therefore useful in evaluating the oxygen isotope based estimates of paleoelevation sampling from deep 50 cm in paleosols helps reduce the uncertainties arising from seasonal temperature fluctuations and from evaporation the new clumped isotope 47 carbonate thermometer expressed as 47 offers an independent and potentially very powerful approach to paleoelevation reconstruction in contrast to the use of 18 o values nothing need be known about the isotopic composition of water from which carbonate grew in order to estimate of temperature of carbonate formation from 47 values using assumed temperature lapse rates with elevation paleoelevations can thereby be reconstructed case studies from the andes and tibet show how these methods can be used alone or in combination to estimate paleoelevation in both cases the potential for diagenetic alteration of primary carbonate values first has to be assessed clear examples of both preservation and alteration of primary isotopic values are available from deposits of varying ages and burial histories 47 values constitute a relatively straightforward test since any temperature in excess of reasonable surface temperatures points to diagenetic alteration for 18 o values preservation of isotopic heterogeneity between different carbonate phases offers a check on diagenesis results of these case studies show that one area of south central tibet attained elevations comparable to today by the late oligocene whereas 2 7 0 4 km of uplift occurred in the bolivian altiplano during the late miocene

recognition classification and mechanical description of debris flows abstract various types of flow or mass movement involving water and sediments occur on steep slopes in mountainous areas among them debris flows are peculiar events during which a large volume of a highly concentrated viscous water debris mixture flows through a stream channel throughout the world these phenomena cause considerable damage but remain poorly understood although a basic knowledge is already available concerning their recognition and propagation firstly a synthesis of the useful practical criteria of recognition is proposed debris flows must be seen as intermediate phenomena between hyperconcentrated flows intense bed load transport and landslides separated from them by sharp transitions of some characteristics celerity deposit nature and flow type two parameters solid fraction and material type thought to be appropriate for a sound and practical classification are brought out and the corresponding complete classification of flow and mass movements in mountain areas is presented two extreme debris flow types are thus distinguished muddy debris flows and granular debris flows a critical review of recent advances in debris flow dynamic is then proposed it is pointed out that adequate work must be carried out in the field of non newtonian fluid mechanics in particular one fundamental rheological property of debris flow materials is the yield stress which explains thick deposits on steep slopes and can be inferred from field measurements furthermore it can be used to estimate viscous dissipation within the bulk during flow relevant models predicting muddy debris flow dynamics are already available whereas further progress is needed concerning granular flows

paleomagnetic tracking of mountain building in the peruvian andes since 10 ma 1 we report paleomagnetic data from 73 sites 628 samples of upper oligocene to pliocene rocks from central and northern peru the data indicate that the subandean zone has not experienced vertical axis rotation since the upper oligocene whereas the coast and the western cordillera record a coherent pattern of counterclockwise rotations emplaced in the last 10 ma this pattern can best be explained by two competing hypotheses 1 a propagation in rotations from the bolivian orocline toward the north or 2 a more punctual and widespread event linked to subduction of the nazca ridge that caused the rotations on the basis of the time space relationship of paleomagnetic rotations deformation magmatism and nazca south america plate convergence the latter appears more likely moreover because the rotations north of the abancay deflection 15 5 s are synchronous with deformation and exhumation they indicate that major mountain building in the peruvian andes has occurred since 10 ma finally we suggest that a succession of aseismic ridge subduction events played an important role in shaping the modern topography of the andean chain

an integrated procedure to evaluate rheological parameters to model debris flows abstract in the present paper the problem of modeling the propagation of debris flow using suitable rheological parameters is considered a new procedure is proposed based on field observations laboratory investigations and numerical analysis the back analysis of a debris flow event that occurred in the campania region southern italy was used to investigate the reliability of the assumed rheological parameters the well known bingham constitutive equation was chosen to model the behavior of the equivalent flow mixture numerical analysis was conducted using dan w a code based on a single phase depth averaged continuum mechanics approach the results show that extrapolating model parameters only from laboratory experiments may lead to inaccurate predictions instead when the rheological parameters are assumed according to stress field observations and experimental data the model satisfactorily replicates the case studies such conclusion suggests that the calibration of model parameters using an integrated approach may be applicable for field scale debris flow simulations and can yield useful information about the dynamics of flows to be investigated the accuracy of this approach was demonstrated by the numerical prediction of other fifty events that occurred in the same area

rapid regional surface uplift of the northern altiplano plateau revealed by multiproxy paleoclimate reconstruction the central altiplano is inferred to have experienced 2 5 1km surface uplift between 10 and 6 ma while the southern altiplano experienced a similar magnitude of surface uplift that began earlier between 16 and 9 ma to properly constrain the along strike timing of the altiplano plateau surface uplift it is necessary to know how and when the northernmost part of the altiplano plateau evolved we reconstruct the paleoclimate and infer the corresponding paleoelevation from the miocene pliocene deposits of the descanso yauri basin 14 15 s in the northernmost part of the altiplano plateau using 4 different proxies including carbonate clumped isotope composition i e 47 values carbonate 18 o c leaf wax d wax and pollen assemblages from paleosol lacustrine and palustrine carbonates and organic rich sediments the isotopic signatures reflect past climate conditions of mean annual air temperature 47 and meteoric water isotope values 18 o c d wax our results show that the northernmost plateau remained at low elevation 0 9 0 8 to 2 1 0 9km until late miocene time 9 ma characterized by 15 c warmer than modern temperature mean annual air temperature of 23 4 c 2 low elevation vegetation and precipitation signature with reconstructed 18 o mw vsmow of 8 3 2 0 2 from carbonate 18 o c and 8 6 1 8 2 from leaf wax d wax modern elevations of 4 km were not reached until 5 4 1 0ma as indicated by a negative shift in d wax vsmow from 143 4 12 8 2 to 209 2 21 1 2 between 9 1 0 7 and 5 4 1 0ma the timing of surface uplift of the northernmost altiplano is consistent with the evidence for late miocene surface uplift of the central altiplano 16 19 s between 10 and 6 ma and indicates that regional scale uplift in the northern central plateau significantly postdates the onset of surface uplift in the southern altiplano 19 22 s between 16 and 9 ma these results are consistent with piecemeal removal of the lower dense lithosphere combined with possible lower middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the altiplano plateau

evaluation of landslide reactivation a modified rainfall threshold model based on historical records of rainfall and landslides abstract this study proposes a modification of the conventional threshold model for assessing the probability of rainfall induced landslide reactivation the modification is based on the consideration that exceedance of a pre determined rainfall threshold is a necessary but not sufficient condition to reactivate a landslide the proposed method calculates the probability of reactivation as a function of the probability of exceedance of a pre determined rainfall threshold as well as the probability of occurrence of a landslide after such exceedance the data for the calculation were obtained from historical records of landslides and rainfall the method was applied to two complex landslides san donato and la salsa involving fine grained debris in the southern section of the apennine foredeep the minimum rainfall threshold triggering landslide reactivation on the two slopes was determined by examining rainfall patterns during the 180 days preceding the slide events for the san donato and la salsa landslides the minimum triggering threshold consists of rainfall events lasting 15 days with cumulated rainfall exceeding 150 and 180 mm respectively based on hydrological and statistical analyses the annual probabilities of exceeding the thresholds were estimated to be 0 38 and 0 25 respectively during the period from 1950 to 1987 the minimum threshold was exceeded 14 times and four reactivations occurred at san donato whereas the threshold was exceeded 10 times and three reactivations occurred at la salsa hence the probabilities of landsliding after exceedance of the minimum rainfall threshold are 4 14 and 3 10 respectively finally annual reactivation probabilities were calculated to be 0 11 and 0 08 respectively the reliability of the minimum rainfall threshold was tested by i simulating variations in the stress strain behavior of the slopes as a result of fluctuations in the water table from normal to extreme values and ii analyzing the results of continuous multi year monitoring of pore pressure and rainfall variations on a slope composed of dominantly fine grained debris

sph run out modelling of channelised landslides of the flow type abstract rainfall induced channelised landslides of the flow type may reach high velocities and travel large run out distances the proper modelling of the propagation stage is fundamental to risk analysis and management the correct selection of mass rheology is fundamental to this procedure and the variation of pore water pressures and bed entrainment along the landslide path must also be properly taken into account all of these processes can be consistently simulated through a quasi 3d depth integrated coupled sph model in this study such a model is applied to a relevant case history from southern italy for which an advanced dataset is available the numerical results provide a satisfactory back analysis of the case history and clearly indicate that the bed entrainment rate and the extent of the erodible areas affect the propagation paths the velocities and the deposition heights on the basis of the results general insights into this type of landslide are discussed with reference to different hypotheses for propagation modelling

paleomagnetic evidence for rapid vertical axis rotation in the peruvian cordillera ca 8 ma paleomagnetic results from 31 neogene sites in the peruvian andes yield primary magnetizations as demonstrated by positive fold and reversal tests strata dated as 18 9 ma record a significant counterclockwise rotation 11 5 whereas unconformably overlying younger strata 7 6 ma are not rotated the age of rotation thus is between 9 and 7 ma a period that coincides with the widespread quechua 2 deformation phase moreover eight independent studies on 107 9 ma rocks from peru between 9 s and 15 s reveal similar and significant rotations 15 6 this suggests that the region rotated during a 2 m y period of deformation ca 8 ma when the andes underwent rapid uplift and important deformation commenced in the subandean zone

new angles on south atlantic opening existing models of relative motion between the south america and africa plates significantly misrepresent the azimuth of lower cretaceous seafloor spreading in the south atlantic ocean an improved model is derived from fits of fracture zones magnetic reversal anomalies and the edges of a rifted large igneous province at the northeast georgia rise and agulhas plateau an absolute date for this rifting event is not known but by assuming least change in spreading rates during magnetic chron c34 rifting can be estimated to have occurred at 100 ma this modelling demands a plate divergence history that involves diachronous opening of the south atlantic consistent with published estimates of the ages of breakup from sedimentary basins on the south american and african passive margins the diachronous opening lasts approximately 40 million years during which time it must be accommodated by significant intracontinental deformation a reconstruction using the intra c34 rotation also illustrates the earliest possibility for direct deep water connection between the central and south atlantic oceans one further consequence of this model is that a total reconstruction derived from it and closure of the central atlantic between north america and africa suggests that the venezuelan and gulf of mexico basins may be conjugates formed during the earliest opening of the central atlantic and not separate marginal basins

an integrated geological geotechnical and geophysical approach to identify predisposing factors for flowslide occurrence abstract this study combines geological geotechnical and geophysical analyses to construct a 3d model of the subsoil based on a significant amount of data collected at a test site in the lattari mountain range in southern italy several investigation techniques were applied to study the spatial variability of the local stratigraphic setting and relevant geophysical and geotechnical parameters at the slope scale by integrating field and laboratory measurements such as geological logs soil sampling 2d and 3d electrical resistivity tomography surveys time domain reflectometry profiles and characteristic curves of electrical resistivity vs saturation degree the continuous stratigraphy of the pyroclastic cover in question was reconstructed and 3d models of effective saturation degree in different pyroclastic horizons were retrieved as the proposed procedure is applied to study flowslide initiation the test site was implemented on a 32 slope affected by historical flowslides the following factors predisposing to flowslides were identified steep stratigraphic contact between shallower soils and bedrock impermeable layers that buffer the draining of the fractured limestone preferential rainwater infiltration paths and spatial distribution of water content in the soil

comment on rapid uplift of the altiplano revealed through 13c 18o bonds in paleosol carbonates based on stable isotope measurements ghosh et al reports 27 january 2006 p 511 concluded that the bolivian altiplano uplifted 3 to 4 kilometers between 10 3 and 6 7 million years ago as a result of gravitational loss of dense lithosphere this result stands at odds with current geological knowledge of the central andes and we propose a test for the reliability of the paleoaltimetry method

reply to comment on rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere by garzione et al 2006 earth planet sci lett 241 2006 543 556

regional scale modelling of shallow landslides with different initiation mechanisms sliding versus liquefaction abstract rainfall induced landslides can result from different soil failure mechanisms each leading to slope instabilities characterized by varying times and depths of occurrence this paper discusses the performance of a physically based model for the spatially distributed analysis of landslide susceptibility the model allows the simultaneous assessment of two failure modes frictional slips and liquefaction induced flowslides the underlying mechanical formulation relies on stability principles for unsaturated soils while infiltration is treated as a transient process described by the richards equation the model has been applied to a series of landslides occurred in 1998 in campania italy using laboratory data to constrain the input parameters the analyses provide spatial and temporal patterns of landslide initiation consistent with field evidences in that they capture most of the affected landslide source areas and predict a temporal evolution of instabilities in agreement with reported failure times similar to available regional inventories the computed fraction of flowslides corresponds to 75 of the total unstable area while the resulting ratio between success and error indices is twice as large as those reported in other studies for the same site parametric analyses conducted by varying the hydraulic conductivity ks have pointed out a strong interplay between the dynamics of infiltration the mode of slope instability and the depth of failure in particular it has been found that low values of ks promote shallow flowslides due to moisture perching and high saturation at the surface while larger values of ks favor deeper infiltration fronts and frictional slips initiating at higher suction the comparison between these scenarios showed that simulations based on calibrated hydraulic properties encompass the widest distribution of failure depths thus reproducing more accurately the typical landslides of the site

late oligocene early miocene major tectonic crisis and related basins in bolivia recent advances in biochronology geochronology magnetostratigraphy structural geology and basin analysis make untenable the traditional correlation of the first major andeanage deformational episode in bolivia with the middle eocene incaic tectonic phase defined in central peru and instead demonstrate that the episode took place in late oligocene and early miocene time this major tectonic crisis resulted in contemporary development of the subandean external foreland basin and altiplano intermontane basin which were separated by the initiation of thrusting in the present cordillera oriental area the deformation suggests that the bolivian orocline began to develop at that time it is likely that this tectonic upheaval is genetically linked to the marked increase in rate of plate convergence produced by the contemporaneous breakup of the farallon plate

a latest carboniferous warming spike recorded by a fusulinid rich bioherm in timor leste implications for east gondwana deglaciation abstract during the late paleozoic and early mesozoic timor lay in the northern part of the north south east gondwana rift system along which the western margin of australia later developed discovery of a latest gzhelian bioherm in the central highlands of timor leste has implications for latest carboniferous earliest permian climate history and deglaciation in basins further south in the rift system limestone outcrop of the maubisse formation near the village of kulau is recognized as a bioherm with a massive lower unit including reef framework at the base and a bedded grainstone upper unit the bioherm developed on a basalt substrate in warm shallow water as indicated by photozoan assemblages in the massive lower unit foraminifera belonging to 17 genera are recorded from the bioherm these include representatives of the families biseriamminidae biwaellidae bradyinidae cornuspiridae lasiodiscidae palaeotextulariidae pseudotaxidae ozawainellidae schubertellidae schwagerinidae staffellidae and textrataxidae twenty one species have been referred to known types and 12 species are left in open nomenclature the assemblage probably belongs within the uppermost gzhelian schwagerina robusta ultradaixina bosbytauensis zone although a possible lowest asselian correlation cannot be excluded the bioherm is the oldest carbonate unit so far recorded from the maubisse formation and the oldest sedimentary unit biostratigraphically dated in timor the dominantly heterozoan composition of the skeletal component of the limestone except for the basal photozoan assemblage and the taxonomic diversity of the larger foraminifera suggest a subtropical environment consistent with a paleolatitude of about 40 s the late pennsylvanian was a time of glaciation that in australia is represented by a significant stratigraphic hiatus in basins to the south of timor in the east gondwana rift system the development of the kulau bioherm during the latest gzhelian may have coincided with a global warming spike that led to rapid melting of continental ice sheets and a substantial influx of glacigene sediment alternating diamictite and mudstone in the southern basins

coupled tectonic evolution of andean orogeny and global climate abstract the largest tectonic relief breaking the earth s surface 13 km vertically is at the subduction margin of the andes which generates routinely megathrust earthquakes mw 8 5 and drives the paradigmatic andean orogen here we present key geologic evidence to reassess first order features of geomorphology and tectonics across the central andes where the orogen includes the altiplano plateau and attains its maximum integrated height and width the andean subduction margin has a stepped morphology dominated by the low relief atacama bench which is similar to a giant uplifted terrace slopes gently over a width of 60 100 km from the andes to the pacific and runs over more than 1000 km of coastal length we find that the genesis of stepped morphology at the andean seaboard is due to concomitant development of large west vergent thrusts parallel to the subduction interface and increasing aridity in the atacama desert which keeps an unprecedented large scale record of interplaying tectonics and cenozoic climate change incorporating our results with published geological knowledge demonstrates that andean orogeny is characterized by trench perpendicular bivergent and trench parallel bilateral growth over the past 50 myr associated with positive trench velocity toward the continent trench advance and subduction of a wide slab under south america we hypothesize that a global plate tectonic reorganization involving long lasting viscous mantle flow has probably forced both andean orogeny and global climate cooling since 50 ma in contrast two important stepwise pulses of increasing aridity and trench perpendicular andean growth appear to be results of changes in erosion rates due to global late eocene and middle miocene cooling events

investigation on rainwater infiltration into layered shallow covers in pyroclastic soils and its effect on slope stability abstract in recent years a number of flowslides and debris flows triggered by rainfall affected a wide mountainous area surrounding the piana campana southern italy the involved slopes are covered with unsaturated air fall layered pyroclastic deposits which stability is guaranteed by the contribution of suction to shear strength to understand the mechanisms of infiltration and to assess the soil suction distribution in such layered deposits infiltration experiments have been carried out in small scale slopes the interpretation of the results has been made with the aid of a 2d mathematical model the results highlight that the presence of coarse textured unsaturated pumiceous layers interbedded between finer ashy layers can delay the wetting front advancement thus initially confining the infiltration process within the uppermost finer layer a diversion of the flow from the vertical towards the slope direction occurs when the soil approaches saturation however whereas a high hydraulic gradient establishes across pumices water infiltration into the deepest layer begins and part of the water crosses the pumices before the complete saturation of the uppermost soil profile

oligocene miocene age of aridity in the atacama desert revealed by exposure dating of erosion sensitive landforms the age of onset of hyperaridity in the atacama desert chile which is needed to validate geological and climatological concepts has been heretofore uncertain measurement of cosmogenic 21 ne in clasts from erosion sensitive sediment surfaces in northern chile shows that these surfaces have been barely affected by erosion since 25 ma surface exposure ages of sediment clasts give replicate values at 25 20 and 14 ma and individual values at 37 and 9 ma predominantly hyperarid conditions are required to preserve these oldest continuously exposed surfaces on earth our findings are compatible with the hypothesis that the onset of aridity in the atacama desert could be the reason for rather than the consequence of uplift of the high andes

little ice age debris lobes and nivation hollows inside ubehebe crater death valley california analog for mars craters the 250 m deep ubehebe crater is the youngest 1000 years and largest 800 m wide phreatomagmatic crater of the ubehebe maar field of northern death valley california usa the crater is blanketed by loose unconsolidated ejecta debris and prominent tongue shaped steep fronted debris lobes up to 200 m long occur at the base of the crater s steep northeast facing interior slope geomorphological observations sedimentological analysis of outcrops and a ground penetrating radar survey show the largest lobe to be composed of downslope dipping progradational beds of ejecta resulting from repeated downslope avalanching grain flow and cohesive debris flow inconsistent with an origin of the lobe as a singular coherent slump or flow large oval depressions on the upper surface of lobes are interpreted as relict nivation hollows occupied by former seasonal snow patches during recent little ice age cooling c 700 year bp when numerous rock glaciers and other periglacial landforms formed at high elevations in surrounding mountains lobes are interpreted as protalus ramparts formed when loose non cohesive ejecta from the steep unstable backwall of the crater moved downslope across snow patches and accumulated around their outer margins snow patch and lobe formation is considered to be a function of the local aspect related meteorology of the crater s interior involving shading of northeast facing interior slopes radiative cooling and ponding of cold air enhanced snow accumulation in the lee of the steep backwall combined with the availability of large volumes of loose ejecta ubehebe crater and its lobes expand the geomorphic record of cool climate processes in death valley the most well known being the winter ice facilitated sliding boulders of racetrack playa having formed in an extreme environment lobes offer an accessible terrestrial analog for poorly understood debris lobes within martian impact craters

testing the sequence stratigraphy model response of fusulinacean fauna to sea level fluctuations examples from pennsylvanian and cisuralian of the pricaspian southern urals region

horizontal subduction zones convergence velocity and the building of the andes we discuss the relationships between andean shortening plate velocities at the trench and slab geometry beneath south america although some correlation exists between the convergence velocity and the westward motion of south america on the one hand and the shortening of the continental plate on the other hand plate kinematics neither gives a satisfactory explanation to the andean segmentation in general nor explains the development of the bolivian orocline in paleogene times we discuss the cenozoic history of horizontal slab segments below south america arguing that they result from the subduction of oceanic plateaus whose effect is to switch the buoyancy of the young subducting plate to positive we argue that the existence of horizontal slab segments below the central andes during eocene oligocene times and below peru and north central chile since pliocene resulted 1 in the shortening of the continental plate interiors at a large distance from the trench 2 in stronger interplate coupling and ultimately 3 in a decrease of the trenchward velocity of the oceanic plate present day horizontal slab segments may thus explain the diminution of the convergence velocity between the nazca and south american plates since late miocene

velocity and runout simulation of destructive debris flows and debris avalanches in pyroclastic deposits campania region italy the campanian apennines are characterized by the presence of monocline ridges mainly formed by limestone during the periods of volcanic activity of the somma vesuvius and phlegrean fields the ridges were mantled with pyroclastic materials in varying thickness the pyroclastics have been involved in destructive landslides both in historical time and in the recent past 1997 1998 1999 the landslides occur following intense and prolonged rainfalls in some cases landslides extended up to 4 km into the surrounding lowlands and reached towns causing severe destruction and over 200 deaths generally the landslides begin as small debris slides that develop into large shallow debris avalanches or debris flows involving pyroclastic horizons and colluvial soils 0 5 2 m thick on steep and vegetated slopes often at the heads of gullies during motion the landslide materials eroded vegetation and soils from the slope so that the moving material volume tended to increase then proceeding towards and beyond the base of the slopes the phenomena evolved into hyperconcentrated streamflow due to dilution by incorporating water the results of motion analyses are described an empirical rheological relationship was used including two principal terms that depend on the total normal stress and on the flow velocity on this basis the model has simulated the velocity and duration of debris avalanches and the distribution of the deposits the selected areas were those of sarno quindici and cervinara where a large amount of data is available both on the material properties and geomorphological setting it was found that the majority of the cases at the two sites can be simulated successfully with only one specific pair of rheologic parameters this provides the possibility for first order predictions to be made of the motion of future landslides such predictions will be a valuable tool for outlining potential hazard areas and designing remedial measures

a comment on rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere by c n garzione et al earth planet sci lett 241 2006 543 556

low temperature thermochronology in the peruvian central andes implications for long term continental denudation timing of plateau uplift canyon incision and lithosphere dynamics abstract in peru the western edge of the 4 5 km high western cordillera is cut by a 3 km deep canyon to understand incision by the cotahuasi ocona river and the regional uplift history of this orogenic plateau capped by volcanic rocks 26 crystalline rock samples were collected for low temperature thermochronology from vertical profiles parallel and perpendicular to the canyon rock cooling histories confirm that most plateau denudation had occurred prior to 24 ma but plateau incision peaked after c 14 9 ma in response to rapid surface uplift the abrupt occurrence of a rock heating event is also detected during middle miocene time this was either a response to the emplacement of low conductivity regionally extensive ignimbritic caprock or a response to crustal scale fluid circulation caused by wet melting of the overriding plate when magmatism resumed c 24 ma the potential for thermochronology to provide information on past geothermal gradients is discussed showing how it can be used as a proxy for understanding change in subducting slab dynamics with oscillations in subduction angle having perhaps been the main on off switch for magmatism in this cordilleran setting supplementary material fission track and apatite u th he results and apatite chemistry indicators are available at http www geolsoc org uk sup18405

end member models for andean plateau uplift abstract diverse techniques have been applied over the past decade to quantify the uplift history of the central andean plateau ap in this study opposing models for surface uplift are evaluated including a rapid rise of 2 5 km 10 6 ma and a slow and steady rise since 40 ma these end member models are evaluated by synthesizing observations of the ap lithosphere and the history of deformation sedimentation exhumation magmatism uplift and fluvial incision structural and geophysical studies estimate variable shortening magnitudes 530 150 km involving cover to basement rocks an isostatically compensated thick crust 80 65 km high heat flow and zones of variable velocity and attenuation in the crust and mantle these observations have invoked interpretations such as a hot weak lithosphere partial melt crustal flow and perhaps current localized delamination but do not provide strong support for massive delamination required by the rapid uplift model deformation and associated exhumation began 60 40 ma and generally migrated eastward with consistent long term average shortening rates 12 8 mm yr in bolivia favoring the slow uplift model volcanic and helium isotope evidence show an ap wide zone of shallow mantle melting and thin lithosphere that has existed since 25 ma which is inconsistent with the rapid rise model that suggests lithospheric thinning occurred 10 6 ma paleoaltimetry data suggest a rapid 2 5 km elevation gain 10 to 6 ma but are equally consistent within error with a linear rise since 25 ma widespread fluvial incision 2 5 1 km occurred along the western flank since 11 8 ma and may be associated with surface uplift as proposed by the rapid rise model however the paleoaltimetry and incision data can also be explained by regional climate change associated with plateau uplift implications of these results for reconstructions of ap evolution are that 1 substantial deformation of a weak lithosphere is essential 2 ap growth has taken significantly longer 40 myr and was more uniform along strike 1500 km than previously appreciated and 3 the slow and steady uplift model is most consistent with available constraints we conclude that the rapid uplift model may be an overestimate and that a more protracted cenozoic uplift history is tenable

rainfall induced landslides by deficit field matric suction in unsaturated soil slopes landslides are mainly triggered by decrease in the matric suction with deepening the wetting band by rainfall infiltrations this paper reports rainfall induced landslides in partially saturated soil slopes through a field study a comprehensive analysis on umyeonsan mt landslides in 2011 was highlighted the incident involves the collapse of unsaturated soil slopes under extreme rainfall event fundamental studies on the mechanism and the cause of landslides were carried out a number of technical findings are of interest including the failure mechanism of a depth of soil and effect of groundwater flow the downward movement of wetting band and the increase of groundwater level based on this an integrated analysis methodology for a rainfall induced landslide is proposed in this paper that incorporates the field matric suction for obtaining hydraulic parameters of unsaturated soil the field matric suction is shown to govern the rate of change in the water infiltration for the landslide analysis with respect to an antecedent rainfall special attention was given to a one dimensional infiltration model to determine the wetting band depth in the absence of the field matric suction the results indicate that landslide activities were primarily dependent on rainfall infiltration soil properties slope geometries vegetation and groundwater table positions the proposed methodology has clearly demonstrated both shallow and deep seated landslides and shows good agreement with the results of landslide investigations

spatial and temporal occurrence of rainfall induced shallow landslides of flow type a case of sarno quindici italy article i nfo rainfall induced shallow landslides of flow type provide unstable masses which often travel long run out distances with high velocities thus posing a high societal risk when they affect large areas therefore analysis of their spatial and temporal occurrence is relevant to landslide hazard assessment as the first step of the risk analysis in order to address this issue this paper outlines a multidisciplinary procedure that is applied to the may 1998 sarno quindici landslides southern italy whose spatial and temporal occurrence is not satisfactorily addressed in current literature the spatial occurrence of the landslides is analysed using heuristic models for both the source and propagation areas the temporal occurrence of the landslides is firstly compiled and then related to the cumulated rainfall stratigraphy and hydraulic boundary conditions finally the spatial and temporal occurrence of the main landslide triggering mechanism is modelled over the whole affected area by analysing the groundwater regime and slope stability conditions the obtained results show that the spatial and temporal occurrence is strongly related to stratigraphy and hydraulic boundary conditions at both the slope and massif scales they also highlight a suitable procedure for assessing the spatial and temporal occurrence of complex landslides over large areas