a multi method monitoring of timing magnitude and origin of rockfall activity in the japanese alps abstract a multi method monitoring was conducted to detect the timing and trigger of rockfall activity on an alpine rockslide cliff composed of cretaceous sandstone and shale in the southern japanese alps aresawa rockslide 2900 m above sea level the monitoring programme includes manual measurements of flaking from painted rock surface and collection of fallen debris daily time lapse imaging of the rockwall automated recordings of rock temperature rock moisture and influencing meteorological factors air temperature and precipitation a stereographic pair of sequential photographs is used to visually identify the location of new erosion and semi quantitative evaluation of detached materials at daily resolution six years 2010 2016 of debris trapping show major rockfall activity in winter between november and may and occasional activity associated with heavy rains in summer and yield an average rate of rockwall retreat on the order of 1 mm a 1 the rockwall shows heterogeneous debris production mainly reflecting joint spacing time lapse imaging displays at least 10 15 rockfall events per year within the shot area 500 m2 the integration of multiple data suggests at least five types of triggering processes towards rockfalls which recur annually 1 in summer and early autumn heavy rainfalls raise the moisture content of the shallow bedrock often triggering significant rockfalls probably due to raised water pressure in rock joints or lubrication of joints 2 in late autumn and late spring light or intermediate rainfalls are sometimes followed by high moisture shallow freezing rapid thawing and eventually by different scales of rockfalls 3 in winter and early spring the same process as in the second case but rainfall is replaced by snowfall triggers submeter scale rockfalls 4 deep seasonal freezing to about 5 m enables release of meter scale rockfalls during seasonal thawing periods from late spring to early summer 5 short term large thermal fluctuations that produce cyclic thermal stress may also contribute to submeter scale rockfalls mainly in winter locally enhanced by freeze thaw action

stress field constraints on intraplate seismicity in eastern north america focal mechanisms of 32 north american midplate earthquakes mo 3 8 6 5 were evaluated to determine if slip is compatible with a broad scale regional stress field derived from plate driving forces and if so under what conditions stress regime pore pressure and frictional coefficient using independent information on in situ stress orientations from well bore breakout and hydraulic fracturing data and assuming that the regional principal stresses are in approximately horizontal and vertical planes 10o the constraint that the slip vector represents the direction of maximum resolved shear stress on the fault plane was used to calculate relative stress magnitudes defined by the parameterb s2 s3 s s3 from the fault stress geometry as long as the focal mechanism has a component of oblique slip i e the b axis does not coincide with the intermediate principal stress direction this calculation identifies which of the two nodal planes is a geometrically possible slip plane gephart 1985 slip in a majority of the earthquakes 25 of 32 was found to be geometrically compatible with reactivation of favorably oriented preexisting fault planes in response to the broad scale uniform regional stress field slip in five events was clearly inconsistent with the regional stress field and appears to require a localized stress anomaly to explain the seismicity significantly all five of these events occurred prior to 1970 when many regional networks were installed and their focal mechanisms are inconsistent with more recent solutions of nearby smaller events the frictional likelihood of the geometrically possible slip on the selected fault planes was evaluated in the context of conventional frictional faulting theory the ratio of shear to normal stress on the fault planes at hypocentral depth was calculated relative to an assumed regional stress field regional stress magnitudes were determined from 1 s s3 ratios based on the frictional strength of optimally oriented faults the basis for the linear brittle portion of lithospheric strength profiles 2 the computed relative stress magnitude b values and 3 a vertical principal stress assumed equal to the lithostat two end member possibilities were examined to explain the observed slip in these less than optimally oriented fault planes first the frictional coefficient was held constant on all faults hydrostatic pore pressure was assumed regionally and the fault zone pore pressure was determined since pore pressure is a measurable quantity with real limits in the crust p0 s3 this end member case was used to determine which of the geometrically possible slip planes were frictionally likely slip planes alternately pore pressure was fixed at hydrostatic everywhere and the required relative lowered frictional coefficient of the fault zone was computed slip in 23 of the 25 geometrically compatible earthquakes was determined to also be frictionally likely in response to an approximately horizontal and vertical regional stress field derived from plate driving forces whose magnitudes are constrained by the frictional strength of optimally oriented faults assuming hydrostatic pore pressure regionally the conditions for slip on these 23 relatively well oriented earthquake faults were determined relative to this regional crustal strength model and require only moderate increases in pore pressure between about 0 4 0 8 of lithostatic hydrostatic is about 0 37 of lithostatic or alternately moderate lowering 50 of the frictional coefficient on the faults which slipped superlithostatic pore pressures are not required focal mechanisms for the two other earthquakes with slip vectors geometrically consistent with the regional stress field however did require pore pressures far exceeding the least principal stress or extremely low coefficients of friction these events may reflect either local stress rotations undetected with current sampling or poorly constrained focal mechanisms the analysis also confirmed a roughly north to south contrast in stress regime between the central eastern united states and southeastern canada previously inferred from a contrast in focal mecha nisms between the two areas most central eastern united states earthquakes occur in response to a strike slip stress regime whereas the southeastern canadian events require a thrust faulting stress regime this contrast in stress regime with a constant maximum horizontal stress orientation determined by far field plate driving forces requires a systematic lateral variation in relative stress magnitudes superposition of stresses due to simple flexural models of glacial rebound stresses are of the correct sense to explain the observed lateral variation but maximum computed rebound related stress magnitude changes are quite small about 10 mpa and do not appear large enough to account for the stress regime change if commonly assumed stress magnitudes determined from frictional strength apply to the crust at seismogenic depths

large scale crustal heterogeneities and lithospheric strength in cratons abstract the rheology and thermal structure of the continental lithosphere are intimately linked in old cratons the effective elastic thickness of the lithosphere has been estimated by various spectral inverse methods based on the correlation between topography and gravity anomalies estimates vary within a very large range from 40 km to 120 km depending on the method used in this paper we use forward models to account for lateral variations in mechanical properties and their effect on the equivalent elastic thickness eet of the lithosphere from these models which allow brittle elastic ductile rheologies and mechanical discontinuities faults we have calculated the strain stress distributions and displacement fields vertical integration of the stress permits a local determination of the effective elastic thickness the computed displacements were used to calculate related bouguer and free air gravity anomalies and compare them with the observations the analysis is applied to the 2000 ma kapuskasing uplift in the superior province of the canadian shield where the presence of a high density block in the upper crust is due to the upthrusting of midcrustal rocks along a major thrust fault the study shows that the stability of this structure on geologic time scales requires a strong lower crustal rheology a cold geotherm and the fault to be healed this study also shows that because of stress dependence of the non linear rheology crustal heterogeneities may cause significant 40 local reductions of the lithospheric strength away from the kapuskasing structure the average strength of the lithosphere remains high eet 100 km conventional methods for estimating the elastic thickness would not resolve such local strength reductions in cratons but would predict depending on the method used highly overestimated or instead underestimated eet

interpreting rockfall activity on an outcrop talus slope system in the southern japanese alps using an integrated survey approach abstract understanding relationships between meteorological conditions and rockfall activity is important for the management of rockfall risks as well as for the estimation of future rockfall activity under climate change seasonal activity of rockfall on talus slopes depends on the actual triggers of rockfall which in turn may vary as well between outcrops because of different rockfall sources and the influence of topography in this study we interpret spatial and temporal variations in rockfall activity and related sediment transfer processes in an outcrop talus slope system in central japan through monitoring using rock temperature and moisture sensors sediment traps and time lapse cameras in addition tree ring analysis has been added to understand possible changes of rockfall activity over longer time periods results suggest that the frequency of grouped gravel transport i e soil creep was higher than that of individual transport i e rockfall and dry ravel on the talus slope whereas rockfall likely is the predominant process from the outcrops observations from sediment traps showed that coarse gravel is characterized by higher bounce heights and that it travelled longer distances than fine gravel rockfall from the outcrops was most active during dormancy of trees which locally lasts from autumn to early spring and can be related to freeze thaw cycles in contrast rockfall and other sediment transfer processes were monitored on the talus slope all year round secondary movement of gravels on the talus slope such as soil creep during rainfall events likely triggers rockfall during times when the outcrops are not producing rockfall i e from late spring to summer consequently our results suggest that the spatio temporal rockfall activity varies substantially between outcrops and talus slopes and that differences in process behavior should be taken into account in future disaster mitigation measures

postglacial vegetation and fire history eastern klamath mountains california usa pollen and high resolution charcoal data from bluff lake and crater lake california indicate simi lar changes in climate vegetation and fire history during the last 15 500 years pollen data at bluff lake suggest that the vegetation between c 15 500 and 13 100 cal bp consisted of subalpine parkland with scattered pinus and abies after 13 100 cal bp a relatively closed forest of p monticola p contorta and abies developed and fire event frequency was low the inferred climate then was cooler and wetter than present pinus and quercus vaccinifoliadominated at both sites during the early holocene when conditions were warm and dry as climate became wetter and cooler in the late holocene abies spp at both sites and tsuga mertensi ana at crater lake increased in importance displacing pinus and quercus the two lake records have similar trends in fire history with high event frequencies at c 8400 4000 and 1000 cal bp and low values at c 4800 cal bp the fire and vegetation history at both sites suggests a similar response to large scale changes in climate during the holocene

isotopic evidence of holocene climatic change in the san juan mountains colorado abstract the d of cellulose from 14c dated wood collected in the san juan mountains of southwestern colorado decreased by about 45 from 9600 to 3100 yr b p and an additional 25 to the present the wood samples are from trees that grew above present day tree line and reflect a time of warmer average summer temperatures these changes in d are interpreted to indicate a major change during the holocene in the sources of moisture in the seasonality of precipitation or in both

tectonics and topography for a lithosphere containing density heterogeneities the purpose of this paper is to clarify the dynamic role of lithospheric density heterogeneities in particular with respect to mountain building and other processes of intraplate deformation density anomalies within or just beneath the lithosphere constitute major sources for tectonic stress fields the product of their magnitude by their depth is shown to characterize their ability to induce deformation this rule of the density moment directly yields the lithospheric thickening or thinning rate when applied to structures of large lateral extent for anomalies of lateral extent that is small in comparison with their depth the deformation is vertically inhomogeneous and has been computed with the help of simple physical models of a stratified viscous newtonian lithosphere the analytical treatment is based on fourier transform continent continent collision thickens not only the crust but the entire lithosphere the cold root underlying a mountain chain induces strong regional compressive stresses able to sustain the mountain bulding process without further help from forces transmitted from far away thus the continental lithosphere is in a somewhat metastable mechanical state adiabatic i e rapid thickening or thinning tends to grow further once initiated tectonic phases of strong compression correspond to the climax of such instabilities the response of models with cold lithospheric roots of various intensities has been computed both in two and three dimensions they yield velocity distributions and stress fields instructive comparisons are made with earthquake focal mechanisms and in situ stress measurements in the alpine and appalachian regions in the presence of lateral variations of the mechanical properties of the lithosphere the tectonic style is not only function of the local topography and of the nature of its compensation deformations in neighbouring provinces are coupled as shown by 3 dimensional models for example thickening sustained by a cold lithospheric root may generate extension in peripheral zones of weakness these last results illustrate the point that the computation of regional tectonic stresses requires the knowledge of the density anomalies within the lithosphere on the one hand and of geometrical constraints related to lateral mechanical heterogeneities on the other

lower timberline in central colorado during the past 15 000 yr a 15 000 yr paleoenvironmental record at the elevation of lower timberline in central colorado suggests two major paleoclimatic changes during that interval 1 at 10 000 yr b p from cool moist conditions to warm moist conditions and 2 at 4 000 yr b p to warm dry conditions this sequence can be interpreted as a shift from precipitation predominantly originating from pacific winter storms before 10 000 yr b p to a predominantly monsoonal type regime lasting until 4 000 yr b p to the present pattern contemporaneity of higher upper timberline and lower lower timberline during the 10 000 to 4 000 yr b p interval is not contradictory but a result of changes in those circulation patterns

a 16 000 14c yr b p packrat midden series from the usa mexico borderlands abstract a new packrat midden chronology from playas valley southwestern new mexico is the first installment of an ongoing effort to reconstruct paleovegetation and paleoclimate in the u s a mexico borderlands playas valley and neighboring basins supported pluvial lakes during full and or late glacial times plant macrofossil and pollen assemblages from nine middens in the playas valley allow comparisons of two time intervals 16 000 10 000 and 4000 0 14c yr b p vegetation along pluvial lake margins consisted of open pinyon juniper communities dominated by pinus edulis juniperus scopulorum juniperus cf coahuilensis and a rich understory of c4 annuals and grasses this summer flowering understory is also characteristic of modern desert grassland in the borderlands and indicates at least moderate summer precipitation p edulis and j scopulorum disappeared or were rare in the midden record by 10 670 14c yr b p the late holocene is marked by the arrival of chihuahuan desert scrub elements and few departures as the vegetation gradually became modern in character larrea tridentata appears as late as 2190 14c yr b p based on macrofossils but may have been present as early as 4095 14c yr b p based on pollen fouquieria splendens one of the dominant desert species present at the site today makes its first appearance only in the last millennium the midden pollen assemblages are difficult to interpret they lack modern analogs in surface pollen assemblages from stock tanks at different elevations in the borderlands

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

ground motion and stress accumulation driven by density anomalies in a viscoelastic lithosphere some results for the apennines summary we provide the analytical formulation for calculating the displacement and stress field forced by internal sources in a stratified self gravitating viscoelastic earth this model is specialized to study the rate of vertical motion and shear stress accumulation produced by lithospheric density anomalies these sources are allowed to vary in the lateral direction we show that sphericity plays a crucial role for elongated lithospheric anomalies while self gravitation produces minor deviations from a gravitating earth when the model is applied to the apennines we get for lithospheric viscosity ranging between 10 and loz3 pas the subsidence of the plate underlying the active front of the overthrusting load to be around 0 5 1 0 mm yr this is consistent with the amount of sedimentation in the adriatic foredeep the deformation pattern is very peculiar with the largest subsidence localized beneath the active front of the topography our model enlightens the impact of discontinuities of tectonic phases on vertical motions in collision zones if lithospheric viscosity is around 10 pa s vertical motions decay drastically on time scales of 105yr if lateral migration of density anomalies comes to an end for higher viscosities deformation rates are maintained longer this correlation between horizontal and vertical motions suggests that altimetric geodetic surveying along levelling lines of a few hundred kilometers can be an important tool to constrain the tectonics of the studied region results are also shown for vertical motions along a transect perpendicular to the apennines when the crustal structure inverted from bouguer gravity data is considered analysis of the stress field induced by an overthrusting load shows that principal stress differences of a few bar or a few tenths of mpa can be accumulated on time scales of 102 103yr these low values agree with the average stress drop of earthquakes in the appalachians and northern apennines where our modelling can be applied we find that lateral density variations certainly contribute to intraplate stresses but they are less efficient in triggering earthquakes than other mechanisms such as transcurrent motions along active plate margins seismicity induced by lateral variations of crustal and lithospheric density must be moderate characterized by long return times these results are in agreement with the recorded seismicity in the northern apennines where the largest earthquakes have return times of lo2 yr if shear stress is forced by an overthrusting load we find that the largest rate of stress accumulation in the crust is concentrated beneath the active front close to the boundary with the ductile lithosphere discontinuities of tectonic phases play an important role in controlling the amount of shear stress due to density anomalies

seismotectonics of the southern appalachians abstract the southern appalachians of eastern tennessee and western north carolina is a region for which high quality instrumental seismic data have been very limited in this paper we report more than 100 new or relocated hypocenters obtained from the initial 2 1 2 yr of operation of the southern appalachian regional seismic network sarsn a 16 station four state telemetered network of short period vertical instruments these data provide a first order snapshot of southern appalachian seismicity that confirms some previous observations and adds new results for the region the most important new observations are well constrained focal depths and focal mechanisms for southern appalachian earthquakes the level of activity exceeds expectations and concentrates more heavily in the valley and ridge province of eastern tennessee as opposed to the blue ridge or inner piedmont than is evident in historical listings the large majority of these events lie between the new york alabama lineament and the clingman ocoee lineaments magnetic anomalies produced by deep seated basement structures an analysis of the uniqueness and stability of hypocentral depth yields reliable depths for 58 earthquakes and demonstrates that most southern appalachian seismic activity occurs beneath the decollement thus lending quantitative support to the argument that appalachian seismicity is unrelated to surficial geological or tectonic features several new focal mechanisms of a higher quality than previously available indicate that the basement of the valley and ridge is under ne sw compression and the principal mode of faulting is right lateral strike slip on nearly north south faults in both depth and type of faulting the seismogenic model we propose for the southern appalachians closely emulates the giles county zone to the north of our study area

the mechanism of rockfall disaster a case study from badouzih keelung in northern taiwan abstract on august 31st 2013 high intensity rainfall caused a severe rockfall disaster in badouzih keelung this study combines the results of detailed field investigation and process based as well as empirical based method to point out unsafe road sections the mechanisms and the characteristics of motions of rockfall are analyzed in the field two intersecting joints and the bedding plane divided bedrock into blocks weathering and the infiltration of rainfall accelerated the erosion process and precipitated ruptures when the rainfall reached its highest intensity which is 94 5 mm h in this event a great deal of water on the slope surface eroded the matrix causing instability and leading to the failure of the rock blocks the process of rockfall took 23 s and can be divisible into 4 stages including roll fall bounce and roll process based simulations are adopted in this case and several critical road sections to understand the characteristic of movements with the empirical based energy line angle analysis potential road sections which may affect by rockfall are showed and their energy are also estimated for the purpose of mitigating rockfall impact reducing similar disasters in this area

spatial variability of late quaternary paleoclimates in the western united states abstract paleoclimatic interpretation of proxy data is complicated sometimes by the appearance of heterogeneous patterns of climatic responses across networks of sites modern climate analogues for the western united states similar to those patterns of atmospheric circulation of 18 000 and 9000 yr b p were examined in order to explain such patterns of spatial heterogeneity modern analogues were defined by comparing modern atmospheric circulation patterns with those simulated by general circulation models maps of temperature and precipitation anomalies of the modern analogues reveal patterns of spatial heterogeneity which resemble the patterns of effective moisture compiled from paleoclimatic data january 1957 was found to be a reasonable 18 000 yr b p analogue and it features isolated areas of increased wetness in the northern great basin and increased dryness in the northwest interior analogues for 9000 yr b p from a composite of 11 augusts display patterns of spatial heterogeneity of effective moisture over most of the mountainous areas the analogues suggest that spatial heterogeneity of climate is the rule rather than the exception over much of the western united states with the climatic anomalies at any particular time representing the outcome of the mediation of large scale atmospheric circulation controls by smaller scale topographic features

numerical modeling of self channeling granular flows and of their levee channel deposits when not laterally confined in valleys pyroclastic flows create their own channel along the slope by selecting a given flowing width furthermore the lobe shaped deposits display a very specific morphology with high parallel lateral levees a numerical model based on saint venant equations and the empirical variable friction coefficient proposed by pouliquen and forterre 2002 is used to simulate unconfined granular flow over an inclined plane with a constant supply numerical simulations successfully reproduce the self channeling of the granular lobe and the levee channel morphology in the deposits without having to take into account mixture concepts or polydispersity numerical simulations suggest that the quasi static shoulders bordering the flow are created behind the front of the granular material by the rotation of the velocity field due to the balance between gravity the two dimensional pressure gradient and friction for a simplified hydrostatic model competition between the decreasing friction coefficient and increasing surface gradient as the thickness decreases seems to play a key role in the dynamics of unconfined flows the description of the other disregarded components of the stress tensor would be expected to change the balance of forces the front s shape appears to be constant during propagation the width of the flowing channel and the velocity of the material within it are almost steady and uniform numerical results suggest that measurement of the width and thickness of the central channel morphology in deposits in the field provides an estimate of the velocity and thickness during emplacement citation mangeney a f bouchut n thomas j p vilotte and m o bristeau 2007 numerical modeling of self channeling granular flows and of their levee channel deposits

the effects of rockfall volume on runout distance the main goal of this paper is to clarify the effects of rockfall volume on its fluidization for this purpose outdoor rockfall experiments were carried out to analyze runout distances and individual movements of rockfall blocks and numerical simulations were conducted for these experiments to learn more about the mechanism of rockfall fluidization the rockfall experiments were conducted using an artificial slope on which granite slabs were surfaced and overlaid with cubiformed granite blocks the size and number of blocks were varied in this series of experiments further numerical simulations were carried out in which the coordinates of individual rockfall blocks were traced in three dimensional space from rockfall initiation to final deposition it became clear from the experiments and simulations that the runout distance had a positive correlation with the rockfall volume number of rockfall blocks and the runout distance of the gravity center of deposited rockfall mass had a negative correlation with the rockfall volume to clarify the mechanism of these two phenomena the positions of individual blocks from initial arrangements to final depositions were traced in the experimental and numerical simulations this revealed that the relative positions of each block along the slope direction were not changed during rockfall movement the reason for the block sequence preservation was that front facing blocks in the initial cube arrangement accelerated and rear facing blocks decelerated along the slope by internal collision between blocks further as the rockfall volume increased the opportunities for impact among the rockfall blocks increased with the front facing blocks pushed farther whereas the gravity center of the deposited rockfall mass had an inclination to travel shorter distances as rockfall blocks increased according to the increase of kinetic energy dispersed by the collision of blocks

stress fields and tectonic motions induced by time varying density anomalies in the lithosphere abstract we explore the extent to which a viscoelastic rheology of the lithosphere could affect the deviatoric stress and vertical deformation driven by deep seated time dependent density anomalies within the lithosphere these sources can be associated with fast density instabilities of thermal chemical or tectonic origin in particular we focus on the stress transfer from the ductile lower lithosphere to the elastic crust the model is radially stratified and employs the maxwell rheology stress transfer takes place from a wide region within the lower lithosphere to the thinner elastic top layer where it is amplified the time history of the source and the lithospheric viscosity play a crucial role in determining the time evolution of the stress and deformation patterns attention is drawn to the temporal rates of maximum shear accumulation which are interpreted as earthquake recurrence times for realistic values of the model and source parameters the increase of the deviatoric stress within the crust can be of a few bars on time scales of 10 3 years for lithospheric viscosities of around 10 22 to 10 23 pa s 1 lower levels of stress variations are found in the viscoelastic lithosphere these findings are consistent with the low levels of stress release and long recurrence times that characterize the intraplate seismicity commonly attributed to density instabilities as a specific application we considered the tectonic subsidence of the tyrrhenian basin from the rate of subsidence derived from the odp leg 107 drilling campaign we can estimate an upper bound for the lithospheric viscosity of around 5 10 22 pa s 1 which is appropriate for active tectonic regions

15 k y paleoclimatic and glacial record from northern new mexico the southern sangre de cristo mountains new mexico contain evidence of glacial activity from the late pleistocene to late holocene sediment cores recovered from an alpine bog 3100 m trapped behind a pinedale age moraine 2 km downvalley from a high elevation cirque reached glacial age debris and recovered 6 m of lake clays overlain by gyttja accelerator mass spectrometry dating sedimentology variations in magnetic properties and organic carbon data reveal six distinct periods of glacial and or periglacial activity these include a late pleistocene pinedale glacial termination just before 12120 1 4 c yr b p a younger dryas chron cirque glaciation an early neoglacial periglacial event ca 4900 1 4 c yr b p a late holocene cirque glaciation 3700 1 4 c yr b p as well as late holocene periglacial events at 2800 1 4 c yr b p and the little ice age ca 120 1 4 c yr b p cold events in the middle to late holocene correlate with subtle ice rafting events in the north atlantic and records of cold events in north america and europe and were probably hemispheric in extent

mechanisms of crustal deformation thirty sixthwilliam smith lecture the energy source for crustal deformation is isotopic heating and secular cooling of the mantle in a true solid heat would be lost to the surface by conduction however solid state creep processes allow the earth s solid mantle to exhibit a fluid behaviour thus thermal convection can convert heating into directed motion variations in temperature lead to variations in densitythrough thermal expansion and contraction although the resultant body forces are vertical horizontal variations in temperature lead to horizontal body forces at an ocean ridge the variations in the thickness of the lithosphere lead to the elevation of the ridge the result is a substantial horizontal ridge push force this force along with the trench pull force on the descending lithosphere is the primary force driving plate tectonics lithospheric thinning must occur beneath continental rifts and plateau uplifts i suggest that lithospheric thinning is caused by the diapiric penetration of hot asthenospheric rock to the crust mantle boundary this penetration may also cause lithospheric stoping and plateau uplifts lithospheric thinning leads to large tensional stresses above the zone of thinning these forces are generally much larger than the compressional forces generated by crustal thinning the forces generated by lithospheric thinning are quite large and may be responsible for the propagation of continental rifts in island arcs and andean type orogenic belts both lithospheric thinning and crustal thickening result in large tensional forces probably the most complex zone of crustal deformation is the continental collision variations in types of continental collisions are discussed

maximum horizontal stress orientations in the cooper basin australia implications for plate scale tectonics and local stress sources summary borehole breakouts and drilling induced tensile fractures ditfs were interpreted in 61 wells in the cooper basin indicating an average maximum horizontal stress orientation of 101 n a total of 890 borehole breakouts and 608 ditfs were interpreted in the cooper basin the approximately east west maximum horizontal stress orientation is consistent over much of the basin except in the patchawarra trough where maximum horizontal stress rotates to a northwest southeast orientation this rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the cooper basin the stress field in the cooper basin appears to mark the apex of a major horseshoe shaped rotation in maximum horizontal stress direction across central eastern australia finite element modelling of the in situ stress field of the indo australian plate iap using a range of plate scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of australia reasonably well including the mean east west maximum horizontal stress orientation in the cooper basin however plate boundary scale modelling does not adequately match the horseshoe shaped stress rotation across central eastern australia the average east west maximum horizontal stress orientation in the cooper basin indicates that stresses from tensional forces acting along the tonga kermadec subduction zone are not transmitted into the interior of the australian plate the majority of the tensional forces associated with the tonga kermadec subduction zone are most likely accommodated along the numerous spreading centres within the lau havre backarc basin a number of more localized stress anomalies have also been identified these cannot be explained by plate scale tectonic forces and are possibly a result of geological structure and or density contrasts locally perturbing the stress field

age of the crowfoot advance in the canadian rocky mountains a glacial event coeval with the younger dryas oscillation a suite of sediment core samples was recovered from two lakes crowfoot and bow lakes that are adjacent to the crowfoot moraine type locality to identify and radiocarbon date sediments related to the crowfoot advance the crowfoot moraine system widely recognized throughout northwestern north america represents a glacial advance that is post wisconsin and pre mazama tephra in age an interval of inorganic sediments bracketed by accelerator mass spectrometry radiocarbon ages of ca 11 330 and 10 100 sup 14 c yr b p is associated with the crowfoot moraine the crowfoot advance is therefore approximately synchronous with the european younger dryas cold event ca 11 000 10 000 sup 14 c yr b p furthermore the termination of the crowfoot advance also appears to have been abrupt these findings illustrate that the climatic change responsible for the european younger dryas event extended beyond the northern atlantic basin and western europe equilibrium line altitude ela depressions associated with the crowfoot advance are similar to those determined for the little ice age advance whereas younger dryas ela depressions in europe significantly exceed little ice age ela depressions 26 refs 3 figs 1 tab

using palaeoenvironmental dna to reconstruct past environments progress and prospects palaeoenvironmental dna palendna is defined as ancient dna adna originating from disseminated genetic material within palaeoenvironmental samples sources of palendna include marine and lake sediments peat loess till ice permafrost palaeosols coprolites preserved gut contents dental calculus tephras and soils as well as deposits in caves rockshelters and at archaeological sites palendna analysis provides a relatively new tool for quaternary and archaeological sciences and its applications have included palaeoenvironmental and palaeodietary reconstructions testing hypotheses regarding megafaunal extinctions human environment interactions taxonomic studies and studies of dna damage because palendna samples comprise markedly different materials and represent wide ranging depositional and taphonomic contexts various issues must be addressed to achieve robust reproducible findings such issues include climatic and temporal limitations the biological origin and state free versus bound of palendna stratigraphic reliability sterile sampling ability to distinguish modern from adna signals dna damage and pcr amplification dna extraction methods and taxonomic resolution in this review we provide a non specialist introduction to the use of palendna for quaternary and archaeological researchers assess attributes and limitations of this palaeoenvir onmental tool and discuss future prospects of using palendna to reconstruct past environments copyright 2014 the authors journal of quaternary science published by john wiley sons ltd on behalf of quaternary research association

extension in south central british columbia mechanical and thermal controls abstract geological data indicate that the omineca belt in the canadian cordillera experienced a rapid episode of extension between 58 and 48 ma following a compressional event and crustal thickening in the early tertiary restored crustal sections have been constructed using listric fault geometries to infer that the amount of eocene extension affecting the southern omineca belt exceeded 50 at the end of compression in the early tertiary the omineca and intermontane belts of southern british columbia reached a crustal thickness of 60 km isostatic compensation implies that these belts formed elevated ranges this is consistent with sediment deposition west of these ranges and the absence of in situ sedimentary basins the stress induced by topography and crustal thickening is calculated the calculations show that the stress in homogeneously thickened lithosphere is small and that tensile stress in the crust is compensated by compression in the mantle removal of the mantle lithosphere induces a stress field that is tensile throughout the lithosphere this local stress field combined with stress induced at the plate boundary by the oblique impingement of the kula farallon ridge controlled the position and direction of crustal extension in south central british columbia the present high heat flow on the west flank of the omineca belt 80 mw m 2 is interpreted as the relict of eocene extension following removal of the lithospheric mantle

temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region japan the duration of the soil depth recovery needed for reoccurrence of shallow colluvial landslides at a given site in humid regions is much longer than the return period of rainfall needed to generate sufficient pore water pressure to initiate a landslide knowledge of the rate of change in soil depth in landslide scars is therefore necessary to evaluate return intervals of landslides spatial variation in sediment transport at the kumanodaira landslide scar in central japan was investigated by field observations spatial distribution of the rate of change in soil depth was estimated using sediment transport data and geographic information system gis analysis observations revealed that the timing of sediment transport differed for shallow and deep soil layers near surface sediment transport mostly dry ravel and some shallow soil creep at depths 0 05 m measured in sediment traps was active in winter and early spring and was affected by freezing thawing soil creep of subsoil i e 0 05 m monitored by strain probes was active in summer and autumn when precipitation was abundant near surface sediment flux was estimated by a power law function of slope gradient deeper soil creep was more affected by relative location to the landslide scar which influences soil depth than by slope gradient our study indicated that the rate of soil depth recovery is high just below the head scarp of the landslide abrupt changes in the longitudinal slope topography immediately above within and just below the head scarp became smoother with time due to degradation proximate to the landslide head scarp and flanks as well as aggradation just below the head scarp copyright 2014 john wiley sons ltd

intraplate stresses and seismicity the role of topography and density heterogeneities abstract the stress induced by the topography and by density heterogeneities in the lithosphere has been computed for two different tectonic regions of the north american plate the lithosphere was assumed to consist of a two dimensional layered elastic slab over an inviscid fluid the calculations show that these stresses are locally comparable in magnitude to the regional tectonic stress 20 50 mpa two areas have been analyzed in greater detail the southeastern united states and the rio grande rift the stress in the southeastern united states is computed along a cross section perpendicular to the strike of the appalachian mountains the computed stress appears largest beneath the blue ridge and valley and ridge provinces where the appalachian seismicity is located the stress in the western united states is computed along a cross section perpendicular to the rio grande rift large stress is shown beneath the rift and the adjacent regions the stress induced by surface and internal loading is extensional in the rio grande rift and compressional in the colorado plateau and in the great plains

three dimensional modeling of intraplate stresses in the epicentral zone of the 21 may 1997 jabalpur earthquake of mw 5 8 central india abstract three dimensional intraplate stresses induced by topography and crustal density heterogeneities have been modeled for a region in central india latitude 21 26 n longitude 77 82 e that was affected by the 1927 son valley m w 6 4 and the 1997 jabalpur m w 5 8 earthquakes the modeled stresses show that these two events occurred in the zones of significant increase in gradients of the principal stress difference 1 3 contours the highest value of these differential stresses 90 mpa is obtained at 5 km depth beneath the epicentral zone of 1927 son valley earthquake whereas a value of 35 mpa is obtained at the focal depth 35 km of the 1997 jabalpur mainshock further depth sections of estimated differential stresses delineate a south dipping high stress body penetrating the whole crust probably a mafic intrusive intruded during the deccan volcanism episode beneath a zone bounded by narmada north fault in the north and narmada south fault in the south within which all aftershocks including mainshocks of the 1997 jabalpur and the 1927 son valley have occurred the modeled direction of principal stresses as well as inferred mode of faulting at 5 20 35 and 40 km depths correlates strongly with the long period 20 50 s centroid moment tensor solutions for the broadband recordings of the m w 5 8 jabalpur mainshock results suggest that estimated large intraplate stresses associated with an inferred mafic intrusive in the presence of high pore pressure resulted from the dehydration of the serpentinite minerals and deep brittle ductile transition may contribute to the failure of rock along the pre existing weak narmada south fault leading to the earthquakes in the deep crust it is proposed that the causal association of large intraplate stresses and the pre existing deep crustal faults would control the future locales of earthquakes in the narmada son lineament

thermal regime and post orogenic extension in collision belts in order to assess the conditions leading to post orogenic extension the temperature and strength of the lithosphere during continental collision are calculated the calculations assume that heat is transported by conduction and either that the lithosphere is homogeneously thickened or that only the crust is thickened during the collision despite increased crustal thickness and heat production the temperature does not increase if the rate of shortening is moderate 5 10 16s 1 leading to 100 increase in crustal thickness in 40 myears the temperature distribution is used to determine a rheological profile that is compared with the stress induced by compensated topography the calculations show that for homogeneous lithospheric thickening the strength of the lithosphere increases and is higher than the tensile stress except in the shallow crust the total strength of stable continental lithosphere at the end of shortening is on the order of 1013 n m 1 it is larger by one order than the force induced by compensated topography 1012 n m 1 it appears that homogeneous lithospheric thickening would not lead to post orogenic extension unless the initial conditions are very special with the lithosphere hotter than normal for crustal thickening only the strength of the lithosphere decreases slightly and is on the same order as the tensile stress extension does not necessarily follow from thickening of the crust only but it could take place for a relatively wide range of initial conditions with initial surface heat flow 60 mw m 2 or higher alternatively an event such as rapid removal of the mantle lithosphere by delamination or small scale convection would increase the tensile stress heat rapidly the lithosphere reduce its strength and always trigger extension

impact of historical land use changes on lacustrine sedimentation recorded in varved sediments of lake jaczno northeastern poland abstract varved lake sediments provide an invaluable archive of natural and human induced environmental changes we present results of sedimentological geochemical and pollen analyses of recent sediments from lake jaczno northeastern poland the sediment record was dated using varve chronology validated with 137 cs fallout peaks principal component analysis pca and stratigraphically constrained cluster analysis were used to identify four major phases of lake development during the last 200 years these results were compared with maps and archival data at the beginning of the studied period 1839 1853 the lake catchment was already partly deforested and used for agriculture which resulted in intensive soil erosion and high input of minerogenic matter next a short period 1854 1864 characterized by fire events is recorded by microcharcoal in the sediments the following phase 1865 1971 shows major changes in the catchment area including further deforestation and shortening of the major inflow feeding the lake this caused a major change from allochthonous minerogenic to autochthonous biogenic sedimentation expressed by the transition from clastic organic to biogenic varves the most recent phase 1972 2013 is characterized by natural afforestation reduction of allochthonous inputs and increase in autochthonous deposition our study shows how intensification of agriculture and related land use changes in small catchments influences sedimentation processes and the formation of varves

combining field and modelling techniques to assess rockfall dynamics on a protection forest hillslope in the european alps adequate management of a mountain forest that protects downslope areas against impacts of rockfall requires insight into the dynamics of the hillslope environment therefore we applied a combined approach using field and modelling techniques to assess the determining factors for rockfall source areas rockfall tracks and rockfall runout zones on a forested slope in mountainous terrain the first objective of this study was to understand why rockfall occurs in the study area the second objective was to translate the knowledge obtained in the field into a model that simulates rockfall dynamics on a forested slope realistically the third objective was to assess which hillslope characteristics primarily determine the distribution of active rockfall tracks to achieve these objectives we made a geomorphological map of the whole study area and we measured the major discontinuity planes in the bedrock that are exposed in the rockfall source areas furthermore a test site for simulation modelling within the larger study area was defined in which both a forest and a hillslope inventory were carried out the available data and our developed rockfall simulation model allowed us to assess the slope characteristics that mainly determine the distribution of areas affected by rockfall we found that in decreasing order of importance both standing and felled trees the surface roughness and rockfall resistant shrubs primarily determine the distribution of rockfall affected areas simulation tests without a forest cover produced similar rockfall runout zones as fossil rockfall events identified in the field we believe that the combined field and modelling approach is a prerequisite for understanding how forests can protect against rockfall

runout analysis of a large rockfall in the dolomites italian alps using lidar derived particle sizes and shapes lidar data were used to quantify and analyse a rockfall event which occurred in 2003 in the western dolomites italian alps in addition to previously existing airborne laserscanning als data high resolution terrestrial laserscanning tls data were collected by using the original point clouds the volume axial ratio and runout length of single boulders as well as the surface roughness in the runout zone of the rockfall were derived the total volume of the rockfall event of approximately 10 000 m was estimated by a reconstruction of the pre event surface at the detachment zone the analysis of the laser scanning data of the accumulation zone revealed a power law scaling for boulder volumes larger than 8 m the dependence of runout length on boulder volume is complex it is moderated by particle sphericity in addition we used als and tls data to derive the spatial distribution of surface roughness on the talus cone tls allow for more accurate roughness mapping than als data but for most applications the point density of als data seems to be sufficiently high to derive measures of roughness different sampling approaches for plane fitting on the scale of 5 m did not show significant effects besides the computational time the results of our analyses provide important perspectives for rockfall modelling and process understanding with potential applications in both applied natural hazards and pure geomorphological research copyright 2012 john wiley sons ltd

rockfall activity index rai a lidar derived morphology based method for hazard assessment abstract in this paper we introduce the rockfall activity index rai a point cloud derived high resolution morphology based approach for assessing rockfall hazards with the rai methodology rockfall hazards are evaluated in a two step procedure first morphological indices local slope and roughness are used to classify mass wasting processes acting on a rock slope these classifications are then used with estimated instability rates to map rockfall activity across an entire slope face the rockfall hazard is quantified as the estimated annual kinetic energy produced by rockfall along 1 m length segments of a slope face field assessment of the rai method at multiple study sites indicates that the morphology derived classification and hazard assessment routines provide results that closely match the observed behavior and performance of rock slopes

holocene fire and vegetation along environmental gradients in the northern rocky mountains abstract holocene records of fire vegetation and climate were reconstructed from four sites in the bitterroot range region of the northern rocky mountains in order to examine the vegetation and fire histories and evaluate the hypothesis proposed by whitlock and bartlein 1993 regarding the effects of increased summer insolation on precipitation patterns vegetation history in the series of sites was broadly similar in the late glacial period the pollen data suggest open parkland dominated by picea or alpine meadow which reflect conditions cooler and drier than present these open forests were replaced in the early to middle holocene by forests composed mainly of pinus and pseudotsuga which suggest conditions warmer than present modern forest compositions were in place by ca 3000 cal yr bp and small variations in the timing of the vegetation shifts reflect local differences among sites the long term trends in fire occurrence support the hypothesis proposed by whitlock and bartlein 1993 that precipitation regimes were sharpened during the early holocene summer insolation maximum but their location has remained unchanged as a result of topographic constraints sites located in areas currently summer dry were drier than present during the early holocene and fires were more frequent conversely sites located in the areas that are summer wet at present were wetter than present in the early holocene and fires were less frequent on millennial time scales it appears that the climate boundary is controlled by topography and does not shift

late holocene relationships among fire climate and vegetation in a forest sagebrush ecotone of southwestern idaho usa the forest sagebrush ecotone is characterized by a more arid climate than forested regions therefore establishing fire histories using traditional methods e g fire scars from trees charcoal in lake sediments is problematic this study uses radiocarbon dating of charcoal preserved in alluvial deposits to reconstruct a record of fire and geomorphic response in southwestern idaho samples indicate three primary periods of fire related activity 4400 4000 2000 1400 and 650 400 cal yr bp charcoal macrofossil identification and comparison with other regional records indicate this area has likely alternated between a fuel limited system fires limited by lack of fuels and a moisture limited system fires limited by too much moisture with changes in holocene climate over the past 2000 yr samples from this site indicate most fires occurred during wetter times than the record average during overall wetter periods e g little ice age lia 600 100 cal yr bp tree density may have increased

quantification of controls on regional rockfall activity and talus deposition kananaskis canadian rockies abstract rockfall is a significant geomorphic process in many mountainous regions that also poses a notable natural hazard risk most previous studies of rockfall erosion have investigated the mechanics and rates of local rockwall retreat and talus deposition with only a few investigations of rockfall and or associated talus considering larger spatial scales i e drainage basin mountain range the purpose of the current research is to investigate the areal extent of rockfall talus and controlling factors of its distribution over regional spatial scales of order 102 km2 in kananaskis canadian rockies to inform our understanding of its significance in mountain development to achieve this goal a large talus inventory is collected and analyzed for 11 steep tributaries of the kananaskis river canadian rockies talus accumulations associated with rockfall provide evidence about the nature and rates of rockfall activity that supplies sediment to these deposits and are the focus of the present study to quantify the controls of rockfall talus activity in this region we analyze the association of talus deposits with structural geology glacial topography and temperature related weathering i e frost cracking a total of 324 talus polygons covering a surface area of 28 51 km2 are delineated within the 11 study basins with the number of talus polygons in each study basin ranging from 1 to 73 analysis of the talus inventory shows that cirques and glacially sculpted valleys are locations of notable talus accumulation in kananaskis with other locations of significant talus deposition being associated with thrust faults we also found that the upper elevations at which talus deposits are typically found are the general range of elevations experiencing a notable number of days in the frost cracking window when this window is defined as 3 to 15 c no such association is found for the frost cracking window of 3 to 8 c estimates of average erosion rates for all study basins combined are between 0 15 mm y 1 lower estimate to 3 1 mm y 1 upper estimate rockfall activity is expected to have been most active for the several millennia following deglaciation during the paraglacial period when hillslopes were oversteepened

seismicity and seismotectonics of madagascar revealed by the 2011 2013 deployment of the island wide macomo broadband seismic array abstract the seismicity and seismotectonics of madagascar have been studied using an island wide distribution of broadband seismic stations the 28 station madagascar comoros mozambique macomo array was deployed for a 23 month period between 2011 and 2013 macomo data were supplemented by seven temporary stations from the seismological signatures in the lithosphere asthenosphere system of southern madagascar selasoma project ten temporary stations from the reunion hotspot and upper mantle reunions unterer mantel project rhum rum and 11 permanent stations a total of 695 earthquakes with magnitudes between ml1 and ml5 3 located within madagascar were recorded a new local magnitude scale was developed and focal mechanisms were determined for 23 well recorded events most of the seismicity is clustered within central madagascar forming nw se trends in the ankaratra region and ne sw trends in the alaotra and ankay regions that roughly align with extensional tectonic features the northern and southern parts of madagascar also show seismicity clusters that align parallel to existing tectonic features primarily precambrian shear zones focal mechanisms exhibit a wide orientation of nodal planes show predominantly normal faulting throughout madagascar and provide no evidence for a sharp east west striking plate boundary between the lwandle and somalian plates in the middle of the island however a diffuse plate boundary cannot be excluded we suggest that topographically generated extensional stresses is the cause of most seismicity given that significantly fewer earthquakes are located in the lower elevation areas of the island compared to regions of higher elevations the frequency magnitude distribution has a b value of 1 2 and indicates that events with magnitude ml5 or greater should occur with an average repeat time of 1 4 years however no earthquake exceeding ml6 has been recorded in the last century suggesting that the frequency magnitude distribution could be truncated

intraplate seismicity and stress in the southeastern united states abstract the stress induced by topography and by density heterogeneities in the lithosphere has been computed for two seismic regions in the southeastern united states the southern appalachian mountains and the south carolina coastal plain the lithosphere was assumed to be a three dimensional layered elastic slab overlying an inviscid fluid the calculations indicate that the local stress is of the same magnitude as the tectonic stress tens of mpa but contradictory conclusions are suggested by the comparison of stress differences and principal directions with earthquake locations and focal mechanisms in the southern appalachians the seismicity correlates well with the stress maximum and focal mechanisms agree with the calculations where regional stress is combined with locally induced stress in south carolina a combination of regional and local stress can explain the orientation of focal mechanisms but stress does not concentrate in the region of charleston and thus other factors must play a role in the charleston seismicity

ground temperature regimes and geomorphological implications in a mediterranean mountain serra da estrela portugal air and shallow ground temperatures from two monitoring sites at the serra da estrela portugal are analysed the cantaro gordo site is located at 1875 m asl and the fraga das penas at 1640 m asl the climate of the study area is mediterranean and very irregular both on a yearly and monthly basis this is particularly significant during winter when differences in snow cover have direct influence on the ground thermal regimes and therefore on geocryological processes to assess the significance of the ground thermal regimes for the geomorphological dynamics bi hourly records of temperature are studied at a daily basis eight types of daily regime were identified isothermal unfrozen non isothermal unfrozen surficial freeze thaw surficial freeze thaw and subsurficial frost surficial and subsurficial freeze thaw subsurficial frost surficial and subsurficial frost and surficial frost but no daily rhythm the occurrence of these regimes is analysed and their geomorphological significance is presented based on the altitudinal differences of the two monitoring sites on the occurrence of the different regimes and on field observations a conceptual model for the altitudinal and seasonal zoning of the daily thermal regimes of the ground is presented this model was prepared for the serra da estrela but it can be used in other mediterranean or tropical areas if altitude and seasonal precipitation differences are taken in explanation d 2002 elsevier science b v all rights reserved

sedimentary charcoal as an indicator of late holocene drought in the sierra nevada california and its relevance to the future a holocene record of climate fire and vegetation regimes was reconstructed for siesta lake yosemite national park california using fossil pollen and charcoal from lake sediments these reconstructions were generated to provide a long term perspective on drought in the sierra nevada the sedimentary record is in agreement with other long term records of climate and vegetation from the sierra nevada and the records of climate and fire for the last c 1000 years are in agreement with tree ring and hydrological studies this correspondence suggests that sedimentary charcoal and pollen are reliable indicators of change in climate vegetation and fire frequency through time the fire frequencies associated with the droughts of the mediaeval warm period are only half as great as those recorded during the early holocene insolation maximum model results suggest that the temperature increases associated with the insolation maximum are a good analogue for those expected with global warming if this is the ca

high elevation paleoenvironmental change during mis 6 4 in the central rockies of colorado as determined from pollen analysis abstract paleoecological studies from rocky mountain usa high elevations encompassing the previous interglacial mis 5e are rare the 10 m composite profile from the ziegler reservoir fossil site 2705 m asl of central colorado allows us to determine paleoenvironments from marine oxygen isotope stages mis 6 4 using pollen zones that are approximately equivalent to marine oxygen isotope stages during pollen zone pz 6 time pollen assemblages dominated by artemisia sagebrush suggest that alpine tundra or steppe occurred nearby the transition to pz 5e was characterized by a rapid increase in tree pollen initially picea spruce and pinus pine but also quercus oak and pseudotsuga menziesii douglas fir non arboreal pollen nap types increased during pz 5d while abies fir and juniperus juniper increased during pz 5c pollen evidence suggests that temperatures during pz 5b were as cold as during pz 6 with the site again surrounded by alpine tundra picea dominated during pz 5a before the onset of cooler conditions during pz 4 the mis 6 mis 5e transition here was similar to the mis 2 mis 1 transition at other rocky mountain sites however the ziegler reservoir pollen record contains evidence suggesting unexpected climatic trends at this site including a warmer than expected mis 5d and cooler than expected mis 5b

middle and late wisconsin paleobotanic and paleoclimatic records from the southern colorado plateau usa the colorado plateau is a distinct physiographic province in western north america which presently straddles the transition between summer wet and summer dry climatic regimes to the south and northwest respectively in addition to climate the diversity of environments and plant communities on the colorado plateau has resulted from extreme topographic diversity desert lowlands as low as 360 m elevation are surrounded by forested plateaus and even higher peaks greater than 3800 m elevation this environmental diversity provides a unique opportunity to study the history of biotic communities in an arid region of north america although the colorado plateau harbours numerous potential sites the paleoecological record of the plateau is poorly known potential deposits for analysis include packrat middens alluvial and cave sites at lower elevations and lake bog and wetland sites at higher elevations forty six sites have been analysed across the nearly 337 000 km2 region of which 27 contain records that span marine oxygen isotope stage is 2 data with is 3 information coming from only 12 sites most is 2 and 3 sites are clustered along the lowland regions of the colorado river corridor and the uplands of the mogollon rim area we compiled selected data from long paleoecological records to examine patterns of vegetation and climate change across the southern colorado plateau for the middle and late wisconsin during the middle wisconsin mixed conifers covered middle elevations presently dominated by ponderosa pine pinus ponderosa and juniper juniperus woodland grew at elevations today covered by blackbrush coleogyne and sagebrush artemisia desert during the late wisconsin boreal conifers primarily engelmann spruce picea engelmannii replaced the mixed conifer association estimates of mean annual temperatures mat during is 3 were at least 3 4 c cooler than today whereas is 2 mat estimates are at least 5 c colder our investigation of millennial scale climatic variability within the region provided equivocal results the packrat midden sequence could not distinguish vegetation changes that might be associated with heinrich events in the north atlantic from the lake records however many heinrich events were associated with generally drier intervals often with elevated sagebrush pollen concentrations future paleoecological investigations should concentrate on the northern colorado plateau as well as the eastern and western margins additional sites along with closer spaced sampling in regions already studied will be important in determining the history of important climatic phenomena such as the timing of the arizona monsoon

earthquake induced rockfall hazard zoning abstract a methodology for quantitative probabilistic hazard zonation for earthquake induced rockfalls is presented and demonstrated in the area of friuli eastern italian alps affected by the 1976 mw 6 5 earthquake four rockfall datasets have been prepared both from historical data analysis and field surveys the methodology relies on a three dimensional hazard vector whose components include the rockfall kinetic energy the fly height and the annual frequency the values of the first two components are calculated for each location along the slope using the 3d rockfall runout simulator hy stone the rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency the annual onset frequency is calculated through a procedure that combines the extent of unstable areas calculated for 10 different seismic hazard scenarios with different annual frequencies of occurrence and the magnitude relative frequency relationship of blocks as derived from the collected field data for each annual frequency of occurrence the unstable area is calculated as a function of morphometric and earthquake characteristics a series of discriminant analysis models using the rockfall datasets and dems of different resolution 1 and 10 m identified the controlling variables and verified the model robustness in contrast with previously published relationships we show that the slope curvature plays a relevant role in the computation of the unstable area

stress induced by topography and crustal density heterogeneities implication for the seismicity of southeastern canada abstract the stress induced by the topography and density heterogeneities in the lithosphere has been calculated for a large region covering most of southeastern canada the calculations assume that the lithosphere consists of a three dimensional layered elastic slab overlaying an inviscid fluid the calculations show that the deviatoric stress difference induced by density heterogeneities and the topographic load is of the same order as the regional tectonic stress tens of mpa stresses appear largest along the saint lawrence valley where most of the seismicity is located e g the charlevoix and the lower saint lawrence areas the charlevoix seismic zone was analyzed in greater detail and theoretical focal mechanisms were computed this analysis shows that the stress induced by surface and internal loading is compressional in this area and the principal stress orientation is consistent with earthquake focal mechanisms and in situ measurements

underplated units in an accretionary complex melange of the shimanto belt of eastern shikoku southwest japan imbricated thrust stacks composed of melange and oceanic slabs occur in the shimanto belt eastern shikoku sw japan the melanges are divided into two types melange i consists of lenticular sandstone blocks surrounded by scaly shale matrix and melange ii is composed of blocks of oceanic material such as basalts cherts and red shale in a scaly matrix of shale melange ii is observed only near the boundaries between melange i and oceanic slabs the fabric of melange i indicates progressive deformation during underthrusting of originally coherent trench fill turbidites layer parallel extension characterizes early deformation and is divided into two stages an early stage formed during normal faulting and a subseguent stage formed perpendicular to the early extension the early extension is interpreted in terms of riedel shear associated with layer parallel shearing and tectonically induced loading normal to the layering the second extension is due to sticking thrust movement late deformation of melange i is represented by folding in association with layer parallel shearing this appears to be related to compression just before or during underplating of melange i beneath the accretionary prism layer parallel shear extends downward due to strain hardening of sheared sediments and then reaches to the base of the sediments subsequently the shear zone penetrates pelagic sediments and finally oceanic basement at this time melange ii is formed by the shearing an imbricated stack of melanges i ii and oceanic slabs forms duplexes during the underplating process the weak metamorphism of the melange complex in the study area suggests that underplating occurs at shallow depths where trench fill is thin

tree ring analysis in the reconstruction of slope instabilities associated with earthquakes and precipitation the crimean mountains ukraine the crimean mountains in ukraine constitute a seismically active region that is abundant in various types of mass movement the limestone escarpments that rise above the black sea coast in the vicinity of the town of yalta are particularly subject to considerable rockfall landslide and debris flow processes that often endanger infrastructure and human life one of these very active slopes is the area of the ancient taraktash rockslide characterised by active block type movements lateral spreading toppling and incipient sliding rockfalls ongoing sliding activities and debris flows the aims of this study were i to employ tree ring analysis to reconstruct a record of slope instabilities mainly block type movements rockfalls landslides and debris flows within the taraktash slope deformation over a period of more than two centuries and ii to establish the degree of correlation between periods of enhanced slope activity and both historical earthquakes and climatic data the temporal frequency of significant slope processes was addressed through a tree ring analysis that took 738 increment cores from 255 crimean pine trees pinus nigra ssp pallasiana the tree ring record reveals periods of increased activity of block type movements rockfalls and landslides during the major earthquakes in 1790 1875 1927 and 1986 although the slope processes studied are predominantly driven by seismic activity their intensity and duration are also dependent on climatic factors this is especially true for landslides and debris flows which occurred mainly in years characterised by high precipitation totals

seasonal changes in the sediment flux on steep hillslopes in a humid diurnal frost environment mountain hillslopes are generally shaped by a combination of various types of sediment transport processes e g surface erosion soil creep and dry ravel which can occur simultaneously in the same area since sediment transport is generally affected by multiple microclimatic factors such as heavy rainfall and changes in ground temperature the types of predominant sediment transport processes vary by season we conducted field observations in the southern japanese alps in the period from 2009 to 2013 using sediment traps and time lapse cameras to investigate the seasonal changes in the type and flux of hillslope sediment transport on steep mountains in which both rainfall and diurnal freeze thaw triggered sediment transport in winter and early spring sediment transport via diurnal freeze thaw soil creep and dry ravel was highly active whereas rainfall induced soil creep and selective transport by overland flow were active in summer and autumn when precipitation is abundant average sediment flux of 0 033 and 0 074 kg m 1 day 1 respectively sediment flux was spatially variable and was affected by the form of the slope sediment flux on the concave slope was higher than on the ridge shaped slope during both freeze thaw and rainfall periods sediment flux on an old landslide exceeded that in second growth forest regardless of the slope shape temporal changes in the sediment flux were not completely synchronized among monitoring plots and were affected by slope shape grain size and episodic sediment supply events such as release of sediment from woody debris copyright 2016 john wiley sons ltd

rockfall triggering by cyclic thermal stressing of exfoliation fractures exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures which in turn can lead to potentially hazardous rockfalls although a number of mechanisms are known to trigger rockfalls many rockfalls occur during periods when likely triggers such as precipitation seismic activity and freezing conditions are absent it has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces which can cause outward expansion here we use data from 3 5 years of field monitoring of an exfoliating granite cliff in yosemite national park in california usa to assess the magnitude and temporal pattern of thermally induced rock deformation from a thermodynamic analysis we find that daily seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls and that cyclic thermal forcing may enhance the efficacy of other more typical rockfall triggers some rockfalls occur without obvious triggers such as seismicity or freeze thaw conditions temperature and deformation patterns on a granite cliff suggest that cyclical thermal forcing can progressively open fractures and trigger rockfalls

tree ring based assessment of rockfall frequency on talus slopes at sola d andorra eastern pyrenees abstract the determination of the frequency of rockfall events continues to challenge quantitative hazard assessments in most mountain areas dendrogeomorphological analysis was used to assess rockfall frequency on talus slopes at sola d andorra eastern pyrenees andorra rockfall events were dated at two sites one at the outlet of a chute and the other below a rock wall the impact wounds visible on the tree surface were analyzed with a seasonal temporal resolution at each site trees were sampled in three forest strips 15 to 30 m wide located at different heights on the talus all the trees with visible injuries in the strips were sampled rockfall frequency cannot be assessed by a simple analysis of time series of tree damage a satisfactory assessment requires a prior interpretation of the location of the damaged trees in relation to a number of rockfall events at sola d andorra the rockfall chronology was reconstructed for the last 25 years by dating visible wounds for older periods the tree wound record of rockfalls is incomplete owing to progressive closure of wounds wounds exceeding 40 years in age had already disappeared from the tree surface in the study area our results show a clear reduction of the rockfall frequency down the talus a noticeable lateral change in frequency and an influence of source morphology chute or wall on rockfall activity on the talus

revised age of deglaciation of lake emma based on new radiocarbon and macrofossil analyses abstract previous radiocarbon ages of detrital moss fragments in basal organic sediments of lake emma indicated that extensive deglaciation of the san juan mountains occurred prior to 14 900 yr b p carrara et al 1984 paleoecological analyses of insect and plant macrofossils from these basal sediments cast doubt on the reliability of the radiocarbon ages subsequent accelerator radiocarbon dates of insect fossils and wood fragments indicate an early holocene age rather than a late pleistocene age for the basal sediments of lake emma these new radiocarbon ages suggest that by at least 10 000 yr b p deglaciation of the san juan mountains was complete the insect and plant macrofossils from the basal organic sediments indicate a higher than present treeline during the early holocene the insect assemblages consisted of about 30 bark beetles which contrasts markedly with the composition of insects from modern lake sediments and modern specimens collected in the lake emma cirque in which bark beetles comprise only about 3 of the assemblages in addition in the fossil assemblages there were a number of flightless insect species not subject to upslope transport by wind indicative of coniferous forest environments these insects were likewise absent in the modern assemblage

precise cosmogenic 10be measurements in western north america support for a global younger dryas cooling event the inner titcomb lakes moraine in the wind river mountains wyoming has been dated with a precision of 5 using accelerator mass spectrometric measurements of cosmogenic 10be in surface samples from nine boulders resting on its crest the age of this moraine is 11 4 0 5 to 13 8 0 6 ka the range in age is due to the uncertainty in the 10be production rate and uncertainties in rock erosion rate and shielding of cosmic rays by snow additional exposure ages on bedrock and boulder surfaces that are stratigraphically younger and older than the inner titcomb lakes moraine conform with this age the exposure ages of the inner titcomb lakes moraine overlap the north atlantic younger dryas event 12 8 0 2 to 11 5 0 3 ka

numerical modeling of flexural stresses in the upper crust of ne brazil implications for stress regimes in intraplate settings abstract we model the contribution of the stresses generated by the topography and density heterogeneities in the stress field of ne brazil and the interplay between these and regional stresses our model consists of a horizontally layered elastic slab the lithosphere that floats above an inviscid fluid the asthenosphere where the surface load is generated by the topography and bathymetry and the internal loads are calculated from the bouguer anomalies the deviatoric flexural stresses are calculated in the fourier domain our results showed local flexural stresses with magnitudes comparable to those of the plate wide stresses and mainly controlled by the long wavelength bouguer anomalies scenarios for the total stress field were calculated by superposing different values for an e w oriented regional compression we predict the stress axes orientations and stress regimes for the equatorial margin and the pernambuco shear zone pesz region however we highlight the importance of spreading stresses not considered here in rotating the maximum horizontal compression shmax predictions the prediction of stress regime and stress axes orientation in pesz using low to zero regional compression suggest that a decoupling of the shallow stresses from the plate wide stresses might occur in this region another possible explanation found was that the spreading stresses might counterbalance the regional stresses we conclude that the superposition of principally flexural and plate wide stresses explains reasonably the observed stress regimes and shmax orientations in a great part of ne brazil furthermore flexural stresses are playing an important role in the reactivation of the pesz possibly controlling the stress field

evidence for cirque glaciation in the colorado front range during the younger dryas chronozone abstract late pleistocene glacial chronologies developed for the front range mountains of colorado include two or more cirque glacier advances locally known as the satanta peak advances sediment cores were recovered from sky pond an alpine lake 3320 m located less than 100 m downvalley from a moraine that exhibits late pleistocene to early holocene relative age features and appears to correlate to the satanta peak deposits one of the cores penetrated 0 5 m of basal diamict and recovered 3 3 m of overlying sediments that are predominantly gyttja an accelerator mass spectrometry ams age of 12 040 60 yr14c b p was obtained from directly above the basal diamict and is similar to other reported ages for cirque deglaciation in the front range mountains the lower portion of the gyttja contains an interval of clastic sediments that show characteristics consistent with glacial activity in alpine catchments radiocarbon ages obtained from below and near the upper contact of this clastic interval are 11 070 50 and 9970 8014c yr b p respectively an additional ams age of 10 410 9014c yr b p was obtained from within the clastic interval in a second core the most likely source for this interval of clastic sediments is a moraine situated directly upvalley from sky pond and consequently it appears that the deposition of this moraine was coeval with the european younger dryas event 11 000 10 00014c yr b p similarities in soil development weathering features and altitude between this moraine and the type satanta peak moraines suggest that the moraines are correlative these findings are in agreement with a growing body of evidence that suggests a relatively minor advance of alpine glaciers occurred in the north american rockies during the younger dryas chron

integrated palynological and molecular analyses of late holocene deposits from lake milkowskie ne poland verification of local human impact on environment commonly applied methods such as pollen analysis charcoal analysis and archaeological studies make it possible to reconstruct the trend of changes in vegetation during the holocene and determine the role of humans in its transformation however it is not always possible to obtain a complete picture of changes which took place in the past and the reasons for their occurrence this paper presents the results of molecular investigations of lacustrine sediments from lake milkowskie aimed at confirming human presence in the vicinity of the lake and its correlation with the palynological and archaeological data the molecular analyses were based on identification of ancient dna adna of faecal bacteria as indicators of human and cattle presence application of comprehensive studies comprising both palaeoenvironmental and molecular methods allowed a detailed determination of the stages of human presence in the vicinity of the lake and confirms the anthropogenic impact on the changes of local plant communities

a postglacial palaeoecological record from the san juan mountains of colorado usa fire climate and vegetation history continuous sediment charcoal and pollen records were developed from a 4 5 m sediment core from little molas lake lml 3370 m elevation san juan county co lml formed by 11 200 cal bp subsequent to glacial retreat turbated clay and gyttja was derived from in lake productivity and outwash sediments from the drainage basin from 1 1 200 cal bp until 10 200 cal bp cessation of glacial input and replacement of tundra with picea forest correlates with the termination of the younger dryas and indicates warming an increase in diploxylon pollen cf p ponderosa probably from lower elevations reflects the influence of the southwestern monsoon c 10 160 cal bp pollen ratios indicate that picea and other conifers persisted near the lake for the remainer of the holocene the driest holocene period occurs c 6200 to 5900 cal bp when lake levels were the lowest as indicated by all the proxy records wetter conditions during the last c 2600 cal bp favoured the expansion of p edulis and p ponderosa lat

palynological evidence for late and postglacial environmental change in central colorado abstract a sediment core recovered from lost park 39 17 30 n 105 32 30 w elevation 3079 m provides palynological evidence for postglacial vegetational and environmental change in the central front range of colorado pine spruce woodland was the dominant vegetation type throughout the 12 000 yr long record nonarboreal taxa however showed substantial changes from 11 800 to 9100 14 c yr b p high artemisia levels suggest steppe vegetation indicative of a climate cooler than that at present with an annual precipitation regime dominated by winter moisture the pollen spectra of this interval resemble modern spectra at two sites within colorado and wyoming comparisons of modern climatic data suggest that lost park may have experienced winter temperatures 3 to 3 5 c colder than those at present and monthly winter precipitation levels 3 5 cm higher than those at present during this late glacial time lower artemisia coupled with increases in poaceae pollen suggest a shift to warmer conditions dominated by summer monsoon precipitation around 9100 14 c yr b p increased charcoal occurrences between 6000 and 4000 14 c yr b p may suggest the onset of drier summer conditions that would be expected with a waning summer monsoon circulation at that time since 1800 14 c yr b p a resurgence in artemisia pollen suggests a return to relatively cool and or dry conditions similar to the present climate

influence of daily surface temperature fluctuations on rock slope stability case study of the rochers de valabres slope france the present paper describes a rockfall that has affected the rochers de valabres slope france s southern alps region and discusses one possible mechanism for the occurrence of this rockfall along with the potential for future ones in the absence of an obvious explanatory trigger factor we set out to examine whether natural daily surface temperature changes could have played a role in this event in particular it is suspected that these slight yet repeated perturbations may be a preparatory factor for rockfalls with a day to day cumulative effect a numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position to investigate this notion more thoroughly a currently vulnerable part of the rochers de valabres slope has been instrumented with a high precision geodetic monitoring system total station it is believed that this device is able to capture thermally induced movements if specific precautions are taken the instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability measured data with a precision level never before achieved on rock slopes are compared herein with numerical modelling results the initial conclusions of the long term study we are conducting indicate that surface temperature changes play an important while not easily quantifiable role in preparing rockfalls

spatial variations of holocene climatic change in the yellowstone region abstract the paleoecologic record of the northern rocky mountains shows considerable spatial variability which has been difficult to explain as a unified response to large scale changes in effective moisture or temperature through time comparison of past and present climatic patterns suggests that the spatial heterogeneity in the fossil record arises from a local response to the effects of greater summer solar radiation during the early holocene solar radiation directly determines evapotranspiration and indirectly controls the strength of the summer monsoon and the eastern pacific subtropical high pressure system the yellowstone region provides an example of an area where the indirect effects of solar radiation are manifest by the juxtaposition of two contrasting climatic regimes today and where these regimes were amplified during the early holocene fossil pollen data suggest that central and southern yellowstone the summer dry area became drier in the early holocene while northern yellowstone the summer wet area became wetter the boundary between regimes however is controlled by topography and has not changed significantly in the holocene the spatial variations of holocene vegetation and climatic changes in the northern rocky mountains may therefore be explained as a trade off between strengthened monsoonal circulation and a stronger subtropical high in the early holocene and the relative importance of these precipitation regimes on a topographically complex landscape

permafrost thaw and destabilization of alpine rock walls in the hot summer of 2003 1 exceptional rockfall occurred throughout the alps during the unusually hot summer of 2003 it is likely related to the fast thermal reaction of the subsurface of steep rock slopes and a corresponding destabilization of ice filled discontinuities this suggests that rockfall may be a direct and unexpectedly fast impact of climate change based upon our measurements in alpine rock faces we present model simulations illustrating the distribution and degradation of permafrost where the summer of 2003 has resulted in extreme thaw we argue that hotter summers predicted by climate models for the coming decades will result in reduced stability of many alpine rock walls

evidence for a major late precambrian tectonic event rifting in the eastern midcontinent region united states recently acquired gravity and aeromagnetic data delineate a large linear gravity anomaly which extends through eastern kentucky and tennessee and coincides with a zone of complex high amplitude magnetic anomalies basement lithologies in the area can be interpreted as a bimodal volcanic suite which is locally peralkaline in nature these volcanics appear to be metamorphosed where they lie east of the grenville front suggesting they predate the grenville metamorphic event the available gravity aeromagnetic seismic refraction and petrologic data along with regional correlations suggest that the best tectonic interpretation of these data is that a keweenawan rift zone extended through the area this rift can be roughly outlined by the gravity high which is locally offset suggesting the presence of transform faults the boundaries of this rift have been locally reactivated and in fact a recent earthquake was located along its western boundary in northern kentucky

dendrogeomorphic dating of rockfalls on low latitude high elevation slopes rodadero iztaccihuatl volcano mexico dynamics and rates of rockfalls have been repeatedly studied in mountain environments with archival records as well as lichenometric radiocarbon or dendrogeomorphic approaches in this study we test the potential of conifers growing at a low latitude high elevation site as a dendrogeomorphic tool to reconstruct to calendar dates associated rockfall activity analysis is based on tree ring records of mexican mountain pine pinus hartwegii lindl growing at timberline 4000 m above sea level a s l and at the runout fringe of a north northeast nne facing slope of the dormant iztaccihuatl volcano mexico which is subject to frequent rockfalls the potential and limitations of tree ring data are demonstrated based on 67 rockfall impacts dated in the increment ring series of 24 trees since ad 1836 while findings of this paper are site specific the study clearly shows the potential of dendrogeomorphic approaches in extra alpine low latitude environments and for the understanding of rockfall processes in space and time copyright 2011 john wiley sons ltd

deglaciation and postglacial timberline in the san juan mountains colorado abstract lake emma which no longer exists because of a mining accident was a tarn in a south facing cirque near the headwaters of the animas river in the san juan mountains of southwestern colorado during the pinedale glaciation this area was covered by a large transection glacier centered over the lake emma region three radiocarbon dates on basal organic sediment from lake emma indicate that by ca 15 000 yr b p this glacier one of the largest in the southern rocky mountains no longer existed twenty two radiocarbon dates on picea and abies krummholz fragments in the lake emma deposits indicate that from ca 9600 to 7800 yr b p from 6700 to 5600 yr b p and at 3100 yr b p the krummholz limit was at least 70 m higher than present these data in conjunction with picea pinus pollen ratios from both the lake emma site and the hurricane basin site of j t andrews p e carrara f b king and r struckenrath 1975 quaternary research 5 173 197 suggest than from ca 9600 to 3000 yr b p timberline in the san juan mountains was higher than present cooling apparently began ca 3000 yr b p as indicated by decreases in both the percentage of picea pollen and picea pinus pollen ratios at the hurricane basin site andrews et al 1975 cooling is also suggested by the lack of picea or abies fragments younger than 3000 yr b p at either the lake emma or the hurricane basin site

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

a 560 year record of santa ana fires reconstructed from charcoal deposited in the santa barbara basin california microscopic charcoal from varved santa barbara basin sediments was used to reconstruct a 560 yr record a d 1425 to 1985 of santa ana fires comparison of large 3750 m2 charcoal with documented fire records in the santa barbara ranger district shows that high accumulations correspond to large fires 20 000 ha that occurred during santa ana conditions the charcoal record reconstructed a minimum of 20 large fires in the santa barbara region during the study period the average time between fires shows no distinct change across three different land use periods the chumash period apparently characterized by frequent burning the spanish early american period with nominal fire control and the 20th century with active fire suppression pollen data support the conclusion that the fire regime has not dramatically changed during the last 500 yr comparison of large charcoal particle accumulation rates and precipitation reconstructed from tree rings show a strong relationship between climate and fire history with large fires consistently occurring at the end of wet periods and the beginning of droughts

a 35 000 year vegetation and climate history from potato lake mogollon rim arizona abstract a new record from potato lake central arizona details vegetation and climate changes since the mid wisconsin for the southern colorado plateau recovery of a longer record discrimination of pine pollen to species groups and identification of macrofossil remains extend whiteside s 1965 original study during the mid wisconsin ca 35 000 21 000 yr b p a mixed forest of engelmann spruce picea engelmannii and other conifers grew at the site suggesting a minimum elevational vegetation depression of ca 460 m summer temperatures were as much as 5 c cooler than today during the late wisconsin ca 21 000 10 400 yr b p even cooler temperatures 7 c colder than today ca 800 m depression allowed engelmann spruce alone to predominate warming by ca 10 400 yr b p led to the establishment of the modern ponderosa pine pinus ponderosa forest thus the mid wisconsin was not warm enough to support ponderosa pine forests in regions where the species predominates today climatic estimates presented here are consistent with other lines of evidence suggesting a cool and or wet mid wisconsin and a cold and or wet late wisconsin climate for much of the southwest potato lake was almost completely dry during the mid holocene but lake levels increased to near modern conditions by ca 3000 yr b p

talus slope characterization in tasiapik valley subarctic quebec evidence of past and present slope processes abstract topographic granulometric morphometric petrographic and vegetation surveys were conducted on the slopes of tasiapik valley near umiujaq nunavik to document mass wasting processes and their geomorphological impact talus slopes widespread at the foot of the steep rockwalls of tasiapik valley are an important landscape feature in the area the lithology of the slope deposits attest their local origin namely the result of rockfalls coming from the adjacent wall locally poor vegetation covering the clasts exhibits recently fallen debris elsewhere dense shrub cover has colonized the slopes demonstrating the low activity nowadays on going periglacial processes have led to extensive dismantling of the rockface enabling for debris supply following the last deglaciation paraglacial processes have potentially favoured slope instabilities the use of automatic cameras during the winter 2017 2018 resulted in the observation of many snow avalanche events however few rockfall events have been observed spring snow avalanches have carried rock debris to the talus at the foot of the slope snow also enabled debris redistribution on the slopes

late glacial and holocene vegetation history and paleoclimate of the kaibab plateau arizona sediment cores spanning the last 13 500 calendar years cal yr were obtained from two lakes fracas lake 2518 m bear lake 2778 m on the kaibab plateau in northern arizona pollen and plant macrofossil records indicate that before 12 900 cal yr b p high elevation landscapes of the kaibab plateau near bear lake were covered by alpine tundra while lower elevations near fracas lake were occupied by picea woodland at12 900 cal yr b p picea engelmannii and abies lasiocarpa forest expanded upward to occupy the top of the plateau pinus ponderosa arrived near fracas lake 11 000 cal yr b p replacing picea forests since then pinus ponderosa forest has dominated the fracas lake area pinus ponderosa did not appear at bear lake until9730 cal yr b p mixed forests of picea mainly picea pungens abies lasiocarpa pinus ponderosa a ndpseudotsuga after8000 cal yr b p grew near bear lake for the remainder of the holocene picea engelmannii populations reexpanded near bear lake after 4000 cal yr b p charcoal records indicate that fire probably helpedpinus ponderosa to become established near bear lake climate changes on the kaibab plateau since the late glacial were inferred from lake levels and vegetation patterns the late glacial 11 000 cal yr b p was cold and probably wet the early holocene 11 000 to8000 cal yr b p was cooler than today and may have been the wettest period fracas lake and bear lake were probably deepest then during this period a strengthened summer monsoon brought in more moisture from the eastern pacific ocean and the gulf of mexico during the dry and warm mid holocene fracas lake and bear lake experienced water level declines the late holocene was relatively wet and cool again and aquatic plants were abundant in the two lakes increasing effective moisture in the late holocene was related to decreasing summer insolation 1999 elsevier science b v all rights reserved

channel initiation by surface and subsurface flows in a steep catchment of the akaishi mountains japan abstract channel initiation which is a key factor in the evolution of mountain landforms is caused by a combination of various hydrogeomorphic processes we modeled the channel initiation in steep mountains on the basis of the physical mechanism for sediment transport by surface and subsurface flows field investigations and geographic information systems gis analysis in the higashi gouchi catchment of central japan showed that our model can well explain the area slope relationship in steep and highly incised subcatchments in which surface flow and shallow underground water would be the dominant flow components in contrast the area slope relationship is not clear in gentler subcatchments in which the contribution of deeper flow components i e deep underground water on the entire runoff is not negligible thus the contribution of each runoff component to the total runoff is an important factor affecting the location of the channel head most channel heads in the deeply incised subcatchments in the higashi gouchi catchment have been formed by surface and subsurface flows although many landslides have also occurred around the channel heads compared with the dominant flow components activity of sediment supply from hillslopes might be a minor factor in determining the area slope relationship for locating the channel head

frost weathering and rockwall erosion in the southeastern swiss alps long term 1994 2006 observations abstract rates and processes of frost weathering in the alps were investigated by visual observations of intensively shattered rocks continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity rapid frost weathering of hard intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock otherwise rocks require pre existing weakness or a long exposure period for intensively shattered automated monitoring shows that crack opening occurs at three scales including small opening accompanying short term frost cycles slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow melt water during seasonal thawing the opening events require at least partial water saturation in the crack the repetition of crack opening frost wedging results in permanent opening and finally debris dislocation debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0 1 mm a 1 with significant spatial and inter annual variations occasional large boulder falls significantly raise the rockwall erosion rates controlled by such factors as the joint distribution in the bedrock repetition of annual freeze thaw cycles and extraordinary summer thaw

rapid response of alpine timberline vegetation to the younger dryas climate oscillation in the colorado rocky mountains usa paleobotanical records from two high altitude 3 300 m sites in colorado show a clear and immediate response to the younger dryas climate oscillation the black mountain lake and sky pond records indicate that alpine timberline migrated upslope to near modern elevations during the late bolling allerod 13 6 12 9 ka subsequent declines in arboreal pollen percentages and accumulation rates during the younger dryas interval 12 9 11 7 ka reflect a downslope displacement of the alpine timberline ecotone of 60 120 m in elevation this change translates to a cooling of summer temperature by approximately 0 4 0 9 c and is consistent with proposed younger dryas advances of alpine glaciers in the rocky mountains to positions close to little ice age maxima alpine timberline readvanced upslope to elevations above both sites between 11 7 and 11 4 ka the concomitant response of temperature sensitive alpine timberline vegetation in colorado and late glacial changes in north atlantic thermohaline circulating implicates a rapid widespread atmospheric transmission of the younger dryas climate oscillation

postglacial fire vegetation and climate history in the clearwater range northern idaho usa the environmental history of the northern rocky mountains was reconstructed using lake sediments from burnt knob lake idaho and comparing the results with those from other previously published sites in the region to understand how vegetation and fire regimes responded to large scale climate changes during the holocene vegetation reconstructions indicate parkland or alpine meadow at the end of the glacial period indicating cold dry conditions from 14 000 to 12 000 cal yr b p abundant pinus pollen suggests warmer moister conditions than the previous period most sites record the development of a forest with pseudotsuga ca 9500 cal yr b p indicating warm dry climate coincident with the summer insolation maximum as the amplification of the seasonal cycle of insolation waned during the middle holocene pseudotsugawas replaced by pinus and abies suggesting cool moist conditions the fire reconstructions show less synchroneity in general the sites west of the continental divide display a fire frequency maximum around 12 000 8000 cal yr b p which coincides with the interval of high summer insolation and stronger than present subtropical high the sites on the east side of the continental divide have the highest fire frequency ca 6000 3500 cal yr b p and may be responding to a decrease in summer precipitation as monsoonal circulation weakened in the middle and late holocene this study demonstrated that the fire frequency of the last two decades does not exceed the historical range of variability in that periods of even higher than present fire frequency occurred in the past

rock moisture measurements techniques results and implications for weathering rock moisture is an important factor for the intensity and distribution of frost weathering processes however quantitative measurements are scarce which is partly due to the lack of reliable measurement techniques this paper presents five different techniques for obtaining rock moisture data while collecting rock pieces and two dimensional geoelectric measurements allow determination of the spatial moisture distribution the temporal variability can be derived from conductivity and time domain reflectometry records computer simulations using rock properties and climatic records as input data render it possible to clarify the important aspects that are responsible for the moisture distribution it proved to be advisable to use several methods to check and validate the results the results obtained in study areas in the bavarian alps make it clear that direct rainfall is the main source of rock moisture the influence of snow is limited to the immediate vicinity of the snow fields and is not equally pronounced at different times and positions rock moisture levels are higher in summer than they are in winter since in winter less water is supplied in liquid form northerly exposed rockwalls are generally more moist than those exposed in a southerly direction which is due to the different insolation as well as to the wind direction during rainfall in every position the rock is on average wetter on the inside than it is on the surface this means that shallow frost cycles as typical for south exposed sites are not affecting weathering since they take place at a depth level that is mostly dried out numerous spatial and temporal patterns of rockfall found in the same study areas can be explained through variations in rock moisture thus the moisture content of the rock is considered to be one of the major controlling factors of the frost shattering rate copyright 2005 john wiley sons ltd

achieving a more realistic assessment of rockfall hazards by coupling three dimensional process models and field based tree ring data sound knowledge of the spatial and temporal patterns of rockfalls is fundamental for the management of this very common hazard in mountain environments process based three dimensional simulation models are nowadays capable of reproducing the spatial distribution of rockfall occurrences with reasonable accuracy through the simulation of numerous individual trajectories on highly resolved digital terrain models at the same time however simulation models typically fail to quantify the real frequency of rockfalls in terms of return intervals the analysis of impact scars on trees in contrast yields real rockfall frequencies but trees may not be present at the location of interest and rare trajectories may not necessarily be captured due to the limited age of forest stands in this article we demonstrate that the coupling of modeling with tree ring techniques may overcome the limitations inherent to both approaches based on the analysis of 64 cells 40 m 40 m of a rockfall slope located above a 1631 m long road section in the swiss alps we illustrate results from 488 rockfalls detected in 1260 trees we illustrate that tree impact data cannot only be used i to reconstruct the real frequency of rockfalls for individual cells but that they also serve ii the calibration of the rockfall model rockyfor3d as well as iii the transformation of simulated trajectories into real frequencies calibrated simulation results are in good agreement with real rockfall frequencies and exhibit significant differences in rockfall activity between the cells zones along the road section real frequencies expressed as rock passages per meter road section also enable quantification and direct comparison of the hazard potential between the zones the contribution provides an approach for hazard zoning procedures that complements traditional methods with a quantification of rockfall frequencies in terms of return intervals through a systematic inclusion of impact records in trees

a local weakening of the brittle ductile transition can explain some intraplate seismic zones abstract a decrease in the strength of a localized area of the lower crust would decrease the depth to the brittle ductile transition and concentrate stress in the stronger elastic crust around and above the zone of decreased strength deformation within the zone of weakened lower crust would occur through viscous or dislocation creep in response to regional plate stress as well as by elastic failure in small earthquakes two dimensional finite element models of zones of weakness subjected to a regional plate stress predict stress amplification of 10 100 surrounding the local decrease in strength a finite element model for an irregular zone of weakness in the lower crust can generate stress directions and relative magnitudes that satisfy the focal mechanisms and seismicity of southeastern tennessee an analysis of the displacements and stresses in the central area of decreased crustal strength suggests that strike slip faulting should dominate above this zone the strike slip faulting should exhibit a strong thrust component the compression and extension of the crust surrounding the weakened zone at the level of the brittle ductile transition predicts that the dominant strike slip faulting should exhibit components of normal faulting on the edges of the weak zone which are near a line through the weak zone parallel to the regional stress and reverse faulting on the edges which are near a line transverse to the regional stress the seismicity of southeastern tennessee is diffused over a narrow elliptical zone trending ne the greatest concentration of activity is near the center the central zone is characterized by deep focus strike slip events with predominantly n or e striking nodal planes these events are responding directly to compression in the direction of the regional compressive stress and extension perpendicular to the regional compressive stress within the weak zone the area surrounding the central zone is characterized by focal mechanisms with larger components of reverse or normal fault movements events with normal components are dominant on the edges in line with the regional stress as predicted by the stress model for a weak central zone under stress the agreement between observed earthquake focal mechanisms in southeastern tennessee and models of crustal stress surrounding a zone of weakness suggests that these events may be caused by a zone of weakness in the lower crust

spatial and temporal rockfall activity in a forest stand in the swiss prealps a dendrogeomorphological case study abstract rockfall is a major threat to settlements and transportation routes in large parts of the alps while protective forest stands in many locations undoubtedly reduce rockfall risk little is known about the exact frequency and spatial distribution of rockfall activity in a given place or about how these parameters can be assessed therefore the objective of the present study was to reconstruct rockfall events with dendrogeomorphological methods and to analyse the spatial and temporal rockfall activity in a subalpine forest stand the study site is located in the transit zone of frequently passing rather small rockfall fragments mean diameter of 10 to 20 cm in all 33 stem discs from previously felled picea abies trees found at the foot of schwarzenberg in diemtigtal swiss prealps were sampled and a total number of 301 rockfall events were dated to between a d 1724 and 2002 results showed that the spatial distribution of rockfall changed slightly with time and that rockfall activity increased considerably over the last century in contrast rockfall magnitude presumably remained on a comparable level the seasonal occurrence of rockfall showed a clear peak during the dormant season of trees most probably in early spring furthermore on a 10 year moving average basis rockfall rates were positively correlated with mean annual as well as summer and winter temperatures this means that higher temperatures resulted in increased rockfall activity on the other hand no correlation with annual or seasonal precipitation totals was revealed overall this study provides an appropriate method for the detailed assessment of spatial and temporal variations in rockfall activity in a given place

deciphering the role of solar induced thermal stresses in rock weathering a dearth of direct field observations limits our understanding of individual mechanical weathering processes and how they interact in particular the specific contributions of solar induced thermal stresses to mechanical weathering are poorly characterized here we present an 11 mo data set of cracking using acoustic emissions aes combined with measurements of rock temperature strain and other environmental conditions all recorded continuously for a granite boulder resting on the ground in open sun we also present stresses derived from a numerical model of the temperature and stress fields in the boulder idealized as a uniform elastic sphere experiencing simple solar temperature forcing the thermal model is validated using this study s data most observed cracking coincides with the timing of calculated maximum insolation driven tensile thermal stresses we also observe that most cracking occurs when storms or other weather events strongly perturb the rock surface temperature field at these times we hypothesize that these weather actuated thermal perturbations result in a complex thermal stress distribution that is superimposed on the background stresses arising from simple diurnal forcing these additive stresses ultimately trigger measurable cracking measured locations of observed cracking and surface strain support this hypothesis in that they generally match model predicted locations of maximum solar induced tensile stresses also recorded rock surface strain scales with diurnal temperature cycling and records progressive cumulative extension dilation consistent with ongoing thermal stress driven subcritical crack growth in the boulder our results therefore suggest that 1 insolation related thermal stresses by themselves are of sufficient magnitude to facilitate incremental subcritical crack growth that can subsequently be exploited by other chemical and physical processes and 2 simple insolation can impart an elevated tensile stress field that makes rock more susceptible to cracking triggered by added stress from other weathering mechanisms our observed cracking activity does not correlate simply with environmental conditions including temperature extremes or the often cited 2 c min thermal shock threshold we propose that this lack of correlation is due to both the ever varying ambient stress levels in any rock at earth s surface as well as to the fact that ongoing subcritical crack growth itself will influence a rock s stress field and strength because similar thermal cycling is universally experienced by subaerially exposed rock this study elucidates specific mechanisms by which solar induced thermal stresses may influence virtually all weathering processes

modeling rockfall frequency and bounce height from three dimensional simulation process models and growth disturbances in submontane broadleaved trees the use of dynamic computational methods has become indispensable for the assessment of rockfall hazards and the quantification of uncertainties although a substantial number of models with various degrees of complexity has become available over the past few years models have only rarely been parameterized against observations especially because long term records of rockfalls have proven to be scarce and typically incomplete on forested slopes tree ring analyses may help to fill this gap as they have been shown to provide annually resolved data on past rockfall activity over long periods in this paper a total of 1495 rockfall scars recorded on the stem surface of 1004 trees have been studied at a site in the vercors massif french alps to calibrate the 3d process based simulation model rockyfor3d uncertainties related to the choice of parameters accounting for energy dissipation and surface roughness have been investigated in detail because of the lack of reliable data these parameters typically are estimated based on expert judgments despite the fact that they have significant impacts on runout distances and bounce height we demonstrate that slight variations in roughness can indeed strongly affect the performance of runout modeling and that the decreasing downward gradient observed in field data is properly reproduced only if reduced roughness 10 cm enables blocks to reach the distal parts of the study plot with respect to the height of impacts our results also reveal that differences between simulations and observations can indeed be minimized if softer soil types are preferred during simulation as they typically limit bouncing we conclude that field based dendrogeomorphic approaches represent an objective tool to improve rockfall simulations and to enhance our understanding of parameterization which is of key importance for process dynamics and thus hazard zoning