the geomorphic dynamics and environmental history of an upper deltaic floodplain tract in the sacramento san joaquin delta california usa a multi proxy approach was used to examine the geomorphic dynamics and environmental history of an upper deltaic oodplain tract in the sacramento san joaquin delta california three long cores were collected from the mccormack williamson tract mwt and these cores were analyzed for bulk density loss on ignition ne clay and silt content al concentration magnetic susceptibility pollen and charcoal radiocarbon dates obtained for the cores were converted into calendar years and an age depth model was constructed long term vertical accretion and sedimentation rates were estimated from the age depth model cross core relations show that coarse sediment generally accumulates more rapidly and has greater magnetic susceptibility compared to ne sediment percentage ne and loi data show a strong linear relationship that indicates ooding is the primary mechanism for the deposition of particular organic matter on the oodplain and that landscape wash load has contributed a highly consistent fraction of persistent organic matter averaging 5 5 per cent to the site down core grain size pro les show two hydrological domains in the cores namely millennial ne coarse uctuations superimposed on general up core ning coarse sediment is viewed as channel or near channel overbank deposits whereas ne deposits are considered to be distal overbank ood deposits the coarse ne uctuations are indicative of changing depositional settings as channels migrated laterally across mwt whereas the upward ning trend re ects a combination of self limiting overbank deposition as oodplain elevation increased and decreasing competence as sea level rise reduced ood pulse energy slopes mwt has been cross cut and incised numerous times in the past only to have the channels abandoned and subsequently lled by ne sediment the channels around mwt attained their modern con guration about 4000 years ago mwt likely came under tidal in uence at about 2500 cal bp wetlands have recently developed on mwt but they are inorganic sediment dominated copyright 2004 john wiley sons ltd

lidar assisted identification of an active fault near truckee california abstract we use high resolution 1 5 2 4 points m 2 bare earth airborne light detection and ranging lidar imagery to identify map constrain and visualize fault related geomorphology in densely vegetated terrain surrounding martis creek dam near truckee california bare earth lidar imagery reveals a previously unrecognized and apparently youthful right lateral strike slip fault that exhibits laterally continuous tectonic geomorphic features over a 35 km long zone if these interpretations are correct the fault herein named the polaris fault may represent a significant seismic hazard to the greater truckee lake tahoe and reno carson city regions three dimensional modeling of an offset late quaternary terrace riser indicates a minimum tectonic slip rate of 0 4 0 1 mm yr mapped fault patterns are fairly typical of regional patterns elsewhere in the northern walker lane and are in strong coherence with moderate magnitude historical seismicity of the immediate area as well as the current regional stress regime based on a range of surface rupture lengths and depths to the base of the seismogenic zone we estimate a maximum earthquake magnitude m for the polaris fault to be between 6 4 and 6 9

late quaternary variability of precipitation in southern california and climatic implications clay mineral evidence from the santa barbara basin odp site 893 abstract clay mineral assemblages have been investigated in a sequence of late quaternary age sediments 160 ka from the santa barbara basin off california these predominantly terrigenous sediments contain an assemblage of clay minerals dominated by smectite mostly derived from discharges of the santa clara river together with illite and kaolinite from adjacent relief besides its characteristic clay mineral signature the santa clara river has the largest drainage basin in this region and contributes most of the terrigenous load to the santa barbara basin smectite contents of the sediments in the basin may therefore be used as a proxy for precipitation and run off distinct changes in the relative abundance of smectite allow reconstruction of the pattern of precipitation and its relations with regional environments and global climate this showed that major intervals of precipitation coincide with local development of pine during glacials and oak during terminations and interglacials some expansion of mountain glaciers in the sierra nevada especially when they occur during local minima of insolation and lacustrine developments in the now arid continental interior of california major precipitation intervals started during glacials and persisted during terminations and early interglacials associated with a weak california current and subsequent expansion of warm pacific surface waters in detail major precipitation intervals consist of alternating episodes of higher and lower rainfall modulated by orbital precession with a significant correlation between episodes of high rainfall and minima in precession which were times of increased meridional gradients enhanced poleward heat transfer and northward expansion of tropical waters

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

late pleistocene and holocene faulting in the western truckee basin north of truckee california evidence for active faulting in the truckee basin north of lake tahoe is observed in a meadow containing a scarp and small closed depression shallow hand dug trenches show offset marsh stratigraphy of holocene age lithostratigraphy descriptions and radiocarbon dates indicate the meadow was a marsh during the late quaternary that was abruptly infilled with the deposition of the 7000 yr b p tsoyawata tephra mt mazama the tephra is offset up to 80 cm across a narrow sub vertical north south striking fault zone additional offset of 30 cm occurred across the same structure during the late pleistocene our study provides direct stratigraphic evidence for at least one surface faulting event during the holocene and another in the late pleistocene within the truckee fault zone and provides new constraints on seismic sources capable of significant ground rupture and or shaking in the greater reno tahoe truckee area

insar bias and uncertainty due to the systematic and stochastic tropospheric delay we quantify the bias and uncertainty of interferometric synthetic aperture radar insar displacement time series and their derivatives the displacement velocities by analyzing the systematic and stochastic components of the temporal variation of the tropospheric delay the biases due to the systematic seasonal delay depend on the sar acquisition times whereas the uncertainties depend on the standard deviation of the random delay the number of acquisitions the total time span covered and the covariance of the time series of the stochastic delay between a pixel and the reference we study the contribution of the wet delay to the insar observations along the western india plate boundary using i moderate resolution imaging spectroradiometer precipitable water vapor ii stratified tropospheric delay estimated from the era i global atmospheric model and iii seven envisat insar swaths our analysis indicates that the amplitudes of the annual delay vary by up to 10 cm in this region equivalent to a maximum displacement bias of 24 cm in insar line of sight direction between two epochs assuming envisat is6 beam mode the stratified tropospheric delay correction mitigates this bias and reduces the scatter due to the stochastic delay for 7 years of envisat acquisitions along the western india plate boundary the uncertainty of the insar velocity field due to the residual stochastic wet delay after stratified tropospheric delay correction using the era i model is in the order of 2 mm yr over 100 km and 4 mm yr over 400 km we discuss the implication of the derived uncertainties on the full variance covariance matrix of the insar data

cosmogenic nuclides and the dating of lateglacial and early holocene glacier variations the alpine perspective abstract based on cosmogenic 10 be data from four sites in the alps we discuss geological uncertainties associated with the dating of former cirque and small valley glacier margins at the early lateglacial gschnitz site trins austria a 3000 yr spread in 10 be exposure ages points to prolonged boulder instability three out of seven ages are not included in the mean age calculation which yielded 15 400 1000 yr indistinguishable from the oldest boulder age of 16 130 1040 yr as a result of the distinctive morphology at julier pass switzerland site we are able to exposure date the early 12 300 1300 yr and the late 11 300 600 yr egesen stadial glacier advances younger dryas equivalent not just final retreat at the kromer site austria 10 be exposure ages from five clast supported boulders are indistinguishable within the analytical uncertainties mean age 8400 500 yr in addition to moraine age key factors that may lead to too young ages include degree of matrix vs clast support of the boulders post depositional periglacial activity and tree coverage at the nagelisgratli bedrock site near grimsel pass switzerland exposure ages of 10 760 11 720 yr are consistent with early holocene cirque glacier retreat and underline the marked lack of nuclide inheritance in bedrock exposures in the alps

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

climatic controls of western u s glaciers at the last glacial maximum abstract we use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western united states 18 000 years ago 18 ka the high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late pleistocene mountain glaciers in this region of diverse topography and climate modeling results suggest that climatic controls of these glaciers varied significantly over the western u s glaciers in the northern rocky mountains existed under relatively cold july temperatures and low winter accumulation reflecting anticyclonic easterly wind flow off the laurentide ice sheet in contrast glaciers that existed under relatively warmer and wetter conditions are located along the pacific coast south of oregon where enhanced westerlies delivered higher precipitation than at present between these two groupings lie glaciers that were controlled by a mix of cold and wet conditions attributed to the convergence of cold air from the ice sheet and moisture derived from the westerlies sensitivity tests suggest that for our simulated 18 ka climate many of the glaciers exhibit a variable response to climate but were generally more sensitive to changes in temperature than to changes in precipitation particularly those glaciers in central idaho and the yellowstone plateau our results support arguments that temperature depression generally played a larger role in lowering equilibrium line altitudes in the western u s during the last glacial maximum than did increased precipitation although the magnitude of temperature depression required for steady state mass balance varied from 8 18 c only the sierra nevada glaciers required a substantial increase in precipitation to achieve steady state mass balance while glaciers in the cascade range existed with decreased precipitation

fluid geochemistry contribution to the interpretation of the 2011 2012 unrest of santorini greece in the frame of the dynamics of the aegean volcanic arc

simulation of snow shielding corrections for cosmogenic nuclide surface exposure studies abstract snow cover reduces cosmogenic nuclide production rates in bedrock corrections for snow cover can be more than 10 in mountainous mid latitude regions where many glacial chronologies have been constructed using cosmogenic nuclide surface dating of landforms most published snow corrections use historic climate data of limited duration that are not likely to reflect adequately the full range of snow conditions over the time of exposure we present a model for describing the impact of snow burial on long term exposure histories of landforms the model applies an energy balance approach to snowpack evolution and incorporates both historic and long term climate proxy data attenuation of cosmogenic fast neutrons is modeled alternatively as a simple exponential decrease with increased shielding or as a thin surface layer with constant production followed by an exponential decrease with increasing depth the choice of attenuation model has little effect on the modeled results for the cairngorms but will have a more significant effect in regions characterized by thinner less dense snowpacks spatial variability in snow cover is modeled as a function of elevation only ignoring local variability in snow accumulation as a result of slope aspect wind redistribution and local topography thus model results reveal general spatial and temporal trends in snow shielding effects rather than site specific corrections applications to data from the cairngorm mountains of scotland show that the constant plus exponential cpe production rate depth profile reduces but does not eliminate snow shielding effects under present day conditions snow at 900 m in the cairngorm mountains reduces average production rates by 6 using the cpe profile and 9 with the exponential profile ep long term climate simulations from 15 5 ka through today produce larger snow shielding effects mainly because they predict an increased proportion of precipitation as snowfall during the younger dryas at 900 m this long term simulation reduces average cosmogenic isotope production rates by 12 cpe and 14 ep these results indicate that snow shielding corrections based on historic climate records may be a potential source of systematic error in midlatitude mountainous regions

glacial geology and chronology of bishop creek and vicinity eastern sierra nevada california the valley of bishop creek which drains part of the eastern flank of the sierra nevada california contains an unusually well preserved set of middle to late quaternary moraines these deposits have been mapped by previous investigators but they have not been quantitatively dated we used the accumulation of cosmogenic 36 cl to assign a chronology to the maximal glacial positions mapped in the valley our results indicate that the terminal moraines mapped by previous investigators as tahoe were all deposited between ca 165 and ca 135 ka during marine isotope stage mis 6 moraines mapped as tioga were deposited between 28 and 14 ka during mis 2 these can be subdivided into tioga 1 28 24 ka tioga 3 18 5 17 0 ka and tioga 4 16 0 14 5 ka advances no moraines dated to tioga 2 21 19 ka were found presumably because the tioga 3 advance either overrode or fluvially eroded them at 15 0 14 5 ka the tioga 4 glacier retreated abruptly to the crest of the range this was followed by the brief and fairly minor recess peak advance at ca 13 4 ka no holocene advances extended beyond the very restricted limits of ice during the matthes little ice age advance all preserved terminal moraines at lower elevations were deposited during either the tahoe or tioga stades the tahoe terminal moraines are extensive and voluminous whereas the tioga moraines are relatively narrow and have small volumes however this notable difference may be more a result of idiosyncrasies in the local glacial history than the result of differences in the length or intensity of glaciation between the two glacial episodes the history of glacial advances at bishop creek exhibits a strong correspondence to global climate cycles and to paleoclimate events in the north atlantic in particular

evidence of temperature depression and hydrological variations in the eastern sierra nevada during the younger dryas stade sediment records from two lakes in the east central sierra nevada california provide evidence of cooling and hydrological shifts during the younger dryas stade yd 12 900 11 500 cal yr bp a chironomid transfer function suggests that lake water temperatures were depressed by 2 c to 4 c relative to maximum temperatures during the preceding bolling allerod interstade ba 14 500 12 900 cal yr bp diatom and stable isotope records suggest dry conditions during the latter part of the ba interstade and development of relatively moist conditions during the initiation of the yd stade with a reversion to drier conditions later in the yd these paleohydrological inferences correlate with similar timed changes detected in the adjacent great basin vegetation response during the yd stade includes the development of more open and xeric vegetation toward the end of the yd the new records support linkages between the north atlantic the north pacific and widespread yd cooling in western north america but they also suggest complex hydrological influences shifting hydrological conditions and relatively muted vegetation changes may explain the previous lack of evidence for the yd stade in the sierra nevada and the discordance in some paleohydrological and glacial records of the yd stade from the western united states

latest quaternary north pacific surface water responses imply atmosphere driven climate instability a full sequence of brief interstadials dansgaard oeschger d o cycles are recorded from 60 to 25 ka in santa barbara basin california ocean drilling program hole 893a by planktonic foraminiferal isotopic and assemblage changes at unparalleled high resolution for the oceans synchronous climatic response between north pacific surface waters and the greenland ice sheet during d o cycling is strongly indicated by remarkable similarities in speed magnitude and character of rapid oceanic and atmospheric reorganizations inferred sea surface temperature warmings of as much as 5 c within a few decades and brief warming overshoots of as much as 3 c suggest involvement of an atmospheric amplification top down in situ atmospheric warming of the ocean is implied by differential responses partial decoupling in the changes recorded in surface and thermoclinal waters

late pleistocene glaciations in the northwestern sierra nevada california pleistocene fluvial landforms and riparian ecosystems in central california responded to climate changes in the sierra nevada yet the glacial history of the western sierra remains largely unknown three glacial stages in the northwestern sierra nevada are documented by field mapping and cosmogenic radionuclide surface exposure crse ages two crse ages of erratic boulders on an isolated till above bear valley provide a limiting minimum age of 76 400 3800 10be yr another boulder age provides a limiting minimum age of 48 800 3200 10be yr for a broad crested moraine ridge within bear valley three crse ages producing an average age of 18 600 1180 yr were drawn from two boulders near a sharp crested bouldery lateral moraine that represents an extensive tioga glaciation in bear valley nine crse ages from striated bedrock along a steep valley transect average 14 100 1500 yr and suggest rapid late glacial ice retreat from lower fordyce canyon with no subsequent extensive glaciations these ages are generally consistent with glacial and pluvial records in east central california and nevada

shoreline processes and the age of the lake lahontan highstand in the jessup embayment nevada the well developed shoreline record of pluvial lake lahontan in the jessup embayment nevada is used to refine the history of late pleistocene lake level fluctuations and to assess controls on shoreline development and distribution controls on the strength and type of shorelines developed include local slope the amount and characteristics of sediment available for transport the availability of accommodation space and length of time the lake level resides at a particular shoreline elevation at the sehoo highstand and during the early part of the regression strong storm winds and waves from the south southeast set up a clockwise net shore drift pattern near the head of the embayment although significant differences in local slope geometry of the shoreline and wave energy existed in the embayment crestal heights of constructional shoreline features formed at the highstand vary 2 6 m in elevation and hence provide a relatively precise marker of the highstand elevation radiocarbon dating of a camel bone preserved in high shoreline deposits indicates that the lake reached its highest elevation of 1338 5 m in the embayment and receded from that elevation immediately prior to 13 070 60 yr b p similar and slightly older radiocarbon ages on gastropod shells preserved in barrier deposits at 1327 m 13 280 110 yr b p and 1331 m 13 110 110 yr b p suggest that the final rise to the highstand was very rapid and that the lake maintained its highest stand for a very brief period of time perhaps only for years or decades the brevity of the highstand is reasonable in light of the recent formation of similar barrier features in modern pyramid lake which formed in less than seven months due to a rapid increase in lake level

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

chronology for fluctuations in late pleistocene sierra nevada glaciers and lakes mountain glaciers because of their small size are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in greenland late in the last glacial period are part of global scale climate variability or are restricted to the north atlantic region correlation of cosmogenic chlorine 36 dates on sierra nevada moraines with a continuous radiocarbon dated sediment record from nearby owens lake shows that sierra nevada glacial advances were associated with heinrich events 5 3 2 and 1

development of the truckee river terraces on the northeastern flank of the sierra nevada abstract the distribution and elevation of the abandoned strath terraces along the truckee river in the carson range on the eastern flank of the sierra nevada are mapped and quantified with measurements from lidar accompanied by field survey each mapped strath terrace is formed by incision into the hunter creek sandstone and deposition of fluvial gravel by the truckee river the gravel contains granitic boulders sourced from the glaciated headwaters of the truckee 20 km upstream from the terraces and display boulders ranging from 4 to 12 m in dimension in comparison to the

pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records berin d i owen l a finkel r c clemmens s 2006 pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records quaternary science reviews 25 2729 2748 sponsorship national science foundation grant ear 0207245

in situ weathering rind erosion abstract the use of cosmogenic nuclide dating methods place in doubt the long term future of weathering rinds wrs as a chronometric tool why estimate ages when radiometric control is possible this paper presents evidence that wrs can provide invaluable clues about what particular sample would provide the most accurate cosmogenic age by avoiding inheritance of cosmogenic nuclides and by avoiding boulders undergoing spalling the key to this new use requires testing the occurrence and nature of wr erosion back scattered electron microscopy reveals that ignimbrite andesite basalt and granitic clasts experience wr erosion in all subsurface and surface contexts thus far studied in arizona california hawaii oregon and washington to understand the magnitude of wr erosion we measured wr thicknesses all while controlling the cosmogenic and surface stability ages of clasts by chlorine 36 and rock varnish microlamination dating methods our data reveal that traditional methodologies of sampling cobbles remove two thirds of the true thickness of weathering rinds calling into question many beliefs including the notion that clay minerals are not produced during weathering rind formation comparisons of optical and electron microscope measurements support concerns that measurement of wrs by color changes while useful as a pedagogical tool creates serious biases in underestimating the true dynamics of wrs in the end we found that concordance of wr and rock coating age trends indicates the ideal boulder for cosmogenic nuclide dating offsets reveal either ongoing boulder erosion invalidating zero erosion model ages or a potential problem with inheritance of cosmogenic nuclides

the link between volcanism and tectonics in the southern volcanic zone of the chilean andes a review abstract the nature of the interplay between tectonics and volcanism is a major question in continental margin tectonics the southern andes volcanic zone svz located at the obliquely convergent nazca south america plate margin between 33 s and 46 s offers a unique opportunity to address this question because of along strike changes in crustal thickness tectonic style and well constrained long term and short term kinematic history the complex interaction between tectonic and magmatic processes is evidenced by both the architecture and geochemical signature of volcanic systems main first order factors accounting for the along strike variations in the nature and composition of volcanism are crustal thickness and the existence of a major intra arc fault system the liquine ofqui fault zone lofz second order factors include the local nature of the volcanic arc basement two main categories of volcano tectonic associations have been identified according to the spatial distribution and internal organization of individual volcanoes and clusters of volcanoes with respect to both the overall strike of the volcanic arc and the first and second order active inactive basement faults kinematically coupled associations those that are directly related to the current dextral transpressional tectonic regime include ne trending volcanic alignments of stratovolcanoes and or monogenetic cones kinematically uncoupled associations in which coupling with the current regime is not required include stratovolcanoes built on top of ancient reverse and strike slip faults of the volcanic arc basement and monogenetic cones lying along master faults of the lofz whereas mostly primitive magmas are found in the first category more evolved terms can occur genetically associated with the second category we propose a simplified three dimensional model for the magma plumbing system along and across the svz that integrates kinematically coupled and kinematically uncoupled volcano tectonic associations within the framework of first and second order geological and structural constraints

the hydrothermal system of the calabozos caldera central chilean andes abstract active thermal springs associated with the late pleistocene calabozos caldera complex occur in two groups the colorado group which issues along structures related to caldera collapse and resurgence and the puesto calabozos group a nearby cluster that is chemically distinct and probably unrelated to the colorado springs most of the colorado group can be related to a hypothetical parent water containing 400 ppm cl at 250 c by dilution with 50 of cold meteoric water the thermal springs in the most deeply eroded part of the caldera were derived from the same parent water by boiling the hydrothermal system has probably been active for at least as long as 300 000 years based on geologic evidence and calculations of paleo heat flow there is no evidence for economic mineralization at shallow depth the calabozos hydrothermal system would be an attractive geothermal prospect were its location not so remote

comparison of seismic activity for llaima and villarrica volcanoes prior to and after the maule 2010 earthquake llaima and villarrica are two of the most active volcanoes in the chilean southern volcanic zone and presently show contrasting types of activity llaima is a closed vent edifice with fumarolic activity while villarrica has an open vent with a lava lake continuous degassing and tremor activity this study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 m8 8 maule earthquake which was located in nnw direction from the volcanoes time series for tremors long period and volcano tectonic events were obtained from the catalogue of the volcanic observatory of the southern andes ovdas and from the sfb 574 temporary volcanic network an increase in the amount of tremor activity long period events and degassing rates was observed at villarrica weeks before the mainshock and continued at a high level also after it this increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the maule event in llaima an increase in the volcano tectonic activity was observed directly after the earthquake the simultaneous post earthquake activity at both volcanoes is consistent with a structural adjustment response since this enhanced activity lasted for more than a year we suggest that it is related to a medium term change in the static stress thus the maule earthquake may have affected both volcanoes but did not trigger eruptions from which we assume that none of the volcanoes were in a critical state

a 13 000 year paleolimnological record from the uinta mountains utah inferred from diatoms and loss on ignition analysis paleolimnological research in mountainous regions of the western united states provide baseline understanding of how these lake systems will respond to ongoing climate change fossil diatom assemblage and loss on ignition data were investigated from a 13 000 year lake sediment core from the uinta mountains northeastern utah usa results indicate the presence of three major zones of environmental change 1 from 12 9 10 9 cal ka modern lake formation began temperatures were cool and water was turbid 2 from 10 9 3 5 cal ka conditions were warmer than present and the lake stratified during the summer and 3 beginning approximately 3 5 cal ka temperatures decreased relative to the previous zone and the lake appears to have become increasingly alkaline shifts in diatom taxa relative abundances within the middle zone ca 8 2 6 5 and 5 0 3 5 cal ka are probably caused by precipitation driven decreases in alkalinity and increases in lake depth this record reflects evolution of the lake system and suggests that currently rising temperatures will reduce ice cover and enhance lake stratification and internal nutrient cycling any future changes in precipitation patterns may also impact lake ecology through shifts in alkalinity and or depth

oblique slip tectonics in an active volcanic chain a case study from the southern andes abstract oblique slip tectonics in the intra arc region of the southern andes accommodates heterogeneous deformation derived from plate convergence during the pliocene and quaternary long term mechanical interaction between andean transverse faults i e nw striking sinistral faults and margin parallel faults i e nne striking faults results in linked transtensional fault damage zones that facilitate structural conditions for the migration and emplacement of geofluids in the upper crust we investigated the architecture of pre eruptive units and the nature of faulting at the tatara san pedro pellado volcanic complex in the southern andes here oblique slip faulting crosscuts miocene folded strata and granitoids our main results suggest that quaternary volcanism and an associated geothermal systems developed on top of an ene oriented structural anisotropy defined by hundreds of faults and dikes interacting in a ca 9 km long and 4 km wide rock volume named the tatara damage zone deformation in this domain is characterized by ene to wnw striking transtensional oblique slip faults flanked by 1 the seismically active ns striking dextral melado fault to the west 2 discrete ns to ene striking dextral splay faults to the east and 3 the sinistral nw striking los condores fault to the north east which is reported for the first time in this work the latter fault represents an excellent example of a long lived andean transverse fault furthermore we suggest that the los condores fault accommodates a margin oblique slip component of bulk transpressional deformation we demonstrate that pliocene quaternary intra arc oblique faulting developed after pre late miocene compressional tectonics and that this oblique faulting constrains the geometry of permeable pathways for the flow emplacement and eruption of quaternary geofluids furthermore we evaluated the stress field for a discrete volcanic complex and provided key elements to better understand the role of andean transverse faults in the spatial organization of quaternary arc volcanism and geothermal systems in the southern andes

latest pleistocene to holocene hydroclimates from lake elsinore california abstract the hydroclimate of the southwestern united states us region changed abruptly during the latest pleistocene as the continental ice sheets over north america retreated from their most southerly extent to investigate the nature of this change we present a new record from lake elsinore located 36 km inland from the pacific ocean in southern california and evaluate it in the context of records across the coastal and interior southwest united states including northwest mexico the sediment core recovered from lake elsinore provides a continuous sequence with multi decadal resolution spanning 19 9 ka bp sedimentological and geochemical analyses reveal hydrologic variability in particular sand and carbonate components indicate abrupt changes at the oldest dryas od bolling allerod ba and younger dryas yd transitions consistent with the timing in greenland hydrogen isotope analyses of the c28 n alkanoic acids from plant leaf waxes dwax reveal a long term trend toward less negative values across 19 9 ka bp dwax values during the od suggest a north pacific moisture source for precipitation consistent with the dipping westerlies hypothesis we find no isotopic evidence for the north american monsoon reaching as far west as lake elsinore therefore we infer that wet dry changes in the coastal southwest were expressed through winter season precipitation consistent with modern climatology comparing lake elsinore to other southwest records notably cave of bells and fort stanton we find coincident timing of the major transitions od to ba ba to yd and hydrologic responses during the od and ba the hydrologic response however varied during the yd consistent with a dipole between the coastal and interior southwest the coherent pattern of hydrologic responses across the interior southwest us and northwest mexico during the od wet the ba drier and yd wet follows changes in the atlantic meridional overturning circulation presumably via its combined influence on north pacific winter storm tracks and the extent magnitude of the north american monsoon in contrast lake elsinore and the coastal southwest experiences a deglacial drying trend punctuated by abrupt change at the od to ba and ba to yd transitions this trend tracks rising greenhouse gases through the deglacial with an apparent southward shift in westerly moisture sources adjusting to the retreating ice sheet

influence of rock mass strength on the erosion rate of alpine cliffs collapse of cliff faces by rockfall is a primary mode of bedrock erosion in alpine environments and exerts a first order control on the morphologic development of these landscapes in this work we investigate the influence of rock mass strength on the retreat rate of alpine cliffs to quantify rockwall competence we employed the slope mass rating smr geomechanical strength index a metric that combines numerous factors contributing to the strength of a rock mass the magnitude of cliff retreat was calculated by estimating the volume of talus at the toe of each rockwall and projecting that material back on to the cliff face while accounting for the loss of production area as talus buries the base of the wall selecting sites within basins swept clean by advancing last glacial maximum lgm glaciers allowed us to estimate the time period over which talus accumulation occurred i e the production time dividing the magnitude of normal cliff retreat by the production time we calculated recession rates for each site our study area included a portion of the sierra nevada between yosemite national park and lake tahoe rockwall recession rates determined for 40 alpine cliffs in this region range from 0 02 to 1 22 mm year with an average value of 0 28 mm year we found good correlation between rockwall recession rate and smr which is best characterized by an exponential decrease in erosion rate with increasing rock mass strength analysis of the individual components of the smr reveals that joint orientation with respect to the cliff face is the most important parameter affecting the rockwall erosion rate the complete smr score however best synthesizes the lithologic variables that contribute to the strength and erodibility of these rock slopes our data reveal no strong independent correlations between rockwall retreat rate and topographic attributes such as elevation aspect or slope angle copyright 2009 john wiley sons ltd

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

downstream patterns of bed material grain size in a large lowland alluvial river subject to low sediment supply 1 a new data set of bimodal subaqueous channel bed sediments was analyzed for longitudinal patterns in grain size it yielded two interesting observations 1 separate fining trends in d50 exist for gravel and fines that overlap for 175 river kilometers and 2 this overlap in fining trends results in a protracted nonabrupt gravel to sand transition these suggest bed patchiness that is interpreted in the context of inherent grain size bimodality localized hydraulic sorting due to spatially heterogeneous and low sediment supply and local deviations in channel gradient the data also show that tributaries have a minor impact on main stem downstream fining due to basin shape and tectonic history in addition subaqueous channel sediments were observed to be finer than nearby sediments collected from exposed bars which may indicate a narrow active zone of transport where bars are disconnected from sediment movement this research has implications for bed material collection and theories of downstream fining

an investigation of the accuracy of coulomb stress changes inferred from geodetic observations following subduction zone earthquakes earthquake clustering along plate boundaries suggests that earthquakes may interact and static coulomb stress change csc is commonly invoked as one possible mechanism for stress transfer between earthquakes and nearby faults previous work has addressed the precision of csc predictions that are influenced by observational noise inversion regularization and simplified modeling assumptions here we address the accuracy of csc predictions informed by geodetic observations in subduction zones where inversion model resolution is poor we conduct synthetic tests to quantify the degree to which the sign and magnitude of csc can be reliably inferred from slip distributions inverted from various geodetic observations insar gps seafloor observations we find that in an idealized subduction zone csc can only be confidently inferred for receiver faults far 10s of km from the earthquake source though this distance shortens with the addition of synthetic seafloor observations we apply this methodology to the 2010 mw8 8 maule earthquake and identify 13 aftershocks from a population of 475 documented events for which we can confidently resolve co seismic stress changes these results demonstrate that the low model resolution of fault slip inversions in subduction zones limits our ability to address fundamental questions about earthquake sources and stress interactions nonetheless our results highlight that stress change predictions are considerably more accurate after the introduction of seafloor geodetic observations additionally we show that insar observations are not required to substantially improve stress change approximations in regions where gps may be the only viable observation such as in island arcs settings

triggering of volcanic eruptions although earthquakes and volcanic eruptions are each manifestations of large scale tectonic plate and mantle motions it is usually thought that the occurrences of these events are not directly related there have been some studies however in which triggering of volcanic eruptions by earthquakes remote from the volcano has been proposed1 2 the 1992 landers southern california earthquake caused triggered seismicity at very large distances3 including the magmatically active4 long valley caldera region which also experienced a significant coincident deformation transient5 motivated by this demonstration of the ability of a distant earthquake to disturb a volcanic system and the earlier studies of specific cases of eruption triggering we examine here the historical record of eruptions and earthquakes to see if there are indeed significantly more eruptions immediately following large earthquakes we find that within a day or two of large earthquakes there are many more eruptions within a range of 750 km than would otherwise be expected additionally it is well known6 that volcanoes separated by hundreds of kilometres frequently erupt in unison the characteristics of such eruption pairs are also consistent with the hypothesis that the second eruption is triggered by earthquakes associated with the first

the origin of the loncopue trough in the retroarc of the southern central andes from field geophysical and geochemical data abstract this work analyzes through field geophysical geochemical and geochronological data a particular setting of the southern andes in which an extensional system is flanking the mountain front this setting is represented by the loncopue trough whose origin is discussed for this part of the andes this work reconstructs 3 dimensionally the structure of this basin and its evolution through time since jurassic times as a series of isolated depocenters to late cretaceous eocene times with the construction of a positive relief that subsequently was relaxed through two extensional stages during the late oligocene early miocene and the pliocene quaternary respectively the last episode of extension is characterized by an initial stage with a series of caldera collapses in the latest pliocene early quaternary this passed to a stage of development of a broad basaltic plateau in pre and inter glacial times circumscribed with new radiometric data to the pleistocene quaternary products in northern and central loncopue trough have chemical relations that are intermediate between the arc front and the southern loncopue trough volcanic rocks studied in previous works thus retroarc eruptions would be part of an extended arc configuration that goes from typical arc series in the northern part of the trough to within plate series in the south low elastic thicknesses computed from gravity data in this work correlate with the area of retroarc volcanic activity magnetic data have allowed determining the curie isotherm showing two areas of relatively abnormal heat flow one along the loncopue trough itself and the other in the foreland zone this scenario is discussed through three main hypotheses an occurrence linked to a slab steepening after a shallow subduction in the area co seismic crustal stretching linked to giant earthquakes in the subduction zone and finally slab tearing associated with asthenospheric upwelling

deglaciation chronology and paleoclimate of the pieciu stawow polskich roztoki valley high tatra mountains western carpathians since the last glacial maximum inferred from 36cl exposure dating and glacier climate modelling abstract exposure dating of abraded bedrock surfaces below glacial trimlines in the pieciu stawow polskich roztoki valley using cosmogenic 36 cl has been applied to determine the deglaciation chronology in the study area nineteen rock samples yielded ages between 21 5 and 9 5 ka the spatial distribution of ages provides evidence of progressive downwasting of glaciers within the study area dates of exposure indicate that the onset of ice volume decrease occurred no later than 21 5 ka this provides evidence that the local maximum glaciation occurred in accordance with the global last glacial maximum lgm the first period of deglaciation in the study area was completed around 18 ka further significant loss of ice volume is confirmed between 15 and 13 ka the spatial distribution of chronological data within the pieciu stawow polskich valley indicates post lgm readvances of glaciers around 17 ka and 12 ka using the glacier modelling and paleoclimate proxies from the study area the early late glacial glacier had been stable with a 9 10 c decrease in temperature and 30 50 lower precipitation in relation to modern conditions the subsequent advance took place with temperatures 6 7 c lower and 10 30 less precipitation the timing of the readvances is nearly synchronous with late glacial advances in the european alps southern carpathians and anatolian peninsula this suggests synchronicity of major climatic fluctuations across central europe and the northern margin of the mediterranean basin

geomorphology and quaternary stratigraphy the roles of morpho litho and allostratigraphy abstract the subdivision and ordering of quaternary sediments and landforms is very often based on geomorphology quaternary landforms such as moraines river terraces palaeoshorelines and indeed any other landform can be arranged and ordered in time based on their relative position in the landscape morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form whilst surface form is often used as a criterion for separating sedimentary units morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision and morpho and lithostratigraphy are often interlinked in quaternary science however another approach allostratigraphy has increasingly been applied to subdivide and order quaternary sediment landforms allostratigraphy uses discontinuities to subdivide sedimentary successions allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit furthermore it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities this paper examines the applications of morpho litho and allostratigraphy to subdivide sediment landform assemblages and critically reviews their role in quaternary stratigraphy

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

cosmogenic 36cl accumulation in unstable landforms 2 simulations and measurements on eroding moraines cosmogenic 36cl surface exposure ages obtained for multiple boulders from single landforms are usually characterized by a variance larger than that of the analytical methods employed this excessive boulder to boulder variability progressively more profound with increasing age of landforms is due to removal of soil and gradual exposure of boulders at the surface in our gradual exposure model boulders are initially buried in moraine matrix with time erosion lowers the moraine surface and the boulders are gradually exposed to cosmic rays because the cosmic ray intensity changes with depth the boulders are subjected to variable production rates of the cosmogenic 36cl initial depth of boulders and their chemical composition are variable which results in different amounts of the accumulated cosmogenic 36cl and thus different apparent ages of boulders the shape of the resulting distribution of the apparent ages and the coefficient of variation depend on the erosion depth while the first moment is a function of the true surface age and the erosion depth these properties of the apparent age distributions permit calculation of the surface age the erosion depth and also the average erosion rate we tested the model calculations using 26 boulders from a late pleistocene moraine at bishop creek sierra nevada california the set exhibited a bimodal distribution of the 36cl surface exposure ages we interpreted the older mode as the result of gradual exposure and the younger one as the result of surficial processes other than soil removal the 10 samples that constitute the older mode produced a distribution which closely matches the modeled distribution calculated using an age of 85 kyr and erosion depth of 570 g cm 2 this age is the same as an independent estimate obtained from cation ratio studies and the calculated erosion depth is very close to the erosion depth of 600 g cm 2 based on a simple analytical model of soil erosion these results indicate that our statistical model adequately describes effects of soil erosion on accumulation of cosmogenic 36cl the approach can be used to simultaneously obtain the true landform age and the erosion rate from apparent 36cl ages and thereifore may help in evaluation of surface exposure ages of eroding landforms

earthquake induced thermal anomalies at active volcanoes answering the question whether a regional earthquake can trigger or enhance volcanic activity requires a systematic measure of volcanic activity one such measure is heat fl ux the availability since a d 2000 of a satellite derived heat fl ux inventory for global volcanism allows us to explore how earthquakes and volcanic activity may be linked examination of 7 yr of global volcanic heat fl ux data reveals 37 volcanic responses to regional earthquakes each response is expressed by an increase in heat fl ux within 1 21 days of the triggering earthquake whether a volcano responds depends on earthquake magnitude distance to the epicenter and orientation of the earthquake focal mechanism in respect to the volcano the focal mechanism has to align with the responding system of the 7 global major increases of seismic energy during 2000 2006 4 were followed by a global volcanic heat fl ux increase the largest response involved a 300 increase and followed the largest earthquake in the period the 2004 sumatraandaman indonesia earthquake moment magnitude m w 9 3

subsidence at southern andes volcanoes induced by the 2010 maule chile earthquake large earthquakes in subduction zones can affect nearby volcanoes analysis of ground deformation following the 2010 earthquake in maule chile shows that some volcanoes subsided by up to 15 cm probably because of quake triggered release of hydrothermal fluids

can compliant fault zones be used to measure absolute stresses in the upper crust 1 geodetic and seismic observations reveal long lived zones with reduced elastic moduli along active crustal faults these fault zones localize strain from nearby earthquakes consistent with the response of a compliant elastic layer fault zone trapped wave studies documented a small reduction in p and s wave velocities along the johnson valley fault caused by the 1999 hector mine earthquake this reduction presumably perturbed a permanent compliant structure associated with the fault the inferred changes in the fault zone compliance may produce a measurable deformation in response to background tectonic stresses this deformation should have the same sense as the background stress rather than the coseismic stress change here we investigate how the observed deformation of compliant zones in the mojave desert can be used to constrain the fault zone structure and stresses in the upper crust we find that gravitational contraction of the coseismically softened zones should cause centimeters of coseismic subsidence of both the compliant zones and the surrounding region unless the compliant fault zones are shallow and narrow or essentially incompressible we prefer the latter interpretation because profiles of line of sight displacements across compliant zones cannot be fit by a narrow shallow compliant zone strain of the camp rock and pinto mountain fault zones during the hector mine and landers earthquakes suggests that background deviatoric stresses are broadly consistent with mohr coulomb theory in the mojave upper crust with 0 7 large uncertainties in mojave compliant zone properties and geometry preclude more precise estimates of crustal stresses in this region with improved imaging of the geometry and elastic properties of compliant zones and with precise measurements of their strain in response to future earthquakes the modeling approach we describe here may eventually provide robust estimates of absolute crustal stress

the use of in situ produced cosmogenic radionuclides in glaciology and glacial geomorphology the usefulness of in situ produced cosmogenic radionuclides in constraining glacial chronologies through exposure age dating has been demonstrated in numerous studies however an understanding of cosmogenic radionuclide techniques and their uncertainties opens up a wide range of other potential applications in glaciology and glacial geomorphology recently developed applications include estimation of spatial and temporal variations in the depth of glacial erosion from cosmogenic radionuclide inheritance which provides important constraints on process based erosion models and burial dating which can provide chronological control for glacial advances and the onset of till deposition an interesting new application currently at the level of theoretical model development concerns the unraveling of complex exposure and burial histories overall in situ produced cosmogenic radionuclide techniques provide a means with which to constrain a wide range of ice sheet and glacial models over time scales of a thousand to a few million years

a review of new zealand palaeoclimate from the last interglacial to the global last glacial maximum abstract results from terrestrial and marine palaeoclimate proxies are integrated to reconstruct palaeoclimate variations in new zealand from the last interglacial to the global last glacial maximum glgm by combining data from 21 speleothems we have constructed composite o c stable isotope sequences from 0 to 88 5 ka bp and from 107 8 to 128 2 ka bp the gaps in the sequence a 19 3 ka break in coverage in mis 5b c and a 2 97 ka gap in mis 5a preclude the construct of a continuous record so data were referenced to a common scale by normalising individual records subtracting means and dividing by standard deviation overlapping records were then merged chronologically these records were compared to integrated summer insolation for 45 s and to terrestrial and marine environmental proxies available for the new zealand region the mis 5e thermal maximum in new zealand was around 128 122 kiloyears bp ka bp and therefore similar in timing to the last interglacial in australia southern europe and greenland temperatures in parts of the north island may have been 2 3 c warmer than present and the sea rose 3 6 m above modern level in mis 5d and 5b cool conditions with glacial advances occurred in the south island but from about 87 to 73 ka in mis 5a warmth within 2 c of present characterised most of the interstadial locally termed the otamangakau interstadial conditions then cooled rapidly and culminated in a mis 4 glacial advance that was the greatest of the new zealand last glacial cycle nzlgm the climate was cool to cold and while wet in westerly windward locations may have been dry in the east combined australian and new zealand evidence suggests glacial culmination around 67 62 ka this regional lgm coincided with severe cooling in europe during mis 3 conditions were very variable the climate in eastern north island hawke bay and the bay of plenty at the start of mis 3 was similar to the holocene and the period 61 43 ka was relatively mild overall and is termed the aurora interstadial although it contained a short interval of mountain glacier expansion around 49 47 ka after 43 ka conditions cooled again with a glacial advance from 42 to 38 ka before a return to milder but still cool conditions during the moerangi interstadial from 37 to 31 ka after this conditions deteriorated at the lead in to the glgm the maximum glacial advance occurred in late mis 3 between 31 and 29 ka the glacial onset was abrupt with te anau glacier in fiordland one of the largest in the southern alps taking only about 2000 years to achieve its maximum glgm depth probably because conditions were wet as well as cold but stable isotope data suggest that the climate then became drier while remaining cold and the glacier progressively ablated such that its surface had lowered 390 m by the start of mis 2 and by 600 m by ca 18 ka the glgm maximum in new zealand may have led the terrestrial ice sheet lgm in the northern hemisphere by a few thousand years possibly because alpine glaciers respond more rapidly to climate change than continental ice sheets the culmination of the glgm in nz occurred in mis 3 about 12 000 years before global ice volume reached its peak as determined by the marine stable isotope record the marine glgm by the time global ice volume was at a maximum 19 ka glaciers had almost disappeared from major fiordland valleys in new zealand whereas polar ice sheet records have revealed a bi polar see saw this is not so evident in the mid latitudes because some temperate zone inter hemispheric climate events coincide closely in time perhaps the see saw effect diminishes with distance from the poles

continuous lake sediment records of glaciation in the sierra nevada between 52 600 and 12 50014c yr b p the chemistry of the carbonate free clay size fraction of owens lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial interstadial oscillations owens lake records of total organic carbon magnetic susceptibility and chemical composition of the carbonate free clay size fraction indicate that tioga glaciation began 24 500 and ended by 13 60014c yr b p many of the components of glacial rock flour e g tio2 mno bao found in owens lake sediments achieved maximum values during the tioga glaciation when valley glaciers reached their greatest extent total organic carbon and sio2 amorphous concentrations reached minimum values during tioga glaciation resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of owens lake at least 20 stadial interstadial oscillations occurred in the sierra nevada between 52 600 and 14 00014c yr b p total organic carbon data from a pyramid lake sediment core also indicate oscillations in glacier activity between 39 500 and 13 60014c yr b p alpine glacier oscillations occurred on a frequency of 1900 yr in both basins suggesting that millennial scale oscillations occurred in california and nevada during most of the past 52 600 yr

the 2010 mw 8 8 maule megathrust earthquake of central chile monitored by gps large earthquakes produce crustal deformation that can be quantified by geodetic measurements allowing for the determination of the slip distribution on the fault we used data from global positioning system gps networks in central chile to infer the static deformation and the kinematics of the 2010 moment magnitude m w 8 8 maule megathrust earthquake from elastic modeling we found a total rupture length of 500 kilometers where slip up to 15 meters concentrated on two main asperities situated on both sides of the epicenter we found that rupture reached shallow depths probably extending up to the trench resolvable afterslip occurred in regions of low coseismic slip the low frequency hypocenter is relocated 40 kilometers southwest of initial estimates rupture propagated bilaterally at about 3 1 kilometers per second with possible but not fully resolved velocity variations

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

nearly synchronous climate change in the northern hemisphere during the last glacial termination the climate of the north atlantic region underwent a series of abrupt cold warm oscillations when the ice sheets of the northern hemisphere retreated during the last glacial termination 17 7 11 5kyr ago evidence for these oscillations which are recorded in european terrestrial sediments as the oldest dryas bolling older dryas allerod younger dryas vegetational sequence1 2 has been found in greenland ice cores3 4 the geographical extent of many of these oscillations is not well known5 6 but the last major cold event the younger dryas seems to have been global in extent7 8 9 10 here we present evidence of four major oscillations in the hydrological balance of the owens basin california that occurred during the last glacial termination dry events in western north america occurred at approximately the same time as cold events recorded in greenland ice with transitions between climate regimes in the two regions taking place within a few hundred years of each other our observations thus support recent climate simulations which indicate that cooling of the north atlantic ocean results in cooling of the north pacific ocean11 which in turn leads to a drier climate in western north america12

poroelastic rebound along the landers 1992 earthquake surface rupture maps of surface displacement following the 1992 landers california earthquake generated by interferometric processing of ers 1 synthetic aperture radar sar images reveal effects of various postseismic deformation processes along the 1992 surface rupture the large scale pattern of the postseismic displacement field includes large lobes mostly visible on the west side of the fault comparable in shape with the lobes observed in the coseismic displacement field this pattern and the steep displacement gradient observed near the emerson camp rock fault cannot be simply explained by afterslip on deep sections of the 1992 rupture models show that horizontal slip occurring on a buried dislocation in a poisson s material produces a characteristic quadripole pattern in the surface displacement field with several centimeters of vertical motion at distances of 10 20 km from the fault yet this pattern is not observed in the postseismic interferograms as previously proposed to explain local strain in the fault step overs peltzer et al 1996b we argue that poroelastic rebound caused by pore fluid flow may also occur over greater distances from the fault compensating the vertical ground shift produced by fault afterslip such a rebound is explained by the gradual change of the crustal rocks poisson s ratio value from undrained coseismic to drained postseismic conditions as pore pressure gradients produced by the earthquake dissipate using the poisson s ratio values of 0 27 and 0 31 for the drained and undrained crustal rocks respectively elastic dislocation models show that the combined contributions of afterslip on deep sections of the fault and poroelastic rebound can account for the range change observed in the sar data and the horizontal displacement measured at global positioning system gps sites along a 60 km long transect across the emerson fault savage and svarc 1997 using a detailed surface slip distribution on the homestead valley kickapoo and johnson valley faults we modeled the poroelastic rebound in the homestead valley pull apart a poisson s ratio value of 0 35 for the undrained gouge rocks in the fault zone is required to account for the observed surface uplift in the 3 5 years following the earthquake this large value implies a seismic velocity ratio vp vs of 2 1 consistent with the observed low vs values of fault zone guided waves at shallow depth li et al 1997 the sar data also reveal postseismic creep along shallow patches of the eureka peak and burnt mountain faults with a characteristic decay time of 0 8 years coseismic dilatant hardening locking process followed by post seismic pore pressure controlled fault creep provide a plausible mechanism to account for the decay time of the observed slip rate along this section of the fault

coulomb stress perturbation after great earthquakes in the sumatran subduction zone potential impacts in the surrounding region abstract the sumatran subduction zone has been seismically very active compared with other major subduction zones in the world since 2004 a sequence of large earthquakes ruptured along the trench including the 2004 mw 9 2 sumatra andaman the 2005 mw 8 6 nias simeulue the 2007 mw 8 4 bengkulu the 2010 mw 7 8 mentawai tsunami earthquakes and numerous moderate and small events these earthquakes released stress over tens of seconds to minutes disturbing the lithosphere and asthenosphere across a broad region as earthquake introduced stress disturbance can trigger tremendous aftershocks and sometimes precipitate large earthquakes in their vicinity gaining a detailed picture of spatial and temporal stress evolution on the fault and its neighboring faults is crucial for seismic forecasting here we have developed spatiotemporal coulomb stress models for the sumatran region which includes the sumatran subduction zone and the sumatran fault using a well studied postseismic model this postseismic model is constrained by decade long time series of geodetic observations from the sumatran gps array sugar and from tide gauge data in southeast asia we show that coulomb stress changes imparted by co and post seismic processes of previous great ruptures could well explain the temporal and spatial connection between seismicity and stress evolution most importantly our results reveal that the stress in the mentawai seismic gap of the sumatran subduction zone was loaded by more than two bars these stress perturbations could potentially trigger the rupture of the mentawai seismic gap which was already overdue in the last seismic cycle now the likelihood for the failure of this gap is even higher than before 2004 we also find that along the sumatran fault stress has increased to more than one bar which may explain the surrounding seismicity consequently we highlight the considerable seismic hazard and associated tsunami threat to the neighboring regions

chronology of glaciations in the sierra nevada california from 10be surface exposure dating abstract we use 10 be surface exposure dating to construct a high resolution chronology of glacial fluctuations in the sierra nevada california most previous studies focused on individual glaciated valleys whereas our study compares chronologies developed throughout the range to identify regional patterns in the timing of glacier response to major climate changes sites throughout the range indicate last glacial maximum retreat at 18 8 1 9 ka 2 that suggests rather consistent changes in atmospheric variables e g temperature and precipitation throughout the range the penultimate glacial retreat occurred at ca 145 ka our data suggest that the sierra nevada landscape is dominated by glacial features deposited during marine isotope stage mis 2 and mis 6 deposits of previously recognized glaciations between circa 25 and 140 ka e g mis 4 tenaya early tahoe cannot be unequivocally identified the timing of sierra nevada glacial retreat correlates well with other regional paleoclimate proxies in the sierra nevada but differs significantly from paleoclimate proxies in other regions our dating results indicate that the onset of lgm retreat occurred several thousand years earlier in the sierra nevada than some glacial records in the western us

diversion of the upper bear river glacial diffluence and quaternary erosion sierra nevada california abstract deep canyon erosion and diversion of more than 300 km 2 of the former upper bear river is documented with stratigraphic and morphologic evidence stratigraphic relationships constrain canyon incision to no older than late miocene in age a hypothesis is advanced that channel diversion was caused by ice spilling over a divide between the bear and south yuba drainages leading to development of glacial diffluence and deep incision the local glacial stratigraphy is mapped based on lateral moraines erratics and striae which indicate that at least two and probably three glacial advances occupied both south yuba and bear valleys stratigraphic relationships constrain most valley incision to before the last major glacial stage and probably by the end of an earlier larger glacial advance morphologic evidence supports a hypothesis of dominantly sub glacial erosion at an outlet glacier through the yuba gorge where steep valley gradients high shear stresses and large meltwater discharges led to rapid erosion and formation of a deep v shaped valley

glacial erosion and geomorphology in the northwest sierra nevada ca pleistocene glacial erosion left a strong topographic imprint in the northwestern sierra nevada at many scales yet the specific landforms and the processes that created them have not been previously documented in the region in contrast glaciation in the southern and central sierra was extensively studied and by the end of the 19th century was among the best understood examples of alpine glaciation outside of the european alps this study describes glacially eroded features in the northwest sierra and presents inferred linkages between erosional forms and pleistocene glacial processes many relationships corroborate theoretical geomorphic principles these include the occurrence of whalebacks in deep ice positions roches moutonnees under thin ice and occurrence of p forms in low topographic positions where high subglacial meltwater pressures were likely some of the landforms described here have not previously been noted in the sierra including a large crag and tail eroded by shallow ice and erosional benches high on valley walls thought to be cut by ice marginal channels

climatic and hydrologic oscillations in the owens lake basin and adjacent sierra nevada california oxygen isotope and total inorganic carbon values of cored sediments from the owens lake basin california indicate that owens lake overflowed most of the time between 52 500 and 12 500 carbon 14 14 c years before present b p owens lake desiccated during or after heinrich event h1 and was hydrologically closed during heinrich event h2 the magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 sierra nevada glaciations occurred between 52 500 and 23 500 14 c years b p most of the glacial advances were accompanied by decreases in the amount of discharge reaching owens lake comparison of the timing of glaciation with the lithic record of north atlantic core v23 81 indicates that the number of mountain glacial cycles and the number of north atlantic lithic events were about equal between 39 000 and 23 500 14 c years b p

cosmogenic chlorine 36 chronology for glacial deposits at bloody canyon eastern sierra nevada deposits from mountain glaciers provide an important record of quaternary climatic fluctuations but have proved difficult to date directly a chronology has been obtained for glacial deposits at bloody canyon california by measurement ofthe accumulation of chlorine 36 produced by cosmic rays in boulders exposed on moraine crests the accumulation ofchlorine 36 indicates that episodes of glaciation occurred at about 21 24 65 115 145 and 200 ka thousand years ago although the timing of the glaciations correlates well with peaks of global ice volume inferred from the marine oxygen isotope record the relative magnitudes differ markedly the lengths of the moraines dating from 115 ka and 65 ka show that the early glacial episodes were more extensive than those during the later wisconsin and indicate that the transition from interglacial to full glacial conditions was rapid

airborne lidar analysis and geochronology of faulted glacial moraines in the tahoe sierra frontal fault zone reveal substantial seismic hazards in the lake tahoe region california nevada usa we integrated high resolution bare earth airborne light detection and ranging lidar imagery with field observations and modern geochronology to characterize the tahoe sierra frontal fault zone which forms the neotectonic boundary between the sierra nevada and the basin and range province west of lake tahoe the lidar imagery clearly delineates active normal faults that have displaced late pleistocene glacial moraines and holocene alluvium along 30 km of linear right stepping range front of the tahoe sierra frontal fault zone herein we illustrate and describe the tectonic geomorphology of faulted lateral moraines we have developed new three dimensional modeling techniques that utilize the high resolution lidar data to determine tectonic displacements of moraine crests and alluvium the statistically robust displacement models combined with new ages of the displaced tioga 20 8 1 4 ka and tahoe 69 2 4 8 ka 73 2 8 7 ka moraines are used to estimate the minimum vertical separation rate at 17 sites along the tahoe sierra frontal fault zone near the northern end of the study area the minimum vertical separation rate is 1 5 0 4 mm yr which represents a two to threefold increase in estimates of seismic moment for the lake tahoe basin from this study we conclude that potential earthquake moment magnitudes m w range from 6 3 0 25 to 6 9 0 25 a close spatial association of landslides and active faults suggests that landslides have been seismically triggered our study underscores that the tahoe sierra frontal fault zone poses substantial seismic and landslide hazards

limited overlap between the seismic gap and coseismic slip of the great 2010 chile earthquake the mw 8 8 chile earthquake on 27 february 2010 occurred in a broad region where tectonic loading has been accumulating since the great 1835 earthquake a joint inversion of tsunami and geodetic data suggests that the 2010 earthquake rupture only partly overlapped with the zone of preseismic locking

a self sustaining climate mode in the tropical atlantic 1995 97 observations and modelling an anomalous climatic event in the tropical atlantic starting in autumn 1995 and continuing into the autumn of 1997 is investigated using remotely sensed datasets and a reduced gravity model it is shown that this event contained both a warm and a cold phase each of roughly 12 months duration the propagating signal within each phase is identified in the sea surface height and temperature signatures as both equatorial and off equatorial waves in the ocean with coupling to atmospheric convection the strength geographical pattern and timing of the anomalous period is consistent with it being the first observed example of a coupled mode of interaction between the ocean and atmosphere found in two previous coupled ocean atmosphere models of the tropics this interpretation means that the two phased climate event which we will call the equatorial atlantic oscillation eao was associated with purely internal atmospheric and oceanographic variability within the atlantic basin and hence was independent of the pacific climate it can also be inferred from long term monthly sea surface temperature and sea level pressure datasets that there were potentially several previous eao events during the past century

updated cosmogenic chronologies of pleistocene mountain glaciation in the western united states and associated paleoclimate inferences abstract surface exposure dating with terrestrial cosmogenic nuclides tcns has become the primary method for determining numerical ages of pleistocene mountain glacial deposits and landforms in the conterminous western united states u s and in numerous other glaciated settings worldwide recent updates to models of tcn production and scaling warrant a reconsideration of published exposure ages of moraines of the last two pleistocene glaciations and associated paleoclimate inferences previously reported tcn exposure ages of moraines are recalculated here using newer production rates and scaling models for nuclides helium 3 3he beryllium 10 10be aluminum 26 26al and chlorine 36 36cl in most cases yielding significant differences from originally reported ages recalculated tcn exposure ages of moraines of the penultimate glaciation display a high degree of variability for individual landforms particularly toward the younger end of age distributions suggesting that exposure history is affected by moraine denudation and that older age modes provide the best estimate of the depositional age of these moraines oldest exposure ages of penultimate glaciation moraines are well aligned among mountain ranges across the western u s and yield a mean of 138 13 ka indicating that mountain glaciation occurred in step with global ice volume maxima during marine oxygen isotope stage 6 on average terminal moraines of the last glaciation date to 19 5 2 3 ka and correspond to the latter part of the global last glacial maximum lgm down valley recessional moraines representing prolonged glacial stabilizations or readvances to 75 of maximum lengths have a mean exposure age of 17 0 1 8 ka suggesting that these moraine positions were last occupied during heinrich stadial 1 evidence for multiple glacial culminations during the last glaciation is found in several mountain ranges and likely reflects at least two phases of late pleistocene climate an earlier phase when glaciers attained their maximum length in response to cooling during the lgm and a later phase when glaciers persisted at or readvanced to near maximum lengths in response to sustained cold temperatures and or increased precipitation

eruption age of a 100 000 year old basalt from 40 ar 39 ar analysis of partially degassed xenoliths we have applied 40 ar 39 ar dating using stepwise thermal extraction of ar to five potassium rich granitic xenoliths and their host basalt from sawmill canyon in the sierra nevada california previous k ar analyses showed the age of the basalt to be roughly 100 000 years or less the xenoliths which had accumulated large amounts of radiogenic 40 ar since their crystallization 100 m y ago were partially degassed upon their inclusion in the basaltic magma ar released from the xenoliths in the laboratory at temperatures substantially below the melting temperature of the basalt was created since the host magma cooled isotopic compositions of ar released from the xenoliths in several extraction steps at temperatures below 900 c were colinear in 36 ar 40 ar versus 39 ar 40 ar diagrams and defined isochrons giving a mean age of degassing of 119 000 7000 2 years 40 ar extracted at higher temperatures included ancient radiogenic 40 ar that was never diffused from the xenoliths during immersion in the magma this 40 ar caused an increase in the apparent age for the high temperature extractions the high precision of the eruption age determined by this method is comparable to that obtained elsewhere by conventional k ar dating of sanidine 40 ar 39 ar analysis of granitic xenoliths to date young basaltic lava flows may prove to yield results superior to those found from analysis of the lava itself establishing the age of eruption of the basalt flow in sawmill canyon establishes age limits for two sierran glaciations which left moraines stratigraphically above and below the lava thus the younger glaciation must be wisconsin the older must be pre wisconsin in age

conceptual model of sediment processes in the upper yuba river watershed sierra nevada ca this study examines the development of a conceptual model of sediment processes in the upper yuba river watershed and we hypothesize how components of the conceptual model may be spatially distributed using a geographical information system gis the conceptual model illustrates key processes controlling sediment dynamics in the upper yuba river watershed and was tested and revised using field measurements aerial photography and low elevation videography field reconnaissance included mass wasting and channel storage inventories assessment of annual channel change in upland tributaries and evaluation of the relative importance of sediment sources and transport processes hillslope erosion rates throughout the study area are relatively low when compared to more rapidly eroding landscapes such as the pacific northwest and notable hillslope sediment sources include highly erodible andesitic mudflows serpentinized ultramafics and unvegetated hydraulic mine pits mass wasting dominates surface erosion on the hillslopes however erosion of stored channel sediment is the primary contributor to annual sediment yield we used gis to spatially distribute the components of the conceptual model and created hillslope erosion potential and channel storage models the gis models exemplify the conceptual model in that landscapes with low potential evapotranspiration sparse vegetation steep slopes erodible geology and soils and high road densities display the greatest hillslope erosion potential and channel storage increases with increasing stream order in channel storage in upland tributaries impacted by hydraulic mining is an exception reworking of stored hydraulic mining sediment in low order tributaries continues to elevate upper yuba river sediment yields finally we propose that spatially distributing the components of a conceptual model in a gis framework provides a guide for developing more detailed sediment budgets or numerical models making it an inexpensive way to develop a roadmap for understanding sediment dynamics at a watershed scale published by elsevier b v

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

timing and significance of late glacial and holocene cirque glaciation in the sierra nevada california mapping and radiocarbon dates of cirque moraines in the sierra nevada demonstrate that the last significant pre little ice age glacier advance in the range the recess peak resulted from snowline lowering roughly twice that of the matthes little ice age advance and that the recess peak advance is late pleistocene in age we mapped recess peak and matthes deposits in 64 cirques along a profile of the main sierran crest that spans the north south limits of neoglacial deposits in the range equilibrium line altitudes for the reconstructed recess peak glaciers vary greatly but coherently with those of the matthes advance the variability of both sets of deposits reflects strong topographic influences on snow accumulation and ablation patterns in their deep cirques tephrochronology and radiocarbon dates from lake sediment cores provide limits on the timing of the two advances previous work documenting the absence of a young regionally extensive tephra on matthes moraines in the central sierra demonstrates that they formed after 700 14c years bp 650 cal years bp the age of the recess peak advance has been less certain we therefore collected and dated sediment cores from lakes dammed behind terminal moraines correlating to the recess peak advance in four widely separated drainages along the sierran crest north to south south fork american river lee vining creek middle fork san joaquin river and bishop creek twenty three high precision ams radiocarbon dates on gyttja peat and macrofossils from the cores are internally consistent and demonstrate that the recess peak advance previously thought to be of late holocene age 2500 years bp ended before 11 190 70 14c years bp 13 100 85 cal years bp recess peak is therefore late pleistocene in age and probably predates the north atlantic younger dryas climatic reversal the absence of any glacial deposits on the bedrock between the recess peak and matthes deposits indicates that 1 any advance related to the younger dryas event in central california was smaller than the matthes advance 2 the matthes advance was the most extensive and possibly the only neoglacial event in the range and 3 climate in the sierra between 13 000 cal years bp and 650 cal years bp was apparently too warm and or dry to support glaciers larger than those of the little ice age other mapping indicates that the recess peak is the first significant glacier advance after retreat of tioga local late wisconsin maximum glaciers these results suggest a regionally variable climate in western north america during the younger dryas event because glaciers appear to have expanded in the canadian rockies at that time the new recess peak age limits combined with other dated lake cores indicate that the sierra was essentially deglaciated by 14 000 15 000 cal years bp 12 000 13 000 14c years bp substantially earlier than previously estimated this finding indicates that current production rates of some in situ cosmogenic nuclides calibrated on an assumed deglaciation of the range at 11 000 cal years bp 10 000 14c years bp may be systematically too high by as much as 20

volcanic subsidence triggered by the 2011 tohoku earthquake in japan the 2011 tohoku earthquake caused high levels of crustal deformation in japan analysis of satellite radar and gps data show that the earthquake caused nearby volcanic regions to subside instantaneously creating elliptical depressions that are parallel to the direction of quake induced crustal extension

bedrock fracture control of glacial erosion processes and rates the importance of rock type and tectonic history on rates of glacial erosion and the relative roles of glacial quarrying and abrasion are poorly understood we use concentrations of cosmogenic 10be in glacial polish and measurements of bedrock fracture spacing to explore the relationship between erosion rates and rock fracturing at 23 sites along tuolumne river valley and five sites in tenaya canyon in yosemite national park california usa most sites yield 10be concentrations that can be best explained as reflecting solely postglacial nuclide accumulation six sites however display anomalously high concentrations implying incomplete removal of the pre glacial nuclide inventory during the last glaciation these require that erosion in the last glacial cycle was 2 3 m these low erosion sites occur preferentially in massive units of the cathedral peak granodiorite and the el capitan granite fractures in high erosion sites are more closely spaced than in low erosion sites with spacings that average 1 1 0 03 m and 3 3 0 1 m respectively our data suggest that the distance between fractures in the rock dictated in part by the original spacing in a particular pluton and in part by the specific tectonic history of the sierra nevada governs the pace of glacial erosion in yosemite

an insar based survey of volcanic deformation in the southern andes we use interferometric synthetic aperture radar insar to search for surface deformation in the southern andes 40 s 46 s and 49 s 53 s associated with magmatic processes although the available data are not optimal we can constrain the amount of volcanic deformation at about 27 holocene volcanoes between the years 1993 1999 we detect inflation of cerro hudson volcano following its 1991 eruption and use spherical and non spherical models to constrain the source of deformation to be between 4 and 8 km below sea level we measure the rate of deformation to be about 5 cm year in the radar line of sight and infer that the maximum deformation could exceed 10 cm year in the center of the caldera within the errors of the measurements the rate of deformation is constant from 1993 1998 10 30 10 6 m 3 year at this rate 100 200 years is required to accumulate the volume of material erupted in 1991

shallow seismicity triggered seismicity and ambient noise tomography at the long dormant uturuncu volcano bolivia using a network of 15 seismometers around the inflating uturuncu volcano from april 2009 to 2010 we find an average rate of about three local volcano tectonic earthquakes per day and swarms of 5 60 events a few times per month with local magnitudes ranging from 1 2 to 3 7 the earthquake depths are near sea level more than 10 km above the geodetically inferred inflation source and the altiplano puna magma body the mw 8 8 maule earthquake on 27 february 2010 triggered hundreds of earthquakes at uturuncu with the onset of the love and rayleigh waves and again with the passage of the x2 x3 overtone phases of rayleigh waves this is one of the first incidences in which triggering has been observed from multiple surface wave trains the earthquakes are oriented nw se similar to the regional faults and lineaments the b value of the catalog is 0 49 consistent with a tectonic origin of the earthquakes we perform ambient noise tomography using love wave cross correlations to image a low velocity zone at 1 9 to 3 9 km depth below the surface centered slightly north of the summit the low velocities are perhaps related to the hydrothermal system and the low velocity zone is spatially correlated with earthquake locations the earthquake rate appears to vary with time a seismic deployment from 1996 to 1997 reveals 1 5 earthquakes per day whereas 60 events day were seen during 5 days using one seismometer in 2003 however differences in analysis methods and magnitudes of completeness do not allow direct comparison of these seismicity rates the rate of seismic activity at uturuncu is higher than at other well monitored inflating volcanoes during periods of repose the frequent swarms and triggered earthquakes suggest the hydrothermal system is metastable