thermal infrared data analyses of meteor crater arizona implications for mars spaceborne data from the thermal emission imaging system thermal infrared tir data from the advanced spaceborne thermal emission and reflection radiometer aster instrument are used to identify the lithologic distribution of the meteor crater ejecta blanket and nearby within 3 km region this has many applications to the analysis of data from the thermal emission imaging system themis instrument that is currently in orbit at mars aster and themis whereas orbiting different planets have similar spatial and spectral resolutions themis represents the highest spatial resolution 100 m to date of the martian surface thereby allowing small 1km impact craters to be studied in detail for the first time meteor crater serves as an analog for the many similar sized impact sites on the surface of mars these sites are future research targets with themis and aster data of meteor crater provides ideal data and geologic landscape in preparation for future themis investigations fieldwork at meteor crater yielded sample collection of the primary lithologies and an opportunity to validate previously collected high resolution 3 2 m airborne thermal imaging multispectral scanner tims data laboratory thermal emission spectra were obtained for the samples collected deconvolution of aster tir emissivity data were performed with image end members and sample end members comparisons of the spaceborne data to high resolution airborne tims data were used to assess the validity of the aster end member analyses the aster image end member analysis agreed well with the earlier tims end member analysis where the effects of resolution degradation were accounted for laboratory spectra and mineral spectral libraries provided poor fits of deconvolution of multispectral tir data lithologies with similar spectral signatures or with low areal abundances were difficult to identify using the same methodology as that applied to the aster tir data of meteor crater themis tir data of a small 1 km impact crater in syrtis major were analyzed the crater s rim and ejecta blanket was found to contain larger particle sizes than the surrounding ejecta free plain indicating a young fresh impact age and little or no accumulation of dust the composition of the rim ejecta and surrounding plain was determined to be basaltic it is hoped that the work performed here will complement future investigations of fresh impact sites with themis data that may be used to solve geologic questions such as 1 the composition of ejecta blocks that represent pre impact underlying stratigraphy in high albedo dust covered regions of mars 2 the approximate age of impact and 3 regolith dust thickness which appears to be a factor of 2

observations at terrestrial impact structures their utility in constraining crater formation hypervelocity impact involves the near instantaneous transfer of considerable energy from the impactor to a spatially limited near surface volume of the target body local geology of the target area tends to be of secondary importance and the net result is that impacts of similar size on a given planetary body produce similar results this is the essence of the utility of observations at impact craters particularly terrestrial craters in constraining impact processes unfortunately there are few well documented results from systematic contemporaneous campaigns to characterize specific terrestrial impact structures with the full spectrum of geoscientific tools available at the time nevertheless observations of the terrestrial impact record have contributed substantially to fundamental properties of impact there is a beginning of convergence and mutual testing of observations at terrestrial impact structures and the results of modeling in particular from recent hydrocode models the terrestrial impact record provides few constraints on models of ejecta processes beyond a confirmation of the involvement of the local substrate in ejecta lithologies and shows that z models are at best first order approximations observational evidence to date suggests that the formation of interior rings is an extension of the structural uplift process that occurs at smaller complex impact structures there are however major observational gaps and cases e g vredefort where current observations and hydrocode models are apparently inconsistent it is perhaps time that the impact community as a whole considers documenting the existing observational and modeling knowledge gaps that are required to be filled to make the intellectual breakthroughs equivalent to those of the 1970s and 1980s which were fueled by observations at terrestrial impact structures filling these knowledge gaps would likely be centered on the later stages of formation of complex and ring structures and on ejecta

structural geology of impact craters abstract the formation of impact craters is a highly dynamic and complex process that subjects the impacted target rocks to numerous types of deformation mechanisms understanding and interpreting these styles of micro meso and macroscale deformation has proved itself challenging for the field of structural geology in this paper we give an overview of the structural inventory found in craters of all size ranges on earth and look into the structures of craters on other planetary bodies structural features are discussed here that are caused by i extremely high pressures and temperatures that occur during the initial passage of the shock wave through the target rock and projectile ii the resulting flow field in the target that excavates and ejects rock materials and iii the gravitationally induced modification of the crater cavity into the final crater form a special focus is put on the effects that low angle impacting bodies have on crater formation we hope that this review will help both planetary scientists and structural geologists understand the deformation processes and resulting structures generated by meteorite impact

interdecadal changes of 30 yr sst normals during 1871 2000 abstract sst predictions are usually issued in terms of anomalies and standardized anomalies relative to a 30 yr normal climatological mean cm and standard deviation sd the world meteorological organization wmo suggests updating the 30 yr normal every 10 yr in complying with the wmo s suggestion a new 30 yr normal for the 1971 2000 base period is constructed to put the new 30 yr normal in historical perspective all the 30 yr normals since 1871 are investigated starting from the beginning of each decade 1871 1900 1881 1910 1971 2000 using the extended reconstructed sea surface temperature ersst on a 2 grid for 1854 2000 and the hadley centre sea ice and sst dataset hadisst on a 1 grid for 1870 1999 eleven 30 yr normals are calculated and the interdecadal changes of seasonal cm seasonal sd and seasonal persistence p are discussed the interdecadal changes of seasonal cm are prominent 0 3 0 6 in the tropical indian ocean the midlatitude north pacific the midlatitude no

impact of the atlantic multidecadal oscillation on north pacific climate variability 1 in this paper we found that the atlantic multidecadal oscillation amo can contribute to the pacific decadal oscillation pdo especially the component of the pdo that is linearly independent of el nino and the southern oscillation enso i e the north pacific multidecadal oscillation npmo and the associated pacific north america pna pattern using a hybrid version of the gfdl cm2 1 climate model we show that the amo provides a source of multidecadal variability to the north pacific and needs to be considered along with other forcings for north pacific climate change the lagged north pacific response to the north atlantic forcing is through atmospheric teleconnections and reinforced by oceanic dynamics and positive air sea feedback over the north pacific the results indicate that a north pacific regime shift opposite to the 1976 77 shift might occur now a decade after the switch of the observed amo to a positive phase around 1995 citation zhang r and t l delworth 2007 impact of the atlantic multidecadal oscillation on north pacific climate variability geophys res lett 34 l23708

the 2010 haiti earthquake a complex fault pattern constrained by seismologic and tectonic observations after the january 12 2010 haiti earthquake we deployed a mainly offshore temporary network of seismologic stations around the damaged area the distribution of the recorded aftershocks together with morphotectonic observations and mainshock analysis allow us to constrain a complex fault pattern in the area almost all of the aftershocks have a n s compressive mechanism and not the expected left lateral strike slip mechanism a first order slip model of the mainshock shows a n264 e north dipping plane with a major left lateral component and a strong reverse component as the aftershock distribution is sub parallel and close to the enriquillo fault we assume that although the cause of the catastrophe was not a rupture along the enriquillo fault this fault had an important role as a mechanical boundary the azimuth of the focal planes of the aftershocks are parallel to the north dipping faults of the transhaitian belt which suggests a triggering of failure on these discontinuities in the western part the aftershock distribution reflects the triggering of slip on similar faults and or alternatively of the south dipping faults such the trois baies submarine fault these observations are in agreement with a model of an oblique collision of an indenter of the oceanic crust of the southern peninsula and the sedimentary wedge of the transhaitian belt the rupture occurred on a wrench fault at the rheologic boundary on top of the under thrusting rigid oceanic block whereas the aftershocks were the result of the relaxation on the hanging wall along pre existing discontinuities in the frontal part of the transhaitian belt

thermoluminescence measurements on shock metamorphosed sandstone and dolomite from meteor crater arizona 2 thermoluminescence age of meteor crater thermoluminescence tl dating measurements were performed on shock metamorphosed rocks from meteor crater arizona il ages were obtained for eight specimens four coconino sandstone and four kaibab dolomite which experienced sufficient shock heating during the impact to reset their preimpact tl postimpact radiation doses were determined for each shocked fragment from thermoluminescence measurements on quartz mineral separates effective radiation dose rates were calculated from concentrations of uranium thorium potassium and rubidium in the rocks and their burial environment and the distributions of these elements as determined by fission track and microprobe analyses cosmic radiation dose rates were estimated by altitude scaling of sea level data and were corroborated by tl dosimeter measurements at the crater the mean tl ages for the two rock types were reasonably concordant 50 400 2900 and 46 000 3100 years for sandstones and dolomites respectively the overall mean age 49 000 3000 years is significantly older than the 25 000 year age estimate based on the inferred correlation of the oldest pluvial episode at the crater with radiometrically dated 18o maxima

complex rupture during the 12 january 2010 haiti earthquake initially the devastating mw 7 0 12 january 2010 haiti earthquake seemed to involve straightforward accommodation of oblique relative motion between the caribbean and north american plates along the enriquillo plantain garden fault zone here we combine seismological observations geologic field data and space geodetic measurements to show that instead the rupture process involved slip on multiple faults primary surface deformation was driven by rupture on blind thrust faults with only minor deep lateral slip along or near the main enriquillo plantain garden fault zone thus the event only partially relieved centuries of accumulated left lateral strain on a small part of the plate boundary system together with the predominance of shallow off fault thrusting the lack of surface deformation implies that remaining shallow shear strain will be released in future surface rupturing earthquakes on the enriquillo plantain garden fault zone as occurred in inferred holocene and probable historic events we suggest that the geological signature of this earthquake broad warping and coastal deformation rather than surface rupture along the main fault zone will not be easily recognized by standard palaeoseismic studies we conclude that similarly complex earthquakes in tectonic environments that accommodate both translation and convergence such as the san andreas fault through the transverse ranges of california may be missing from the prehistoric earthquake record

quantitative measurement method for impact basin characteristics based on localized spherical harmonics abstract characteristics of impact basins are important fundamental knowledge for assessing basin forming impacts and their influence on surficial and interior structural evolutions for lunar and planetary bodies to estimate impact basin characteristics based on spherical harmonic expressions of topographic figures we propose a quantitative method that we apply it to actual lunar topographic data the estimated basin locations center are almost coincident with those determined by visual inspection however the numbers of ring structures differ from previously reported ones the relation between the ring height and the ring diameter coincides well with those reported previously some older basins show discrepancies in the height diameter relation which probably reflect the degree of degradation by subsequent small impacts we recognize a power law relation between the diameters of a ring and a neighboring ring structure that relation suggests that the formation volume and modification of the melt cavity control the formation and size of peak ring and multi ring structures these relations which are thought to reflect the mechanism of the collapse stage of basin formation impact provide helpful constraints for elucidating the long standing problem of how multi ring impact basins are formed

a geometric model for excavation and modification at terrestrial simple impact craters a geometric model for the excavation and modification of simple crater development is presented modification is modelled by considering the relative dimensions and geometries of the final crater and the transient cavity formed by excavation and displacement the input parameters required are the rim crest diameter of the final crater the depth to autochthonous basement the rim crest height and the outer rim slope the model calculates the diameter of the final crater at the original ground plane the dimensions of the transient cavity and the rim crest volume difference between the final and transient cavities this volume is considered to be the material which slumped off the unstable overheightened transient cavity wall during modification and corresponds to the observed volume of the breccia lens within the final crater excavation is approximated by a steady state z model with the diameter of excavation equivalent to the previously modelled diameter of the transient cavity at the original ground plane the center of flow taken as 1 projectile diameter and z 2 5 3 0 the z model predicts such parameters as the depth and volume of excavation which can be compared with observational data the applicability of the model has been tested with data from meteor and brent craters in the case of meteor the modelled final crater diameter at the original ground plane is within 26 m of the observed value and the modelled breccia lens and the rim crest volumes of the final true crater are within 9 5 and 2 5 respectively of observed values the results of the z model for meteor crater with z 2 8 0 1 give results consistent with observational data on the depth and volume of excavation the correspondence for the more degraded brent crater is less precise as there is greater uncertainty in the input parameters it is possible however to match the model parameters with the breccia lens volume and published estimates of original dimensions the modelled excavated volumes for meteor and brent are 58 and 55 respectively of the transient cavity volume below the original ground plane in the absence of additional observational data for further testing it is concluded that the model may provide first order spatial information on the formation of simple craters

ejecta distribution patterns at meteor crater arizona on the applicability of lithologic end member deconvolution for spaceborne thermal infrared data of earth and mars 1 a spectral deconvolution using a constrained least squares approach was applied to airborne thermal infrared multispectral scanner tims data of meteor crater arizona the three principal sedimentary units sampled by the impact were chosen as end members and their spectra were derived from the emissivity images to validate previous estimates of the erosion of the near rim ejecta the model was used to identify the areal extent of the reworked material the outputs of the algorithm reveal subtle mixing patterns in the ejecta identified larger ejecta blocks and were used to further constrain the volume of coconino sandstone present in the vicinity of the crater the availability of the multialtitude data set also provided a means to examine the effects of resolution degradation and quantify the subsequent errors on the model these data served as a test case for the use of image derived lithologic end members at various scales which is critical for examining thermal infrared data of planetary surfaces the model results indicate that the coconino ss reworked ejecta is detectable over 3 km from the crater this was confirmed by field sampling within the primary ejecta field and wind streak the areal distribution patterns of this unit imply past erosion and subsequent sediment transport that was low to moderate compared with early studies and therefore places further constraints on the ejecta degradation of meteor crater it also provides an important example of the analysis that can be performed on thermal infrared data currently being returned from earth orbit and expected from mars in 2002

degradation of selected terrestrial and martian impact craters degraded craters on mars record the cumulative effects of the complex interplay between erosion transport and deposition by competing intermittent processes fortunately impact craters are instantaneous landforms common to both the earth and mars that are characterized by similar topography and local lithofacies deconvolving the signatures of individual degradation processes around young craters on earth e g drainage scale and density changing wall slope deflation features allows calibrating degradation signatures around craters on mars and places first order limits on controlling processes and perhaps past climates such comparisons are valid despite differences in vegetation cover and time scales over which activity occurs on the two planets analysis of degradation at meteor crater lonar crater and talemzane crater reveals a terrestrial sequence of advancing degradation by fluvial eolian and mass wasting processes at meteor crater fluvial processes currently dominate primary erosion however combined deflation from the ejecta and both alluvium and colluvium make eolian processes most important in overall ejecta degradation lonar and talemzane reveal that advancing fluvial degradation is characterized by larger drainages and decreasing wall slopes at talemzane interior drainages breach the rim crest and pirate headward regions of exterior drainage basins when comparable degradation signatures resolvable at viking resolutions are used in selected areas on mars important differences from the terrestrial sequence are revealed all morphologies of craters in southern ismenius lacus sil are typically incised by small valleys with low drainage densities display rare alluvial deposits possess walls sloped at the angle of repose and are sometimes partially covered by airfall deposit remnants analogy with the terrestrial craters indicates signatures associated with advancing fluvial degradation should be readily detected on mars together with other differences between degraded craters on the two planets the paucity of fluvial signatures in sil implies that mass wasting and eolian activity predominated degradation of martian craters preserved since the hesperian crater statistics for sil indicate most craters were degraded during geologically brief intervals in the noachian and mid hesperian therefore fluvial signatures preserved in sil imply any runoff since the hesperian was short lived locally debouched and unrelated to rainfall

possible north atlantic origin for changes in enso properties during the 1970s the most intense el nino episodes in more than a century occurred after the 1970s climate shift previous studies show that the characteristics of the el nino southern oscillation enso phenomenon changed synchronously with the shift but the associated causes are not fully understood an analysis of the observed tropical pacific sea surface temperature sst anomalies shows that their increase in the eastern part of the basin after the 1970s is not related to the canonical enso pattern but to the tropical pacific meridional mode tpmm we present observational evidence which supports the hypothesis that the change in the tpmm was triggered by the great salinity anomaly gsa which manifested in the north atlantic during the late 1960s the gsa induced a weak labrador convection and a sst dipole south of greenland the associated atmospheric structure includes a north pacific oscillation sea level pressure dipole in the pacific sector this excites the tpmm which contributes to the intense el nino events and to the enhanced enso s asymmetry observed after the shift our results imply that if the gsa has not an anthropic origin as was suggested then the tropical pacific climate shift has a natural origin this is supported by the end of the north atlantic regime in the 1990s and by the rebound of the tropical pacific after 1998

the subsurface character of meteor crater arizona as determined by ground probing radar ground probing radar has provided new two dimensional stratigraphic and structural information on meteor crater arizona four 50 mhz transects inside the crater and one 100 mhz transect on a northeast radial across the exterior ejecta blanket were carried out the frequencies used were in relation to the desired depth of investigation greater than 50 m at 50 mhz and 30 m for 100 mhz the results obtained inside the crater show that the water table can be clearly detected at depths of 65 m as can the contact between the crater wall and the infilling allochthonous breccia lens in addition we were able to detect 1 point reflectors from relatively coherent blocks 1 5m within the breccia lens 2 a zone 7 m thick relatively free of point reflectors from the immediate fall back unit 3 a series of subhorizontal reflectors a few meters apart due to bedding in the post impact crater sediments and 4 five separate subhorizontal reflectors from what we interpret to be a series of postimpact paleo water table levels in the breccia lens the ejecta blanket transect indicates a 4 10 m thick ejecta layer and the underlying moenkopi formation sandstone as well as the moenkopi kaibab contact and bedding within the kaibab formation in addition reverse faults with displacements up to 4 m were detected in the bedrock as well as changes from subhorizontal to 30 in the dip of the bedrock as the crater rim is approached from the northeast beneath the ejecta blanket the total uplift observed at the crater rim is around 55 m the radar data indicate uplift effects out to a radial distance of 400 m from the rim farther than that determined from drilling 300 m the results demonstrate the utility of continuous ground probing radar cross sections in studying the near subsurface 50 m character at meteor crater this relatively rapid low cost technique can be extended to other structures but confident interpretation requires supplemental ground truth constraints

origin of the structure and planform of small impact craters in fractured targets endurance crater at meridiani planum mars we present observations and models that together explain many hallmarks of the structure and growth of small impact craters forming in targets with aligned fractures endurance crater at meridiani planum on mars diameter 150 m formed in horizontally layered aeolian sandstones with a prominent set of wide orthogonal joints a structural model of endurance crater is assembled and used to estimate the transient crater planform the model is based on observations from the mars exploration rover opportunity a bedding plane orientations and layer thicknesses measured from stereo image pairs b a digital elevation model of the whole crater at 0 3 m resolution and c color image panoramas of the upper crater walls this model implies that the crater s current shape was mostly determined by highly asymmetric excavation rather than long term wind mediated erosion we show that modal azimuths of conjugate fractures in the surrounding rocks are aligned with the square component of the present day crater planform suggesting excavation was carried farther in the direction of fracture alignments this was previously observed at barringer crater in arizona and we show the same relationship also holds for tswaing crater in south africa we present models of crater growth in which excavation creates a stellate transient cavity that is concave cuspate in planform these models reproduce the lenticular crescentic layering pattern in the walls of some polygonal impact craters such as endurance and barringer craters and suggest a common origin for tear faults and some crater rays we also demonstrate a method for detailed error analysis of stereogrammetric measurements of bedding plane orientations

the terrestrial impact cratering record approximately 130 terrestrial hypervelocity impact craters are currently known due to variations in preservation and in geologic knowledge this sample is biased towards young x 20 km craters on the cratons of australia europe including the former u s s r and north america the rate of discovery of new craters is 3 5 craters per year although modified by erosion terrestrial impact craters exhibit the range of morphologies observed for craters on other terrestrial planetary bodies such as the moon terrestrial craters provide essential ground truth data on the geologic effects of impact and the subsurface structure of impact craters which can be used to constrain interpretations of lunar samples and models of crater formation due to erosion and its effects on form terrestrial craters are recognized primarily by the occurrence of shock metamorphic effects these include shatter cones microscopic planar deformation features solid state and fusion glasses high pressure polymorphs and whole rock melting and vaporization shock recovery experiments indicate that these features occur over shock pressures of 5 gpa to x 100 gpa terrestrial craters have a set of geophysical characteristics which are largely the result of the passage of a shock wave and impact induced fracturing they include gravity and magnetic lows and reductions in seismic velocity the gravity anomalies are seldom greater than 30 mgal due to the limiting effects of lithostatic pressure on fracturing at large complex craters the gravity signature may include a central relative gravity high due to uplift and short wavelength central magnetic anomalies due to a variety of processes much current work is focused on the effects of impact on earth evolution previous work on shock metamorphism and the contamination of impact melt rocks by meteoritic siderophile elements provides a basis for the interpretation of the physical and chemical evidence from cretaceous tertiary boundary sites as resulting from a major impact suggestions that other biological boundaries in the stratigraphie record are due to periodic impacts are not supported by time series analysis of the terrestrial cratering record by analogy with the lunar record and modelling of the effects of very large impacts it has been proposed that biological and atmospheric evolution of the earth could not stabilize before the end of the late heavy bombardment 3 8 ga ago the present terrestrial cratering rate is 5 4 2 7 10 15 km 2a 1 for a diameter 20 km this represents a local threat on historic time scales on a global scale a major impact sufficient to cripple human civilization severely will occur on time scales of 106 a

gradation of the roter kamm impact crater namibia interpretation of ground penetrating radar data from the 3 7 ma old roter kamm impact crater together with results of petrographic and sedimentologic analysis of sediment samples indicates that 40 m or more of slope sensitive degradation of the rim was accompanied by reduction of wall slopes well below the angle of repose and nearly complete erosion of ejecta from around the crater only one patch of in situ ejecta deposit was identified degradation of both the interior and exterior of the crater was dominated by fluvial alluvial activity likely during the first 1 0 2 7 ma history of the crater eolian modification has dominated gradation since the last half of the pleistocene results from roter kamm can help in evaluating evolution of degraded martian craters that may have experienced fluvial alluvial gradation followed by eolian modification on mars extended fluvial alluvial activity should produce a low sloped incised rim thereby eroding most of the continuous ejecta well before removal of easily recognizable rim relief subsequent eolian deposition can bury all but the raised rim of craters thereby creating a focal point for efforts geared towards constraint of gradational history

earthquake source parameters for the 2010 january haiti main shock and aftershock sequence summary previous analyses of geological and geodetic data suggest that the obliquely compressive relative motion across the caribbean north america plate boundary in hispaniola is accommodated through strain partitioning between near vertical transcurrent faults on land and low angle thrust faults offshore in the dominican republic earthquake focal mechanism geometries generally support this interpretation little information has been available about patterns of seismic strain release in haiti however due to the small numbers of moderate to large earthquakes occurring in western hispaniola during the modern instrumental era here we analyse the damaging mw 7 0 earthquake that occurred near port au prince on 2010 january 12 and aftershocks occurring in the four months following this event to obtain centroid moment tensor cmt solutions for 50 earthquakes with magnitudes as small as mw 4 0 while the 2010 january main shock exhibited primarily strike slip motion on a steeply dipping nodal plane strike 250 dip 71 and rake 22 we find that nearly all of the aftershocks show reverse faulting motion typically on high angle 30 45 nodal planes two small aftershocks mw 4 5 and 4 6 located very close to the main shock epicentre show strike slip faulting with geometries similar to the main shock one aftershock located off the south coast of haiti shows low angle thrust faulting we also examine earthquakes occurring in this region from 1977 2009 successful analysis of four such events provides evidence for both strike slip and reverse faulting the pattern of seismic strain release in southern haiti thus indicates that partitioning of plate motion between transcurrent and reverse structures extends far west within hispaniola while we see limited evidence for low angle underthrusting offshore most reverse motion appears to occur on high angle fault structures adjacent to the enriquillo fault our results highlight the need to incorporate seismogenic slip on compressional structures into hazard assessments for southern haiti

strain partitioning and fault slip rates in the northeastern caribbean from gps measurements 1 gps data collected in the dominican republic from 1994 to 2001 show that oblique convergence between the north american and caribbean plates is partitioned between 5 2 2 mm yr 1 of dip slip reverse motion on the north hispaniola thrust approximately n s and 12 8 2 5 mm yr 1 and 9 0 9 0 mm yr 1 of approximately e w left lateral strike slip motion on the septentrional and enriquillo faults 95 confidence the agreement between gps and paleoseimological slip rates on the septentrional fault together with the 770 960 years since the last major earthquake and the 800 1200 years maximum repeat time of major earthquakes may indicate that the septentrional fault is currently in the late phase of its rupture cycle

on the pacific decadal oscillation and the atlantic multidecadal oscillation might they be related 1 the nature of the pacific decadal oscillation pdo is investigated based upon analyses of sea surface temperature observations over the last century the pdo is suggested to be comprised of a 20 year quasi periodic oscillation and a lower frequency component with a characteristic timescale of 60 years the 20 year quasi periodic oscillation is clearly identified as a phase locked signal at the eastern boundary of the pacific basin which could be interpreted as the signature of an ocean basin mode we demonstrate that the 60 year component of the pdo is strongly time lag correlated with the atlantic multidecadal oscillation amo on this timescale the amo is shown to lead the pdo by approximately 13 years or to lag the pdo by 17 years this relation suggests that the amo and the 60 year component of the pdo are signatures of the same oscillation cycle

erosion of ejecta at meteor crater arizona new methods for estimating erosion at meteor crater arizona indicate that continuous ejecta deposits beyond 1 4 1 2 crater radii from the rim 0 25r 0 5r have been lowered less than 1 m on the average this conclusion is based on the results of two approaches coarsening ofunweathered ejectainto surface lag deposits and calculation of the sediment budget within a drainage basin on the ejecta preserved ejecta morphologies beneath thin alluvium revealed by ground penetrating radar provide qualitative support for the derived estimates although slightly greater erosion 2 3 m of less resistant ejecta locally has occurred such deposits were limited in extent particularly beyond 0 25r 0 5r from the present rim subtle but preserved primary ejecta features e g distal ejecta lobes and blocks further support our estimate of minimal erosion of ejecta since the crater formed 50 000 years ago unconsolidated deposits formed during other sudden extreme events e g landslides exhibit similarly low erosion over the same time frame the common factor is the presence of large fragments or large fragments in a matrix of finer debris at meteor crater fluvial and eolian processes remove surrounding fines leaving behind a surface lag of coarse grained ejecta fragments that armor surfaces and slow vertical lowering

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

enhancement of enso variability by a weakened atlantic thermohaline circulation in a coupled gcm abstract a coupled ocean atmosphere general circulation model is used to investigate the modulation of el nino southern oscillation enso variability due to a weakened atlantic thermohaline circulation thc the thc weakening is induced by freshwater perturbations in the north atlantic and leads to a well known sea surface temperature dipole and a southward shift of the intertropical convergence zone itcz in the tropical atlantic through atmospheric teleconnections and local coupled air sea feedbacks a meridionally asymmetric mean state change is generated in the eastern equatorial pacific corresponding to a weakened annual cycle and westerly anomalies develop over the central pacific the westerly anomalies are associated with anomalous warming of sst causing an eastward extension of the west pacific warm pool particularly in august february and enhanced precipitation these and other changes in the mean state lead in turn to an eastward shift of the zonal wind anomalies associated with el nin

imaging the subsurface stratigraphy in the ubehebe hydrovolcanic field death valley california using ground penetrating radar abstract ground penetrating radar gpr surveys were carried out to collect subsurface images of the basaltic base surge deposits in the ubehebe hydrovolcanic field death valley national park california antennae with frequencies of 50 100 and 200 mhz were used this technique allowed the collection of useful geologic data for example the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated different radar responses were also obtained from base surge deposits and underlying sedimentary rocks which enable their recognition where no outcrops are available furthermore gpr data confirmed the presence of small eroded craters which are partially filled by alluvium in this case an unconformity between the overlying horizontally bedded alluvium and the underlying bowl shaped base surge deposits can be recognized within the crater and the thickness of the alluvium estimated common mid point cmp surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0 095 0 1 m ns

enso suppression due to weakening of the north atlantic thermohaline circulation changes of the north atlantic thermohaline circulation thc excite wave patterns that readjust the thermocline globally this paper examines the impact of a freshwater induced thc shutdown on the depth of the pacific thermocline and its subsequent modification of the el nino southern oscillation enso variability using an intermediate complexity global coupled atmosphere ocean sea ice model and an intermediate enso model respectively it is shown by performing a numerical eigenanalysis and transient simulations that a thc shutdown in the north atlantic goes along with reduced enso variability because of a deepening of the zonal mean tropical pacific thermocline a transient simulation also exhibits abrupt changes of enso behavior depending on the rate of thc change the global oceanic wave adjustment mechanism is shown to play a key role also on multidecadal time scales simulated multidecadal global sea surface temperature sst patterns show a large degree of similarity with previous climate reconstructions suggesting that the observed pan oceanic variability on these time scales is brought about by oceanic waves and by atmospheric teleconnections

impact fracturing and structural modification of sedimentary rocks at meteor crater arizona 1 meteor crater provides a rare opportunity to study impact deformation of sedimentary target rocks and isolate those features from preexisting tectonic deformation and impact generated reactivation of preexisting tectonic features this study reports over 2500 new measurements of orientations of bedding faults and fractures in crater walls and in surrounding bedrock target rocks are characterized by horizontal bedding planes that are cut by at least three prominent sets of preimpact tectonic fracture systems the crater rim is also cut by three distinct groups of fractures radial concentric and conical fractures when the crater rim is restored to preimpact condition the radial and concentric fractures resemble preimpact fracture populations indicating that crater wall deformation and rim uplift were partly accommodated by activation of preexisting fractures in contrast the conical fractures are dissimilar to the preimpact fractures and apparently formed as a direct result of impact deformation some of the preimpact fractures were transformed into tear faults during the impact event and motion along those faults appears to have controlled the geometry of the impact deformational features the crater rim is thus square in plan view rather than circular faults occurring in the crater diagonals are prominent ones allowing greater vertical displacement the deformation pattern of meteor crater is different from that at lonar crater which was excavated in basalt with fewer preimpact fractures the differences between deformation at meteor crater and lonar crater may reflect the same disparities seen in simple craters produced in different target lithologies on mars and other planetary surfaces

ground penetrating radar investigation of active faults along the dead sea transform and implications for seismic hazards within the city of aqaba jordan abstract ground penetrating radar gpr was used in an effort to locate a major active fault that traverses aqaba city jordan measurements over an exposed trenched cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset flexured reflectors both showing a geometric correlation with two known faults at a control site the asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults however other observations regarding this radar signature render the mechanism generating these events more complex and uncertain gpr measurements in aqaba city were limited to vacant lots seven gpr profiles were conducted approximately perpendicular to the assumed strike of the fault zone based on regional geological evidence a radar response very similar to that obtained over the cross fault was observed on five of the profiles in aqaba city although the response is weaker than that obtained at the control site the positions of the identified responses form a near straight line with a strike of 45 although subsurface verification of the fault by trenching within the city is needed the geophysical evidence for fault zone location is strong the location of the interpreted fault zone relative to emergency services military bases commercial properties and residential areas is defined to within a few meters this study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region

linking emergence of the central pacific el nino to the atlantic multidecadal oscillation abstractthe ocean atmosphere coupling in the northeastern subtropical pacific is dominated by a pacific meridional mode pmm which spans between the extratropical and tropical pacific and plays an important role in connecting extratropical climate variability to the occurrence of el nino analyses of observational data and numerical model experiments were conducted to demonstrate that the pmm and the subtropical pacific coupling experienced a rapid strengthening in the early 1990s and that this strengthening is related to an intensification of the subtropical pacific high caused by a phase change of the atlantic multidecadal oscillation amo this pmm strengthening favored the development of more central pacific cp type el nino events the recent shift from more conventional eastern pacific ep to more cp type el nino events can thus be at least partly understood as a pacific ocean response to a phase change in the amo

bi decadal variability excited in the coupled ocean atmosphere system by strong tropical volcanic eruptions decadal and bi decadal climate responses to tropical strong volcanic eruptions sves are inspected in an ensemble simulation covering the last millennium based on the max planck institute earth system model an unprecedentedly large collection of pre industrial sves up to 45 producing a peak annual average top of atmosphere radiative perturbation larger than 1 5 wm 2 is investigated by composite analysis post eruption oceanic and atmospheric anomalies coherently describe a fluctuation in the coupled ocean atmosphere system with an average length of 20 25 years the study provides a new physically consistent theoretical framework to interpret decadal northern hemisphere nh regional winter climates variability during the last millennium the fluctuation particularly involves interactions between the atlantic meridional overturning circulation and the north atlantic gyre circulation closely linked to the state of the winter north atlantic oscillation it is characterized by major distinctive details among them the most prominent are a a strong signal amplification in the arctic region which allows for a sustained strengthened teleconnection between the north pacific and the north atlantic during the first post eruption decade and which entails important implications from oceanic heat transport and from post eruption sea ice dynamics and b an anomalous surface winter warming emerging over the scandinavian western russian region around 10 12 years after a major eruption the simulated long term climate response to sves depends to some extent on background conditions consequently ensemble simulations spanning different phases of background multidecadal and longer climate variability are necessary to constrain the range of possible post eruption decadal evolution of nh regional winter climates