late quaternary deformation of the toppenish ridge uplift in south central washington mapping of quaternary sedimentary rocks and miocene basalts on toppenish ridge a fold in south central washington reveals a 32 km long zone of nearly 100 surface ruptures the ruptures indicate renewed movement on miocene structures in latest quaternary time the ruptures probably formed in response to regional compressive stress between 500 and 13 000 yr ago these ruptures are interpreted to represent the most recent surface deformation in central washington

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

vegetation and fire history during the last 30 000 years based on phytolith and macroscopic charcoal records in the eastern and western areas of aso volcano japan abstract vegetation and fire history during the last 30 000 years has been reconstructed using phytolith and macroscopic charcoal records obtained from two tephra sections around aso caldera southwestern japan phytolith assemblages from both sites revealed that grassland vegetation dominated by gramineae consistently occurred for more than 30 000 years prior to 13 5 ka vegetation both east and west of aso caldera was composed mainly of sasa cool temperate dwarf bamboo although the vegetation east of the caldera considerably declined by intense volcanic activity between 30 and 13 5 ka in the holocene miscanthus pampas grass grassland was established and continued consistently to the present in the eastern area whereas sasa and pleioblastus warm temperate dwarf bamboo grassland has existed in the western area of the volcano the difference of grassland vegetation transition in the holocene between the eastern and western regions can be explained as difference of fire regime between both areas inferred from macroscopic charcoal records prior to 13 5 ka fire activity was infrequent east of aso caldera whereas fire events moderately occurred west of the caldera fire frequency in the eastern region rose abruptly at 13 5 ka and fire activity was most frequent in the last 5 ka while holocene fire frequency in the western area was similar to that of 32 30 ka the consistent presence of miscanthus grassland in combination with high fire activity east of aso caldera after 13 5 ka suggests that the miscanthus grassland was attributed to burning as a consequence of anthropogenic activities

distribution of helicity cape and shear in tropical cyclones abstract the previous study of helicity cape and shear in hurricane bonnie 1998 was extended to all eight tropical cyclones sampled by nasa during the convection and moisture experiments camex storms were categorized as having large or small ambient vertical wind shear with 10 m s 1 as the dividing line in strongly sheared storms the downshear mean helicity exceeded the upshear mean by a factor of 4 as in the previous study the helicity differences resulted directly from the tropical cyclone response to ambient shear with enhanced in up out flow and veering of the wind with height present downshear cape in strongly sheared storms was 60 larger downshear mean inflow near the surface and the depth of the inflow layer each were 4 times larger downshear at more than 30 of observation points outside the 100 km radius in the downshear right quadrant midlatitude empirical parameters indicated a strong likelihood of supercells no such points existed upshear in highly sheared storms much small

novae on venus geology classification and evolution 1 novae are radially fractured centers 100 300 km in diameter and 64 have been identified on venus dense radial fracturing and upraised topography are common and massive amounts of volcanism are seen in some novae are interpreted to be the result of updoming and fracturing of the surface due to interaction of mantle diapirs with the lithosphere and radial fracturing caused by dike emplacement we analyzed the topography and character of deformational and morphological structures of all 64 novae leading to a better understanding of their evolution and relation to diapir dynamics and their age we subdivided novae into four topographic classes 1 upraised 2 annular 3 flat and negative and 4 plateau like novae are located mostly in areas of regional rises and rift zones with a small number in the lowlands about one half the novae studied show association with rifts in some of these the rift troughs surround nova rises and form plateau like novae plateau like novae may predate postdate or form simultaneously with rifts our analysis generally confirms and updates previous models of novae evolution with the following geological factors being important 1 depth of the neutral buoyancy level of the rising mantle diapir 2 rheological characteristics of the overlying lithosphere 3 whether or not the visco plastic material above the diapir undergoes spreading and 4 the nature and influence of regional stress and rift structures these combined factors exert control on the direction of nova evolution and appear to determine the primary characteristics of nova such as topography tectonics and volcanism we found clear evidence for 1 the important role of dike swarm emplacement in the formation of radial patterns of novae and 2 the formation of concentric tectonic features during the relaxation stage of novae novae have multiple evolutionary stages and are long lived structures stratigraphic analysis of all 64 local areas showed a similarity in the sequence of regional geologic units we found that 40 3 of the novae population started to form before emplacement of regional plains with wrinkle ridges and that 11 3 completed their activity before this time 88 7 of the population of novae was active after regional plains formation in contrast to novae coronae activity was greatest before formation of regional plains which may be due to thickening of the lithosphere with time detailed structural analysis shows that novae evolution does not always lead to the formation of corona like features

mechanisms of faulting in and around caloris basin mercury 1 the distribution of faulting in and around the caloris basin on mercury provides constraints on the planet s early lithosphere and tectonic history by means of a series of finite element models we test a range of ideas regarding lithospheric structure surface loading and shallow flow proposed to account for early contractional features and younger extensional features on the basin floor as well as contractional tectonic features exterior to the basin early stage thrust faults within the basin are well matched by the stress field accompanying flexural subsidence in response to partial infilling of a broad basin floor while younger normal faulting can be the result of flexural uplift in response to later stage emplacement of an exterior annulus of smooth plains deposits a proposed scenario in which later stage inward flow of the lower crust induces uplift of the basin floor can under some conditions yield extension in the basin but not in a manner consistent with the observed distribution of normal faults thrust faulting on the exterior smooth plains can be the result of local subsidence accompanying the emplacement of these units but may also have been influenced by global contraction our results lead to the prediction that the gravity anomaly associated with the caloris basin and surroundings should consist of a central positive anomaly mascon and an annular gravity high separated by a ring of lower gravity gravity and topography measurements to be made by the messenger mission will provide a test of this prediction and more generally of the models developed here

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

evidence for young volcanism on mercury from the third messenger flyby during its first two flybys of mercury the messenger spacecraft acquired images confirming that pervasive volcanism occurred early in the planet s history messenger s third mercury flyby revealed a 290 kilometer diameter peak ring impact basin among the youngest basins yet seen having an inner floor filled with spectrally distinct smooth plains these plains are sparsely cratered postdate the formation of the basin apparently formed from material that once flowed across the surface and are therefore interpreted to be volcanic in origin an irregular depression surrounded by a halo of bright deposits northeast of the basin marks a candidate explosive volcanic vent larger than any previously identified on mercury volcanism on the planet thus spanned a considerable duration perhaps extending well into the second half of solar system history

evidence for basaltic volcanism on the moon within the past 100 million years the majority of basaltic volcanism on the moon occurred more than 3 billion years ago small mounded formations on the lunar nearside may be products of basaltic eruptions less than 100 million years ago suggesting a long decline of magmatic activity

life of a six hour hurricane hurricane claudette developed from a weak vortex in 6 h as deep convection shifted from downshear into the vortex center despite ambient vertical wind shear exceeding 10 m s 1 six hours later it weakened to a tropical storm and 12 h after the hurricane stage a circulation center could not be found at 850 hpa by aircraft reconnaissance at hurricane strength the vortex contained classic structure seen in intensifying hurricanes with the exception of 7 12 c dewpoint depressions in the lower troposphere upshear of the center these extended from the 100 km radius to immediately adjacent to the eyewall where equivalent potential temperature gradients reached 6 k km 1 the dry air was not present prior to intensification suggesting that it was associated with vertical shear induced subsidence upshear of the developing storm it is argued that weakening of the vortex was driven by cooling associated with the mixing of dry air into the core and subsequent evaporation and cold downdrafts evidence suggests that this mixing might have been enhanced by eyewall instabilities after the period of rapid deepening the existence of a fragile small but genuinely hurricane strength vortex at the surface for 6 h presents difficult problems for forecasters such a temporary hurricane in strongly sheared flow might require a different warning protocol than longer lasting hurricane vortices in weaker shear

estimation and mapping of hurricane turbulent energy using airborne doppler measurements abstract hurricane turbulent kinetic energy tke was computed using airborne doppler measurements from the noaa wp 3d tail radars and tke data were retrieved for a variety of storms at different stages of their life cycle the geometry of the radar analysis coupled with the relatively small beam resolution at ranges 8 km allowed for the estimation of subkilometer turbulent processes two dimensional profiles of tke were constructed and revealed that the strongest turbulence was generally located in convective regions such as the eyewall with magnitudes often exceeding 15 m2 s 2 and in the boundary layer with values of 5 10 m2 s 2 in the lowest kilometer a correlation analysis showed that the strong turbulence was generally associated with strong horizontal shear of vertical and radial wind components in the eyewall and strong vertical shear of horizontal wind in the boundary layer mean vertical profiles of tke decrease sharply above the hurricane boundary layer and level off at low magnitude for al

morphometric analysis of small scale lobate scarps on the moon using data from the lunar reconnaissance orbiter 1 prior to lunar reconnaissance orbiter lro the morphology and dimensions of only a limited number of lobate scarps all located near the equator within 21 had been characterized topography derived from lro camera stereo images and lunar orbiter laser altimeter lola ranging is used to measure the relief and analyze the morphology of previously known and newly detected low and high latitude lobate scarps the asymmetric profiles and maximum slopes on scarp faces 5 to 29 of lunar lobate scarps are similar to those of lobate scarps observed on mars and mercury scarp lengths range from 0 6 to 21 6 km mean 6 0 km median 4 4 km n 79 and measured relief ranges from 5 to 150 m mean 35 m median 20 m n 26 assuming a range of 20 to 40 for the fault plane dip estimated lower limits for the horizontal shortening s expressed by the lobate scarp thrust faults range from 10 to 410 m the range in s estimated for the lunar scarps is roughly an order of magnitude lower than estimates of s for lobate scarp thrust faults on mars and mercury the relatively small range of s estimated for the growing number of well characterized lunar scarps is consistent with a small amount of global contraction

gld100 the near global lunar 100 m raster dtm from lroc wac stereo image data 1 we derived near global lunar topography from stereo image data acquired by the wide angle camera wac of the lunar reconnaissance orbiter camera lroc system from polar orbit tracks the lroc wac provides image data with a mean ground resolution at nadir of 75 m pixel with substantial cross track stereo overlap wac stereo images from the one year nominal mission and the first months of the science mission phase are combined to produce a near global digital terrain model dtm with a pixel spacing of 100 m the global lunar dtm 100 m or gld100 it covers 79 s to 79 n latitudes 98 2 of the entire lunar surface we compare the gld100 with results from previous stereo and altimetry based products particularly with the lunar orbiter laser altimeter lola altimetry which is the current topographic reference for the moon we describe typical characteristics of the gld100 and based upon the comparison to the lola data set assess its vertical and lateral resolution and accuracy we conclude that the introduced first version of the stereo based gld100 is a valuable topographic representation of the lunar surface complementary to the lola altimetry data set further improvements can be expected from continuative investigations

volcanic eruptions on mid ocean ridges new evidence from the superfast spreading east pacific rise 17 19 s uniform sediment cover were recovered from lava that buries older faulted terrain the boundary in lava composition coincides with a change in depth to the top of an axial magma lens seismic reflector consistent with magmas from two separate reservoirs being erupted in the same event chemical compositions from throughout the area indicate that lavas with identical compositions can be emplaced in separate volcanic eruptions within individual segments a comparison of our results to global data on submarine mid ocean ridge eruptions suggests consistent dependencies of erupted volume activated fissure lengths and chemical heterogeneity with spreading rate consistent with expected eruptive characteristics from ridges with contrasting thermal properties and magma reservoir depths index terms 3035 marine geology and geophysics midocean ridge processes 8414 volcanology eruption mechanisms 8439 volcanology physics and chemistry of magma bodies 3655 mineralogy and petrology major element composition keywords lava flow chemical heterogeneity erupted volume lava morphology side scan sonar

asymmetric hurricane boundary layer structure from dropsonde composites in relation to the environmental vertical wind shear this study investigates the asymmetric structure of the hurricane boundary layer in relation to the environmentalverticalwind shearin theinner core region data from1878 gps dropsondesdeployed by research aircraft in 19 hurricanes are analyzed in a composite framework kinematic structure analyses based on doppler radar data from 75 flights are compared with the dropsonde composites shear relative quadrantmeancomposite analysesshow that boththekinematicandthermodynamic boundarylayerheight scalestend to decrease with decreasing radius consistent with previous axisymmetric analyses there is still a clear separation between the kinematic and thermodynamic boundary layer heights both the thermodynamic mixed layer and height of maximum tangential wind speed are within the inflow layer the inflow layer depth is found to be deeper in quadrants downshear with the downshear right dr quadrant being the deepest the mixed layer depth and height of maximum tangential wind speed are alike at the eyewall but are deeper outside in quadrants left of the shear the results also suggest that air parcels acquire equivalent potential temperature ue from surface fluxes as they rotate through the upshear right ur quadrant from the upshear left ul quadrant convection is triggered in the dr quadrant in the presence of asymmetric mesoscale lifting coincident with a maximum in ue energy is then released by latent heating in the downshear left dl quadrant convective downdrafts bring down cool and dry air to the surface and lower ue again in the dl and ul quadrants this cycling process may be directly tied to shear induced asymmetry of convection in hurricanes

extensive ash falls in and around the sea of japan from large late quaternary eruptions abstract five widespread ashes of late quaternary age have been recognized on land and also in deep sea sediments in and around the sea of japan all are favorable for determining the magnitude and type of the great eruptions and for establishing a quaternary chronology around japan accurate determination of refractive indices of volcanic glass shards and phenocrysts together with chemical data have enabled successful characterization of the tephra layers and correlation between land and sea of the five tephras two are alkalic and are the products of major eruptions of two korean volcanoes the baegdusan tomakomai ash b tm and the ulreung oki ash u oki the b tm ash is recognized at the top of most cores in the northern part of the sea of japan and also on hokkaido and the northern part of honshu where a reliable archeological age is given around the 11th century the u oki ash occurs between the kikai akahoya and aira tn ashes in cores from adjacent to the ulreung do to central honshu where three radiocarbon ages of around 9300 yr b p were obtained the other three tephras are subalkalic and are correlated with large scale eruptions producing voluminous pyroclastic flows and calderas in kyushu the kikai akahoya k ah aira tn at and aso 4 ashes the former two have been well described already but their fallout areas are partly revised in this manuscript the at ash is the most prominent marker recognized not only on land of japan but also in cores from the whole area of the sea of japan and part of the pacific ocean the airfall aso 4 ash simultaneous with the aso 4 pyroclastic flow eruption is also described it mantles very extensive areas and serves as an important time marker about 70 000 years ago

vegetation history after the late period of the last glacial age based on phytolith records in nangodani valley basin southern part of the aso caldera japan

modeling volcanic deformation in a regional stress field implications for the formation of graben structures on alba patera mars abundant grabens transect the volcano alba patera their complex geometry and formation mechanisms are still poorly understood tectonic processes and magmatic intrusions are responsible for these long surface features cross cutting relationships of the grabens show radial fractures that were formed during early stages and were progressively overprinted by concentric fractures on the mid and upper flanks of the volcano two modeling methods are used to understand the formation of the observed structures and to evaluate their implications for hidden subvolcanic processes surface deformation and fault arrangements predicted in finite element models are compared to the graben systems observed in viking images the orientation and position of the concentric grabens are found to be best reproduced by local crustal subsidence superimposed on a regional nw se oriented extension with decreasing magnitude from south to north in analogue sandbox models we also simulate surface structures of arrangements that almost perfectly mimic the observed lineaments on alba patera formation of the grabens spans a period on the order of a billion years suggesting long term geodynamic processes to be responsible for the subsidence of the central alba patera area the progressive change toward higher concentricity is likely resultant from an increase in density in the crust by accumulation of intrusive material and cooling thus causing subsidence of the region above this volcanic root

dike induced faulting in rift zones of iceland and afar geodetic data and field observations demonstrate that the emplacement of dikes in volcanic rift zones frequently generates normal faulting and graben subsidence at the earth9s surface elastic modeling of the vertical ground surface displacements above dikes and faults indicates that the extent of graben subsidence can be achieved only if fault slip extends virtually to or beyond the dike plane at depth a mechanical model that includes dikes and frictional faults shows that dike opening tends to compress and lock faults located to either side of the dike therefore slip extending into or beyond the dike cavity must occur either 1 on faults that intersect the dike near its top above the zone of dike induced compression or 2 on faults that slip ahead of the dike as it propagates laterally data from iceland indicate that slip occurred on deep faults that presumably slipped in advance of the laterally propagating dike

graben fissure systems in guinevere planitia and beta regio 264 312 e 24 60 n venus and implications for regional stratigraphy and mantle plumes detailed mapping in a 14 000 000 km 2 area of northwestern guinevere planitia and northern beta regio bounded by 264 312 e 24 60 n has revealed thousands of long extensional lineaments graben fissures and related fractures these can be grouped into radiating circumferential and linear systems thirty four radiating systems have been identified of which 16 have radii greater than 300 km and eight have radii greater than 1000 km twenty six linear straight systems with a length greater than 300 km have been distinguished of which six have a length greater than 1000 km linear systems are generally associated with rifts although some may represent distal portions of radiating systems in addition 19 circumferential systems some associated with coronae have been identified the distribution of each system is compared with the host geology in order to place the graben fissure systems in a regional stratigraphic framework the majority of systems are 1 younger than tesserae ridge belts and densely fractured plains 2 coeval with and in many cases define fracture belts 3 partially flooded by wrinkle ridged plains units and 4 older than smooth and lobate plains units and young rifts the inventory of radiating graben fissure systems that we catalogue represents a database of tectono magmatic centers that complements the centers defined using other criteria e g large volcanoes coronae and shield fields we have attempted to identify those systems that are underlain by dike swarms in order to evaluate their relationship to mantle plumes at least 11 of the radiating systems extend well beyond any central topographic uplift and are therefore interpreted to be underlain by dike swarms

extension and contraction within volcanically buried impact craters and basins on mercury orbital images of mercury obtained by the messenger spacecraft have revealed families of troughs interpreted to be graben on volcanic plains material that largely or completely buried preexisting craters and basins the graben are partially to fully encircled by rings of contractional wrinkle ridges localized over the rims of the buried impact features to form systems of associated contractional and extensional landforms most of the buried craters and basins with graben identified to date are located in the extensive volcanic plains that cover much of mercury s northern high latitudes the distinctive relationship between wrinkle ridges and graben in buried craters and basins on mercury is interpreted to be the result of a combination of extensional stresses from cooling and thermal contraction of thick lava flow units and compressional stresses from cooling and contraction of the planet s interior

flexural rotation of normal faults a conceptual model is proposed for the generation of low angle normal faults in metamorphic core complexes the model is based on three assumptions 1 the isostatic response to normal fault motion is of regional extent 2 when a fault segment is significantly rotated from the optimum angle of slip relative to the crustal stress field it is replaced by a new planar fault oriented in the optimum direction and 3 the fault cuts the entire upper crust and fault motion always nucleates in the same region at the base of the upper crust the stress field is considered to be uniform through the crust and the regional isostatic response of the crust to loads is computed using the thin plate flexure approximations active low angle normal faults are difficult to reconcile with rock mechanics theories earthquake focal mechanism studies and geochronologic results indicating rapid cooling of core complex rocks the model does not require active fault slip on low angle faults the flexural response to normal faulting is shown to be significantly affected by anelastic behavior of the crust and by loading due to sedimentation the anelastic response to large bending stresses results in significant reduction in the effective elastic rigidity of the upper crust this can explain the observed short wavelength of topographic response to normal fault loads the model results in 1 a nearly flat lying abandoned normal fault or detachment below slices of upper plate rocks and sedimentary infill 2 a strong contrast in metamorphic grade across the abandoned detachment 3 rapid movement of lower plate rocks from midcrustal depths to shallower depths these results are qualitatively in agreement with geologic observations for core complexes

evidence for intrusive activity on mercury from the first messenger flyby images from messenger s first flyby of mercury have shown convincing evidence for surface volcanism here we report on evidence in the new data for several features that are characterized by fractures and graben rare features on a planet dominated by contractional deformation that may be linked to intrusive activity these features include 1 a floor fractured crater interpreted to have been the site of laccolith like sill intrusions the feature is similar to some floor fractured craters on the moon and shows evidence for individual fractured dome like uplifts on the floor 2 a concentric complex of graben observed inside the peak ring on the floor of the 250 km diameter raditladi basin and associated with dark plains and possibly embayed by them the feature may represent an unusual type of floor fracturing associated with deeper intrusions and related ring dikes or cone sheets or the graben may instead be the product of non magmatic uplift of the basin floor 3 a large radial graben swarm pantheon fossae located near the center of the caloris basin thus far unique on mercury and characterized by hundreds of individual graben segments ranging from 5 km to 110 km in length in the nexus graben crosscut one another and produce a local polygonal pattern others curve away from the center as the nexus is approached two scales of graben length are observed the radius of the dense radially symmetric plexus of graben is 175 km and a few graben extend to greater radial distances to the north and southwest out to distances that intersect with a ring of generally concentric graben around the outer basin floor two width scales of graben are observed a large graben about 8 km wide emerges from the nexus and extends for 100 km most graben are less than half this width some graben walls appear cuspate with convex outward wall segments that resemble crater chain segments one crater chain with distinctive raised rims parallels nearby graben locally some graben appear in en echelon patterns and smaller graben sometimes show cross cutting superposition relationships abundant impact craters the most prominent being apollodorus and secondary crater clusters and chains are superposed on the graben system there is little evidence that craters greater than 5 km in diameter have been cut by a graben this relation implies that the graben swarm formed soon after the emplacement of the caloris floor plains these graben are interpreted to be the surface expression of a radial dike swarm emanating from a subsurface magma reservoir similar features in which the dikes contribute to a near surface stress field that favors radial graben are known on the earth venus and mars the location of pantheon fossae in the center of the caloris basin suggests that formation of the radial graben structure is linked to basin evolution

extensional troughs in the caloris basin of mercury evidence of lateral crustal flow thirty years ago mariner 10 revealed extensional troughs that form giant polygons in the floor material of the caloris impact basin mercury the polygonal troughs occur in the interior of the basin and overprint wrinkle ridges formed in an earlier stage of compression in contrast lunar and martian basins exhibit extensional troughs that are circumferential and confined to basin margins loading by basin filling material can explain the extensional and compressional features seen in deformed lunar and martian basins but not the existence of the caloris polygonal troughs here we suggest that the caloris troughs formed from late stage basin uplift and extension due to lateral flow of a relatively thick crust toward the basin center if such lateral flow occurs the resulting timing location and magnitude of the extensional stresses predicted by our model are consistent with those inferred from the polygonal troughs these results are not strongly dependent on the degree of lateral flow or the assumed crustal rigidity for a dry plagioclase rheology and likely radiogenic heat fluxes the crustal thickness around caloris is 90 140 km similar late stage uplift and extension probably do not occur in basins on the moon and mars because their crusts are too thin to allow analogous lateral flow

90 000 year phytolith records from caldera rim to western foot of aso volcano japan implications for vegetation history since catastrophic eruption abstract vegetation history after the aso 4 ignimbrite eruption 89 ka has been reconstructed using phytolith records obtained from three tephra sections from caldera rim to the western foot of aso volcano southwestern japan the ca 90 000 year vegetation transitions vary between these sites and elevations at the northern caldera rim 800 900 m asl sparse vegetation composed of sasa sect crassinodi cool temperate dwarf bamboo and zoysia was considered to be established within 1000 years after the catastrophic aso 4 eruption the sasa grassland dominated by sasa sect crassinodi existed continuously at the northeastern caldera rim between 89 and 13 5 ka whereas pleioblastus sect nezasa warm temperate dwarf bamboo andropogoneae including miscanthus japanese pampas grass and zoysia existed in the sasa grassland between 66 and 30 ka although sasa grassland existed after 13 5 ka pleioblastus dwarf bamboo became a constituent of the grassland around 8 ka and continued flourishing until the present on the western slope ca 150 m asl sparse vegetation existed prior to 55 ka after a large outburst flood generated by a breach of caldera rim of intra caldera lake ca 89 72 ka the vegetation after 55 ka was dominated by grassland accompanied with moderate amounts of trees zoysia prevailed from about 55 to 40 ka although sasa was predominant during the period of 40 5 ka the sasa grassland containing andropogoneae pampas grass declined around 5 ka and pleioblastus dwarf bamboo became a constituent of the grassland the pleioblastus grassland including miscanthus japanese pampas grass paniceae and trees lauraceae etc continued to the present at the western foot of the volcano 100 m asl zoysia grassland became established after the large outburst flood the grassland gradually declined from ca 60 ka and almost disappeared around 40 ka instead sasa dwarf bamboo grassland which accompanied pleioblastus dwarf bamboo increased after 60 ka the sasa grassland accompanying sparse trees continued but decreased after 13 1 ka miscanthus grassland occurred after 29 ka and flourished especially in the last 8 ka the consistent presence of miscanthus grassland for 29 000 years may be related to frequent fire episodes due to human activities including burning at the low elevation of the western foot of aso volcano

mesoscale and convective structure of a hurricane rainband abstract the mesoscale thermodynamic kinematic and radar structure of a hurricane floyd rainband observed on 7 september 1981 is presented data are from 26 aircraft passes through the rainband from 150 to 6400 m a composite technique which presents rainband structure as a function of distance from the storm circulation center reveals inflow from the outer edge of the band and a partial barrier to this flow below 3 km in the direction parallel to rainband orientation radar reveals cellular reflectivity structure on the upwind and central portions of the rainband the frequency of cellular precipitation decreases in favor of stratiform precipitation further downwind as the band spirals gradually towards the eyewall in the radial direction a decrease of 12 k in e is observed across the rainband in the subcloud layer convective scale up and downdrafts that are associated with cellular reflectivity structure are hypothesized to be responsible for the thermodynamic modification of the cloud and subc

emplacement and tectonic deformation of smooth plains in the caloris basin mercury abstract messenger s first flyby of mercury provided the first complete view of the caloris basin and its interior smooth plains multispectral imaging shows that the interior plains are spectrally distinct from surrounding terrain with a reflectance about 15 20 higher and a steeper spectral slope than the global average the caloris basin rim massifs and hummocky material in contrast have lower reflectance and a shallower spectral slope than the global average and extend around the entire basin isolated relatively red patches along the margins of caloris each surround irregularly shaped scalloped edged rimless depressions that are interpreted to be volcanic vents some with associated pyroclastic deposits a nearly continuous annulus of smooth plains exterior to the basin displays spectral characteristics that contrast sharply with those of the basin interior smooth plains the exterior smooth plains are lower in reflectance and spectrally similar to the caloris rim massifs and the hummocky materials the rims and floors of larger impact craters in the interior plains expose low reflectance material there is widespread evidence of contractional and extensional tectonic deformation of the caloris interior smooth plains a set of linear radial graben pantheon fossae radiates outward from a zone near the basin center and some of these graben extend to and intersect a set of generally basin concentric graben distributed along the outer margin of the caloris basin floor the average areal extensional strain expressed by the mapped system of graben is 0 08 wrinkle ridges also deform the interior smooth plains and predate both basin radial and basin concentric graben the average areal contractional strain expressed by the mapped wrinkle ridges is 0 07 the density of wrinkle ridges on the western interior smooth plains is less than on the eastern interior plains in contrast to the more even distribution of graben a similar difference is seen between the density of wrinkle ridges on the western and eastern exterior smooth plains with far fewer wrinkle ridges per unit area on the western annular plains superposition relations spectral contrast and the occurrence of volcanic vents and possible pyroclastic deposits all support a volcanic origin for the caloris interior plains crater counts indicate that the caloris exterior plains and hummocky material are younger than the caloris rim and interior plains and are therefore also likely volcanic in origin the contrast in spectral properties between the interior and exterior plains indicates a difference in the composition of the two expanses of volcanic material models for extensional tectonic deformation of the caloris basin interior inferred from the distribution of graben viewed by mariner 10 must be reevaluated to account for the discovery of pantheon fossae

a composite analysis of the core of a mature hurricane abstract an unusually large quantity of aircraft data was obtained within the core of hurricane frederic 1979 these data are combined with powell s surface observations of the same storm and composited the data are sufficiently abundant to allow three dimensional kinematic analyses of poorly documented parameters such as divergence and vertical velocity patterns of related but independently determined parameters such as radar reflectivities cloud water concentrations and kinematically derived vertical velocities agree well diagnostic budget analyses of sensible heat and angular momentum are computed for the storm inflow layer the analysis provides a unique quantitative picture of the inflow layer of a mature asymmetric hurricane the depth of the inflow layer decreases with decreasing radius as a result surface drag coefficients derived from angular momentum budgets do not appear to increase with increasing wind speed the sensible heat budget shows downward subgrid scale heat fluxes near cloud

90 000 year phytolith record from tephra section at the northeastern rim of aso caldera japan abstract vegetation history during the last 90 000 years has been reconstructed using the phytolith record obtained from a tephra section located at the northeastern rim of aso caldera southwestern japan the phytolith assemblage from the section revealed that grassland vegetation dominated by gramineae consistently occurred for 90 000 years sparse vegetation composed of sasa sect crassinodi cool temperate dwarf bamboo and zoysia lawn was considered to be established within 1000 years after the catastrophic aso 4 eruption 89 ka the sasa grassland dominated by sasa sect crassinodi existed continuously at the northeastern caldera rim between 89 and 13 5 ka the dominance of sasa sect crassinodi in the grassland suggests that the aso caldera rim during the period was under a cooler and drier climate plants other than sasa dwarf bamboo declined during the period of 75 66 ka mis4 whereas pleioblastus sect nezasa warm temperate dwarf bamboo andropogoneae pampas grass and zoysia existed in the sasa grassland between 66 and 30 ka mis3 during the period from 30 to 13 5 ka mis2 corresponding to the last glacial maximum lgm phytoliths from plants other than sasa dwarf bamboo and fern are only present in small numbers suggesting that they declined in response to a cool climate during the lgm sasa grassland which had continued since 89 ka existed after 13 5 ka at the northeastern rim of aso caldera in the earlier stage of the holocene phytoliths of sasa sect crassinodi and sasa sect sasa dominated but pleioblastus dwarf bamboo became a constituent of the grassland around 8 ka the proportion of pleioblastus dwarf bamboo mainly pleioblastus sect nezasa in the grassland increased and continued flourishing until the present although sasa gradually decreased in addition arboreal phytoliths were recognized at several holocene horizons these phenomena indicate that grassland vegetation composed mainly of sasa and pleioblastus dwarf bamboos with sparse trees dominated at the northeastern rim of the aso caldera in holocene time

holocene vegetation history based on phytolith records in asodani valley northern part of the aso caldera japan abstract vegetation history during the holocene has been reconstructed using phytolith records obtained from three tephra sections in the asodani valley basin northern part of aso caldera southwestern japan the topography of the asodani valley basin is divided into four types somma caldera rim and pyroclastic flow plateau caldera wall caldera floor and post caldera central cone slope the holocene vegetation transitions in the basin vary between these topographic types at the northern caldera rim sasa cool temperature dwarf bamboo grassland existed prior to 8 ka and thereafter pleioblastus warm temperature dwarf bamboo grassland dominated to the present at the steep caldera wall forest with understory of bambusoideae plants sasa and pleioblastus existed during the holocene and mixed forests composed of evergreen trees deciduous trees and conifers appeared after 6 ka on the post caldera central cone slope grassland vegetation composed of sasa existed prior to 10 2 ka and miscanthus pampas grass grassland with sparse trees established around 13 ka and flourished in the last 4 ka the center of the asodani valley was occupied by the last intra caldera lake prior to 8 9 ka and thereafter changed to swampy and fluvial environments phragmites occurred continuously in and around the intra caldera lake and the subsequent marshes and swamps in the last 11 4 ka the difference of vegetation transition in the holocene between topographic types can be explained as difference of human activities in and around the aso caldera grassland dominated by sasa pleioblastus and miscanthus occurred on pyroclastic flow plateau around the caldera and on the central cone slope which were strongly affected by human activities including burning for a long time and forest with understory bambusoideae plants was preserved on the caldera wall which is unapproachable because of the steep topography

floor fractured craters in mare smythii and west of oceanus procellarum implications of crater modification by viscous relaxation and igneous intrusion models endogenic modification in lunar floor fractured craters can constrain spatial variations in early lunar conditions the nature of these constraints however depends on the assumed mecha nism of crater modification for viscous relaxation the extent of crater modification depends on the surrounding crustal viscosity and thus provides loose constraints on the history of crustal heat ing within a region for igneous intrusion models the extent of crater modification reflects mag matically driven deformation and can be inverted to estimate both local magma pressure and intru sion depth both models indicate clear differences between regional conditions at mare smythii and in the highlands west of oceanus procelm the uniformly shallow crater depths in mare smythii probably indicate a long lived period of extreme crater relaxation whereas the wide range of modified crater depths in the western highlands suggest a much shorter period of partial crater relaxation for comparable relaxation times the average viscosity derived for mare smythii is over 10 times lower than the average viscosity inferred for the western highlands alternatively if modification reflects deformation over crater centered laccolithlike intrusions the derived magma pressures indicate a broad uniform magma source beneath mare smythii whereas the spatial vari ation of estimated magma pressures in the western highlands suggests the presence of several smaller magma sources the derived intrusion depths are partly a function of crater size but range from 1 to 10 km in depth for both regions and may be slightly greater on average in the western highlands while both viscous relaxation and igneous intrusions can explain the modification of individual craters the regional variations in these derived modification conditions also allow fur ther testing of each modification model in particular the correlation of the lowest viscosities or the longest relaxation times with the smallest craters in both mare smythii and the western high lands seems inconsistent with crater modification by the relaxation mechanism the onset of total relaxation at progressively smaller topographic wavelengths over time might produce such a trend in mare smythii but total relaxation cannot be invoked for the western highlands where many large craters still preserve significant fractions of their initial relief in addition the relaxation of the smallest craters in both regions suggests the presence of exceptionally high near surface ther mal gradients 150 200 k km since the observed regional variations in crater modification can be easily attributed to variations in magma pressure as a function of mantle topography we con clude that crater floor fracturing in both regions is more consistent with the igneous intrusion mechanism than with viscous relaxation during a crustal heating event

constraints on the depth and variability of the lunar regolith knowledge of regolith depth structure is important for a variety of studies of the moon and other bodies such as mercury and asteroids lunar regolith depths have been estimated using morphological techniques i e quaide and oberbeck 1968 shoemaker and morris 1969 crater counting techniques shoemaker et al 1969 and seismic studies i e watkins and kovach 1973 cooper et al 1974 these diverse methods provide good first order estimates of regolith depths across large distances tens to hundreds of kilometers but may not clearly elucidate the variability of regolith depth locally 100 m to km scale in order to better constrain the regional average depth and local variability of the regolith we investigate several techniques first we find that the apparent equilibrium diameter of a crater population increases with an increasing solar incidence angle and this affects the inferred regolith depth by increasing the range of predicted depths from 7 15 m depth at 100 m equilibrium diameter to 8 40 m at 300 m equilibrium diameter second we examine the frequency and distribution of blocky craters in selected lunar mare areas and find a range of regolith depths 8 31 m that compares favorably with results from the equilibrium diameter method 8 33 m for areas of similar age 2 5 billion years finally we examine the utility of using clementine optical maturity parameter images lucey et al 2000 to determine regolith depth the resolution of clementine images 100 m pixel prohibits determination of absolute depths but this method has the potential to give relative depths and if higher resolution spectral data were available could yield absolute depths

buoyancy of convective vertical motions in the inner core of intense hurricanes part ii case studies abstract this is the second of two papers on the buoyancy of convective vertical motions in the inner core of intense hurricanes this paper uses extensive airborne radar dropwindsonde and flight level observations in hurricanes guillermo 1997 and georges 1998 to illustrate typical azimuthal distribution of buoyant convection and demonstrate that the low level eye can be an important source region for buoyant eyewall convection in both hurricanes eyewall vertical velocity and radar reflectivity are asymmetric and exhibit persistent relationships with the direction of the environmental vertical wind shear mesoscale vertical motions exhibit a wavenumber 1 structure with maximum ascent downshear and weak descent upshear the mesoscale reflectivity maxima are located left of shear buoyant eyewall updraft cores and transient convective scale reflectivity cells are predominantly downshear and left of shear most eyewall downdraft cores that transport significant mass downward are located upshear nega

on the origin of graben and ridges within and near volcanically buried craters and basins in mercury s northern plains 1 images of mercury s northern volcanic plains taken by the messenger spacecraft reveal a large number of buried impact craters and basins discernible by wrinkle ridge rings that overlie their rims many of these ghost craters and basins contain interior graben of diverse widths and orientations here we use finite element models to test a variety of mechanisms for the formation of these graben and ridges results show that graben are best explained by cooling of large thicknesses of flood lavas within the craters and basins conservation of surface area during cooling induces the required extensional stress state in contrast the development of wrinkle ridge rings is best explained as the result of cooling and contraction of mercury s interior during which a reduction in mercury s surface area led to a compressional state of stress the critical factor in determining where large graben form is the thickness of the youngest cooling unit the topmost sequence of lavas that cooled coevally a thicker cooling unit leads to a deeper initiation of normal faulting wider graben floors consistent with observations the widest graben are predicted to occur where pooled lavas were thickest and no graben are predicted within generally thinner plains outside of major craters observed concentrically oriented graben can be explained by variations in the thickness of the youngest cooling unit in contrast none of the basin uplift mechanisms considered including isostatic response to crater topography inward flow of the lower crust or exterior loading by volcanic plains can account for concentrically oriented graben

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

tropical cyclone motion and evolution in vertical shear abstract the motion and the evolution of tropical cyclone like vortices in an environmental flow with vertical shear are investigated using a baroclinic primitive equation model the study focuses on the fundamental dynamics of a baroclinic vortex in vertical shear the influence of vortex structure and the role of diabatic heating the results show that the initial response of the vortex to the vertical shear is to tilt downshear as soon as the tilt develops the upper level anticyclonic and lower level cyclonic circulations begin to interact with each other as a result of these interactions the tilted axis of the vortex reaches a stable state after an initial adjustment which varies with the structure of the vortex its environmental flow shear and the cumulus convective heating the motion of an adiabatic vortex in vertical shear is controlled by both the steering of the environmental flow and vertical coupling mechanisms most of the vortices move with the environmental flow at about 650 hpa or

mechanics of graben formation in crustal rocks a finite element analysis small 1 10 km wide grabens are ubiquitous tectonic structures that have been observed on the surfaces of all the terrestrial planets and satellites in spite of their frequent occurrence there is no fundamental understanding of how they form other than that they are characteristic of extensional terranes this paper examines the mechanics of the initial stages of graben formation and demonstrates that the configuration of a pair of antithetically dipping normal faults a graben is the energetically most favorable fault configuration in elastic brittle rocks subjected to pure extension a corollary to this hypothesis is that the occurrence of synthetic normal faults is indicative of a stress field other than purely extensional or of nonhomogeneous characteristics of the rock the analysis proceeds by computing the stress field in the vicinity of a single initial normal fault using a two dimensional finite element model it is shown that slip on this fault substantially lowers the proximity to failure of the surrounding rocks except for two small regions one near the surface of the downthrown block and the other near the fault tip the region on the downthrown block is located a horizontal distance from the initial fault slightly less than the fault s depth the proximity to failure actually increases here and a secondary fault develops an antithetic secondary fault would link this region with the other failure zone near the fault tip to demonstrate the preference for antithetic secondary faults more rigorously we show that this fault configuration results in a smaller total strain energy than the synthetic configuration in addition a two layer model is used to show that the graben s width is only weakly dependent upon the presence of mechanically distinct layers in the crust both weak over strong and strong over weak configurations are investigated the depth of the initial fault and the thickness of the top layer are varied and the width of the resulting graben is evaluated by computing the distance between the initial fault and the region of highest proximity to failure near the surface this analysis indicates that the depth of the initial fault is the major factor controlling graben width

igneous dikes on mars revealed by mars orbiter laser altimeter topography the origin of martian grabens has remained controversial for decades given the nonuniqueness of graben morphology and conflicting interpretations of dike induced or faultingbased formation processes we use measurements from the mars orbiter laser altimeter to identify the characteristic topographic signature at the surface of an igneous dike beneath a martian graben our results suggest that this subtle but diagnostic signature can be used to test competing interpretations of the formation of grabens and associated fissures and collapse depressions

strain at radially fractured centers on venus 1 radially fractured centers rfcs on venus are distinctive 100 km long radiating systems of graben fissures and fractures arranged around a central topographic high we use cycle 1 and cycle 3 magellan images to determine the depths and wall dip angles of several large radial graben using two different methods at four rfcs becuma mons didilia corona h uraru corona and pavlova corona we record graben depths of 0 3 0 9 km and mean wall dip angles of about 36 which we interpret as a primary talus slope rather than a fault plane using the calculated depths and a more realistic fault dip of 60 we find extension of between 0 5 and 1 km on graben between about 5 and 10 km wide we use this extension to estimate the hoop strain at each rfc maximum measured strains on the flanks are typically between 1 and 4 and may be up to 7 toward the center we conclude that this strain is too large to be explained by current plume related uplift models and also by magma chamber inflation we conclude that dikes are probably responsible for the majority of the strain at the large radial graben

geology of grimaldi basin on the moon evidence for volcanism and tectonism during the copernican period abstract the grimaldi basin centered at 5 2 s 68 6 w is a 400 km diameter highly degraded pre nectarian double ring impact structure on the moon located near the western edge of the oceanus procellarum hyperspectral data from moon mineralogy mapper m3 feo estimates from kaguya lunar multiband imager mi data and tio2 estimates from wac 321 415 nm ratio have been used to study the compositional make up of the grimaldi mare basalt additionally morphological studies and crater chronology have been carried out using moderate to very high resolution images from lunar reconnaissance orbiter lro to decipher the geological evolution of the grimaldi basin mare grimaldi are dominantly composed of clino pyroxenes with olivine and or of feldspathic mixing with lateral as well as depth wise variations in composition in the south central part the basin experienced copernican aged volcanism 700 ma ago resulting in the formation of olivine bearing basalts with high feo and tio2 content cross cutting of small copernican craters by fresh wrinkle ridges and lobate scarps has been observed at several places in the basin suggesting that tectonic activities occurred in the basin within the past 50 ma 1 ga thus similar to the oceanus procellarum region grimaldi basin was also geologically active during the copernican period

evidence for recent and ancient faulting at mare frigoris and implications for lunar tectonic evolution abstract nearside basin related extensional tectonism on the moon was thought to have ended by about 3 6 billion years ago and mare basin localized contractional deformation ended by about 1 2 billion years ago lunar reconnaissance orbiter camera lroc high resolution 50 200 cm pixel images show the moon s surface in unprecedented detail and have enabled us to find many previously unidentified tectonic landforms forcing a re assessment of our views of tectonism in the maria the morphology and stratigraphic relationships of these newly identified populations of tectonic landforms imply a more complex and longer lasting history of deformation we selected mare frigoris as an ideal location to perform a mapping survey where excellent imaging conditions abundant tectonic landforms and restricted mascon allow us to unravel the mare s tectonic evolution similar to previous surveys we find that tectonism in the eastern portion of mare frigoris was controlled by ancient mascon induced flexure in the western portion however we identify a parallel set of ancient compressional wrinkle ridges across the mare that is inconsistent with an origin by mare basin centric mascon flexure or influence from the mare imbrium mascon instead our results imply an ancient regional non isotropic stress field over western mare frigoris we also identify young wrinkle ridges and show that they have likely been active within the last 1 billion years and some ridges as recently as within 40 million years finally we identify a 300 km long series of lobate scarps coincident with one of the shallow moonquakes recorded during apollo and use geodetic strain from the mapped global population of young lobate scarps to predict a level of seismicity consistent with the shallow moonquakes recorded during apollo in tandem with similarly young lobate scarps and small graben as well as recorded shallow moonquakes these young wrinkle ridges imply that some tectonism in and around mare frigoris has occurred in the geologically recent past and likely still continues today

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

recent extensional tectonics on the moon revealed by the lunar reconnaissance orbiter camera on the moon extensional tectonic features have only been observed close to the influence of the mare basalt filled basins and floor fractured craters analysis of lunar reconnaissance orbiter camera images reveals several potentially very young extensional tectonic features in the farside highlands implying that extensional stresses may locally exceed compressional ones

tectonics and volcanism of eastern aphrodite terra venus no subduction no spreading eastern aphrodite terra a deformed region with high topographic relief on venus has been interpreted as analogous to a terrestrial extensional or convergent plate boundary however analysis of geological and structural relations indicates that the tectonics of eastern aphrodite terra is dominated by blistering of the crust by magma diapirs the findings imply that within this region vertical tectonism dominates over horizontal tectonism and consequently that this region is neither a divergent nor a convergent plate boundary

volcanic rifting at martian grabens 1 a large fraction of surface extension on mars occurred at segmented grabens having width length ratios akin to oceanic rifts on earth association with volcanic landforms such as pit craters clearly suggests interconnection between tectonic and magmatic processes a martian rift evolution model is proposed on the basis of new geomorphological and structural interpretations of imagery high resolution digital elevation models dems scaled experimental modeling and three dimensional boundary element modeling of magmatic and tectonic processes and a comparison with terrestrial rifts the dems were obtained from mars observer laser altimeter viking orbiter stereo images or a combination of both comparison of terrestrial rifts included afar iceland and the east pacific rise the ambient extensional stress field induced by regional body forces is combined at depth with decompression melting and mantle plume thermal anomaly resulting in emplacement of elongated magma reservoirs along the grabens injection of dikes above the reservoirs and flood basalt eruption result in a reservoir underpressurization of up to hundreds of mpa and induces surface collapse each collapse event is associated with an eruption of volcanic volumes akin to those of individual flow eruptions in large terrestrial igneous provinces the geometry and mechanisms of graben formation and surface collapse are described and used to infer reservoir depth and width we conclude from this study that giant dike swarms akin to typical giant terrestrial dike swarms are unlikely to underlie the volcanic martian grabens on the basis one graben one dike rather every volcanic graben segment appears to own a local dike swarm perhaps analogous to the dike swarms in the icelandic fissure zones index terms 5475 planetology solid surface planets tectonics 8149 5480 planetology solid surface planets volcanism 8450 6225 planetology solar system objects mars 8121 tectonophysics dynamics convection currents and mantle plumes 8010 structural geology fractures and faults keywords rifting graben pit crater magma chamber dyke

extracting accurate and precise topography from lroc narrow angle camera stereo observations abstract the lunar reconnaissance orbiter camera lroc includes two identical narrow angle cameras nac that each provide 0 5 to 2 0 m scale images of the lunar surface although not designed as a stereo system lroc can acquire nac stereo observations over two or more orbits using at least one off nadir slew digital terrain models dtms are generated from sets of stereo images and registered to profiles from the lunar orbiter laser altimeter lola to improve absolute accuracy with current processing methods dtms have absolute accuracies better than the uncertainties of the lola profiles and relative vertical and horizontal precisions less than the pixel scale of the dtms 2 5 m we computed slope statistics from 81 highland and 31 mare dtms across a range of baselines for a baseline of 15 m the highland mean slope parameters are median 9 1 mean 11 0 standard deviation 7 0 for the mare the mean slope parameters are median 3 5 mean 4 9 standard deviation 4 5 the slope values for the highland terrain are steeper than previously reported likely due to a bias in targeting of the nac dtms toward higher relief features in the highland terrain overlapping dtms of single stereo sets were also combined to form larger area dtm mosaics that enable detailed characterization of large geomorphic features from one dtm mosaic we mapped a large viscous flow related to the orientale basin ejecta and estimated its thickness and volume to exceed 300 m and 500 km 3 respectively despite its 3 8 billion year age the flow still exhibits unconfined margin slopes above 30 in some cases exceeding the angle of repose consistent with deposition of material rich in impact melt we show that the nac stereo pairs and derived dtms represent an invaluable tool for science and exploration purposes at this date about 2 of the lunar surface is imaged in high resolution stereo and continued acquisition of stereo observations will serve to strengthen our knowledge of the moon and geologic processes that occur across all of the terrestrial planets

modeling of grabens extending above evaporites in canyonlands national park utah abstract grabens in canyonlands national park utah began extending above a layer of evaporites when the colorado river cut through the overburden two dimensional finite element models simulate the effects of geometry and rock properties on graben configuration and spacing only those models having a progressively increasing slope or no slope mimicked the natural upslope graben propagation typical rock properties produced the most realistic fault patterns an initial friction angle of 31 a cohesion of 1 mpa and strain weakening comprising cohesion loss and decrease of friction angle to 26 a tensile stress limit narrowed the grabens and reproduced the vertical upper portion of the natural faults the viscous salt resisted overburden spreading and controlled its rate modeled grabens spread at typical rates of 1 2 mm a 1 for a salt viscosity of 1 10 18 pa s and the entire system strained at rates from 6 0 10 14 s 1 to 0 5 10 14 s 1 the faults bounding a graben formed nearly simultaneously at the top surface and propagated downward salt rose beneath the grabens as reactive diapirs overburden adjacent to the canyon flexed as salt was expelled and formed an arching horst and graben a corresponding horst has been found in the field the model results scale to larger dimensions except for the steep upper part of the faults reduced dimensions create vertical or no faults

a 90 000 year tephrostratigraphic framework of aso volcano japan abstract a detailed 90 000 year tephrostratigraphic framework of aso volcano southwestern japan has been constructed to understand the post caldera eruptive history of the volcano post caldera central cones were initiated soon after the last caldera forming pyroclastic flow eruption 90 ka and have produced voluminous tephra and lava flows the tephrostratigraphic sequence preserved above the caldera forming stage deposits reaches a total thickness of 100 m near the eastern caldera rim the sequence is composed mainly of mafic scoria fall and ash fall deposits but 36 silicic pumice fall deposits are very useful key beds for correlation of the stratigraphic sequence explosive silicic pumice fall deposits that fell far beyond the caldera have occurred at intervals of about 2500 years in the post caldera activity three pumice fall deposits could be correlated with lava flows or an edifice in the western part of the central cones although the other silicic tephra beds were erupted at unknown vents which are probably buried by the younger products from the present central cones most of silicic eruptions produced deposits smaller than 0 1 km 3 but bulk volumes of two silicic eruptions producing the nojiri pumice 84 ka and kusasenrigahama pumice kpfa 30 ka were on the order of 1 km 3 vei 5 the largest pyroclastic eruption occurred at the kusasenrigahama crater about 30 ka this catastrophic eruption began with a dacitic lava flow and thereafter produced kpfa 2 2 km 3 total tephra volume in the past 90 000 years is estimated at about 18 1 km 3 dense rock equivalent dre whereas total volume for edifices of the post caldera central cones is calculated at about 112 km 3 which is six times greater than the former therefore the average magma discharge rate during the post caldera stage of aso volcano is estimated at about 1 5 km 3 ky which is similar to the rates of other quaternary volcanoes in japan

a numerical study of hurricane erin 2001 part ii shear and the organization of eyewall vertical motion a high resolution numerical simulation of hurricane erin 2001 is used to examine the organization of vertical motion in the eyewall and how that organization responds to a large and rapid increase in the environmental vertical wind shear and subsequent decrease in shear during the early intensification period prior to the onset of significant shear the upward motion in the eyewall was concentrated in small scale convective updrafts that formed in association with regions of concentrated vorticity herein termed mesovortices with no preferred formation region around the eyewall asymmetric flow within the eye was weak as the shear increased an azimuthal wavenumber 1 asymmetry in storm structure developed with updrafts tending to occur on the downshear to downshear left side of the eyewall continued intensification of the shear led to increasing wavenumber 1 asymmetry large vortex tilt and a change in eyewall structure and vertical motion organization during this time the eyewall structure was dominated by a vortex couplet with a cyclonic anticyclonic vortex on the downtilt left downtilt right side of the eyewall and strong asymmetric flow across the eye that led to strong mixing of eyewall vorticity into the eye upward motion was concentrated over an azimuthally broader region on the downtilt side of the eyewall upstream of the cyclonic vortex where low level environmental inflow converged with the asymmetric outflow from the eye as the shear diminished the vortex tilt and wavenumber 1 asymmetry decreased while the organization of updrafts trended back toward that seen during the weak shear period based upon the results for the erin case as well as that for a similar simulation of hurricane bonnie 1998 a conceptual model is developed for the organization of vertical motion in the eyewall as a function of the strength of the vertical wind shear in weak to moderate shear higher wavenumber asymmetries associated with eyewall mesovortices dominate the wavenumber 1 asymmetry associated with the shear so that convective scale updrafts form when the mesovortices move into the downtilt side of the eyewall and dissipate on the uptilt side under strong shear conditions the wavenumber 1 asymmetry characterized by a prominent vortex couplet in the eyewall dominates the vertical motion organization so that mesoscale ascent with embedded convection occurs over an azimuthally broader region on the downtilt side of the eyewall further research is needed to determine if these results apply more generally

small scale lunar graben distribution dimensions and formation processes abstract the lunar reconnaissance orbiter camera lroc is the first instrument to provide widespread coverage with a range of incidence angles at the resolution required to detect small scale landforms a sample n 238 of globally distributed small scale graben average 26 m wide and 179 m long when dividing the population into those located within mare and highland regions we observe that graben located within mare tend to be narrower shorter and more irregularly spaced than those in highland terrane for graben associated with contractional landforms those in mare are smaller in width and length than those in highlands the same is true for graben independent of contractional landforms assuming a simple geometry widths of mare graben associated with scarps or ridges are used to estimate the minimum depth range to a mechanical discontinuity e g base of the regolith resulting in values of 4 48 m these values are similar to the ranges estimated for regolith thickness from previous workers using apollo 14 seismic data 3 9 8 5 m crater counting techniques 8 33 m crater morphology techniques 2 5 9 m and crater blockiness 8 31 m widths of highland graben yield minimum depths of faulting of 209 296 m while this range agrees well with models for regolith production an older surface will have thicker regolith this estimate likely does not represent the thickness of a mechanical unit due to the fragmented nature of the highland crust it does not provide a defining boundary between bedrock and regolith spacing of mare graben not associated with contractional landforms is used to estimate maximum local mare unit thickness for two graben groups 190 m for posidonius and 296 m for vitello maximum graben ages range from late eratosthenian to early copernican based on superposed and crosscut crater ages with a group of graben deforming ejecta from copernicus crater data presented here provide further evidence of a globally distributed young small scale graben population that has formed as a result of localized extension either from flexural bending or dilation due to contractional faulting or volcanic uplift indicating a significant level of recent geologic activity

small graben in the southeastern ejecta blanket of the lunar copernicus crater implications for recent shallow igneous intrusion on the moon abstract dozens of linear graben that are about 10 400 m wide and less than 1 km long are recognized in the southeastern continuous ejecta deposits of copernicus supporting that copernican aged tectonism has occurred on the moon fault geometry analysis suggests that the bounding faults of the graben have formed within the ejecta deposits the graben are exclusively located on a local high relief area but they are not formed by mass wasting because the topographic slope is substantially less than the repose angle of typical lunar materials and no other extensional structures are visible on similar high relief areas at the continuous ejecta deposits of copernicus the orientations of the graben all point to the center of copernicus but the topography of copernicus is little compensated after formation suggesting that the graben were not caused by possible crustal isostatic readjustment this graben system is one of the three examples on the moon that were interpreted to be caused by shallow igneous intrusions in the format of laccoliths the currently available grail gravity data have a lower spatial resolution than the size of the graben so the gravity data cannot resolve the hypothesized sub kilometer scale laccoliths beneath the graben while laccolith intrusion to a depth of about 80 m is required to explain the formation of this graben system the laccolith intrusion scenario is not consistent with the geological context of the graben a compressional structure is visible close to the graben system and their spatial configuration and similar preservation states are consistent with being generically related a close examination of the other two sets of graben that were also interpreted to have no associated compressional structures actually reveals spatially related lobate scarps and wrinkle ridges in the vicinity therefore shallow igneous intrusion is not plausible or necessary to explain to formation of copernican aged graben on the moon and they are most likely formed by the late stage global contraction of the moon

low level thermodynamic kinematic and reflectivity fields of hurricane guillermo 1997 during rapid intensification abstract from 0600 utc 2 august to 1200 utc 3 august hurricane guillermo 1997 deepened by 54 hpa over the eastern north pacific ocean easily exceeding the thresholds that define rapid intensification ri the noaa wp 3ds observed a portion of this ri with similar two aircraft missions on consecutive days the aircraft jettisoned 70 successful global positioning system gps dropwindsondes or gps sondes which reveal how conditions in the lower troposphere on the octant to quadrant scale evolved within 250 km of the eye reflectivity fields demonstrate that the deepening is correlated with a spiraling in of the northern eyewall that reduces the eye diameter by 10 km this behavior contrasts the more uniform contraction witnessed during eyewall replacement cycles mixing between the lower eye and eyewall as detailed by other investigators appears to have triggered the reduction in the eye diameter after ri the eyewall remains asymmetrical with the tallest echo tops and heaviest rain rates located o

lunar floor fractured craters classification distribution origin and implications for magmatism and shallow crustal structure 1 floor fractured craters ffcs are a class of lunar craters characterized by anomalously shallow floors cut by radial concentric and or polygonal fractures additional interior features are moats ridges and patches of mare material two formation mechanisms have been hypothesized floor uplift in response to shallow magmatic intrusion and sill formation and floor shallowing in response to thermally driven viscous relaxation this study combines new lunar orbiter laser altimeter lola and lunar reconnaissance orbiter camera lroc data to characterize and categorize the population of ffcs and map their distribution on the moon and uses variations in floor fractured crater morphology and regional distribution to investigate the proposed formation mechanisms the population of ffcs was categorized according to the classes outlined by schultz 1976 the distribution of these ffc categories shows an evolution of crater morphology from areas adjacent to lunar impact basins to areas in the lunar highlands we propose that this trend is supportive of formation by shallow magmatic intrusion and sill formation crustal thickness determines the magnitude of magmatic driving pressure and thus either piston like floor uplift for high magnitude or a convex floor profile for low magnitude predictions from previous studies modeling viscous relaxation are inconsistent with the observed altimetric profiles of ffcs hence our analysis favors ffc formation by shallow magmatic intrusion with the variety of ffc morphologies being intimately linked with location and crustal thickness and the driving pressure of the intrusion data from the grail gravity recovery and interior laboratory mission will help to test these conclusions

evidence of recent thrust faulting on the moon revealed by the lunar reconnaissance orbiter camera lunar reconnaissance orbiter camera images reveal previously undetected lobate thrust fault scarps and associated meter scale secondary tectonic landforms that include narrow extensional troughs or graben splay faults and multiple low relief terraces lobate scarps are among the youngest landforms on the moon based on their generally crisp appearance lack of superposed large diameter impact craters and the existence of crosscut small diameter impact craters identification of previously known scarps was limited to high resolution apollo panoramic camera images confined to the equatorial zone fourteen lobate scarps were identified seven of which are at latitudes greater than 60 indicating that the thrust faults are globally distributed this detection coupled with the very young apparent age of the faults suggests global late stage contraction of the moon

venus tectonics initial analysis from magellan radar imaging and altimetry data from the magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the venus surface the plains record a superposition of different episodes of deformation and volcanism strain is both areally distributed and concentrated into zones of extension and shortening the common coherence of strain patterns over hundreds of kilometers implies that many features in the plains reflect a crustal response to mantle dynamic processes ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening the mountain belts also show widespread evidence for extension and collapse both during and following crustal compression venus displays two geometrical patterns of concentrated lithospheric extension quasi circular coronae and broad rises with linear rift zones both are sites of significant volcanism no long large offset strike slip faults have been observed although limited local horizontal shear is accommodated across many zones of crustal shortening in general tectonic features on venus are unlike those in earth s oceanic regions in that strain typically is distributed across broad zones that are one to a few hundred kilometers wide and separated by stronger and less deformed blocks hundreds of kilometers in width as in actively deforming continental regions on earth

crater centered laccoliths on the moon modeling intrusion depth and magmatic pressure at the crater taruntius abstract many floor fractured craters on the moon show surface deformation like that seen over terrestrial laccoliths consequently terrestrial laccoliths provide one model for such crater modification this model directly relates surface deformation to the growth of a shallow crater centered intrusion and it estimates intrusion size and magma pressure it also yields a minimum estimate for intrusion depth maximum intrusion depths cannot be directly constrained but a range of likely intrusion depths can be derived with additional assumptions when the model is applied to the crater taruntius the surface record indicates an intrusion 30 km across and 1900 m thick the calculated excess magma pressure is 9 mpa 90 bar and the estimated intrusion depths range from 1 to 5 km if magma pressure reflects a hydrostatic magma column beneath taruntius these values suggest a total magma column length of 65 km during crater modification

multiscale analysis of tropical cyclone kinematic structure from airborne doppler radar composites abstractthe multiscale inner core structure of mature tropical cyclones is presented via the use of composites of airborne doppler radar analyses the structure of the axisymmetric vortex and the convective and turbulent scale properties within this axisymmetric framework are shown to be consistent with many previous studies focusing on individual cases or using different airborne data sources on the vortex scale these structures include the primary and secondary circulations eyewall slope decay of the tangential wind with height low level inflow layer and region of enhanced outflow radial variation of convective and stratiform reflectivity eyewall vorticity and divergence fields and rainband signatures in the radial wind vertical velocity vorticity and divergence composite mean and variance fields statistics of convective scale fields and how they vary as a function of proximity to the radius of maximum wind show that the inner eyewall edge is associated with stronger updrafts and higher refl