global survey of lunar regolith depths from lroc images abstract we performed the first global survey of lunar regolith depths using lunar reconnaissance orbiter camera lroc data and the crater morphology method for determining regolith depth we find that on both the lunar farside and in the nearside non mare regions the regolith depth is twice as deep as it is within the lunar maria our data compare favorably with previous studies where such data exist we also find that regolith depth correlates well with density of large craters 20 km diameter this result is consistent with the gradual formation of regolith by rock fracture during impact events

emplacement and inflation of the al halaq al kabir lava flow field central part of the al haruj volcanic province central libya abstract numerous of lava rise plateaus and tumuli developed in the medial and distal portions of the al halaq al kabir lava flow field during the last holocene eruption in the central part of the al haruj volcanic province ahvp these inflation structures provide important data on the lava emplacement mechanism in this part of the al haruj region where the widespread occurrence of tumuli and lava rise plateaus are good indicators of the mode of emplacement we report the results of detailed measurements of the maximum and minimum diameters in plan view of 551 lava rise plateaus and 289 tumuli from the distal part of the al halaq al kabir lava field using arcgis and field observations tumuli and lava rise plateaus may be divided into subpopulations according to abrupt changes in the scaling exponents on log log plots of their frequency versus diameter using the estimated stiffness young s modulus of the basaltic rocks in the study area of 10 34 gpa numerical and analytical results show that theoretical maximum tensile stresses in the inflated upper solidified crustal layers of the developing tumuli and lava rises at tens of mega pascals mpa this theoretical stress is orders of magnitude higher than typical in situ tensile strengths of rocks 0 5 9 mpa and thus high enough to rupture the crustal layers of the lava rises and tumuli the high tensile stresses are generated during crustal doming driven by a magmatic overpressure of only about 1 mpa our results partly explain the abundance of tension fractures at the surface of the al halaq al kabir lava flow field tumuli observed in the area are remarkably similar in morphology and aspect height width ratios to the flow lobe tumuli in holocene lava flow fields in iceland suggesting an analogous mechanics of formation there appears to be a coincidence between the age of an initial volcanism in the ahvp 7 9 5 3 ma and a local fauna and flora disappearance in the as sahabi area ne sirt basin during messinian zanclean time 7 5 to 5 ma we speculate that the volcanism may have had a local negative environmental impact and contributed to the reported decline in the fauna and flora in the area

geomorphology of lunar grabens requires igneous dikes at depth dense coverage of high resolution topographic measurements from the lunar orbiter laser altimeter lola now allows for a global survey of the long wavelength morphology of lunar grabens with important implications for the geologic processes that form them comparing model ground displacements for grabens that arise solely from faulting and from faulting involving a dike at depth with topographic measurements across some of the most prominent and best preserved grabens shows that many of them are underlain by a dike matching ground displacement models to topographic observations is the only way to detect and also provide specific geometric information about dikes too small to be resolved in available gravity and magnetic measurements and thus allows for quantitative assessments of magma source depths and required magma overpressures dike forming magmas are likely mantle derived originating from depths greater than 20 km with dike widths exceeding 100 500 m such dike geometric properties are only plausible if a mechanically weak lunar lithosphere was under extension at the time of dike emplacement

a new model for the emplacement of columbia river basalts as large inflated pahoehoe lava flow fields extensive flows of the columbia river basalt crb group in washington oregon and idaho are dominantly inflated compound pahoehoe sheet lavas early studies recognized that crb lavas are compound pahoehoe flows with textures suggesting low flow velocities but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks however small volume 1 km compound pahoehoe flows on kilauea hawai i demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger 10 20 km3 pahoehoe flows in iceland the vertical distribution of vesicles and other morphologic features within crb lava flows indicate that they grew similarly by inflation small pahoehoe lobes at the base and top of many crb pahoehoe lava flows indicate emplacement in a gradual piecemeal manner rather than as a single flood we propose that each thick crb sheet flow was active for months to years and that each group of flows produced by a single eruption a flow field was emplaced slowly over many years

the roza member columbia river basalt group a gigantic pahoehoe lava flow field formed by endogenous processes we present studies on the physical volcanology of the 15 ma roza member of the wanapum formation in the columbia river basalt group the roza member represents a compound pahoehoe flood basalt lava flow field with an area of 40 300 km 2 and a volume of 1300 km 3 it consists of 4 major lava flows each composed of numerous decimeter to kilometer long pahoehoe lobes roza lavas feature a wide range of pahoehoe surface structures such as lava rise plateaus tumuli and surface breakouts and we illustrate that the lava morphology is inconsistent with previous proposals of rapid emplacement for these lavas an integral component of the roza flow field is the sheet lobe with internal structures identical to those of inflated pahoehoe sheet lobes from hawaii and iceland both at the same scale and at much larger scales we identify a three part division of the sheet lobes into basal crust lava core and lava crust which are interpreted as the equivalent to the bottom crust the liquid lava core and the surface crust of an active inflating pahoehoe lobe the upper lava crust grows continuously during lava emplacement and its growth rate can be approximated by conductive cooling this relationship is used to calculate the emplacement time for individual roza sheet lobes and to derive a first order estimate on the duration of the roza eruption the results indicate that the emplacement of individual roza lobes lasted for months to years and that the lava flow field was constructed over a period of at least 14 years we propose that the roza flows achieved great areal dimensions and thicknesses by inflation and endogenous growth as the lava flowed from vent to flow front it traveled under an insulating crust which maintained cooling rates of 0 1 c km and allowed for efficient transport of lava over distances up to 300 km

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

tumulus development on lava flows insights from observations of active tumuli and analysis of formation models here we use observations of active flows along with detailed morphometric field measurements of more than 70 tumuli on flows at mount etna italy kilauea and hualalai us volcanoes to constrain a previously published model that estimates the pressure needed to form tumuli in an attempt to discover the nature and magnitude of pressure variations within active lava flow interiors we then consider how tumuli differ from idealized circular plates we incorporate observations of active tumuli and find that they may grow asymmetrically yet produce a symmetrical tumulus and can form where the flow path significantly changes direction bending models of clamped edges provide the most reasonable head estimates for the tumuli in our study tumulus formation requires the proper combination of cooling and effusion rate if cooling is too extensive and effusion rate too low the crust will provide too much resistance to bending if cooling is too limited and effusion rates too high crusts will not develop or have insufficient strength to resist fracture and subsequent breakouts we do not find it surprising that tumuli are rarely found over well established lava tubes that typically have rigid walls overlying crusts that exceed 2 m in thickness and provide too much resistance to bending silicic flows lack tumuli because the viscosity gradients within the flow are insufficient to concentrate stress in a localized area

simulated degradation of lunar impact craters and a new method for age dating farside mare deposits with the advent of clementine data it is now possible to determine the lithology and extent of geologic materials on the moon particularly the farside mare deposits however traditional crater counting techniques do not provide reliable age estimates of these materials owing to their small surface areas to support such studies we present a model for estimating their age by analyzing the morphometry of degraded craters 1 3 km in diameter a photoclinometric model was adapted for use with monoscopic 0 750 m ultraviolet visible and high resolution images where we extracted the topography of fresh craters a two dimensional computer model simulating linear diffusional creep was applied to fresh craters at a variety of diameters the resulting profiles were then compared to photoclinometric profiles of degraded craters of known ages for calibration application of the resulting model to degraded craters in the mare deposit of the central apollo basin 36 5 latitude 208 0 longitude indicates that this material was emplaced during the early imbrian period 3 85 ga by calculating the amount of material eroded from each of the degraded craters observed in this unit the average erosion rate is estimated to be 2 0 0 1 10 7 mm yr on the moon since the imbrian the estimated amount of material eroded during any given period suggests that the erosion rate has decreased with time implying that the flux of larger impactors has as well

lunar topographic roughness maps from lunar orbiter laser altimeter lola data scale dependence and correlation with geologic features and units we present maps of the topographic roughness of the moon at hectometer and kilometer scales the maps are derived from range profiles obtained by the lunar orbiter laser altimeter lola instrument onboard the lunar reconnaissance orbiter lro spacecraft as roughness measures we used the interquartile range of profile curvature at several baselines from 115 m to 1 8 km and plotted these in a global map format the maps provide a synoptic overview of variations of typical topographic textures and utilize the exceptional ranging precision of the lola instrument we found that hectometer scale roughness poorly correlates with kilometer scale roughness because they reflect different sets of processes and time scales hectometer scale roughness is controlled by regolith accumulation and modification processes and affected by the most recent events primarily geologically recent 1 2 ga meteoritic impacts kilometer scale roughness reflects major geological impact volcanic and tectonic events in earlier geological history young large impact craters are rough and their roughness decreases with age the global roughness maps revealed a few unusually dense clusters of hectometer and decameter size impact craters that differ in their morphology and settings from typical secondary crater clusters and chains the origin of these features is enigmatic the maps can assist in the geological mapping of the lunar maria by revealing contacts between volcanic plain units the global roughness maps also clearly reveal cryptomaria old volcanic plains superposed by younger materials primarily crater and basin ejecta

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

lunar and martian meteorite delivery services launch mechanisms for lunar and martian meteorites have been investigated by integrating physical modeling constraints geochemical cosmic ray exposure cre constraints and petrologic constraints the potential source region for lunar meteorites is remarkably small compared to the final crater volume cre constraints indicate that most launches start at depths of 3 2 m and cratering theory implies derivation of suitably accelerated objects from a subvolume with diameter only about 0 3 the final crater diameter the shallow depth provenance is probably related to shock wave interference enhanced by the lunar regolith s extremely low compressional wave velocity cre constraints alone imply that four to five separate launch events are represented among the eight well studied lunar meteorites most of the lunar meteorites are regolith breccias which tend to show only limited compositional diversity within any kilometer scale region of the moon several others are polymict breccias which also show relatively subdued compositional diversity compared to igneous rocks the observed diversity among these samples in terms of abundances of mare basalt and kreep and in mg mg fe ratio implies that among eight well studied lunar meteorites only two potential source crater pairings are plausible between asuka 881757 y 793169 most probable and between y 793274 eet875721 altogether these eight lunar meteorites apparently represent at least six separate source craters including three in the past 105 years and five in the past 106 years cre constraints imply that snc meteorites are launched from systematically greater depths than lunar meteorites sncs are also systematically bigger and all nine well studied sncs are uncommonly young by martian standards mafic igneous rocks comparison between viking and apollo results reveals that rocks the size of common meteorites are remarkably scarce in the martian regolith probably due to pervasive weathering a plausible explanation for these trends is that most old small and shallow rocks on mars have been weakened by a two stage process of brecciation followed by pervasive weathering to the point where they seldom survive the stresses of spallation off the planet the scarcity of source crater pairing among the lunar meteorites implies that these objects can be launched from craters much smaller than previously estimated and tends to support the suggestion of rabinowitz 1993 astrophys j 407 412 427 that present day cratering rates for the earth moon region may be higher than previously estimated

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

formation of lunar mare domes along crustal fractures rheologic conditions dimensions of feeder dikes and the role of magma evolution abstract in this study we examine a set of lunar mare domes located in the hortensius milichius t mayer region and in northern mare tranquillitatis with respect to their formation along crustal fractures their rheologic properties the dimensions of their feeder dikes and the importance of magma evolution processes during dome formation many of these domes display elongated summit vents oriented radially with respect to major impact basins and several dome locations are also aligned in these preferential directions analysis of clementine uv vis and lunar prospector gamma ray spectrometer data reveals that the examined mare domes formed from low si basaltic lavas of high feo and low to moderate tio2 content based on their morphometric properties diameter height volume obtained by photoclinometric and shape from shading analysis of telescopic ccd images we derive rheologic quantities lava viscosity during eruption effusion rate duration of the effusion process magma rise speed and the dimensions of the feeder dikes we establish three rheologic groups characterised by specific combinations of rheologic properties and dike dimensions where the most relevant discriminative parameter is the lava viscosity the first group is characterised by 10 4 pa s 10 6 pa s and contains the domes with elongated vents in the milichius t mayer region and two similar domes in northern mare tranquillitatis the second group with 10 2 pa s 10 4 pa s comprises the very low aligned domes in northern mare tranquillitatis and the third group with 10 6 pa s 10 8 pa s the relatively steep domes near hortensius and in the t mayer region the inferred dike dimensions in comparison to lunar crustal thickness data indicate that the source regions of the feeder dikes are situated within the upper crust for six of the domes in northern mare tranquillitatis while they are likely to be located in the lower crust and in the upper mantle for the other examined domes by comparing the time scale of magma ascent with the time scale on which heat is conducted from the magma into the host rock we find evidence that the importance of magma evolution processes during ascent such as cooling and crystallisation increases with lava viscosity we conclude that different degrees of evolution of initially fluid basaltic magma are able to explain the broad range of lava viscosities inferred for the examined mare domes the spectral data reveal that differences in tio2 content may additionally account for the systematic difference in lava viscosity between the two examined lunar regions we show that the described mechanisms are likely to be valid also for other lunar mare domes situated near cauchy and arago regarded for comparison on the other hand we find for the gruithuisen and mairan highland domes that despite their inferred high lava viscosities of 10 8 10 9 pa s no significant magma cooling in the dike occurred during ascent supporting previous findings that the highland domes were formed during a specific phase of non mare volcanism by highly silicic viscous lavas

the role of unsteady effusion rates on inflation in long lived lava flow fields abstract the emission of volcanic gases and particles can have global and lasting environmental effects but their timing tempo and duration can be problematic to quantify for ancient eruptions where real time measurements are absent lava flows for example may be long lasting and their impact is controlled by the rate tempo and vigor of effusion these factors are currently difficult to derive from the geologic record but can have large implications for the atmospheric impact of an eruption we conducted a set of analogue experiments on lava flow inflation aiming at connecting lava morphologies preserved in the rock record to eruption tempo and dynamics through pulsating effusion rates inflation a process where molten material is injected beneath the crust of an active lava flow and lifts it upwards is a common phenomenon in basaltic volcanic systems this mechanism requires three components a a coherent insulating crust b a wide spread molten core and c pressure built up beneath the crust from a sustained supply of molten material inflation can result in a lava flow growing tens of meters thick even in flow fields that expand hundreds of square kilometers it has been documented that rapid effusion rates tend to create channels and tubes isolating the active part of the flow from the stagnant part while slow effusion rates may cause crust to form quickly and seize up forcing lava to overtop the crust however the conditions that allow for inflation of large flow fields have not previously been evaluated in terms of effusion rate by using peg 600 wax and a programmable pump we observe how by pulsating effusion rate inflation occurs even in very low viscosity basaltic eruptions we show that observations from inflating hawaiian lava flows correlate well with experimental data and indicate that instantaneous effusion rates may have been 3 times higher than average effusion rates during the emplacement of the 23 january 1988 flow at k lauea hawai i the identification of a causal relationship between pulsating effusion rates and inflation may have implications for eruption tempo in the largest inflated flows flood basalts

properties of the hermean regolith iv photometric parameters of mercury and the moon contrasted with hapke modelling a comparison of the photometric properties of mercury and the moon is performed based on their integral phase curves and disk resolved image data of mercury obtained with the swedish vacuum solar telescope proper absolute calibration of integral v band

eruption of magmatic foams on the moon formation in the waning stages of dike emplacement events as an explanation of irregular mare patches abstract volcanic eruptions on the moon take place in conditions of low gravity and negligible atmospheric pressure very different from those on earth these differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity and to the production of unusual eruption products neither predicted nor observed on earth in the terminal stages of eruptions these include the unusual mounds and rough hummocky blocky floors of some small shield summit pit crater floors elongate depressions and mare flows similar to those named irregular mare patches imps by braden et al 2014 we examine the ascent and eruption of magma in the waning stages of the eruptive process in small shield summit pit crater floors and show that many imp characteristics can be plausibly explained by basaltic magma behavior as the rise rate of the ascending magma slows to zero volatiles exsolve in the dike and lava lake to form a very vesicular foam and the dike begins to close stresses in the very vesicular and porous lava lake crust produce fractures through which the foam extrudes at a rate determined by its non newtonian rheology waning stage extrusion of viscous magmatic foams to the surface produces convex mounds whose physical properties inhibit typical impact crater formation and regolith development creating an artificially young crater retention age this mechanism for the production and extrusion of very vesicular magmatic foams is also applicable to waning stage dike closure associated with pit craters atop dikes and fissure eruptions in the lunar maria providing an explanation for many irregular mare patches this mechanism implies that imps and associated mare structures small shields pit craters and fissure flows formed synchronously billions of years ago in contrast to very young ages less than 100 million years proposed for imps by some workers

geological characterization of the ina shield volcano summit pit crater on the moon evidence for extrusion of waning stage lava lake magmatic foams and anomalously young crater retention ages ina a distinctive 2 3 km d shaped depression is composed of unusual bulbous shaped mounds surrounded by optically immature hummocky blocky floor units the crisp appearance optical immaturity and low number of superposed impact craters combine to strongly suggest a geologically recent formation for ina but the specific formation mechanism remains controversial we reconfirm that ina is a summit pit crater vent on a small shield volcano 3 5 billion years old following detailed characterization we interpret the range of ina characteristics to be consistent with a two component model of origin during the waning stages of summit pit eruption activities the ina pit crater floor is interpreted to be dominated by the products of late stage low rise rate magmatic dike emplacement magma in the dike underwent significant shallow degassing and vesicle formation followed by continued degassing below the solidified and highly microvesicular and macrovesicular lava lake crust resulting in cracking of the crust and extrusion of gas rich magmatic foams onto the lava lake crust to form the mounds these unique substrate characteristics highly porous aerogel like foam mounds and floor terrains with large vesicles and void space exert important effects on subsequent impact crater characteristics and populations influencing 1 optical maturation processes 2 regolith development and 3 landscape evolution by modifying the nature and evolution of superposed impact craters and thus producing anomalously young crater retention ages accounting for these effects results in a shift of crater size frequency distribution model ages from

migration of parabolic dunes at aberffraw anglesey north wales abstract aberffraw is a 1 km wide and 3 km long transgressive dunefield that extends inland along a northeast southwest trending valley from a southwest facing beach traeth mawr the prevailing wind is from the southwest and both the parabolic dunes and the valley within which they lie are sub parallel to the prevailing wind the dunefield at aberffraw includes two foredune ridges and three rows of active compound parabolic dunes at the landward end is a lake llyn coron which has been formed by dunes migrating up the valley and damming the river afon ffraw between the parabolic dunes are gently sloping interdune areas with a close cropped vegetation the parabolic dunes at aberffraw have been migrating inland across the interdune areas rates of parabolic dune migration are derived from three sets of aerial photographs taken in 1940 1982 and 1993 the aerial photographs have been scanned and manipulated in arcview gis software registration of the aerial photograph to an ordnance survey os map was performed using ground control points gcps common fixed features that are identifiable on both the aerial photographs and the baseline map attempts to correct for the inherent distortions of aerial photography were made during registration standardising the projection of the photographs to a common baseline allows meaningful spatial analysis and the dune ridges trailing edges and areas of bare sand were mapped from each photograph as a series of overlays rates of dune migration are calculated from the spatial distance between linear trend lines parallel to the dune crests and perpendicular to the dune migration orientation applied to sections of dune ridges for 1940 and 1993 trend lines were only fitted to sections where continuity of dune form was maintained over the given period the method provides an improved representation of the actual migration rate as it incorporates the whole of the parabolic dune form and the whole of the compound dune ridge form into the calculation it effectively measures the centre point or line of a dune or dune ridge as opposed to the variable positions and orientations of the dune crest noses which represent maximum migration rather than the mean rates of parabolic dune migration range from a minimum of 0 m year 1 to a maximum of 3 6 m year 1 with an average migration rate of 1 m year 1

crater degradation on the lunar maria topographic diffusion and the rate of erosion on the moon landscape evolution on the moon is dominated by impact cratering in the post maria period in this study we mapped 800 m to 5 km diameter craters on 30 of the lunar maria and extracted their topographic profiles from digital terrain models created using the kaguya terrain camera we then characterized the degradation of these craters using a topographic diffusion model because craters have a well understood initial morphometry these data provide insight into erosion on the moon and the topographic diffusivity of the lunar surface as a function of time the average diffusivity we calculate over the past 3 ga is 5 5 m2 myr with this diffusivity after 3 ga a 1 km diameter crater is reduced to approximately 52 of its initial depth and a 300 m diameter crater is reduced to only 7 of its initial depth and craters smaller than 200 300 m are degraded beyond recognition our results also allow estimation of the age of individual craters on the basis of their degradation state provide a constraint on the age of mare units and enable modeling of how lunar terrain evolves as a function of its topography

late stage imbrium volcanism on the moon evidence for two source regions and implications for the thermal history of mare imbrium abstract large open fissures or volcanic rifts can form in volcanic terrain and they are also conduits for magma ascending through the lunar crust on the moon we investigated two volcanic source regions within mare imbrium by tracking surface morphologic features and compositional information the euler source region is situated at the southwest edge of the basin while the lambert source region lies off the south margin of the imbrium mascon survey of dike surface manifestations in euler source site suggest that dikes are the possible source of the local upper basaltic flows and the last lava phases with well developed scarps near the euler crater which extend northeast to the basin center the euler dike swarm are radial to the basin and reveal possible dike to conduit transition mechanism they reveal radial subsurface fractures which may be tensional cracks preceding to the emplacement of the last stage of the mare fill of these the largest dike has a more than 100 km length the spatial arrangement of tectonic and volcanic features in lambert source site is directly or indirectly controlled by the regional compression and extension stresses associated with flexure in response to mascon and basalt loading in addition compositional variation trends show a general southwest to northeast flooding direction of the exposed high ti basalts this will have important implications for both the imbrium basin s mare volcanism and for the thermal evolution of mare imbrium and the moon

the structure of basaltic scoria and reticulite and inferences for vesiculation foam formation and fragmentation in lava fountains in this investigation pyroclast structures are used to constrain degassing in basaltic lava fountains vesicle size shape number density interconnectedness and packing character are quantified and related to 1 the kinetics of bubble nucleation and growth 2 the structural evolution of magmatic foams and 3 the influence of vesiculation rate on magma fragmentation measurements made on a diverse suite of pyroclasts from kilauea volcano indicate that basaltic foams evolve through an initially disordered closed celled spherical state to a well ordered open celled polyhedral state as the vesicularity rises from 75 to 98 the structural changes occur rapidly 10 s in the conduit and fountain in response to an intense vesiculation burst vesicle size distribution systematics indicate bubble nucleation rates 2 104 events cm 3s 1 that are approximately three orders of magnitude greater than those found for effusive eruptive activity bubble growth rates 9 10 4 cm s exceed effusive estimates by a factor of 3 the observed runaway rate of bubble production indicates strong supersaturations at the onset of nucleation we speculate that the rise speed of the magma as it reaches the level where significant volatile exsolution begins determines the intensity of the vesiculation burst and hence the vigor of the eruption rapid expansion and acceleration of the magma under these conditions may provide the impetus for fragmentation

spectral properties of the marius hills volcanic complex and implications for the formation of lunar domes and cones we have used multispectral data from the clementine uv visible camera to study the volcanic features of the marius hills complex and their comparison to other lunar domes and cones there are several mare units identified in the complex each with a unique ti content as indicated by their 415 750 nm value the domes in marius hills are spectrally identical to the mare plains of the complex supporting similar compositions in contrast most of the volcanic cones of the complex are lower in reflectance bluer in color and have weaker mafic absorptions than the mare and domes the spectral characteristics of the cones can best be explained by fine grained crystallization in the spatter that compose the cones other lunar cones such as mons esam in northern tranquillitatis have spectral properties similar to those at marius hills the rima parry cones and their associated dark mantle deposit appear redder with a stronger mafic absorption than the marius hills cones the cones isis and osiris in southern mare serenitatis the domes of rumker hills and several domes in northern mare tranquillitatis are spectrally similar to adjacent mare units the mairan and gruithuisen domes in northern oceanus procellarum have a feldspathic signature characteristic of highland material although they are redder and brighter than adjacent highland soils they appear to represent highland material that resembles domes rather than actual mare domes like those at marius and rumker hills the diversity of lunar volcanic features can best be explained by differences in accumulation rates and cooling of ejected clasts from various eruption styles mare domes may have formed at lower effusion rates thereby allowing lava to construct small shields with slopes 3 the steeper domes at marius hills require higher viscosities resulting from even lower effusion rates and enhanced crystallization in the magmas during the terminal stages of earlier eruptions that emplaced the mare cones like mons esam rima parry isis and osiris are aligned along linear rilles and are interpreted to result from degassing of near surface dikes in contrast the cones of marius hills show no linear alignment and may result from strombolian eruptions at the terminal stages of earlier effusive eruptions that emplaced the domes and mare in the complex

using satellite imagery to identify and analyze tumuli on earth and mars abstract tumuli are small dome like features that form when magmatic pressures build within a subsurface lava pathway causing the overlying crust to bulge upwards as the appearance of these features has been linked to lava flow structure e g underlying lava flow tubes and conditions there is interest in identifying such features in satellite images so they can be used to expand our understanding of lava flows within regions difficult to access such as on other planets here we define a methodology for identifying and measuring tumuli within satellite imagery and validate it by comparing our results with fieldwork results of terrestrial tumuli reported in the literature and with independent measurements we made within amboy field ca in addition we present aggregated results from the application of our methodology to satellite images of six terrestrial fields and seven martian fields with 2100 tumuli identified per planet comparisons of tumuli morphometrics on earth and mars yield similarities in size and overall shape which were surprising given the many differences in the environmental and planetary conditions within which these features have formed given our measurements we identify constraints for tumulus formation models and drivers that would yield similar shapes and sizes on two different planets furthermore we test a published hypothesis regarding the number of tumuli that form per a square kilometer and find it unlikely that a diagnostic tumuli density value exists

controls on lunar basaltic volcanic eruption structure and morphology gas release patterns in sequential eruption phases assessment of mare basalt gas release patterns during individual eruptions provides the basis for predicting the effect of vesiculation processes on the structure and morphology of associated features we subdivide typical lunar eruptions into four phases phase 1 dike penetrates to the surface transient gas release phase phase 2 dike base still rising high flux hawaiian eruptive phase phase 3 dike equilibration lower flux hawaiian to strombolian transition phase phase 4 dike closing strombolian vesicular flow phase we show how these four phases of mare basalt volatile release together with total dike volumes initial magma volatile content vent configuration and magma discharge rate can help relate the wide range of apparently disparate lunar volcanic features pyroclastic mantles small shield volcanoes compound flow fields sinuous rilles long lava flows pyroclastic cones summit pit craters irregular mare patches imps and ring moat dome structures rmdss to a common set of eruption processes

ina pit crater on the moon extrusion of waning stage lava lake magmatic foam results in extremely young crater retention ages the enigmatic ina feature on the moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m y of lunar history an extremely young age for volcanism on the moon ina is a 2 3 km d shaped depression that consists of a host of unusual bleb like mounds surrounded by a relatively optically fresh hummocky and blocky floor documentation of magmatic volcanic processes from shield volcano summit pit craters in hawai i and new insights into shield building and dike evolution processes on the moon provide important perspectives on the origin of ina we show that the size location morphology topography and optical maturity of ina are consistent with an origin as a subsided summit pit crater lava lake on top of a broad 22 km diameter 3 5 b y old shield volcano new theoretical treatments of lunar shield building magmatic dike events predict that waning stage summit activity was characterized by the production of magmatic foam in the dike and lake the final stages of dike stress relaxation and closure cause the magmatic foam to extrude to the surface through cracks in the lava lake crust to produce the mounds the high porosity of the extruded foams 75 altered the nature of subsequent impact craters the aerogel effect causing them to be significantly smaller in diameter which could bias the crater derived model ages accounting for this effect allows for significantly older model ages to 3 5 b y contemporaneous with the underlying shield volcano thus extremely young volcanic eruptions are not required to explain the unusual nature of ina

correlation of deep moonquakes and mare basalts implications for lunar mantle structure and evolution abstract the genesis of mare basalts and deep moonquakes are important events that have major implications for understanding the thermal evolution and interior dynamics of the moon the eruption of mare basalts predominantly from 3 9 ga to 3 ga ago represents one of the most important events in lunar geological history deep moonquakes recorded by the apollo seismic network show the dynamic nature of the present day lunar mantle in this study we have correlated the presence of the mare basalts using feo concentration as a proxy with the epicenters of 52 well located deep moonquake dmq clusters we determine feo concentrations of 13 wt or higher to be representative of the mare basalt deposits our analysis shows that over 63 of the dmqs occur within 1 from the mare basalt deposits while over 80 of the dmqs are within 5 from the mare basalt deposits our analysis also shows that for the same amount of randomly distributed dmqs within a spherical cap on the nearside that encompasses all the nearside dmqs the probability of over 80 of the dmqs occurring within 5 from the mare basalt deposits is about 0 01 thus rejecting a random distribution of the dmqs with respect to the mare basalts the correlation between mare basalts and the dmqs from our analysis suggests that the mare basalts may be derived from melting processes at relatively large depths consistent with previous petrology and geodynamic studies we propose that the water and volatiles in the mare basalt source material i e a mixture of ilmenite cumulates and olivine orthopyroxene together called mic play an important role in causing the dmqs and that the dmqs delineate the present day locations of mic in the deep mantle since the mare basalts are predominately distributed on the nearside our results further suggest that the dmqs may indeed be largely nearside features which is a prediction that can be tested in future lunar seismic exploration

a new lunar digital elevation model from the lunar orbiter laser altimeter and selene terrain camera abstract we present an improved lunar digital elevation model dem covering latitudes within 60 at a horizontal resolution of 512 pixels per degree 60 m at the equator and a typical vertical accuracy 3 to 4 m this dem is constructed from 4 5 10 9 geodetically accurate topographic heights from the lunar orbiter laser altimeter lola onboard the lunar reconnaissance orbiter to which we co registered 43 200 stereo derived dems each 1 1 from the selene terrain camera tc 1010 pixels total after co registration approximately 90 of the tc dems show root mean square vertical residuals with the lola data of

high resolution imaging science experiment hirise images of volcanic terrains from the first 6 months of the mars reconnaissance orbiter primary science phase 1 in the first 6 months of the mars reconnaissance orbiter s primary science phase the high resolution imaging science experiment hirise camera has returned images sampling the diversity of volcanic terrains on mars while many of these features were noted in earlier imaging they are now seen with unprecedented clarity we find that some volcanic vents produced predominantly effusive products while others generated mostly pyroclastics flood lavas were emplaced in both turbulent and gentle eruptions producing roofed channels and inflation features however many areas on mars are too heavily mantled to allow meter scale volcanic features to be discerned in particular the major volcanic edifices are extensively mantled though it is possible that some of the mantle is pyroclastic material rather than atmospheric dust support imaging by the context imager ctx and topographic information derived from stereo imaging are both invaluable in interpreting the hirise data

lava tubes terraces and megatumuli on the 1614 24 pahoehoe lava flow field mount etna sicily the 1614 1624 lava flow of mt etna was formed during a long duration flank eruption involving predominantly pahoehoe flows which produced unusual surface features including mega tumuli here defined and terraces detailed mapping of the flow units surface features and associated tubes reveals a complex sequence of emplacement for the field the stair stepped terraces appear to have been formed as a consequence of self damming of tube fed flows which developed perched ponds of lava surges of lava through tubes elevated sections of crusted lava at the distal ends of the flow to generate tumuli some as high as 130 m as a consequence of pressure via hydrostatic head conditions within the tube although pahoehoe lavas and the related features described here are atypical of mt etna they may reflect styles of eruption and lava emplacement found on volcanoes elsewhere

structural fabric of the paleozoic golconda allochthon antler peak quadrangle nevada progressive deformation of an oceanic sedimentary assemblage the golconda allochthon in nevada consists of structurally complex mid to late paleozoic basinal sedimentary and volcanic rocks deformed under low temperature and pressure conditions and emplaced onto the north american shelf in the permo triassic above the basal thrust in the antler peak area the allochthon consists in ascending structural order of late early to early late permian thick bedded chert pumpernickel subunit 1 pennsylvanian and early permian thin bedded chert argillite and siltstone pumpernickel subunit 2 mississippian siliciclastic turbidites jory unit and undated chert and argillite of the trenton unit open to tight folds in subunit 1 trend north south and are east vergent folds in thinner bedded subunit 2 vary considerably in style fold axes in this unit are distributed within the mean axial plane oriented n s 60 w but exhibit a west northwest trending data gap boudin axes measured in zones of highly disrupted layering interpreted as zones of movement or shear exhibit similar patterns without data gaps these girdled distributions in part reflect rotation of these elements upon greater strain towards the east west trending direction of tectonic transport or towards parallelism with the x axis of the strain ellipsoid asymmetry of folds indicate movement was west to east locally developed late stage folds in subunit 2 are subhorizontal trend north south and are compatible with fold fault solutions that indicate east directed thrusting striations measured within fault zones yield bidirectional east west slip lines our fold and fault data indicate that east west shortening of these basinal sediments was accomplished by folding and east directed thrust faulting during a single progressive deformational event this conclusion is supported by the presence of a major west dipping thrust fault in the map area that places mississippian over permian rocks the allochthon formed as an east vergent submarine fold and thrust belt that was subsequently thrust on the continental shelf autochthonous rocks beneath the golconda thrust are virtually undeformed suggesting that most of the structure in the allochthon formed prior to its ultimate emplacement

the origin of ina evidence for inflated lava flows on the moon 1 ina is an enigmatic volcanic feature on the moon known for its irregularly shaped mounds the origin of which has been debated since the apollo missions three main units are observed on the floor of the depression 2 9 km across 64 m deep located at the summit of a low shield volcano irregularly shaped mounds up to 20 m tall a lower unit 1 to 5 m in relief that surrounds the mounds and blocky material analyses of lunar reconnaissance orbiter camera images and topography show that features in ina are morphologically similar to terrestrial inflated lava flows comparison of these unusual lunar mounds and possible terrestrial analogs leads us to hypothesize that features in ina were formed through lava flow inflation processes while the source of the lava remains unclear this new model suggests that as the mounds inflated breakouts along their margins served as sources for surface flows that created the lower morphologic unit over time mass wasting of both morphologic units has exposed fresh surfaces observed in the blocky unit ina is different than the terrestrial analogs presented in this study in that the lunar features formed within a depression no vent sources are observed and no cracks are observed on the mounds however lava flow inflation processes explain many of the morphologic relationships observed in ina and are proposed to be analogous with inflated lava flows on earth

diversity of basaltic lunar volcanism associated with buried impact structures implications for intrusive and extrusive events abstract relatively denser basalt infilling and the upward displacement of the crust mantle interface are thought to be contributing factors for the quasi circular mass anomalies for buried impact craters in the lunar maria imagery and gravity observations from the lunar reconnaissance orbiter lro and dual gravity recovery and interior laboratory grail missions have identified 10 partially or fully buried impact structures where diversity of observable basaltic mare volcanism exists with a detailed investigation of the characteristics of associated volcanic landforms we describe their spatial distribution relationship with respect to the subsurface tectonic structure of complex impact craters and propose possible models for the igneous processes which may take advantage of crater related zones of weakness and enable magmas to reach the surface we conclude that the lunar crust having been fractured and reworked extensively by cratering facilitates substance and energy exchange between different lunar systems an effect modulated by tectonic activities both at global and regional scales in addition we propose that the intrusion caused contribution to gravity anomalies should be considered in future studies although this is commonly obscured by other physical factors such as mantle uplift and basalt load

newly discovered ring moat dome structures in the lunar maria possible origins and implications we report on a newly discovered morphological feature on the lunar surface here named ring moat dome structure rmds these low domes a few meters to 20 m height with slopes 5 are typically surrounded by narrow annular depressions or moats we mapped about 2 600 rmdss in the lunar maria with diameters ranging from tens to hundreds of meters four candidate hypotheses for their origin involving volcanism are considered we currently favor a mechanism for the formation of the rmds related to modification of the initial lava flows through inflated flow squeeze ups and or extrusion of magmatic foams below a cooling lava flow surface these newly discovered features provide new insights into the nature of emplacement of lunar lava flows suggesting that in the waning stages of a dike emplacement event magmatic foams can be produced extrude to the surface as the dike closes and break through the upper lava flow thermal boundary layer crust to form foam mounds and surrounding moats

ring moat dome structures rmdss in the lunar maria statistical compositional and morphological characterization and assessment of theories of origin ring moat dome structures rmdss are positive morphologic features found clustered across many mare regions on the moon of which only a few isolated examples have been previously reported our continuing survey has expanded the known locations of the rmdss from 2 600 to over 8 000 indicating that rmdss are more common geological features than previously thought this work presents a detailed geomorphological analysis of 532 rmdss identified in several mare basins the combination of detailed elemental mapping morphological and morphometric analyses spatial distribution relationships with other geologic structures and comparison with terrestrial analogs lead us to conclude that 1 rmdss represent low circular mounds with diameters of a few hundred meters average about 200 m and a mean height of 3 5 m the mounds are surrounded by moats ranging from tens to over 100 m in width and up to several meters in depth 2 there is a wide variation of titanium abundances although rmdss are more commonly found in mare regions of moderate to high titanium content 3 wt tio2 3 rmdss are found to occur on or around fractures graben and volcanic edifices small shields and cones 4 a spatial association between rmdss and irregular mare patches see braden et al 2014 https doi org 10 1038 ngeo2252 is observed suggesting that both may form from related lava flows 5 comparisons between rmdss and lava inflationary structures on earth support an inflation related extrusive nature and a genetic relationship with host lava flow processes and 6 rmds embayment relationships with craters of different degradation ages superposed on the host mare and regolith development models produces conflicting age relationships and divide theories of rmds origin into two categories 1 synchronous with the emplacement and cooling of the host lava flows 3 4 ga and 2 emplaced substantially after the host mare lava unit in the period 0 3 ga we outline the evidence supporting this age conundrum and implications for the different theories of origin and describe future research avenues to help resolve these outstanding questions 2020 american geophysical union all rights reserved

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

statistical distribution of tumuli on pahoehoe flow surfaces analysis of examples in hawaii and iceland and potential applications to lava flows on mars 1 spatial distributions of tumuli on lava flow surfaces can be quantitatively linked to subsurface inflation processes three distinct styles of flow emplacement are studied 1 lava flows undergo inflation that changes as a function of space and time resulting in random spatial distributions of tumuli 2 lava flows with preferred pathways result in systematic clustering of inflation features and 3 established tubes or narrow pahoehoe flows produce chains of tumuli statistical analyses are required to distinguish between styles one and two comparison of the spatial distribution of tumuli on a portion of a lava flow at mauna ulu with the poisson distribution indicates that tumuli are randomly distributed on the flow surface typical of style one emplacement where small scale topographic variability and low slope influence development of preferred pathways that evolve over time at thrainsskjoldur direct statistical comparisons to the poisson spatial distribution are inconclusive but nearest neighbor analysis indicates significant clustering an initially random spatial distribution is inferred that developed preferred pathways and systematic clustering of inflation features as with style two at elysium planitia on mars the flow margin is significantly deficient in inflation features while away from the margin the flow exhibits a random spatial distribution of tumuli typical of style one emplacement the flow is interpreted as multiple units or a single flow that migrated in space during emplacement at the 1843 flow on mauna loa tumuli occur on a linear trend consistent with style three emplacement

the physical mechanisms of deep moonquakes and intermediate depth earthquakes how similar and how different abstract we here review the characteristics of deep moonquakes dmq and conclude that they share many common features with certain categories of intermediate depth earthquakes namely the pressure temperature conditions where they occur their occurrence in highly localized nests their tendency to occur repeatedly at the same or nearly the same location and their distribution of sizes b values we thus explore various physical mechanisms proposed for earthquakes that might also explain deep moonquakes these include the possibility that there are partial melts or fluid phases in the lunar mantle that permit dmq to occur at pressures where ordinary brittle fracture is not possible the possibility that stress concentration increases tidal stresses at certain locations where moonquakes occur repeatedly and the possibility that dmq occur at relatively low stresses because rock strength is lowered by a fatigue process induced by the repetitive application of tidal stresses the similarities between dmq and terrestrial earthquakes imply that research focusing on the properties of both phenomena may help us understand the physical origins of both

lunar cryptomaria physical characteristics distribution and implications for ancient volcanism cryptomaria lunar volcanic deposits obscured by crater and basin impact ejecta can provide important information about the thermal and volcanic history of the moon the timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism in addition knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean solidification here we use multiple datasets e g m3 lola lroc diviner to undertake a global analysis to identify the general characteristics e g topography surface roughness rock abundance albedo etc of lunar light plains in order to better distinguish between ancient volcanic deposits cryptomaria and impact basin and crater ejecta deposits we find 20 discrete regions of cryptomaria covering approximately 2 of the moon which increase the total area covered by mare volcanism to 18 of the lunar surface comparisons of light plains deposits indicate that the two deposit types volcanic and impact produced are best distinguished by mineralogic data on the basis of cryptomaria locations the distribution of mare volcanism does not appear to have changed in the time prior to its exposed mare basalt distribution there are several hypotheses explaining the distribution of mare basalts which include the influence of crustal thickness mantle convection patterns asymmetric distribution of source regions kreep distribution and the influence of a proposed procellarum impact basin the paucity of farside mare basalts means that multiple factors such as crustal thickness variations and mantle convection are likely to play a role in mare basalt emplacement

the importance of pahoehoe abstract pahoehoe lava flows are common in every basaltic province and their submarine variants pillow lavas and sheet flows cover the bulk of the earth pahoehoe flows are emplaced by inflation the injection of molten lava underneath a solidified crust only in the past few years has an understanding of the inflation process and the ability to recognize ancient inflated lava flows been achieved all large terrestrial basaltic flow fields studied to date including flood basalts were emplaced as thermally efficient inflated compound pahoehoe sheet flows this leads us to propose that this is the standard way of emplacing large lavas the swell hypothesis the atmospheric impact of such flood basalt eruptions could have been protracted and severe providing a plausible link between flood basalt eruptions and mass extinctions

a theoretical model for the formation of ring moat dome structures products of second boiling in lunar basaltic lava flows abstract newly documented ring moat dome structures rmdss low mounds typically several hundred meters across with a median height of 3 5 m and surrounded by moats occur in the lunar maria they appear to have formed synchronously with the surrounding mare basalt deposits it has been hypothesized that they formed on the surfaces of lava flows by the extrusion of magmatic foams generated in the flow interiors as the last stage of the eruption and flow emplacement process we develop a theoretical model for the emplacement and cooling of mare basalts in which the molten cores of cooling flows are inflated during the late stages of eruptions by injection of additional hot lava containing dissolved volatiles crystallization of this lava causes second boiling an increase in vapor pressure to the point of supersaturation due to crystallization of the melt generating copious quantities of vesicles magmatic foam layers at the top and bottom of the central core of the flow flow inflation of many meters is predicted to accompany the formation of the foam layers flexing the cooled upper crustal layer and forming fractures that permit extrusions of the magmatic foams onto the surface to form domes with subsidence of the subjacent and surrounding surface forming the moats by modeling the evolution of the internal flow structure we predict the properties of rmdss and the conditions in which they are most likely to form we outline several tests of this hypothesis

reevaluation of vesicle distributions in basaltic lava flows a fundamental dichotomy in the study of basaltic lava flows is that observations of active flows are restricted to flow surfaces yet older flows are often exposed only in vertical cross section cross sectional exposures of an inflated basaltic sheet flow emplaced in kalapana hawaii from 1990 to 1991 provide an unusual opportunity to merge these two viewpoints permitting the development of the internal structure of the flow to be viewed in the context of its known emplacement history we demonstrate that fundamental features of the flow structure a thick upper vesicular crust that diminishes downward in overall vesicularity a dense flow interior and a thin lower vesicular zone are generated through syn emplacement cooling of upper and lower flow crusts both the inverse correlation of overall vesicularity and vesicle size and the constant relative thickness of the upper vesicular zone are unique to inflated flows and permit a reinterpretation of flows previously interpreted to be ponded rapidly emplaced identification of inflation in turn implies near horizontal paleoslopes and permits estimates of flow duration based on upper flow crust thickness

three long lava flows in north queensland the kinrara toomba and undara basaltic lava flows are from 55 to 160 km long and range in age from 13 to 190 ka the lavas were emplaced down low gradients 0 2 to 0 4 with volumes ranging up to 30 km3 they were not unusually hot at eruption 1130 1160 nor unusually fluid gentle topography controlled the flows and shallow drainage lines captured them lava tubes operated in places and some drained to form caves injection under surface crust was widespread producing inflation features ranging from tumuli and low plateaus to extensive ridges sustained eruption was essential for the development of the long flows but each is composite with pauses between successive pulses that partially covered the earlier longer flows the lava structures are mainly pahoehoe but some a a lavas are present of the three volcanoes involved undara is a simple low angle lava cone with a 200 m wide crater toomba is a low angled cone with several eruption centers and kinrara has a deep crater with evidence of strong fountaining effusion rates are not known but may have been relatively low similar to those observed in hawaiian volcanoes lava tubes most of which remained undrained are believed to have been of major importance in flow emplacement given the evidence of successive flows and the time needed to develop widespread inflation it is suggested that the two long flows over 100 km involved many decades of eruption

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

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

structure and origin by injection of lava under surface crust of tumuli lava rises lava rise pits and lava inflation clefts in hawaii tumuli are positive topographic features that are common on hawaiian pahoehoe lava flow fields particularly on shallow slopes and 75 measured examples are presented here to document the size range tumuli form by up tilting of crustal plates without any crustal shortening and are thus distinguished from pressure ridges which are up buckled by laterally directed pressure the axial or star like systems of deep clefts that characterize tumuli are defined here as lava inflation clefts their tips advanced into red hot lava and they widened as uplift proceeded and while the lava crust was thickening flat surfaced uplifts formed like tumuli by injection of lava under a surface crust were previously called pressure plateaus but lava rise is proposed instead the pits that abound among lava rises previously attributed to collapse or subsidence are generally formed because the lava around them rose and the name lava rise pit is proposed unique examples of tumuli and lava rises from which lava drained out under a surface crust 1 5 to 2 5 m thick are described from kilauea caldera these examples show that in tumuli and lava rises the crust floats on considerable bodies of fluid lava and is able to do so because of its higher vesicle content the fluid lava loses many of its gas bubbles during residence beneath the crust the bulk densities of samples from tumuli show a general downward increase the form of the density profile is consistent with the relationship that for any given crustal thickness the density of fluid lava closely matched the average density of that crust suggesting that the lava was stably density stratified it is inferred that stable stratification was regulated by out flows of the more vesicular lava fractions loss of bubbles through the lava inflation clefts and entry of injected lava at its level of neutral buoyancy below the uppermost meter the downward decrease in vesicularity closely conforms with that expected by compression of a uniform mass of gas per unit mass of lava

eruption reconstruction formation of flow lobe tumuli and eruption duration in the 5900 bp helgafell lava field heimaey south iceland abstract the 5900 bp helgafell eruption started with an intense fire fountaining phase that deposited scoria and spatter near the vent spatter accumulated agglutinated and was subsequently emplaced as clastogenic flows the intense initial phase was followed by effusive emplacement of tube fed pahoehoe this type of lava emplacement makes up the bulk of the lava field and contains abundant inflation features such as tumuli and pressure ridges we measured the depths of 358 inflation clefts in tumuli and the thicknesses of the upper vesicular crust in flow lobes from the helgafell lava field measurements of altitude between a point source of lava tubes and the depth of inflation clefts in tumuli suggest that the magmastatic pressure affects initial tumuli formation the overall growth of tumuli is however more dependent on effusion rate and collapse clogging of individual tubes than on the magmastatic head within tubes three areas with abundant tumuli are recognized in the helgafell lava field each of which was active for at least 47 days the average time for tumuli formation is 32 days using the crustal measurements of inflation features we test the hypothesis that the total eruption duration can be estimated for a pre historic volcanic eruption we chose the helgafell lava field to test this hypothesis because it has 1 abundant inflation features that are easily measured and 2 the majority of lava flows emplaced during the eruption are well exposed our result shows that the duration of the helgafell eruption can be estimated to 11 12 months yielding an average volumetric effusion rate for the helgafell eruption of 0 05 0 06 km3 month this result is very similar to the effusion rates for two known eruptions in the same volcanic system i e the 1963 1967 surtsey and the 1973 eldfell eruptions with effusion rates of 0 02 and 0 04 km3 month respectively given that all three eruptions occurred within the same volcanic system and that they have similar volumetric effusion rates we suggest that our estimated eruption duration for helgafell is reasonable our results building on the suggestion by hon et al 1994 hon k kauhikaua j denlinger r mackay k 1994 emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii geol soc amer bull 106 351 370 that the duration of inflation can be estimated for individual flows by measuring inflation features show that by combining abundant and measureable inflation features with a well established stratigraphy the duration of an entire pre historic eruption can be estimated

development of tumuli in the medial portion of the 1983 aa flow field mount etna sicily a number of tumuli formed on the aa dominated lava fan complex which developed in the medial zone of the 1983 flow field of mount etna during the later stages of the eruption this complex flow field formed on shallow sloping ground below a scarp between 1900 and 1700 m asl a major tube system fed a branching tube network in the fan complex numerous tumuli and break outs of lava formed in the fan three main types of tumulus are identified 1 focal tumuli which are formed from the break up and uplift of old thick lava crust and themselves become sustained sites for the distribution of lava both as flows and within distributary tubes these focal tumuli are significant centres associated with major tubes 2 satellite tumuli which are typically elongate whale back shaped features that branch out from focal tumuli these satellite tumuli were initially lava flows erupted from a focal tumulus the crust of the flow slowed or came to a halt and the rigid crust became uplifted and fractured forming a dome shaped ridge feature these satellite tumuli continued to be fed from the focal tumulus and became sites of lava emission with numerous break outs 3 distributary tumuli formed on the fan associated with short lived break outs from tubes and are relatively simple structures formed from limited effusion of toey lobes and pahoehoe lava the major tumuli on the fan complex show distinct dilation fractures the fracture surfaces provide good exposure of the crust and three distinct zones are recognised an upper zone showing columnar jointing a middle zone consisting of planar fracture surfaces and a basal zone with distinctive banded planar fracture surfaces showing evidence of both brittle and ductile formation using these data a model is proposed for tumulus growth field analysis of the fan complex shows how it was fed by a branching tube system leading to flow thickening formation of tumuli and numerous ephemeral boccas

lunar meteorite regolith breccias an in situ study of impact melt composition using la icp ms with implications for the composition of the lunar crust dar al gani dag 400 meteorite hills met 01210 pecora escarpment pca 02007 and macalpine hills mac 88104 88105 are lunar regolith breccia meteorites that provide sampling of the lunar surface from regions of the moon that were not visited by the us apollo or soviet luna sample return missions they contain a heterogeneous clast population from a range of typical lunar lithologies dag 400 pca 02007 and mac 88104 88105 are primarily feldspathic in nature and met 01210 is composed of mare basalt material mixed with a lesser amount of feldspathic material here we present a compositional study of the impact melt and impact melt breccia clast population i e clasts that were generated in impact cratering melting processes within these meteorites using in situ electron microprobe and la icp ms techniques results show that all of the meteorites are dominated by impact lithologies that are relatively ferroan mg 10 and have low incompatible trace element ite concentrations i e typically 10 ppm sm high magnesium suite typically 70 mg or high alkali suite high ites sc sm ratios 2 target rocks instead the meteorite mafic melts are more ferroan kreep poor and sc rich and represent mixing between feldspathic lithologies and low ti or very low ti vlt basalts as pca 02007 and mac 88104 05 were likely sourced from the outer feldspathic highlands terrane our findings suggest that these predominantly feldspathic regions commonly contain a vlt to low ti basalt contribution

observations on basaltic lava streams in tubes from kilauea volcano island of hawai i from 1986 to 1997 the pu u o o kupaianaha eruption of kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10 12 km from vents on the volcano s east rift zone to the ocean within a kilometer of the vent tubes were as much as 20 m high and 10 25 m wide on steep slopes 4 10 a little farther away from the vent some tubes formed by roofing over of lava channels lava streams were typically 1 2 m deep flowing within a tube that here was typically 5 m high and 3 m wide on the coastal plain 1 tubes within inflated sheet flows were completely filled typically 1 2 m high and several tens of meters wide tubes develop as a flow s crust grows on the top bottom and sides of the tubes restricting the size of the fluid core the tubes start out with nearly elliptical cross sectional shapes many times wider than high broad flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting sometimes the tubes began downcutting progressive downcutting was frequently observed through skylights a rate of 10 cm d was measured at one skylight for nearly 2 months

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

a sinuous tumulus over an active lava tube at klauea volcano evolution analogs and hazard forecasts abstract inflation of narrow tube fed basaltic lava flows tens of meters across such as those confined by topography can be focused predominantly along the roof of a lava tube this can lead to the development of an unusually long tumulus its shape matching the sinuosity of the underlying lava tube such a situation occurred during k lauea volcano s hawai i usa ongoing east rift zone eruption on a lava tube active from july through november 2010 short lived breakouts from the tube buried the flanks of the sinuous ridge like tumulus while the tumulus crest its surface composed of lava formed very early in the flow s emplacement history remained poised above the surrounding younger flows at least several of these breakouts resulted in irrecoverable uplift of the tube roof confined sections of the prehistoric carrizozo and mccartys flows new mexico usa display similar sinuous ridge like features with comparable surface age relationships we contend that these distinct features formed in a fashion equivalent to that of the sinuous tumulus that formed at k lauea in 2010 moreover these sinuous tumuli may be analogs for some sinuous ridges evident in orbital images of the tharsis volcanic province on mars the short lived breakouts from the sinuous tumulus at k lauea were caused by surges in discharge through the lava tube in response to cycles of deflation and inflation di events at k lauea s summit the correlation between di events and subsequent breakouts aided in lava flow forecasting breakouts from the sinuous tumulus advanced repeatedly toward the sparsely populated kalapana gardens subdivision destroying two homes and threatening others hazard assessments including flow occurrence and advance forecasts were relayed regularly to the hawai i county civil defense to aid their lava flow hazard mitigation efforts while this lava tube was active

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

large shield volcanoes on the moon 1 the volcanic style of the moon has long been understood to consist almost exclusively of flood basalts erupted from fissures along with minor pyroclastic activity large central vent shield volcanoes that characterize basaltic volcanism on the other terrestrial planets appeared to be absent small few kilometers diameter central vent constructs have long been recognized in the lunar maria and often are found clustered in fields throughout the lunar maria new global topographic data from the lola and lroc instruments on lro reveal that almost all of these volcanic complexes on the moon occur on large regional topographic rises in the lunar maria tens to hundreds of kilometers in extent and between several hundred to several thousand meters high we propose that these topographic swells are shield volcanoes and are the lunar equivalents of the large basaltic shields found on the earth venus and mars the newly recognized lunar shields are found peripheral to the large deeply flooded impact basins imbrium and serenitatis suggesting a genetic relation to those features loading of the lithosphere by these basalt filled basins may be responsible for inducing a combination of flexural and membrane stress inducing a pressure distribution on vertically oriented dikes favorable to magma ascent this condition would occur in a zone annular to the large circular loads produced by the basins where the shield volcanoes occur

integrated topographic photometric and spectral analysis of the lunar surface application to impact melt flows and ponds abstract this study provides an analysis of the impact melt deposits melt flows and ponds associated with eight lunar craters with diameters between 9 and 96 km in terms of their topographic photometric and spectral properties our analysis is based on an integrated method for construction of digital elevation models dem of high lateral resolution pixel wise photometric modelling construction of topographically corrected normalised reflectance maps extraction of spectral parameters and estimation of elemental abundances based on moon mineralogy mapper m 3 hyperspectral data and data of the lunar prospector gamma ray spectrometer instrument most of the examined geologically fresh impact melt flows are characterised by lower albedos than the surrounding surface and tend to originate from topographically low parts of the source crater rim as an exception we find that the impact melt deposits northeast of crater aristillus lack any optical signature and are not visible in monochrome images but can only be observed by their anomalously smooth surface inferred from the dem some impact melt flows and ponds exhibit photometric anomalies in terms of the asymmetries in the single particle scattering function and the slope of that parameter with respect to wavelength these photometric anomalies may be due to impact melt specific anomalies of the surface structure e g consolidated rock rather than regolith or anomalies in size or shape of the geometric surface elements e g individual grains or their aggregates on submillimetre spatial scales the strength of the hydroxyl absorption displays a negative anomaly with respect to the surrounding surface for the majority of the examined impact melt flows as an impact melt specific spectral behaviour we find a decrease in the absorption band depth around 2000 nm and in several cases a simultaneous increase of the absorption band depth near 1000 nm these observations are consistent with the laboratory analyses by tompkins et al tompkins s pieters c m 2010 meteorit planet sci 45 7 1152 1169 of chemically uniformly composed mixtures between crystalline and glass material for several impact melt flows their data allow to roughly estimate the fraction of glass material based on our spectral analysis

a comparative study of iron abundance estimation methods application to the western nearside of the moon abstract the feo weight percentage wt abundance of the moon s western nearside 55 s 55 n and 5 e 40 w is estimated using data from the infrared spectrometer 2 sir 2 and the moon mineralogy mapper m3 in this study we modified an feo abundance estimation algorithm bhatt m mall u bugiolacchi r mckenna lawlor s banaszkiewicz m nathues a ullaland k 2012 icarus 220 51 64 which relies exclusively on the 2 m absorption band parameters the modified feo abundance estimation algorithm and the regression based elemental abundance estimation algorithm wohler c grumpe a berezhnoy a bhatt m u mall u 2014 icarus 235 86 122 which is based on the 1 m and 2 m absorption band parameters is applied to the m3 data we have compared results obtained from these two modified algorithms with a previously published clementine s feo wt map lucey p g blewett d t jolliff b l 2000 j geophys res 105 20297 20306 the effects of topography and space weathering on feo wt estimates have been successfully minimized using the modified algorithm based on the 2 m absorption band parameters thus this algorithm can be successfully applied at middle to high latitudes furthermore a correction for tio2 is applied to the feo abundance estimation algorithm based on the 2 m absorption band parameters using the m3 data our comparative study shows a good correspondence between the three algorithms discussed there are two locations the crater tycho and the region around rima bode which show major discrepancies our modified algorithm based on the 2 m absorption parameters predicts 3 4 wt less feo for the ray system of tycho than for the surrounding region the average iron abundance for the lunar highlands is about 6 wt and for the mare regions is about 16 wt using the regression based elemental abundance estimation algorithm and the algorithm based on the 2 m absorption parameters this result is consistent with the previous analysis using lunar prospector gamma ray spectrometer data sets the feo wt is in the range 20 24 wt for the high ti basalts using both the modified iron abundance estimation and the regression based elemental abundance estimation algorithms

tumuli and associated features from the western deccan volcanic province india whale back shaped uplifts called tumuli are common in the pahoehoe flows of the western deccan volcanic province dvp although they usually occur in hummocky flows they are also associated with thicker sheet lobes they have been subjected to a detailed morphometric and petrographic study for the first time the tumuli are characterised by positive relief and lava inflation clefts occupied by squeeze ups they display elongate as well as equant forms some are constituted of a single flow lobe whereas others display multiple flow lobes some tumuli appear to have developed along anastomosing tube systems the detailed study of one of the tumuli reveals considerable petrographic and textural variations among the constituent flow units some of these such as the enrichment of phenocrysts in squeeze ups and breakouts could be related to the emplacement dynamics of the tumulus all the observed tumuli display much evidence of inflation or endogenous growth field observations and measurements reveal that the tumuli and associated pahoehoe features display a close similarity with their hawaiian counterparts this is a very significant observation since it points out to a similarity in nature and style of eruptions in hawaii and at least in the western part of the dvp this has an important bearing on determining the short medium and long term effusion rates in the deccan however any concrete inference will have to await systematic volcanological studies of the lava features in the dvp

the morphology and formation of flow lobe tumuli on icelandic shield volcanoes three types of tumuli are recognized on monogenetic shield volcanoes in iceland namely 1 lava coated tumuli 2 upper slope tumuli and 3 flow lobe tumuli flow lobe tumuli grade into lava rises which are larger inflation structures but both structures have a similar mode of emplacement the areal distribution of flow lobe tumuli in the flow field differs from that of lava coated tumuli and upper slope tumuli flow lobe tumuli are frequent in the medial and distal parts of pahoehoe flow fields whereas the other two tumulus types are more frequent in the proximal parts of the flow fields the flow lobe tumuli also differ from the two other tumulus types as regards their morphology they are significantly larger have shallower flanks and do not have extensive outflows from the cracks the vesicle distribution within the flow lobe tumuli is similar to that of p type flow lobes a fairly dense zone is situated between the upper and lower vesicular zones each flow lobe tumulus is an individual lobe that inflates and forms tension cracks in the lava crust major lava tubes are mostly absent from the areas where flow lobe tumuli form and therefore the emplacement of flow lobe tumuli must be related to secondary short lived pathways of lava the flow lobe tumuli inside the flow fields of icelandic shield volcanoes are morphologically identical to those flow lobe tumuli that are found in the margins of flow fields of other icelandic volcanoes these observations allow us to model the flow lobe tumuli as morphological variants of p type flow lobes forming along terminating secondary lava paths flow lobe tumuli form at low lava supply rates of the order of 10 2 10 5 m3 s and are generated by inflation of the lava crust as a result of magmatic overpressure in the associated lava core we model the tumulus as a circular elastic plate that becomes uplifted inflated and fractured by a uniform magmatic overpressure at its bottom we conclude that 1 the effective thickness of the lava crust that is subject to bending is 0 2 0 4 m and remains essentially constant during the formation of the tumulus and 2 for flow lobe tumuli that are supplied with magma from tubes that originate in overflow from the lava lake of a shield volcano the elevation difference between the tumuli and the surface of the source lava lake is commonly around 100 m this elevation difference can give rise to a static magmatic overpressure of 2 5 mpa in the tumulus whereas the overpressure needed to form a typical flow lobe tumulus is only 0 2 1 mpa

emplacement history and inflation evidence of a long basaltic lava flow located in southern payenia volcanic province argentina abstract the el corcovo lava flow from the huanul shield volcano in the southern mendoza province central western argentina traveled a distance of 70 km and covered a minimum area of 415 km 2 the flow emplacement was controlled both by extrinsic e g topography and intrinsic e g lava supply rate lava physicochemical characteristics factors the distal portion of the lava flow reached the colorado river valley in la pampa province where it spread and then was confined by earlier river channels cross sections through the flow surveyed at several localities show two vesicular layers surrounding a dense central section where vesicles are absent or clustered in sheet shaped and cylindrical shaped structures lavas of the el corcovo flow are alkaline basalts with low values of viscosity the morphological and structural characteristics of the flow and the presence of landforms associated with lava accumulation are the evidence of inflation this process involved the formation of a tabular sheet flow up to 4 m of thick with a large areal extent in the proximal sectors while at terminal sectors frontal lobes reached inflation values up to 10 m the numerous swelling structures present at these portions of the flow suggest the movement of lava in lava tubes we propose that this aspect and the low viscosity of the lava allowed the flow travel to a great distance on a gentle slope relief

global surface slopes and roughness of the moon from the lunar orbiter laser altimeter 1 the acquisition of new global elevation data from the lunar orbiter laser altimeter carried on the lunar reconnaissance orbiter permits quantification of the surface roughness properties of the moon at unprecedented scales and resolution we map lunar surface roughness using a range of parameters median absolute slope both directional along track and bidirectional in two dimensions median differential slope and hurst exponent over baselines ranging from 17 m to 2 7 km we find that the lunar highlands and the mare plains show vastly different roughness properties with subtler variations within mare and highlands most of the surface exhibits fractal like behavior with a single or two different hurst exponents over the given baseline range when a transition exists it typically occurs near the 1 km baseline indicating a significant characteristic spatial scale for competing surface processes the hurst exponent is high within the lunar highlands with a median value of 0 95 and lower in the maria with a median value of 0 76 the median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing among other things the ejecta surrounding large basins particularly orientale as well as the ray systems surrounding young copernican age craters in addition it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age

the effect of inflation on the morphology derived rheological parameters of lava flows and its implications for interpreting remote sensing data a case study on the 2014 2015 eruption at holuhraun iceland abstract morphology derived lava flow rheology is a frequently used tool in volcanology and planetary science to determine rheological parameters and deduce the composition of lavas on terrestrial planets and their moons these calculations are usually based on physical equations incorporating 1 lava flow driving forces gravity slope and flow rate and 2 morphological data such as lava flow geometry flow width height or shape of the flow outline all available methods assume that no geometrical changes occur after emplacement and that the measured flow geometry reflects the lava s apparent viscosity and or yield strength during emplacement it is however well established from terrestrial examples that lava flows may inflate significantly after the cessation of flow advance this inflation affects in turn the width to height ratio upon which the rheological estimates are based and thus must result in uncertainties in the determination of flow rheology as the flow height is one of the key parameters in the morphology based deduction of flow properties previous studies have recognized this issue but to date no assessment of the magnitude of this error has been presented this is likely due to a lack of digital elevation models dems at sufficiently high spatial and temporal resolution the 2014 15 holuhraun eruption in central iceland represents one of the best monitored large volume 1 5 km3 lava flow fields 85 km2 to date an abundance of scientific field and remote sensing data were collected during its emplacement moreover inflation plays a key role in the emplacement dynamics of the late stage of the lava field here we use a time series of high resolution dems acquired by the tandem x satellite mission prior during and after the eruption to evaluate the error associated with the most common methods of deriving lava flow rheology from morphological parameters used in planetary science we can distinguish two dominant processes as sources of error in the determination of lava flow rheology from morphology 1 wholesale inflation of lava channels and 2 post halting inflation of individual lava toes these result in a 2 4 to 17 fold overestimation of apparent viscosity and a 0 7 to 2 4 fold overestimation of yield strength when applied in planetary sciences this overestimation in rheological parameters translates directly to an overestimation of the respective lavas silica content we conclude that although qualitatively informative morphological analysis is insufficient to discern lava rheology and composition instead in situ analysis together with high resolution remote sensing data is needed to properly constrain the compositions involved in planetary volcanism

a reassessment of the emplacement and erosional potential of turbulent low viscosity lavas on the moon we have reevaluated the role of thermal erosion by low viscosity lunar lavas as a mechanism for the formation of the lunar sinuous rules we have adapted the model of williams et al 1998 and used the compositions of an apollo 12 basalt and a terrestrial komatiitic basalt to investigate the compositional and environmental effects on the flow behavior of low viscosity lavas on the moon and the earth our model predicts that lunar lavas could have erupted as turbulent flows that were capable of flowing hundreds of kilometers on a sufficiently flat unobstructed substrate these results are consistent with previous studies modeling of lavas over a substrate of the same composition shows that thermal erosion rates would have been low 10 cm d 1 as a result long duration eruptions approximately months to years would have been required to incise deep tens to hundreds of meters channels partial melting and mechanical removal of the substrate a mechanism suggested by hulme 1973 to enhance erosion only slightly increases thermal erosion rates other factors such as higher flow rates or lava superheating could have produced deep rules by thermal erosion during shorter duration eruptions a superheated lunar lava not only would have had a higher erosion rate 40 cm d 1 but also would have remained uncrusted for tens of kilometers which is consistent with the open channel morphology of most sinuous rules for lunar lavas with large volatile i e vesicle contents the presence of vesicles would have tended to increase viscosity at low strain rates resulting in shorter turbulent flow distances lower thermal erosion rates and thus shallower erosion channel depths for given eruption durations