precise analysis of icesat altimetry data and assessment of the hydrostatic equilibrium for subglacial lake vostok east antarctica summary based on the ice cloud and land elevation satellite icesat laser altimetry data the hydrostatic equilibrium he condition for the subglacial lake vostok east antarctica is evaluated a digital elevation model dem of the ice surface is derived by a regional crossover adjustment the analysis of the dem and its comparison with gps derived ice surface elevations and an ice surface dem based on radar altimetry data reveal an overall accuracy of better than 0 7 m for the lake area the dem is combined with an ice thickness model and a regional geoid model to determine the deviation of the local ice surface height from he for large parts of the lake the ice sheet fulfils the he our results reveal a strong positive deviation of about 10 m along the lake shoreline in addition positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio echo sounding in the southern part of the lake we find a linear negative deviation 4 0 m which coincides with the convoy route from vostok station to mirny base in addition to the dem relative biases for the icesat laser operational periods are determined in the regional crossover adjustment

distribution of rocks on the gusev plains and on husband hill mars 1 the population of rocks larger than 15 cm in diameter was measured at 36 locations imaged by the spirit rover over 4 km of the traverse across the gusev plains and husband hill in gusev crater on mars the rock population observed on plains surfaces is consistent with impact fragmentation of rubbly fractured volcanics and reveals little evidence for modification by secondary processes or weathering interpretation of counts from husband hill suggest an influence by bedrock for rocks larger than 0 5 m across but the distribution of smaller rocks is consistent with ejecta possessing contributions from pre plains impact events results indicate plains surfaces experienced only tens of centimeters of eolian erosion deposition since the hesperian whereas meters rather than tens of meters of erosion modified husband hill since the early hesperian

spaceborne observations of the 2000 bezymianny kamchatka eruption the integration of high resolution aster data into near real time monitoring using avhrr abstract since its launch in december 1999 the advanced spaceborne thermal emission and reflection radiometer aster instrument has been observing over 1300 of the world s volcanoes during the day and night and at different times of the year at the onset of an eruption the temporal frequency of these regularly scheduled observations can be increased to as little as 1 3 days at higher latitudes however even this repeat time is not sufficient for near real time monitoring which is on the order of minutes to hours using poorer spatial resolution 1 km pixel instruments the eruption of bezymianny volcano kamchatkan peninsula russia in march 2000 was detected by the alaska volcano observatory avo and also initiated an increased observation frequency for aster a complete framework of the eruptive cycle from april 2000 to january 2001 was established with the advanced very high resolution radiometer avhrr data used to monitor the large eruptions and produce the average yearly background state for the volcano twenty nearly cloud free aster scenes 2 days and 18 nights show large thermal anomalies covering tens to hundreds of pixels and reveal both the actively erupting and restive background state of the volcano aster short wave infrared swir and thermal infrared tir data were also used to validate the recovered kinetic temperatures from the larger avhrr pixels as well as map the volcanic products and monitor the thermal features on the summit dome and surrounding small pyroclastic flows these anomalies increase to greater than 90 c prior to a larger eruption sequence in october 2000 in addition aster has the first multispectral spaceborne tir capability which allowed for the modeling of micrometer scale surface roughness vesicularity on the active lava dome where coupled with ongoing operational monitoring programs like those at avo aster data become extremely useful in discrimination of small surface targets in addition to providing enhanced volcanic mapping capabilities

an analysis of the ice sheet surface and subsurface topography above the vostok station subglacial lake central east antarctica radio echo sounding res and satellite radar altimeter data were analyzed in order to identify the surface and subsurface topography around the largest known subglacial lake at vostok station east antarctica named here as lake vostok in doing so a data set was established from which a qualitative description of the flow of ice across the lake was developed patterns of ice flow were constructed through consideration of 1 the ice sheet surface from the satellite altimeter and 2 internal layering from res it is concluded that lake vostok influences the dynamics of the overriding ice specifically although the flow of ice across the lake is dominated by the general eastward flow of the grounded ice sheet a southward velocity component caused by an ice shelf type ice flow mechanism is also present over the subglacial lake a further 67 smaller subglacial lakes exist within central regions of the antarctic ice sheet occupying 5 10 of the ice sheet base subglacial lakes may therefore exert a significant control on ice dynamics within central antarctica

the fold illusion the origins and implications of ogives on silicic lavas abstract folds on the surfaces of mafic lavas are among the most readily recognized geological structures and are used as first order criteria for identifying ancient lavas on earth and other planetary bodies however the presence of surface folds on the surface of silicic lavas is contested in this study and we challenge the widely accepted interpretation that silicic lava surfaces contain folds using examples from the western united states and sardinia italy we interpret the ridges and troughs on their upper surfaces typically referred to as ogives or pressure ridges as fracture bound structures rather than folds we report on the absence of large scale buckle style folds and note instead the ubiquitous presence of multiple generations and scales of tensile fractures comparable to crevasses in glaciers and formed in ways similar to already recognized crease structures we report viscosity data and results of stress analyses that preclude folding ductile deformation in compression of the upper surface of silicic lavas at timescales of emplacement weeks to months therefore analysis of fold geometry wavelength amplitude etc is erroneous and instead the signal produced reflects the strength and thickness of the brittle upper surface stretching over a ductile interior the presence of ogives on the surfaces of lavas on other planetary bodies may help to elucidate their rheological properties and crustal thicknesses but relating to their tensile strength not viscosity

impact of earthquake induced liquefaction and related ground failure on a mississippian archeological site in the new madrid seismic zone central usa an investigation of earthquake induced liquefaction features and related ground failure at the east archeological site 3po610 located near the southern end of the new madrid seismic zone was crucial to the identification of cultural features and horizons and interpretation of archeological data through the examination of stratigraphic and structural relations in the archeological excavation as well as in three nearby trenches it was determined that cultural horizons and features including the floor of a sweat lodge are tilted displaced downward and buried by a vented sand deposit known as a sand blow this sand blow is up to 1 m thick and is composed of four major depositional units suggesting that it formed during a sequence of large earthquakes the compound sand blow directly overlies cultural horizons and features indicating that the earthquakes occurred near the end of or soon after occupation on the basis of radiocarbon dating of samples collected above and below the sand blow the earthquakes are estimated to have occurred between a d 1300 and 1670 a new madrid earthquake sequence ca a d 1450 150 was the probable cause of liquefaction and ground failure at the site and may have led to cultural abandonment of the site ironically the earthquakes that may have led to abandonment of the site also helped to preserve it for posterity

identity and emplacement of domical structures in the western arcadia planitia mars 1 morphologic morphometric and thermophysical aspects of domical structures in a restricted part of the mars northern plains were characterized using mars odyssey and mars global surveyor data the majority of domical structures consist of relatively high thermal inertia subcircular to irregularly shaped core bodies surrounded by adjacent relatively low albedo low thermal inertia annuli and dispersed aureoles of apparently disaggregated material core profiles vary considerably from low to high aspect ratios elongate arms of material extend from the central summit regions in some of the structures core features include apparent blocky surface texture summit fissures and pits apparent summit and flank ruptures suggestive of eruption of material and concentric and straight summit ridges core heights range from 30 to 400 m mean 160 m diameters range from 620 to 3090 m mean 1550 m aspect ratios range from 0 02 to 0 36 mean 0 11 and volumes range from 0 1 to 1 8 km3 an additional morphologic type consists of subcircular domical mounds that are apparently covered by plains materials we propose that the majority of the structures are partially extrusive cryptodomes and lava domes whereas the mounds are entirely intrusive cryptodomes

structural variation and the development of thick rhyolite lava a case study of the sanukayama rhyolite lava on kozushima island japan abstract geological studies of ancient rhyolite lavas are required for understanding flow dynamics because rhyolite lava eruption is an infrequent event the pleistocene sanukayama rhyolite lava is about 130 m thick and located on kozushima island japan vertical sections of the lava are well exposed in the sea cliff and in a dissected valley providing a good opportunity for the elucidation of the internal structural variations the vertical lithofacies variations are classified into three zones of pumiceous obsidian and crystalline from the top to the base respectively the exposed area is considered to correspond to the upper half of the lava in the boundaries between each zone the lithofacies are mingled rather than exhibiting gradual change this indicates that rheological contrasts are arisen within the lava due to differences of vesicularity and or crystallinity various heterogeneous structures are recognized throughout the lava such as obsidian and reddish layers in the pumiceous zone strongly deformed white colored bands and a clastic layer in the obsidian zone and dark colored bands in the crystalline zone we demonstrate on the basis of geological evidences and magnetic studies that these heterogeneous structures originated mostly from shear induced fracturing within the advancing lava this study indicates that brittle lava fracturing during ductile brittle transition likely governs the acceleration of rhyolite lava heterogeneity

the roughness of natural terrain a planetary and remote sensing perspective we examine the various methods and parameters in common use for quantifying and reporting surface topographic roughness it is shown that scale dependent roughness parameters are almost always required though not widely used we suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered by different workers using different field techniques can be directly and easily intercompared we illustrate the proposed method by analyzing topographic data from 60 different surfaces gathered by five different groups and examine the information for common features we briefly discuss the implications of our analysis for studies of planetary surface roughness lander safety and radar remote sensing modeling and analysis

eruption of crystal mush and the formation of steep sided volcanic domes on venus insight from picritic bodies near marki cyprus abstract steep sided domes are one of the most striking volcanic landforms on venus they may also be key to determining the range of magmatic processes operating on venus as in contrast to all other volcanic landforms they likely represent eruption of viscous lava although there have been various explanations for the presence of high viscosity lavas on a planet dominated by effusive basaltic volcanism it is often assumed that they are silica rich this would necessitate either periodic large scale extensive fractionation of basaltic magma in the venusian crust or a mechanism for re melting an already silica enriched lower crust as such determining the origin of steep sided domes is important in constraining magmatic processes on venus and for understanding geological evolution of stagnant lid regime planets generally here we use observations from the marki region of the troodos ophiolite cyprus to propose an alternative model where steep sided domes form by eruption of crystal mush from the same magmatic systems which fed extensive basaltic terrains with which domes are associated steep sided volcanic landforms near marki represent extrusion of un eruptible extremely olivine rich mush onto the palaeo seafloor following cessation of widespread basaltic volcanism field relations suggest that these bodies formed by localised repeated extrusion of crystal mush fed by extensional faults tapping crustal magma chambers differential stress enabled eruption of viscous non newtonian magmas with crystal contents 50 vol which then built up volcanic edifices on the seafloor a similar much larger scale mechanism can explain many features of steep sided volcanic domes on venus including their intimate relationship with extensive basaltic terrains general morphology and dome spatial and temporal clustering this implies that domes share a common magmatic origin with the venusian basaltic crust rather than representing a discrete magmatic process and that they represent periods of magmatic quiescence it also implies that the contrasting morphology of these domes arises from a fundamental difference in eruptive style from widespread effusive basaltic magmatism to localised extensional fault controlled extrusion of crystal mush if correct this mechanism might also explain formation of steep sided volcanic edifices on other large stagnant lid regime planetary bodies

the mechanical properties of solidified polyethylene glycol 600 an analog for lava crust abstract the strength of lava crust and the role of that crust in determining lava flow dynamics and morphology are of fundamental importance in modeling lava flow behavior great improvements to flow models have been made by combining theoretical analysis with the results from analog experiments using polyethylene glycol peg 600 wax which solidifies just below room temperature and can be used to simulate solidifying flows however a paucity of experimental data on the mechanical properties of solid peg 600 has limited the quantitative interpretation of the role of crust in these experiments we have therefore conducted experiments to measure the mechanical properties tensile strength shear strength and young s modulus of solidified peg 600 at temperatures and strain rates similar to those employed in analog experiments the mechanical properties of peg 600 can be modeled by a power law function of temperature with the tensile strength exhibiting an additional dependence on strain rate at intermediate temperatures marked changes in the temperature dependence of the young s modulus and in the character of failure surfaces indicate a transition from brittle to ductile behavior we find that the strength of solid peg 600 at experimental temperatures and strain rates exceeds that inferred for the crust on active laboratory flows by four orders of magnitude this discrepancy is best explained by the presence of a thin visco elastic layer separating the solid surface from the fluid interior of peg 600 flows a model that has been suggested to explain the behavior of some basaltic lava flows

radar attenuation and temperature within the greenland ice sheet 2015 american geophysical union all rights reserved the flow of ice is temperature dependent but direct measurements of englacial temperature are sparse the dielectric attenuation of radio waves through ice is also temperature dependent and radar sounding of ice sheets is sensitive to this attenuation here we estimate depth averaged radar attenuation rates within the greenland ice sheet from airborne radar sounding data and its associated radiostratigraphy using existing empirical relationships between temperature chemistry and radar attenuation we then infer the depth averaged englacial temperature the dated radiostratigraphy permits a correction for the confounding effect of spatially varying ice chemistry where radar transects intersect boreholes radar inferred temperature is consistently higher than that measured directly we attribute this discrepancy to the poorly recognized frequency dependence of the radar attenuation rate and correct for this effect empirically resulting in a robust relationship between radar inferred and borehole measured depth averaged temperature radar inferred englacial temperature is often lower than modern surface temperature and that of a steady state ice sheet model particularly in southern greenland this pattern suggests that past changes in surface boundary conditions temperature and accumulation rate affect the ice sheet s present temperature structure over a much larger area than previously recognized this radar inferred temperature structure provides a new constraint for thermomechanical models of the greenland ice sheet

rhyolite lava emplacement dynamics inferred from surface morphology abstract the morphology of a silicic lava is created by the fluid dynamic conditions that operated during flow careful analysis of these features can thus be used to reconstruct emplacement processes we used unoccupied aerial system and structure from motion photogrammetry techniques to collect centimeter scale spatial resolution imagery of the surfaces of south coulee and obsidian dome rhyolite lavas mono inyo craters usa we supplement the newly acquired orthomosaics and digital elevation models with existing imagery of other holocene rhyolite lavas from across the western usa including rock mesa dome south sister or newberry flow south sister or obsidian flow newberry or interlake flow newberry or and banco bonito flow valles caldera nm although many morphologic features exist we restrict our quantitative analyses to the recurrent ridges and blocks of loose rubble that are common to the flows ridge spacing and ridge vergence indicate the ridges are likely folds produced by compression during emplacement pressure ridge spacings range from 27 to 45 m at south coulee and 18 to 34 m on obsidian dome spacing generally decreases with distance from the vent across both lavas ridge amplitudes range from 4 to 17 m at both lavas and show little correlation with distance from the vent the vergence of the crest of the ridges in the flow interiors points back to the source vent which provides strong evidence for endogenous flow and the backward rotation of folds produced by undertow of the underlying lava ridges near flow margins verge towards the flow front demonstrating that exogenous flow becomes increasingly important at the point of advance in both south coulee and obsidian dome block sizes are largest near the vent and gradually decrease towards the flow front the gradual decrease in block size with increasing distance from the vent likely reflects decreasing effusion rates from the conduit we interpret our high resolution field measurements under the lens of analytical solutions to fluid dynamic models to estimate emplacement timescales and associated rates we calculate relatively abbreviated eruptive timescales ranging from 1 month to

telkibanya lava domes lithofacies architecture of a miocene rhyolite field tokaj mountains carpathian pannonian region hungary abstract this work focuses on the miocene telkibanya lava dome field tokaj mountains hungary proposed as an example of poorly investigated lithofacies architecture of old silicic lava dome fields a detailed fieldwork combined with petrographic and radiometric k ar dating analyses allows us the redefinition of the volcano stratigraphy of a 25 km2 area and the recognition of two temporary different generation of domes that grew in a subaerial environment 12 cohesive and autoclastic lithofacies are identified and grouped together to document the internal variability of the domes as well as the erosional phases that affected the lithofacies architecture furthermore stratigraphy lithofacies association and morphology allow recognizing the areal distribution of 5 lithosomes lava flows coulees or domes all these findings represent a major breakthrough in the identification and interpretation of the volcanic processes that control the growth of silicic lava domes and their products in late miocene environment of carpathian pannonian region

the evolution of an active silicic lava flow field an etm perspective an active dacitic lava flow began advancing down the south flank of the caliente dome unit santiaguito volcano guatemala during july 1999 by january 2002 continued activity had built a 1 km2 66 106 m3 flow field using a time series of landsat 7 etm images and field observations the evolution and characteristics of this flow field are described throughout the period of emplacement flow front advance rates have been extremely slow 2 13 m day 1 consistent with a viscosity of 109 1010 pa s however extremely efficient thermal insulation has allowed flow fronts to extend up to 3 75 km from the vent in spite of extrusion rates of just 0 5 1 6 m3 s 1 surface temperatures along most of the flow are less than 75 c and typically 40 c such surface temperatures result in extremely low rates of heat loss and thus core cooling of just 0 03 0 09 c h 1 or 0 01 0 12 c m 1 the flow field itself clearly displays the same systematic spatial variations in structure and morphology as described by lipman and banks prof pap geol surv u s 1350 1987 1527 for a basaltic a a flow where a stable and then transitional channel zone feeds a distal area of dispersed flow the stable channel dominates the proximal and medial sections of the flow field and comprises a 90 375 m wide channel flanked by levees that are up to 117 m high a marked increase in the flow area and thickness occurred between january 2001 and january 2002 and was coincident with an increase in the extrusion rate from 0 5 0 7 to 1 2 1 6 m3 s 1 however this increase in extrusion rate did not bring an increase in flow lengths indicating that the flow may have reached its cooling limited length around january 2001

rates of tectonic uplift in the corinth and megara basins central greece we present evidence of the rates of late quaternary tectonic uplift that have affected parts of central greece during this period of active extension and basin formation dual lines of evidence indicate upper pleistocene to holocene uplift rates of the order of 0 3 mm yr 1 for the corinth and megara basins first u series disequilibrium ages of acropora sp corals from uplifted marine sediments are used to derive minimum average rates of vertical displacement since deposition second the geometries of cyclical transgressive sequences and of erosional terraces are consistent with the radiometric evidence and the known history of late quaternary sea level fluctuations two types of uplift are distinguished on the basis of structural relationships 1 fault block rotation about a horizontal axis tilting in response to footwall uplift on the active normal fault bounding the alkyonides gulf and 2 a more regional uplift which affects the corinth basin and peloponnesos to the south the results of u series dating are discussed in the light of initial 234u 238u activity ratios derived from the coral samples which are higher than for average marine waters 1 17 1 31 compared to 1 14 these values may be related to a variable freshwater input to the structurally confined gulf of corinth or alternatively they may reflect a previously higher global 234u 238u activity ratio in marine waters or post mortem enrichment in 234u although the mechanism of the latter is not yet understood

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

the unique radar properties of silicic lava domes 1 silicic lava domes exhibit distinct morphologic characteristics at scales of centimeters to kilometers multiparameter radar observations capture the unique geometric signatures of silicic domes in a set of radar scattering properties that are unlike any other natural geologic surfaces backscatter cross section values are among the highest observed on terrestrial lava flows and show only a weak decrease with incidence angle cross polarization backscatter hv shows a unique behavior increasing with increasing wavelength circular polarization ratios are relatively high in the 0 3 0 95 range and increase with increasing wavelength field measurements of boulder size frequency distributions and microtopography indicate that silicic dome surfaces are among the roughest ever measured rms heights at a 1 m lateral scale range from 13 cm to 50 cm rms slopes at 1 m spacing range from 12 to 43 degrees modeling of the scattering behavior suggests it results from a combination of rough surface facet scattering and scattering from block edges that act as a random collection of dipoles the unusual wavelength dependence of the radar parameters appears to result from a higher component of edge scattering at large wavelengths producing for example higher cross polarized backscatter at p band 68 cm steep sided volcanic domes on venus superficially resemble terrestrial silicic domes in plan view gross morphology but few similarities remain when the radar scattering and three dimensional shapes of the features are compared the unique radar scattering properties suggest that such volcanic surfaces can be identified with multiparameter radar observations in future planetary radar missions and in active terrestrial volcanoes where dome development can represent serious hazards

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

corinth rift margin uplift new evidence from late quaternary marine shorelines 1 new evidence for uplift of the southern margin to the corinth rift one of the world s most rapidly extending continental regions defines an area of uniform uplift separating a more rapidly uplifting western rift flank from a slowly backtilting eastern flank this major tectonic boundary coincides with geophysical evidence for a junction between flat underlying subducted oceanic plate and steep subduction we propose that trench rollback by the anatolian plate over the subducting african plate has led to differential uplift and possible migration of active faulting at the southern rift margin in the last few million years

lro observations of morphology and surface roughness of volcanic cones and lobate lava flows in the marius hills 1 the volcanic domes cones sinuous rilles and pyroclastic deposits of the marius hills region of the moon 13 4 n 304 6 e represent a significant episode of magmatic activity at or near the lunar surface that is still poorly understood comparisons between lroc nac block populations mini rf data and diviner derived rock abundances confirm that blocky lava flows comprise the domes of the marius hills 8 m features measured by diviner indicate that the domes are not rich in silica and are not significantly different than surrounding mare materials lroc observations indicate that some of the dome building lava flows originated directly from volcanic cones many of the cones are c shaped while others are irregularly shaped and local topography and lava eruptions affect cone shape in general the cones are morphologically similar to terrestrial cinder and lava cones and are composed of varying amounts of cinder spatter and lava many of the cones are found in local groupings or alignments the wide range of volcanic features from broad low domes to steep cones represents a range of variable eruption conditions complex morphologies and variable layering show that eruption conditions were variable over the plateau

morphology of rubbly pahoehoe simple flows from the deccan volcanic province implications for style of emplacement abstract lava flows with preserved bases and brecciated upper crusts constitute a morphological type that differs in character from typical pahoehoe and a a such flows have been reported from many provinces around the world previous studies had referred to these flows informally as pahoehoe flows with rubbly tops broken top pahoehoe and rubbly pahoehoe recent studies have formally applied the latter term to describe parts of the well studied laki flow in iceland as well as flows from the columbia river basalt province rubbly pahoehoe flows are abundant in the upper stratigraphic formations of the deccan volcanic province dvp and are more commonly known as simple flows this study presents detailed observations of such flows from various parts of the dvp and discusses their implications for understanding flow emplacement these flows which appear to be single units at the outcrop scale are generally much thicker and significantly more extensive than individual pahoehoe lobes that dominate the lower formations of the deccan stratigraphy they are characterised by preserved gently undulating tachylitic bases but variably disrupted crustal zones that grade into flow top breccias the breccias are constituted of highly vesicular and oxidised fragments of varying sizes that appear to have been derived from previously formed pahoehoe crusts previous work has indicated that the morphology of these flows might be related to initial inflation accompanied by rapid volatile exsolution and an increase in effusion rate and or viscosity with time this agrees reasonably well with the qualitative and quantitative models of emplacement developed for the laki flow the abundance of such flows in the upper formations of the deccan stratigraphy clearly hints at a significant shift in the nature of the deccan eruptions this could be indicative of higher eruption rates during this period this in turn raises the possibility of hazardous impact on the climate during the eruption of these flows which is also discussed in the paper

the terraces of corinth gerrce a detailed record of eustatic sea level variations during the last 500 000 years abstract between corinth and xylokastro 20 marine terraces reflect the interaction of the northern peloponnese uplift and the global eustatic sea level fluctuations during the last 500 000 years correlation of the terraces with oxygen isotope records in deep sea cores allowed accurate dating of these fossilized transgressive shorelines curves of altitude versus age have been plotted they show a regular decrease of the uplift rate and a frequent return of the sea level very close to the present day one not only during the interglacial periods 5 7 9 11 13 but also during glacial periods 3 1 3 3 6 8 the alternative would be to suppose very complicated and highly improbable vertical movements of the substratum to explain the regularity of the curves the rhythm of these high sea levels is around 20 30 ka since at least 330 000 years ago

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

subglacial lake ellsworth a candidate for in situ exploration in west antarctica radio echo sounding reveals a 10 km long lake beneath 3 4 km of ice near the ellsworth mountains in west antarctica 20 km from the ice divide subglacial lake ellsworth is located within a distinct topographic hollow which is 1 5 km deeper than the surrounding bed judging by bed slopes flanking the lake the water depth is at least 10s of metres calculations of basal temperature reveal the ice base to be warm both now and during full glacial periods as the environments of subglacial lakes are broadly similar life may be expected in lake ellsworth as in any other given this its physical characteristics and the fact that the west antarctic ice sheet has been accessed on several occasions lake ellsworth is an excellent candidate for in situ examination

spectral evidence of volcanic cryptodomes on the northern plains of mars abstract the composition and detailed morphology of dome shaped features located in western arcadia planitia and just west of utopia planitia were examined in this study utilizing data from mars reconnaissance orbiter and mars odyssey sensors the domes have diameters averaging 1 5 km and heights averaging 160 m and are generally dark toned although some are lighter toned or have split dark and light toned surfaces the domes are surrounded by annular deposits comprising with increasing distance from the domes dark toned aprons light toned aureoles and dark toned aureoles compact reconnaissance imaging spectrometer for mars crism data over several areas in the western arcadia region show that spectra from the flanks of several domes have 1 and 2 m absorption features consistent with the presence of olivine and a high ca pyroxene nominally augite modified gaussian model mgm analysis of these spectra indicates fe rich olivine compositions the tops of domes and the aprons surrounding many domes have negative sloping flat spectra in the near infrared which is consistent with tachylite rich glassy compositions high resolution imaging science experiment hirise images over several domes indicate that relatively high thermal inertia values associated with the tops of domes can be attributed to boulder strewn surfaces hirise images also reveal that light toned aureoles around domes consist of crenulated ground resembling brain terrain textures previously described for ice rich concentric crater fill elsewhere on the northern plains the plains surrounding the domes also display lineations that are interpreted to be lava channels or tubes the combination of volcanic and ice related features are consistent with the domes having formed as cryptodomes in the near sub surface we suggest that the domes could be basaltic in composition if the magmas were degassed and or highly crystallized and thus more viscous than typical basaltic magmas the intrusion of these magmas into an ice rich horizon would have produced a pervasively jointed chilled margin on the domes which once the domes were exposed would have mechanically weathered to form the dark aprons the domes could have served as local centers for ice accumulation during periods of high orbital obliquity which ultimately would have led to the formation of the brain terrain surrounding the features the domes represent late stage volcanic products on the northern plains of mars and associated features provide more evidence for the role that ice accumulation and modification has played in recent martian history

lava dome growth and mass wasting measured by a time series of ground based radar and seismicity observations range and intensity measurements of the change in summit lava 1 5 10 6 m 3 22 2 avtis range measurements to measure the talus growth 3 9 10 6 m 3 57 and 3 rockfall seismicity to measure the pyroclastic flow deposit volumes 1 4 10 6 m 3 21 which gives an overall dense rock equivalent extrusion rate of about 7 m 3 s 1 these figures demonstrate how efficient nonexplosive lava dome growth can be in generating large volumes of primary clastic deposits a process that by reducing the proportion of erupted lava stored in the summit region will reduce the likelihood of large hazardous pyroclastic flows

volcano ice interactions at prestahnukur iceland rhyolite eruption during the last interglacial glacial transition prestahnukur is a 570 m high rhyolite glaciovolcanic edifice in iceland s western rift zone with a volume of 0 6 km 3 uniform whole rock mineral and glass compositions suggest that prestahnukur was constructed during the eruption of one magma batch ar ar dating gives an age of 89 24 ka which implies eruption during the transition oxygen isotope substages 5d to 5a between the eemian interglacial and the weichselian glacial period prestahnukur is unique among published accounts of rhyolite tuyas because a base of magmatically fragmented tephra appears to be absent instead basal exposures consist of glassy lava lobes and coarse hyaloclastite above which are single and multiple lava sheets with matrix supported basal breccias and hyaloclastite upper carapaces steepening ramp structures at sheet termini are interpreted as ice contact features interactions between erupting magma and water ice have affected all lithologies a preliminary model for the construction of prestahnukur involves an effusive subglacial eruption between 2 19 years duration which never became emergent into an ice sheet over 700 m thick if 700 m of ice had built up during this interglacial glacial transition this would corroborate models arguing for the swift accumulation of land based ice in rapid response to global cooling

block size distributions on silicic lava flow surfaces implications for emplacement conditions we determined block size distributions on the surfaces of holocene silicic lava flows at the inyo domes and the medicine lake volcano and studied the development of blocks on the active mount st helens and mount unzen lava domes to better understand the emplacement history of young viscous flows we measured block chord lengths along perpendicular 25 m long transects within vent jumbled and ridged morphologic units vent regions generally contain the largest average block sizes and largest range of average blocks whereas ridged areas tend to have the smallest average blocks observations at the active mount st helens and mount unzen lava domes show that block size distributions reflect stress conditions during flow high extrusion rates produce small primary blocks and lead to rapid fracturing of the flow surface whereas low extrusion rates allow large slabs to form in the vent area and lead to less severe fragmentation a dramatic increase in the size of blocks evident in active vent regions may indicate a significant decrease in eruption rate and thus could signal the cessation of extrusion however if the extrusion rate is too high or the cooling rate too low a rigid crust and accompanying blocks will not form on an eruptive time scale blocks may fracture through mechanical and thermal processes as they move downslope most silicic lava flows reach a steady state downslope where the average block size at the surface remains in the 20 30 cm size range with increasing distance from the vent fines blocks 12 cm do not accumulate on the flow surface because they slip toward the flow interior through void spaces between surface blocks we therefore expect long silicic lava flows to have blocky surfaces throughout their lengths an important consideration for evaluation of planetary lava flow emplacement

automated identification of lava flow structures using local fourier spectrum of digital elevation data 1 the rheological parameters of a lava flow can be inferred by studying structural features on the solidified lava surface we have developed a technique using the s transform a localized fourier transform to analyze and interpret digital elevation data we examined structural features of a silicic lava flow the medicine lake dacite flow in california the s transform accurately identified and located both repeating and single instance structures several classes of structures were identified in the data including the following localized short wavelength features 1 3 3 6 m in wavelength identified as large blocks and repeating medium wavelength features 5 8 10 16 18 26 30 36 and 56 67 m in wavelength identified as multiple generations of crustal folding fold wavelengths determined by the s transform and a model of compressional folding associated with near surface viscosity gradients were used to evaluate the rheology of the medicine lake dacite flow the similarity of the amount of strain during folding events and the wavelength ratio of successive generations of folding suggest that the flow rheology remained relatively constant during folding of the flow surface repeating long wavelength features 67 70 and 105 140 m wavelengths were identified as the spacing of crease structures crease structures were recognized by the absence of short wavelength features at the location of their smooth flanks and by a central spike corresponding to the central trough the limitations and applicability of this approach lie in the accuracy and resolution of the digital elevation data used

archaeological and geomorphological indicators of the historical sea level changes and the related palaeogeographical reconstruction of the ancient foreharbour of lechaion east corinth gulf greece abstract study of the architectural morphological and constructional features of the coastal harbour installations of the ancient foreharbour of lechaion indicates that they were built or rebuilt during the period of the roman domination of corinth and has facilitated the reconstruction of the vertical movements and the palaeogeography of the coast on the basis of the current position of the sea level indicators including beachrocks fossilized uplifted and submerged marine notches and ancient coastal harbour installations and the relationship between them the sea level during the roman operation of the harbour was determined to be 0 90 m lower than at present furthermore the subsequent abandonment of the harbour and the siltation of its constructions were determined during two successive tectonic subsidence co seismic events the sea level rose by 2 0 m in total 1 60 m during the first event and 0 40 m during the second one a strong uplift tectonic event followed and the sea level dropped by 1 10 m this regression of the sea was responsible for the present shoreline morphology determination of the sea level fluctuation at the shore of the ancient harbour of lechaion allowed the palaeogeographical reconstruction of the coast in different stages related to these changes

geophysical surveys of earthquake induced liquefaction deposits in the new madrid seismic zone we explore the effectiveness and limitations of electrical and electromagnetic methods in imaging buried earthquake induced liquefaction deposits geophysical surveys conducted at liquefaction sites in the new madrid seismic zone nmsz in the central united states demonstrate that these subsurface imaging techniques can be useful tools in paleoseismology paleoseismological studies of liquefaction features provide one of the few means for estimating recurrence intervals of large earthquakes in the nmsz a region with widespread evidence of strong ground shaking but short instrumental record noninvasive geophysical methods minimize ground disturbance during these studies an attribute of particular importance when the studies are conducted at federally protected archaeological sites surveys such as those described here can be used to locate buried liquefaction deposits and to site trenches for detailed geologic studies

geophysical investigation for the detection of liquefaction phenomena in an archaeological site lechaion greece abstractthe area of lechaion located in the northeastern part of the peloponnese greece is of great archaeological interest because it represents the western harbor of ancient corinth and includes the remains of an early christian basilica destroyed during a series of earthquakes in the sixth century ad numerous depressions and buckling structures of circular and linear geometry observed on the decorated floor of the basilica are indicative of ground deformation processes possibly related to earthquake induced ground liquefaction electromagnetic with a conductivity meter ground penetrating radar gpr with 250 mhz shielded antenna and electric ert methods have been applied in an effort to study the properties of the substratum and to identify indicative features related to ground liquefaction phenomena the electromagnetic survey that was used as a reconnaissance method with both coil orientations provided valuable information through data processing identifying zones of higher conductivity t

rhyolitic volcano ice interactions in iceland iceland contains an abundance and diversity of rhyolitic edifices produced during volcano ice interactions glaciovolcanism that is unmatched by any other volcanic province with an estimated 350 km3 erupted during the past 0 8 ma from at least fifteen volcanic systems this review summarises research undertaken during the past decade and provides a new summary of the distribution of rhyolitic glaciovolcanic rocks erupted during the past 0 8 ma descriptions of effusion dominated edifices focus on the two best studied edifices the c 0 6 km3 and 570 m high prestahnukur edifice and the smaller volume 0 1 km3 drape of blahnukur both show little or no evidence of magmatic fragmentation i e driven by volatile exsolution but both show abundant evidence of quench fragmentation and meltback of ice walls a particular feature of prestahnukur is its sheet like lava bodies which are interpreted as sills that intruded the ice edifice interface rhyolitic tuyas are products of sustained eruptions into thick ice and form distinctive steep sided edifices with flat or broad dome like tops they are 300 700 m high with volumes up to 2 km3 though 0 5 1 0 km3 is more typical initial vigorous phreatomagmatic eruptions within well drained ice vaults build steep sided piles of tephra confined by ice walls gradual upwards increases in inflated clasts point to the decreasing involvement of meltwater and the increasing ability of the magma to vesiculate as the eruption progresses and terminates non explosive degassing produces lava caps up to 300 m thick oraefajokull is a stratovolcano illustrating complex volcano ice interactions generated when rhyolitic lavas erupt onto steeper slopes and encounter ice of variable thickness and properties e g fracturing eruptive units record dramatic ice thickness fluctuations of up to 500 m in valley glaciers between eruptions which emphasises that useful palaeoenvironmental information can be gleaned from detailed studies of volcano ice interactions considerable value is added when palaeoenvironmental information is combined with ar ar dating for example ar ar dating of two rhyolitic tuyas at torfajokull reveal that they erupted prior to the last glacial maximum when temperatures were at least 4 c cooler than the present day ar ar dating of prestahnukur suggests it erupted during the last interglacial glacial transition into over 700 m of ice which corroborates studies arguing for rapid accumulation of land based ice during global cooling

subglacial lake vostok not expected to discharge water the question whether antarctica s largest lake subglacial lake vostok exchanges water is of interdisciplinary relevance but has been undecided so far we present the potential pathway outlet location and threshold height of subglacial water discharge from this lake based on a quantitative evaluation of the fluid potential if water left lake vostok it would flow toward ross ice shelf discharge would occur first to the east of the southern tip of the lake at this location the bedrock threshold is 91 23 m higher than the hydrostatic equipotential level of lake vostok it is concluded that lake vostok is not likely to reach this level within climatic timescales and that no discharge of liquid water is to be expected we show that in absence of the ice sheet the lake vostok depression would harbor a lake significantly deeper and larger than the present aquifer

a new phenomenon in ancient liquefaction the draw in process its final stage abstract the authors propose a draw in phenomenon which occurs at the final stage of liquefaction three case studies of ancient liquefaction accompanied with draw in phenomena are examined from the karasu river district gunmna prefecture and the sanbusho and motoyashiki archeological sites niigata prefecture central japan the intrusion spout phenomenon is the primary or the main process of liquefaction caused by the increase in pressure of the liquefied layer during the earthquake the draw in phenomenon is the secondary or final process of liquefaction which occurs just after the earthquake the draw in structure is important to recognize in the field because only the final form of ancient liquefaction is preserved during the draw in stage the ancient surface soils are mixed and drawn in therefore the draw in structure is useful in order to estimate the age of ancient liquefaction events

examining rhyolite lava flow dynamics through photo based 3d reconstructions of the 2011 2012 lava flowfield at cordon caulle chile during the 2011 2012 eruption at cordon caulle chile an extensive rhyolitic flowfield was created in excess of 0 5 km3 in volume affording a unique opportunity to characterise rhyolitic lava advance in 2012 and 2013 we acquired approximately 2500 digital photographs of active flowfronts on the north and east of the flowfield these images were processed into three dimensional point clouds using structure from motion and multi view stereo sfm mvs freeware from which digital elevation models were derived sequential elevation models separated by intervals of three hours six days and one year were used to reconstruct spatial distributions of lava velocity and depth and estimate rheological parameters three dimensional reconstructions of flowfronts indicate that lateral extension of the rubbly a like flowfield was accompanied by vertical inflation which differed both spatially and temporally as a function of the underlying topography and localised supply of lava beneath the cooled upper carapace compressive processes also drove the formation of extensive surface ridges across the flowfield continued evolution of the flowfield resulted in the development of a compound flowfield morphology fed by iterative emplacement of breakout lobes the thermal evolution of flow units was modelled using a one dimensional finite difference method which indicated prolonged residence of magma above its glass transition across the flowfield we compare the estimated apparent viscosity 1 21 4 03 1010 pa s of a breakout lobe based on its advance rate over a known slope with plausible lava viscosities from published non arrhenian temperature viscosity models and accounting for crystallinity 50 vol there is an excellent correspondence between viscosity estimates when the lava temperature is taken to be magmatic despite the breakout being located 3 km from the vent and advancing approximately nine months after vent effusion ceased this indicates the remarkably effective insulation of the lava flow interior providing scope for significant evolution of rhyolitic flow fields long after effusive activity has ceased

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

distinguishing between primary and secondary emplacement events of blocky volcanic deposits using rock size distributions 1 rock size characteristics in rock avalanches and blocky lava flows are different and statistical techniques can be used both to distinguish between and to constrain the different emplacement mechanisms of these two processes at the chaos jumbles rock avalanche deposit in california rock sizes decrease as a function of distance the rock avalanche mechanism is an example of a secondary process that can only break existing blocks in contrast lava flows at sabancaya peru were emplaced by primary mechanisms capable of creating as well as breaking blocks these deposits exhibit uniform block sizes as functions of distance and significantly larger blocks overall than chaos jumbles rock sizes at inyo domes also emplaced by a primary process are significantly smaller in areas with compressional ridges as compared to vent or jumbled areas

water exchange between the subglacial lake vostok and the overlying ice sheet it has now been known for several years that a 200 km long lake called lake vostok lies beneath the ice sheet on which sits vostok station in antarctica the conditions at the base of the ice sheet above this subglacial lake can provide information about the environment within the lake including the likelihood that it supports life here we present an analysis of the ice sheet structure from airborne 60 mhz radar studies which indicates that distinct zones of basal ice loss and accretion occur at the ice water interface subglacial melting and net ice loss occur in the north of the lake and across its 200 km long western margin whereas about 150 m of ice is gained by subglacial freezing in the south this indicates that significant quantities of water are exchanged between the base of the ice sheet and the lake waters which will enrich the lake with gas hydrates cause sediment deposition and encourage circulation of the lake water

silicic lava dome growth in the 1934 1935 showa iwo jima eruption kikai caldera south of kyushu japan the 1934 1935 showa iwo jima eruption started with a silicic lava extrusion onto the floor of the submarine kikai caldera and ceased with the emergence of a lava dome the central part of the emergent dome consists of lower microcrystalline rhyolite grading upward into finely vesicular lava overlain by coarsely vesicular lava with pumice breccia at the top the lava surface is folded and folds become tighter toward the marginal part of the dome the dome margin is characterized by two zones a fracture zone and a breccia zone the fracture zone is composed of alternating layers of massive lava and welded oxidized breccia the breccia zone is the outermost part of the dome and consists of glassy breccia interpreted to be hyaloclastite the lava dome contains lava with two slightly different chemical compositions the marginal part being more dacitic and the central part more rhyolitic the fold geometry and chemical compositions indicate that the marginal dacite had a slightly higher temperature lower viscosity and lower yield stress than the central rhyolite the high temperature dacite lava began to effuse in the earlier stage from the central crater the front of the dome came in contact with seawater and formed hyaloclastite during the later stage low temperature rhyolite lava effused subaerially as lava was injected into the growing dome the fracture zone was produced by successive fracturing ramping and brecciation of the moving dome front in the marginal part hyaloclastite was ramped above the sea surface by progressive increments of the new lava the central part was folded forming pumice breccia and wrinkles subaerial emplacement of lava was the dominant process during the growth of the showa iwo jima dome