io hot spots in 1991 results from europa occultation photometry and infrared imaging abstract during the winter of 1991 an unusually favorable series of occultations of io by europa took place we obtained infrared photometry of four of these events at the united kingdom infrared telescope at wavelengths of 5 0 or 3 4 m in order to investigate the nature and distribution of volcanism on io by observing the occultation of the volcanic hot spots by the limb of europa observations at 3 4 m on 1991 01 08 detected a possible small hot spot in the northern hemisphere observations at 5 0 m on 1991 02 27 detected and resolved the major hot spot loki which had a diameter of 170 km and had three times its voyager 1 flux and also detected the voyager hot spot pele at about half its voyager 1 flux a 5 0 m occultation of pele on 1991 03 06 when loki was not occulted indicated no significant flux change since the week before infrared images of io obtained at the nasa infrared telescope facility between october 1990 and april 1991 show that the europa occultations occurred during a period of unusually high activity at loki loki showed very little thermal emission in observations between 1990 10 12 and 1990 11 27 but increased in flux by a factor of 10 in 32 days by 1991 12 29 loki then remained bright in all observations until 1991 03 26 but had begun to fade on 1991 04 09 such rapid variations in flux over such a large area are remarkable multiwavelength observations indicate that loki increased in temperature during the brightening and that materials hotter than 630 k were exposed at loki the possible pele type volcanoes surt and aten unlike pele were not detected with 3 8 m flux upper limits of about 8 gw m 1 str 1

global near ir maps from gemini n and keck in 2010 with a special focus on janus patera and kanehekili fluctus abstract we have imaged io in the near infrared 1 5 m with adaptive optics on the 10 m w m keck ii and the gemini north telescopes we have constructed global maps from the data taken in 2010 although numerous hot spots are visible the maps are dominated by two volcanic centers loki patera and kanehekili fluctus we have examined in detail the thermal emission from janus patera and kanehekili fluctus using images obtained between 2003 and 2010 and have created a timeline of volcanic activity at these locations utilizing data from a wide variety of sources based on our data and this timeline we find that the thermal emission from janus patera is relatively steady indicative of an active lava lake the thermal emission from kanehekili fluctus however is quite variable and is indicative of the emplacement of extensive lava flows in 2010 the thermal emission from this location was 10 times higher than ever seen before indicative of a particularly voluminous eruption of lava

spatially resolved observations of the forbidden so a1δ x3σ a1δ x3σ rovibronic transition on io during an eclipse and a volcanic eruption at ra patera abstract we report observations of io that were conducted on ut 12 november 2002 with the nirspec spectrometer coupled to the adaptive optics system on the 10 m keck ii telescope we detected a bright eruption in the ra patera area with a color h k band temperature of 1031 110 k over an effective area of 1 5 0 2 km 2 the eruption was associated with a hot plume which revealed itself through so emission at a rate of 9 3 10 25 photons s 1 about 10 15 of io s total so flux at the time the rotational temperature was 700 150 k no significant so emission was received from io s northern hemisphere north of ra patera loki roughly 50 of the total so emission came from the equatorial region including ra patera janus and loki and 40 came from the south the rotational temperatures typically measured between 600 and 1000 k the emissions are most likely produced by so molecules ejected out of volcanic vents in the excited a 1 state our narrow band images that span the so emission band suggest that a source near io s south pole nemea may be a source of some of the southern so emissions

microstructure and texture in experimentally folded single layer rock salt abstract buckling experiments on single layers of fine grained artificial polycrystalline rock salt embedded in a plasticine matrix have been performed in the temperature range of 185 200 c under a confining pressure of 10 bars in a plane strain pure shear apparatus strain rates ranged from 2 5 10 7 to 4 7 10 7 layers with an aspect ratio of 7 deformed without buckling but when this ratio was increased to 13 layers deformed by buckling and produced one wavelength of a sinusoidal fold the stress strain and time strain curves indicate that folding is initiated at about 7 to 8 of bulk deformation the layer parallel shortening and thickening continues with progressive folding the changes in the arclength thickness and limb dip show that initially the fold growth is slow and then becomes rapid the inner fold are is characterized by strong preferred dimensional grain orientation with the longer axis normal to the layer surface the axial ratio of grains gradually decreases towards the outer arc the stresses on the outer are have been relieved mainly by the development of tension fractures in the limbs the grains are elongated normal to the layer however close to the surfaces the grains are very fine and exhibit a tendency to elongate along the layer surface the preferred lattice orientation of 100 110 and 111 planes in halite have been determined by x ray texture goniometry and the pole figures are partially comparable to the textures in natural fold from salt domes

high resolution keck adaptive optics imaging of violent volcanic activity on io io the innermost galilean satellite of jupiter is a fascinating world data taken by voyager and galileo instruments have established that it is by far the most volcanic body in the solar system and suggest that the nature of this volcanism could radically differ from volcanism on earth we report on near ir observations taken in february 2001 from the earth based 10 m w m keck ii telescope using its adaptive optics system after application of an appropriate deconvolution technique mistral the resolution 100 km on io s disk compares well with the best galileo nims resolution for global imaging and allows us for the first time to investigate the very nature of individual eruptions on 19 february we detected two volcanoes amirani and tvashtar with temperatures differing from the galileo observations on 20 february we noticed a slight brightening near the surt volcano two days later it had turned into an extremely bright volcanic outburst the hot spot temperatures 1400 k are consistent with a basaltic eruption and being lower limits do not exclude an ultramafic eruption these outburst data have been fitted with a silicate cooling model which indicates that this is a highly vigorous eruption with a highly dynamic emplacement mechanism akin to fire fountaining its integrated thermal output was close to the total estimated output of io making this the largest ionian thermal outburst yet witnessed

io heat flow from dark volcanic fields abstract dark flow fields on the jovian satellite io are evidence of current or recent volcanic activity we have examined the darkest volcanic fields and quantified their thermal emission in order to assess their contribution to io s total heat flow loki patera the largest single source of heat flow on io is a convenient point of reference we find that dark volcanic fields are more common in the hemisphere opposite loki patera and this large scale concentration is manifested as a maximum in the longitudinal distribution near 200 w consistent with usgs global geologic mapping results in spite of their relatively cool temperatures dark volcanic fields contribute almost as much to io s heat flow as loki patera itself because of their larger areal extent as a group dark volcanic fields provide an asymmetric component of 5 of io s global heat flow or 5 1012 w

single layer folding in marble and limestone an experimental study folding experiments have been carried out on single layers of carrara marble and solnhofen limestone at a confining pressure of 275 bars temperature of 400 c and strain rates of 5 5 10 7 to 8 2 10 7 the marble and limestone layers were embedded in a rock salt matrix and in a matrix of a mixture of 60 fine grained halite and 40 fine grained calcite respectively and deformed to different percentages of bulk shortening aspect ratios of the layers varied between 11 25 and 15 the stress strain relationship reveals that strain increased with a very small increment in compressive stresses once folding was initiated with progressive deformation the bulk strain is compensated by folding along one fold hinge the resulting folds are concentric and a combination of class 1a 1b and 3 type the changes in the arc length layer thickness limb dip and wavelength with progressive folding in marble layers are discussed the microstructure and texture of the folded marble and limestone layers have been investigated optically and by means of an x ray texture goniometer the inner fold arc exhibits a strong preferred orientation whereas in the outer fold are the preferred orientation is poorly developed differences in the fabric in medium grained marble and fine grained limestone layers have been attributed to the difference in mechanism of deformation

resonant interaction of acoustic waves with subaqueous bedforms sand dunes in the south china sea the large subaqueous sand dunes in the south china sea are expected to produce the coupling of energy between acoustic normal modes in this letter resonant interaction between acoustic propagating modes and subaqueous bedforms are numerically investigated as a function of bedform wavelength acoustic frequency and bedform packet length the results demonstrate that bedform wavelength impacts acoustic mode coupling behavior with the principal transfer of energy occurring between acoustic modes whose eigenvalue difference is equal to the peak value in the bedform wavenumber spectrum the observed effect of wavelength is greater than that of acoustic frequency and bedform packet length

volcanic eruptions on io nine eruption plumes were observed over a period of 6 1 2 days during the voyager 1 encounter with io during the voyager 2 encounter 4 months later eight of these eruptions were still active the largest plume viewed by voyager 1 became inactive sometime between the two encounters however a major eruption occurred at surt sometime between the two encounters and deposited an ejecta blanket comparable in size to those associated with the largest plumes the plumes range in height from about 60 to over 300 km with corresponding ejection velocities of about 0 5 to 1 0 km s where topographic information exists plumes 1 and 8 the plume source is located on level plains rather than topographic highs and consists of either fissures or calderas with the exception of plume 1 pele the brightness distribution monotonically decreases from the core to the top of the plume the shape and brightness distribution together with the pattern of the surface deposit of at least plume 3 prometheus can be simulated by a ballistic model in which the ejection velocity is constant 0 5 km s and ejection angles vary from vertical 0 to 55 the brightness distribution of plume 1 is probably better explained by a shock front near the top of the plume numerous surface deposits similar to those associated with active plumes probably mark the sites of recent eruptions the distribution of active and recent eruptions appears to be concentrated in the equatorial regions and indicates the volcanic activity is more frequent and intense in the equatorial regions than the polar regions this suggests that the depositional rate is greater and the surface age younger in the equatorial regions which may account for the darker polar regions the geologic setting of certain plume sources and the very large reservoirs of volatiles required for the active eruptions suggests that sulphur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes

enhanced acoustic mode coupling resulting from an internal solitary wave approaching the shelfbreak in the south china sea internal waves and bathymetric variation create time and space dependent alterations in the ocean acoustic waveguide and cause subsequent coupling of acoustic energy between propagating normal modes in this paper the criterion for adiabatic invariance is extended to the case of an internal solitary wave isw encountering a sloping bathymetry i e continental shelfbreak predictions based on the extended criterion for adiabatic invariance are compared to experimental observations from the asian seas international acoustics experiment using a mode 1 starter field results demonstrate time dependent coupling of mode 1 energy to higher adjacent modes followed by abrupt coupling of mode 5 7 energy to nonadjacent modes 8 20 produces enhanced mode coupling and higher received levels downrange of the oceanographic and bathymetric features numerical simulations demonstrate that increasing isw amplitude and seafloor slope enhance the coupling of energy to adjacent and nonadjacent modes this enhanced coupling is the direct result of the simultaneous influence of the isw and its proximity to the shelfbreak and compared to the individual effect of the isw or shelfbreak has the capacity to scatter 2 4 times the amount of acoustic energy from below the thermocline into the upper water column beyond the shelfbreak in realistic environments

calcite fabrics in the hinge zones of experimentally folded single layers of marble and limestone abstract the preferred orientations of poles to 0006 and 10 1 4 planes in calcite have been studied in the inner and outer arcs of experimentally produced single layer buckle folds in carrara marble and solnhofen limestone the textures produced in the medium grained marble differ from that of the fine grained limestone further the pole figures from the inner fold arcs are characterized by a general orthorhombic symmetry and a strong preferred orientation of the crystallographic fabric elements whereas that from the outer fold arcs generally exhibits a triclinic symmetry and a weak preferred orientation the difference in the pole figures in medium grained marble and fine grained limestone is attributed to the mechanism of internal deformation in calcite the orthorhombic symmetry of the pole figures from the inner fold arc suggests a coaxial strain history in this zone whereas the triclinic symmetry of the fabric diagrams from the outer fold arcs is attributed to a non coaxial strain history

ground based observations of volcanism on io in 1999 and early 2000 ground based observations of volcanism on io during the period of the 1999 and early 2000 galileo close flybys have detected several types of activity providing information which complements the spacecraft observations at loki a brightening began between august 25 and september 9 and continued through february on august 2 a major outburst was observed near 14 n 74 w whose brightness corresponds to an area of approximately 350 km 2 at a temperature of 1100 k observations of eruptions in late june 9906a and in late november 9911a at tvashtar provide temporal and photometric constraints on activity also seen by galileo high resolution adaptive optics images provide further information on the fainter sources distributed across the surface

keck ao observations of io in and out of eclipse abstract we present adaptive optics ao observations of io taken with the w m keck ii telescope on 18 december 2001 ut before the satellite went into eclipse and while it was in jupiter s shadow making these kind of io in eclipse observations as well as the associated data reduction and analysis are challenging hence one focus of the paper is to explain the methods and tools used for these data sets for the sunlit images io itself was used as the wavefront reference source while nearby ganymede was used as reference star when io was in eclipse observations were obtained in k l and m bands the sunlit images have been deconvolved using mistral the io in eclipse data were deconvolved with idac and mistral the former gives better results both in absolute photometry and in matching the original images we determined the flux densities of the hot spots from the original io in eclipse data with starfinder as well as from the deconvolved images by integrating the intensity over the relevant areas we determined the highly anisoplanatic psf via a fft method from the original data and used this in starfinder and as a starting psf for idac and mistral we derived temperatures and areal coverage of all 19 spots detected in both k and l band images of io in eclipse we also determined temperatures and areal coverage of the hot spots visible on the l and m band images of sunlit io most volcanoes contain a compact hot core 10 km2 at 600 800 k within a larger area at lower temperatures e g 102 104 km2 at 300 500 k the total heat flow contributed by these active volcanoes is 0 2 w m 2 8 of the average global heat flow measured at 5 20 m by veeder et al j geophys res 99 1994 17095

tidal dissipation surface heat flow and figure of viscoelastic models of io abstract the distribution of hot spots on io s surface and io s figure constrain models of io s interior voyager observations indicate that most hot spots and volcanic plumes are close to the equator recently however it has been proposed that a large low albedo feature in the south polar region may be the source of 40 of the surface heat flow we calculate spatial distributions of the dissipation rate surface heat flow and the figures of three and four layer maxwell rheology models of io by using the correspondence principle the models are required to satisfy the observed surface heat flow constraint and are consistent with the composition of a dehydrated c2 chondrite they consist of an inviscid fe fes core and viscoelastic silicate mantle and lithosphere layers a comparison of the calculated equilibrium figure with the observed figure of io supports the chosen core radius of 980 km in addition the four layer model has a partially molten asthenosphere a few tens of kilometers thick the preferred three layer model has a mantle shear modulus of 10 10 pa and a viscosity of 2 10 16 pa s consistent with rock properties the tidal dissipation rate for this model is largest along the polar axis integration of the dissipation rate over radius gives a surface heat flow with maxima at the poles and minima near the sub jovian and anti jovian points in contrast the dissipation rate in a molten or partially molten incompressible asthenosphere has maxima near the equator and is close to zero at the poles the asthenosphere dissipation rate is mainly a function of asthenosphere viscosity and thickness the thinner the asthenosphere the smaller is the required viscosity a 50 km thick asthenosphere requires a viscosity of about 10 8 pa s a strong south polar hot spot if it can be confirmed by infrared observation favors dissipation in the mantle but does not exclude dissipation in a partially molten asthenosphere equatorial hot spots and the concentration of prometheus type plumes near the equator favor asthenosphere heating but do not rule out deep mantle dissipation both asthenosphere and deep mantle heating may contribute to io s surface heat flow the properties of magma transport through the lithosphere and the planform of mantle convection might exert a control on the surface expression of heating at greater depth

experimental folding and fabric development in multilayered ice abstract deformation of multilayered crystalline ice in plane strain at 1 c and under a constant load has produced folds varying strain distributions and a variety of microfabrics three different specimen configurations were used to produce the folds 1 1 layers of polycrystalline ice separated by thin plastic films and unconstrained in the extension direction these formed large symmetric sinusoidal folds where layer parallel shear contributed to the fold shape 2 2 bonded plastic coated layers of polycrystalline ice constrained in the extension direction these developed symmetric disharmonie folds of one wavelength layer boundaries remained attached except in fold hinges and there was no evidence for layer boundary slip 3 3 multilayered fibrous ice unconstrained in the extension direction these produced gentle half wavelength buckles finite strain distributions were different in each experiment and varied between layers of different grain size the greatest strains were observed in the fine grained layers principal elongations fan about the axial surface of folds where layers have undergone buckling late in their deformation history under co axial deformation conditions the axes of the strain ellipses parallel the axes of bulk strain except in the constrained regions progressive deformation involving intracrystalline slip recrystallization and recovery processes serve to continuously modify the crystallographic fabric variation in the patterns of c axis preferred orientation correlate with strain variations and differences in deformation path the presence of a strong initial c axis orientation and grain shape distribution can also govern the strength of the final pattern of preferred orientation

a survey of io s volcanism by adaptive optics observations in the 3 8 μm thermal band 1996 1999 in this study we analyze a series of images of io obtained with the european southern observatory adaptive optics system adaptive optics near infrared system adonis at 3 8 m from 1996 to 1999 with particular emphasis on the observations carried out in late 1999 in support of the galileo flybys of io use of a new myopic deconvolution method myopic iterative step preserving algorithm mistral especially designed for planetary objects significantly improves the quality and the reliability of the reconstructed images using a simulation of artificial images of io we estimate the extent to which this algorithm is able to prevent noise amplification to better restore sharp edges and to preserve the initial photometry once this algorithm has been applied to our data and the solar reflected background has been subtracted we have 89 images of io available for search and temporal survey of the hot spots over 4 years in most cases the data acquired during two consecutive nights provide an almost global view of the surface of io we identify 20 hot spots for which we determine the coordinates and the brightness at 3 8 m as a function of time more than half of the hot spots were detected on all the images and were considered as persistent particular emphasis has been put on the brightest two hot spots loki and pele for which we obtain a center to limb variation curve a cosine curve for loki and a curve decreasing slightly faster than a cosine law for pele with possible physical interpretations the temporal variations of their activity have been derived over these 4 years and for loki compared with the results of other ground based surveys the variability of the other fainter sources has also been derived but with less accuracy we have also identified a few new hot spots some of which are transient such as a diffuse emission seen in september and november 1999 at the location of the upcoming tvashtar outburst the data are based on observations 58 f 1003 63 s 0260 and 64 s 0661 collected at the european southern observatory in la silla chile

a history of high temperature io volcanism february 1995 to may 1997 ground based observations of io s infrared thermal emission between february 1995 and may 1997 show several discrete brightenings for which we can constrain locations fluxes and durations several of these were brief high temperature events with temperatures up to at least 1500 k similar to but often smaller than the rare outbursts seen previously loki io s most powerful volcano was relatively active before and probably during galileo s december 1995 io flyby was faint during most of 1996 and began a major long lived brightening between february 20 and march 12 1997 thermal emission was not seen from ra patera site of an active plume in galileo images major outbursts were seen on march 2nd and september 27 1995

tablet boudinage of an anhydrite layer in rock salt matrix results from thermomechanical experiments abstract a single competent layer of anhydrite embedded in a matrix of incompetent rock salt was deformed in a flattening type of bulk deformation at temperature t 345 c strain rate 10 7 s 1 to a maximum finite strain e z 30 as the anhydrite layer was oriented perpendicular to the main shortening direction z the layer underwent equal layer parallel extension in all directions resulting in tablet shaped boudins boudinage results from tensile fracture of anhydrite the rock salt matrix on the other hand behaved viscously crystal plastic deformation of halite was accommodated by slip on 110 which led to formation and rotation of subgrains and a 001 maximum parallel to the principal shortening axis z an axisymmetric texture of halite however is present only in high strain domains at the contact to the anhydrite layer where the differential stress obtained from subgrain size of halite reaches maximum values of ca 6 mpa subgrains remote from the anhydrite layer yielded 2 3 mpa which is consistent with the flow stress recorded by the load cell of the machine the non isometric shape of the tablet boudins in plan view is indicated by the ratio between long and short axis r 1 2 1 9 and can be explained by the interaction of concentric and radial tensile fractures both the mean diameter of the tablet boudins in plan view w a and the number of boudins n show a linear relation to the layer thickness progressive finite strain results in a higher number and a smaller mean diameter of the boudins the thickness of the boudins h f is almost the same like the initial layer thickness h i while the aspect ratio w d w a h f decreases with finite strain the mean w d values obtained from all runs are ranging from ca 0 8 to ca 1 5 this range is much lower than the aspect ratio of boudins in viscous or brittle viscous layers but is similar to the aspect ratio expected from fracture saturation models the aspect ratio of the tablet shaped anhydrite boudins is further consistent with aspect ratios published so far for tensile fracture boudins which developed in a plane or constrictional type of bulk deformation

observations of nonlinear internal waves on the outer new england continental shelf during the summer shelfbreak primer study observations are presented of nonlinear internal waves on the outer new england continental shelf during the summer shelfbreak primer study conducted between july 26 and august 5 1996 current and temperature measurements were made with an upward looking acoustic doppler current profiler adcp located on the 147 m isobath near the shelfbreak and three vertical thermistor moorings located upshelf data from the adcp and two nearby thermistor chains show energetic internal tides propagating at roughly 0 9 m s 21 to the north northwest nearly perpendicular to the local topography with 10 15 cm s 21 horizontal currents and 15 30 m vertical displacements these waves evolve rapidly within a 5 8 km range into an undular internal tidal bore cross isobath barotropic tidal currents responsible for generating the internal tides are in the 5 12 cm s 21 range the bore formation is highly variable there is evidence of a correlation between internal tide steepening and a shelfbreak front jet orientation that is oppositely directed to the internal tide propagation there is no correlation between steepening and the jet s vertical shear statistics of the undular bores show rms travel time fluctuations from 0 8 to 1 7 hours and average tidal bore durations from 12 to 9 hours the average undular bore speed is 0 9 m s 21 with an rms fluctuation of 0 4 m s 21 the number of high frequency waves in the bore varies from 0 to 8 near the shelfbreak and increases to 30 waves 26 7 km upshelf the observed distribution function of temporal spacing between high frequency internal waves is spread between 4 and 20 min

active volcanism on io global distribution and variations in activity abstract io s volcanic activity has been monitored by instruments aboard the galileo spacecraft since june 28 1996 we present results from observations by the near infrared mapping spectrometer nims for the first 10 orbits of galileo correlate them with results from the solid state imaging system ssi and from groundbased observations and compare them to what was known about io s volcanic activity from observations made during the two voyager flybys in 1979 a total of 61 active volcanic centers have been identified from voyager groundbased and galileo observations of these 41 are hot spots detected by nims and or ssi another 25 locations were identified as possible active volcanic centers mostly on the basis of observed surface changes hot spots are correlated with surface colors particularly dark and red deposits and generally anti correlated with white so 2 rich areas surface features corresponding to the hot spots mostly calderas or flows were identified from galileo and voyager images hot spot temperatures obtained from both nims and ssi are consistent with silicate volcanism which appears to be widespread on io two types of hot spot activity are present persistent type activity lasting from months to years and sporadic events which may represent either short lived activity or low level activity that occasionally flares up sporadic events are not often detected but may make an important contribution to io s heat flow and resurfacing the distribution of active volcanic centers on the surface does not show any clear correlation with latitude longitude voyager derived global topography or heat flow patterns predicted by the asthenosphere and deep mantle tidal dissipation models however persistent hot spots and active plumes are concentrated toward lower latitudes and this distribution favors the asthenosphere rather than the deep mantle tidal dissipation model

acoustic mode coupling due to subaqueous sand dunes in the south china sea the large subaqueous sand dunes on the upper continental slope of the south china sea are expected to couple acoustic propagating normal modes in this letter the criterion of adiabatic invariance is extended to the case of a waveguide possessing bedforms using the extended criterion to examine mode propagation over the bedforms observed in the sand dune field in 2012 results demonstrate that bedforms increase mode coupling strength such that the criterion for adiabatic propagation is exceeded for waveguides with small bedform amplitude to water depth ratios increasing bedform amplitude enhances mode coupling numerical simulations confirm the extended criterion parameterization

loki io new ground based observations and a model describing the change from periodic overturn 1 loki patera is the most powerful volcano in the solar system we have obtained measurements of loki s 3 5 micron brightness from nasa s infrared telescope facility irtf and have witnessed a major change in eruptive behavior while loki brightened by a factor of several every 540 days prior to 2001 from 2001 through 2004 loki remained at a constant intermediate brightness we have constructed a quantitative model of loki as a basaltic lava lake whose solidified crust overturns when it becomes buoyantly unstable by altering the speed at which the overturn propagates across the patera we can match our ground based brightness data in addition we can match other data taken at other times and wavelengths by slowing the propagation speed dramatically we can match the observations from 2001 2004 such slowing could be due to a small change in volatile content in the lava

hinge migration as a mechanism of superimposed folding abstract paraffin wax analogue modelling of superimposed folding shows how early fold shape and orientation determine fold axis orientation type of interference pattern and mechanism of superposed folding during two successive deformations the behaviour depends on the angle between the first and second compression directions i when they are perpendicular to each other classic superposed folding with either domes and basins or folds with vertical axes develop depending on whether the earlier folds were open or closed ii when the two compression directions are oblique the earlier folds rotate the degree of rotation depends on the angle between the first folds and the later compression direction and is proportional to the amount of strain the orientations of the new folds are close to those of the earlier open folds the final deformation pattern consists of domains where the orientations of the axes depend on whether the early folds were previously either open or closed many early folds are reused to become later folds by the mechanism of hinge migration these results are consistent with the pattern of superimposed folding observed in the devoluy structure of the french alps they show that simply by studying the directions of fold axes in areas of superposed folding it is not possible to define compression directions moreover there is the possibility that superposed folding may go unnoticed if hinge migration has occurred

internal structure of io and the global distribution of its topography abstract the distribution of equatorial long wavelength topography on io consists of alternating basins and swells similar to the pattern expected if tidal heating in a thin asthenosphere controls the elevation of the surface through a conductive lithosphere in isostatic equilibrium the equatorial basin swell pattern is shifted in longitude with respect to theoretical tidal heating patterns however making the correlation between theoretical heat flow and elevation unclear we calculate global topography for multilayer io models with dissipation occurring in a viscous asthenosphere and a solid mantle two models are considered a thermal swell model in which topography and heat flow are positively correlated and a differentiated lithosphere model in which topography and heat flow are negatively correlated both models match the observed pattern of alternating basins and swells along the equator and moderate polar topography if about two thirds of the tidal heating occurs in the asthenosphere and about one third occurs in the underlying solid mantle the mean thicknesses of the model lithospheres are 35 km in the differentiated model and 150 km in the thermal swell model polar topography and the hypsometric distribution of elevations in the differentiated lithosphere model match the observations better than the thermal swell model in a differentiated lithosphere model consistent with the topography the asthenosphere is at least 50 km thick with viscosity about 100 mpa sec and is about 7 more dense than the lithosphere the mantle density exceeds the asthenosphere density by at least 10 the shift of the equatorial basin swell pattern suggests that io s lithosphere has recently undergone a zonal rotation of about 25

analysis of nonlinear internal waves in the new york bight this paper presents the results on internal wave analysis of the current meter mooring data in the new york bight from the sar internal wave signature experiment sarsex selective sets of current and temperature measurements are analyzed for a parametric study of internal wave characteristics and shear effects on wave parameters are studied based on the limited data from moorings the solitary wave theory has been extended for the wave evolution on a continental shelf by including dissipation and shoaling effects a series of numerical simulations are performed to demonstrate the relative importance of dissipation and shoaling effects from an observed initial wave packet at the upstream mooring the numerical evolution simulation compares reasonably well with the measurements at the distant mooring for the leading two large solitons

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

two new rare high effusion outburst eruptions at rarog and heno paterae on io observations obtained with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck ii telescope on mauna kea hawaii on 15 august 2013 at 15 30 ut revealed two large outburst class volcanic eruptions on io follow up observations five days later showed that both eruptions had substantially faded the most energetic eruption was at rarog patera at a location near 305 w 42 s a smaller one occurred further south at 310 w and 57 s close to heno patera total radiant fluxes at rarog patera on august 15 were of order 500 gw sr m at wavelengths between 2 and 4 m and close to 250 gw sr m at 1 6 m indicative of an effective temperature of 1040 k over an area of 120 km 2 and a total thermal emission of nearly 8 tw at heno patera the 4 m flux measured 250 gw sr m and 90 gw sr m at 2 2 m suggestive of an effective temperature of 720 k over an area of more than 300 km 2 and a total thermal emission of 5 6 tw fits of the davies davies a g 1996 icarus 124 1 45 61 io flow model indicate that these two eruptions are vigorous and the exposed surfaces are mostly very young no older than 4 5 min at rarog patera and a few hours at heno patera the model fits suggest that in both locations lava fountaining is taking place a highly energetic style of volcanism using follow up observations taken between august 20 and september 7 we estimate peak effusion rates between 5 10 4 and 10 5 m 3 s

discovery of hotspots on io using disk resolved infrared imaging active tidally driven volcanism on jupiter s satellite io1 2 was discovered in voyager images in 1979 voyager also detected the thermal emission from the volcanoes3 4 and this emission has since been monitored from earth using a variety of techniques employing single element infrared detectors5 10 because of io s small angular size no more than 1 2 arcsec however it has normally been possible to resolve and locate only the brightest individual hotspot loki although additional hotspots can be located at five year intervals during occultations of io by the other galilean satellites11 12 here we present first results using two new techniques for ground based observation of io s hotspots first use of an infrared array camera allowed us to exploit the mauna kea observatory s excellent atmospheric stability to obtain direct infrared images of io with resolution better than 0 5 arcsec this allowed us to see more than one hotspot on io in jupiter eclipse in jupiter s shadow second we used the camera to make the first observations of the jupiter occultation disappearance behind jupiter of the hotspots these new techniques have revealed and located at least three hotspots and will now permit routine ground based monitoring of the locations temperatures and sizes of multiple hotspots on io

io heat flow from small volcanic features abstract we identify nine new faint thermal sources on io via color ratio images constructed from relatively high spatial resolution galileo nims data acquired late in the mission all of these identifications are associated with small dark paterae we utilize nims data to quantify their volcanic thermal emission as 0 53 1012 w or 0 5 of io s total heat flow in addition we refine our previous estimates of the thermal emission from 47 hot spots and highlight several hot spots within the amirani flow field small dark paterae still out number faint close to the limit of detection hot spots identified in high spatial resolution multi wavelength nims data in particular we point out 24 small dark paterae that were scanned by nims at resolutions down to 17 km pixel but had no detectable volcanic thermal emission all dark paterae are expected to have some volcanic thermal emission but the small size and finite number of detectable faint sources limit their contribution to the total heat flow on io compared to small paterae small dark flows are more numerous but must have significantly lower surface temperatures finally we update and summarize our results for the global heat flow on io due to 242 recently active volcanic features including other dark paterae as well as large dark flows the volcanic thermal emission from known hot spots undetected scanned dark patera and outbursts can account for only 56 2 1012 w or 54 of io s total heat flow approximately 49 1012 w or 46 of io s heat flow remains an enigma

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 1 geometric and kinematic aspects a new deformation apparatus has been used to model the internal kinematics of salt diapirs composite natural samples consisting of a single layer of anhydrite embedded in halite matrix were constrictionally deformed at temperature t 345 c strain rate 10 7 s 1 maximum viscosity 2 1013 pa s and maximum finite strain ex 122 the anhydrite layer oriented parallel to the major stretching axis x was deformed by fracturing whereas halite behaved viscously at advanced state of constriction ex 90 a strong increase in strain hardening of halite led to a transient tension fracture that healed up and was shortened by folding during the final phase of viscous deformation tiny prismatic anhydrite inclusions disseminated inside the halite matrix were reoriented during constriction resulting in a linear grain shape fabric 3d images of the anhydrite layer based on computer tomography revealed rare kink folds with axes subparallel to x and boudins which result from tension fracture with increasing layer thickness hi the width of boudins wa increases linearly wa 0 3 1 3 hi the normalized width of boudins wd wa hi is almost constant at 1 5 1 0 these geometrical parameters can be used to reveal fracture boudinage under bulk constriction the oblique orientation of most of the boudins with respect to the principal strain axes results from folding of the boudins by a second generation of folds the latter with axes subperpendicular to the layer

active volcanism on io as seen by galileo ssi abstract active volcanism on io has been monitored during the nominal galileo satellite tour from mid 1996 through late 1997 the solid state imaging ssi experiment was able to observe many manifestations of this active volcanism including 1 changes in the color and albedo of the surface 2 active airborne plumes and 3 glowing vents seen in eclipse about 30 large scale tens of kilometers surface changes are obvious from comparison of the ssi images to those acquired by voyager in 1979 these include new pyroclastic deposits of several colors bright and dark flows and caldera floor materials there have also been significant surface changes on io during the galileo mission itself such as a new 400 km diameter dark pyroclastic deposit around pillan patera while these surface changes are impressive the number of large scale changes observed in the four months between the voyager 1 and voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive there are two reasons why this was not actually the case first it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years second it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of io s surface the plume monitoring has revealed 10 active plumes comparable to the 9 plumes observed by voyager one of these plumes was visible only in the first orbit and three became active in the later orbits only the prometheus plume has been consistently active and easy to detect observations of the pele plume have been particularly intriguing since it was detected only once by ssi despite repeated attempts but has been detected several times by the hubble space telescope at 255 nm pele s plume is much taller 460 km than during voyager 1 300 km and much fainter at visible wavelengths prometheus type plumes 50 150 km high long lived associated with high temperature hot spots may result from silicate lava flows or shallow intrusions interacting with near surface so2 a major and surprising result is that 30 of io s volcanic vents glow in the dark at the short wavelengths of ssi these are probably due to thermal emission from surfaces hotter than 700 k with most hotter than 1000 k well above the temperature of pure sulfur volcanism active silicate volcanism appears ubiquitous there are also widespread diffuse glows seen in eclipse related to the interaction of energetic particles with the atmosphere these diffuse glows are closely associated with the most active volcanic vents supporting suggestions that io s atmopshere is dominated by volcanic outgassing globally volcanic centers are rather evenly distributed however 14 of the 15 active plumes seen by voyager and or galileo are within 30 of the equator and there are concentrations of glows seen in eclipse at both the sub and antijovian points these patterns might be related to asthenospheric tidal heating or tidal stresses io will continue to be observed during the galileo europa mission which will climax with two close flybys of io in late 1999

violent silicate volcanism on io in 1996 we monitored io s volcanic thermal emission from 1 7 to 4 8 m in 1995 96 the data reveal a number of brightenings when io s thermal emission increased several fold we use a model of emission from lava flows to understand observations of two brightenings in 1996 the brightenings were caused by eruptions 3km in extent with eruptive rates of 104 106 m s 1 and with maximum lava temperatures 1400 k these events were probably lava lakes and or fire fountains

silicate volcanism on io io is currently emitting 1 1 5 w m 2 of tidal energy as a result of its volcanic activity if the lithosphere is more than 20 km thick as appears probable from the surface relief only a fraction of the tidal energy can be dissipated within the lithosphere otherwise it will become thinner the rest of the tidal energy must be dissipated below the lithosphere io is likely to be highly differentiated as a result of the volcanic activity with a low melting temperature fraction such as basalt near the surface and a high melting temperature fraction such as peridotite at depth if solidus temperatures are reached at depths shallower than the thickness of the basalt layer a partial melt zone will separate an all basalt lithosphere above from a peridotite mantle below and part of the tidal energy will be dissipated by viscous deformation within the melt zone most of the energy dissipated below the lithosphere will be transported upward through the lithosphere as silicate magma which is generated in quantities sufficient to resurface the satellite at a rate of a few tenths of a centimeter a year depending on the lithosphere thickness many of the characteristics of the ionian surface have been explained in terms of sulfur volcanism however most of the features observed can be as readily explained by silicate volcanism and silicates are more consistent with the apparent strength of the surface as implied by the relief simulations of basaltic eruptions indicate that the surface temperatures that would result from basaltic eruptions are similar to those measured by the voyager infrared interferometer spectrometer experiment the high rates of emission by the ionian hot spots imply eruption rates that are high compared with typical terrestrial eruptions an eruption rate of 4000 m3 s 1 may be required to explain loki which is currently emitting 1013 w although the near surface materials are mainly silicate they may contain several percent of volatile components rich in s na and k remobilization of these components by the ongoing silicate eruptions causes the plumes provides material to the torus and gives the satellite its characteristic reflectivity

io s loki patera modeling of three brightening events in 2013 2016 abstract loki patera is one of the most dramatically time variable volcanic features on io exhibiting episodic brightening events every 1 3 years that may produce over 15 of io s global heat flow we observed three such brightening events with adaptive optics imaging at the keck and gemini n telescopes over the course of 70 nights of observation in 2013 2016 the high cadence and multi wavelength nature of the observations provides constraints on models for activity at loki patera the matson et al 2006 model for loki patera as an overturning basaltic magma sea is adapted to fit the observations of all three events in particular we adjust the details of the overturn progression and modify the lava thermal properties to include dependencies on temperature and porosity to improve the fit to the data the preferred models find overturn front propagation velocities of 1 2 1 7 km day corresponding to resurfacing rates of 1500 2200 m2 s the time intervals of 440 540 days between successive events are roughly consistent with the 540 day period calculated by rathbun et al 2002 for events prior to 2001 the best coverage was obtained for the 2016 brightening model fits to this event require a lava bulk thermal conductivity of 0 55 0 75 w m k with the best fit obtained for a value of 0 7 w m k and an average porosity that decreases during cooling for all three events the overturn front appears to propagate around the patera in the clockwise direction opposite to what has been inferred for past brightening events there is evidence that the overturn may be more complex than a single propagating wave perhaps involving multiple simultaneous resurfacing waves as well as portions of the patera that are active even after the nominal bright phase has ended the measured intensities are anomalously low when loki patera is viewed at high emission angles suggestive of topographic shadowing due to a raised area or the edge of the depression in which the magma sea resides

tvashtar awakening detected in april 2006 with osiris at the w m keck observatory abstract we detected a volcanic outburst in io s northern hemisphere on 17 april 2006 with the osiris imaging spectrometer at keck and confirmed it was still erupting on 2 june 2006 the eruption which we name 060417a was located in tvashtar paterae 100 km southeast of the february 2000 eruption the observed temperature was 1240 4 k over a surface area of 60 5 km 2 providing a total thermal output of 7 7 0 9 10 12 w

observationally constrained modeling of sound in curved ocean internal waves examination of deep ducting and surface ducting at short range a study of 400 hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented sound propagation roughly along the crests of the waves is simulated with a three dimensional parabolic equation computational code and the results are compared to measured propagation along fixed 3 and 6 km source receiver paths the measurements were made on the shelf of the south china sea northeast of tung sha island construction of the time varying three dimensional sound speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data computed three dimensional propagation results compare well with field observations the simulations allow identification of time dependent sound forward scattering and ducting processes within the curved internal gravity waves strong acoustic intensity enhancement was observed during passage of high amplitude nonlinear waves over the source receiver paths and is replicated in the model the waves were typical of the region 35 m vertical displacement two types of ducting are found in the model which occur asynchronously one type is three dimensional modal trapping in deep ducts within the wave crests shallow thermocline zones the second type is surface ducting within the wave troughs deep thermocline zones

three decades of loki patera observations abstract we present observations of io s loki patera taken with the 10 m keck telescopes between 1998 and 2016 adding these data to those published by rathbun and spencer 2006 and the gemini data of de kleer and de pater 2016a 2017 results in a database of 3 5 3 8 m emission from loki patera over almost 3 decades data presented here contain adaptive optics ao observations of io s sunlit hemisphere at wavelengths between 1 6 and 5 m ao observations of io in eclipse at 2 5 m and non ao observations of io in eclipse at 1 6 12 m the non ao data were taken in september of 1999 during the early phase of a brightening event that was documented by howell et al 2001 dual component io flow model ifm fits to our 1999 observations show a mostly cool lava crust over almost the entire patera floor with a relatively small hotter component making up less than 1 of the total area consistent with previous observations the 30 year timeline of loki patera revealed that after an apparent cessation of or change in brightening events in 2002 loki patera became active again in 2009 the more recent activity may have a slightly shorter periodicity than observed by rathbun et al 2002 and the direction of flow propagation appears to have reversed since 2009 the flow direction is in the clockwise direction starting in the north or north east corner and propagating along the patera towards the south west during the galileo era the propagation was in the counter clockwise direction starting in the south west and propagating towards the east both the 30 year timeline and the 1 6 12 m spectrum that was obtained during the brightening event in 1999 agree well with matson et al s 2006 overturning lava lake model as modified by de kleer and de pater 2017

speckle imaging of volcanic hotspots on io with the keck telescope abstract using speckle imaging techniques on the 10 m w m keck i telescope we observed near infrared emission at 2 2 m from volcanic hotspots on io in july august 1998 using several hundreds of short exposure images we reconstructed diffraction limited images of io on each of three nights we measured the positions of individual hotspots to 0 004 or better corresponding to a relative positional error of 20 km on io s surface the sensitivity of normal ground based images of io is limited by confusion between overlapping sources by resolving these multiple points we detected up to 17 distinct hotspots the largest number ever seen in a single image during the month long span of our 1998 observations several events occurred loki was at the end of a long brightening and we observed it to fade in flux by a factor of 2 8 over the course of one month at the 3 sigma level we see evidence that loki s position shifts by 100 km this suggests that the brightening may not have been located at the primary loki emission center but at a different source within the loki caldera we also see a bright transient source near loki among many other sources we detect a dim source on the limb of io at the latitude of pele this source is consistent with 2 7 of the thermal emission from the pele volcano complex being scattered by the pele plume which would be the first detection of a plume through scattered infrared hotspot emission

io heat flow from dark paterae abstract dark paterae on the jovian satellite io are evidence of recent volcanic activity some paterae appear to be entirely filled with dark volcanic material while others have only partially darkened floors dark paterae have area and heat flow longitudinal distributions that are bimodal as well as anti correlated with the longitudinal distribution of mountains on io at a global scale as part of our study of io s total heat flow we have examined the darkest paterae and quantified their thermal emission in order to assess their contribution this is the first time that the areas of the dark material in these paterae have been measured with such precision and correlated with their thermal emission dark paterae yield a significantly larger contribution to io s heat flow than dark volcanic fields dark paterae including loki patera yield at least 4 10 13 w or 40 of io s total heat flow in comparison dark flow fields yield 10 13 w or 10 of io s total heat flow of the total heat loss from dark paterae loki patera alone yields 10 13 w or 10 of io s total thermal emission

a coupled mode solution for acoustic propagation in a waveguide with stepwise depth variations of a penetrable bottom a coupled mode solution is formulated for the problem of acoustic propagation in a cylindrically symmetric ocean divided in range into a finite number of adjoining pekeris waveguides of differing water depths attenuation is included in the bottom and the problem is discretized by assigning a pressure release boundary condition at a depth which is sufficiently far removed to prevent significant energy from returning to the water this formulation includes backscatter from the depth variations of the water column and full coupling between a finite number of modes propagating in the water column and in the bottom numerical results based on an implementation of this solution are presented

keck observations of eruptions on io in 2003 2005 abstract we report observations of four energetic volcanic eruptions on io at tupan patera on ut 8 march 2003 tung yo patera on ut 28 may 2004 sui jen patera on ut 30 may 2004 and south of babbar patera on ut 31 may 2005 the tung yo sui jen and south of babbar paterae eruptions are in locations where no activity had been seen before our observations were obtained at near infrared wavelengths 1 2 4 7 m with the 10 m keck telescope equipped with adaptive optics we report single and two temperature blackbody fits as well as single component and dual component io flow model ifm fits davies 1996 icarus 124 45 61 to all four eruptions where applicable we use 2 m and 5 m radiant fluxes the 2 5 m radiant flux ratio and radiant flux density of each thermal source to constrain the likely style of volcanic eruption all eruptions are characterized by a high temperature ifm component ranging from 1475 to 900 k from a relatively small area

io s thermal emission from the galileo photopolarimeter radiometer galileo s photopolarimeter radiometer instrument mapped io s thermal emission during the i24 i25 and i27 flybys with a spatial resolution of 2 2 to 300 kilometers mapping of loki in i24 shows uniform temperatures for most of loki patera and high temperatures in the southwest corner probably resulting from an eruption that began 1 month before the observation most of loki patera was resurfaced before i27 pele s caldera floor has a low temperature of 160 kelvin whereas flows at pillan and zamama have temperatures of up to 200 kelvin global maps of nighttime temperatures provide a means for estimating global heat flow