three dimensional simulation of gas and dust in io s pele plume abstract io s giant pele plume rises high above the moon s surface and produces a complex deposition pattern we use the direct simulation monte carlo dsmc method to model the flow of so2 gas and silicate ash from the surface of the lava lake into the umbrella shaped canopy of the plume and eventually onto the surface where the flow leaves black butterfly wings surrounded by a large red ring we show how the geometry of the lava lake from which the gas is emitted is responsible for significant asymmetry in the plume and for the shape of the red deposition ring by way of complicated gas dynamic interactions between parts of the gas flow arising from different areas in the lava lake we develop a model for gas flow in the immediate vicinity of the lava lake and use it to show that the behavior of ash particles of less than about 2 m in diameter in the plume is insensitive to the details of how they are introduced into the flow because they are coupled to the gas at low altitudes we simulate dust particles in the plume to show how particle size determines the distance from the lava lake at which particles deposit on the surface and we use this dependence to find a size distribution of black dust particles in the plume that provides the best explanation for the observed black fans to the east and west of the lava lake this best fit particle size distribution suggests that there may be two distinct mechanisms of black dust creation at pele and when two log normal distributions are fit to our results we obtain a mean particle diameter of 88 nm we also propose a mechanism by which the condensible plume gas might overlay black dust in areas where black coloration is not observed and compare this to the observed overlaying of pillanian dust by pele s red ring

ries crater and suevite revisited observations and modeling part ii modeling we present the results of numerical modeling of the formation of the ries crater utilizing the two hydrocodes sova and isale these standard models allow us to reproduce crater shape size and morphology and composition and extension of the continuous ejecta blanket some of these results cannot however be readily reconciled with observations the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks containing very little material in comparison with the ejecta curtain at the end of the modification stage the crater floor is covered by a thick layer of impact melt with a total volume of 6 11 km3 the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters ejecta from all stratigraphic units of the target are transported ballistically no separation of sedimentary and crystalline rocks as observed between suevites and bunte breccia at ries is noted we also present numerical results quantifying the existing geological hypotheses of ries ejecta emplacement from an impact plume by melt flow or by a pyroclastic density current the results show that none of these mechanisms is consistent with physical constraints and or observations finally we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile rich sedimentary rocks

researching the earth and a few of its neighbors during my career our knowledge of erupting geysers and volcanoes in the solar system has exploded in this prefatory i tell how i became fascinated with high speed processes through studying meteorite impact dynamics and then how my initial idea of studying old faithful geyser as a volcanic analog led me to work not only on the dynamics of eruption of mount st helens in 1980 but also on geysers erupting on io a fiery satellite of jupiter triton a frigid satellite of neptune and enceladus an active satellite of saturn unforeseeably the study of these events also led to work on mineral thermodynamics and the hydraulics and geomorphic evolution of rapids in the grand canyon this is a narrative not a formal review article but the reader can find references in the related resources section to explore topics in more detail

the canyon diablo impact event 2 projectile fate and target melting upon impact abstract despite its centennial exploration history there are still unresolved questions about meteor crater the first recognized impact crater on earth this theoretical study addresses some of these questions by comparing model results with field and laboratory studies of meteor crater our results indicate that meteor crater was formed by a high velocity impact of a fragmented projectile ruling out a highly dispersed swarm as well as a very low impact velocity projectile fragmentation caused many fragments to fall separately from the main body of the impactor making up the bulk of the canyon diablo meteorites most of these fragments were engulfed in the expansion plume as they approached the surface without suffering high shock compression and were redistributed randomly around the crater thus the distribution of canyon diablo meteorites is not representative of projectile trajectory as is usual for impactor fragments in smaller strewn fields at least 50 of the main impactor was ejected from the crater during crater excavation and was dispersed mostly downrange of the crater as molten particles spheroids and highly shocked solid fragments shrapnel when compared with the known distribution model results suggest an impactor from the sw overall every model case produced much higher amounts of pure projectile material than observed the projectile target mixing was not considered in the models however this process could be the main sink of projectile melt as all analyzed melt particles have high concentrations of projectile material the fate of the solid projectile fragments is still not completely resolved model results suggest that the depth of melting in the target can reach the coconino sandstone formation however most of the ejected melt originates from 30 40 m depth and thus is limited to moenkopi and upper kaibab material some melt remains in the target based on the estimated volume of the breccia lens at meteor crater our models suggest at most a 2 content of melt in the breccia finally a high water table at the time of impact could have aided strong dispersion of target and projectile melt

infrasonic crackle and supersonic jet noise from the eruption of nabro volcano eritrea the lowermost portion of an explosive volcanic eruption column is considered a momentum driven jet understanding volcanic jets is critical for determining eruption column dynamics and mitigating volcanic hazards however volcanic jets are inherently difficult to observe due to their violence and opacity infrasound from the 2011 eruption of nabro volcano eritrea has waveform features highly similar to the crackle phenomenon uniquely produced by man made supersonic jet engines and rockets and is characterized by repeated asymmetric compressions followed by weaker gradual rarefactions this infrasonic crackle indicates that infrasound source mechanisms in sustained volcanic eruptions are strikingly similar to jet noise sources from heated supersonic jet engines and rockets suggesting that volcanologists can utilize the modeling and physical understandings of man made jets to understand volcanic jets the unique distinctive infrasonic crackle from nabro highlights the use of infrasound to remotely detect and characterize hazardous eruptions and its potential to determine volcanic jet parameters key points nabro volcano produced sound similar to supersonic jet engines and rockets volcanic and man made jets have similar sound source mechanisms infrasound can remotely detect and characterize volcanic eruptions and jets 2013 american geophysical union all rights reserved

eruptions at lone star geyser yellowstone national park usa 1 energetics and eruption dynamics 1 geysers provide a natural laboratory to study multiphase eruptive processes we present results from a 4 day experiment at lone star geyser in yellowstone national park usa we simultaneously measured water discharge acoustic emissions infrared intensity and visible and infrared video to quantify the energetics and dynamics of eruptions occurring approximately every 3 h we define four phases in the eruption cycle 1 a 28 3 min phase with liquid and steam fountaining with maximum jet velocities of 16 28 m s 1 steam mass fraction of less than 0 01 intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction 2 a 26 8 min posteruption relaxation phase with no discharge from the vent infrared ir and acoustic power oscillations gliding between 30 and 40 s 3 a 59 13 min recharge period during which the geyser is quiescent and progressively refills and 4 a 69 14 min preplay period characterized by a series of 5 10 min long pulses of steam small volumes of liquid water discharge and 50

the origin of harmonic tremor at old faithful geyser volcanic tremor the seismic signal which is often associated with eruptions is among the least understood phenomena in seismology large variations in the physical properties of volcanic rocks and fluids along with the complex geological structure make it difficult to obtain reliable source models old faithful geyser yellowstone national park was chosen as a laboratory for studying fluid flow induced seismicity the geyser s cyclic behavior on an hourly time scale and its accessibility make it suitable for a detailed study of seismic behavior between eruptions simultaneously with underwater pressure measurements inside the geyser we observe that sharp pressure pulses inside the water column attributed to steam bubble collapse are followed by distinct seismic events with a sharp onset and a harmonic horizontal motion whose frequency varies spatially but not temporally a superposition of these events creates the appearance of continuous harmonic tremor since the pressure in the water column exhibits no sign of resonance the harmonic motion must be caused by elastic waves reverberating in the solid medium a near surface soft layer is demonstrated to be a possible elastic model the harmonic tremor observed at old faithful seems analogous to some examples of shallow volcanic tremor

the decompression of volcanic jets in a crater during explosive volcanic eruptions during explosive volcanic eruptions fragmented silicic magma and volatiles exit the vent with pressures typically in the range 10 100 atm and at the speed of sound of the mixture we show that for magmatic volatile contents no in the range 0 03 no 0 06 this has the approximate value 0 95 0 05 nort 12 where r is the gas constant and t is the eruption temperature this speed is nearly independent of the vent pressure and vent radius by assuming there is negligible mixing with the air we have modelled the decompression of such jets following eruption from the vent for free decompression into the atmosphere the velocity of the decompressed jet has the approximate value 1 85 0 05 nort 12 this is nearly independent of the eruption rate for decompression into a crater the process is more complex at low eruption rates with low vent pressure the material becomes underpressured as it rises in the crater a shock then forms in the crater this recompresses the magma volatile mixture which then issues from the crater as a relatively slow subsonic jet at atmospheric pressure as the eruption rate increases such shocks move towards the top of the crater and ultimately cannot form in the crater instead the material issues from the crater as a high speed supersonic jet the upward thrust provided by the crater walls on this high pressure jet then increases the upward velocity above that of a freely decompressing jet the presence of a crater may therfore cause collapse in relatively small eruptions whereas it may promote formation of buoyant eruption columns at higher eruption rates if a crater grows through erosion during an eruption column collapse will typically ensue even if the mass flux remains steady

water velocity and the nature of critical flow in large rapids on the colorado river utah 1 rapids are an integral part of bedrock controlled rivers influencing aquatic ecology geomorphology and recreational value flow measurements in rapids and high gradient rivers are uncommon because of technical difficulties associated with positioning and operating sufficiently robust instruments in the current study detailed velocity water surface and bathymetric data were collected within rapids on the colorado river in eastern utah with the water surface survey it was found that shoreline based water surface surveys may misrepresent the water surface slope along the centerline of a rapid flow velocities were measured with an adcp and an electronic pitot static tube integrating multiple measurements the adcp returned velocity data from the entire water column even in sections of high water velocity the maximum mean velocity measured with the adcp was 3 7 m s the pitot static tube while capable of only point measurements quantified velocity 0 39 m below the surface the maximum mean velocity measured with the pitot tube was 5 2 m s with instantaneous velocities up to 6 5 m s analysis of the data showed that flow was subcritical throughout all measured rapids with a maximum measured froude number of 0 7 in the largest measured rapids froude numbers were highest at the entrance of a given rapid then decreased below the first breaking waves in the absence of detailed bathymetric and velocity data the froude number in the fastest flowing section of a rapid was estimated from near surface velocity and depth soundings alone

cratering on mars with almost no atmosphere or volatiles pangboche crater pangboche crater 17 2 n 226 7 e 10 4 km dia lies close to the summit of olympus mons volcano mars at an elevation of 20 9 km above the datum given a scale height of 11 1 km for the atmosphere this relatively large fresh crater most likely formed at an atmospheric pressure 1 mbar in essentially volatile free young lava flows detailed analysis of pangboche crater from high resolution imaging science experiment hirise and context camera ctx images reveals that volatile related features e g fluidized ejecta layers and pitted floor material are absent in contrast abundant impact melt occurs on the floor inner walls and rim of the crater and there is an extensive field of secondary craters that extend up to approximately 45 km from the rim crest all of these attributes argue that it was the absence of volatiles in the target rocks at the time of crater formation rather than the thin atmosphere which had a controlling influence on crater morphology digital elevation data derived from the ctx images reveal that pangboche crater has a depth of about 954 m depth diameter approximately 0 092 and that uplifted target rocks comprise about 58 of the relief of the 180 m high north rim as the target material comprised a sequence of layered lava flows pangboche crater may well represent the best crater on mars for direct comparison with craters formed on the moon permitting variations in gravitational effects to be investigated or on mercury allowing the role of the atmosphere to be studied

a clathrate reservoir hypothesis for enceladus south polar plume we hypothesize that active tectonic processes in the south polar terrain of enceladus the 500 kilometer diameter moon of saturn are creating fractures that cause degassing of a clathrate reservoir to produce the plume documented by the instruments on the cassini spacecraft advection of gas and ice transports energy supplied at depth as latent heat of clathrate decomposition to shallower levels where it reappears as latent heat of condensation of ice the plume itself which has a discharge rate comparable to old faithful geyser in yellowstone national park probably represents small leaks from this massive advective system

volcan reventador s unusual umbrella 1 photographs of a volcanic column in a recent eruption of reventador show a prominently scalloped umbrella that is unlike any umbrella previously documented on a volcanic column we propose that the scallops in this umbrella are the result of a turbulent rayleigh taylor rt instability a type of fluid instability with no precedents in volcanology negative buoyancy drives this instability and we ascribe the unusual negative buoyancy of the reventador umbrella to the fact that the reventador column fed on a cool co ignimbrite cloud from the wavelength of the scallops we estimate a value for the eddy viscosity of the umbrella d 4 000 m2 s the first such value to be inferred directly from an observation in the field collapse of the umbrella back to the ground could result in a previously unrecognized hazardous flow we hope this work will elicit new reports on scalloped umbrellas and further study of the characteristics and evolution of such umbrellas

emplacement of cretaceous tertiary boundary shocked quartz from chicxulub crater observations on shocked quartz in cretaceous tertiary k t boundary sediments compellingly tied to chicxulub crater raise three problems first in north america shocked quartz occurs above the main k t ejecta layer second shocked quartz is more abundant west than east of chicxulub third shocked quartz reached distances requiring initial velocities up to 8 kilometers per second corresponding to shock pressures that would produce melt not the moderate pressure shock lamellae observed shock devolatilization and the expansion of carbon dioxide and water from impacted wet carbonate producing a warm accelerating fireball after the initial hot fireball of silicate vapor may explain all three problems

estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes apparently benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction as happened recently at mount unzen in japan1 two sources have been proposed for the energy that propels such pelean or merapi type2 pyroclastic flows gravitational col lapse supplemented by heating and expansion of air and sudden expansion of pressurized gases from inside the lava flow if gravity controls the energy transfer then areas likely to be affected can be predicted on the basis of topography3 and the resulting deposits will bear a simple relationship to the part of the lava flow from which they issued but if gas pressure adds a significant contribution hazard assessment becomes more difficult because gas decompression adds velocities beyond those acquired by gravitational forces putting much larger areas at risk and forming pyroclastic deposits that are much more difficult to relate to their source here we estimate the initial velocities of pyroclastic flows generated by dome disintegration for a range of lava compositions and volatile contents and offer a conceptual framework for correlating the dynamics of dome front collapse with the resulting sediment record our results indicate that explosive decompression at distal portions of domes can cause velocities comparable to gravitational collapse especially in cases where volatiles become locally concentrated above equilibrium values

blast dynamics at mount st helens on 18 may 1980 at 8 32 a m on 18 may 1980 failure of the upper part of the north slope of mount st helens triggered a lateral eruption the blast that devastated the conifer forests in a sector covering 500 km2 north of the volcano i present here a steady flow model for the blast dynamics and propose that through much of the devastated area the blast was a supersonic flow of a complex multiphase solid liquid vapour mixture the shape of the blast zone pressure temperature velocity mach number and density distributions within the flow positions of weak and strong internal shocks and mass flux energy flux and total energy are calculated the shape of blast zone was determined by the initial areal expansion from the reservoir by internal expansion and compression waves including shocks and by the density of the expanding mixture the pressure within the flow dropped rapidly away from the source of the blast until at a distance of 11 km the flow became underpressured relative to the surrounding atmosphere weak shocks within the flow subparallel to the east and west margins coalesced at about this distance into a strong mach disk shock across which the flow velocities would have dropped from supersonic to subsonic as the pressure rose back towards ambient the positions of the shocks may be reflected in differences in the patterns of felled trees at the limits of the devastated area the temperature had dropped only 20 from the reservoir temperature because the entrained solids thermally buffered the flow the dynamic and thermodynamic effects of the admixture of the surrounding atmosphere and the uprooted forest and soils into the flow are not considered the density of the flow decreased with distance until at the limits of the blast zone 20 25 km from the volcano the density became comparable with that of the surrounding dirty atmosphere and the flow became buoyant and ramped up into the atmosphere according to the model the mass flux per unit area at the source was 0 6 104 g s 1 cm 2 and the energy flux per unit area was 2 5 mw cm 2 from the measured total ejected mass 0 25 1015 g the total energy released during the eruption was 1024 erg or 24 megatons the model triggering of the eruption and the transition from unsteady to steady flow and applications to eyewitness observations and atmospheric effects are discussed in ref 1

comparison of petrofabrics with composite magnetic fabrics of s c mylonite in paramagnetic granite abstract an anisotropy of magnetic susceptibility ams analysis was conducted for a typical s c mylonite in a small scale ductile shear zone derived from late cretaceous magnetite free granite in the ryoke belt teshima island southwest japan in such mylonites paramagnetic minerals such as biotite and hornblende which define foliations are assumed to control the ams accordingly we attempted to measure the orientations of both minerals to correlate the s c c fabric to the ams using techniques of microscopic and back scattered electron bse image analyses a measured magnetic fabric of the s c mylonite that is expressed by a kmin normal plane kmax kint plane approximated s foliation kmax orientation coincided well with the orientations of mean resultant vectors for long axes of biotite and minor hornblende whereas kmax did not coincide well with those of the mean resultant vectors for long axes of the brighter domain aggregates of biotite and minor hornblende from the binary bse image these results show that the magnetic fabric fairly reflects the shape preferred orientation of individual grains of paramagnetic monoclinic minerals especially biotite which forms the s c c fabric

stress and mass changes at a wet volcano example during the 2011 2012 volcanic unrest at kawah ijen volcano indonesia since 2010 kawah ijen volcano has been equipped with seismometers and its extremely acid volcanic lake has been monitored using temperature and leveling sensors providing unprecedented time resolution of multiparametric data for an acidic volcanic lake the nature of stress and mass changes of the volcano is studied by combining seismic analyses and volcanic lake measurements that were made during the strongest unrest ever recorded by the seismic network at kawah ijen the distal vt earthquake swarm that occurred in may 2011 was the precursor of volcanic unrest in october 2011 that caused an increase in shallow earthquakes the proximal vt earthquakes opened pathways for fluids to ascend by increasing the permeability of the rock matrix the following months were characterized by two periods of strong heat and mass discharge into the lake and by the initiation of monochromatic tremor mt activity when steam gases interacted with shallow portions of the aquifer significant seismic velocity variations concurrent with water level rises in which water contained a large amount of steam gas were associated with the crises that caused an although the unrest did not affect the shallow hydrothermal system at a large scale whereas shallow vt earthquakes likely reflect a magmatic intrusion mt and relative seismic velocity changes are clearly associated with shallow hydrothermal processes these results will facilitate the forecast of future crises

the plumbing of old faithful geyser revealed by hydrothermal tremor 1 old faithful geyser in yellowstone national park usa has attracted numerous scientific investigations for over two centuries to better understand its geological structure the physics of its eruptions and the controls of its intermittency using data acquired with a seismic array in 1992 we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser the location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface on the sw side of the vent and connected to the conduit this reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption

air pressure waves from mount st helens eruptions weather station barograph records as well as infrasonic recordings of the pressure wave from the mount st helens eruption of may 18 1980 have been used to estimate an equivalent explosion airblast yield for this event pressure amplitude versus distance patterns in various directions compared with patterns from other large explosions such as atmospheric nuclear tests the krakatoa eruption and the tunguska comet impact indicate that the wave came from an explosion equivalent of a few megatons of tnt the extent of tree blowdown is considerably greater than could be expected from such an explosion and the observed forest damage is attributed to outflow of volcanic material the pressure time signature obtained at toledo washington showed a long 13 min duration negative phase as well as a second hour long compression phase both probably caused by ejacta dynamics rather than standard explosion wave phenomenology the peculiar audibility pattern with the blast being heard only at ranges beyond about 100 km is explicable by finite amplitude propagation effects near the source compression was slow taking more than a second but probably less than 5 s so that it went unnoticed by human ears and susceptible buildings were not damaged there was no damage asmore toledo 54 km where the recorded amplitude would have broken windows with a fast compression an explanation is that wave emissions at high elevation angles traveled to the upper stratosphere where low ambient air pressures caused this energetic pressure oscillation to form a shock wave with rapid nearly instantaneous compression atmospheric refraction then returned part of this wave to ground level at long ranges where the fast compressions were clearly audible copyright american geophysical union 1987 less

impact and volcanism a momentum scaling law for erosion the controversy that raged through the 1950s 1970s over similarities and differences between meteorite impact and volcanic processes is revisited in this paper we propose that there are quantitative similarities in erosion caused by high speed ejecta produced by either impacts or volcanic processes field and petrographic data from the manicouagan impact crater canada are used to demonstrate that during the emplacement of the impact melt sheet erosion occurred at a rate of 2562 kg m 2 s 1 field data for the mount st helens lateral blast of may 18 1980 suggest an erosion rate of 2 kg m 2 s 1 and field data for a small pyroclastic flow on august 7 1980 suggest an erosion rate of 14 kg m s 1 it is proposed that these three rates were determined dominantly by the momentum of the ejecta and a quantitative formulation based on lofting theory is given a new application of the monte carlo approach to analysis provides minimum most likely and maximum estimates for both the field and the theoretical analyses the substantial erosion that occurs by fast moving flows results in mixing of stratigraphic components over large distances and to very fine scales

mount st helens eruption of 18 may 1980 air waves and explosive yield strong atmospheric acoustic gravity waves were recorded by sensitive microbarographs and seismographs at large distances from the mount st helens eruption of 18 may 1980 wave signatures were similar to those of waves from large nuclear explosions independent theoretical and empirical analyses indicate that the explosive yield of the eruption was approximately 35 megatons

ice melt rates in liquid filled cavities during explosive subglacial eruptions subglacial eruptions are often associated with rapid penetration of overlying ice and release of large flow rates of water as jokulhlaups observations of recent subglacial eruptions indicate rapid syn eruptive ice melting within liquid filled subglacial cavities but quantitative descriptions of possible heat transfer processes need to be developed calculations of heat flux from the ice cavity fluid to the melting ice surface indicate that up to 0 6 mw m 2 may be obtained for fluids undergoing single phase free convection similar to minimum estimates of heat flux inferred from observations of recent eruptions our model of boiling two phase free convection in subglacial cavities indicates that much greater heat fluxes in the range 3 5 mw m 2 can be obtained in the vent region of the cavity and may be increased further by momentum transfer from the eruption jet rapid magma water heat transfer from fragmented magma is needed to sustain these heat fluxes similar heat fluxes are anticipated for forced convection of subcooled cavity water induced by momentum transfer from an eruption jet these heat fluxes approach those required to explain jokulhlaup flow rates and rapid ice penetration rates by melting in some but not all recent eruptions

residence time of buoyant objects in drowning machines hydraulic jumps are a common feature of rivers and waterways where they can be found close to spillways weirs rocky ledges and boulders people adrift upstream of a hydraulic jump are liable to become trapped in the turbulent roller of the hydraulic jump for this reason hydraulic jumps have been termed drowning machines and are recognized as a public hazard we use experiments and theory to show that on average a buoyant object spends a time p trapped in a jump where is the period of a harmonic process inherent in the jump and p is the probability that the object will escape in any time interval the probability p is governed by the statistical theory of extreme values and depends primarily on the ratio between the density of the object and the density of the fluid we use our results to draw conclusions that might prove to be useful to public safety agencies intent on carrying out tests in drowning machines our results can also be used to predict the amount of flotsam that accumulates at the toe of a hydraulic jump

prometheus io s wandering plume unlike any volcanic behavior ever observed on earth the plume from prometheus on io has wandered 75 to 95 kilometers west over the last 20 years since it was first discovered by voyager and more recently observed by galileo despite the source motion the geometric and optical properties of the plume have remained constant we propose that this can be explained by vaporization of a sulfur dioxide and or sulfur snowfield over which a lava flow is moving eruption of a boundary layer slurry through a rootless conduit with sonic conditions at the intake of the melted snow can account for the constancy of plume properties

ground coupled acoustic airwaves from mount st helens provide constraints on the may 18 1980 eruption abstract the may 18 1980 mount st helens eruption perturbed the atmosphere and generated atmosphere to ground coupled airwaves which were recorded on at least 35 seismometers operated by the pacific northwest seismograph network pnsn from 102 distinct travel time picks we identify coherent airwaves crossing washington state primarily to the north and east of the volcano the travel time curves provide evidence for both stratospheric refractions at 200 to 300 km from the volcano as well as probable thermospheric refractions at 100 to 350 km the very few first hand reports of audible volcano sounds within about 80 km of the volcano coincide with a general absence of ground coupled acoustic arrivals registered within about 100 km and are attributed to upward refraction of sound waves from the coherent refracted airwave arrivals we identify at least four distinct sources which we infer to originate 10 s 114 s 180 s and 319 s after the onset of an 8 32 11 pdt landslide the first of these sources is attributed to resultant depressurization and explosion of the cryptodome most of the subsequent arrivals also appear to be coincident with a source located at or near the presumed volcanic conduit but at least one of the later arrivals suggests an epicenter displaced about 9 km to the northwest of the vent this dislocation is compatible with the direction of the sector collapse and lateral blast we speculate that this concussion corresponds to a northern explosion event associated with hot cryptodome entering the toutle river valley

the mlindi ring structure an example of an ultrapotassic pyroxenite to syenite differentiated complex the mlindi ring complex in southern malawi dated at 495 ma is intrusive in the proterozoic migmatite basement composed mainly of hornblende and biotite bearing paragneiss and dolomitic marble three main lithologic facies have been distinguished 1 syenite which crops out in the outer part of the complex as an oval shaped ring dike 7 km 9 km and as a rim of massive bodies cutting the mafic rocks of the central part 2 two types of diopside biotite gabbro syenogabbro and gabbronorite and 3 a banded phlogopite pyroxenite cumulate intruded by the diopside biotite gabbro

an examination of froude supercritical flows and cyclic steps on a subaqueous lacustrine delta lake chelan washington u s a density driven submarine flows including turbidity currents play an important role in the transfer of sediment into deep water these bottom hugging flows often produce flow transverse bedforms along their path a sedimentological and geophysical survey of the stehekin river delta in lake chelan washington reveals a downslope elongate field of bedforms on the delta foreset associated with hyperpycnal discharges of the stehekin river an analysis of the bedform morphologies delta geometry and density contrast between lake and river water suggests that these hyperpycnal flows are froude supercritical the bedforms are likely cyclic steps flow transverse bedforms that are bounded by stable hydraulic jumps between alternating subcritical and supercritical flow regimes the ability to examine the three dimensional bed configuration produced by natural density driven flows adds valuable information to the body of experimental work focused on the behavior of cyclic steps in flumes

the replacement of plagioclase feldspars by albite observations from hydrothermal experiments oligoclase and labradorite crystals have been experimentally replaced by albite in an aqueous sodium silicate solution at 600 c and 2 kbars the replacement is pseudomorphic and is characterised by a sharp chemical interface which progresses through the feldspar while preserving the crystallographic orientation reaction rims of albite up to 50 m thick can be readily achieved within 14 days re equilibration of plagioclase in an 18o enriched sodium and silica bearing solution results in oxygen isotope redistribution within the feldspar framework structure the observed characteristics of the reaction products are similar to naturally albitised plagioclase and are indicative of an interface coupled dissolution reprecipitation mechanism chemical analyses demonstrate that the albitisation is accompanied by the mobilisation of major minor and trace elements also including elements such as al and ti which are commonly regarded as immobile during hydrothermal alteration the results contribute to developing our understanding of the close association between large scale albitisation and secondary ore mineralisation which is common in nature

io in the near infrared near infrared mapping spectrometer nims results from the galileo flybys in 1999 and 2000 galileo s near infrared mapping spectrometer nims observed io during the spacecraft s three flybys in october 1999 november 1999 and february 2000 the observations which are summarized here were used to map the detailed thermal structure of active volcanic regions and the surface distribution of so2 and to investigate the origin of a yet unidentified compound showing an absorption feature at 1 m we present a summary of the observations and results focusing on the distribution of thermal emission and of so2 deposits we find high eruption temperatures consistent with ultramafic volcanism at pele such temperatures may be present at other hot spots but the hottest areas may be too small for those temperatures to be detected at the spatial resolution of our observations loki is the site of frequent eruptions and the low thermal emission may represent lavas cooling on the caldera s surface or the cooling crust of a lava lake high resolution spectral observations of emakong caldera show thermal emission and so2 within the same pixels implying that patches of so2 frost and patches of cooling lavas or sulfur flows are present within a few kilometers from one another thermal maps of prometheus and amirani show that these two hot spots are characterized by long lava flows the thermal profiles of flows at both locations are consistent with insulated flows with the amirani flow field having more breakouts of fresh lava along its length prometheus and amirani each show a white ring at visible wavelengths while so2 distribution maps show that the highest concentration of so2 in both ring deposits lies outside the white portion visible measurements at high phase angles show that the white deposit around prometheus extends into the so2 ring this suggests that the deposits are thin and that compositional or grain size variations may occur in the radial direction so2 mapping of the chaac region shows that the interior of a caldera adjacent to chaac has almost pure so2 the deposit appears to be topographically controlled suggesting a possible origin by liquid flow