post eruption erosion and deposition in the 1980 crater of mount st helens washington determined from digital maps the crater of mount st helens shows one of the world s highest known rates of mass wasting on many summer days rockfall is almost continuous and many large rock and dirty snow avalanches have travelled several kilometres from their sources on the crater walls since formation of the crater on 18 may 1980 talus cones exceeding 100 m in thickness have formed at the base of the unstable 600 m high crater walls to estimate rates of erosion and deposition a series of digitized topographic maps made from aerial photographs taken of the crater in 1980 1981 1983 1986 and 1988 were analysed using a geographic information system between 1980 and 1988 30 106 m3 of rock were eroded from the crater wall representing a mean retreat rate of 2 1 m yr 1 to account for the volume increase that occurs when bedrock is transformed into scree this volume is multiplied by 4 3 this provides an estimate of the rock debris volume supplied to the crater floor of 40 106 m3 the actual volume of deposits that accumulated during this 8 year period however is 68 106 m3 the difference of 28 106 m3 is presumably the volume of snow intercalated between insulating layers of rock debris similar calculations for each of four time intervals between 1980 and 1988 suggest that wall erosion and thus talus accumulation rates are declining but that rates will probably remain high for decades to come

ground penetrating radar simulation in engineering and archaeology forward modeling of ground penetration radar is developed using exact ray tracing techniques structural boundaries for a ground model are incorporated via a discrete grid with interfaces described by splines polynomials and in the case of special structures such as circular objects the boundaries are given in terms of their functional formula in the synthetic radargram method the waveform contributions of many different wave types are computed using a finely digitized antenna directional response function the radar crosssection of buried targets and the effective area of the receiving antenna can be statistically modeled attenuation along the raypaths is also monitored the forward models are used 1 as a learning tool to avoid pitfalls in radargram interpretation 2 to understand radar signatures measured across various engineering structures and 3 to predict the response of cultural structures buried beneath important archaeological sites in japan

a young multilayered terrane of the northern mare imbrium revealed by chang e 3 mission china s chang e 3 ce 3 spacecraft touched down on the northern mare imbrium of the lunar nearside 340 49 e 44 12 n a region not directly sampled before we report preliminary results with data from the ce 3 lander descent camera and from the yutu rover s camera and penetrating radar after the landing at a young 450 meter crater rim the yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders the boulder contains a substantial amount of crystals which are most likely plagioclase and or other mafic silicate mineral aggregates similar to terrestrial dolerite the lunar penetrating radar detection and integrated geological interpretation have identified more than nine subsurface layers suggesting that this region has experienced complex geological processes since the imbrian and is compositionally distinct from the apollo and luna landing sites

source parameters and time dependent slip distributions of slow slip events on the cascadia subduction zone from 1998 to 2008 1 we invert for the time dependent slip history of slow slip events on the cascadia subduction zone using gps data from 1998 to 2008 the 16 slip transients have sufficient station coverage to solve for the slip distribution on the plate interface gps time series are inverted for fault slip using the extended network inversion filter limited station coverage south of portland 45 5 n latitude restricts our analysis to events on the northern half of the subduction zone slip is resolved at the base of the seismogenic zone and the slip distributions suggest a potential segment boundary near seattle 47 6 n that correlates roughly with geologic and tectonic boundaries events that initiate to the north and south tend to overlap at about this latitude we compile statistics on source parameters such as propagation rate recurrence interval and stress drop which can be used to constrain proposed models of the source mechanics over a 10 year period total strain release from slow slip events is nonuniform along strike with the greatest cumulative slip 27 cm centered beneath port angeles 48 1 n this slip patch also exhibits the most regular recurrence of mw 6 events relative to other locations along strike the spatial extent of the slip patch beneath port angeles correlates with the along strike bend of the cascadia subduction zone in northwestern washington suggesting that plate geometry plays an important role in controlling the along strike characteristics of slow slip

submarine hydrothermal activity along the mid kermadec arc new zealand large scale effects on venting 1 the 2 500 km kermadec tonga arc is the longest submarine arc on the planet here we report on the second of a series of cruises designed to investigate large scale controls on active hydrothermal venting on this arc the 2002 nzaplume ii cruise surveyed 12 submarine volcanic centers along 580 km of the middle kermadec arc mka extending a 1999 cruise that surveyed 260 km of the southern kermadec arc ska average spacing between volcanic centers increases northward from 30 km on backarc crust along the ska to 45 km on backarc crust along the southern mka to 58 km where the mka joins the kermadec ridge volcanic cones dominate in the backarc and calderas dominate the kermadec ridge the incidence of venting is higher along the mka 83 10 of 12 volcanic centers than the ska 67 8 of 12 but the relative intensity of venting as given by plume thickness areal extent and concentration of dissolved gases and ionic species is generally weaker in the mka this pattern may reflect subduction of the 17 km thick oceanic hikurangi plateau beneath the ska subduction of this basaltic mass should greatly increase fluid loss from the downgoing slab initiating extensive melting in the upper mantle wedge and invigorating the hydrothermal systems of the ska conversely volcanic centers in the southern mka are starved of magma replenishment and so their hydrothermal systems are waning farther north where the mka centers merge with the kermadec ridge fewer but larger magma bodies accumulate in the thicker older crust ensuring more widely separated caldera dominated volcanic centers

hydrothermal activity in the se tyrrhenian sea an overview of 30 years of research subduction related volcanic activity in the southeast tyrrhenian back arc basin has resulted in a large variety of calcalkaline rocks ranging from arc tholeiitic to shoshonitic and rhyolitic composition which were emplaced in both oceanic and continental crust hydrothermal systems in the se tyrrhenian sea have leached these magmatic rocks generating a wide range of oxyhydroxide and sulfide deposits all the hydrothermal occurrences formed at much shallower depths than those from the mid ocean ridges oxyhydroxide deposits metalliferous sediments crusts and nodules are almost pure hydrothermal formations with insignificant hydrogenetic and diagenetic contributions they exhibit strong separation of mn rich and fe rich end members with mn rich occurrences dominant their geochemistry suggests a relative enrichment of mn in the hydrothermal systems of the se tyrrhenian the sulfides are zn and pb rich but poor in cu and relatively poor in fe this suggests either deep seated magma chambers or boiling of the hydrothermal fluids beneath the seafloor as a consequence 1 cu and a large proportion of the fe are deposited as sulfides in the basement rocks and sediment cover 2 the hydrothermal fluids become relatively enriched in mn zn and pb a number of accessory sulfosalts and selenides not typical of mid ocean ridge massive sulfides are present

gps ground deformation patterns at mount st helens washington usa from 2004 to 2010 terra nova 24 148 155 2012 abstract gps measurements on mount st helens spanning the 2004 00 2010 85 time interval encompassing the 2004 2008 dome building eruption were analysed first a local reference frame was derived to isolate the volcanic ground deformation from the background tectonic pattern related to the interactions between the pacific juan de fuca and north american plates secondly the resulting ground deformation patterns were modelled to constrain magmatic sources results suggest a vertically elongated magma chamber centred at 8 9 km depth beneath the summit area that deflated during the beginning of the dome growth and inflated since january 2008 indicating that the same primary magma reservoir was active both during and after the eruption in a magmatic system that is persistent over the time

the precious metal rich south hercules mineralization western tasmania a possible subsea floor replacement volcanic hosted massive sulfide deposit south hercules is a newly delineated disseminated to semimassive base metal sulfide deposit with significant gold and silver grades the deposit lies a kilometer along strike south from the hercules mine a 2 0 mt polymetallic massive sulfide deposit in the mount read volcanics belt western tasmania the mineralization and alteration at the south hercules deposit has been divided into two major facies the mineralized sulfide facies and the carbonate facies the carbonate facies interfingers with and surrounds the upper part of the sulfide facies the mineralized sulfide facies includes three zones a massive pyrite or barite zone a siliceous or stringer sulfide zone and a sphalerite galena or pyrite zone the carbonate facies also consists of three zones a blebby carbonate chlorite zone a massive carbonate zone and a cherty carbonate zone the massive pyrite or barite zone contains significant gold grades and occurs mostly at the top of the sulfide facies this zone is characterized by colloform aggregates of pyrite and compact massive pyrite in chert the siliceous or stringer sulfide zone is a silicified and sericitized tuffaceous shale with disseminated to stringer pb zn mineralization the massive sphalerite galena or pyrite zone contains subordinate gold and silver and occurs as thin lenses toward the base of the sulfide facies significant zinc and lead values occur throughout the mineralized sulfide facies with the highest values occurring along stratigraphically controlled layers copper values are conspicuously low throughout the south hercules deposit rarely exceeding 0 5 percent the carbonate facies is conspicuous by its lack of significant precious metal and base metal grades mineragraphic investigations indicate that electrum occurs in two general associations with pyrite and with other sulfides such as sphalerite galena and tetrahedrite the electrum locked in the pyrite euhedra is generally fine grained 5 40 mu m whereas the electrum associated with other sulfides displays a range between 5 and 200 mu m microprobe analysis indicates that the fineness 1 000 au au ag wt for gold in the deposit ranges from 427 to 965 the delta 18 o isotope composition of the carbonate varies from 9 8 to 16 7 per mil and the delta 13 c values range from 3 5 to 0 6 per mil the calculated isotopic composition of the ore fluid at 150 degrees and 250 degrees c is consistent with derivation from evolved seawater sulfur isotope analyses of selected samples from the mineralized facies give delta 34 s values of 8 2 to 14 1 per mil which is in the same range as values from the rosebery deposit and consistent with values of sulfur derived from cambrian seawater the form texture mineralogy stable isotopes and fluid inclusion data for the south hercules deposit suggest that it was formed largely by a subsea floor replacement process from relatively low temperature 150 degrees 250 degrees c near neutral fluids the very low copper content and relatively high au ag pb zn ratio of the ores support a low temperature environment in which gold was transported as the au hs 2 super complex and pb and zn were transported as chloride complexes

magnetic properties of lunar materials meteorites luna and apollo returned samples abstract we present the first comprehensive study of the magnetic properties of lunar meteorites and compare them with measurements from apollo and luna returned samples 37 unpaired lunar meteorites were studied while new susceptibility measurements were performed on 88 luna soil and rock samples to complement published luna and apollo data new magnetic data were also obtained on 4 apollo mare basalt samples magnetic susceptibility and saturation remanence appear mainly controlled by the amount of metallic iron added by the regolith forming processes and meteoritic contamination as shown by a positive correlation with ni and ir content a decrease with depth in regolith core profiles and a decrease with increasing soil size fraction the three sources of lunar materials provide coherent range of magnetic properties although the much larger abundance of anorthositic highland samples in the meteorite collection allows one to better describe the properties of this major lunar lithology the observed range of saturation remanence implies that mare basalts cannot contribute significantly to the patchy lunar crustal magnetizations which must be attributed to superficial impact processed feldspathic or mafic lithologies

the magma system of mount st helens non linear high resolution p wave tomography abstract high resolution three dimensional images of p wave velocity anomalies below mt st helens washington were derived using tomographic inversion the model is a 27 5 21 20 km target volume parameterized by blocks 0 5 km per side the area included 39 stations and 5454 local events leading to 35 475 rays used in the inversion to diminish the effects of noisy data the laplacian was constrained to be small within horizontal layers providing smoothing of the model non linear effects were compensated for by iterating three dimensional ray tracing using pseudo bending between inversions and relocating earthquakes relative to the updated three dimensional model the structural differences between the linear and non linear inversions appear to be insignificant although the amplitudes of the anomalies are larger in the non linear models results indicate a low velocity anomaly 7 approximately 1 km in lateral extent from 1 5 to 3 km depths between 3 and 6 km depth the anomaly appears to spread out below 6 km depth the low velocity feature changes to a higher velocity perturbation with lower velocity perturbations flanking around the perimeter of the volcano the higher velocity material which correlates with the higher seismicity at that depth is interpreted as being a plug capping the low velocity magma chamber which begins below 9 km depth

regolith thickness over the lunar nearside results from earth based 70 cm arecibo radar observations the inversion of regolith thickness over the nearside hemisphere of the moon from newly acquired earth based 70 cm arecibo radar data is investigated using a quantitative radar scattering model the radar scattering model takes into account scattering from both the lunar surface and buried rocks in the lunar regolith and three parameters are critically important in predicting the radar backscattering coefficient the dielectric constant of the lunar regolith the surface roughness and the size and abundance of subsurface rocks the measured dielectric properties of the apollo regolith samples at 450 mhz are re analyzed and an improved relation among the complex dielectric constant bulk density and regolith composition is obtained the complex dielectric constant of the lunar regolith is estimated globally from this relation using the regolith composition derived from lunar prospector gamma ray spectrometer data to constrain the lunar surface roughness and abundance of subsurface rocks from radar data nine regions are selected as calibration sites where the regolith thickness has been estimated using independent analysis techniques for these sites scattering from the lunar surface and buried rocks cannot be perfectly distinguished and a tradeoff relationship exists between the size and abundance of buried rocks and surface roughness using these tradeoff relations as guidelines for globally representative parameters the regolith thickness of four regions over the lunar nearside is inverted and the inversion uncertainties caused by calibration errors of the radar data and model input parameters are analyzed the regolith thickness of the maria is generally smaller than that of highlands and older surfaces have thicker regolith thicknesses our approach cannot be applied to regions where the surface roughness is very high such as with young rocky craters and regions in the highly rugged highlands

drilling shallow water massive sulfides at the palinuro volcanic complex aeolian island arc italy a subseafloor replacement style barite and sulfide occurrence was drilled in shallow waters at the palinuro volcanic complex the northernmost aeolian arc volcano in the tyrrhenian sea italy using a lander type drilling device 11 successful drill holes yielded a total of 13 5 m of core from a sediment filled depression located at a water depth of 630 to 650 m the longest continuous drill core recovered consists of 4 84 m of massive to semimassive barite and sulfides with abundant late native sulfur overprint seafloor observations suggest that the hydrothermal system associated with the formation of the subseafloor barite and sulfide ore zone is still active although black smoker activity does not occur on the seafloor the recovered drill core shows that the subseafloor deposit is zoned with depth the top of the mineralized zone is comprised of a variably silicified vuggy barite sulfide facies that shows notable polymetallic metal enrichment while the deeper portion of the mineralized zone is dominated by massive pyrite having distinctly lower base and precious metal grades metal zonation of the barite and sulfide deposit is related to the evolution of the hydrothermal fluids in space and time the barite cap and the massive pyrite present in the deeper portion of the mineralized zone appear to have formed early in the paragenesis during the main stage of the mineralization the barite cap was brecciated and cemented by a polymetallic assemblage of barite and pyrite with minor chalcopyrite and tetrahedrite trace famatinite and rare cinnabar lower temperature precipitates formed during the main stage of mineralization include sphalerite galena pyrite opal a and barite which are associated with traces of pb sb as sulfosalts such as bournonite seligmannite or semseyite a distinct mineral assemblage of fine grained anhedral enargite hypogene covellite chalcopyrite and galena is commonly associated with colloform sphalerite galena and pyrite as a late phase of this main stage colloform pyrite and marcasite are the last sulfides formed in the paragenetic sequence the deposit is interpreted to have formed from fluids having an intermediate sulfidation state although excursions to high and very high sulfidation states are indicated by the presence of abundant enargite and hypogene covellite laser ablation and conventional sulfur isotope analyses show that pyrite formed close to the seafloor within the zone of polymetallic metal enrichment has a variable sulfur isotope composition 34s 39 to 3 whereas a more narrow range is observed in the massive pyrite at depth 34s 10 to 0 similar variations were also documented for the late native sulfur overprint overall the negative sulfur isotope ratios at depth the intermediate to very high sulfidation conditions during mineralization and the abundance of native sulfur suggest contributions of magmatic volatiles to the mineralizing fluids from a degassing magma chamber at depth biological processes are interpreted to have played a major role during late stages of ore formation the combination of a subseafloor replacement deposit with a massive to semimassive barite cap rock overlying massive pyrite the intermediate to high sulfidation characteristics and the strong biological influence on the late stages of mineralization are distinct from other modern seafloor massive sulfide deposits and represents a style of submarine mineralization not previously recognized in a modern volcanic arc environment the barite and sulfide occurrence at palinuro shares many characteristics with porphyry related base metal veins and intermediate sulfidation epithermal deposits suggesting that metallogenic processes associated with arc related magmatic hydrothermal systems are not restricted to the subaerial environment

the 3 d geological model around chang e 3 landing site based on lunar penetrating radar channel 1 data high frequency lunar penetrating radar lpr data from an instrument on the lunar rover yutu from the chang e 3 ce 3 robotic lander were used to build a three dimensional 3 d geological model of the lunar subsurface structure the ce 3 landing site is in the northern mare imbrium more than five significant reflection horizons are evident in the lpr profile which we interpret as different period lava flow sequences deposited on the lunar surface the most probable directions of these flows were inferred from layer depths thicknesses and other geological information moreover the apparent imbrian paleoregolith homogeneity in the profile supports the suggestion of a quiescent period of lunar surface evolution similar subsurface structures are found at the nasa apollo landing sites indicating that the cause and time of formation of the imaged phenomena may be similar between the two distant regions

spherical and ellipsoidal volcanic sources at long valley caldera california using a genetic algorithm inversion technique abstract we model the second inflation period at long valley caldera california using a genetic algorithm technique and high quality geodetic measurements of elevation changes and baseline extensions we compare two source inversions for both spherical mogi point sources and the finite prolate ellipsoid of yang and davis a sensitivity analysis for the genetic algorithm is performed based upon synthetic data set inversions on similar sources in order to better constrain the areal location orientation and volume of the potential sources the spherical sources are well constrained the larger located at 9 9 km beneath the resurgent dome with a volume of 0 036 km 3 while the second at only 0 008 km 3 is located at a depth of 7 3 km beneath the south moat the depths to the ellipsoidal sources are switched with the larger source at a depth of 9 6 km and the smaller at 11 8 km with volumes of 0 037 and 0 002 km 3 respectively

vp structure of mount st helens washington usa imaged with local earthquake tomography we present a new p wave velocity model for mount st helens using local earthquake data recorded by the pacific northwest seismograph stations and cascades volcano observatory since the 18 may 1980 eruption these data were augmented with records from a dense array of 19 temporary stations deployed during the second half of 2005 because the distribution of earthquakes in the study area is concentrated beneath the volcano and within two nearly linear trends we used a graded inversion scheme to compute a coarse grid model that focused on the regional structure followed by a fine grid inversion to improve spatial resolution directly beneath the volcanic edifice the coarse grid model results are largely consistent with earlier geophysical studies of the area we find high velocity anomalies nw and ne of the edifice that correspond with igneous intrusions and a prominent low velocity zone nnw of the edifice that corresponds with the linear zone of high seismicity known as the st helens seismic zone this low velocity zone may continue past mount st helens to the south at depths below 5 km directly beneath the edifice the fine grid model images a low velocity zone between about 2 and 3 5 km below sea level that may correspond to a shallow magma storage zone and although the model resolution is poor below about 6 km we found low velocities that correspond with the aseismic zone between about 5 5 and 8 km that has previously been modeled as the location of a large magma storage volume

initial results for the north pole of the moon from mini sar chandrayaan 1 mission 1 we present new polarimetric radar data for the surface of the north pole of the moon acquired with the mini sar experiment onboard india s chandrayaan 1 spacecraft between mid february and mid april 2009 mini sar mapped more than 95 of the areas polewards of 80 latitude at a resolution of 150 meters the north polar region displays backscatter properties typical for the moon with circular polarization ratio cpr values in the range of 0 1 0 3 increasing to over 1 0 for young primary impact craters these higher cpr values likely reflect surface roughness associated with these fresh features in contrast some craters in this region show elevated cpr in their interiors but not exterior to their rims almost all of these features are in permanent sun shadow and correlate with proposed locations of polar ice modeled on the basis of lunar prospector neutron data these relations are consistent with deposits of water ice in these craters

relationships between microstructure and composition in enargite and luzonite cu 3 as sb s 4 minerals commonly contain structurally disordered crystals of intergrown enargite and the luzonite famatinite series posfai and sundberg 1998 here we discuss the relationships between the fine scale structural variations and the sb as ratios of these minerals although luzonite typically contains more sb than enargite individual layers of luzonite within sb bearing enargite are not associated with higher sb as ratios defect free enargite can also contain sb we develop a structure composition diagram in which both the structural enargite luzonite and the compositional luzonite famatinite solid solutions can be represented compositions plotted in this diagram reveal that sb bearing enargite and luzonite contain only a relatively small number of defects whereas sb free crystals can be heavily disordered coexisting enargite and famatinite and zoning in luzonite famatinite indicate fluctuations in the sb content of the fluid during ore deposition on the other hand assemblages of sb free enargite and luzonite probably reflect thermal oscillations heavily disordered intermediate structures may have formed near the transition temperature of low temperature luzonite to high temperature enargite our results suggest that characteristic microstructures in enargite luzonite and famatinite can be useful for constraining fluid composition and temperature during ore deposition

radar sounding of temperate permafrost in alaska analogy to the martian midlatitude to high latitude ice rich terrains 1 radar detection of subsurface ice on mars has been widely debated in part because the dielectric signature of ice as deduced from the dielectric constant can be confused with dry silicate rich materials to identify the ice dielectric signature it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss unfortunately the latter remains poorly quantified at both mars advanced radar for subsurface and ionospheric sounding marsis and shallow subsurface radar sharad frequencies to address this ambiguity we conducted multiple frequency ground penetrating radar and resistivity investigations in well characterized temperate permafrost in fairbanks alaska the area shows several geomorphologic similarities to midlatitude and high latitude terrains on mars this approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 mhz frequency band at 20 mhz our results suggest an average dielectric loss rate of 0 25 0 03 db m whereas the corresponding average scattering loss rate is 0 94 0 37 db m the scattering loss was found to represent 69 of the total signal attenuation considering this result and the study by heggy et al 2006a in volcanic environments we revised the interpretation of the attenuation coefficient calculated from sharad data over the deuteronilus mensae region and amazonis planitia we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity our results suggest that even if deuteronilus mensae deposits and the vastitas borealis formation may have similar dielectric constants their imaginary parts are different this implies that the two regions have different bulk compositions with the former being ice rich sediments and the latter being nonconsolidated volcanic deposits

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

high so2 flux sulfur accumulation and gas fractionation at an erupting submarine volcano strombolian style volcanic activity has persisted for six years at the nw rota 1 submarine volcano in the southern mariana arc allowing direct observation and sampling of gas rich fluids produced by actively degassing lavas and permitting study of the magma hydrothermal transition zone fluids sampled centimeters above erupting lava and percolating through volcaniclastic sediments around an active vent have dissolved sulfite 100 mmol kg total dissolved sulfide 1 mmol kg if nw rota is representative of submarine arc eruptions then volcanic vent fluids from seawater lava interaction on submarine arcs have a significant impact on the global hydrothermal flux of sulfur and al to the oceans but a minimal impact on mg removal gas ratios so 2 co 2 h 2 and he are variable on small spatial and temporal scales indicative of solubility fractionation and gas scrubbing elemental sulfur s e is abundant in solid and molten form produced primarily by disproportionation of magmatic so 2 injected into seawater s e accumulates within the porous rock surrounding the lava conduit connecting the magma source to the seafloor accumulated s e can be heated melted and pushed upward by rising magma to produce molten s e flows and lavas saturated with s e molten s e near the top of the lava conduit may be ejected up into the water column by escaping gases or boiling water this mechanism of s e accumulation and refluxing may underlie the relatively widespread occurrence of s e deposits of many sizes found on submarine arc volcanoes

on magma chamber evolution during slow effusive eruptions 1 we explore some of the controls on the evolution of a slow effusive eruption imposed by processes in a shallow magma reservoir we envisage that the emplacement of basaltic magma into a shallow evolved crustal reservoir generates sufficient overpressure to trigger the slow effusive eruption of the overlying layer of evolved magma the subsequent evolution of the system then depends on a number of factors including 1 the volatile contents of the two magmas 2 the rate of any continuing influx of basalt 3 the cooling heating rates of the two layers of magma and 4 the eruption rate of the silicic magma where we assume that the crystals and bubbles remain in the layer in which they formed any exsolved volatiles in the magma increase the compressibility of the magma in a waning system this tends to increase the volume of material which needs to be erupted to relieve a given overpressure by an amount of order 10 100 and hence increases the duration of the eruption typical calculations suggest that eruptions from magma chambers of size 1 10 km3 may persist for times of order 1 10 years if the main body of silicic magma is saturated in volatiles in addition cooling of the basalt leads to formation of dense crystals which lowers the pressure however if the magma becomes saturated exsolution of volatile gases occurs tending to increase the pressure again in a waning system this tends to extend the eruption duration and increase the mass erupted from the chamber for chamber volumes of 1 10 km3 cooling rates of 10 6 k s can increase the eruption volume by a factor of order 10 rapid cooling may also lead to an initial increase in the eruption rate while the chamber pressure is controlled by the rate of production of new bubbles if there is an influx of basalt to the chamber which is maintained during the eruption then the evolution of the eruption is primarily dependent on this input rate although the cooling of the basalt may increase the eruption rate to values in excess of this input rate especially at an early stage in the eruption the complex and nonlinear evolution of the eruption rate predicted by our simple model illustrates the sensitivity of the eruption rate to the magma volatile content and magma cooling rates such understanding is key in developing quantitative models for hazard assessments of slow effusive eruptions

comparative analysis of reflection characteristics of lunar penetrating radar data using numerical simulations abstract the moon and most extraterrestrial objects are lacking in water thus electromagnetic waves can penetrate deep into the ground and bring some structural information about the regolith and surrounding rocks as an important assistant to the existing payloads ground penetrating radar gpr is particularly suitable for deep space exploration which is feasible and necessary for detecting the subsurface structures mainly associated with the dielectric permittivity variations of extraterrestrial objects unfortunately there are not enough reference gpr profiles or drills on the extraterrestrial objects to constrain the acquired data here we construct some typical models and perform numerical simulations to make the results reasonable various factors are considered including the type scale and location of the abnormal bodies then we review the reflecting phenomenon under the ground and perform comparative analyses on the reflection characteristics of different models finally we present some criteria for identifying different reflectors using critical patterns of reflections the configuration of our numerical experiments is comparable to that of the lunar penetrating radar onboard the yutu 1 and 2 thus the results would be reliable to support the geological interpretation of detected records as well as possible gpr detection on extraterrestrial objects in the future this work is helpful for recognizing the reflection characteristics of the observed gpr data and would be beneficial to uncovering more critical details of subsurface structures

improved constraints on the estimated size and volatile content of the mount st helens magma system from the 2004 2008 history of dome growth and deformation 1 the history of dome growth and geodetic deflation during the 2004 2008 mount st helens eruption can be fit to theoretical curves with parameters such as reservoir volume bubble content initial overpressure and magma rheology here assumed to be newtonian viscous with or without a solid plug in the conduit center data from 2004 2008 are consistent with eruption from a 10 25 km3 reservoir containing 0 5 2 bubbles an initial overpressure of 10 20 mpa and no significant sustained recharge during the eruption we used curve fits to project the eruption s final duration and volume early projections predicted a final volume only about half of the actual value but projections increased with each measurement implying a temporal increase in reservoir volume or compressibility a simple interpretation is that early effusion was driven by a 5 10 km3 integrated core of fluid magma this core expanded with time through creep of semi solid magma and host rock

evidence of a shallow persistent magmatic reservoir from joint inversion of gravity and ground deformation data the 25 26 october 2013 etna lava fountaining event

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

hydrothermal nontronite formation at eolo seamount aeolian volcanic arc tyrrhenian sea abstract a sediment core containing a yellowish green clay bed was recovered from an area of extensive hydrothermal deposition at the se slope of the eolo seamount tyrrhenian sea the clay bed is composed of pure nontronite described for the first time in the tyrrhenian sea which appears to be the most aluminous nontronite ever found among the seafloor hydrothermal deposits the high al content suggests precipitation from al containing hydrothermal solutions the ree distribution of the eolo nontronite has a v shape pattern the heavy ree enrichment is in part due to their preferential partitioning in the nontronite structure this enrichment was possibly further enhanced by the hree preferential sorption on bacterial cell walls the light ree enrichment is the result of scavenging uptake by one of the nontronite precursors i e poorly ordered fe oxyhydroxides from the hydrothermal fluids oxygen isotopic composition of the nontronite yields a formation temperature of 30 c consistent with a low temperature hydrothermal origin the relatively radiogenic nd isotopic signature of the nontronite compared to the present day mediterranean seawater indicates that approximately half of nd and presumably the rest of the lree are derived from local volcanic sources on the other hand 87 sr 86 sr is dominated by present day seawater sr scanning electron microscopy investigation revealed that the nontronite is composed of aggregates of lepispheres and tube like filaments which are indicative of bacteria assisted precipitation bacteria inhabiting this hydrothermal site likely acted as reactive geochemical surfaces on which poorly ordered hydrothermal fe oxyhydroxides and silica precipitated upon aging the interactions of these primary hydrothermal precipitates coating bacterial filaments and cell walls likely led to the formation of nontronite finally the well balanced interlayer and layer charges of the crystal lattice of seafloor hydrothermal nontronite decrease its sorption capacity to zero thus the ubiquitous nontronite precipitation along the active plate boundaries and around the hot spots has no significant impact on oceanic trace element chemistry

copper ore grade hydrothermal mineralization discovered in a seamount in the tyrrhenian sea mediterranean is the mineralization related to porphyry coppers or to base metal lodes abstract a luzonite and tennantite tetrahedrite bearing massive sulfide mineralization was discovered when sampling the crater of the palinuro seamount located within a probable island arc or marginal basin tectonic setting the mineralization is made up of indurated sulfide crusts interpreted to have been deposited by a seawater sediment interface and mixed with ooze of organic and volcanic origin a preliminary investigation of the economic minerals showed besides luzonite and tennantite tetrahedrite native rare copper all associated with pyrite predominantly and baryte native silver bismuthinite and stibnite were also found a dust like white precipitate was observed by submersible close to the mineralized zone but no structures or edifices resembling black smokers have yet been identified massive pyrite deposits associated with such uncommon mineral assemblages are found in the high level volcanic parts of porphyry copper systems or associated with base metal lodes the massive sulfide discovery is suggested to have a volcanogenic exhalative origin and a genetic relationship with porphyry coppers or base metal sulfide lodes

a story of regolith told by lunar penetrating radar abstract knowledge of the lunar regolith not only provides important information about lunar geology but is also critical to quantifying potential resources for lunar exploration and engineering for human outposts the lunar penetrating radar lpr onboard china s chang e 3 ce 3 provides a unique opportunity for mapping the subsurface structure and the near surface stratigraphic structure of the regolith a radar image with high resolution can be produced using a data processing pipeline the contact interface of the regolith and the basement rock is explored according to forward simulation results f k frequency wavenumber filtering that highlights the contact surface of the regolith and the basement rock is carried out the energy distribution of the lpr data helps to stratify the lunar regolith finally by combining this with the history of the moon regional geology and particularly the lpr data we deduce the evolution of the regolith on the ce 3 landing site

geodynamic implications of subduction related magmatism insights from the tyrrhenian apennines region abstract the location and age of potassic and ultra potassic magmatism mostly recognized as derived from mantle sources hybridized by subducted crustal rocks in the tyrrhenian apennines system do not show any plausible causal relationship with the evolutionary history of subduction processes reconstructed from the time pattern of accretionary activity in the apenninic belt on the other hand since magmatism in the study area was always associated in space and time with major phases of crustal stretching one could think that the uprise of magmas through the uppermost lithosphere is strictly conditioned by the occurrence of extensional tectonics and in particular by the formation of significant fractures in the upper brittle crust this would imply that using the distribution of subduction related magmatism for recognizing the timing and location of paleosubduction processes could be misleading the geochemical features of these magmas can provide information on the kind of tectonophysical processes which took place in the mantle during the previous evolution but as far as we know the delay between mantle hybridization and magmatic activity cannot easily be assessed

parameters and structure of lunar regolith in chang e 3 landing area from lunar penetrating radar lpr data abstract chang e 3 ce 3 landed in the northwest mare imbrium a region that has not been explored before yutu rover that released by ce 3 lander carried the first lunar surface penetrating radar lpr for exploring lunar regolith thickness and subsurface shallow geological structures in this paper based on the lpr data and the panoramic camera pc data we first calculate the lunar surface regolith parameters in ce 3 landing area including its permittivity density conductivity and feo tio2 content lpr data provides a higher spatial resolution and more accuracy for the lunar regolith parameters comparing to other remote sensing techniques such as orbit radar sounder and microwave sensing or earth based powerful radar we also derived the regolith thickness and its weathered rate with much better accuracy in the landing area the results indicate that the regolith growth rate is much faster than previous estimation the regolith parameters are not uniform even in such a small study area and the thickness and growth rate of lunar regolith here are different from other areas in mare imbrium we infer that the main reason should be geological deformation that caused by multiple impacts of meteorites in different sizes

contemporary vertical crustal deformation in cascadia abstract data from 29 tide gauges and 113 pairs of first and second order leveling lines are analyzed to determine the pattern of vertical deformation in the pacific northwest of the united states the data span nearly 100 years and represent the interseismic elastic deformation related to the great earthquake cycle uplift rates calculated from leveling surveys are adjusted to a model surface in the tidal reference frame using a robust weighted linear least square technique rapid uplift occurs in two distinct broad regions along the coast separated by a narrow zone of slow subsidence vertical deformation rates range from 4 mm year of uplift on southern vancouver island to 2 mm year of subsidence in northern coastal oregon the deformation pattern is consistent with the results of previous studies and subduction models

submarine hydrothermal activity and gold rich mineralization at brothers volcano kermadec arc new zealand brothers volcano of the kermadec intraoceanic arc is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world it has two distinct vent fields known as the nw caldera and cone sites whose geology permeability vent fluid compositions mineralogy and ore forming conditions are in stark contrast to each other the nw caldera site strikes for 600 m in a sw ne direction with chimneys occurring over a 145 m depth interval between 1 690 and 1 545 m at least 100 dead and active sulfide chimney spires occur in this field and are typically 2 3 m in height with some reaching 6 7 m their ages at time of sampling fall broadly into three groups 4 23 and 35 years old the chimneys typically occur near the base of individual fault controlled benches on the caldera wall striking in lines orthogonal to the slopes rarer are massive sulfide crusts 2 3 m thick two main types of chimney predominate cu rich up to 28 5 wt cu and more commonly zn rich up to 43 8 wt zn geochemical results show that mo bi co se sn and au up to 91 ppm are correlated with the cu mineralization whereas cd hg sb ag and as are associated with the dominant zn rich mineralization the cone site comprises the upper cone site atop the summit of the recent main dacite cone and the lower cone site that straddles the summit of an older smaller more degraded dacite cone on the ne flank of the main cone huge volumes of diffuse venting are seen at the lower cone site in contrast to venting at both the upper cone and nw caldera sites individual vents are marked by low relief 0 5 m mounds comprising predominately native sulfur with bacterial mats vent fluids of the nw caldera field are focused hot 300 c acidic ph 2 8 metal rich and gas poor calculated end member fluids from nw caldera vents indicate that phase separation has occurred with cl values ranging from 93 to 137 of seawater values by contrast vent fluids at the cone site are diffuse noticeably cooler 122 c more acidic ph 1 9 metal poor and gas rich higher than seawater values of so4 and mg in the cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water rock interactions iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from fe rich brines evidence for magmatic contributions to the hydrothermal system at brothers includes high concentrations of dissolved co2 e g 206 mm kg at the cone site high co2 3he negative d and 18oh2o for vent fluids negative 34s for sulfides to 4 6 sulfur to 10 2 and 15n2 to 3 5 vent fluid ph values to 1 9 and mineral assemblages common to high sulfidation systems changing physicochemical conditions at the brothers hydrothermal system and especially the cone site occur over periods of months to hundreds of years as shown by interlayered cu au and zn rich zones in chimneys variable fluid and isotopic compositions similar shifts in 3he 4he values for both cone and nw caldera sites and overprinting of magmatic mineral assemblages by water rock dominated assemblages metals especially cu and possibly au may be entering the hydrothermal system via the dissolution of metal rich glasses they are then transported rapidly up into the system via magmatic volatiles utilizing vertical 2 5 km long narrow 300 m diameter pipes consistent with evidence of vent fluids forming at relatively shallow depths the nw caldera and cone sites are considered to represent stages along a continuum between water rock and magmatic hydrothermal dominated end members

neogene and quaternary rollback evolution of the tyrrhenian sea the apennines and the sicilian maghrebides reconstruction of the evolution of the tyrrhenian sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 ma it involved two episodes of back arc extension which were induced by the rollback of a west dipping subducting slab the first period of extension 10 6 ma was prominent in the northern tyrrhenian sea and in the western part of the southern tyrrhenian sea the second period of extension mainly affected the southern tyrrhenian sea began in the latest messinian 6 5 ma and has been accompanied by subduction rollback at rates of 60 100 km myr 1 slab reconstruction combined with paleomagnetic and paleogeographic constraints indicates that in the central apennines the latest messinian 6 5 ma arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike slip faults these processes resulted in the formation of a narrow subducting slab beneath the ionian sea that has undergone faster subduction rollback and induced extreme rates of back arc extension

mt etna 2001 eruption new insights into the magmatic feeding system and the mechanical response of the western flank from a detailed geodetic dataset abstract in the last decades the increasing availability of comprehensive geodetic datasets has allowed for more detailed constraints on subsurface magma storage and conduits at several active volcanoes worldwide here by using a large dataset of geodetic measurements collected between early january 2001 and august 2001 we identified at least six different deformation stages that allow us to quantify the surface deformation patterns before during and after the 2001 mt etna volcanic eruption our results are largely in agreement with previous works e g the presence of a deep inflating source and a shallow dike located beneath the north western and upper southern flanks of the volcano respectively however we provide 1 finer resolution of the temporal activity of these magmatic sources leading to 2 new evidence related to the evolution of the magmatic system and the mechanical response of the western flank in particular during the pre eruptive phase results and analysis show a clear change in the ground deformation pattern of the volcano in response to the 20 24 april 2001 seismic swarm that occurred beneath the western flank evolving from a volcano wide inflation to a slight deflation of the summit area we suggest that the source responsible for the volcano wide inflation beginning in the fall of 2000 experienced a drastic reduction in the inflation rate in response to this seismic swarm moreover we provide evidence for the presence of a new inflating source located beneath the upper southern flank at a depth of 7 0 km bsl that triggered both the occurrence of the 20 24 april 2001 seismic swarm and led to the rapid ascent of magma upward to the surface after 12 july the lower vents system was fed by fresh magma rising from this source the presence of this inflating source is inferred by 1 seismological and volcanological observations coming from the 2001 eruption and 2 seismological constraints coming from a previous similar episode that occurred at etna during the 1993 1998 period furthermore both shallow deflations observed after the 20 24 april 2001 seismic swarm and during the first day of the eruption also could be due to the deflation of two adjacent portions of the same shallow 2 km bsl reservoir such reservoirs would feed the activity that occurred at the south east crater after january 2001 and the activity of the upper vents system during the july august eruption in agreement with petrochemical observations through an updated revision of the available data we shed some light on the relevance of pre eruptive activity patterns an important element for an effective volcano monitoring

tectonic features of the lipari vulcano complex aeolian archipelago italy from 10 years 1996 2006 of gps data this research has benefited from funding provided by the italian presidenza del consiglio dei ministri dipartimento della protezione civile dpc

estimation of the permittivity and porosity of the lunar uppermost basalt layer based on observations of impact craters by selene 1 we have investigated the geological conditions below two lava flow units through determining the bulk permittivity and porosity in the uppermost basalt layer to depths of a few hundred meters we use a newly developed method based on three data sets obtained by the lunar radar sounder lrs multiband imager mi and terrain camera tc onboard the selenological and engineering explorer selene kaguya spacecraft the bulk permittivity of the uppermost basalt layer is calculated as the ratio of the apparent radar depth to the thickness of the uppermost basalt layer its thickness can be constrained from the excavation depths of two types of craters haloed and nonhaloed craters these craters are identified on the basis of feo and or tio2 maps created from the mi data these excavation depths are determined based on the measurement of the crater diameter using the tc data the apparent radar depth is derived from the time delay between the surface echo and subsurface echo measured by lrs near the craters the bulk permittivities are estimated to be 2 8 5 5 in a lava flow unit of mare humorum and 4 2 18 0 in a lava flow unit of mare serenitatis these bulk permittivities are indicative of porous basalt layers with the porosities of 19 51 in the unit of humorum and 0 33 in the unit of serenitatis the estimated porosities would be mainly explained by two different sources intrinsic voids of lava and impact induced cracks

chang e 4 initial spectroscopic identification of lunar far side mantle derived materials over 60 years of spacecraft exploration has revealed that the earth s moon is characterized by a lunar crust1 dominated by the mineral plagioclase overlying a more mafic richer in iron and magnesium mantle of uncertain composition both crust and mantle formed during the earliest stages of lunar evolution when late stage accretional energy caused a molten rock magma ocean flotation of the light plagioclase sinking of the denser iron rich minerals such as olivine and pyroxene and eventually solidification2 very large impact craters can potentially penetrate through the crust and sample the lunar mantle the largest of these craters is the approximately 2 500 kilometre diameter south pole aitken spa basin3 on the lunar far side evidence obtained from orbiting spacecraft shows that the floor of the spa basin is rich in mafic minerals4 but their mantle origin is controversial and their in situ geologic settings are poorly known china s chang e 4 lunar far side lander recently touched down in the von karman crater5 6 to explore the floor of the huge spa basin and deployed its rover yutu 2 here we report on the initial spectral observations of the visible and near infrared spectrometer vnis 7 onboard yutu 2 which we interpret to represent the presence of low calcium ortho pyroxene and olivine materials that may originate from the lunar mantle geological context6 suggests that these materials were excavated from below the spa floor by the nearby 72 km diameter finsen impact crater event and transported to the landing site continued exploration by yutu 2 will target these materials on the floor of the von karman crater to understand their geologic context origin and abundance and to assess the possibility of sample return scenarios initial spectral observations by china s chang e 4 far side lunar rover suggest the presence of materials that may originate from the moon s mantle

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

dielectric properties estimation of the lunar regolith at ce 3 landing site using lunar penetrating radar data abstract the second channel ch2 of the lunar penetrating radar lpr carried on the chang e 3 ce 3 yutu rover was used to determine the thickness and structure of the lunar regolith accurately revealing the true structure beneath the surface requires knowledge of the dielectric permittivity of the regolith which allows one to properly apply migration to the radar image in contrast to simple assumptions in previous studies this paper takes account of heterogeneity of the regolith and derives regolith s permittivity distribution laterally and vertically by a method widely used in data processing of terrestrial ground penetrating radar gpr we find that regolith permittivity at the landing site increases with depth more quickly than previously recognized at a depth of 2 5 3 m the dielectric constant reaches the value of solid basalt the radar image was migrated on the basis of the permittivity profile we do not find any continuous distinct layers or an apparent regolith rock interface in the migrated radargram which implies that this area is covered by relatively young poorly layered deposits

magma transport and storage at mt etna italy a review of geodetic and petrological data for the 2002 03 2004 and 2006 eruptions abstract a detailed reconstruction of magma movements within the plumbing system of mt etna volcano has been made by reviewing the eruptions occurring during the october 2002 december 2006 period the availability of continuous gps data allowed detecting at least ten different ground deformation stages highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion these data have been coupled with the available petrological datasets including major trace elements and sr nd pb isotope compositions for the volcanic rocks erupted in the 2002 2006 period we identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano the former is located at a depth of 7 km bsl and fed the 2001 and 2002 03 eruptions while the latter located from 3 5 to 5 5 km bsl fed the 2004 05 and 2006 eruptions petrological characteristics of emitted products have been correlated with the inflation vs deflation cycles related to the identified sources providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature finally we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002 03 eruption as a consequence of the major seaward motion of the eastern flank of the volcano