a physical basis for the frictional melting of some rock forming minerals abstract under conditions of coseismic slip 0 1 2 0 m s 1 within the upper crust differences in the shear yield strengths fracture toughnesses melting points and to a lesser extent thermal conductivities of rock forming minerals result in a hierarchy of friction melting susceptibilities in many so called pseudotachylytes it is observed that phyllosilicates and amphiboles are preferentially consumed to form the melt phase whilst quartz and feldspar tend to survive as clasts this can be explained in terms of the disequilibrium flash melting of those mineral phases possessing the lower shear yield strengths fracture toughnesses and thermal conductivities rather than by eutectic melting that would otherwise generate equilibrium minimum melts indicative of igneous processes at high strain rates typical of coseismic faulting the mechanical behaviour of minerals is primarily controlled by their fracture toughnesses with progressive comminution during slip leading to fusion the friction melting dependence on the mechanical properties of minerals indicates that there may be an important relationship between wall rock lithology and earthquake magnitude if frictional melting results in fault lubrication

physical properties of tuffs from a scientific borehole at alban hills volcanic district central italy recent seismic swarms and hydrothermal activity suggest that the quaternary volcanic complex of the alban hills may pose a threat to the city of rome a 350 m scientific borehole was therefore drilled into this volcanic area to elucidate its inner structure for the first time wire line logs were run in the borehole in order to characterize the physical properties of the rocks and their variations with depth in particular a detailed sonic log was run to measure the p wave velocity from the well head down to 110 m to further investigate velocity changes we carried out laboratory measurements of p and s elastic wave velocities and fluid permeability at effective pressures up to 70 mpa during both increasing and decreasing pressure cycles on selected core samples representative of the main volcanic units specifically we studied samples from two pyroclastic units representative of two classes of volcanic deposits that are representative of the whole succession i a coarse grained well lithified facies pozzolane rosse unit containing abundant mm to cm lava clasts and crystals and ii a fine grained matrix supported pyroclastic deposit tufo pisolitico di trigoria unit with rare lithic lava clasts and sparse pumice elastic wave velocities reveal significant differences between units and indicate how within the same lithology the different degree of lithification and presence of clasts can affect significantly physical property values the mean laboratory value of the p wave velocity for pozzolane rosse and tufo pisolitico di trigoria units is respectively of 3 75 and 3 2 km s at an effective pressure equivalent to that at the depth at which the sonic velocity was measured under increasing effective pressure a profound influence on the transport properties is observed permeability ranges from the order of 10 18 m 2 for the pozzolane rosse unit to the order of 10 15 m 2 for the tufo pisolitico di trigoria unit in good agreement with the shallow aquifer circulating in the shallower units c 2008 elsevier b v all rights reserved

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

impact induced frictional melting in ordinary chondrites a mechanism for deformation darkening and vein formation high speed friction experiments have been performed on the ordinary chondrites el hammami h5 s2 and sahara 97001 l6 s3 using an axial friction welding apparatus each sample was subjected to a strain rate of 103 to 104 s 1 which generated 250 to 500 m deep darkened zones on each sample cube thin section analyses reveal that the darkened areas are composed of silicate glass and mineral fragments intermingled with dispersed submicron size feni and fes blebs fracturing of mineral grains and the formation of tiny metallic veins define the extent of deformation beyond the darkened shear zone these features are not present in the original meteorites the shear zones and tiny veins are quite similar to certain vein systems seen in naturally deformed ordinary chondrites the experiments show that shock deformation is not required for the formation of melt veins and darkening in ordinary chondrites therefore the presence of melt veins and darkening does not imply that an ordinary chondrite has undergone severe shock deformation in fact high strain rate deformation and frictional melting are especially important for the formation of veins at low shock pressures

the colli albani mafic caldera roma italy stratigraphy structure and petrology new results for the colli albani volcano roma italy surveyed for the geological map of italy at 1 50 000 scale carg project integrated with previous data provide insights on caldera evolution the colli albani a quiescent volcano became active at 600 ka eruptive compositions are consistently mafic 50 km 3 deposits forming the villa senni eruption unit ignimbrites at ca 355 ka two edifices were built within the caldera 1 the horseshoe shaped tuscolano artemisio ta composite edifice or lithosome consists of coalescing peri caldera fissure related scoriae cones interbedded with lava flows the fissure system forms two segments controlled by regional fractures 2 the steep sided faete stratovolcano 949 m a s l filled the caldera the ta and faete lithosomes partly interfinger and were emplaced at 350 260 ka their products indicate reduced eruption rates relative to the vl period and a change to effusive and mildly explosive eruptions the most recent and still active phase of phreatomagmatic activity formed overlapping maars and tuff cones along the western and northern slopes of the volcano collectively named via dei laghi composite lithosome the colli albani caldera is poly phase 1 a piecemeal caldera is associated with large volume ignimbrites of the vl edifice the present shape of the caldera is related to the villa senni eruption 2 the ta composite edifice erupted from peripheral caldera fissures is unrelated to explosive phases of caldera collapse the ta final products cover a morphologically stable caldera wall the peripheral fractures feeding the ta composite edifice are interpreted as volcano tectonic structures activated during the late stage downsag of the caldera reduced eruption rates during the ta and the faete stages 10 1 km 3 1 ka respect to 10 0 km 3 1 ka for the vl edifice suggest a reduced recharge of the magma chamber that may have induced prolonged deflation and downsagging of the caldera floor and the opening of outward dipping peripheral fractures by this interpretation the ta edifice represents the surface expression of ring dykes at depth the absence of similar fissure structures along the western caldera rim may relate to the deep geometry of the ring faults dipping inward in those areas and therefore not favourably oriented for magma intrusion during a period of general subsidence by contrast the following and still active phreatomagmatic phase that has emplaced the via dei laghi composite edifice is located right on the western side of the caldera and may therefore relate to resurgent conditions classical petrological and pers pearce elements ratios analyses indicate that lavas are co genetic and show a differentiation trend up through stratigraphy driven by

metal veins in the kernouve h6 s1 chondrite evidence for pre or syn metamorphic shear deformation abstract kernouve is an h6 chondrite that experienced a very small degree of late stage shock loading s1 however kernouve contains fe ni metal vein like structures whose formation have been attributed to an early impact event to establish the formation conditions of metal veins in kernouve we examined the three dimensional 3d arrangement of metal vein like structures and typical metal grains in two samples of kernouve with x ray microtomography ct at resolutions of 11 m voxel we additionally investigated the 3d structure of the porosity present in kernouve using ct at two different resolutions 3 and 11 m voxel these data and optical microscopy support the hypothesis that kernouve has experienced little post metamorphic shock however the moderate 5 8 vol porosity of kernouve is in the form of intergranular voids rather than cracks which indicates any cracking that may have existed in the relatively brittle silicate grains was annealed we estimate that 70 80 of the primordial porosity in kernouve was removed by impact related compaction moreover we found no collective orientation of metal grains so high metamorphic temperatures following compaction erased any common orientation of metal grains due to compaction we propose that the metal vein structures can be explained as a pre or syn metamorphic shock induced process which we infer was primarily shear deformation with some uniaxial compaction also occurring the coarse metal veins probably formed by accumulation of ductile metal grains along shear zones a process that would have been facilitated by having an already warm h chondrite parent body when shock occurred i e syn metamorphic shock the complexity of shape including numerous tendrils expanding from the primary structure of the veins in kernouve is likely due to the coalescence of metal by metamorphic growth after the shear event the metal veins in kernouve thus appear to record evidence for early shock induced metal mobilization and the maximum shock pressure experienced by kernouve may have been 21 gpa our study suggests that collision induced segregation of metal occurred at an early stage in low gravity planetesimals consistent with the idea that this process could have been important for the differentiation of such objects

gravitational slope deformation of a resurgent caldera new insights from the mechanical behaviour of mt nuovo tuffs ischia island italy abstract ischia island italy is an impressive example of the rare phenomenon of caldera resurgence the emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m concentrated in the western portion of mt epomeo 789 m a s l as a consequence of this uplift the island has experienced several slope instabilities at different scales since the holocene from shallow mass movements to large rock and debris avalanches these mass wasting events which mobilised large volumes of greenish alkali trachytic tuff the mt epomeo green tuff megt were strictly related to volcano tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island deep seated gravitational slope deformation dsgsd at mt nuovo located adjacent to densely populated coastal villages is an ongoing process that covers an area of 1 6 km 2 the mt nuovo dsgsd involves a rock mass volume of 190 mm 3 and is accommodated by a main shear zone and a series of sub vertical fault zones associated with high angle joint sets to improve our understanding of this gravity induced process we performed a physical porosity and permeability and mechanical uniaxial and triaxial deformation experiments characterisation of two ignimbrite deposits both from the megt that form a significant component of the nw sector of mt epomeo the main conclusions drawn from our experiments are twofold first the presence of water dramatically reduces the strength of the tuffs suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability second the transition from brittle dilatant to ductile compactant behaviour in the tuffs of the megt occurs at a very low effective pressure analogous to a depth of a couple of hundred metres and that this transition is likely moved closer to the surface in the presence of water we hypothesise that compactant porosity decreasing behaviour at the base of the layer could therefore facilitate slope instability although our results show that transient exposure to 300 c does not influence the short term strength of the tuff we speculate that the high in situ temperature could increase the efficiency of brittle and compactant creep and therefore increase the rate of slope deformation taken together our experimental data highlight a potentially important role for the hydrothermal system that reaches a minimum depth of 1 km in dictating the dsgsd at mt nuovo an understanding of this deformation process is not only important for the proximal coastal villages at risk of engulfment by a large debris avalanche but also for the towns and cities along the coast of the gulf of naples that are at risk to a secondary consequence of such an avalanche a tsunami wave

post caldera activity in the alban hills volcanic district italy 40ar 39ar geochronology and insights into magma evolution we present 24 40ar 39ar ages for the youngest volcanic products from the alban hills volcanic district rome combined with petrological data on these products we have attempted to define the chronology of the most recent phase of activity and to investigate the magma evolution of this volcanic district the early mainly explosive activity of the alban hills spanned the interval from 561 1 to 351 3 ka after approximately 50 kyr of dormancy a mainly effusive phase of activity took place accompanied by the strombolian activity of a small central edifice monte delle faete this second phase of activity spanned the interval 308 2 to 250 1 ka after another dormancy period of approximately 50 kyr a new hydromagmatic phase of activity started at 200 ka at several centers located to the southwest of the monte delle faete edifice after an initial recurrence period of approximately 50 kyr which also characterized this new phase of activity the longest dormancy period approximately 80 kyr in the history of the volcanic district preceded the start of the activity of the albano and giuturna centers at 70 1 ka results of our study suggest a quasi continuous magmatic activity feeding hydromagmatic centers with a new acme of volcanism since around 70 ka based on data presented in this paper we argue that the alban hills should not be considered an extinct volcanic district and a detailed re assessment of the volcanic hazard for the area of rome is in order

is that a relict rock glacier abstract the distribution of rock glaciers is often used to investigate the occurrence of permafrost in mountain areas and to understand their climate and paleoclimate evolution this requires the creation of regional and global inventories capable of discriminating active and relict landforms in order to forecast the presence or absence of ice in the ground in this paper geomorphological geophysical and microclimatic surveys are performed on a rock glacier of the carnic alps eastern european alps in the classification currently used for implementing regional inventories of permafrost evidence in the alps this rock glacier would be defined as relict however the geophysical climatological and geomorphological results indicate that internal ice is widespread in large portions of the rock glacier these are generally interpreted as ice in pore spaces and local ice lenses probably without layers of massive ice moreover the occurrence of ice during the maximum thawing season at depths

thermal constraints on the early history of the h chondrite parent body reconsidered abstract reconstructions of the early thermal history of the h chondrite parent body have focused on two competing hypotheses the first posits an undisturbed thermal evolution in which the degree of metamorphism increases with depth yielding an onion shell structure the second posits an early fragmentation reassembly event that interrupted this orderly cooling process here we test these hypotheses by collecting a large number of previously published closure age and cooling rate data and comparing them to a suite of numerical models of thermal evolution in an idealized parent body we find that the onion shell hypothesis when applied to a parent body of radius 75 130 km with a thermally insulating regolith is able to explain 20 of the 21 closure age data and 62 of the 71 cooling rates furthermore six of the eight meteorites for which multiple data at different temperatures are available can be accounted for by onion shell thermal histories we therefore conclude that no catastrophic disruption of the h chondrite parent body occurred during its early thermal history the relatively small number of data not explained by the onion shell hypothesis may indicate the formation of impact craters on the parent body which while large enough to excavate all petrologic types were small enough to leave the parent body largely intact impact events fulfilling these requirements would likely have produced transient crater diameters at least 30 of the parent body diameter

strike slip faulting and block rotation a possible triggering mechanism for lava flows in the alban hills abstract it is suggested in this paper that two distinct tectonic triggers tapping different depths of a magma reservoir may be the cause of nearly contemporaneous eruptions of lava flows and ignimbrites in the alban hills the area between the alban hills and rome underwent alternating regional extensional and strike slip faulting during the middle pleistocene the geometries of the main structural dislocations in quaternary strata combined with a statistical analysis of drainage network trends show a structural pattern that is consistent with local strain partitioning in transpressive zones at strike slip fault bends superimposed on regional extension based on this analysis it is suggested that local clockwise block rotation between parallel n s strike slip faults might have generated local crustal decompression allowing relatively volatile free magma to rise from deep reservoirs beneath the alban hills triggering peripheral fissure lava flows in contrast the main ignimbrite eruptions appear to tap shallow volatile rich magma reservoirs and are controlled by extensional processes

brecciation among 2280 ordinary chondrites constraints on the evolution of their parent bodies abstract after accretion of meteorite parent bodies larger and smaller collisions have led to significant modifications of these bodies involved processes include excavation of material thermal metamorphism melting mixing of different materials re accretion and re lithification all these processes can be repeated several times in this study polished thin sections pts of 2280 chondrites 1193 h 947 l and 140 ll chondrites were investigated in order to obtain the abundance of brecciated rocks among the ordinary chondrites in addition we have determined the abundance and characteristics of shock vein bearing h l and ll chondrites and of impact melt rock clasts we also recognized xenolithic components based on o isotope studies noble gas data were considered in order to detect regolith breccias and to discuss late impact histories the investigation of 2280 samples shows that 23 276 of 1193 of the h chondrites 23 220 of 947 of the l chondrites and 79 110 of 140 of the ll chondrites are brecciated considering the heavily brecciated ll chondrites in 63 of the 140 chondrites 45 shock veins were clearly detected 57 of these 63 chondrites are brecciated rocks the investigation of the h and l chondrites has shown that about 26 310 of 1193 of the h chondrites and 40 379 of 947 of the l chondrites contain shock veins in our data set 20 of the h chondrites and 8 3 of the ll chondrites but only 3 0 of the l chondrites contain solar noble gases remarkably about 62 of all brecciated h chondrites with noble gases analyzed contain solar noble gases compared to only around 11 and 10 of the brecciated l and ll chondrites respectively the identification of xenolithic clasts e g ci cm and ureilite like lithologies in primitive type 3 chondrites indicates simultaneous accretion of clasts and chondrules these clasts must have been formed early within the first 2 ma on subsequently destroyed precursor first generation parent bodies the formation of complex breccias witnesses the collisions between asteroids of very different lithologies and heritage although the onion shell configuration of primordial parent bodies is necessary in order to form the chondrites with different degrees of metamorphic overprint petrologic types 3 6 subsequent catastrophic fragmentation and reassembly to form asteroids with a rubble pile structure are required to explain certain features discussed in this work however distinct peaks in the cosmic ray exposure age distributions indicate that not too many impacts in the last 100 ma were responsible to deliver the majority of the ordinary chondritic meteoroids to earth yet this certainly does not tell anything about the number of last generation parent bodies that exist in the asteroid belt since s type asteroids are the most abundant type of asteroid in the inner main belt and thought to be the parent bodies of ordinary chondrites

verification of geophysical models in alpine permafrost using borehole information at two permafrost sites in the swiss alps a range of geophysical methods were applied to model the structure of the subsurface at both sites borehole information was used to verify the quality of the model results on the murtel corvatsch rock glacier 2700 m a s l upper engadine a 58 m deep core drilling was performed in 1987 d c resistivity measurements refraction seismics ground penetrating radar gpr and gravimetric surveys allowed the shape of the permafrost table beneath the marked surface microtopography to be determined and the lateral extent of a deeper shear horizon to be established the validity of each method was verified by the borehole information cores density log and temperature a coherent model of the rock glacier structure was developed at the schilthorn 2970 m a s l bernese oberland it was not clear whether permafrost is in fact present various geophysical surveys d c resistivity tomography refraction seismics gpr and em 31 gave results that were not typical of permafrost environments a 14 m percussion drilling revealed warm permafrost and a very low ice content these geotechnical and geothermal data allowed reinterpretation of the geophysical results improving modelling of ground conditions the paper demonstrates that in the difficult terrain of alpine permafrost boreholes may be critical in calibration and verification of the results of geophysical methods the most useful combinations of geophysical techniques proved to be a seismics with d c resistivity and b gravimetry with gpr

pollen analysis and 14c age of moss remains in a permafrost core recovered from the active rock glacier murtel corvatsch swiss alps geomorphological and glaciological implications within the framework of core drilling through the permafrost of the active rock glacier murtel corvatsch in the swiss alps subfossil stem remains of seven different bryophyte species were found at a depth of 6 m below surface and about 3 m below the permafrost table in samples from massive ice the composition of the moss species points to the former growth of the recovered mosses in the nearest surroundings of the drill site a total of 127 pollen and spores captured by the mosses and representing 23 taxa were determined the local vegetation during deposition time must be characterized as a moss rich alpine grassland meadow rich in cyperaceae poaceae chenopodiaceae and asteraceae comparable to today s flora present around the study site for l4 c analysis accelerator mass spectrometry had to be used due to the small sample mass about 0 5 mg carbon content the mean conventional 14 c age of 2250 100 years 1 variability corresponds to ranges in the calibrated calendar age of 470 170 bc and 800 bc to ad 0 at statistical probabilities of 68 and 95 respectively this result is compared with the present day flow field as determined by high precision photogrammetry and with information about the thickness vertical structure and flow of the permafrost from borehole measurements total age of the rock glacier as a landform is on the order of 10 4 years the development of the rock glacier most probably started around the onset of the holocene when the area it now occupies became definitely deglaciated the bulk of the ice rock mixture within the creeping permafrost must be several thousand years old characteristic average values are estimated for 1 surface velocities through time cm a 1 2 long term ice and sediment accretion rates mm a 1 on the debris cone from which the rock glacier develops 3 retreat rates 1 2 mm a 1 of the cliff which supplies the debris to the debris cone and rock glacier and 4 ice content of the creeping ice rock mixture 50 90 by volume the pronounced supersaturation of the permafrost explains the steady state creep mode of the rock glacier

characteristics and petroleum origin of the carboniferous volcanic rock reservoirs in the shixi bulge of junggar basin western china abstract shixi bulge of the central junggar basin in western china is a unique region that provides insight into the geological and geochemical characteristics of large scale petroleum reservoirs in volcanic rocks of the western central asian orogenic belt carboniferous volcanic rocks in the shixi bulge mainly consist of striped lava and agglomerate as well as breccia lava and tight tuff volcanic rocks differ in porosity and permeability striped lava exhibits the highest porosity average 14 2 but the lowest permeability average 0 67 10 15 m among the rock types primary gas pores are widely developed and mostly filled secondary dissolution pores and fractures are two major reservoir storage spaces capillary pressure curves suggest the existence of four pore structure types of reservoir rocks several factors namely lithology pore structure and various diagenesis govern the physical properties of volcanic rocks the oil is characterized by a high concentration of tricyclic terpane a terpane distribution of c 23 21 c 20 and sterane distributions of c 27 28 29 and c 27 c 28 29 oil and gas geochemistry revealed that the oil is a mixture derived primarily from p 2 w source rock and secondarily from p 1 j source rock in the sag west of pen 1 well the gases are likely gas mixtures of humic and sapropelic organic origins with the sapropelic gas type dominant in the mixture the gas mixture is most likely cracked from kerogen rather than oils the carboniferous volcanic reservoirs in shixi bulge share some unique characteristics that may provide useful insights into the various roles of different volcanic reservoir types in old volcanic provinces the presence of these reservoirs will undoubtedly encourage future petroleum exploration in volcanic rocks up to the deep parts of sedimentary basins

shock metamorphism of planetary silicate rocks and sediments proposal for an updated classification system we reevaluate the systematics and geologic setting of terrestrial lunar martian and asteroidal impactites resulting from single or multiple impacts for impactites derived from silicate rocks and sediments we propose a unified and updated system of progressive shock metamorphism shock metamorphosed rocks occur as lithic clasts or melt particles in proximal impactites at impact craters and rarely in distal impactites they represent a wide range of metamorphism typically ranging from unshocked to shock melted as the degree of shock metamorphism at a given shock pressure depends primarily on the mineralogical composition and the porosity of a rock or sediment sample different shock classification systems are required for different types of planetary rocks and sediments we define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments 1 crystalline rocks with classes f m a and u 2 chondritic rocks class c and 3 sedimentary rocks and sediments with classes sr se and re the abbreviations stand for felsic f mafic m anorthositic a ultramafic u sedimentary rocks sr unconsolidated sediments se and regoliths re in each class the progressive stages of shock metamorphism are denominated s1 to sx these progressive shock stages are introduced as s1 s7 for f s1 s7 for m s1 s6 for a s1 s7 for u s1 s7 for c s1 s7 for sr s1 s5 for se and s1 s6 for re s1 stands for unshocked and sx variable between s5 and s7 stands for whole rock melting we propose a sequence of symbols characterizing the degree of shock metamorphism of a sample i e f s1 to f s7 with the option to add the tabulated pressure ranges in gpa in parentheses

geomorphology internal structure and successive development of a glacier foreland in the semiarid chilean andes cerro tapado upper elqui valley 30 08 s 69 55 w we use geomorphological analysis sedimentological survey remote sensing and ground penetrating radar gpr in order to understand the complex landform assemblage found in front of the cerro tapado glacier in the upper elqui river catchment semiarid andes of chile the geomorphological analysis highlights prominent boundaries dividing the landform assemblage into from the upper part to the lower part an upper latero frontal moraine complex an upper debris covered glacier a lower debris covered glacier two rock glaciers and a lower morainic complex the sedimentological survey highlights the rather small size of the surface debris in general 400 m receding of the glacier occurred along with downslope displacements dm m y 1 of most of the landform units and a significant evolution of the thermokarst features on the debris covered glaciers considerable surface lowering occurred in the upper part of the assemblage while localized bulging is seen along the morphological boundaries in the lower units the gpr profiles highlight spectacular internal structure in the upper debris covered glacier with up to 80 m of buried ice in the other landform units the internal structure is less visible and more heterogeneous the analysis of the radar wave velocity along the gpr profiles reveals the occurrence of air filled and moist zones in the internal structure the geomorphological assemblage is fundamentally characterized by its morphological structural and dynamical boundaries and defined as a young probably 2000 years polygenetic construction with landform units having added to overlapped one another the rock glaciers do not derive from the present debris covered glacier but preexist to it

inflation rate of the colli albani volcanic complex retrieved by the permanent scatterers sar interferometry technique 1 we analyzed 99 ers sar images of the colli albani volcano using the permanent scatterers technique we retrieved the average surface displacement velocities for over 100 000 scatterers for the period 1993 2000 showing that present deformation is concentrated in the area of most recent volcanic activity with rates up to 2 6 mm yr in the satellite line of sight we inverted the observed deformation using several analytical solutions for volcanic sources in an elastic half space the best fit is obtained with two mogi sources aligned in a n s direction at 5 and 7 km depth beneath the western flank of the volcano

the 1989 1990 seismic swarm in the alban hills volcanic area central italy abstract a long seismic swarm has been recorded by a digital microseismic network that the istituto nazionale di geo fisica ing deployed from april 1989 to march 1990 in the alban hills quaternary volcanic region about 20 km southeast of rome the network consisted of thirteen digital stations equipped with four six component weak motion and strong motion sensors three three component and six vertical weak motion seismometers including both broad band and short period sensors more than 3000 earthquakes were detected during about one year of operation the data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the roman age although the temporal distribution of seismicity reveals a volcanic type swarm activity the recorded seismic signals show medium high frequency waveforms and clear s wave arrivals typical of tectonic earthquakes about 1100 earthquakes in a magnitude range between m d 1 5 and md 4 0 have been located the seismicity delineates a 6 12 km 2 nw se elongated region that corresponds to the area where the most recent 0 027 ma phreato magmatic activity took place almost no earthquakes occurred beneath the central cone and the eastern side of the caldera the seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at sligthly different depths 3 5 and 4 6 km the fault plane solutions of the strongest earthquakes reveal a ne sw extension consistent with the regional orientation of the stress field along the apenninic chain as obtained by other seismo logical data

flow and internal structure of a rock glacier exposure of a full transverse cross section of the terminus of fireweed rock glacier wrangell mountains alaska revealed a thin layer of unconsolidated debris mantling a consolidated melange of ice and rock the main rock glacier is fed by three tributaties at the terminus contacts between the three are sharply defined ice content is 50 by volume bubble foliation and crystal morphologies of the ice matrix are similar to those reported from glacier ice folded ice rich strata and lenses foliation planes and the long intermediate axial planes of tabular shaped englacial clasts dip steeply toward the center line of the rock glacier the planar structures generally parallel the steep walls of the gorge containing the trunk stream these steeply dipping longitudinal structures appear to result from transverse compression where the tributaries converge and the trunk stream narrows down valley bergschrund like and moulin like features at the heads of the middle and west tributaries respectively exposed admixed ice and rock similar to that of the terminus but lacking the well developed flow texture talus from the unstable cirque headwall and polygeneticice both accumulate at the base of the headwall and nourrish the tributary rock glaciers

petrogenesis of miller range 07273 a new type of anomalous melt breccia implications for impact effects on the h chondrite asteroid miller range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine grained 3 gpa possibly to 15 19 gpa and temperature 1350 c possibly to 2000 c the higher pressures and temperatures would have involved back reaction of high pressure polymorphs to pyroxene and olivine upon cooling silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration

understanding the seismic velocity structure of campi flegrei caldera italy from the laboratory to the field scale we report laboratory measurements of p and s wave velocities on samples of tuff from campi flegrei italy and a new tomographic velocity map of the campi flegrei caldera laboratory measurements were made in a hydrostatic pressure vessel during both increasing and decreasing effective pressure cycles selected samples were also thermally stressed at temperatures up to 600 c to induce thermal crack damage acoustic emission output was recorded throughout each thermal stressing experiment and velocities were measured after thermal stressing laboratory p and s wave velocities are initially low for the tuff which has an initial porosity of 45 but both increase by between 25 and 50 over the effective pressure range of 5 to 80 mpa corresponding to a decrease of porosity of 70 marked velocity hysteresis due to inelastic damage processes is also observed in samples subjected to a pressurization depressurization cycle tomographic seismic velocity distributions obtained from field recordings are in general agreement with the laboratory measurements integration of the laboratory ultrasonic and seismic tomography data indicates that the tuffs of the campi flegrei caldera can be water or gas saturated and shows that inelastic pore collapse and cracking produced by mechanical and thermal stress can significantly change the velocity properties of campi flegrei tuffs at depth these changes need to be taken into account in accurately interpreting the crustal structure from tomographic data

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

post impact thermal evolution of porous planetesimals abstract impacts between planetesimals have largely been ruled out as a heat source in the early solar system by calculations that show them to be an inefficient heat source and unlikely to cause global heating however the long term localized thermal effects of impacts on planetesimals have never been fully quantified here we simulate a range of impact scenarios between planetesimals to determine the post impact thermal histories of the parent bodies and hence the importance of impact heating in the thermal evolution of planetesimals we find on a local scale that heating material to petrologic type 6 is achievable for a range of impact velocities and initial porosities and impact melting is possible in porous material at a velocity of 4 km s burial of heated impactor material beneath the impact crater is common insulating that material and allowing the parent body to retain the heat for extended periods millions of years cooling rates at 773 k are typically 1 1000 k ma matching a wide range of measurements of metallographic cooling rates from chondritic materials while the heating presented here is localized to the impact site multiple impacts over the lifetime of a parent body are likely to have occurred moreover as most meteorite samples are on the centimeter to meter scale the localized effects of impact heating cannot be ignored

the effect of topography latitude and lithology on rock glacier distribution in the lemhi range central idaho usa abstract statistical analysis of rock glaciers in the lemhi range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology we inspected 171 alpine valleys in the lemhi range using optical remote sensing techniques digital topographic analysis and field examination in those valleys we identified 48 rock glaciers and examined them for lichen cover evidence of ice presence specific evidence of movement and distinctive morphological features in addition to recording the presence or absence of a rock glacier in each alpine valley existing rock glaciers were classified according to their morphology factors such as topographic shading lithology relief aspect and elevation determine the development and preservation of rock glaciers analysis of these factors in the lemhi range shows that elevation 2600 m a north facing aspect 300 60 and multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly whereas duration of insolation is a logical controlling factor latitude is more enigmatic additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range lithology may affect rock glacier distribution through its effects on hydrology or air ventilation moreover statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence suggesting that protalus lobes play a role in the genesis of rock glaciers in the lemhi range separate analysis of the classification systems shows that each morphologic class inferred to correlate with rock glacier activity is statistically significant and distinguishable from other classes in addition to the effect of insolation statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology

shock experiments with the h6 chondrite kernouve pressure calibration of microscopic shock effects shock recovery experiments were carried out on samples of the h6 chondrite kernouve at shock pressures of 10 15 20 25 30 35 45 and 60 gpa and preheating temperatures of 293 k low temperature experiments and 920 k high temperature experiments using a calculated equation of state of kernouve pressure pulse durations of 0 3 to 1 2 s were estimated the shocked samples were investigated by optical microscopy to calibrate the various shock effects in olivine orthopyroxene oligoclase and troilite the following pressure calibration is proposed for silicates 1 undulatory extinction of olivine gpa 2 weak mosaicism of olivine from 10 15 gpa to 20 25 gpa 3 onset of strong mosaicism of olivine at 20 25 gpa 4 transformation of oligoclase to diaplectic glass completed at 25 30 gpa low temperature experiments and at 20 25 gpa high temperature experiments 5 onset of weak mosaicism in orthopyroxene at 30 35 gpa low temperature experiments and at 25 30 gpa high temperature experiments and 6 recrystallization or melting of olivine starting at 45 60 gpa low temperature experiments and at 35 45 gpa high temperature experiments and completed above 45 60 gpa in the high temperature experiments troilite displays distinct differences between the samples shocked at low and high temperatures in the low temperature experiments the following effects can be observed in troilite 1 undulatory extinction up to 25 gpa 2 twinning up to 45 gpa 3 partial recrystallization from 30 to 60 gpa and 4 complete recrystallization 35 gpa whereas in the high temperature experiments troilite shows 1 complete recrystallization from 10 up to 45 gpa and 2 melting and crystallization above 45 gpa localized shock induced melting is observed in samples shocked to pressures 15 gpa in the high temperature experiments and 30 gpa for the low temperature experiments in the form of feni metal and troilite melt injections and intergrowths and as pockets and veins of whole rock melt obviously the onset and abundance of shock induced localized melting strongly depends on the initial temperature of the sample

the geomorphic significance of rock glaciers estimates of rock glacier debris volumes and headwall recession rates in west greenland to obtain knowledge on rockwall retreat rates at sites with rock glaciers an inventory of about 400 individual rock glacier sites in west greenland was carried out by means of field studies and using aerial photographs and topographic maps a number of sites with ice cored moraines beyond normal glaciers were included in the analysis for comparative purposes the estimated debris volume was compared with the size of the source headwall the result of the inventory suggests that the presence of rock glaciers indicates extraordinary high retreat rates for rock free faces above especially headwalls above glacier derived rock glaciers are exposed to high weathering rates and thereby presumably delimit critical ranges regarding altitude for headwall retreat rates the relation of such a critical altitudinal range to other regional concepts such as glaciation level gl and glacier equilibrium line is discussed from this comments are also made on the relation between various permafrost zones and the typical regional climate within the maximum headwall weathering altitude at sites with active rock glaciers finally the potential importance of this range of maximum weathering for understanding the long term evolution of high relief cold climate landscapes is emphasised

looking into a volcanic area an overview on the 350 m scientific drilling at colli albani rome italy abstract a 350 m deep borehole was drilled in the colli albani volcanic district central italy in order to understand the shallow crust structure beneath the volcanic complex characterize the rock physical properties especially through in situ measurements and afterward laboratory experiments assess the local present day stress field install a broad band seismometer at depth the borehole is located adjacent to the western rim of the tuscolano artemisio caldera where several phenomena of unrest recently occurred in 1989 90 a seismic swarm affected this area and a related uplift was recognized in addition high gas concentrations mainly co 2 and h 2 s in aquifers and soils caused illnesses and casualties among inhabitants and animals in the past we describe the investigations carried out at the drill site and the results achieved from data analysis wire line drilling produced a complete stratigraphic record of the quaternary volcanic units down to the plio pleistocene sedimentary sequence and geophysical logs allowed a characterization of the rock physical properties from a tectonic point of view data provided by dipmeter and borehole televiewer were used for investigations on the recent and present day stress field and the results are compared to those available in the literature in the volcanic units we recognized two main fracture systems sw and nw dipping several faults intersecting the borehole show planes with oblique striae indicating a prevalent strike slip component of the movement finally borehole breakout analysis defined an active stress field with a e w oriented minimum horizontal component at the end of the drilling a blow out occurred due to pressurized fluids trapped into the sandy unit drilled in the last few meters of the hole sampling these fluids gave an additional value to the borehole providing information about the deep volcanic circulation and its possible connection to a deep seated magma chamber the main results show water with a na hco 3 chemistry and the highest salinity ever recognised in the area electrical conductivity 10 12 ms cm stable o and h isotopes reveal a meteoric origin of water and the absence of tritium points out a long residence time in the aquifer emitted gas is co 2 dominated with n 2 as second most important component helium isotopic composition of the gas allows us to estimate a magmatic component ranging in the interval 40 50 one of the highest in the colli albani carbon isotopes of co 2 0 53 vs pdb suggest that it could derive partly from a magmatic source and partly by the thermal decarbonation of the carbonatic basement

morphology and the role of landsliding in formation of some rock glaciers in the mosquito range colorado some 23 rock glaciers have been identified in the central portion of the mosquito range surface features and characteristic forms correlate well with those reported for rock glaciers in alaska and elsewhere in colorado new mexico and utah on the basis of air photo interpretation about two thirds of the rock glaciers are lobate in form and one third are tongue shaped only 5 of the 23 rock glaciers are believed to be active a detailed stability analysis of two rock glaciers in iowa gulch indicates that landsliding of unstable morainal deposits played a major role in their formation landslide debris provided loading necessary to initiate ice creep in frozen till on the lower valley slopes ice creep continued eventually bringing the rock glaciers to their present form with the supply of landslide debris exhausted and with insufficient ice wedging and rock exposure to generate large talus cones stresses generated by the superincumbent load were reduced by creep induced spreading and motion ceased internal ice in the form of both interstitial ice and ice layers still remains techniques developed to evaluate activity of rock glaciers in alaska have been applied to the two rock glaciers in iowa gulch these techniques based principally on steepness and form of the rock glacier front as well as on calculated values of basal shear stress indicate both rock glaciers to be inactive re survey of a mining claim corner and inspection of a shaft show that no movement has occurred over the period of record and that the rock glaciers are indeed inactive substantiating the usefulness and validity of the above described techniques for assessment of rock glacier activity elsewhere

studies of an artificially shock loaded h group chondrite five samples of the naturally unshocked kernouve h6 meteorite were artificially shock loaded to pressures of 70 165 270 and 390 kbar and the silicates and metal examined optically by scanning and transmission electron microscopy and by thermoluminescence tl olivine deformation is closely comparable to that in naturally shocked meteorites producing dislocations with burgers vector 001 at pressures of 165 kbar these are formed in well defined slip planes at 270 kbar olivine develops optical mosaicism has high dislocation densities throughout and is also highly fractured recovery due to heating is minimal in orthopyroxene the deformation mechanism changes from the clino inversion to unit dislocation slip between 70 and 165 kbar in diopside 001 and 100 twinning was produced plagioclase is inferred to have been progressively converted to maskelynite but some is still present in 270 kbar sample the microhardness of the kamacite in the samples increases with shock pressure the transformation pressure in the kamacite is 30 40 kbar higher than observed for iron meteorites annealed kamacite displays incipient polycrystallinity and martensite and taenite sometimes contains slip lines troilite acquired cracks undulose extinction twins polycrystallinity and finally melted as the shock pressure increased at pressures over 200 kbar there was a systematic decrease in the natural tl and the tl sensitivity detailed considerations of changes in the natural tltl sensitivity ratio for various regions of the tl glow curve suggest that two processes were effective during shock thermal drainage of electron traps and a reduction in the effective trap density it is suggested that the latter process associated with the vitrification of feldspar the tl phosphor an additional sample was subjected to a shock pulse which was spiked instead of square very distinctive changes were apparent thermal effects are conspicuous and with widespread annealing 600 800 c of metal and sulfide glassy opaque veins were produced which are analogous to the black veins in shock lithified gas rich meteorites anomalous low temperature tl was induced suggesting that a new or modified phase or mineral has become the dominant tl phosphor

the significance of rock glaciers in the glacial periglacial landscape continuum rock glaciers are distinct landforms whose wide distribution occurrence and significance often go unrecognised they are deposits of poorly sorted angular blocky to tabular debris which are held together by an ice core or a matrix of ice cemented fine clastics rock glaciers have formed in glaciated and non glaciated areas many researchers have suggested that the absence of an ice core or the lack of movement indicates relict or fossil status active and inactive states can be viewed as the end members of a movement continuum movement rates derived from world wide locations as reported in the literature range from less than 1 cmyr 1 to greater than 130cmyr 1 unfortunately lack of observed movement has been equated incorrectly with an inactive status rock glacier movement must be considered from a rheological point of view movement is controlled by the transformation of potential energy to kinetic energy as the system attempts to reach thermal equilibrium or stability whereas a glacier can completely disappear or redevelop reactivation of a rock glacier requires only the re establishment of the conditions responsible for development and maintenance of interstitial ice although it might not be possible to re establish an ice core interstitial areas can definitely be recharged with ice and thus facilitate movement the concept of active versus inactive should be abandoned in favor of the view that a spatial and temporal continuum of form and movement exists

noble gas retention chronologies for the st severin meteorite abstract 40 ar 39 ar and 129 xe 128 xe analyses were performed on two lithologies light and dark of the st severin ll6 chondrite for the light and dark fractions respectively we obtained 40 ar retention ages of 4 38 and 4 42 ae and 129 xe retention ages of 8 4 and 15 2 myr after bjurbole the two methods give age differences of opposite sense and by both methods the differences are significant both the 40 ar and the 129 xe ages are interpreted as dating relaxation of metamorphic conditions these two chronometers are decoupled however and do not date the same events 40 ar 39 ar reflect chondritic metamorphisrn on a 10 8 yr time scale the 129 xe 128 xe ages reflect isotopic closure at higher temperatures and earlier times

three dimensional velocity structure and earthquake relocation in the alban hills volcano central italy abstract the alban hills is a quaternary volcano located along the tyrrhenian margin of the apennines central italy which has erupted from 0 7 to 0 027 ma the high density of population around the volcano as well as the proximity to rome 20 km spurred us to investigate the three dimensional 3d crustal structure beneath the volcano with particular emphasis to the identification of volcano related phenomena hydrothermal circulation and frequent seismic activity characterize the present state of the volcano a seismic swarm from april 1989 to march 1990 consisted of shallow seismicity depths less than 6 km located beneath the western side of the volcano where the phreatomagmatic eruptions 0 03 ma occurred in this paper we present new results obtained from seismic tomography using the recorded local earthquakes we imaged the earthquake distribution jointly with the 3d velocity structure by inverting 1314 p and 1185 s arrival times from 163 selected events using the method developed by thurber 1983 we progressively focused toward the well sampled crustal volume decreasing the model gridspacing in subsequent inversion detailed resolution analysis and comparison with results of a synthetic test ensure that the computed models are reliable at least in the volume where the ray coverage is sufficient the calculated model improves the hypocentral locations of the 1989 1990 earthquakes allowing us to visualize the structures that generated the seismic swarm the relocated earthquakes are confined between 3 and 6 km in depth and they surround a body with anomalously high p wave velocity that is probably uplifted and metamorphosed carbonate rocks

radon and thoron emission from lithophysae rich tuff under increasing deformation an experimental study 1 radon and thoron emissions from lithophysae rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring two samples are uniaxially loaded up to failure while two others are unloaded at the end of the elastic phase in order to achieve the highest compaction of existing pores changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique results show that tuff samples are characterised by a dual porosity consisting of a macroporosity given by isolated large pores with sizes from mm up to cm scale and a microporosity ranging between microns to hundreds of microns at the end of the elastic phase pervasive pore collapse is observed due to the closure of the cm scale macropores this is mirrored by a significant decrease of radon and thoron release after failure a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores at this stage radon and thoron emissions increase the formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations strongly prevailing over the densification carried out from the compaction mechanisms in terms of volcanic hazard negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures key words radon and thoron exhalation tuff deformation seismic precursor

postshock annealing and postannealing shock in equilibrated ordinary chondrites implications for the thermal and shock histories of chondritic asteroids abstract in addition to shock effects in olivine plagioclase orthopyroxene and ca pyroxene petrographic shock indicators in equilibrated ordinary chondrites oc include chromite veinlets chromite plagioclase assemblages polycrystalline troilite metallic cu irregularly shaped troilite grains within metallic fe ni rapidly solidified metal sulfide intergrowths martensite and various types of plessite metal sulfide veins large metal and or sulfide nodules silicate melt veins silicate darkening low ca clinopyroxene silicate melt pockets and large regions of silicate melt the presence of some of these indicators in every petrologic type 4 to 6 ordinary chondrite demonstrates that collisional events caused all equilibrated oc to reach shock stages s3 s6 those type 4 to 6 oc that are classified as shock stage s1 on the basis of sharp optical extinction in olivine underwent postshock annealing due to burial beneath materials heated by the impact event those type 4 to 6 oc that are classified s2 on the basis of undulose extinction and lack of planar fractures in olivine were shocked to stage s3 s6 annealed to stage s1 and then shocked again to stage s2 some oc were probably shocked to stage s3 after annealing it seems likely that many oc experienced multiple episodes of shock and annealing because 40ar 39ar chronological data indicate that mil 99301 ll6 s1 was annealed 4 26 ga ago presumably as a consequence of a major impact it seems reasonable to suggest that other equilibrated s1 and s2 oc which contain relict shock features were also annealed by impacts because some type 6 s1 oc e g guarena kernouve portales valley all of which contain relict shock features were annealed 4 44 4 45 ga ago during a period when impacts were prevalent and most oc were thermally metamorphosed it follows that impact induced annealing could have contributed significantly to oc thermal metamorphism

relationships among physical properties as indicators of high temperature deformation or post shock thermal annealing in ordinary chondrites collisions and attendant shock compaction must have been important for the accretion and lithification of planetesimals including the parent bodies of chondrites but the conditions under which these occurred are not well constrained a simple model for the compaction of chondrites predicts that shock intensity as recorded by shock stage should be related to porosity and grain fabric to test this model we studied sixteen ordinary chondrites of different groups h l ll using x ray computed microtomography ct to measure porosity and metal fabric ideal gas pycnometry and 3d laser scanning to determine porosity and optical microscopy om to determine shock stage these included a subsample of six chondrites previously studied using transmission electron microscopy tem to characterize microstructures in olivine combining with previous data results support the simple model in general but not for chondrites with low shock porosity foliation low spf chondrites these include kernouve h6 portales valley h6 7 butsura h6 park l6 gro 85209 l6 estacado h6 mil 99301 ll6 spade h6 and queen s mercy h6 among others the data for these meteorites are best explained by high ambient heat during or after shock low spf chondrites tend to have older 40ar 39ar ages 4435 4526 ma than other non low spf type 6 chondrites in this study we conclude that the h l and ll asteroids all were shock compacted at an early stage while warm with collisions occurring during metamorphic heating of the parent bodies results ultimately bear on whether chondrite parent bodies have internal structures more akin to a metamorphosed onion shell or metamorphosed rubble pile and on the nature of accretion and lithification processes for planetesimals

thermal and impact history of the h chondrite parent asteroid during metamorphism constraints from metallic fe ni abstract we have studied cloudy taenite metallographic cooling rates and shock effects in 30 h3 6 chondrites to elucidate the thermal and early impact history of the h chondrite parent body we focused on h chondrites with old ar ar ages 4 4 gyr and unshocked and mildly shocked h chondrites as strongly shocked chondrites with such old ages are very rare cooling rates for most h chondrites at 500 c are 10 50 c myr and do not decrease systematically with increasing petrologic type as predicted by the onion shell model in which types 3 5 are arranged in concentric layers around a type 6 core some type 4 chondrites cooled slower than some type 6 chondrites and type 3 chondrites did not cool faster than other types contrary to the onion shell model cloudy taenite particle sizes which range from 40 to 120 nm are inversely correlated with metallographic cooling rates and show that the latter were not compromised by shock heating the three h4 chondrites that were used to develop the onion shell model ste marguerite beaver creek and forest vale cooled through 500 c at 5000 c myr our thermal modeling shows that these rates are 50 higher than could be achieved in a body that was heated by 26al and cooled without disturbance by impact published ar ar ages do not decrease systematically with increasing petrologic type but do correlate inversely with cloudy taenite particle size suggesting that impact mixing decreased during metamorphism metal and silicate compositions in regolith breccias show that impacts mixed material after metamorphism without causing significant heating impacts during metamorphism created portales valley and two other h6 chondrites with large metallic veins excavated the fast cooled h4 chondrites around 3 4 myr after accretion and mixed petrologic types metallographic data do not require catastrophic disruption by impact during cooling

deformation and thermal histories of ordinary chondrites evidence for post deformation annealing and syn metamorphic shock abstract we show that olivine microstructures in seven metamorphosed ordinary chondrites of different groups studied with optical and transmission electron microscopy can be used to evaluate the post deformation cooling setting of the meteorites and to discriminate between collisions affecting cold and warm parent bodies the l6 chondrites park shock stage s1 bruderheim s4 leedey s4 and morrow county s5 were affected by variable shock deformation followed by relatively rapid cooling and probably cooled as fragments liberated by impact in near surface settings in contrast kernouve h6 s1 portales valley h6 7 s1 and mil 99301 ll6 s1 appear to have cooled slowly after shock probably by deep burial in warm materials in these chondrites post deformation annealing lowered apparent optical strain levels in olivine additionally kernouve morrow county park mil 99301 and possibly portales valley show evidence for having been deformed at an elevated temperature 800 1000 c the high temperatures for morrow county can be explained by dynamic heating during intense shock but kernouve park and mil 99301 were probably shocked while the h l and ll parent bodies were warm during early endogenically driven thermal metamorphism thus whereas the s4 and s5 chondrites experienced purely shock induced heating and cooling all the s1 chondrites examined show evidence for static heating consistent with either syn metamorphic shock kernouve mil 99301 park post deformation burial in warm materials kernouve mil 99301 portales valley or both the results show the pitfalls in relying on optical shock classification alone to infer an absence of shock and to construct cooling stratigraphy models for parent bodies moreover they provide support for the idea that secondary metamorphic and tertiary shock processes overlapped in time shortly after the accretion of chondritic planetesimals and that impacts into warm asteroidal bodies were common

ancient porosity preserved in ordinary chondrites examining shock and compaction on young asteroids we use a combination of 2d and 3d petrographic examination and 40ar 39ar analyses to examine the impact histories of a suite of seven ordinary chondrites baszkowka miller nwa 2380 mount tazerzait sahara 98034 tjerebon and mil 99301 that partially preserve their ancient but postaccretionary porosity ranging from 10 to 20 we examine whether materials that seem to be only mildly processed as their large intergranular pore spaces suggest may have more complex shock histories the ages determined for most of the seven ocs studied here indicate closure of the 40ar 39ar system after primary accretion but during baszkowka or shortly after others thermal metamorphism with little subsequent heating exceptions include sahara 98034 and mil 99301 which were heated to some degree at later stages but retain some evidence for the timing of thermal metamorphism in the 40ar 39ar system although each of these chondrites has olivine grains with sharp optical extinction signaling an apparent shock stage of s1 normally indicative of an extremely mild impact history all of the samples contain relict shock indicators given the high porosity and relatively low degree of compaction coupled with signs of shock and thermal annealing it seems plausible that impacts into materials that were already hot may have produced the relict shock indicators initial heating could have resulted from prior collisions the decay of 26al or both processes

volcanic settings and their reservoir potential an outcrop analog study on the miocene tepoztlan formation central mexico abstract the reservoir potential of volcanic and associated sedimentary rocks is less documented in regard to groundwater resources and oil and gas storage compared to siliciclastic and carbonate systems outcrop analog studies within a volcanic setting enable to identify spatio temporal architectural elements and geometric features of different rock units and their petrophysical properties such as porosity and permeability which are important information for reservoir characterization despite the wide distribution of volcanic rocks in mexico their reservoir potential has been little studied in the past in the valley of mexico situated 4000 m above the neogene volcanic rocks groundwater is a matter of major importance as more than 20 million people and 42 of the industrial capacity of the mexican nation depend on it for most of their water supply here we present porosity and permeability data of 108 rock samples representing five different lithofacies types of the miocene tepoztlan formation this 800 m thick formation mainly consists of pyroclastic rocks mass flow and fluvial deposits and is part of the southern transmexican volcanic belt cropping out south of the valley of mexico and within the two states of morelos and mexico state porosities range from 1 4 to 56 7 average porosity is 24 8 generally permeabilities are low to median 0 2 933 3 md with an average permeability of 88 5 md the lavas are characterized by the highest porosity values followed by tuffs conglomerates sandstones and tuffaceous breccias on the contrary the highest permeabilities can be found in the conglomerates followed by tuffs tuffaceous breccias sandstones and lavas the knowledge of these petrophysical rock properties provides important information on the reservoir potential of volcanic settings to be integrated to 3d subsurface models

evidence of active tectonics on a roman aqueduct system ii iii century a d near rome italy abstract in this paper we describe evidence of strong tectonic deformation affecting two aqueducts of roman age ii iii century a d the channels are located approximately 20 km northeast of rome along the ancient via tiburtina brittle and ductile deformation affects these two structures including extensional joint systems ne oriented faults and horizontal distortion this deformation is consistent with right lateral movement on major n striking faults and represents the first evidence that tectonic deformation took place in historical times in the vicinity of rome with local strike slip movement superimposed on a regional extensional fault system

mesoscale and microscale shock effects in the ll6 s4 chondrites saint severin and elbert a tale of two breccias

recent terrestrial and satellite observations to model deformations at colli albani volcano central italy the colli albani volcanic complex rome italy has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the albano maar phase 70 ka earthquakes of moderate intensity gas emissions and significant ground deformations are the recent evidences of a residual activity former geodetic data from leveling surveys gps stations and insar observations tracked ongoing significant uplift of the order of few mm year near the colli albani western flank different uplift rates were detected by each technique in different time spans suggesting also the possibility of sporadic recharge of the hydrothermal system the renewed high precision leveling data from igmi survey carried out in 1997 1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of 3 mm year radar interferograms from alos satellite show uplift rate of 6 mm year southwest of the central sector of the leveling route we have undertaken a joint inversion of the various geodetic data vertical rates from leveling surveys gps site velocities and insar observations acquired by alos satellite using a nonlinear inversion technique to estimate the parameters of a point pressure source possibly capable of explaining the ongoing deformation at colli albani volcano

rock glaciers and the geomorphological evolution of deglacierizing mountains abstract rock glaciers are an important geomorphic element of glaciated mountain landscapes but our understanding of their distribution and ages controls on their development and their importance in regional mountain hydrology and mountain geomorphic evolution is incomplete in part this incomplete knowledge arises through problems associated with identifying rock glaciers on a morphological basis alone amplified by the multiple ways in which rock glaciers can form in different glacial periglacial and paraglacial settings this study focuses on rock glaciers as a paraglacial mountain landscape element and considers the relationships between rock glaciers and glacial periglacial and paraglacial processes new geomorphic and sedimentary data on different rock glaciers from the khumbu region of nepal are presented these data show that even within a single region rock glaciers may have varied origins and thus likely ages and different climatic and environmental controls we argue that rock glaciers in deglacierizing mountains may have a long residence time in the landscape unlike many other glacially influenced mountain landforms and can undergo significant morphodynamic changes as glaciated landscapes transition into paraglacial landscapes

spade an h chondrite impact melt breccia that experienced post shock annealing the low modal abundances of relict chondrules 1 8 vol and of coarse i e 200 m size isolated mafic silicate grains 1 8 vol in spade relative to mean h6 chondrites 11 4 and 9 8 vol respectively show spade to be a rock that has experienced a significant degree of melting various petrographic features e g chromite plagioclase assemblages chromite veinlets silicate darkening indicate that melting was caused by shock plagioclase was melted during the shock event and flowed so that it partially to completely surrounded nearby mafic silicate grains during crystallization plagioclase developed igneous zoning low ca pyroxene that crystallized from the melt or equilibrated with the melt at high temperatures acquired relatively high amounts of cao metallic fe ni cooled rapidly below the fe ni solvus and transformed into martensite subsequent reheating of the rock caused transformation of martensite into abundant duplex plessite ambiguities exist in the shock stage assignment of spade the extensive silicate darkening the occurrence of chromite plagioclase assemblages and the impact melted characteristics of spade are consistent with shock stage s6 low shock stage s2 is indicated by the undulose extinction and lack of planar fractures in olivine this suggests that spade reached a maximum prior shock level equivalent to stage s6 and then experienced post shock annealing probably to stage s1 these events were followed by a less intense impact that produced the undulose extinction in the olivine characteristic of shock stage s2 annealing could have occurred if spade were emplaced near impact melts beneath the crater floor or deposited in close proximity to hot debris within an ejecta blanket spade firmly establishes the case for post shock annealing this may have been a common process on oc asteroids

the history of the monti sabatini and alban hills volcanoes groundwork for assessing volcanic tectonic hazards for rome abstract the volcanic rocks of rome provide chronostratigraphic constraint that is of use to geologists archaeologists and paleontologists identifying the areal distribution of these rocks their mode of emplacement and a detailed chronology of the eruptive events also is crucial for assessing local natural hazards in a volcanic tectonic context and for recognizing whether the volcanoes may erupt again in the future we have identified and dated many of the volumetrically significant eruptive units from the monti sabatini and alban hills colli albani and propose a formalized volcanic stratigraphy for rome it is probable that seismic events triggered some eruptions as several ignimbrites from the two volcanoes have statistically indistinguishable ages following a 200 kyr period of dormancy that was coincident with a pulse of regional uplift the alban hills appears to have begun recently circa 45 ka a new eruptive cycle therefore accurate assessment of volcanic tectonic hazards and estimation of possible future volcanic activity is necessary for the safety of the five million people living near these volcanoes

shock and thermal history of northwest africa 4859 an annealed impact melt breccia of ll chondrite parentage containing unusual igneous features and pentlandite abstract northwest africa 4859 nwa 4859 is a meteorite of ll chondrite parentage that shows unusual igneous features and contains widely distributed pentlandite the most obvious unusual feature is a high proportion of large 3 cm diameter igneous textured enclaves lites interpreted as shock melts that were intruded into an ll chondrite host one such lite appears to have been produced by whole rock melting of ll chondrite initial rapid partial crystallization and subsequent slow cooling of the residual melt in the host to produce a differentiated object other unusual features include mm sized overgrowth objects fine grained plagioclase rich bands and coarse troilite 7 mm across grains all these features are interpreted as having crystallized from melts produced by a single transient shock event followed by slow cooling a subsequent shock event of moderate s3 intensity produced veining and transformed some of the pyroxene into the clinoenstatite polytype pentlandite together with associated troilite in nwa 4859 probably formed by the breakdown of a monosulfide precursor phase at low temperature 230 c following the second shock event nwa 4859 is interpreted to be an unusual impact melt breccia that contains shock melt which crystallized in different forms at depth within the parent body

mid distal occurrences of the albano maar pyroclastic deposits and their relevance for reassessing the eruptive scenarios of the most recent activity at the colli albani volcanic district central italy abstract the late pleistocene albano maar hosted the most recent volcanic activity of the colli albani volcanic district represented at near vent sections by a thick pyroclastic succession of seven units clustered in two main eruptive cycles dated at around 70 68 and 41 36 ka b p respectively recent stratigraphic investigations allowed us to recognise a pyroclastic succession comprising four eruptive units widely spread in the northeastern sectors of the colli albani volcano up to 15 km eastward from the albano maar integrated tephrostratigraphic morpho pedostratigraphic archaeological petrological and geochemical analyses enable us to recognise them as distal deposits of the first third fifth and seventh albano maar eruptions enlarging significantly their previously supposed dispersion area further tephrostratigraphic studies in central apennine area allowed us to identify the albano maar products in late pleistocene deposits of several intermountain basins extending still further the dispersion area of distal ash fallout as far as 100 120 km from the vent on the basis of the identification and the study of these previously unrecognised mid distal albano maar deposits a reappraisal of the eruptive scenarios and related energetic parameters is proposed

engineering geomorphology of rock glaciers a partnership between geomorphology and engineering is facilitating human development in this harsh environment rock glaciers provide locations for urban water sources construction borrow sources drill sites shaft and tunnel portals ski tower supports and dam abutments rock glaciers as dynamic landforms necessitate proper identification in the field placing structures on in or adjacent to rock glaciers requires an appreciation and understanding of their temporal stability internal and surface characteristics provide important clues to the development and deformation of rock glaciers rock glaciers play a significant role in the alpine debris transport system active movement and mass wasting are perhaps the most obvious geologic hazards affecting engineered works the structure of the rock glacier is conducive to the production of a steady continuous supply of meltwater during summer months thus rock glaciers serve as alpine aquifers consideration of rock glaciers as potential aquifer sources requires caution because of the long term impact of climate change on the temporal nature of the landform from the rock glaciers that we have monitored for water quality characteristics it appears that they provide quality potable water this paper provides a foundation for appreciation and understanding of rock glaciers from an engineering geomorphologic point of view the approach taken in this paper provides practical important information to aid the engineer and engineering geologist in prudent evaluations of rock glaciers as potential sites for human development and uses the bottom line of our paper is rock glaciers must be avoided for essentially all structures

rock glacier dynamics in marginal periglacial environments vertical electric sounding bottom temperature of winter snowcover bts and ground thermal measurement debris surface analysis and a differential global positioning system dgps survey were performed on the posets rock glacier pyrenees between 2001 and 2008 high precision records of horizontal and vertical movements of the rock glacier were measured using a dgps on ten steel rods total and annual average displacements and thickness changes for each control point were derived from the field survey horizontal and vertical displacement rates in different sectors of the rock glacier were compared and these compared with thermal structural and morphological maps the inferred surface deformation was characterized by extensional and compressive flows in which two dynamic types were found the first type of movement is defined by the slide and flows related to the existence of an ice body over the frost body the second dynamic type involved the displacement generated by deformation of the frozen body the study attempts to understand the surface movement and dynamics of rock glaciers in marginal cold environments and their usefulness as environmental geoindicators copyright 2010 john wiley sons ltd

shock metamorphism of carbonaceous chondrites abstract we have studied shock effects in carbonaceous chondrites using optical microscopy of thin sections and find that our petrographic classification of progressive shock metamorphism in ordinary chondrites can also be applied to carbonaceous chondrites we find that sixty nine carbonaceous chondrites can be assigned to four shock stages si to s4 largely on the basis of shock effects in olivine the least shocked chondrite groups are cm2 and co3 thirty six out of thirty eight members are classified as shock stage s1 differences between the mean shock levels of certain groups of chondrites e g co3 and cv3 are probably due to stochastic differences in the sampling of their parent bodies however there is an overall tendency for the mean shock level of carbonaceous chondrites and ordinary chondrites to increase with increasing petrologic type that may reflect real differences in the shock level of near surface materials on their parent bodies caused by intrinsic variations in the chemical and physical properties of these materials petrologic type 2 and 3 chondrites are more porous and richer in volatiles than types 4 to 6 the greater porosity of types 2 3 causes higher post shock temperatures and melting at lower pressures and the higher volatile contents ensure that strongly shocked material is more readily dispersed on release from high pressure we suggest that type 2 3 material shocked above 20 30 gpa normally escapes from the parent asteroids and forms particles that are too small to survive as meteorites in the cv3 group there is a correlation between the degree of chondrule flattening and the intensity of shock metamorphism analogous to that discovered in ordinary chondrites by sneyd et al 1988 suggesting that shock rather than static overburden pressure is responsible for chondrule flattening we infer that the correlations are due to collapse of pores under shock pressures of at least 5 10 gpa and that shock is an important process affecting many physical properties of type 2 4 chondrites

the nature and dynamics of frozen ground in alpine and subarctic periglacial environments a spatial assessment of the complex discontinuous and sporadic permafrost distribution and characteristics in high altitude alpine and high latitude subarctic permafrost environments was achieved u

recent uplift of the alban hills volcano italy evidence for magmatic inflation first order leveling surveyed in 1951 and 1994 along a line across the alban hills volcano reveals maximum vertical uplift of 30 cm average of 7 mm yr in the region of geologically recent 0 020 0 030 ma explosive activity the uplifted region corresponds to an area where seismic activity is concentrated at depths of 3 6 km uplift exceeding 10 cm is observed over a 14 km wide zone in the center of a 40 km long line with the deformation tapering to zero at both ends of the line data from a few sparse older benchmarks measured in 1891 and 1927 suggest that the deformation in the first half of this century was very small compared to the period 1951 1994 the observed uplift together with increased seismic activity suggest that recent magma injection has occurred in the upper crust beneath the alban hills volcano

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

relating pore fabric geometry to acoustic and permeability anisotropy in crab orchard sandstone a laboratory study using magnetic ferrofluid pore fabric anisotropy is a common feature of many sedimentary rocks in this paper we report results from a comparative study on the anisotropy of a porous sandstone crab orchard using anisotropy of magnetic susceptibility ams acoustic wave velocity and fluid permeability techniques initially we characterise the anisotropic pore fabric geometry by impregnating the sandstone with magnetic ferro fluid and measuring its ams the results are used to guide subsequent measurements of the anisotropy of acoustic wave velocity and fluid permeability these three independent measures of anisotropy are then directly compared results show strong positive correlation between the principal directions given from the ams velocity anisotropy and permeability anisotropy permeability parallel to the macroscopic crossbedding observed in the sandstone is 240 higher than that normal to it p and s wave velocity anisotropy and ams show mean values of 19 1 4 8 and 3 8 respectively reflecting the disparate physical properties measured

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

application of refraction seismics in alpine permafrost studies a review abstract refraction seismics is a common geophysical application to investigate permafrost in alpine studies this study reviews the physical basis of the use of refractions seismics and introduces the history of its application in alpine environments seismic properties are influenced by rock or soil properties and fluid or ice effects in laboratory measurements these influences are determined and linked to mechanical properties or used for calibration of field studies in field conditions supplementary environmental factors influence the seismic properties of landforms in this paper laboratory studies of rocks from different lithologies and with different properties as well as case studies on rock glaciers moraines talus slopes and debris covered slopes are collected and influencing factors quantitatively analyzed the data demonstrate how lithology porosity and anisotropy influence p wave velocity environmental factors result in a high variation of p wave velocities in landforms however p wave velocities enable the differentiation of active layer and permafrost in rock glaciers and moraines in talus slopes and debris covered slopes p wave velocity contrasts between active layer and permafrost layer might be insufficient and require the application of additional methods for a final differentiation

laboratory measurements of ultrasonic wave velocities in rocks from the campi flegrei volcanic system and their relation to other field data the campi flegrei caldera located near the city of naples italy has shown signs of unrest characterized by large ground deformation seismic activity and changes in the hydrothermal system since 1970 any attempt to model the processes giving rise to these phenomena requires some knowledge of the subsurface structure and of the physical properties of the rocks at depth in this study we report the results of laboratory measurements of ultrasonic compressional and shear wave velocities in rock samples cored in 4 different geothermal wells reaching a maximun depth of 3 km the wells are located in the san vito sv and mofete mf areas at about 3 km north and 4 km west respectively from the center of the caldera we selected 10 core samples 7 from the sv wells and 3 from the mf wells the attention being focused on the most important rock formations underneath campi flegrei and on the lower sections of the wells where data had been lacking the measurements involved the transmission of ultrasonic waves along three orthogonal directions through dry and water saturated rocks at room conditions the samples are only moderately anisotropic 13 for one sv sample and 8 for all the other samples wave velocities generally increase with the depth of the sample the range of velocities is 3 5 4 km s 1 for p waves and 1 5 2 9 km s 1 for s waves for the sv samples water saturation generally implies slightly larger 10 vp values and smaller 20 vs values as compared with dry velocities for the mf samples water saturation implies both higher vp and vs velocities up to 35 and 18 respectively these results may be explained by the different type of porosity of the sv samples vesicular and the mf samples fissurai the ultrasonic measurements on water saturated samples are slightly higher than the available in situ vp sonic measurements 25 for one sv sample and 15 for all the other samples these differences can be explained by velocity dispersion between ultrasonic and sonic frequencies and by the different pressure temperature conditions existing at depth

low magnitude earthquakes in rome structural interpretation and implications for the local stress field on 1995 june 12 a ml 3 6 earthquake occurred in the cecchignola area of southern rome a detailed structural investigation of this area and an analysis of macroseismic and instrumental data indicate a seismogenic area for the local low magnitude seismicity that affects the city of rome a peripheral volcanic field in cecchignola shows that the local seismicity could be related to the same volcanotectonics that affects the colli albani alban hills region fracture field emission is proposed for the emplacement of about 2 5 km3 of lava which developed a small plateau that was subsequently intruded by the feeder dyke of a large ignimbrite the geometry of this dyke as well as the faults disrupting the lava field indicates ne sw extension younger tectonic features show a nw striking 3 in the studied area suggesting that dextral n s strike slip displacement generated structures that are not compatible with the local present day stress field characterized by a ne striking 3 an analysis of focal solutions and the spatial distribution of the 1995 june 12 microearthquake sequence suggests an e w seismogenic structure whose trend is atypical of the structural setting of the area the present study identifies surface faulting with the same trend as the focal mechanisms in the epicentral area and suggests that these faults represent an inactive surface expression of the deeper structures it is also suggested that these structures originated during a different tectonic regime and are presently reactivated at depth by the ne sw extension the general ne orientation of the t axes from focal mechanisms for the colli albani earthquakes and for the 1995 june 12 cecchignola event strongly supports a regional interpretation for the present day stress field previously observed only in the colli albani area it is likely that a combination of different tectonic styles during the last 600 kyr is necessary to explain the structural features of the cecchignola area and of the central tyrrhenian sea margin of italy in general

pebbly versus bouldery rock glaciers morphology structure and processes abstract differences in rockwall geology cause two types of rock glaciers a bouldery rock glacier having the active layer composed of matrix free boulders derived from crystalline rocks and massive limestone and a pebbly rock glacier consisting of matrix supported debris derived from less resistant shale and platy limestone such material composition controls transport processes responsible for the shape size and internal structure of the two types of rock glaciers this paper compares the major processes controlling the morphology and structure of the two types in the swiss alps based on mapping description of geological and morphological characteristics direct observation of stratigraphy and geophysical soundings of internal structure in the swiss alps pebbly rock glaciers are distinguished from bouldery rock glaciers by the clast size of 15 20 cm in the mean b axis diameter the former are fed by small scale rockfalls debris flows and solifluction whereas the latter mainly originate from large rockfalls pebbly rock glaciers are generally smaller 100 k m in bouldery rock glaciers appears to originate from snow banks buried with deposits of large rockfalls from the large source rockwall

topographic lithologic and glaciation style influences on paraglacial processes in the upper sil and luna catchments cantabrian mountains nw spain abstract deglaciated mountainous areas are usually affected by a great range of paraglacial processes that involve progressively denudation of glacial imprints this study focuses on paraglacial processes and glacial landform preservation in six zones located in two catchments of the cantabrian mountains nw spain these zones are adjacent but display important topographic lithologic and glaciation style differences an analysis of how these variables conditioned the intensity and diversity of paraglacial processes in these zones was investigated through a detailed study of their relief lithology and paleo glacier surface using gis a comprehensive cartography of paraglacial landforms was also accomplished considering landslides alluvial fans and rock glaciers that show signs of having been conditioned by glaciation moraines and debris mantled slopes were also included in the analysis to examine their grade of preservation depending on the studied variables data comparison show that differences in glaciation style influenced paraglacial processes in the ancient icefield area relief modification by glacial action was limited and scarce paraglacial processes occur by contrast in the upper areas located in the southern ranges where an alpine style of glaciation was installed paraglacial processes were very active generating many rock glaciers lithology explains some paraglacial landforms distribution 1 landslides are associated with incohesive sandy and shale rocks 2 rock glaciers mainly occur in quartzite areas 3 in limestone areas subterranean drainage contributes to glacial landscape preservation but suffosion dolines affect some glacial deposits topography is also a key factor in paraglacial processes 1 moraines are well preserved in gently sloping valleys but rare in the steeper where they are usually transformed into moraine or debris mantled slopes 2 alluvial fans are more frequent in the steeper valleys but more dissected by postglacial river action 3 elevation and orientation show little influence on paraglacial landforms except in the generation of some periglacial features such as rock glaciers

the rate of bedrock weathering by frost action field measurements and a predictive model shattering rate surface temperature moisture content and the physical and strength properties of bedrock were measured in four rockwall sites of the japanese alps five year observations revealed that the bedrock shattering rate was usually much higher in the freeze thaw period from october to next may than in the frost free period from june to september this indicates that frost action is the most important shattering process although unusual heavy rainstorms in summer are also responsible for the shattering a combination of some empirical relationships derived from recent laboratory experiments leads to a predictive model of the frost shattering rate this model shows that the annual shattering rate is dependent on the annual freeze thaw frequency on the rock surface and the degree of saturation and tensile strength of the rock masses the coefficients involved in the model were determined using the field data

understanding stress and deformation in active volcanoes no eruption no caldera collapse and no large landslide can takeplaceinavolcanounlessitsstateofstressissuitablefortheassociatedtype of rock failure the state of stress in turn results in deformation andbothstressanddeformationdependonthemechanicalpropertiesof the rocks that constitute the volcano understanding stress anddeformation in volcanoes is thus of fundamental importance forunderstanding unrest periods and for accurate forecasting volcanofailure such as may result in large scale lateral and vertical collapsesand eruptions deformation studies in volcanic areas have signi cantly improved both in quality and quantity during the past decade while theinterest of the scienti c community and the volcanological commu nity in particular has primarily been in the description andinterpretation of the deformation especially at active volcanoes new and powerful techniques have recently become available toimprove our understanding of the local stresses and mechanicalproperties of volcanoes and how they relate to surface deformation volcano deformation studies in the last years have of courseincluded standard eld and analytical techniques but in additionthere has been increasing use of advanced analogue and numericalmodels as well as modern geophysical monitoring techniques such asgps and insar all these techniques have contributed to an improvedunderstanding of various aspects of both regional and local volcanodeformation at the regional scale the relationship between tectonicsand magmatism at divergent plate boundaries is now better under stood e g kendall et al 2005 wright et al 2006 and so is thegeneral relationship between arc volcanism and seismicity e g walter and amelung 2007 at a more local scale signi cantimprovements have been made in understanding the mechanics ofmagma chamber rupture e g gudmundsson 2006 dyke propaga tion e g polandetal 2004 gudmundssonetal 2008 thestructureof calderas e g acocella 2007 gottsmann and marti 2008 geshi 2009 the collapse of volcanoes e g cervelli et al 2002 amelunget al 2007 the relationships between volcanic activity and edi cedeformation e g neri et al 2009 the seismicity associated withvolcanism benson et al 2008 and the interactions betweenvolcanoes e g miklius and cervelli 2003 andrew and gudmunds son 2008 these and other studies con rm the crucial importance ofunderstandingdeformationandstressinvolcanicareas asisgenerallyrecognised by the volcanological and tectonic communities oneimportanttopicrelatedtovolcanodeformationandstressthatis still not well understood is how active deformation can be used toforecast eruptions and their behaviour this applies particularly to themechanics of dike emplacement the vast majority of volcaniceruptions are fed by dikes and understanding dike propagation andarrest is necessary so as to mitigate various hazards associated withvolcanic eruptions caldera collapses and landslides in particular major eruptions seismicity and sector collapses pose threats out togreat distances from volcanoes understanding these processes however depends on knowing the more general relationshipsbetween deformation stress and volcanic activity the structure and contents of this special issue are motivatedprimarily by our belief that understanding deformation and stress inactive volcanoes is a necessary condition for reliable forecast ofvolcanic eruptions caldera collapses and large landslides thesetopics all belong to the eld of volcanotectonics also we think thatcorrect interpretation of volcano deformation in terms of localstresses and mechanical properties is fundamental for understandingvolcano behaviour and thereby assessing volcanic hazards this special issue derives from a session on volcanotectonics at the2007eguassemblyinvienna austria thefocusison vemaintopicswithin the eld of volcanotectonics the rst topic concerns generalaspects of volcano deformation stress and failure bonafede andferrari 2009 this volume eggert and walter 2009 this volume gudmundsson 2009 this volume the second topic is collapsecalderas battaglia and hill 2009 this volume jonsson 2009 thisvolume kusumoto and gudmundsson 2009 this volume followedby dike propagation and arrest acocella and neri 2009 this volume contents lists available at sciencedirect

an analytical electron microscopy aem investigation of opaque inclusions in some type 6 ordinary chondrites abstract a large number of ordinary chondrites contains micron sized particles of metal and or troilite dispersed in their silicate grains such metallic phases are responsible for the so called darkening of the silicate grains and might be either precipitates which formed during reduction of the silicates or inclusions injected as a melt during a shock event we have investigated these tiny foreign phases by analytical transmission electron microscopy in three unweathered metamorphosed ordinary chondrites saint severin ll6 tsarev l6 and kernouve h6 we also looked for remnant shock indices our tem observations suggest the following sequence of events in the three meteorites first a number of relatively strong shock events occurred on the parent body bodies producing an fe fes melt that was injected into silicate grains along a dense network of open fractures most of these shock defects were subsequently erased by high temperature 700 900 c thermal metamorphism some remnants of the shock events are the observed trails of tiny metal and or sulfide inclusions that formed as a result of fracture healing chemical homogenization of the silicates and limited oxidation of the metallic blebs also occurred during this high temperature annealing event resulting in ni rich inclusions this effect was especially pronounced in the l and ll chondrites studied during subsequent cooling of the body bodies inclusions of chromite and phosphate precipitated nucleating preferentially on lattice defects dislocations subgrain boundaries and on the metal and sulfide inclusions a later shock event of moderate intensity probably corresponding to the separation of the meteorite from its parent body produced new shock features in the silicate grains of the saint severin meteorite including mechanical twins in diopside and straight free screw dislocations in olivine