deep seated gravitational slope deformations related landslides and tectonics abstract deep seated gravitational slope deformations and their relationships with tectonic deformation of rocks is considered to examine the viewpoint of tectonics as a causative factor in slope deformation first a distinction is made between the different types of deep seated gravitational slope deformation then the geomorphological and structural effects of the different macrostructural deformations induced by tectonics on the scale of the whole deforming ridge is briefly discussed finally some case studies that represent either verified or possible cases of gravity deformation in response to tectonic activity are used as illustration

the eurogeul first report of the palaeontological palynological and archaeological investigations of this part of the north sea abstract the eurogeul is the shipping lane gully in front of rotterdam harbour due to the combination of suction dredging and fishing activities diverse faunae are found on its bottom this paper briefly describes the fauna consisting of 13 terrestrial mammals and six marine mammal species radiocarbon dating gave two time periods from which the bones originate ca 37 500 48 500 bp and ca 7 8000 bp pollen sampling gave similar results respectively an interstadial before the last glacial maximum and the early holocene boreal period human artefacts dating from the boreal period add to our understanding of the quaternary history of the southern north sea area

the hermitage of cerbaiolo tuscany italy stability conditions and geomorphological characterization the italian cultural heritage is one of the most noticeable in the world an important part of it is subjected to natural hazard and risk conditions religious buildings due to their location on impervious sites are particularly exposed to landslides in this paper we study the hermitage of cerbaiolo tuscany central italy the hermitage founded in the 8th century as a benedictine monastery is now a franciscan women institute seat the buildings are on the edges of a limestone plate overlapped to a clayey formation falls toppling and slides are present along the limits of the plate due to the geomechanics properties of the rock and to the contrast between the two lithological complexes in order to identify the main joint sets affecting the rock mass a structural geological survey was carried out and four sets are identified the rock plate was classified according to bieniawski barton and geological strength index approaches the outcomes confirm the predisposing factors to mass movements corresponding to the intensity and characteristics of fracturing of the rock mass with regard to the slope stability analysis a failure mechanism involving sliding along a single plane plane failure was assumed on the first approximation the analyses take into account the presence of tension cracks as an indicator factor for the instability phenomenon the results of stability analyses performed in static and seismic conditions indicate a widespread instability condition the dip slope direction the properties and type of discontinuities and the local variation of composition influence the hazard assessment

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

groundmass crystallization of mount st helens dacite 1980 1986 a tool for interpreting shallow magmatic processes the 1980 1986 eruption of mount st helens volcano provides an unprecedented opportunity to observe the evolution of a silicic magma system over a short time scale groundmass plagioclase size measurements are coupled with measured changes in matrix glass plagioclase and fe ti oxide chemistry to document increasing groundmass crystallinity and thus to better constrain proposed physical models of the post may 18 1980 magmatic reservoir measurements of plagioclase microlite and microphenocryst sizes demonstrate that relatively rapid growth approximately 10 9 cm s of groundmass plagioclase occurred immediately subsequent to may 18 relatively rapid plagioclase growth continued through the end of 1980 at an average rate of 3x10 11 cm s plagioclase growth rates then decreased to 1x10 11 cm s through 1986 changes in groundmass crystallinity are reflected in changes in both matrix glass and plagioclase microphenocryst rim chemistry although the matrix glass composition appears to have remained approximately constant from 1981 1986 after a rapid compositional change from may 18 until the end of 1980 plagioclase microphenocrysts show increasingly more complex zoning patterns with time microphenocryst core compositions are commonly positively correlated with crystal size both of these observations indicate continuous groundmass plagioclase growth through 1986 magmatic temperatures estimated from fe ti oxide pairs are approximately constant through 1981 at eruption temperatures of 930 c and at log fo2 of 10 8 by 1985 1986 oxide temperatures decreased to 870 c chemical and textural changes can be explained by 1 rapid degassing and crystallization in response to the intrusion of magma into a shallow 4 5 km reservoir toward the end of the may 18 1980 eruption 2 continued crystallization at a much reduced rate through 1986 due to slow cooling of the shallow magma reservoir growth rates and consequent chemical changes appear to decrease at the end of 1980 this is coincident with the change in eruption style from explosive eruptions sometimes followed by dome growth to solely extrusive dome building events and can be explained by the expected viscosity increase of both degassing and increasing crystallinity the model of twostage crystallization of magma in a shallow reservoir is consistent with conclusions from gas studies casadevall et al 1983 gerlach and casadevall 1986 a b patterns of crater deformation chadwkck et al 1988 and post 1980 seismicity endo et al 1990 although it does not explain the experimental data of hill and rutherford 1989 on the growth rate of amphibole reaction rims textural measurements on mount st helens dacite can also be used to evaluate crystallization kinetics in silicic magmas systems for which experimental data is almost non existent plagioclase growth rates are 5 10 times slower than estimated plagioclase growth rates in basaltic systems a result consistent with the higher viscosity of a more silicic melt furthermore patterns of textural change both average crystal size and number density are similar to those observed during the 1984 mauna loa eruption by lipman and banks 1987 suggesting that the only modification to the crystallization behavior of plagioclase required in extrapolation from basaltic systems is a moderate decrease in rates such that the rate of crystallization scales with the melt viscosity

crystallization of mount st helens 1980 1986 dacite a quantitative textural approach quantitative measurements of crystal size distributions csds have been used to obtain kinetic information on crystallization of industrial compounds randolph and larson 1971 and more recently on hawaiian basalts cashman and marsh 1988 the technique is based on a population balance resulting in a differential equation relating the population densityn of crystals to crystal sizel i e at steady staten no exp l itg whereno is nucleation density g is the average crystal growth rate is the average growth time and the nucleation ratej nog csd inn vsl plots of plagioclase phenocrysts in 12 samples of mount st helens blast dacite and 14 samples of dacite from the 1980 1986 mount st helens dome are similar and averageg 9 6 1 1 10 3 cm andno 1 2 106 cm 4 reproducibility of the measurements was tested by measuring csds of 12 sections cut from a single sample in three mutually perpendicular directions precision of the size distributions is good in terms of relative but not necessarily absolute values 10 growth and nucleation rates for plagioclase have been calculated from these measurements using time brackets of 30 150 years growth ratesg are 3 10 10 12cm s and nucleation ratesj are 5 21 10 6 cm3 s g andj for fe ti oxides calculated from csd data areg 2 13 10 13 cm sec andj 7 33 10 5 cm3 s respectively the higher nucleation rate and lower growth rate of oxides resulted in a smaller average crystal size than for plagioclase sizes of plagioclase microlites 0 01 mm in the blast dacite groundmass have been measured from backscatter sem photographs nucleation of these microlites was probably triggered by intrusion of material into the cone of mount st helens in spring 1980 this residence time of 52 days gives minimum crystallization estimates ofg 1 3 10 11 cm s andj 9 16 1o3 cm3 s the skeletal form of the microlites provides evidence for nucleation and growth at high values of undercooling t relative to the phenocrysts a comparison of nucleation and growth rates for the two crystal populations phenocrysts vs microlites suggests that while growth rate seems to be only slightly affected by changes in t nucleation rate is a very strong function of undercooling a comparison of plagioclase nucleation and growth rates measured in the mount st helens dacite and in basalt from makaopuhi lava lake in hawaii suggests that plagioclase nucleation rates are not as dependent on composition groundmass textures suggest that plagioclase microphenocrysts crystallized at depth rather than in the conduit in the dome or after extrusion onto the surface most of this crystallization appears to be in the form of crystal growth coarsening of groundmass microphenocrysts at small degrees of undercooling rather than extensive nucleation of new crystals this continuous crystallization in a shallow magmatic reservoir may provide the overpressurization needed to drive the continuing periodic domebuilding extrusions which have been the pattern of activity at mount st helens since december 1980

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

magma budgets and steady state activity of vulcano and stromboli we present three models for magma budget during steady state volcanic activity by which non erupted magma is emplaced as dykes or cumulates or crystallises in place using gas and thermal data we apply our models at vulcano to calculate degassing cooling and crystallisation of magma at a rate of 40 375 kg s 1 within a magma body with an upper surface at a 2 km depth at stromboli we calculate a steady magma supply of 300 1300 kg s 1 to shallow 1 km depths

dynamics of magma mixing and degassing recorded in plagioclase at stromboli aeolian archipelago italy crystal rich materials scoriae and lava flows emitted during the 1985 2000 activity of stromboli were taken into consideration for systematic study of bulk rock matrix glass chemistry and in particular for the study of chemical and textural zoning of plagioclase the most abundant mineral phase over the considered time period bulk rock composition remained fairly constant in both major sio2 49 2 50 9 wt and k2o 1 96 2 18 wt and trace elements the quite constant chemistry of matrix glasses also indicates that the degree of crystallization of magma was maintained at around 50 vol plagioclase ranges in composition between an62 and an88 and is characterized by alternating 10 100 m thick bytownitic and labradoritic concentric layers although the dominant and representative plagioclase of scoriae is an68 the labradoritic layers an62 70 show small scale 1 5 m oscillatory zoning are free of inclusions and appear to record episodes of slow crystal growth in equilibrium with a degassed liquid having the composition of the matrix glass in contrast the bytownitic layers an70 an88 are patchy zoned show sieve structure with abundant micrometric glass inclusions and voids and are attributed to rapid crystal growth

quaternary gomphotheres mammalia proboscidea gomphotheriidae from the continental shelf pearl islands panama abstract fishermen have recovered four quaternary proboscidean teeth from the continental shelf in the vicinity of the pearl islands about 50 80 km offshore from the southern coast of panama two upper third molars m3 and one lower third molar m3 are similar to comparable teeth of the pleistocene gomphothere cuvieronius based on the presence of 4 to 5 lophs lophids that are either horizontal or slightly inclined to long axis of the tooth and rather complicated enamel with single trefoils incipient double trefoils and numerous small accessory cusps cuvieronius is also known from the pleistocene el hatillo and la trinidaita sites from the azuero peninsula in panama the teeth of cuvieronius from the pearl islands are referred to c hyodon following recent taxonomic revisions indicating a single pan american species of this genus was present in both north america and south america the oldest records of cuvieronius are from early pleistocene early irvingtonian faunas in el salvador florida and new mexico cuvieronius dispersed to south america in the early pleistocene during the great american biotic interchange with the earliest record of c hyodon on that continent from the early to middle pleistocene ensenadan tarija fauna in bolivia the two late pleistocene populations of c hyodon in the neotropical region have a disjunct biogeographic distribution with the population from southern mexico and central america separated from the second population in the andean highlands of ecuador peru and bolivia by a distance of about 1000 km the intervening region comprising the lowland tropics of northern south america was populated by the gomphothere notiomastodon during the late pleistocene although notiomastodon is also known from andean localities in ecuador and peru two of the cuvieronius teeth from the pearl islands were recovered in nets by shrimp fisherman from depths of about 90 m likely indicating they date to the last glacial maximum between 30 and 15 ka when sea level was as much as 120 m lower than present and the gulf of panama was dry land these teeth represent the first record of late pleistocene fossils of terrestrial mammals from the continental shelf in central america

middle pleistocene age of the fossiliferous sedimentary sequence from tarija bolivia abstract the highly fossiliferous sediments of the tolomosa formation from tarija southern bolivia represent one of the most important localities in south america that documents the great american biotic interchange over the past several decades chronostratigraphic studies have indicated a middle pleistocene age for the tolomosa formation from 1 1 to 0 7 ma this interval correlates to the ensenadan south american land mammal age as it is characterized from classic localities in argentina recently however a new interpretation based on ams 14c ages indicates that the fossiliferous sediments from tarija are latest pleistocene i e

rockfalls in the duraton canyon central spain inventory and statistical analysis abstract this paper presents an initial analysis of the rockfall processes affecting the walls of the canyon of the river duraton this 34 km long meandering canyon in the basin of the river duero in central spain 41 18 n 3 45 w has evolved in a large scale outcrop of late cretaceous calcareous rocks dolomite and limestone deformed into a series of asymmetrical folds its vertical scarps range from 80 to 100 m its width varies from 150 to 300 m and its floor is between 30 and 50 m wide the research consisted of drawing up an inventory of rockfalls from a field survey and mapping the fallen blocks deposited on the basal talus or on the canyon floor which in turn allowed the original location of each block on the scarps to be identified and located on the orthophotos available a digital elevation model dem was produced using a geographic information system gis and maps made of the aspects and slopes the aspect of each rockfall data point was determined and this initial database was completed with other significant parameters location on the valley side relationship with the tectonic structure and relative age an approximate delimitation was also produced of the potential rockfall source area by reclassifying the slopes according to morphometric criteria the result is a geomorphic rockfall inventory map showing the distribution of the rockfalls and a basic statistical analysis to allow a preliminary evaluation of the rockfall characteristics in relation to both their topoclimatic location aspect and their structural location with or counter to the dip of the strata and to the current geomorphic dynamic through a study of recent scars on the scarps recent rockfalls have also been related to the meteorological conditions in which they occurred

effects of magma storage and ascent on the kinetics of crystal growth the size distributions of crystals of olivine plagioclase and oxides of the 1991 93 eruption at mt etna italy are analyzed the simultaneous collection of this information for different minerals gives precious insight into the cooling history of lavas three distinct episodes are detectable a storage of the magma in a deep reservoir characterized by nearly constant and low nucleation and growth rates near to equilibrium an ascent phase with an ever increasing nucleation rate related to volatile exsolution and finally a quenching phase in addition to geochemical and geophysical evidence the similarity of the crystal size distributions of the present eruption with those of previous ones of this century makes it possible to exclude that crystal size distributions of etnean lavas are due to mixing of different populations this strongly suggests that the main features of the volcano feeding system have not changed despite observed variations in the magma output rates

coupled degassing and crystallization experimental study at continuous pressure drop with application to volcanic bombs experiments on degassing of water saturated granite melts with a pressure drop from 100 and 450 mpa to 40 and 120 mpa respectively at temperatures close to feldspar liquidus 750 700 c were carried out to determine the modality of water exsolution and vesicle formation at the liquidus temperature pressure drop rates as small as approximately 100 bar day were used uniform space distributions of bubbles of exsolved water were obtained with starting glass containing a small fraction 0 5 vol of trapped air bubbles volume crystallization of feldspar was observed in degassed melts supplied with seeds bubble size distributions bsd measured in granite glasses after degassing are presented data on vesicle characteristics number radius area elongation were acquired on images digitized with standard software while the reconstruction of size distributions was performed with the schwartz saltikov unfolding procedure bubble size distributions of size classes in the range 5 1000 m were acquired with proper magnification and satisfactory statistical reliability of determined number densities the bsds of the experimental samples are compared with the results of measurements of rapidly degassed products of mt etna and vulcano island many particular features of the bubble nucleation and growth can be distinguished in an individual bsd however the general bsd of the whole data set including natural ones can be relatively well described with linear regression in bilogarithmic coordinates the slope of this regression is approximately 2 8 0 1 this dependence is in striking contrast with distributions theoretically predicted with classical nucleation models based on homogeneous nucleation of vesicles the theoretical distribution requires the occurrence of strong maxima that are not observed in our experimental and natural samples thus arguing for heterogeneous nucleation mechanisms

persistent polybaric rests of calc alkaline magmas at stromboli volcano italy pressure data from fluid inclusions in restitic quartzite nodules a fluid inclusion study has been performed on quartzite nodules of stromboli volcano hosted by calc alkaline lavas of both the strombolicchio 200 ka and paleostromboli ii 60 ka periods the nodules are mainly composed of quartz crystals with subordinate plagioclase and k feldspar small interstitial minerals such as plagioclase k feldspar clinopyroxene biotite and quartz are also found together with glass muscovite epidote and zircon occur as accessory minerals different quartzite nodules occur 1 equigranular polygonal granoblastic quartzite nodules forming a polygonal texture with clear triple points 2 inequigranular polygonal granoblastic quartzite nodules and 3 break up nodules with strongly resorbed quartz these quartzites are restites from partial melting involving felsic crustal rocks at the magma wall rock contact restitic quartz re crystallises at variable and generally high temperatures leading to the formation of quartzites with different textures quartz grains contain five types of fluid inclusions distinguished on the basis of both fluid type and textural phase relationships at room temperature type i are two phase liquid vapour co2 rich fluid inclusions they are primary and subordinately pseudosecondary in origin and have undergone re equilibration processes type ii mono phase two phase vapour liquid vapour co2 rich fluid inclusions are the most common and based on their spatial distribution and shape they can be divided into two subclasses type iia and type iib type ii inclusions are secondary or pseudosecondary and they are assumed to have formed after decrepitation of type i inclusions and cracking of the host quartz type iii inclusions are mono phase vapour they possibly contain co2 at very low density and surround the inner rims of quartz grains type iv two phase silicate melt inclusions contain glass co2 rich fluid some of them are cogenetic with type ii inclusions finally type v two phase liquid vapour aqueous inclusions are both vapour rich and liquid rich aqueous inclusions microthermometric experiments were performed on both type i and ii inclusions type i inclusions homogenise to liquid between 20 and 30 5 c type iia inclusions homogenise to vapour in the 24 to 30 c range with a maximum peak of frequency at 29 c type iib inclusions also homogenise to vapour between 14 and 25 c there appears to be no difference in homogenisation temperature distribution between the strombolicchio and paleostromboli ii samples the trapping pressures of the fluid inclusions have been obtained by combining the microthermometric data of the strombolicchio and paleostromboli ii samples with the pressure temperature volume i e density characteristics for a pure co2 system the data on the early inclusions type i suggest an important magma rest at a pressure of about 290 mpa i e about 11 km depth type iia co2 inclusions suggest that a second magma rest occurred at a pressure of about 100 mpa i e about 3 5 km depth whereas type iib inclusions were trapped later at a shallower depth during the final magma upwelling no pressure depth differences seem to occur between the strombolicchio and paleostromboli ii periods indicating the same polybaric rests for the calc alkaline magmas of stromboli despite their significantly different ages this persistence in magma stagnation conditions from 200 to 60 ka suggests a similar plumbing system for the present day strombolian activity

crystal size distribution systematics and the determination of magma storage times the 1959 eruption of kilauea volcano hawaii abstract the theory of crystal size distribution csd theory is based on a steady state population balance that monitors the flux of crystals growing into and out of specificed size categories in precipitating solutions the conservation equation describing this balance permits crystal growth and nucleation rates to be determined directly from crystal size distribution data in this investigation it is shown that csd analysis can alternatively be used to calculate the residence time of crystals in the system or in volcanologic terms the magma storage time prior to eruption if the characteristic crystal growth rate can be independently determined or estimated the crystal size data needed for storage time determinations are easily obtained from thin sections of glassy eruption samples and the mathematical calculations are relatively simple analysis of the errors inherent in this new technique predicts storage estimates accurate to within an order of magnitude

lateral spreading processes in mountain ranges insights from an analogue modelling experiment abstract the results of a study on gravitational induced lateral spreading phenomena are here reported the lateral spreading processes are widely represented in the italian apennines due to the widespread overlapping of stiff rock masses on more ductile ones the stress strain evolution of these processes was investigated by combining an analogical and a numerical modelling approach the analogue modelling reproduced the evolution of a carbonate ridge thrust over a clayey flysch with reference to the case study of mt roccatagliata mt sant angelo ridge the rock mass juxtaposition was reproduced in a laboratory experiment by overlapping a brittle concrete on a viscous ductile material these materials were selected with rheological properties physically scaled with respect to the natural rock mass prototypes the spreading phenomenon was modelled by opening horizontal panels in sequential stages and monitoring the resulting stresses within the ductile material during the experiment a stress strain modelling was also performed by an fdm numerical solution this modelling replied the laboratory experiment by testing the use of different rheological constitutive laws the resulting stresses and morphological evolutions are comparable with the analogical laboratory experiment only if a time dependent rheological behaviour is assumed for the ductile material the results show that lateral spreading processes can be properly investigated by combining analogue and numerical modelling techniques which take into account the viscous plastic behaviour of the used materials

chaotic dynamics and fractals in magmatic interaction processes a different approach to the interpretation of mafic microgranular enclaves abstract fractals have been used for describing a wide range of natural processes however applications of fractal geometry to the study of magma mingling mixing processes is almost completely lacking in spite of the fact that such an approach could give new insights into the nature of magmatic interactions fractal analyses of two geochemically linked groups of mafic microgranular enclaves mme from the sithonia plutonic complex northern greece have been performed because of the difficulties involved in using contours of enclaves to estimate their fractal dimensions a different approach is used in this paper fractal dimension is estimated using distribution maps of chemical elements inside enclaves the results obtained indicate that a clear correlation between fractal dimensions of enclaves and geochemical evidences of interaction exists and hence the two groups of enclaves reflect different degrees of interaction from a dynamical point of view stretching and folding processes between two magmas with different rheologies are considered representative of magmatic interaction this dynamic system can easily generate chaotic patterns recognized by the presence of fractal structures the contemporaneous occurrence of well mixed regions together with poorly mixed regions in the same system is thought to be similar to the host enclave system found in many granitoid plutons in particular mme are believed to represent islands of partially mixed mafic fluid subjected to different degrees of interaction with the host granitoid whereas host rocks are believed to represent mixed regions where the mixing process acted more efficiently producing almost completely hybrids it is shown that fractal geometry and chaotic dynamics can be considered suitable techniques in studying complex petrological phenomena and they can represent helpful methods in the development of petrogenetic models

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization ii makaopuhi lava lake crystal size distribution csd theory has been applied to drill core samples from makaopuhi lava lake kilauea volcano hawaii plagioclase and fe ti oxide size distribution spectra were measured and population densities n were calculated and analyzed using a steady state crystal population balance equation n n0 exp l g slopes on ln n versus crystal size l plots determine the parameter g a product of average crystal growth rate g and average crystal growth time the intercept is j g where j is nucleation rate known temperature depth distributions for the lava lake provide an estimate of effective growth time allowing nucleation and growth rates to be determined that are independent of any kinetic model plagioclase growth rates decrease with increasing crystallinity 9 9 5 4 10 11 cm s as do plagioclase nucleation rates 33 9 1 6 10 3 cm3 s ilmenite growth and nucleation rates also decrease with increasing crystallinity 4 9 3 4 10 10 cm s and 15 2 2 10 3 cm3 s respectively magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus g 2 9 10 10 cm s j 7 6 10 2 cm3 s moments of the population density function were used to examine the change in crystallization rates with time preliminary results suggest that total crystal volume increases approximately linearly with time after 50 crystallization a more complete set of samples is needed for material with 50 crystals to define the entire crystallization history comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling this interpretation is consistent with proposed thermal models of magmatic cooling where heat loss is balanced by latent heat production to maintain equilibrium cooling

population density and zoning of olivine phenocrysts in tholeiites from kauai hawaii the population density of olivine phenocrysts of the tholeiites display an exponential variation which is typical of igneous as well as contact metamorphic rocks the exponential variation is explained by a new growth probability model which is consistent with experimental work the forsterite content of the olivine phenocrysts decreases with decreasing size various phenocryst features suggest that the tholeiites first crystallized slowly in a magma chamber after which they underwent crystallization for a short period of time in a feeder dyke before eruption took place

intra grain sr isotope evidence for crystal recycling and multiple magma reservoirs in the recent activity of stromboli volcano southern italy over the last several hundred years stromboli has been characterized by steady state strombolian activity the volcanic products are dominated by degassed and highly porphyritic hp magma black scoria bombs lapilli and lava flows of basaltic shoshonitic composition periodically about one to three events per year more energetic explosive eruptions also eject light coloured volatile rich pumices with low phenocryst content lp magma that have more mafic compositions than the hp magma an in situ major and trace element and sr isotope microanalysis study is presented on four samples chosen to characterize the different modes of activity at stromboli a lava flow 1985 1986 effusive event a scoria bomb from the normal present day activity of stromboli april 1984 and a scoria and coeval pumice sample from a recent more explosive eruption september 1996 plagioclase an

textural effects of steady state behaviour of the stromboli feeding system abstract the exceptionally persistent activity of stromboli volcano has lasted for at least 1400 years the normal strombolian activity is periodically interrupted by more energetic explosions 1 2 per year and by sporadic effusive episodes every 10 20 years normal activity and effusive episodes are characterized by crystal rich high k to shoshonitic basalts issuing from a volatile poor shallow system crystal poor pumice are emitted only during more violent explosions and are thought to derive from deep pulses of volatile rich magma shallow level degassing induces massive crystallization of deep pulses of feeding magma that continuously mixing with the resident one produces the crystal rich shoshonite of the persistent activity we examined the crystallization history of the crystal rich shallow reservoir using plagioclase crystal size distribution csd analysis of scoriae and lavas emitted in the past twenty years csds show a linear dependence from crystal size in the size interval 0 06 1 2 mm number density of larger crystals is biased by right hand truncation effects csds slopes and intercepts are quite constant during the whole considered time span revealing a system that is close to the equilibrium also from a kinetic point of view the linear crystal size distribution are reached by the system through episodes of growth and resorption respectively occurring in the degassed and undegassed magma during the continuous mixing in the feeding system plagioclase net growth rate 2 10 11 cm s results from a balance of growth 10 10 cm s and resorption episodes which induce spectacular zoning and resorption textures in crystals larger than 200 m csds of mafic phases cannot be accurately acquired on each single sample due to poor counting statistics the evaluation of pyroxene and olivine csd on the whole data set however confirms the conclusions acquired from plagioclase csds

interaction between regional and local tectonic forcing along a complex quaternary extensional basin upper tiber valley northern apennines italy abstract in extending areas undergoing regional tectonic uplift the persistence of subsidence at a normal fault hanging wall depends on the competition between regional and local tectonic effects when regional uplift exceeds the subsidence of the hanging wall block denudation prevails at both the hanging wall and the foot wall when local tectonic subsidence exceeds regional uplift sedimentation occurs over the hanging wall block supplied by foot wall erosion we analyzed a pliocene quaternary continental basin currently crossed by the tiber river in italy the tectono sedimentary evolution of the basin developed at the hanging wall of a regional low angle extensional detachment the alto tiberina fault in the axial region of the northern apennines of italy this area is affected by regional uplift on the order of 0 5 1 0 mm yr the present day activity of the fault is revealed by both microseismicity and geodetic gps data we investigated the mid 10 100 ka and long term 0 5 3 0 ma evolution of the three depocenters by studying the continental pleistocene succession infilling the basin as well as fluvial terraces and higher paleosurfaces carved into the pleistocene deposits by using surficial geologic data and an interpretation of a set of seismic reflection profiles we show that the three depocenters experienced a fairly similar evolution during the pliocene early pleistocene when a 1000 m thick continental succession was deposited on the contrary geomorphological observations indicate that at the beginning of the middle pleistocene a switch occurred in the evolution of the three depocenters in the northernmost sansepolcro sub basin bounding normal faults are active and hanging wall subsidence outpaces regional uplift concurrently in the umbertide and ponte pattoli sub basins uplift dominates over the hanging wall subsidence promoting river incision and exhumation of the pleistocene deposits for these two depocenters by means of terrace river correlations we estimate that the incision rate is 0 3 0 35 mm yr suggesting a maximum tectonic subsidence of 0 2 mm yr the identification of a heterogeneous uplift pattern along the hanging wall of the alto tiberina fault driven by different displacement rates of its fault splays allowed us to characterize fault segments with different activities and possibly different seismic behaviors

crystal size distributions and scaling laws in the quantification of igneous textures this study demonstrates the value of the combined use of scaling of the chemical evolution of cooling magmas have investigated the detailed relationships between temanalysis and crystal size distribution csd measurements in the interpretation of igneous textures and outlines applications of these perature phase abundance and phase composition the reaction series bowen 1922 and the cipw norm cross methods to other fundamentally important problems theoretical calculations and measurements of natural samples are used to et al 1903 have been supplemented by modern thermodynamic models that predict the compositions and abundcharacterize the relationship between igneous texture and cooling history the total number nt and mean length l of crystals ances of minerals in equilibrium with melt of a given composition and temperature e g ariskin et al 1993 in a sample are correlated through a scaling relationship of the form n t l this proportionality depends on the mineralogy ghiorso sack 1995 although there are a few areas of uncertainty the chemistry of igneous petrogenesis is of the rock and so a modal normalization factor c is introduced the csd slope s and intercept ln n are uniquely related to fairly well understood but chemical models cannot address the central probeach other through the equation ln n 4ln s ln c where s l this overall relationship allows the texture of a rock lem of igneous crystallization which is the physical process of generating a set of crystals from magma two to be related to the local duration of cooling through an arbitrary crystal growth model quantification of the link between the texture magmas with the same composition will normally produce the same minerals in the same proportions however of a rock and its cooling history makes it possible to predict spatial variations in texture we show an example of this method using depending on their thermal histories these two magmas can solidify into rocks with drastically different physical the sudbury igneous complex canada additional applications include relating the textures of volcanic rocks to spatial and temporal appearances e g basalt and gabbro the set of minerals is the same but what distinguishes them is the abundance variations in the magma chamber and extracting kinetic parameters from suites of comagmatic rocks and size of the constituent crystals the fine grained rocks in the chilled margins of most basic intrusions cooled rapidly and the coarse grained rocks in the interiors of plutons cooled slowly this has

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects