surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

mantle and crustal processes in the magmatism of the campania region inferences from mineralogy geochemistry and sr nd o isotopes of young hybrid volcanics of the ischia island south italy ischia one active volcano of the phlegraean volcanic district prone to very high risk is dominated by a caldera formed 55 ka bp followed by resurgence of the collapsed area over the past 3 ka the activity extruded evolved potassic magmas only a few low energy explosive events were fed by less evolved magmas a geochemical and sr nd o isotope investigation has been performed on minerals and glass from products of three of such eruptions molara vateliero and cava nocelle 2 6 ka bp data document strong mineralogical geochemical and isotopic heterogeneities likely resulting from mingling mixing processes among mafic and felsic magmas that already fed the ischia volcanism in the past detailed study on the most mafic magma has permitted to investigate its origin the mantle sector below ischia underwent subduction processes that modified its pristine chemical isotopic and redox conditions by addition of 1 of sediment fluids melts similar processes occurred from southeast to northwest along the apennine compressive margin with addition of up to 2 5 of sediment derived material this is shown by volcanics with poorly variable typical 18o mantle values and 87sr 86sr progressively increasing toward typical continental crust values multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust acquiring more 18o than 87sr at ischia 7 of hercynian granodiorite assimilation produced isotopically distinct k basaltic to latitic magmas a sw ne regional tectonic structure gave these magmas coming from large depth the opportunity to mingle mix with felsic magmas stagnating in shallower reservoirs eventually triggering explosive eruptions

mineralogy and sr nd isotopes of spm and sediment from the mandovi and zuari estuaries influence of weathering and anthropogenic contribution clay minerals and sr nd isotopes of suspended particulate matter spm and bottom sediment were investigated along transect stations of the mandovi and zuari estuaries western india to determine the provenance and role of estuarine processes on their distribution kaolinite and illite followed by minor goethite gibbsite and chlorite were present in spm and bottom sediment at all stations both during monsoon and pre monsoon smectite occurred in traces at river end stations but its contents increased downstream in both estuaries smectite contents were much higher in zuari than in mandovi estuary the 87 sr 86 sr ratios and nd of spm were higher than those in hinterland rocks and laterite soils the sr ratios were highest at river end stations of both estuaries and decreased sharply seaward the sm nd ratios of spm and sediment were close to that of iron ore material flushed into the estuaries the mean nd of spm and sediment were similar in both estuaries it is suggested that the smectite is formed in coastal plains and its distribution downstream is controlled by lithology and drainage basin of rivers abundant kaolinite and high sr ratios reflect chemical weathering and lateritization of source rocks sr isotopic ratios along transects are influenced by changes in salinity organic matter and turbidity high and near identical nd values along transect stations of both estuaries suggest that the nd isotopic compositions are influenced by the lateritization of source rocks and anthropogenic contribution of ore material

geomorphic effectiveness a linear concept in a non linear world geomorphic effectiveness has been an influential concept in geomorphology since its introduction by reds wolman and john miller in 1960 it provided a much needed framework to assess the significance of an event by comparing event magnitude to the resultant geomorphic effects initially this concept was applied primarily in river channels under the linear assumption that geomorphic responses to similarly sized flood events will be consistent numerous authors have since attempted to quantify a direct proportional relationship between event magnitude and different forms of geomorphic response in a variety of geomorphic settings in doing so these investigations applied an array of metrics that were difficult to compare across different spatiotemporal scales and physiographic and geomorphic environments critically the emergence of other geomorphic concepts such as sensitivity connectivity thresholds and recovery has shown that relationships between causes events and geomorphic effects responses are often complex and non linear this paper disentangles the complex historical development of the geomorphic effectiveness concept and reviews the utility of various metrics for quantifying effectiveness we propose that total energy joules is the most appropriate metric to use for quantifying the magnitude of disturbance events cause and volumetric sediment flux associated with landform modification is the most appropriate metric for quantifying geomorphic effects while both metrics are difficult to quantify they are the only ones which facilitate comparison across a range of spatiotemporal scales comparability in a variety of geomorphic environments flexibility the geomorphic effectiveness concept can continue to be useful provided that geomorphologists use flexible and comparable metrics today geomorphologists are better prepared to consider the influence of non linear processes on determinations of geomorphic effectiveness allowing investigators to not only determine if a disturbance event was effective but also to explain why or why not copyright

channel bed adjustment along mine affected rivers of northeast tasmania forty million m3 and 1 million m3 of mining waste are estimated to have been supplied respectively to the ringarooma and george rivers between 1875 and 1984 given the volumes involved and the fact that much of the input was less than 5 mm in diameter the size composition of the bed material changed from gravel to sand as the rivers progressively aggraded their beds downstream increases in bed height of over 10 m and 1 m are predicted respectively for the two rivers with change becoming more gradual further downstream with upstream supplies becoming depleted first degradation followed the same pattern as aggradation progressing downstream maximum rates of almost 0 5 m yr 1 were measured degradation has returned the george river to its pre 1875 level but has yet to reach the downstream reaches of the ringarooma where sediment waves continue to pass over a slightly aggrading bed where degradation has been occurring long enough the bed material has again become gravelly through re exposure of the original bed and or lag concentration of coarser fractions within the introduced load such armouring should improve bed stability and slow the rate of degradation however at herrick which is representative of intermediate reaches with only a thin gravel veneer the annual amount of degradation is reasonably well correlated with flow conditions suggesting that high discharges can strip the surface armour and continue to degrade actively incision has not only changed the vertical position of the rivers but also their planimetric and cross sectional geometry in particular non uniform lowering of the bed has narrowed the channel by up to 60 changes which can be predicted quite accurately by chang s quantitative model of channel adjustment at least another 50 years will be needed for degradation to cleanse the ringarooma of mining debris

lead isotopic analysis within a multiproxy approach to trace pottery sources the example of white slip ii sherds from late bronze age sites in cyprus and syria lead isotope analyses were carried out on fragments of white slip ii ware a late bronze age cypriote pottery ware and on raw materials possibly used for their production sherds originate from three late bronze age sites hala sultan tekke and sanidha in cyprus and minet el beida in syria and clays come from the surroundings of sanidha a production site for white slip ware x ray fluorescence xrf and a principal component analysis pca are combined with pb isotope analyses to further investigate the effectiveness of the latter method within a multiproxy approach for pottery provenance study the pottery sherds from the three sites are compared between themselves and with potential raw material additional x ray diffraction xrd and analyses using a scanning electron microscope sem equipped with an energy dispersive x ray detection edx facility were performed on selected sherds and clays this work confirms that the clay source used for pottery production in sanidha derives from local weathered gabbro it also shows that different origins can be proposed for white slip ii ware sherds from hala sultan tekke and minet el beida and that clays were prepared prior to white slip ii ware production it finally confirms the effectiveness of pb isotopes in tracing pottery provenance not only by comparing sherd assemblages but also by comparing sherds to potential raw materials

water speciation and sr isotopic exchange during water melt interaction a combined nmr tims study on the cretaio tephra ischia island south italy abstract in order to improve the microscopic understanding of the water magma interaction process during explosive volcanism volcanic glasses representative of deposits with sedimentological characteristics suggesting different water melt ratios were studied by a combination of the nuclear magnetic resonance nmr and tims methods the glasses were separated from pumices of two surge layers and one fallout bed of the cretaio tephra ischia island italy which is the product of an explosive eruption that occurred at ischia in the second century bc the 29si cp mas nmr experiments indicate the occurrence of 1h 29si dipolar couplings in glasses from the phreatomagmatic activity suggesting the presence of hydrogen atoms in proximity of silicon atoms this feature is not detected in the glass from the deposit of the magmatic explosion 1h mas nmr spectra reveal different peaks attributed to different hydrous species characterized by different motional properties these include rigid h2o groups isolated in the glass structure more mobile water species and possibly structural hydroxyl groups 1h mas nmr spectra recorded after deuteration experiments of the glass at a temperature up to 300 c revealed that the exchange reactions of the d2o vapor with hydrogen were limited to the most mobile water species possibly on vesicle surfaces or in channels the hydrogen concentration linearly correlates with the 87sr 86sr isotope ratio in glasses suggesting isotopic tracer exchanges between the sr dissolved in the water vapor and the sr in the silicon oxygen network during hydration it is proposed that the uprising melt interacted with a hydrothermal system of seawater derived fluids characterized by relatively high sr isotopic composition

remobilization of andesite magma by intrusion of mafic magma at the soufriere hills volcano montserrat west indies the 1995 1999 eruption of the soufriere hills volcano montintroduction serrat has produced a crystal rich andesite containing quenchthe soufriere hills volcano montserrat located in the textured mafic inclusions which show evidence of having been molten lesser antilles island arc in the west indies began to when incorporated into the host magma individual crystals in the erupt on 18 july 1995 after about 350 years of dormancy andesite record diverse histories amphibole phenocrysts vary from young et al 1998b the eruption was preceded by a pristine and unaltered to strongly oxidized and pseudomorphed by period of seismic swarms which began in january 1992 anhydrous reaction products plagioclase phenocrysts are commonly previous earthquake crises have occurred on montserrat reverse zoned often with dusty sieve textures reverse zoned rims are in 1896 1897 1932 1935 and 1966 1967 powell 1938 also common on orthopyroxene phenocrysts pyroxene geothermometry shepherd et al 1971 initial phreatic and phregives an average temperature of 858 20 c for orthopyroxene atomagmatic activity was followed by extrusion of an phenocryst cores whereas reverse zoned rims record temperatures andesitic lava dome in november 1995 pyroclastic flows from about 880 to 1050 c the heterogeneity in mineral rim generated by gravitational collapse of the unstable dome compositions zoning patterns and textures is interpreted as reflecting have been the dominant form of activity throughout the non uniform reheating and remobilization of the resident magma eruption but periods of explosive activity producing body by intrusion of hotter mafic magma convective remobilization pumice flows and falls have also occurred robertson et results in mixing together of phenocrysts that have experienced al 1998 young et al 1998b dome growth ceased different thermal histories depending on proximity to the intruding suddenly in march 1998 and further activity up to may mafic magma the low temperature and high crystallinity are 1999 has mainly involved gravitational collapses of the interpreted as reflecting the presence of a cool highly crystalline dome and periods of ash venting with some small scale magma body beneath the soufriere hills volcano the petrological vulcanian explosive events observations in combination with data on seismicity extrusion rate the soufriere hills volcano is the only active centre and so2 fluxes indicate that the current eruption was triggered by on montserrat the volcano is a composite of at least recent influx of hot mafic magma five andesitic lava domes flanked by pyroclastic deposits rea 1974 identified four other volcanic centres all

step filling and development of a three layer magma chamber the neapolitan yellow tuff case history abstract the neapolitan yellow tuff the product of the largest known trachytic phreatoplinian eruption gives a good opportunity to investigate the filling mechanisms and internal dynamics of a trachytic magma chamber a detailed study of the geochemical mineralogical and isotopical features of the deposit was carried out to investigate the behaviour of the magma chamber before the eruption the collected data show three distinct compositional groups separated by gaps single depositional units contain glass shards formed contemporaneously although each of these shards is homogeneous they display the same compositional variations and gaps detected in pumice clasts this feature is taken as an evidence for interpreting the detected compositional gaps as real gaps in the chamber therefore the chamber was filled by three distinct magma bodies separated by compositional gaps the uppermost magma was alkali trachyte and highly homogeneous likely a consequence of vigorous convection the intermediate magma was trachyte with a slight and continuous compositional variation likely resulting from less intense convection the lowermost magma was compositionally zoned from alkali trachyte to latite downward this compositional zonation was most likely acquired during uprise from a deeper reservoir the three magmas entered the chamber sequentially from the uppermost to the lowermost the latter entered the chamber short before the beginning of the eruption its input was interpreted as a possible triggering factor for the eruption the results of this study strongly support a step filling mechanism for the neapolitan yellow tuff magma chamber and allow definition of the temporal succession of input of magma batches furthermore they also suggest that the magma bodies did not mix although at least the uppermost two coexisted inside the chamber for a time long enough to allow internal homogeneization by convection

geochemical and b sr nd isotopic evidence for mingling and mixing processes in the magmatic system that fed the astroni volcano 4 1 3 8 ka within the campi flegrei caldera southern italy abstract the astroni volcano was built through seven eruptions that generated pyroclastic deposits and lava domes within the campi flegrei caldera southern italy 4 1 3 8 ka bp whole rock geochemical and b sr nd isotopic investigations were carried out on representative samples of all seven eruptions the products vary from tephriphonolites to phonolites and from latites to trachytes they show textural mineralogical and isotopic evidence of disequilibrium including distinct clinopyroxene populations rounded and or resorbed plagioclase and alkali feldspar and reverse zoned phenocrysts of all these mineral phases the sr nd and b isotopic composition of whole rocks is variable and correlated with the degree of chemical evolution suggesting open system processes in addition to fractional crystallisation moreover significant sr isotopic disequilibrium between the phenocrysts and glass has been documented for one sample the chemostratigraphy of the products indicates that astroni eruptions 1 through 5 were fed by magmas of trachytic to phonolitic composition that were less enriched in radiogenic sr and 11b up section this variability has been interpreted as the result of mingling between at least two distinct magmatic end members one more evolved and the other less evolved another heterogeneous batch of magma resulting from almost complete mixing between the same two end members was drained during eruptions 6 and 7 the more evolved end member characterised by 87sr 86sr 0 7075 143nd 144nd 0 51247 and 11b 8 was very similar to the magma that fed the final phases of the agnano monte spina eruption which occurred a few centuries earlier in the astroni vent area the less evolved end member had 87sr 86sr 0 70726 143nd 144nd 0 51251 and 11b 10 and was likely derived by fractional crystallisation of a mantle derived magma an abrupt decrease in both the sr isotope ratio and the th content detected at the transition between unit 4 and 5 suggests that another magma with a 87sr 86sr ratio intermediate between those of the two identified end members may have been involved in astroni activity the more evolved end member is interpreted as a residue of the agnano monte spina eruption that was invaded by either the intermediate or the less evolved magmatic end member promoting mingling and triggering astroni activity this study of astroni provides insights for both short and long term volcanic hazard assessment as the astroni volcano is the best example of a very close sequence of eruptions from the same vent area in the campi flegrei caldera

exhumation of an active magmatic hydrothermal system in a resurgent caldera environment the example of ischia italy abstract ischia is a rare case of a well exposed caldera system that has experienced rapid recent resurgence which can be used to dissect the anatomy of an otherwise inaccessible active hydrothermal system developed in a caldera forming environment integrated analyses of melt and fluid inclusions mineralogy and stable isotopic compositions of pumices tuffs and syenitic xenoliths of the ischia volcanic system provide strong physico chemical constraints on the shallow magmatic reservoir and the hydrothermal system the hydrothermal system has been exposed by the rapid uplift of the mt epomeo resurgent block the engine of the hydrothermal system of ischia can be identified in the shallow magmatic system at around 2 km depth that hosts hot c 1000 c trachytic magma the hydrothermal system developed principally within thick intracaldera ignimbrite deposits and extended to a depth of at least 1 km defining a series of facies characterized by associations of alteration mineral assemblages typical of a seawater dominated high temperature geothermal system supplementary material sample descriptions and analytical methods are available at http www geolsoc org uk sup18371

a comprehensive study of pumice formation and dispersal the cretaio tephra of ischia italy the cretaio tephra is a small volume 0 02 km3 pumice deposit on the island of ischia in italy it was erupted during historical time and is associated with a tuff ring dome complex extruded along a n s trending normal fault system bordering the east side of the mt epomeo resurgent block 14c ages of the deposit average 1860 a b p which is in agreement with the potsherds found in paleosols underlying and overlying the deposit the eruption sequence consists of 7 members most of these members are pumice fall deposits one is an ash and pumice fallout and another is a surge bed the tephra have a trachytic phonolitic composition all chemical characteristics including major and trace elements and sr isotope composition are homogeneous throughout the sequence the vesicularity of pumice clasts does not show any systematic change the erupted magma had the same amount of volatiles the same flux and vesicle growth behavior throughout the eruption sequence grain size analyses of 90 tephra samples representative of all the members at variable distance from the supposed vent have been processed using the sequential fragmentation transport theory in order to define the effects of eruptive fragmentation and subsequent transport on the particle sizes distribution four significant subpopulations have been identified and related to transport mechanisms

coastal geomorphology through the looking glass abstract coastal geomorphology will gain future prominence as environmentally sound coastal zone management strategies requiring scientific information begin to supplant engineered shoreline stabilization schemes for amelioration of coastal hazards we anticipate substantial change and progress over the next two decades but we do not predict revolutionary advances in theoretical understanding of coastal geomorphic systems paradigm shifts will not occur knowledge will advance incrementally we offer predictions for specific coastal systems delineated according to scale for the surf zone we predict advances in wave shoaling theory but not for wave breaking we also predict greater understanding of turbulent processes and substantive improvements in surf zone circulation and radiation stress models very few of these improvements are expected to be incorporated in geomorphic models of coastal processes we do not envision improvements in the theory of sediment transport although some new and exciting empirical observations are probable at the beach and nearshore scale we predict the development of theoretically based two and three dimensional morphodynamical models that account for non linear time dependent feedback processes using empirically calibrated modules most of the geomorphic research effort however will be concentrated at the scale of littoral cells this scale is appropriate for coastal zone management because processes at this scale are manageable using traditional geomorphic techniques at the largest scale little advance will occur in our understanding of how coastlines evolve any empirical knowledge that is gained will accrue indirectly finally we contend that anthropogenic influences directly and indirectly will be powerful forces in steering the future of coastal geomorphology if you should suddenly feel the need for a lesson in humility try forecasting the future kleppner 1991 p 10

simple shearing block resurgence in caldera depressions a model from pantelleria and ischia abstract similar resurgent blocks occur in caldera depressions at the islands of pantelleria and ischia the two blocks which are tilted show similar deformation patterns and similar distributions of volcanic vents related to resurgence the remaining parts of the floors of the two calderas are not deformed similarities between the two features are so striking that the resurgence mechanism must have been alike a dynamic model for resurgence is presented and called simple shearing block resurgence the triggering mechanism is an increase of the magmatic pressure in the upper part of a shallow magma chamber which results in a vertical direction of the maximum stress applied on the roof rocks the block is first defined by high angle inland dipping marginal detachments and then deformed through a simple shearing mechanism reverse faults on its mostly uplifted side determine an horizontal shortening of the block which is balanced on the opposite side by normal faults oblique movements take place along the other two sides due to this distribution of the stress around the block magmas can reach the surface only through the extensional faults on the less uplifted side

14c age of the museum breccia campi flegrei and its relevance for the origin of the campanian ignimbrite abstract field stratigraphic investigations and ams 14 c dating of carbon particles in paleosols has resulted in a framework of the sequence and age of the pyroclastic products in the campi flegrei area of southern italy the museum breccia cannot be the early phase of the campanian ignimbrite as was previously believed but is from a smaller and later eruption with an age of approximately 17 900 y b p this date also precludes its correlation with the neapolitan yellow tuff 12 000 y b p

sr nd pb o isotopic evidence for decreasing crustal contamination with ongoing magma evolution at alicudi volcano aeolian arc italy implications for style of magma crust interaction and for mantle source compositions abstract new isotopic sr nd pb o data are reported for a suite of basalts mgo up to 10 wt to andesites and associated mineral separates from the island of alicudi aeolian arc southern tyrrhenian sea with the aim of investigating the effects of magma wall rock interaction in continental magmatic systems major and trace elements at alicudi exhibit smooth variations suggesting derivation of the entire suite from a single type of parental magma that underwent fractional crystallisation however 87sr 86sr and 18o values decrease while 143nd 144nd increases with increasing sio2 and decreasing mgo moreover phenocryst phases show isotopic disequilibrium relative to whole rocks and groundmass such an unusual isotope vs major and trace element variation and isotopic disequilibria suggest interaction between magmas and crustal wall rocks but the decrease of 87sr 86sr with increasing differentiation excludes assimilation fractional crystallisation processes we suggest that mafic calcalkaline magmas with primitive sr nd o isotopic signatures were intruded into a deep reservoir where they underwent fractional crystallisation contamination occurred shortly before eruption as the magmas ascended to the surface interactions between magmas and wall rocks were more extensive for the basalts than basaltic andesites and andesites generating a positive correlation between mgo and 87sr 86sr ratios the variable degrees of magma wall rock interaction are suggested to depend on the differing capabilities of magmas to dissolve crustal rocks due to variable temperature and viscosity the present study therefore provides sr nd pb o isotopic evidence on an uncommon modality of magma contamination by upper crust the alicudi andesites have the most primitive isotope signatures over the entire aeolian arc in plots of 206pb 204pb vs 87sr 86sr or 143nd 144nd isotopes the bulk of the aeolian volcanoes fall along a curved trend that connects himu mantle reservoir and the upper crust in contrast the alicudi andesites fall outside this trend and plot on a binary trend connecting himu and em1 mantle reservoirs it is suggested that the alicudi source consisted of a hybrid himu em1 mantle that was modified by fluids or melts coming from an oceanic slab these fluids did not change significantly the isotopic signatures of the wedge but generated high lile hfse ratios which were inherited by the alicudi magma in contrast the compositions of other aeolian volcanoes and of central italian magmatism reflect addition of upper crust to a himu or fozo mantle collectively the data record the complex interplay between different mantle reservoirs and the addition of various amounts and types of subduction related components in the southern tyrrhenian sea

first integrated tephrochronological record for the last 190 kyr from the fucino quaternary lacustrine succession central italy we present the first integrated tephrochronological study major and trace elemental glass composition sr and nd isotope analyses and 40ar 39ar dating for the last one tenth 82 m of the 900 m thick quaternary lacustrine succession of the fucino basin the largest and probably only central apennine intermountain tectonic depression that hosts a continuous lacustrine succession documenting the plio quaternary sedimentary history up to historical times major element glass compositions determined using a wavelength dispersive electron microprobe wds empa yielded the geochemical fingerprinting needed for a reliable identification of most of the 23 stratigraphically ordered tephra layers under investigation these include tephra from italian volcanoes such as campi flegrei etna colli albani ischia vico sabatini and undefined volcanic sources in the neapolitan area and latium region the recognition of key mediterranean marker tephra layers e g x 5 and x 6 is supported by trace element data acquired by laser ablation inductively couple plasma mass spectrometry la icp ms the sr and nd isotope compositions of selected layers where also determined for circumscribing the volcanic source of distal tephra and for supporting correlations with individual eruptive units we also propose a new more expeditious covariation diagram cao feotot vs cl for identifying the volcanic source of trachytic to phonolitic and tephrytic to phonolitic tephra that are the most common compositions of pyroclastic rocks from volcanoes of campania and latium regions finally we present five new 40ar 39ar age determinations including a new analytically well supported and more precise 40ar 39ar age for the widespread y 7 tephra and the first 40ar 39ar age determinations for one tephra from the sabatini volcanic district 126 ka and one tephra from neapolitan volcanic area campi flegrei 159 ka these newly dated tephra are widely dispersed e g monticchio southern italy adriatic sea and lake ohrid macedonia abania and have thus the potential to become important mediterranean mis 5 and mis 6 tephrochronological markers altogether the new geochemical data and 40ar 39ar ages precisely constrain the chronology of the investigated fucino succession spanning the last 190 ka in light of these results and by considering that this sedimentary succession possibly extends back to 2 ma fucino is likely to provide a very long continuous tephrostratigraphic record for the mediterranean area and become a key node in the dense network of tephra correlations of this region

seismologically observed spatiotemporal drainage activity at moulins hydrology is important for glacier dynamics but it is difficult to monitor the subsurface drainage systems of glaciers by direct observations since meltwater drainage generates seismic signals passive seismic analysis has the potential to be used to monitor these processes to study continuous seismic radiation from the drainage we analyze geophone data from six stations deployed at the kaskawulsh glacier in yukon canada during the summer of 2014 using ambient noise cross correlation techniques we locate the noise sources by back projecting the amplitude of the cross correlation to the glacier surface most of the ambient noise sequences are found in two clusters with each cluster located in the vicinity of a moulin identified at the surface stronger seismic radiation is observed during the day consistent with expected variability in melt rates we demonstrate that the sparse seismic network array with 2 km station separation has the ability to detect moulins within the array with a precision of 50 m we confirm that seismic activity is correlated with air temperature and thus melt on a diurnal timescale and precipitation correlates with the activity at longer timescales our results highlight the potential of passive seismic observations for monitoring water flow into subglacial channels through moulins with an affordable number of seismic stations but quantification of water flow rates still remains a challenge the cross correlation back projection technique described here can also potentially be applied to any localized source of ambient noise such as ocean noise tectonic tremor and volcanic tremor

oxygen isotope geochemistry of pyroclastic clinopyroxene monitors carbonate contributions to roman type ultrapotassic magmas the oxygen isotope geochemistry and chemical composition of clinopyroxene crystals from alban hills pyroclastic deposits constrain the petrological evolution of ultrapotassic roman type rocks volcanic eruptions in the 560 35 ka time interval produced thick pyroclastic deposits bearing clinopyroxene phenocrysts with recurrent chemical characteristics clinopyroxenes vary from si mg rich to al fe rich with no compositional break indicating that they were derived from a continuous process of crystal fractionation based on the 18o and trace element data no primitive samples were recovered monomineralic clinopyroxene cumulates set the oxygen isotope composition of primary magmas in the range of uncontaminated mantle rocks 5 5 but their ree composition resulted from extensive crystal fractionation departing from these mantle like 18ocpx values the effects of crustal contamination of clinopyroxene o isotope composition were identified and used to monitor chemical variations in the parental magma 18o values in si mg rich clinopyroxene are slightly higher than typical mantle values 5 9 6 2 and the low ree contents are representative of early stages of magmatic differentiation 18o values as high as 8 2 are associated with al fe3 rich clinopyroxene showing high ree contents these 18o values are characteristic of crystals formed during the late magmatic stages of each main eruptive phase geochemical modelling of 18o values vs trace element contents indicates that these ultrapotassic magmas were derived from fractional crystallization plus assimilation of limited amounts of carbonate wall rocks starting from a primary melt and from interaction with co2 derived from country rocks during crystal fractionation

retrieval of moho reflected shear wave arrivals from ambient seismic noise theoretical studies on ambient seismic noise asn predict that complete green s function between seismic stations can be retrieved from cross correlation however only fundamental mode surface waves emerge in most studies involving real data here we show that moho reflected body wave sms and its multiples can be identified with asn for station pairs near their critical distances in the short period band 1 5 s we also show that an uneven distribution of noise sources such as mining activity and wind topography interaction can cause surface wave precursors which mask weaker body wave phases

cyclical slope instability and volcanism related to volcano tectonism in resurgent calderas the ischia island italy case study abstract the results of a detailed stratigraphic study carried out in the areas located to the east and south west of mt epomeo at ischia are presented and compared with those of previous geological archaeological and historical investigations to show the relationships among caldera resurgence volcanism and slope instability in the past 5 5 ka resurgence at ischia began at about 30 ka b p and occurred through intermittent uplifting and tectonic quietness phases during the past 5 5 ka reactivation of faults and related volcanic activity was accompanied by emplacement of deposits generated by surface gravitational movements these deposits were generated in four main phases dated between 5 5 and 2 9 ka around 2 9 ka between 2 6 and 2 3 ka and between 2 3 and 1 9 ka respectively deposits formed by gravitational movements preceded and followed the emplacement of volcanic rocks testifying that slope instability was induced by vertical movements which also activated and or reactivated faults and fractures that fed volcanism the results of this study therefore suggest that although slope failure can occur as a consequence of a variety of factors resurgence has to be considered a factor inducing a particularly intense slope instability resurgence is accompanied by activation of faults and renewal of volcanism causing oversteepening of the slopes and generating seismicity that could trigger surface gravitational movements furthermore the availability of large amount of loose material rapidly accumulated along the slopes during eruptions favors landslide generation

major end moraines of younger dryas age on wollaston peninsula victoria island canadian arctic implications for paleoclimate and for formation of hummocky moraine some of the most extensive and massive end moraines of younger dryas age 11 10 14c ka bp yet recognized in north america occur on wollaston peninsula of victoria island on the western part of the peninsula numerous closely spaced end moraines formed in the interval starting 11 100 100 radiocarbon years ago and ending about 10 500 10 200 years ago net recession was generally slow throughout and was punctuated by moraine building and at least two readvances recession is mapped with a resolution that is approximately decadal the moraines form an orderly nested succession and are consistently associated with westward shedding of meltwater which formed a sequence of marine limit deltas we lack firm independent proxy climate evidence needed to assess whether these moraines formed because of cold younger dryas climate rather than because of controls such as topographic setting and water depth but climatic control seems probable the moraines evidently retain glacier ice cores as do most similarly

the deep magmatic system of the campi flegrei caldera italy 1 melt inclusions in phenocrysts of the minopoli2 shoshonite and fondo riccio latite eruptive products campi flegrei caldera 10 2 to 9 5 ka bp constrain the nature of deep phlegraean magmatic fluids their role in volcanism and give new insights into the magmatic plumbing system the analyzed melt inclusions show that co2 is an abundant gaseous species confirming the results of geochemical studies on the magmatic gas fraction involved in present day fumarolic emissions volatile concentrations within the melt inclusions require gas melt equilibria between 8 and 9 km depth and closed system degassing in presence of ascending co2 rich fluids of deep provenance magmas later re equilibrate at depths up to 3 2 km i e above the top of the carbonate basement these observations correlate well with independent geophysical and geochemical evidence and are useful constraints for volcanic hazards assessment at campi flegrei

the averno 2 fissure eruption a recent small size explosive event at the campi flegrei caldera italy the averno 2 eruption 3 700 50 a b p was an explosive low magnitude event characterized by magmatic and phreatomagmatic explosions generating mainly fall and surge beds respectively it occurred in the western sector of the campi flegrei caldera campanian region south italy at the intersection of two active fault systems oriented ne and nw the morphologically complex crater area largely filled by the averno lake resulted from vent activation and migration along the ne trending fault system the eruption generated a complex sequence of pyroclastic deposits including pumice fall deposits in the lower portion and prevailing surge beds in the intermediate upper portion the pyroclastic sequence has been studied through stratigraphical morphostructural and petrological investigations and subdivided into three members named a through c member a was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km during this phase the eruption reached its climax with a mass discharge rate of 3 2 106 kg s intense fracturing and fault activation favored entry of a significant amount of water into the system which produced explosions driven by variably efficient water magma interaction these explosions generated wet to dry surge deposits that emplaced member b and c respectively isopachs and isopleths maps as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a ne oriented 2 km long fissure the total volume of magma extruded during the eruption has been estimated at about 0 07 km3 dre the erupted products range in composition from initial weakly peralkaline alkali trachyte to last emplaced alkali trachyte isotopic data and modeling suggest that mixing occurred during the averno 2 eruption between a more evolved less radiogenic stored magma and a less evolved more radiogenic magma that entered the shallow reservoir to trigger the eruption the early phases of the eruption during which the vent migrated from sw to the center of the present lake were fed by the more evolved uppermost magma while the following phases extruded the less evolved lowermost magma integration of the geological and petrological results suggests that the averno 2 complex eruption was fed from a dyke shaped shallow reservoir intruded into the ne sw fault system bordering to the west the la starza resurgent block within the caldera floor

enrichment of basalt and mixing of dacite in the rootzone of a large rhyolite chamber inclusions and pumices from the rattlesnake tuff oregon a variety of cognate basalt to basaltic andesite inclusions and dacite pumices occur in the 7 ma rattlesnake tuff of eastern oregon the tuff represents 280 km3 of high silica rhyolite magma zoned from highly differentiated rhyolite near the roof to less evolved rhyolite at deeper levels the mafic inclusions provide a window into the processes acting beneath a large silicic chamber quenched basaltic andesite inclusions are substantially enriched in incompatible trace elements compared to regional primitive high alumina olivine tholeiite haot lavas but continuous chemical and mineralogical trends indicate a genetic relationship between them basaltic andesite evolved from primitive basalt mainly through protracted crystal fractionation and multiple cycles 10 of mafic recharge which enriched incompatible elements while maintaining a mafic bulk composition the crystal fractionation history is partially preserved in the mineralogy of crystal rich inclusions olivine plagioclase clinopyroxene and the recharge history is supported by the presence of mafic inclusions containing olivines of fo80 small amounts of assimilation 2 of high silica rhyolite magma improves the calculated fit between observed and modeled enrichments in basaltic andesite and reduces the number of fractionation and recharge cycles needed the composition of dacite pumices is consistent with mixing of equal proportions of basaltic andesite and least evolved high silica rhyolite in support of the mixing model most dacite pumices have a bimodal mineral assemblage with crystals of rhyolitic and basaltic parentage equilibrium dacite phenocrysts are rare dacites are mainly the product of mingling of basaltic andesite and rhyolite before or during eruption and to a lesser extent of equilibration between the two the rattlesnake magma column illustrates the feedback between mafic and silicic magmas that drives differentiation in both low density rhyolite traps basalts and induces extensive fractionation and recharge that causes incompatible element enrichment relative to the primitive input the basaltic root zone in turn thermally maintains the rhyolitic magma chamber and promotes compositional zonation

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

source location of the 26 sec microseism from cross correlations of ambient seismic noise 1 very strong narrow band rayleigh wave arrivals peaking near 26 sec are observed in cross correlations of long time sequences of ambient noise records on us european and african stations with apparent arrival times that are typically smaller than expected for propagation along the great circle linking the stations use of these apparent travel times to locate the source of narrow band arrivals shows that the waves originate off the west african coast in the gulf of guinea and propagate with an average speed of about 3 5 km s i e close to the expected group speed of rayleigh waves at this period using data from different months demonstrate that the source location is temporally stable with amplitudes that maximize during the southern hemisphere winter a microseism with similar features but with a slightly broader spectral peak is observed at stations in east asia and in the western pacific and apparently originates in the north fiji basin the nearly antipodal location of the two source regions leads to the hypothesis that the 26 sec signals are excited by a single source located in the gulf of guinea the pacific inter station cross correlations may be for major arc propagation

the generation of overpressure in felsic magma chambers by replenishment abstract evidence of magma mixing is common in the products of explosive felsic eruptions and it is generally accepted as a common mechanism for triggering such events in order to quantify the potential for magma mixing to trigger explosive eruptions we have developed a simple analytical model based on previous models of magma chamber replenishment which considers the injection of volatile rich mafic magma into a chamber occupied by a homogeneous volatile rich felsic magma we assume that the overpressure caused by the injection of new magma is not sufficient to trigger an eruption for which additional overpressure is required two mixing related mechanisms have traditionally been considered to have the potential to generate the additional overpressure 1 exsolution of volatiles from the felsic magma during forced convection and 2 exsolution of volatiles from the mafic magma by oversaturation during cooling and subsequent crystallization our calculations suggest that exsolution of volatiles from the felsic magma is not an effective mechanism to generate additional overpressure however significant overpressure can be achieved by volatile exsolution from the mafic magma during its cooling and crystallization the time scale between intrusion and eruption considered in our model is of the order of a few days to a few months which coincides with petrological and geophysical evidence obtained from magma mixing related eruptions we also suggest that replenishment of shallow felsic magma chambers by mafic magma in most cases does not lead to large scale mixing as eruption will occur before thermal equilibrium between the two magmas is reached so that density and viscosity contrasts between the two magmas will remain significant

new insights into late pleistocene explosive volcanic activity and caldera formation on ischia southern italy a new pyroclastic stratigraphy is presented for the island of ischia italy for the period 75 50 ka bp the data indicate that this period bore witness to the largest eruptions recorded on the island and that it was considerably more volcanically active than previously thought numerous vents were probably active during this period the deposits of at least 10 explosive phonolite to basaltic trachyandesite eruptions are described and interpreted they record a diverse range of explosive volcanic activity including voluminous fountain fed ignimbrite eruptions fallout from sustained eruption columns block and ash flows and phreatomagmatic eruptions previously unknown eruptions have been recognised for the first time on the island several of the eruptions produced pyroclastic density currents that covered the whole island as well as the neighbouring island of procida and parts of the mainland the morphology of ischia was significantly different to that seen today with edifices to the south and west and a submerged depression in the centre the largest volcanic event the monte epomeo green tuff megt resulted in caldera collapse across all or part of the island it is shown to comprise at least two thick intracaldera ignimbrite flow units separated by volcaniclastic sediments that were deposited during a pause in the eruption extracaldera deposits of the megt include a pumice fall deposit emplaced during the opening phases of the eruption a widespread lithic lag breccia outcropping across much of ischia and procida and a distal ignimbrite in south west campi flegrei during this period the style and magnitude of volcanism was dictated by the dynamics of a large differentiated magma chamber which was partially destroyed during the megt eruption this contrasts with the small volume holocene and historical effusive and explosive activity on ischia the timing and distribution of which has been controlled by the resurgence of the monte epomeo block the new data contribute to a clearer understanding of the long term volcanic and magmatic evolution of ischia

technological examination of neolithic bronze age pottery from central and southeast europe and from the near east abstract scanning electron microscopy is used to examine sequences of pottery sherds from central and southeast europe greece and the near east spanning the period from the neolithic to the bronze age in order to obtain information on the ceramic technologies employed in antiquity on the basis of the vitrification observed and the chemical composition the types of clay and firing procedures temperature and atmosphere employed in the manufacture of the pottery are defined two under lying trends in the associated ceramic technologies are thus identified the first is based on the use of non calcareous or unstable calcareous clays fired in a reducing atmosphere at temperatures below 800 c and the second on the use of stable calcareous clays fired in an oxidizing atmosphere at temperatures in excess of 800 c

sr nd isotopic fingerprinting as a tool for ceramic provenance its application on raw materials ceramic replicas and ancient pottery abstract the potentiality of isotope analysis has largely been explored in archaeological sciences to date objects attribute their provenance and depict ancient human dietary habits however the potential of this technique for provenance studies of ancient ceramics has barely been explored due to the fact that the ceramic process often involves the selection of different raw materials and consequently different sources of radiogenic isotopes in this paper 87sr 86sr and 143nd 144nd isotope ratios were measured on raw materials clays and volcanic temper that were exploited in antiquity for producing pottery in the campania region of italy and for the first time on experimental ceramic materials that replicate archaeological pottery to validate the method sr and nd isotope ratios were also measured on selected archaeological pottery from cuma the results of this pioneering approach clearly show that the synthetic mixtures used for the ceramic replicas plot exactly on the theoretical mixing curve between the clay and volcanic temper end members on the other hand technological processes employed during pottery manufacturing such as firing and levigation induce no significant variations in sr and nd isotope ratios isotope characterisation represents an effective fingerprint of pottery that strictly depends on the geochemical affinity of the raw materials thus providing a better discrimination among different ceramic productions

geomorphology as science the role of theory abstract because geomorphology is a science it is permeated by theory overt recognition of this actuality is frequently resisted by geomorphologists earth history does not represent an alternative to earth science it is an essential component of earth science in its broadest sense science seeks to discover new knowledge through a two stage activity involving the creation and justification of ideas theory deduction is generally regarded as the only logically consistent method of justifying ideas the creation of ideas is a much more controversial topic some methodologists deem it beyond logic certainly deductive arguments which are nothing more than formal logical expressions of theory play no role in the conception of new ideas many earth scientists generate possible explanations of observed phenomena based on abductive reasoning others advocate reliance on purported forms of pure induction such as serendipity and intuition in which observations assume primacy over theory besides lacking consistency and educability the latter posture is flawed because it mistakenly implies that becoming well versed in theory is irrelevant to or impedes scientific discovery irrational or subjective factors play a role in the creation of ideas but it is erroneous to claim that these factors are divorced from theory science is first and foremost a cognitive activity thus the primacy of observations in science is a myth all observations are theory laden in the sense that the act of observation inherently involves interpretation and classification both of which can only occur within the context of theoretical preconceptions even discoveries based on unexpected observations require the fortunate investigator to recognize the theoretical importance of what is seen or measured the most useful view of geomorphology as a science is one in which theory is seen as central but fragile and in which theory and observation are viewed symbiotically with theory providing the generative force and observation providing a vital policing role much of the current debate in geomorphology centers around differences in characteristics of theory type of scientific arguments and metaphysical perspectives among investigators working at different temporal scales full recognition and understanding of these differences are essential for developing a unified approach to the science of geomorphology

grain size and srnd isotopes as tracer of paleo bottom current strength northeast atlantic ocean abstract a crucial question in modern paleoceanographic research is how vigourous was the bottom current in the glacial north atlantic ocean distribution of sediment grain size can provide such information if the characteristics of the source functions are known the interest of this paper is to use the sr nd isotopic composition of lithic particles as a tracer of origin in order to determine possible changes in the source function over the last 185 kyr grain size distribution data are derived from a sediment core in the icelandic basin gardar drift the distribution pattern reveals a well sorted silt size modal size 20 m in the glacial deposits sr and nd isotopic composition measured on separate size fractions indicates a more constant local origin iceland for the silt fraction than for the fine fraction these data suggest that the increase in the silt fraction during glacial periods is related primarily to an increase in the bottom current strength rather than to changes in sediment supply i e ice rafting turbidity current the increase in vigour of the bottom current recorded during the isotopic stages 6 4 and the last post glacial periods could have been initiated by a southward shift of the zone of deep water formation in the northern part of the icelandic basin

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

river adjustment to changes in sediment load the effects of tin mining on the ringarooma river tasmania 1875 1984 the mining of alluvial tin in the ringarooma basin began in 1875 reached a peak in 1900 20 and had virtually ceased by 1982 during that time 40 million m3 of mining waste were supplied to the main river quickly replacing the natural bed material and requiring major adjustments to the channel based on estimates of sediment supply from more than 50 widely scattered mines and the frequency of flows capable of transporting the introduced load the river s transport history is reconstructed using a mass conservation model because of the lengthy time period 110 years and river distance 75 km involved the model cannot predict detailed change but it does reproduce the main pattern of sediment movement in which successive phases of aggradation and degradation progress downstream peak storage is predicted in that part of the river where braiding and anastomosis are best developed aggradation was most rapid in the upper reaches close to major supply points becoming slower and later with distance downstream channel width increased by up to 300 per cent where the valley floor was broad and braiding became relatively common bridges had frequently to be replaced while bed levels were still rising in lower reaches degradation began in upper ones notably after 1950 and by 1984 had progressed downriver over 30 km rates of incision reached 0 5 m yr 1 especially in the early 1970s when record high flows occurred as a result of degradation the bed material became gravelly through either reexposure of the original bed or lag concentration of coarser fractions also a narrower unbraided channel has developed the river is beginning to heal itself and upper reaches now have reasonably stable beds but at least another 50 years will be required for the river to cleanse its channel of mining debris

the restless resurgent campi flegrei nested caldera italy constraints on its evolution and configuration abstract we have collected new stratigraphic data in the campi flegrei caldera through surface geological mapping and study of cores drilled to various depths we integrate these data with geological geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera the caldera is a resurgent nested structure resulting from two main collapses related to the campanian ignimbrite 37 ka and the neapolitan yellow tuff 12 ka eruptions while the structure is affected by a broad subsidence ongoing local resurgence and unrest occur inside the younger nested caldera structure although most of the caldera floor consists of multiple structural blocks due to long term deformations magmas were able to erupt only in one sector of the resurgent part the caldera has shown signs of unrest during the past 25 years with short term deformations that have generated a net uplift of 3 5 m the short term deformations are related to the neapolitan yellow tuff caldera resurgence and interpreted as the net result of brittle and ductile components the long term deformations likely represent the sum of the permanent brittle component of each short term deformational event

shallow crustal velocities and volcanism suggested from ambient noise studies using a dense broadband seismic network in the tatun volcano group of taiwan abstract the tatun volcano group tvg is situated adjacent to the taipei metropolis and was active predominantly around 0 8 0 2 ma pleistocene various recent lines of evidence suggest that the tvg is a potentially active volcano and that future volcanic eruptions cannot be ruled out geothermal activities are largely constrained to faults but the relationship between volcanism and detailed velocity structures is not well understood we analyzed ambient seismic noise of daily vertical components from 2014 using a dense seismic network of 40 broadband stations we selected a 0 02 grid spacing to construct 2d and 3d shallow crustal phase velocity maps in the 0 5 3 s period band two s wave velocity profiles transect chishingshan mt cs in the shallow 3 km crust are further derived the footwall of the shanchiao fault is dominated by low velocity which may relate to tertiary bedrock buried under andesitic lava flows dozens to hundreds of meters thick the hanging wall of the shanchiao fault is the location of recent major volcanic activities low velocity zones in the southeast of dayoukeng dyk may be interpreted as hydrothermal reservoirs or water saturated tertiary bedrock related to cenozoic structures in the shallow crust high velocities conspicuously dominate the east of the tvg where the earliest stages of volcanism in the tvg are located but where surface hydro geothermal activities were absent in recent times between the shanchiao fault and kanchiao fault high velocities were detected which converge below mt cs and may be related to early stages of magma conduits that gradually consolidated these two faults may play a significant role with the tvg the submarine volcanism adjacent to the keelung coastline also requires further attention

a persistent localized microseismic source near the kyushu island japan 1 very strong signals with apparent velocity higher than rayleigh wave velocity are observed on noise correlation functions ncfs between seismic stations in east asia these signals are present on one month ncfs in ten years period with stable arrival times indicating their persistent and localized nature the signals are strong in the frequency band of 0 07 0 12hz and their amplitudes show inter annual but not seasonal variation location obtained from two algorithms with gsn and fnet data indicates that the source is situated in kyushu island japan after an earthquake is used to account for heterogeneity effects the location is closer to the ariake bay but still in the island the non seasonal amplitude variation and the peak frequency of 0 1hz suggest the signals are probably not generated by oceanic sources this persistent localized microseismic source needs to be taken into consideration in ambient noise tomography studies in east asia

a model for ischia hydrothermal system evidences from the chemistry of thermal groundwaters abstract ischia volcano in central italy has long been known for its copious surface hydrothermal manifestations signs of a pervasive circulation of hot fluids in the subsurface because of the significant chemical heterogeneity of fumarolic gas discharges and hot spring discharges evidences of a complex hydrothermal setting a definite model of fluid circulation at depth is currently unavailable in spite of the several previous efforts here we report on the chemical and isotopic composition of 120 groundwater samples collected during several sampling surveys from 2002 to 2007 the acquired data suggest that the composition of surface manifestations reflect contributions from meteoric water sea water and thermal fluids rising from two distinct hydrothermal reservoir with equilibrium temperatures of respectively 150 c and 270 c and depths of 150 300 m and 300 m but possibly 1000 m we also make use of an isotopic characterization of the dissolved gas phase in thermal waters to demonstrate that the ischia hydrothermal system is currently supplied by a deep rising gas component dgc characterized by co2 97 7 1 2 vol on a water free basis 13cco2 3 51 0 9 and helium isotopic ratio of about 3 5 ra 3he 4he ratio normalized to the air ratio ra likely magmatic in origin an assessment of the thermal budget for ischia hydrothermal system is also presented in the attempt to derive a first estimate of the size and rate of degassing of the magmatic reservoir feeding the gas emissions we calculate that a heat flow of about 153 222 mw presently drives hydrothermal circulation on the island which we suggest is supplied in convective form e g by the ascent of a high t magmatic vapour phase by complete degassing of 2 2 3 3 107 m3 yr 1 of trachytic magma with 2 1 wt dissolved h2o content if extrapolated to entire period of quiescence lasting since the arso eruption in 1302 a d this volume corresponds to 1 6 2 3 1010 m3 of magma degassed in about 700 years of quiescent activity

modelling curved surface wave paths membrane surface wave synthetics summary earth s heterogeneity near the surface is so severe that surface waves with period 20 s exhibit complicated propagation effects such as curved paths and multiple rays in order to take account of these effects a new method to analyse surface waves is developed the method which we call the membrane surface wave method is an approximation to the green s function method in a 3 d medium and is valid for a laterally smoothly varying media we also present the formulae to invert the seismograms as an example we apply the method to a preliminary california model use of the method for the forward calculation shows that heterogeneity in the model is so severe that the wavefront due to the whittier narrows earthquake is split in two by the time it reaches the san francisco bay area the kernels in the inverse formula to the six berkeley stations show curved paths multipathings and finite wavelength effects and visually demonstrate how waves sample the medium the method is attractive in that these complications cause no problems in its application

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

magma mixing at lipari aeolian islands italy insights from textural and compositional features of phenocrysts in southern lipari aeolian islands italy the volcanic activity was exclusively rhyolitic in the last 42 ka but the presence of mafic magmas in the magmatic system is revealed by the occurrence of mingling and mixing textures in the silicic deposits the study of textural and compositional zoning of phenocrysts is a powerful tool to unravel magmatic processes especially when bulk rock data are affected by magma mixing in this work we present the results of detailed petrographic and microanalytical investigations carried out on the rhyolitic products and their mafic enclaves with the aim to improve the knowledge of the lipari magmatic system in recent times trace element profiles on phenocrysts were carried out by laser ablation icp ms on the products of eruptions occurred around 22 ka ago mineral chemistry indicated the formation of different mafic magma batches in that period zoning patterns in clinopyroxene and plagioclase phenocrysts in enclaves record mixing between two different mafic magmas this event preceded of less than a few years the syn eruptive mixing with the rhyolite short residence times less than hundreds of years of plagioclase phenocrysts in the mafic magma prior to mixing with the rhyolite were calculated based on measured sr profiles and diffusion kinetics the results evidence the existence in southern lipari of a composite vertically developed magmatic system storing silicic and mafic magmas as relatively small volume batches interacting with each other

isotopic evidence for open system processes within the campanian ignimbrite campi flegrei italy magma chamber new sr and nd isotope data for whole rocks glasses and minerals are combined to reconstruct the nature and origin of mixing end members of the 200 km3 trachytic to phonolitic campanian ignimbrite campi flegrei italy magmatic system the least evolved magmatic end member shows equilibrium between host glass and the majority of the phenocrysts and is less radiogenic in sr and nd than the most evolved magma on the contrary only the fe rich pyroxene from the most evolved erupted magma is in equilibrium with the matrix glass while all other minerals are in isotopic disequilibrium these magmas mixed prior to and during the campanian ignimbrite eruption and minerals were freely exchanged between the magma batches combining the results of the geochemical investigations on magma end members with geophysical and geological data we develop the following scenario in stage 1 a parental less differentiated magma rose into the middle crust and evolved through combined crustal assimilation and crystal fractionation in stage 2 the differentiated magma rose to shallower depth fed the pre campanian ignimbrite activity and evolved by further open system processes into the most evolved and most radiogenic campanian ignimbrite end member magma in stage 3 new trachytic magma isotopically distinct from the pre campanian ignimbrite magmas rose from ca 6 km to shallower depth recharged the most evolved pre campanian ignimbrite magma chamber and formed the large and stratified campanian ignimbrite magmatic system during the course of the campanian ignimbrite eruption the two layers were tapped separately and or simultaneously and gave rise to the range of chemical and isotopic values displayed by the campanian ignimbrite pumices glasses and minerals

remobilization of highly crystalline felsic magma by injection of mafic magma constraints from the middle sixth century eruption at haruna volcano honshu japan the latest eruption of haruna volcano at futatsudake took place in the middle of the sixth century starting with a plinian fall followed by pyroclastic flows and ending with lava dome formation gray pumices found in the first plinian phase lower fall and the dome lavas are the products of mixing between felsic andesitic magma having 50 vol phenocrysts and mafic magma the mafic magma was aphyric in the initial phase whereas it was relatively phyric during the final phase the aphyric magma is chemically equivalent to the melt part of the phyric mafic magma and probably resulted from the separation of phenocrysts at their storage depth of 15 km the major part of the felsic magma erupted as white pumice without mixing and heating prior to the eruption after the mixed magma gray pumice and heated felsic magma white pumice of the lower fall deposit although the mafic magma was injected into the felsic magma reservoir at 7 km depth part of the product lower fall ejecta preceded eruption of the felsic reservoir magma as a consequence of upward dragging by the convecting reservoir of felsic magma the mafic magma injection made the nearly rigid felsic magma erupt letting low viscosity mixed and heated magmas open the conduit and vent indeed the lower fall white pumices preserve a record of syneruptive slow ascent of magma to 2 km depth probably associated with conduit formation

a complex magma mixing origin for rocks erupted in 1915 lassen peak california the eruption of lassen peak in may 1915 produced four volcanic introduction rock types within 3 days and in the following order 1 hybrid magma mixing is an important process among interblack dacite lava containing 2 undercooled andesitic inclusions mediate magmas in volcanic arcs e g turner 3 compositionally banded pumice with dark andesite and light campbell 1986 philpotts 1990 and references therein dacite bands and 4 unbanded light dacite all types represent laboratory studies of synthetic analogs of silicate magma stages of a complex mixing process between basaltic andesite systems and mathematical modeling of mixing viscous and dacite that was interrupted by the eruption they contain liquids have suggested a range of possible mixing mechdisequilibrium phenocryst assemblages characterized by the coanisms e g cashman bergantz 1991 however use existence of magnesian olivine and quartz and by reacted and of these results to interpret magmatic systems is limited unreacted phenocrysts derived from the dacite the petrography and by the applicability of synthetic analogs to magmatic crystal chemistry of the phenocrysts and the variation in rock conditions and by the imprecise knowledge of the effective compositions indicate that basaltic andesite intruded dacite magma viscosity of silicate liquid crystal mixtures at magmatic and partially hybridized with it phenocrysts from the dacite magma temperatures and pressures if magmas mix incompletely were reacted cooling crystallization and vesiculation of the hybrid i e mingle features such as compositional banding or andesite magma converted it to a layer of mafic foam the decreased undercooled inclusions are usually apparent but if they density of the andesite magma destabilized and disrupted the foam mix completely mineralogical disequilibrium may be the blobs of foam rose into and were further cooled by the overlying dacite magma forming the andesitic inclusions disaggregation of only direct evidence for a mixing origin andesitic inclusions in the host dacite produced the black dacite and if the thermal and compositional contrasts between light dacite magmas formation of foam was a dynamic process two magmas are great and the ratio of silicic to mafic removal of foam propagated the foam layer downward into the magma is large there is little interaction between them hybrid andesite magma eventually the thermal and compositional and the mafic magma is undercooled e g bacon 1986 contrasts between the hybrid andesite and black dacite magmas were many undercooled inclusions contain reacted phereduced then they mixed directly forming the dark andesite magma nocrysts inherited from their host silicic magma heiken about 40 50 andesitic inclusions were disaggregated into the eichelberger 1980 and bacon 1986 pointed out host dacite to produce the hybrid black dacite thus disaggregation that undercooled inclusions are typically formed from of inclusions into small fragments and individual crystals can be hybrid magmas in general the formation of undercooled an efficient magma mixing process disaggregation of undercooled inclusions retards further mixing sakuyama 1984 inclusions carrying reacted host magma phenocrysts produces cothompson dungan 1985 sparks marshall 1986 existing reacted and unreacted phenocryst populations koyaguchi blake 1991 however fragmentation and or disaggregation of undercooled inclusions plays an important role in hybridization in some magma systems thompson dungan 1985 coulon et al 1986 clynne christiansen 1987 clynne 1989 linneman myers

locating a scatterer in the active volcanic area of southern peru from ambient noise cross correlation we report on a strong scatterer of seismic energy in the 5 10 s period range located in the volcanic arc of southern peru it is superficially like an active noise source in that it produces a continuous signal that arrives earlier than the inter station surface wave in the noise cross correlations however it is clearly determined to be a scatterer based on the coda arrivals observed in the cross correlations and the fact that it scatters waves from earthquake sources we model the scatterer as a cylinder approximately 5 km in diameter with a shear wave velocity 30 per cent lower than the background velocity it is likely to exist at the depth of 5 10 km and is located at 71 6 w 16 1 s with an error of 10 km which is near the inactive volcano nevado chachani and the active volcano el misti which recently erupted in 1985

statistical models of fluvial systems abstract statistical methods have dominated quantitative analyses of fluvial systems over the last 40 years this paper assesses the utility of statistical models by examining methodological issues associated with empirical analysis of hydraulic and channel geometry relationships it also describes and presents examples of advanced statistical models that promise to enhance our understanding of the structure and dynamics of fluvial systems bivariate and multivariate power function models of fluvial systems provide objective numerical descriptions of the relationship between channel geometry and hydrologic hydraulic sedimentologic and biotic controls traditional regression models are limited in that they only describe simple input output relations between the states of dependent and independent variables advanced statistical models transcend these limitations simultaneous equation models continuously varying parameter models and distributed lag models are statistical tools for explicitly analyzing 1 mutual adjustments among fluvial variables 2 the factors controlling the spatial structure of channel geometry flow relations and 3 the equilibrium or disequilibrium dynamics of fluvial systems respectively these advanced statistical techniques can be used to empirically test conceptual models of fluvial systems at a variety of spatial and temporal scales

crust and uppermost mantle beneath the north china craton northeastern china and the sea of japan from ambient noise tomography 1 a 3 d shear velocity model of the crust and uppermost mantle to a depth of 100 km is presented beneath the north china craton ncc northeastern china the korean peninsula and the sea of japan ambient noise rayleigh wave tomography is applied to data from more than 300 broadband seismic stations from chinese provincial networks cearray the japanese f net and the iris global seismic network continuous data from 2007 to 2009 are used to produce group and phase velocity maps from 8 s to 45 s periods the model is motivated to constrain the distributed intraplate volcanism crustal extension cratonic rejuvenation and lithospheric thinning that are hypothesized for the study region numerous robust features are observed that impose new constraints on the geometry of these processes but discussion concentrates only on four 1 the north south gravity lineament follows the 40 km contour in crustal thickness and crustal thickness is anticorrelated with water depth beneath the sea of japan consistent with crustal isostasy for a crust with laterally variable composition 2 the lithosphere is thin 70 km beneath the songliao bohai graben but seismically fast 3 even thinner more attenuated lithosphere bounds three sides of the eastern ncc in a horseshoe shape identifying a region of particularly intense tectonothermal modification where lithospheric rejuvenation may have reached nearly to the base of the crust 4 low velocity anomalies reach upward in a y shape in the mantle beneath the eastern and western borders of the sea of japan extending well into continental east asia in the west and are separated by a 60 km thick lithosphere beneath the central sea of japan this anomaly may reflect relatively shallow slab dehydration in the east and in the west may reflect deeper dehydration and convective circulation in the mantle wedge overlying the stagnant slab

landform signature of the laurentide and cordilleran ice sheets across alberta during the last glaciation government geological survey maps and research publications have portrayed the distribution of glacial landforms associated with the advance and retreat of the laurentide and cordilleran ice sheets across alberta at a local regional and continental scale to date this information has not been systematically synthesized into a single compilation at a consistent scale although this original work provided valuable information to constrain reconstructions of former ice sheet extent configuration and flow geometry its derivation primarily from the interpretation of aerial photographs and the shuttle radar topography mission 90 m digital elevation model dem may result in methodological inconsistencies and spatial biases these biases together with challenges associated with geomorphic mapping in densely forested areas of western and northern alberta limit the usefulness of previous mapping when applied to inversion based ice sheet reconstructions which have specific input data demands recently ligh

time dependent geochemistry of clinopyroxene from the alban hills central italy clues to the source and evolution of ultrapotassic magmas abstract we investigated chemical and isotopic compositions of clinopyroxene crystals from well age constrained juvenile scoria clasts lava flows and hypoabyssal magmatic ejecta representative of the whole eruptive history of the alban hills volcanic district the alban hills is a quaternary ultra potassic district that was emplaced into thick limestone units along the tyrrhenian margin of italy alban hills volcanic products even the most differentiated are characterised by low sio2 content we suggest that the low silica activity in evolving magmas can be ultimately due to a decarbonation process occurring at the magma limestone interface according to the liquid line of descent we propose the differentiation process is driven by crystallisation of clinopyroxene leucite apatite magnetite coupled with assimilation of a small amount of calcite and or with interaction with crustal co2 by combining age chemical data strontium and oxygen isotopic compositions and ree content of clinopyroxene we give insights into the evolution of primitive ultrapotassic magmas of the alban hills volcanic district over an elapsed period of about 600 kyr geochemical features of clinopyroxene crystals consistent with data coming from other italian ultrapotassic magmas indicate that alban hills primary magmas were generated from a metasomatized lithospheric mantle source in addition our study shows that the 87sr 86sr and lree hree of alban hills magmas continuously diminished during the 600 35 ka time interval of the alban hills eruptive history possibly reflecting the progressive depletion of the metasomatized mantle source of magmas

relationships between intermediate and acidic rocks in orogenic granitoid suites petrological geochemical and isotopic sr nd pb data from capo vaticano southern calabria italy abstract major trace element and isotopic data are reported for hercynian granodiorites and tonalites from capo vaticano calabria with the aim of clarifying the relationships between acidic and intermediate lithologies in orogenic intrusive suites these granodiorites sio 2 70 5 73 5 are peraluminous relatively depleted in rb u th and pb and display a large variation in many geochemical and isotopic parameters ree show fractionated cross cutting chondrite normalized patterns with small but significant negative eu anomalies initial 290 ma sr and nd and present day pb isotope ratios are 87 sr 86 sr 290 0 7105 0 7110 143 nd 144 nd 290 0 51175 0 51221 206 pb 204 pb 18 35 18 50 207 pb 204 pb 15 64 15 76 208 pb 204 pb 38 51 39 03 pb isotope ratios determined for separated feldspars show similar 207 pb 204 pb and 208 pb 204 pb and higher 207 pb 204 pb ratios compared to the present day values for the whole rock the tonalites sio 2 57 6 67 3 are typically calc alkaline in composition and most of them are weakly peraluminous they display large heterogeneities in trace element abundances ree patterns and nd and pb isotope ratios both between and within individual intrusive units sr nd and pb isotopic compositions display a range of values close to that of the associated granodiorites 87 sr 86 sr 290 0 7099 0 7111 143 nd 144 nd 290 0 51185 0 51224 206 pb 204 pb 18 31 18 56 207 pb 204 pb 15 65 15 72 208 pb 204 pb 38 41 39 59 the obtained data indicate that the tonalites and granodiorites share many compositional features which point to a genetic linkage likewise many petrological geochemical and field data exclude the possibility that all the granodiorites derive from intermediate magmas by any common evolutionary process such as crystal liquid fractionation or assimilation fractional crystallization afc and point to a different genesis for the two rock types an origin of the granodiorites by the mixing of two separate acidic melts one of crustal anatectic origin and one probably derived from an intermediate magma by crystal liquid fractionation or afc is suggested by the data presented the tonalites appear to have been generated by interaction of a mafic magma with crustal end member s with isotopic and geochemical signatures similar to those of the granodiorites the large involvement of crustal material in the genesis of the capo vaticano granitoids is responsible for the many common compositional characteristics observed in the intermediate and acidic rocks however a contribution from mantle components is also indicated by petrological and geochemical data as well as by the occurrence of mafic enclaves commonly present in the tonalites nevertheless the geochemical and isotopic features of such a mantle component appear to be greatly diluted by a large quantity of crustal material involved in the genesis of the studied granitoids

results from a new model of river basin evolution this paper briefly describes a model of the erosional development of catchments and their channel networks the model differentiates between the dominant transport processes in hillslope and channels the development of channels and hillslopes occurs in an integrated manner as a function of physically observable mechanisms the growth of a river basin is qualitatively described the model concepts are used to study the basin during periods of growth transient periods as well as during dynamic equilibrium this leads to hypotheses about the relationship between slopes relief tectonic uplift erodability runoff and catchment area it is shown that the model leads to very reasonable and desirable behaviour of hillslopes during retreat and degradation

the crust and uppermost mantle structure of southern peru from ambient noise and earthquake surface wave analysis abstract southern peru is located in the northern central andes which is the highest plateau along an active subduction zone in this region the nazca slab changes from normal to flat subduction with the associated holocene volcanism ceasing above the flat subduction regime we use 6 s to 67 s period surface wave signals from ambient noise cross correlations and earthquake data to image the shear wave velocity v s v structure to a depth of 140 km a mid crust low velocity zone is revealed and is interpreted as partially molten rocks that are part of the andean low velocity zone it is oblique to the present trench and possibly indicates the location of the volcanic arcs formed during the steepening of the oligocene flat slab beneath the altiplano plateau the recently subducted slab beneath the forearc shows a decrease in velocity from the normal to flat subduction regime that might be related to hydration during the formation of the nazca ridge which in turn may contribute to the buoyancy of the flat slab the mantle above the flat slab has a comparatively high velocity which indicates the lack of melting and thus explains the cessation of the volcanism above a velocity contrast from crust to uppermost mantle is imaged across the cusco vilcanota fault system and is interpreted as the boundary between two lithospheric blocks

10s period volcanic tremors observed over a wide area in southwestern japan unusual seismic oscillations with a period of 10 seconds were observed over a wide area of southwestern japan several lines of evidence indicate that the origin of these 10s waves must be around the aso volcano located in the central part of kyushu island japan although a 10s period is unusually long for a volcanic tremor and no corresponding surface activity at the crater was reported by the local observatory the volcanic origin of the tremor is indisputable a further astonishing aspects of the observation is that there exists a strong correlation between the onset of 10s waves observed remotely and cessation of high frequency 1hz volcanic tremors at the aso volcano the aso volcano appears to be trembling with a 10s period without this having been noticed since seismic monitoring of volcanic activity is limited to high frequencies above 1 hz at the most of the volcanoes in the world long period tremors of the type observed here might be a widespread phenomenon that has been overlooked

clinopyroxene phenocrysts with green salite cores in trachybasalts implications for two magma chambers under the kokchetav uhp massif north kazakhstan abstract clinopyroxene phenocrysts in the kokchetav trachybasalts are variable in composition and textures two distinctive cores are recognized diopside cores and green salite cores the diopside cores with mg of 80 90 are mantled by colorless salite rims with mg of 70 80 the green salite cores have especially low mg

14c geochronological constraints for the volcanic history of the island of ischia italy over the last 5000 years abstract the chronology of the most significant eruptions at the island of ischia in the last 5000 years has been studied by means of accelerator mass spectrometry to obtain 14 c data the results are in good agreement with stratigraphical and archeological constraints this allows interpretation of the measured dates as ages of the eruptions which produced the deposits overlying or incorporating the sampled paleosols and charcoal fragments respectively these ages define the timing of volcanism in the last 5000 years suggesting that the recent volcanic activity at ischia is characterized by periods of very intense volcanism alternating to periods of quiescence this timing of the volcanism is correlated with the behaviour of the magmatic system and dynamics of resurgence of the mt epomeo block

seismicity and structure of nazca plate subduction zone in southern peru abstract we define subducting plate geometries in the nazca subduction zone by re locating intra slab earthquakes in southern peru 14 18 s and using previously published converted phase analysis results to clarify the slab geometry and inferred relationships to the seismicity we also provide both p and s wave velocity models of the subducting nazca plate and mantle layer above the slab using double difference tomography to understand upper plate volcanism and subduction zone process the double difference constraints for determining the hypocenters and velocity model ensure high accuracy of the relative location of earthquakes with respect to velocity structure the relocated seismicity shows a smooth contortion in the slab dip transition zone for 400 km between the shallow 30 to flat dipping interface to the northwest and the 30 dipping interface to the southeast we find a significant slab dip difference up to 10 between our results and previous slab models along the profile region sampling the horizontal slab at a depth of 85 95 km robust features in both p and s wave tomography inversions are both arc normal and along arc velocity variations in the arc normal direction all profile results show that the slab velocities beneath the forearc down to a depth of 100 km transition to higher velocities beneath the backarc at 100 140 km depth in the along arc direction velocities of the subducting flat slab are shown to be depressed compared to those of the normal dip slab in addition high shear wave velocities and low vp vs are detected in the mantle layer above the flat slab indicating its cold and dry environment such differences in the velocity structures for the slab and mantle wedge between the two regions may indicate different hydration states which greatly affects the upper plate structure of southern peru

effects of volatiles on mixing in calc alkaline magma systems the intimate mixing between different magmas of disparate densities characteristic of some calc alkaline magma systems is explained by a new mechanism involving the emplacement of a layer of wet undersaturated mafic magma at the base of a magma chamber containing more differentiated magma turbulent transfer of heat between the mafic magma and the overlying magma leads to crystallization and exsolution of volatiles in the lower layer for an initial water content of a few per cent the bulk density of the mafic magma can become equal to that of the overlying magma causing overturning and intimate mixing of the magmas the mechanism is most probable in the low pressure environment of a high level magma chamber

a philosophy of rivers equilibrium states channel evolution teleomatic change and least action principle until recently no universal agreement as to a philosophical or scientific methodological framework has been proposed to guide the study of fluvial geomorphology an understanding of river form and process requires an understanding of the principles that govern the behaviour and evolution of alluvial rivers at the most fundamental level to date the investigations of such principles have followed four approaches develop qualitative unifying theories that are usually untested collect and examine data visually and statistically to define semi quantitative relationships among variables apply newtonian theoretical and empirical mechanics in a reductionist manner resolve the primary flow equations theoretically by assuming maximum or minimum outputs here we recommend not a fifth but an overarching philosophy to embrace all four clarifying and formalising an understanding of the evolution of river channels and iterative directional changes in the context of least action principle lap the theoretical basis of variational mechanics lap is exemplified in rivers in the form of maximum flow efficiency mfe a sophisticated understanding of evolution in its broadest sense is essential to understand how rivers adjust towards an optimum state rather than towards some other because rivers as dynamic contemporary systems flow in valleys that are commonly historical landforms and often tectonically determined we propose that most of the world s alluvial rivers are over powered for the work they must do to remain stable they commonly evolve to expend surplus energy via a variety of dynamic equilibrium forms that will further adjust where possible to maximise their stability as much less common mfe forms in stationary equilibrium this paper 1 shows that the theory of evolution is derived from and applicable to both the physical and biological sciences 2 focusses the development of theory in geomorphology on the development of equilibrium theory 3 proposes that river channels like organisms evolve teleomatically progression towards an end state by following natural laws and iteratively one stage forming the basis for the next towards an optimal end state 4 describes lap as the methodological basis for understanding the self adjustment alluvial channels towards mfe 5 acknowledges that whereas river channels that form within their unmodified alluvium evolve into optimal minimum energy systems exogenic variables such as riparian or aquatic vegetation can cause significant variations in resultant river styles we specifically attempt to address luna leopold s lament in 1994 that no clearly expressed philosophy explains the remarkable self adjustment of alluvial channels

coastal slope terracing and relative sea level changes deductions based on computer simulations although a traditional geological survey of terraced coastal slopes is an essential part of studies aimed to reconstruct relative sea level changes the stratigraphic and chronological data so obtained frequently prove inadequate to completely unravel the sometimes very complex history of sea level fluctuation especially where erosion has prevailed over deposition and or deposits are difficult to date on the basis of our experience we think that much additional information can be gained through geomorphological interpretation of the profiles of those slopes in order to facilitate such interpretation a computer simulation model is developed that is able to predict the morphogenic response to a variety of possible relative sea level histories the results can be used to envisage some new interpretation keys for the analysis of real situations and hopefully as bases for the conception of general models of coastal slope evolution under the action of a variable sea level though preliminary the results so far obtained permit identification of the geomorphological consequences in terms of resulting slope profile of ordered successions of transgressions and regressions of different amplitude rate order and style moreover they provide interesting insights into the role that different styles of tectonic uplift may play in the phenomenon of multiple terracing of coastal slopes

the interplay between crystallization replenishment and hybridization in large felsic magma chambers abstract while hybridized granitoid magmas are readily identifiable the mechanisms of hybridization in large crustal magma chambers are so not clearly understood characteristic features of hybrid granitoids are 1 both the granitoid and included enclaves are commonly hybrids as shown by mineralogy geochemistry and isotopes 2 mixing seen in zoned plutons and synplutonic dykes and enclaves occurred early 3 zoned plagioclase phenocrysts commonly show very complex life histories of growth and dissolution 4 mafic end members in hybrids are commonly fractionated magmas and 5 stratification in subvolcanic granitoid magma chambers is not uncommon and stratification has been identified in some deeper level plutons hybridization must overcome the tendency to form a stable stratification of dense mafic magma underlying less dense felsic magma experimental work with magma analogues and theoretical considerations reveal very severe thermal rheological and dynamical limitations on mixing only very similar composition temperature magmas are likely to mix to homogeneity and only moderately silicic hybrids are likely to be produced however impossibly silicic hybrids do exist synchronous interactive fractional crystallization and hybridization may provide a mechanism for hybridization of magmas in the following manner a mafic magma intrudes into the base of a stratified felsic magma and is cooled against it crystallization of the upper boundary layer of the mafic magma yields an eventually buoyant residual melt that overturns and mixes with an adjacent stratum of the felsic magma chamber subsequently melt released by crystallization pf this now hybrid zone mixes with adjacent more felsic zones thus a suite of hybrid magmas are progressively formed density inhibitions are overcome by the generation of relatively low density residual melts as crystallization proceeds later injections are preserved as dykes and enclaves composed of hybrid magma in this process only physically adjacent and dynamically thermally similar magmas directly interact and so may mix to homogeneity finally not simply felsic and mafic endmembers mix but a whole suite of intermediate endmembers participate ranging from relatively mafic through to felsic pairs of magmas direct mixing between the primary magmas only occurs at the beginning

modes and times of caldera resurgence the 10 ka evolution of ischia caldera italy from high precision archaeomagnetic dating abstract ischia is a well exposed and densely populated late quaternary caldera in the campanian magmatic province of italy ischia caldera experienced an average uplift rate of 3 3 cm year in the last ca 30 ka and is still actively resurging during the last 10 ka coeval with the resurgence a volcanic field of alkali trachytic to trachyandesitic lava domes lava flows tuff and scoria rings and pumice cones developed mainly on the eastern sector of the caldera along both resurgence related faults and regional nnw and ne striking faults in order to improve both our understanding of the recent volcanic history and the evaluation of future risks on ischia island a high precision archaeomagnetic dating method was applied to the products of 12 volcanic centres with probable age 14 c ages archaeomagnetic and other geochronological data as well as stratigraphic constraints show that during the studied time interval ischia volcanism occurred in five periods separated by phases of quiescence and coeval with earthquake and landslide events this fact suggests a pulsating mode of uplifting and deformations of the ischia resurgence during the two oldest periods of activity 7200 6800 bc and 4100 2300 bc resurgence probably produced a dome shaped structure location and geometry of vents suggest the occurrence of magma uprise along the fractures produced by bending of the overburden crustal block most of magma was emplaced as intrusions at the interior of the resurgent block whereas volcanism was represented by very viscous differentiated and crystallized lavas that emplaced as domes and high aspect ratio flows the resurgent dome caused recurrent lateral collapses that removed about 2 5 km 3 of rocks during the three youngest periods of activity 1800 1000 bc 650 bc 355 ad and 1302 ad resurgence affected a fault bounded asymmetric block this resulted from both a hydrostatic rebound of the crustal block after removal of material involved into huge slope instability triggering an increase in uplift rate and b new influxes of less evolved magma batches into the shallow reservoir that in turn favoured the intense volcanism of the last 4000 years

glacial geomorphology and geographic information systems recent developments in the field of glacial geomorphology have dramatically increased the need to acquire maintain manipulate and analyze large amounts of landform landscape and sediment data the use of geographic information systems gis has provided new platforms and tools for analysis and visualization of geomorphic data glacial geomorphologists have used gis to integrate multi source data manage multi scale studies identify previously unrecognized spatial and temporal relationships and patterns in geomorphic data and to link landform data with numerical models as part of model calibration and verification gis based analyses associated with numerical modeling are improving our understanding of glacial landscape evolution and are allowing new quantitative and systematic examinations of spatial and temporal patterns of glacial landforms and processes this has allowed for the development of insights and concepts that would be unlikely to arise using traditional methods alone key recommendations for future research and applications in glacial geomorphology include enhanced gis education and dissemination the development of standards and conventions for glacial geomorphic data community projects to collect data into readily accessible databases and enhanced use of linked gis model frameworks to address major issues in glacial geomorphology