petrologic determination of ascent rates for the 1995 1997 soufriere hills volcano andesitic magma the recent eruption of the soufriere hills volcano in montserrat july 1995 to present october 1997 has produced a hornblende bearing andesitic lava dome it is possible to petrologically estimate changes in ascent rates of amphibole bearing magmas for certain rates of decompression a breakdown rim of fine grained anhydrous reaction products forms where amphibole is in contact with melt the thickness of the rim varies with ascent rate most of the amphibole phenocrysts in the magma storage region lack breakdown rims about 10 have 200 400 m thick coarse grained breakdown rims that are interpreted to be relicts of a past heating event study of a time series of new dome andesites showed that ascent rate increased from december 1995 0 001 m s to july 1996 0 008 m s while eruptive style remained extrusive ascent rate increased to 0 012 m s in august 1996 and the first major explosive eruption occurred on 17 18 september 1996

separation of regional and residual anomalies by least squares orthogonal polynomial and relaxation techniques a performance evaluation1 the performances of least squares orthogonal polynomial and relaxation techniques in the separation of regional and residual anomalies have been evaluated with a view to minimizing personal biasing the advantage of orthogonal over nonorthogonal polynomials is their ability to estimate an optimum order of polynomial to represent the predominant regional trend in the data using an approximate 2d difference table the z matrix the correlation coefficients between residuals of two consecutive orders also give the same result in the relaxation technique a linear trend is assumed within each cell of the mesh of a square grid a set of such linear segments can approximate any complicated regional trend the performances of these two techniques have been evaluated using simulated gravity anomalies produced by 2d and 3d complex regional structures superimposed on residual fields due to cylinders and prismatic bodies as well as three field examples taken from the published literature the analyses have revealed that the relaxation technique produces excellent results when an optimum polynomial order rather than an arbitrary fixed one is used for computing the boundary conditions along the periphery of the map analyses have revealed that such boundary conditions provide minimum distortion near the two ends of the profile

mobility of pyroclastic flows and surges at the soufriere hills volcano montserrat the soufriere hills volcano on montserrat has produced avalanche like pyroclastic flows formed by collapse of the unstable lava dome or explosive activity pyroclastic flows associated with dome collapse generate overlying dilute surges which detach from and travel beyond their parent flows the largest surges partially transform by rapid sedimentation into dense secondary pyroclastic flows that pose significant hazards to distal areas different kinds of pyroclastic density currents display contrasting mobilities indicated by ratios of total height of fall h run out distance l area inundated a and volume transported v dome collapse flow mobilities characterised by either l h or a v2 3 resemble those of terrestrial and extraterrestrial cold rockfalls dade and huppert 1998 in contrast fountain fed pumice flows and fine grained secondary pyroclastic flows travel slower but for comparable initial volumes and heights can inundate greater areas

growth of the lava dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008 the third episode of lava dome growth at soufriere hills volcano began 1 august 2005 and ended 20 april 2007 volumes of the dome and talus produced were measured using a photo based method with a calibrated camera for increased accuracy the total dense rock equivalent dre volume of extruded andesite magma 306 51 mm3 was similar within error to that produced in the earlier episodes but the average extrusion rate was 5 6 0 9 m3s 1 dre higher than the previous episodes extrusion rates varied in a pulsatory manner from 0 5 m3s 1 to 20 m3s 1 on 18 may 2006 the lava dome had reached a volume of 85 mm3 dre and it was removed in its entirety during a massive dome collapse on 20 may 2006 extrusion began again almost immediately and built a dome of 170 mm3 dre with a summit height 1047 m above sea level by 4 april 2007 there were few moderate sized dome collapses 1 10 mm3 during this extrusive episode in contrast to the first episode of dome growth in 1995 8 when they were numerous the first and third episodes of dome growth showed a similar pattern of low 0 5 m3s 1 but increasing magma flux during the early stages with steady high flux after extrusion of 25 mm3

avtis a novel millimetre wave ground based instrument for volcano remote sensing during may and june 2004 we tested a novel millimetre wave ground based dual mode radar and radiometer on soufriere hills volcano montserrat avtis all weather volcano topography imaging sensor has an active radar mode designed to image the distance to lava domes on volcanoes whose summits are commonly obscured by persistent cloud such as soufriere hills volcano the passive radiometer mode can be employed to measure the surface temperature of the imaged topography in its current form avtis can be deployed by two people and takes 50 min to acquire a 20 5 scene at 0 1 increments during the fieldwork period the lava dome was not growing and only the radar mode was used the data recorded indicate that the maximum distance imaged was about 3800 m combining datasets acquired from different viewpoints can potentially provide a full 3d topographic model the accuracy and completeness of this reconstruction are reduced by two factors firstly relatively small grazing angles of the ground based line of sight rendered incised valleys invisible secondly methods currently used to orient the instrument limit the accuracy of the resulting topographic information nevertheless valuable information on new topographic surfaces was obtained in an area north of the lava dome where a valley has been infilled by deposits and in the amphitheatre created by the giant collapse event of july 2003

magma production and growth of the lava dome of the soufriere hills volcano montserrat west indies november 1995 to december 1997 from november 1995 to december 1997 a total volume of 246 106 dre m of andesite magma erupted partitioned into 93 106 m of the dome 125 106 m of pyroclastic flow deposits and 28 106 m of explosive ejecta in the first 11 weeks magma discharge rate was low 0 5 m s from february 1996 to may 1997 discharge rates have averaged 2 1 m s but have fluctuated significantly and have increased with time three pulses lasting a few months can be recognised with discharge rates reaching 3 to 8 m s short term pulsations in growth lasting a few days reach discharge rates of over 10 m s and there are periods of days to a few weeks when dome growth is 0 5 m s discharge rate increased from may 1997 with an average rate of 7 5 m s to december 1997 the observations indicate an open magmatic system

chlorine variations in the magma of soufriere hills volcano montserrat insights from cl in hornblende and melt inclusions the soufriere hills volcano in montserrat erupts a cl rich porphyritic andesite hcl degassing accompanies eruption and is dependent on the growth rate of the lava dome the magma contains hornblende phenocrysts that show repetitive zoning in most elements including cl on the basis of the zoning data cl oh ratios in the melt calculated from partitioning data increase rimward through each zone indicating that the phenocrysts formed under conditions of varying cl oh m an empirical relationship between a site occupancy in the hornblende and temperature implies that crystallisation of each zone is also accompanied by increasing temperature each zone ends at a resorption horizon and crystallisation recommences at lower temperature and cl oh m melt inclusion h2o and cl contents for the 8th january 2007 explosive eruption can be explained by closed system degassing with dclfl m between 5 and 30 or by open system degassing accompanied by a small amount of crystallisation however neither simple closed system degassing nor convective circulation of magma can explain the positive correlation of cl oh m with temperature we suggest that the zoning can be caused by accumulation of co2 rich vapour in the andesite probably as a result of mafic magma injection into the chamber decreasing h2o fugacity and or increasing clm result in increasing cl oh m while heat transferred with the volatiles causes the rise in temperature intermittently the accumulated fluid is lost to the surface possibly as a result of renewed eruptive activity this model requires the co2 rich fluid to be decoupled from the magma consistent with previous observations of continuous co2 emissions at the surface

measuring large topographic change with insar lava thicknesses extrusion rate and subsidence rate at santiaguito volcano guatemala lava flows can produce changes in topography of the order of 10s 100s of metres a knowledge of the resulting volume change provides evidence about the dynamics of an eruption using differential insar phase delays it is possible to estimate height differences between the current topography and a digital elevation model dem this does not require a pre event sar image so it does not rely on interferometric phase remaining coherent during eruption and emplacement synthetic tests predict that we can estimate lava thicknesses of as little as 9 m given a minimum of five interferograms with suitably large orbital baseline separations in the case of continuous motion such as lava flow subsidence we invert interferometric phase simultaneously for topographic change and displacement we apply this to santiaguito volcano guatemala and measure increases in lava thickness of up to 140 m between 2000 and 2009 largely associated with activity between 2000 and 2005 we find a mean extrusion rate of 0 437 0 06 m

a low cost method applicable worldwide for remotely mapping lava dome growth abstract lava dome growth and collapse represents both a significant hazard as it can trigger pyroclastic density currents and a monitoring challenge limiting monitoring to a few known active volcanoes here i propose a new differencing technique based on synthetic aperture radar sar amplitude images to quantify the extent of lava dome growth this differencing technique which is both low cost and can be utilized worldwide is applied to sar amplitude images at mount st helens and validated using 2004 2008 aerial photography observations difference of amplitude images accurately characterize the dome growth location the low ground resolution of the 2004 2008 sar data leads to underestimation by 10 to 15 of the dome extent but the accuracy of this method will increase with the improved resolution of current and future sar missions amplitude images are a low level sar product available from all sar satellites mostly freely making the proposed method ideal for systematic low cost monitoring of lava dome growth worldwide with minimum processing required

lava production at soufriere hills volcano montserrat 1995 2009 1 we estimate that about 1 km3 of andesitic lava has been produced at soufriere hills volcano montserrat from 1995 to 2009 there were three major episodes of extrusion each lasting about 2 to 3 5 years and producing about 280 to 340 m m3 of lava and one minor episode our estimates account for the dense rock equivalent volumetric contributions from the core and talus components of the lava dome pyroclastic flow deposits and air fall deposits by 2005 at least two thirds of the erupted mass has already entered the sea the average lava flux across the major extrusion episodes has been 3 5 m3s 1 with short period 10 15 days pulses up to 10 20 m3s 1 the first and third episodes of extrusion show similar flux histories suggesting similar behaviour of the system ten years apart waning flux towards the end of each episode may be caused by declining overpressure in the magma reservoir

clastic and core lava components of a silicic lava dome the formation of a lava dome involves fractionation of the lava into core and clastic components we show that for three separate successive andesitic lava domes that grew at soufriere hills volcano montserrat between 1999 and 2007 the volumetric proportion of the lava converted to talus or pyroclastic flow deposits was 50 90 of the lava extruded currently only 8 of the total magma extruded during the 1995 2007 eruption remains as core lava the equivalent representation in the geological record will probably be even lower most of the lava extruded at the surface flowed no further than 150 300 m from the vent before disaggregation resulting in a lava core whose shape tends to a cylinder moderate to high extrusion rates at the soufriere hills domes may have contributed to the large clastic fraction observed creating talus dissipates much of the energy that would otherwise be stored in the core lava of domes the extreme hazards from large pyroclastic flows and blasts posed by wholesale collapse of a lava dome depend largely on the size of the lava core and hence on the aggregate history of the partitioning process not on the size of the dome

remote sensing of glacier and ice sheet grounding lines a review abstract the precise positioning and long term monitoring of the grounding line forming the boundary between grounded and floating ice of marine ice sheets and tidewater glaciers is critical for assessing ice sheet glacier stability ice sheet glacier mass balance calculations and numerical ice modelling however mapping of the grounding line is a challenging task since it is a subglacial and transient feature remote sensing techniques do not map the grounding line directly but locate surface features in the grounding zone that serve as proxies for the true grounding line position the large variety of methods products and publications as well as an inconsistent use of terminology additionally complicate the topic we present the first detailed review of existing remote sensing techniques and data for grounding line mapping benefits and limitations of the different techniques and data sources are discussed and illustrated with examples we identify a present tradeoff between accuracy and both spatial coverage and temporal resolution of the derived grounding line products rather new methods like sentinel 1 sar synthetic aperture radar differential range offset tracking drot and pseudo crossover radar altimetry pcra offer the potential for recent measurements and to fill gaps in some areas nevertheless there is a high demand of new spaceborne radar sensors that provide time series of very short repeat pass data to enable regular grounding line monitoring with most accurate differential sar interferometry dinsar on a continental scale

the explosive eruption of soufriere hills volcano montserrat west indies 17 september 1996 on 17 september 1996 the soufriere hills volcano started a 9 hour period of dome collapse involving 11 7 106 m dre of lava after 2 5 hours of quiescence a sustained explosive eruption began estimated eruption parameters are plume height at least 11 3 km and a maximum of 15 km 180 m s for launch velocities of ballistic clasts peak explosion pressure of 27 5 mpa magma water contents of 2 5 5 magma discharge rates from 2300 to 4300 m s ejecta volume of 3 2 0 9 106 m dre ejecta consists of pumice 1160 kg m higher density vesiculated ejecta 1300 to 2000 kg m dense glassy clasts 2600 kg m breccias cut by tuffisite veins and hydrothermally altered lithics the ejecta are interpreted as a conduit assemblage with evacuation of the conduit down to depths of about 3 to 5 km the eruption was triggered by unloading of a gas pressurised conduit due to dome collapse

catastrophic lava dome failure at soufriere hills volcano montserrat 12 13 july 2003 the lava dome collapse of 12 13 july 2003 was the largest of the soufriere hills volcano eruption thus far 1995 2005 and the largest recorded in historical times from any volcano 210 million m3 of dome material collapsed over 18 h and formed large pyroclastic flows which reached the sea the evolution of the collapse can be interpreted with reference to the complex structure of the lava dome which comprised discrete spines and shear lobes and an apron of talus progressive slumping of talus for 10 h at the beginning of the collapse generated low volume pyroclastic flows it undermined the massive part of the lava dome and eventually prompted catastrophic failure from 02 00 to 04 40 13 july 2003 large pyroclastic flows were generated these reached their largest magnitude at 03 35 when the volume flux of material lost from the lava dome probably approached 16 million m3 over two minutes the high flux of pyroclastic flows into the sea caused a tsunami and a hydrovolcanic explosion with an associated pyroclastic surge which flowed inland a vulcanian explosion occurred during or immediately after the largest pyroclastic flows at 03 35 13 july and four further explosions occurred at progressively longer intervals during 13 15 july 2003 the dome collapse lasted approximately 18 h but 170 of the total 210 million m3 was removed in only 2 6 h during the most intense stage of the collapse

using microlites to gain insights into ascent conditions of differing styles of volcanism at soufriere hills volcano abstract microlite textural characteristics are analyzed in the products of vulcanian explosions ash venting occurring synchronously with lava effusion syn extrusive ash venting a precursory explosion and lava dome effusion associated with phases 3 and 5 of the current soufriere hills volcano shv eruption 2d microlite population statistics and crystal size distributions are used to infer decompression pathways for each style of volcanism in addition magma ascent rates for each eruptive style were calculated using microlite number density toramaru et al 2008 strong differences between pyroclastic and effusive microlites are observed in 2d population statistics and crystal size distributions indicating higher amounts of smaller microlites 0 0084 to 0 012 mm however syn extrusive ash venting samples have comparatively greater amounts of large microlites the similarity between lava dome and vulcanian explosions at larger microlite sizes suggests comparable crystallization conditions in the deeper conduit system 2 km depth the contrast in eruption style despite similarity at depth suggests a shallow control to eruption processes at shv the greater amounts of large microlites in syn extrusive ash venting compared to the lava dome indicates two distinct decompression pathways within a single conduit inferred to result from differences in ascent rate sluggish conduit margin ascent leading to lower decompression rates is inferred to produce the increased degree of crystal growth observed in syn extrusive ash venting compared with the lava dome calculated magma ascent rates for vulcanian explosions and syn extrusive ash venting have similar ranges while lava effusion is up to a factor of 10 faster differences in magma ascent rate are inferred to result from variations in the depth at which ascent rate is calculated for each eruptive style ascent rate is calculated at microlite nucleation depth using the method of toramaru et al 2008 however the average microlite nucleation depth will vary because of differences in microlite nucleation rate during ascent more small microlites in the lava dome suggest greater nucleation rates in the shallow conduit recording an on average shallower magma ascent rate 2 km depth

thermal photogrammetric imaging a new technique for monitoring dome eruptions abstract structure from motion sfm algorithms greatly facilitate the generation of 3 d topographic models from photographs and can form a valuable component of hazard monitoring at active volcanic domes however model generation from visible imagery can be prevented due to poor lighting conditions or surface obscuration by degassing here we show that thermal images can be used in a sfm workflow to mitigate these issues and provide more continuous time series data than visible light equivalents we demonstrate our methodology by producing georeferenced photogrammetric models from 30 near monthly overflights of the lava dome that formed at volcan de colima mexico between 2013 and 2015 comparison of thermal models with equivalents generated from visible light photographs from a consumer digital single lens reflex dslr camera suggests that despite being less detailed than their dslr counterparts the thermal models are more than adequate reconstructions of dome geometry giving volume estimates within 10 of those derived using the dslr significantly we were able to construct thermal models in situations where degassing and poor lighting prevented the construction of models from dslr imagery providing substantially better data continuity than would have otherwise been possible we conclude that thermal photogrammetry provides a useful new tool for monitoring effusive volcanic activity and assessing associated volcanic risks

overview of the eruption of soufriere hills volcano montserrat 18 july 1995 to december 1997 the onset of phreatic volcanic activity at the soufriere hills volcano montserrat on 18 july 1995 followed a three year period of heightened volcano seismic activity beneath the island phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 november 1995 magma production rate has varied leading to changes in eruptive style an explosive eruption on 17 september 1996 followed a period of enhanced dome growth and large scale gravitational collapses from its eastern flank increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest north and west during early 1997 sustained high magma production rate since june 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions dome growth re started immediately after the cessation of the latest of these explosive phases in october 1997 and continues as of december 1997

thirty years of satellite derived lava discharge rates at etna implications for steady volumetric output 1 we present a 30 year long data set of satellite derived time averaged lava discharge rates tadr for mount etna volcano sicily italy spanning 1980 2010 and comprising 1792 measurements during 23 eruptions we use this to classify eruptions on the basis of magnitude and intensity as well as the shape of the tadr time series which characterizes each effusive event we find that while 1983 1993 was characterized by less frequent but longer duration effusive eruptions at lower tadrs 2000 2010 was characterized by more frequent eruptions of shorter duration and higher tadrs however roughly the same lava volume was erupted during both of these 11 year long periods so that the volumetric output was linear over the entire 30 year period increasing at a rate of 0 8 m3 s 1 between 1980 and 2010 the cumulative volume record can be extended back in time using data available in the literature this allows us to assess etna s output history over 5 centuries and to place the current trend in historical context we find that output has been stable at this rate since 1971 at this time the output rate changed from a low discharge rate phase which had characterized the period 1759 to 1970 to a high discharge rate phase this new phase had the same output rate as the high discharge rate phase that characterized the period 1610 1669 the 1610 1669 phase ended with the most voluminous eruption of historic times

lava dome growth and mass wasting measured by a time series of ground based radar and seismicity observations range and intensity measurements of the change in summit lava 1 5 10 6 m 3 22 2 avtis range measurements to measure the talus growth 3 9 10 6 m 3 57 and 3 rockfall seismicity to measure the pyroclastic flow deposit volumes 1 4 10 6 m 3 21 which gives an overall dense rock equivalent extrusion rate of about 7 m 3 s 1 these figures demonstrate how efficient nonexplosive lava dome growth can be in generating large volumes of primary clastic deposits a process that by reducing the proportion of erupted lava stored in the summit region will reduce the likelihood of large hazardous pyroclastic flows

the magmatic plumbing system beneath santiaguito volcano guatemala abstract the silicic dome complex of santiaguito guatemala has exhibited continuous extrusive activity for 90 years despite its longevity remarkably little is known about the magmatic plumbing system beneath santiaguito here we use petrological analyses of lava samples to define this plumbing system from storage in the lower to mid crust through to extrusion onto the surface magmatic storage conditions are constrained using amphibole and plagioclase phenocrysts ascent processes are examined using the breakdown rims of amphibole phenocrysts and the texture and composition of groundmass while shallow processes are revealed by the alteration of titanomagnetites and matrix glass santiaguito magmas contain amphiboles that formed from 24 km to 12 km beneath the surface with temperatures of 940 to 980 c and f o2 of nno 0 4 to nno 1 2 amphibole breakdown rims suggest that during the final phases of ascent magma may rise from 12 km the limit of amphibole stability relatively rapidly 27 to 84 m h 1 we infer from the texture of the groundmass that melt rigidifies prior to extrusion a finding that may have important consequences for conduit dynamics

changes in progradation rate of the tidal flats at the mouth of the changjiang yangtze river china progradation rates of tidal flats at the chiangjiang river mouth china over different periods were examined based on surveys and historical records rapid progradation after the holocene sea level rise began about 2000 years ago because of an increase in riverine sediment the tidal flats at the river mouth have grown at a rate of about 5 km2 year and the southern mainland shoreline in front of the river mouth has advanced at a rate of 17 m year in recent decades the lateral progradation rate at the frontal area has been from tens to hundreds of meters per year the evolutionary process of the tidal flat is highly episodic under this general tendency of progradation spring neap cyclicity shows clearly in calm seasons while the bare flat surface is sensitive to windy conditions different seasonal patterns occur between the marsh and the bare flat because of the influence of vegetation spatial changes in sedimentation rate are also striking which could be attributed to differences in sediment distribution and hydrodynamics the changeability of sediment surface shows a shoreward reduction from the subtidal area to the high marsh likely due to the shoreward decrease in water energy and submergence time as well as the protective effect of marsh vegetation it is predicted that the general progradation could be greatly slowed when the sharp reduction in riverine sediment caused by the three gorges project and the south to north water diversion will coincide with the rapid relative sea level rise

volcanic seismicity at montserrat a comparison between the 2005 dome growth episode and earlier dome growth in 2005 soufriere hills volcano on montserrat started its third major episode of dome growth since the current eruption started in 1995 the style of seismicity associated with dome growth has changed in particular the events known as hybrid earthquakes have reduced in numbers by an order of magnitude compared to previous dome growth episodes in the past hybrid earthquakes have been associated with magma ascent and so it is surprising to observe prolonged periods of rapid dome growth during which very few hybrid earthquakes are recorded in addition the frequency of the codas of hybrid earthquakes as well as of some of the so called long period events has changed the changes in recorded seismicity have had a marked effect on the techniques used to monitor the state of the volcano and those events that continue to be recorded in large numbers rockfall events have been used to assess the state of activity at the volcano

control of magma flow in dykes on cyclic lava dome extrusion 1 lava dome eruptions are commonly characterized by large fluctuations in discharge rate with cyclic behaviour on time scalesranging from hours to decades examples include bezymianny volcano russia merapi java santiaguito guatemala mt st helens usa mt unzen japan and soufriere hills volcano montserrat previous models have assumed simple cylindrical conduits for magma transport but extrusions are mainly fed by dykes with cylindrical geometries developing only at shallow levels the widths of dykes embedded in an elastic medium are influenced by local magma pressure affecting flow rates and system dynamics strongly we develop a model for magma flow in dykes which predicts intense pulsations of magma extrusion for the case of a constant source pressure the period time scale is determined by the elastic deformation of the dyke walls and the length to width ratio of the dyke the dyke acts like a volumetric capacitor storing magma as pressure increases and then releasing magma in a pulse of extrusion for the soufriere hills volcano cyclic extrusions with time scales of a few weeks are predicted for dykes 300 500 m long and 3 6 m wide matching observations the model explains the sharp onset of tilt pulsations and seismic swarms citation costa a o melnik r s j sparks and b voight 2007 control of magma flow in dykes on cyclic lava dome extrusion geophys res lett 34 l02303 doi 10 1029 2006gl027466

hot pressing in conduit faults during lava dome extrusion insights from mount st helens 2004 2008 abstract rhyodacitic volcanoes such as mount st helens msh soufriere hills mount unzen and mount pelee erupt spines mantled by layers of magma derived cataclasite and fault gouge msh produced seven lava spines from 2004 2008 composed of low porosity compositionally uniform crystalline dacite dome extrusion was attended by continuous drumbeat seismicity derived from faulting along the conduit margin at 0 5 1 km depth and evidenced by the enveloping gouge layers we describe the properties of the gouge derived fault rocks including laboratory measurements of porosity and permeability the gouge varies from unconsolidated powder to lithified low porosity low permeability fault rocks we reconstruct the subsurface ascent of the msh magma using published field observations and create a model that reconciles the diverse properties of the gouge with conditions in the conduit during ascent i e velocity temperature we show lithification of the gouge to be driven by hot pressing processes wherein the combination of elevated temperature confining pressure and dwell time cause densification and solid state sintering of the comminuted crystal rich glass poor gouge the degree of gouge lithification corresponds with residence time in the conduit such that well lithified materials reflect extended times in the subsurface due to slower ascent rates with this insight we suggest that gouge competence can be used as a first order estimate of lava ascent rates furthermore we posit gouge lithification which reduces porosity and permeability inhibits volcanic outgassing thereby increasing the potential for explosive events at spine producing volcanoes

application of actualistic models to unravel primary volcanic control on sedimentation taveyanne sandstones oligocene northalpine foreland basin abstract this work is focused on the taveyanne sandstones gres de taveyanne an oligocene volcaniclastic turbidite sequence cropping out in the northern alpine molassa between se france and central switzerland with the aim to investigate the temporal relationship between volcanic activity and sediment supply detailed stratigraphic sedimentological and petrographic xrd analyses on mudstones and point counts on sandstones studies conducted on three sections col de l oulette and flaine in se france taveyanne in sw switzerland allow a discrimination of three main facies among which only one is extremely enriched in volcaniclastic detritus and characterized by features similar to those of disaggregated pyroclastic density current deposits the other two facies are characterized by variable to no volcanic detritus but supplied by crystalline and sedimentary detritus such sediment trends are similar to those of modern volcanically controlled source to sink systems this allows a reinterpretation of the taveyanne sandstones as a syn volcanic turbidite system episodically supplied by large amounts of volcanic detritus which periodically modified the drainage paths moreover the well known temporal and spatial persistence of such modifications in modern settings leads to conciliate the syn volcanic supply with the location of the volcanic centers in the internal part of the alps without invoking particular climatic and tectonic conditions controlling foreland sedimentation