sector collapse sedimentation and clast population evolution at an active island arc volcano stromboli italy sciara del fuoco is the subaerial part of a partially filled sector collapse scar that extends to 700 m below sea level on stromboli volcano the collapse occurred 2200 m and 10 km from the shore to the nnw a fan shaped mounded feature comprises debris avalanche deposits 4 km3 from two or more sector collapses volcaniclastic density currents originating from sciara del fuoco follow the topographic margin of the debris avalanche deposits although overbank currents and other unconfined currents widely cover the mounded feature with turbidites historical recorded eruptive activity in sciara del fuoco is considerably less than that which occurred earlier and much of the partial fill may have formed from eruptions soon after the sector collapse it is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the tyrhennian basin evidence that the early post collapse eruptive discharge was greater than the apparent recent flux 2kg s counters suggestions that a substantial part of stromboli s growth has been endogenous the partial fill of sciaria del fuoco is dominated by lava and spatter layers rather than by the scoria and ash layers classically regarded as main constituents of strombolian cinder cones much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra which is therefore rapidly transported to the sea delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport mainly in avalanches and by shoreline wave reworking and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast forming processes considerable amounts of dense non vesicular fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate the submarine extension of the collapse scar and the continuing topographic depression to 2200 m below sea level are zones of considerable by passing of fine sand and silt which are transported in turbidity currents evidently volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast forming processes that occurred during an eruption marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration unless there is a high rate of discharge of pyroclastic material into the sea

tsunamis in the aeolian islands southern italy a review the aeolian islands located in the south tyrrhenian sea to the west of calabria and to the north of sicily constitute the aeolian volcanic arc characterized by a relevant volcanic activity with an established tsunamigenic potential according to the documentary sources that are available for the aeolian tsunamis and that cover unfortunately only about the last 100 years stromboli is responsible for the majority of the events some cases are also known to have occurred at the islands of salina and vulcano in terms of intensities the most destructive events are those originated by the stromboli volcano reported to have produced severe destruction to boats and houses and to have even caused injuries and fatalities in this work we focus on the historical events and discard the paleotsunami occurrences that were probably associated with the ascertained flank collapses of the volcanic cones we also neglect the recent destructive tsunamis of 30 december 2002 which were caused by a series of mass failures at the sciara del fuoco since observations and analyses are of such an amount that deserve to be illustrated in devoted papers the bulk of the present research consisted in collecting all the available data on the historical cases the first in order of time is the july 1916 stromboli tsunami with the purpose of casting more light on their generation mechanism and on their effects and consequently of contributing to the studies on assessment of tsunami hazard and risk in the aeolian islands and in the southern tyrrhenian sea

continuous gps and broad scale deformation across the rhine graben and the alps in order to study the ongoing tectonic deformation in the rhine graben area we reconstruct the local crustal velocity and the strain rate field from gps array solutions following the aim of this work we compile the velocities of permanent gps stations belonging to various networks euref agnes regal and rgp in central western europe moreover the strain rate field is displayed in terms of principal axes and values while the normal and the shear components of the strain tensor are calculated perpendicular and parallel to the strike of major faults the results are compared with the fault plane solutions of earthquakes which have occurred in this area a broad scale kinematic deformation model across the rhine graben is provided on the basis of tectonics and velocity results of the gps permanent stations the area of study is divided into four rigid blocks between which there might be relative motions the velocity and the strain rate fields are reconstructed along their borders by estimating a uniform rotation for each block the tectonic behaviour is well represented by the four block model in the rhine graben area while a more detailed model will be needed for a better reconstruction of the strain field in the alpine region

seismic wave attenuation from borehole and surface records in the top 2 5km beneath the city of basel switzerland summary we investigate attenuation q 1 of sediments of 2 5 3 5 km thickness underneath the city of basel switzerland we use recordings of 195 induced events that were obtained during and after the stimulation of a reservoir for a deep heat mining project in 2006 and 2007 the data set is ideally suited to estimate q as all events are confined to a small source volume and were recorded by a dense surface network as well as six borehole sensors at various depths the deepest borehole sensor is positioned at a depth of 2 7 km inside the crystalline basement at a mean hypocentral distance of 1 8 km this allows us to measure q for frequencies between 10 and 130 hz we apply two different methods to estimate q first we use a standard spectral ratio technique to obtain q and as a second measure we estimate q in the time domain by convolving signals recorded by the deepest sensor with a q operator and then comparing the convolved signals to recordings at the shallower stations both methods deliver comparable values for q we also observe similar attenuation for p and s waves qp qs as expected q increases with depth but with values around 30 50 it is low even for the consolidated permian and mesozoic sediments between 500 and 2700 m

submarine pyroclastic deposits formed at the soufriere hills volcano montserrat 1995 2003 what happens when pyroclastic flows enter the ocean the soufriere hills volcano montserrat west indies has undergone a series of dome growth and collapse events since the eruption began in 1995 over 90 of the pyroclastic material produced has been deposited into the ocean sampling of these submarine deposits reveals that the pyroclastic flows mix rapidly and violently with the water as they enter the sea the coarse components pebbles to boulders are deposited proximally from dense basal slurries to form steep sided near linear ridges that intercalate to form a submarine fan the finer ash grade components are mixed into the overlying water column to form turbidity currents that flow over distances 30 km from the source the total volume of pyroclastic material off the east coast of montserrat exceeds 280 106 m3 with 65 deposited in proximal lobes and 35 deposited as distal turbidites

morpho structural setting of stromboli volcano revealed by high resolution bathymetry and backscatter data of its submarine portions the first high resolution bathymetric and backscatter maps of offshore stromboli island are presented together with an interpretation of its volcanic structural and sedimentary features the volcanic edifice is characterized by a sub conical shape with a quasi bilateral symmetry with respect to a ne sw axis the dimensions of the strombolicchio volcanic centre to the ne of stromboli have been restored by redrawing its morphology before wave action that eroded it in late quaternary time on the ne submarine flank of strombolicchio a n64 e structural trend controls the shape of strombolicchio canyon on the southern side of stromboli the submarine flank has a radial structural trend possibly reflecting a volcanic stress regime landslide scars at various scales are ubiquitous on the submarine slopes of stromboli repeated large scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano producing large debris avalanche deposits

onset of submarine debris flow deposition far from original giant landslide submarine landslides can generate sediment laden flows whose scale is impressive individual flow deposits have been mapped that extend for 1 500 km offshore from northwest africa these are the longest run out sediment density flow deposits yet documented on earth this contribution analyses one of these deposits which contains ten times the mass of sediment transported annually by all of the world s rivers understanding how this type of submarine flow evolves is a significant problem because they are extremely difficult to monitor directly previous work has shown how progressive disintegration of landslide blocks can generate debris flow the deposit of which extends downslope from the original landslide we provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide encased within deposits of a more dilute flow type called turbidity current very little sediment was deposited across the intervening large expanse of sea floor where the flow was locally very erosive sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea floor gradient from 0 05 degrees to 0 01 degrees this debris flow was probably generated by flow transformation from the decelerating turbidity current the alternative is that non channelized debris flow left almost no trace of its passage across one hundred kilometres of flat 0 2 degrees to 0 05 degrees sea floor our work shows that initially well mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean

depositional features and transportation mechanism of valley filling iwasegawa and kaida debris avalanches japan the depositional features of two valley filling debris avalanche deposits were studied to reveal their transportation and depositional mechanisms the valley filling iwasegawa debris avalanche deposit ca 0 1 km3 is distributed along the valleys at the southeastern foot of tashirodake volcano northern honshu japan debris avalanche blocks range in size from 0 3 km3 is distributed along the valleys at the eastern southeastern foot of ontake volcano central japan debris avalanche blocks range in size from 25 m proximally to 7 m in the medial zone debris avalanche matrix percentages increase from 50 70 in the proximal zone to 80 in the distal zone the debris avalanche matrix is more abundant 80 90 at the bottom part of the deposit deformation structures observed in the debris avalanche blocks include elongation folding conjugate reverse faults and numerous minor faults in unconsolidated materials lithic components within the debris avalanche matrix tend to have a higher percentage of plucked clasts from the adjacent underlying formations a bingham plug flow model is consistent with the transportation and depositional mechanisms of the valley filling debris avalanches in the plug of the debris avalanche fragile blocks were transported without major rupturing due to relatively small shear stresses in regions of small strain rate the debris avalanche matrix was mainly produced by shearing at the bottom and margins of the avalanche valley filling debris avalanches tend to have smaller debris avalanche blocks and larger amounts of debris avalanche matrix than do unconfined debris avalanches these differences may be due to disaggregation of debris avalanche blocks by shearing against valley walls and interaction between debris avalanche blocks and valley walls oriented wood logs and branches reverse grading of clasts at the base and a higher proportion of incorporated clasts at the base are interpreted to result from shearing along the bottom and valley walls

petrology of phlogopite sapphirine bearing al mg granulites from ihouhaouene in ouzzal hoggar algeria an example of phlogopite stability at high temperature al mg granulites with cordierite garnet sapphirine orthopyroxene sillimanite spinel phlogopite k feldspar plagioclase and variable quartz from ihouhaouene in ouzzal algeria display a range of decompression textures involving the breakdown of orthopyroxene and sillimanite and of garnet the succession of parageneses suggests that the p t t evolution corresponds to decompression with cooling from peak conditions of about 950 c and 10 kbar this decompression path is obtained from the paragenetic analysis in the fmas system however according to current kfmash grids this p t t evolution should take place outside the stability field of phlogopite quartz yet this assemblage is probably stable during most of the p t evolution notably during peak metamorphism this discrepancy is interpreted as the effect of the high content of f in phlogopite which should shift its stability limit towards higher temperature the consequences of this shift on the phase relationships in the kfemash system are investigated and it is concluded that a topological inversion could exist in the f bearing system

a magmatic hydrothermal lacustrine exhalite from the permian lucaogou formation santanghu basin nw china the volcanogenic origin of fine grained clastic sedimentary rocks abstract shales in the middle permian lucaogou formation in the intracontinental santanghu rift basin have been considered as typical organic rich profundal shales for decades our study of well cores using petrographic microscope and scanning electron microscopy suggests an otherwise complex hydrovolcanic and hydrothermal origin this paper describes characteristics of a particular type of the shales composed of fine grained detrital minerals and lithic grains some of them are orthopyroxene calcite peralkaline feldspars and analcime that are interpreted as derived from peralkaline alkaline carbonatite pyroxenite analcime phonolite and andesite whereas others are quartz dolomite ankerite serpentine and calcite that were precipitated from syndepositional or penecontemporary hydrothermal fluids grain size ranges from 0 001 to 2 mm mostly 0 01 0 1 mm well developed laminae are mostly 0 5 3 mm thick and alternate with tuffaceous dolomicrite the rocks are interpreted as sublacustrine hydrovolcanic deposits which had been altered by syndepositional hydrothermal fluids the interpretation is substantiated by abundant cone shaped stratigraphic buildups on seismic sections in the basin this study shows an ancient example of volcanic hydrothermal deposits in a rift basin

characterisation of the recent big 95 debris flow deposit on the ebro margin western mediterranean sea after a variety of seismic reflection data swath bathymetry and backscatter data side scan sonographs high resolution hr and very high resolution vhr reflection seismic profiles and sediment cores reveal the complexity of the seafloor and subseafloor features resulting from a large debris flow event that affected the ebro continental slope and base of slope at the beginning of the holocene the big 95 debris flow as it has been named disturbed more than 2200 km2 including a 26 km3 deposit of remobilised sediment covering 2000 km2 swath bathymetry and backscatter imagery allow to distinguish four main areas within the debris flow the source area the proximal depositional area the intermediate blocky depositional area and the distal depositional area in the source area a sinuous headwall scar 20 km long and up to 200 m high and several other secondary scars have been identified sediment released from the source area flowed southeastwards to the proximal depositional area which is the main depocentre of the big 95 debris flow deposit with accumulations over 90 m thick large slabs of sediment detached from this area and from the headwall scar and moved southeastwards embedded in a more mobile matrix thus forming the intermediate blocky depositional area only the looser matrix reached the distal depositional area finally freezing in and partially burying the valencia channel a mid ocean type channel digitisation of vhr seismic reflection profiles where the debris flow deposit is shown as a body of mainly transparent seismic facies has allowed the construction of isobath and isopach maps showing the thickness distribution of the deposit and its interplay with preexisting canyons and channels dating of two sediment cores gives a minimum age of 11 000 calendar years bp for the big 95 debris flow a set of triggering mechanisms including seismicity and oversteepening of the slope due to the existence of a volcanic structure underneath the main headwall is invoked

slope failures on the flanks of the western canary islands abstract landslides have been a key process in the evolution of the western canary islands the younger and more volcanically active canary islands el hierro la palma and tenerife show the clearest evidence of recent landslide activity the evidence includes landslide scars on the island flanks debris deposits on the lower island slopes and volcaniclastic turbidites on the floor of the adjacent ocean basins at least 14 large landslides have occurred on the flanks of the el hierro la palma and tenerife the majority of these in the last 1 million years with the youngest on the northwest flank of el hierro as recent as 15 thousand years in age older landslides undoubtedly occurred but are difficult to quantify because the evidence is buried beneath younger volcanic rocks and sediments landslides on the canary island flanks can be categorised as debris avalanches slumps or debris flows debris avalanches are long runout catastrophic failures which typically affect only the superficial part of the island volcanic sequence up to a maximum thickness of 1 to 2 km they are the commonest type of landslide mapped in contrast slumps move short distances and are deep rooted landslides which may affect the entire thickness of the volcanic edifice debris flows are defined as landslides which primarily affect the sedimentary cover of the submarine island flanks some landslides are complex events involving more than one of the above end member processes individual debris avalanches have volumes in the range of 50 500 km3 cover several thousand km2 of seafloor and have runout distances of up to 130 km from source overall debris avalanche deposits account for about 10 of the total volcanic edifices of the small relatively young islands of el hierro and la palma some parameters such as deposit volumes and landslide ages are difficult to quantify the key characteristics of debris avalanches include a relatively narrow headwall and chute above 3000 m water depth on the island flanks broadening into a depositional lobe below 3000 m debris avalanche deposits have a typically blocky morphology with individual blocks up to a kilometre or more in diameter however considerable variation exists between different avalanche deposits at one extreme the el golfo debris avalanche on el hierro has few large blocks scattered randomly across the avalanche surface at the other icod on the north flank of tenerife has much more numerous but smaller blocks over most of its surface with a few very large blocks confined to the margins of the deposit icod also exhibits flow structures longitudinal shears and pressure ridges that are absent in el golfo the primary controls on the block structure and distribution are inferred to be related to the nature of the landslide material and to flow processes observations in experimental debris flows show that the differences between the el golfo and icod landslide deposits are probably controlled by the greater proportion of fine grained material in the icod landslide this in turn relates to the nature of the failed volcanic rocks which are almost entirely basalt on el hierro but include a much greater proportion of pyroclastic deposits on tenerife landslide occurrence appears to be primarily controlled by the locations of volcanic rift zones on the islands with landslides propagating perpendicular to the rift orientation however this does not explain the uneven distribution of landslides on some islands which seems to indicate that unstable flanks are a weakness that can be carried forward during island development this may occur because certain island flanks are steeper extend to greater water depths or are less buttressed by the surrounding topography and because volcanic production following a landslide my be concentrated in the landslide scar thus focussing subsequent landslide potential in this area landslides are primarily a result of volcanic construction to a point where the mass of volcanic products fails under its own weight although the actual triggering factors are poorly understood they may include or be influenced by dyke intrusion pore pressure changes related to intrusion seismicity or sealevel climate changes a possible relationship between caldera collapse and landsliding on tenerife is not in our interpretation supported by the available evidence

the 1883 and late prehistoric eruptions of augustine volcano alaska abstract the eruptive history of augustine volcano has been characterized by cycles of growth and destruction of the volcano repeated failure of 5 10 of the edifice has produced mobile debris avalanches that reached the sea on all sides high lava extrusion rates rapidly restore the volcano to its pre failure configuration this equilibrium between constructive and destructive processes has resulted in a relatively low lava dome complex surrounded by an apron of volcaniclastic debris three times the volume of the dome complex the most recent edifice collapse occurred in 1883 producing the 0 3 km3 burr point debris avalanche deposit three major slide blocks extended the shoreline up to 2 km and produced a tsunami that swept across cook inlet hummock morphologies change from a proximal radial orientation to a dominantly transverse alignment reflecting deceleration and compression of the avalanches as they enter the sea the breached crater formed by collapse was then largely filled by a 0 09 km3 lava dome and a 0 04 km3 lava flow travelled down the north flank lithic block and ash flows and pyroclastic surges reached the coast the burr point avalanche deposit partially overlaps the rocky point debris avalanche deposit to the west that was probably emplaced 200 400 years b p a major collapse event at ca 1540 110 a d produced the west island debris avalanche ending a period of expansion of the western side of the island an accompanying lateral blast overtopped the avalanche covering a 40 sector of the west flank the plinian tephra layer b may also have been erupted at the time of the west island eruption today augustine volcano has rebuilt itself to a size similar to that which preceded the last edifice failure in 1883 the frequency of past collapses three in the last 500 years suggests that summit collapse is a possibility during any future eruption the next major collapse is expected to involve 0 1 0 5 km3 of the summit the ensuing debris avalanche would likely reach the coast producing a tsunami that could impact populated areas of the kenai peninsula the largest tsunami would result from collapse in directions other than to the north or west tsunami magnitude is contingent on failure volume direction and timing with respect to tides

epiclastic volcanic debrites evidence of flow transformations between avalanche and debris flow processes middle ordovician baie verte peninsula newfoundland canada abstract the balsum bud cove formation of the snooks arm group eastern baie verte peninsula newfoundland contains intervals of epiclastic mafic volcanic debrites characterized by textures indicative of gravity flow evolution in a submarine setting these proximal to distal and aggradational deposits record a downslope change from debris avalanche to cohesionless debris flow processes this change involves the mechanical formation of small cobble to granular matrix due to apparent crushing and grinding of large angular basalt clasts during downslope movement this flow evolution has been studied in two measured sections in the upper debrite member of the balsum bud cove formation along snooks arm avalanche and proto debris flow deposits have been studied in the stratigraphically lower and more proximal section at haggis point an upper and more distal section devil s splitting table 20 30 m above haggis point contains mostly channelized basalt clast debris flow deposits which are chaotic or crudely inversely graded and amalgamated with the underlying flow units some inversely graded cohesionless debris flows observed at devil s splitting table contain basaltic clasts 20 100 cm in diameter supported at or near their tops in an effort to better understand the flow dynamics of the debrites observed at haggis point and devil s splitting table individual flow units in both sections were analysed to determine original flow thickness at initiation slope angle at flow initiation and flow velocity using equations from takahashi 1978 mechanical characteristics of debris flow j hydraul div am soc civ eng 104 hyb 8 1153 1159 and takahashi 1981 debris flow ann rev fluid mech 13 57 77 which are applicable to both to subaerial and submarine debris flows flow velocities ranging from 6 22 to 7 78 m s were calculated for proto and cohesionless debris flows at haggis point initiation slopes range from 12 3 to 16 7 an avalanche deposit at haggis point attained a velocity of 28 87 m s cohesionless debris flows at devils splitting table had a range of flow velocities of 5 86 12 32 m s at calculated slopes of 4 8 18 8 with the exception of the avalanche velocity these examples are consistent with velocities observed or calculated for other high slope submarine debris flow deposits the calculated initiation slopes and velocities indicate 5 11 km of potential avalanche debris flow run out in the upper debrite the epiclastic volcanic apron observed in the upper debrite outcrops along snooks arm is progradational it consists of a proximal apron dominated by avalanche and proto debris flow deposits and a distal apron dominated by highly channelized cohesionless debris flows and sandy turbidites

deep sea volcaniclastic sedimentary systems an example from la fournaise volcano reunion island indian ocean a volcaniclastic sedimentary fan extending to water depths of 4000 m is characterized using gravity cores camera surveys high resolution sonar images seismic records and bathymetry from the submarine portion of la fournaise volcano reunion island a basaltic shield volcano in the sw indian ocean three main areas are identified from the study 1 the proximal fan extending from 500 m water depth down to 2000 m water depth 2 the outer fan extending from 2000 m water depth down to 3600 m water depth 3 the basin extending beyond 3600 m water depth within these three main areas seven distinct submarine environments are defined the proximal fan is characterized by volcanic basement outcrops sedimentary slides deep water deltas debris avalanche deposits and eroded floor in the valley outlets the outer fan is characterized by a discontinuous fine grained sedimentary cover overlying coarse grained turbidites or undifferentiated volcanic basement the basin is characterized by hemipelagic muds and fine grained turbidites interbedded with sandy and gravelly turbidite lobes the evolution of the deep sea volcaniclastic fan is strongly influenced by sector collapses such as the one which occurred 0 0042 ma ago this collapse produced a minimum of 6 km3 of debris avalanche deposit in the proximal area the feeding regime of the deep sea fan is alluvial dominated before the occurrence of any sector collapse and lava dominated after the occurrence of a sector collapse the main deep water lava fed delta is prograding among the blocks of the debris avalanche deposits as a result of turbidity flows occurring on the delta slope these turbidity flows are triggered routinely by wave action earthquakes and accumulation of new volcanic debris on top of the deltas both turbidity currents triggered on the deep water delta slope and those triggered by debris avalanche reworked volcaniclastic material as far as 100 km from the shore line

dynamics of the december 2002 flank failure and tsunami at stromboli volcano inferred by volcanological and geophysical observations 1 the 2002 effusive flank eruption at stromboli volcano started on december 28 after several months of strong explosive activity at the summit craters on december 30 the seismic network recorded two large flank failures and associated tsunami waves this is the first time that a flank collapse and tsunami and their associated phenomena have been recorded by a multi disciplinary monitoring system volcanological and geophysical monitoring as well as thermal surveys performed immediately before and after the failure allowed us to define and interpret the sequence of events the still on going eruption has provided for the first time the opportunity to look into the dynamics of stromboli s effusive eruptions flank failure and landslide formation and their potential hazard

valid garnet biotite gb geothermometry and garnet aluminum silicate plagioclase quartz gasp geobarometry in metapelitic rocks abstract at present there are many calibrations of both the garnet biotite gb thermometer and the garnet aluminum silicate plagioclase quartz gasp barometer that may confuse geologists in choosing a reliable thermometer and or barometer to test the accuracy of the gb thermometers we have applied the various gb thermometers to reproduce the experimental data and data from natural metapelitic rocks of various prograde sequences inverted metamorphic zones and thermal contact aureoles we have concluded that the four gb thermometers perchuk l l lavrent eva i v 1983 experimental investigation of exchange equilibria in the system cordierite garnet biotite in saxena s k ed kinetics and equilibrium in mineral reactions springer verlag new york berlin heidelberg pp 199 239 kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 holdaway m j 2000 application of new experimental and garnet margules data to the garnet biotite geothermometer american mineralogist 85 881 892 model 6av kaneko y miyano t 2004 recalibration of mutually consistent garnet biotite and garnet cordierite geothermometers lithos 73 255 269 model b are the most valid and reliable of this kind of thermometer more specifically we prefer the holdaway holdaway m j 2000 application of new experimental and garnet margules data to the garnet biotite geothermometer american mineralogist 85 881 892 and the kleemann and reinhardt kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 calibrations due to their small errors in reproducing the experimental temperatures and good accuracy in successfully discerning the systematic temperature changes of the different sequences in addition after applying the gasp barometer to 335 natural metapelitic samples containing one kind of aluminosilicate and 33 natural metapelitic samples containing two kinds of aluminosilicate as well as to rocks in limited geographic areas and thermal contact aureoles we propose that the calibrations of holdaway holdaway m j 2001 recalibration of the gasp geobarometer in light of recent garnet and plagioclase activity models and versions of the garnet biotite geothermometer american mineralogist 86 1117 1129 and newton and haselton newton r c haselton h t 1981 thermodynamics of the garnet plagioclase al2sio5 quartz geobarometer in newton r c navrotsky a wood b j eds thermodynamics of minerals and melts new york springer verlag 131 147 based on kleemann and reinhardt s kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 thermometer are the most valid gasp barometers other gb thermometers and gasp barometers are not recommended

recent surface displacements in the upper rhine graben preliminary results from geodetic networks abstract datasets of the gnss upper rhine graben network gurn and the national levelling networks in germany france and switzerland are investigated with respect to current surface displacements in the upper rhine graben urg area gurn consists of about 80 permanent gnss global navigation satellite systems stations the terrestrial levelling network comprises 1st and 2nd order levelling lines that have been remeasured at intervals of roughly 25 years starting in 1922 compared to earlier studies national institutions and private companies made available raw data allowing for consistent solutions for the urg region we focussed on the southern and eastern parts of the investigation area our preliminary results show that the levelling and gnss datasets are sensitive to resolve small surface displacement rates down to an order of magnitude of 0 2 mm a and 0 4 mm a respectively the observed horizontal velocity components for a test region south of strasbourg obtained from gnss coordinate time series vary around 0 5 mm a the results are in general agreement with interseismic strain built up in a sinistral strike slip regime since the accuracy of the gnss derived vertical component is insufficient data of precise levelling networks is used to determine vertical displacement rates more than 75 of the vertical rates obtained from a kinematic adjustment of 1st order levelling lines in the eastern part of urg vary between 0 2 mm a and 0 2 mm a indicating that this region behaves stable higher rates up to 0 5 mm a in a limited region south of freiburg are in general agreement with active faulting we conclude that both networks deliver stable results that reflect real surface movements in the urg area we note however that geodetically observed surface displacements generally result from a superposition of different effects and that a separation in tectonic and non tectonic processes needs additional information and expertise

emplacement mechanisms of contrasting debris avalanches at volcan mombacho nicaragua provided by structural and facies analysis we study the lithology structure and emplacement of two debris avalanche deposits dads with contrasting origins and materials from the quaternary holocene mombacho volcano nicaragua a clear comparison is possible because both dads were emplaced onto similar nearly flat 3 slope topography with no apparent barrier to transport this lack of confinement allows us to study in nature the perfect case scenario of a freely spreading avalanche in addition there is good evidence that no substratum was incorporated in the events during flow so facies changes are related only to internal dynamics mombacho shows evidence of at least three large flank collapses producing the two well preserved debris avalanches of this study one on its northern flank las isletas directed northeast and the other on its southern flank el crater directed south other south eastern features indicate that the debris avalanche corresponding to the third collapse la danta occurred before las isletas and el crater events the materials involved in each event were similar except in their alteration state and in the amount of substrata initially included in the collapse while el crater avalanche shows no signs of substratum involvement and has characteristics of a hydrothermal weakening related collapse the las isletas avalanche involves significant substratum and was generated by gravity spreading related failure the latter avalanche may have interacted with lake nicaragua during transport in which case its run out could have been modified through a detailed morphological and structural description of the mombacho avalanches we provide two contrasting examples of non eruptive volcanic flank collapse we show that remarkably even with two distinct collapse mechanisms the debris avalanches developed the same gross stratigraphy of a coarse layer above a fine layer this fine layer provided a low friction basal slide layer whereas dad layering and the run outs are roughly similar the distribution of structures is different and related to lithology las isletas has clear proximal faults replaced distally by inter hummock depressions where basal unit zones are exhumed whereas el crater has faults throughout but the basal layer is hidden in the distal zone hummocky forms depend on material type with steep hummocks being formed of coherent lava units and low hummocks by matrix rich units in both avalanches extensional structures predominate the upper layers exclusively underwent longitudinal and lateral extension this is consistent with evidence of only small amounts of block to block interactions during bulk horizontal spreading the base of the moving mass accommodated transport by large amounts of simple shear we suggest that contractional structures and inter block collisions seen in many other avalanches are artifacts related to topographic confinement

the stromboli 2002 tsunamigenic submarine slide characteristics and possible failure mechanisms 1 on 30 december 2002 a major instability event deeply involving the submarine slope occurred on the sciara del fuoco on the western flank of stromboli volcano in the aeolian islands tsunami waves with a maximum runup of over 10 m in stromboli were generated having a measurable impact as far as the sicily coast just 10 months before the event a multibeam bathymetry had been collected in the area down to 1000 m of depth a repetition of the survey after the slide allowed the unique opportunity to verify the occurrence of a large submarine slide and to define volumes involved and morphology generated by the event through the comparison of the preevent and postevent bathymetric grids a morphological characterization of the slope before and after the submarine landslide is presented showing how the preexisting features interacted with the slide event in controlling the instability mechanisms of the submarine failure are discussed on the basis of the geometrical characters of the landslide event structural and stratigraphic setting of the submerged slope and geotechnical considerations on the behavior of slope material

the 55 to 60 ka te whaiau formation a catastrophic avalanche induced cohesive debris flow deposit from proto tongariro volcano new zealand te whaiau formation is a massive volcaniclastic deposit interbedded within gravelly and sandy volcanogenic sediments of the northwestern tongariro ring plain the ca 0 5 km3 deposit comprises a clay rich matrix supported diamicton with lithological and physical properties that are typical of a cohesive debris flow deposit clays identified in the matrix are derived from hydrothermally altered andesite lava and pyroclastic rocks the distribution pattern of the deposit and the nature of the clay matrix point to a source area that was located in the vicinity of mt tongariro s current summit 1967 m most of the proximal zone is buried under late pleistocene lavas forming the northwestern flank of the massif in contrast the medial and distal zones are well exposed to the northwest in the whanganui river catchment lithofacies exposed in these latter zones contain isolated volcaniclastic megaclasts and well preserved jointed blocks of andesite small hummocks up to 5 m high are present only in the distal margins of the deposit based on these observations possible source areas and analogy with similar deposits elsewhere we infer that te whaiau formation was initiated as a fluid saturated debris avalanche that transformed downstream into a single cohesive debris flow it is interpreted that the mass flow was initially confined to the northwestern flank of tongariro before spreading laterally onto the lowlands to the northwest the resulting heterolithological diamicton filled stream channels in the western sector of the tongariro ring plain at 15 km from source the debris flow encountered an elevated terrain which acted as a barrier to further spreading to the north the stratigraphy of the cover beds and k ar data on an underlying lava indicate that te whaiau formation was emplaced between 55 and 60 ka a cool period characterized by intense volcaniclastic sedimentation around the tongariro massif jigsaw fit fractured volcanic bombs suggest that an explosive eruption through hydrothermally altered rock and pyroclastic deposits probably triggered the mass flow the characteristics of the deposit indicate that a large portion of the proto tongariro edifice collapsed en masse to form the initial avalanche hence we infer that the current morphology of tongariro volcano is derived not only from glacial erosion but also from gravitational failure prehistoric eruptions and current geothermal activity on the upper northern and western slopes of the tongariro massif suggest that avalanche induced debris flows must be considered a potential future volcanic hazard for the region

multiple sector collapses at stromboli volcano italy how they work this paper demonstrates that four large sector collapses have affected the nw flank of the stromboli volcano in the past 13 ka alternating with growth phases in order to contribute to the evaluation of the critical conditions which trigger lateral collapses a reconstruction of the geometry of each collapse of the volcano edifice in the four stages that preceded the relative collapse events is also presented and a computation of the landslide volume this reconstruction is based on new field data plotted in three dimensions prior to the initial 13 ka collapse the volcano was 1125 100 m high above sea level the collapse had a volume of 2 23 0 87 km3 whereas the pre collapse volcano volume was 218 8 7 7 km3 the next edifice that failed was 900 70 m high a s l the collapse volume was 1 0 54 km3 with a precollapse volcano volume of 201 4 5 4 km3 the edifice then grew to 1000 60 m a s l the third collapse had a volume of 1 08 0 39 km3 and occurred within a volcano with a volume of 209 1 4 6 km3 this was followed by a new growth phase followed by the last collapse with a volume of 0 73 0 22 km3 the volcano volume was about the same as the present one the present active crater zone is at 780 m a s l in the first three collapses sliding surfaces cut the main magma conduit in the last collapse the upper scarp coincided with the conduit location dyking along a main ne trending weakness zone across the volcano summit exerted a lateral force for collapse inception the decrease of the landslide volumes with the age and the concentric scarps of the four collapses suggest that the younger sliding planes tended to become more superficial and to decrease the areal extent this is interpreted as due to a successively weaker eruptive products from dominantly lavas to dominantly pyroclastics and b the feedback effects between collapses and dykes that injected along the lateral segments of the first collapse slide plane

facies architecture of the upper oligocene submarine smrekovec stratovolcano northern slovenia abstract the upper oligocene smrekovec volcanic complex svc represents the remains of a submarine stratovolcano which underwent early miocene tectonic dissection and large scale displacement along the periadriatic line according to the lithofacies architecture abundance and spatial distribution central medial and distal zones of the former volcano edifice have been recognized the zones extend at a distance of 0 2 km 2 5 km and 5 20 km south of the periadriatic line respectively lavas shallow intrusive bodies autobreccia peperite and hyaloclastite deposits occur mainly in the central zone which is extensively altered under hydrothermal conditions characterised by the development of zeolites mainly laumontite prehnite chlorite albite and epidote explosive volcanic activity intensified with the evolution of magma from basaltic andesitic to dacitic gas and water supported eruption fed density flows are assumed their deposits show lithofacies organisation in pyroclastic depositional units pdus similar to either volcaniclastic turbidites type 1 or thin subaqueous ignimbrites type 2 volcaniclastic debris flow deposits are developed as volcaniclastic breccia and sandy debris flow deposits the former occurs in the central and medial zones and the latter occurs in the medial zone only the most widespread lithofacies in the svc are volcaniclastic turbidite deposits three types of sedimentary unit tsu have been distinguished type 1 is 2 5 m thick and dominated by the massive division it mainly occurs in the central zone type 2 is 0 7 3 5 m thick and occurs in the central and medial zones it comprises the massive division bedded fining and thinning upward division and a horizontally wavy and cross laminated division topped by massive fine grained tuff type 3 is 0 1 1 5 m thick and mainly occurs in the distal zone the massive division is absent and thinly bedded and laminated divisions are topped by massive fine grained tuff volcaniclastic turbidites were settled from low density turbidity currents and related suspension clouds mixed volcaniclastic siliciclastic deposits are subordinate in occurrence and restricted to the distal zone they are commonly reworked by bottom currents

anatomy and kinematics of oblique continental rifting revealed a three dimensional case study of the southeast upper rhine graben germany the upper rhine graben is a north northeast trending small displacement crustal scale rift of tertiary age retrodeformation of its southeastern part demonstrates that it is a product of sinistral oblique rifting early extension was toward 80 later the major stretching axis changed to a 60 direction the modeling results suggest that the eastern main border fault developed first and that faulting later propagated into the evolving graben interior considerable along strike variations in heave throw and displacement are evident displacement partitioning causes warping of the rift floor with a 30 35 km wavelength we consider this to be a characteristic of oblique rifting contact deformation of the wall rocks to the major faults may have caused widespread smaller scale faulting and brecciation and may be the location of later movements close spatial coincidence of the depth projections of some of the faults studied and the hypocenters of recent small earthquakes indicates continuing activity of the fault system apparently three fault segments in the freiburg area are currently active and may be an increased earthquake risk

determination of displacements in the upper rhine graben area from gps and leveling data the upper rhine graben is a north northeast trending rift system which belongs to the european cenozoic rift system today the southern part of the graben is seismically still active earthquakes of magnitude 5 have a recurrence time of approximately 30 years in order to monitor and to determine the displacements in the study area gps measurements have been carried out in two campaigns 1999 and 2000 and observations of the available permanent stations have been processed in 2002 owing to the small size of deformations expected high accuracy requirements must be met by the gps processing in order to achieve these requirements precise antenna modeling has been introduced into the processing as expected the short time span has not enabled to detect significant displacements from the gps measurements the deformation analysis shows that the horizontal displacement rates do not exceed 1 mm year which is compatible with the geological information owing to the fact that the accuracy of positioning with gps for the vertical coordinates is lower than for the horizontal coordinates the determination of vertical displacements has been carried out using the leveling technique in the area of freiburg first order and second order leveling lines have been chosen for the detection of local displacements on the weinstetten on the lehen schonberg and on the main border fault mbf some sections of these faults are still active today significant vertical displacements have been observed at the weinstetten fault in the area of bad krozingen and on the mbf in freiburg the displacement rates 1925 1984 are 0 17 0 01 mm year and 0 25 0 02 mm year respectively the results agree very well with the results of seismotectonic investigations and show that ongoing displacements can be found on the northern part of the lehen schonberg fault in the vicinity of eichstetten and on the mbf in the vicinity of freiburg

metamorphic evolution of granulites in the minto block northern quebec extraction of peak p t conditions taking account of late fe mg exchange in the central minto block of northern quebec the lake minto and goudalie domains are dominated respectively by orthopyroxene bearing plutonic suites granite granodiorite and diatexite and a tonalitic gneiss complex both of which contain scattered remnant paragneisses two main granulite grade mineral assemblages are observed in the paragneiss garnet grt orthopyroxene opx plagioclase quartz gopq and garnet grt cordierite crd sillimanite plagioclase quartz gcspq these show distinct lithological associations with the gcspq assemblages occurring exclusively within the diatexite in the lake minto domain petrogenetic grid considerations demonstrate that the gopq rocks are higher grade than the gcspq rocks maximum temperatures for gopq rocks obtained from equilibria based on al solubility in orthopyroxene in equilibrium with garnet range from 950 to 1000d c significantly higher than garnet orthopyroxene fe mg exchange temperatures of 700 50d c the latter probably representing a closure temperature below peak conditions the al temperatures were corrected for late cation exchange by adjusting the fe fe mg ratios in garnet and orthopyroxene to achieve internal consistency between the gopq thermometers and barometers grt crd thermometry records temperatures of 750 50d c peak p t conditions range from 5 6 kbar and 750 800d c in the goudalie and eastern lake minto domains to 7 10 kbar and 950 1000d c in the western and central lake minto domain this variability contrasts with the uniform crustal pressures of 5 1 kbar recorded by the gcspq assemblages in the diatexites and the hornblende granodiorites c 4 5 kbar across the same area the gopq rocks are inferred to record earlier p t conditions that prevailed before the formation of gcspq assemblages and the intrusion of the granodiorites partial p t paths in gopq rocks from both domains based on net transfer equilibria corrected for fe mg resetting document cooling of 100 250d c from thermal peak conditions concomitant with a modest pressure decrease of 2 3 kbar although textures diagnostic of isobaric cooling are not developed the paths are consistent with a tectonic model in which granulite metamorphism and crustal thickening in the minto block were consequences of magmatic underplating the progression from higher p t conditions recorded by gopq assemblages to lower p t conditions recorded by gcspq assemblages is attributed to variable amounts of synmagmatic uplift and cooling in a single continuous thermal event in the minto crust associated with protracted crustal magmatism in the goudalie and eastern lake minto domains where gopq and gcspq rocks and hbl granodiorites have similar p t conditions of equilibration the crust may not have been thickened as much as further west where gopq p t conditions are significantly higher than those of the hornblende granodiorites and the gcspq rocks

geological constraints on the emplacement mechanism of the parinacota debris avalanche northern chile the holocene parinacota volcanic debris avalanche ca 8 000 years b p is located in the central andes of northern chile the avalanche formed by the sector collapse of a major stratovolcano adjacent to a lake basin in a single catastrophic event the deposit has an estimated volume of ca 6 km3 a run out of over 22 km and covers more than 140 km2 of the surrounding terrain the values of the heim coefficient 0 08 and the ratio a v 2 3 ca 50 where a is the area covered and v the volume of the deposit indicate high mobility of the avalanche debris in transport two avalanche units can be distinguished the lower unit consists mainly of blocks of rhyodacitic lavas and domes and pyroclastic flow deposits and glacial fluvial and lacustrine sediments the upper unit consists of a coarse grained breccia with little matrix largely composed of andesite blocks which are angular with little or no rounding by abrasion the avalanche displays pronounced hummocky topography in which hummock volume and amplitude as well as maximum block size within individual hummocks tends to decrease with transport distance and towards the lateral margins of the avalanche deposit some surfaces of individual breccia blocks are covered by tens to thousands of small scale impact marks indicating that neighbouring blocks were vibrating and colliding without significant shearing motion most of the deformation and shearing was instead accommodated in a basal layer of wet structureless sediments incorporated into the avalanche debris from the inundated lake basin we propose that the ancestral parinacota stratovolcano collapsed because of loading of underlying fluvioglacial and lacustrine sediments the edifice disintegrated during collapse along existing fractures into large rock domains volumes from 10 to greater than 1 106 m3 which were transported with little internal deformation and then fragmented into hummocks of breccia as they were deposited the decrease of hummock volume with distance suggests that material that travelled further broke up and had an initial greater kinetic energy

neotectonics and intraplate continental topography of the northern alpine foreland research on neotectonics and related seismicity has hitherto been mostly focused on active plate boundaries that are characterized by generally high levels of earthquake activity current seismic hazard estimates for intraplate domains are mainly based on probabilistic analyses of historical and instrumental earthquake catalogues the accuracy of such hazard estimates is limited by the fact that available catalogues are restricted to a few hundred years which on geological time scales is insignificant and not suitable for the assessment of tectonic processes controlling the observed earthquake activity more reliable hazard prediction requires access to high quality data sets covering a geologically significant time span in order to obtain a better understanding of processes controlling on going intraplate deformation the alpine orogen and the intraplate sedimentary basins and rifts in its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that deformation of the northern alpine foreland is still on going and will continue in the future this has major implications for the assessment of natural hazards and the environmental degradation potential of this densely populated area we examine relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland and their implications for tectonically induced topography for the environmental tectonics project entec the upper and lower rhine graben urg and lrg and the vienna basin vb were selected as natural laboratories the vienna basin developed during the middle miocene as a sinistral pull apart structure on top of the east alpine nappe stack whereas the upper and lower rhine grabens are typical intracontinental rifts the upper rhine graben opened during its late eocene and oligocene initial rifting phase by nearly orthogonal crustal extension whereas its neogene evolution was controlled by oblique extension seismic tomography suggests that during extension the mantle lithosphere was partially decoupled from the upper crust at the level of the lower crust however whole lithospheric folding controlled the mid miocene to pliocene uplift of the vosges black forest arch whereas thermal thinning of the mantle lithosphere above a mantle plume contributed substantially to the past and present uplift of the rhenish massif by contrast oblique crustal extension controlling the late oligocene initial subsidence stage of the lower rhine graben gave way to orthogonal extension at the transition to the neogene the entec project integrated geological geophysical geomorphologic geodetic and seismological data and developed dynamic models to quantify the societal impact of neotectonics in areas hosting major urban and industrial activity concentrations the response of europe s intraplate lithosphere to late neogene compressional stresses depends largely on its thermo mechanical structure which in turn controls vertical motions topography evolution and related surface processes

granulite facies metamorphism and retrogressive evolution of the monts du lyonnais metabasites massif central france abstract garnet bearing pyriclasites have been found within the monts du lyonnais formation near st andrela cote in the eastern part of the massif central the rocks appear to have differentiated from a tholeiitic magma of continental affinity and they may be genetically related to quartzofeldspathic granulites considered to be the products of crustal melts by means of electron microprobe analyses the consistent pressure and temperature estimates based essentially on pyroxene garnet equilibria show that the peak of metamorphism was at about 860 c and 10 kbar furthermore this study tends to confirm the affiliation of monts du lyonnais granulites to the early variscan granulite eclogite facies metamorphism which extends from bohemia to spain through central europe this event may be expected in the vicinity of an ancient suture zone where a continental collision followed a subduction

crustal velocity field of western europe from permanent gps array solutions 1996 2001 we derive a new geodetic velocity field for western europe and the western mediterranean by rigorously combining 1 a selection of 36 itrf2000 sites 2 a solution from a subset of sites of the european permanent gps network euref epn 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy of the order of i mm yr 1 or better its analysis shows that central europe defined as east of the rhine graben and north of the alps and the carpathians behaves rigidly at a 0 4 mm yr 1 level and defines a stable europe reference frame in that reference frame we find no significant motion at sites located west of the rhine graben and on the iberian peninsula which sets an upper bound of 0 6 mm yr 1 on horizontal motion across the rhine graben and the pyrenees we find that the current strain pattern in the western alps combines e w extension and right lateral shear we confirm a counterclockwise rotation of the adriatic microplate which appears to control the strain pattern along its boundaries in the friuli area the alps and the apennines our results also suggest that the africa eurasia plate motion in the western mediterranean may be 40 50 per cent slower that the nuvel1a plate motion model and rotated 20 30 counterclockwise

recent crustal movements in the southern black forest western germany precise levelling data are examined in the southern black forest massif by comparing them analytically along levelling profiles instead of generalizing regional vertical motion trends the method emphasizes the current activity of accurately located individual structural elements measured recent crustal movement rates range from 0 2 to 1 1 mm year for the 1930 1961 1972 period the inferred motions corresponding to aseismic fault creep based on the near infrared band image of a landsat mss scene a lineament map of the study area is compared with the recent crustal movement rcm map the upper rhine graben eastern border fault between badenweiler and freiburg displays the highest rcm these displacements are consistent with the geological motion and the topographic expression of that structure within the massif both the lineament map and the rcm map demonstrate the predominant role played by wnw ese to nw se striking structures in accommodating the deformation moreover with the seismic dislocations in the southern black forest taking place also mainly on n120 and n20 faults it is most probable that these active structures are deep reaching zones of crustal weakness to some extent seismicity and rcm appear however to be mutually exclusive in their spatial distribution the seismic black forest flexure and dinkelberg block being opposed to the aseismically moving eastern and northern parts of the study area

generation and migration of coarse grained sediment waves in turbidity current channels and channel lobe transition zones large scale sediment waves composed of gravels and sands have been studied using deep water sidescan systems new data are presented from submarine channels off the canary islands and from canyon mouths off portugal data from other areas are briefly reviewed including a re interpretation of data from laurentian fan in order to summarise the varied morphology and setting of these bedforms coarse grained sediment waves are found in the proximal dominantly bypassing areas of deep water turbidite systems within canyons channels and channel lobe transition zones wave heights are in the region of 1 10 m and wavelengths are up to several hundred metres the distribution of waves and sparse sedimentological evidence from modern and ancient sediment wave fields suggests that initial transport and deposition of coarse sediment occurs within a high density turbidity current and not as a non newtonian debris flow in some cases the development of pronounced wave asymmetry and evidence of wave disruption and reworking suggests that the wave morphology is at least partially controlled by a later phase of low density turbidity flow grain size also appears to exert some control on wave morphology for example gravel rich waves have a greater height for the same wavelength than sand rich waves coarse grained sediment waves are often difficult to recognise on the seafloor because of reworking or burial by younger turbidity currents and are equally difficult to recognise in outcrop because of their large size

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

the stromboli volcano landslides of december 2002 a seismological description 1 we analyse seismograms of the slump episodes at stromboli on december 30 2002 using a simple single force model we estimate the volume involved in the individual subevents and attempt a chronological reconstruction of the whole process our results indicate the occurrence of two main events that could be interpreted as a submarine slump which caused the observed tsunami and a subaerial slump which did not produce destructive sea waves a total volume of about 20 106 m3 results for the submarine event which developed over about 2 minutes with several distinct detachments the first and largest displacing a volume of 10 8 106 m3 the second subaerial slump involved at least 2 5 106 m3 in about 90 s a large long period pulse is also recognizable in the seismograms of the stromboli station we tentatively interpret this feature as tilt caused by the water load associated with the inundation in the ficogrande area on the northeastern side of the island

sedimentary signatures of the entrance of coarse grained volcaniclastic flows into the sea the example of the breccia units of the las palmas detritic formation mio pliocene gran canaria eastern atlantic spain abstract the transformations of volcaniclastic gravity flows entering the sea remain poorly understood they are recorded by sedimentary signatures in the volcaniclastic sedimentation of the mio pliocene las palmas detritic formation lpdf of the volcanic island of gran canaria these gravity flows are contemporaneous with an erosive period on the island succeeding the emplacement of the fataga volcanic group and the beginning of the evolution of the roque nublo stratovolcano the sedimentary section that crops out at the mouth of a paleobarranco at las cuevas del guincho comprises subtidal calcareous and clastic sediments affected by wave and storm action units 1 and 3 beach gravels unit 4 volcaniclastic deposits represented by reworked phonolitic pyroclastic deposits unit 1 breccia deposits that contain juvenile and phonolitic gravels and blocks mainly incorporated at the shoreline unit 2 and a debris avalanche deposit at the top unit 5 the breccia deposits display a reversely graded base which disappears distally as a result of seawater incorporation and liquidization of the volcaniclastic mass and mixing with marine sediment this breccia unit is interpreted as having been emplaced by a granular mass flow after transformation of a block and ash flow deposit that entered the sea in the debris avalanche deposits thermal quenching of juvenile basaltic lava clasts and large inclined clastic intrusions of underlying marine sediments suggest that the debris avalanche entered the sea rapid subaqueous emplacement of the granular mass flow and of the debris avalanche deformed the sedimentary substratum water incorporation reduced the influence of the volcaniclastic flows on the substratum ams data confirm the effect of water ingestion and correlative loss of cohesion and allow also reconstruction of paleoflow directions that were normal to the paleoshoreline of the northern coast of gran canaria all these volcaniclastic gravity flow deposits and their textural characteristics are particularly useful in the reconstruction of processes that occur at the subaerial submarine transition and for the location of ancient shorelines

constraining the efficiency of turbidity current generation from submarine debris flows and slides using laboratory experiments abstract results from a small set of laboratory experiments are presented here that help further constrain the processes governing the production of turbidity currents from impulsive failures of continental shelf and slope deposits three mechanisms by which sediment can be transferred from a parent debris flow to a less dense turbidity current were observed and quantified these mechanisms are grain by grain erosion of sediment from the leading edge of the parent flow detachment of thin layers of shearing material from the head of the parent flow and turbulent mixing at the head of the parent flow which transfer process dominates an experimental run depends on whether the large dynamic stresses focused on the head of the debris flow are sufficient to overcome a effective yield strength for the parent sediment water mixture and on whether the dynamic stresses are sufficient to induce the turbulent flow of the parent mixture analysis of data from marr et al geol soc am bull 113 2001 1377 and mohrig et al geol soc am bull 110 1998 387 support the use of a shear strength to dynamic stress ratio in constraining necessary critical values for occurrence of the different production mechanisms direct sampling of turbidity currents using racks of vertically stacked siphons was used to measure both the quantity of sediment eroded from the heads of non mixing parent flows and the distribution of particle sizes transported by the developing turbidity currents acoustic backscatter imaging was used to better resolve the internal boundary separating any turbulent mixing zone near the front of a flow from unmodified parent material

large scale seafloor waveforms on the flanks of insular volcanoes aeolian archipelago italy with inferences about their origin abstract high resolution multibeam data in the central and eastern part of the aeolian volcanic arc southern tyrrhenian sea reveal widespread large scale waveforms on the submarine flanks of these insular volcanoes these features show high variability in wave parameters wavelength of 60 1600 m and wave height of 4 200 m and morphology from sinuous to arcuate in plan view and from undulating to stepped with very steep scarps in cross section indicating that different processes at variable spatial and temporal scale are responsible for their genesis by relating the morphological characters of the different waveforms and the local boundary conditions morphological setting regional slope gradients sediment source and dynamics where these features form we were able to distinguish bedforms formed by sedimentary gravity flows from bedform like features due to gravity instability processes in detail bedforms have been interpreted as coarse grained sediment waves according to their wave parameters geometry and texture bedforms are always found where the slope gradients markedly decrease to values

tectonic evolution of proterozoic rocks in the cimarron mountains northern new mexico usa abstract portions of three proterozoic tectonostratigraphic sequences are exposed in the cimarron mountains of new mexico the cimarron river tectonic unit has affinities to a convergent margin plutonic volcanic complex igneous hornblende from a quartz diorite stock records an emplacement pressure of 2 2 6 kbar rocks within this unit were subsequently deformed during a greenschist facies regional metamorphism at 4 5 kbar and 330 50 c the tolby meadow tectonic unit consists of quartzite and schist mineral assemblages are indicative of regional metamorphism at pressures near 4 kbar and temperatures of 520 20 c a low angle ductile shear zone separates this succession from gneisses of the structurally underlying eagle nest tectonic unit gneissic granite yields hornblende pressures of 6 8 kbar pelitic gneiss records regional metamorphic conditions of 6 7 kbar and 705 15 c overprinted by retrogression at 4 kbar and 530 10 c comparison of metamorphic and retrograde conditions indicates a p t path dominated by decompression and cooling the low angle ductile shear zone represents an extensional structure which was active during metamorphism this extension juxtaposed the tolby meadow and eagle nest units at 4 kbar and 520 c both units were later overprinted by folding and low grade metamorphism and then were emplaced against the cimarron river tectonic unit by right slip movement along the steeply dipping fowler pass shear zone an argon isotope correlation age obtained from igneous hornblende dates plutonism in the cimarron river unit at 1678 ma muscovite associated with the greenschist facies metamorphic overprint yields a 40 ar 39 ar plateau age of 1350 ma by contrast rocks within the tolby meadow and eagle nest units yield significantly younger argon cooling ages hornblende isotope correlation ages of 1394 1398 ma are interpreted to date cooling during middle proterozoic extension muscovite plateau ages of 1267 1257 ma appear to date cooling from the low grade metamorphic overprint the latest ductile movement along the fowler pass shear zone post dated these cooling ages argon released from muscovites of the eagle nest tolby meadow composite unit at low experimental temperatures yields apparent ages of c 1100 ma similar ages are not obtained north east of the fowler pass shear zone suggesting movement more recently than 1100 ma

morpho sedimentary characteristics of the volcaniclastic apron around stromboli volcano italy abstract submarine portions of stromboli volcano account for about 98 of the whole extent of the volcanic edifice and are mostly covered by volcaniclastic sediments that made up a modern volcaniclastic apron the architecture and main sedimentary processes acting within the apron are depicted through the integration of geophysical evidence multibeam long range side scan sonar and seismic data and seafloor sampling the apron shows on the whole a large variability both across and along slope of morphologies and deposits related to mass wasting and reworking processes passing into areas covered by hemipelagic sedimentation a large spectrum of erosive depositional features was recognized on the surface of the apron on shallower areas i e submerged shelves shore platforms and depositional terraces submarine features related to wave action and sea level fluctuations are present they mainly act as temporary storing and reworking areas for volcaniclastic material derived from subaerial portions unconfined cohesionless inertial flows commonly dominate the upper slope where gradients are very high up to 35 and grain to grain and grain to bed collisions are favoured within the flows these flows tend to evolve into turbidity currents on the lower slope in response to a marked decrease of slope gradients below 8 generating various erosive depositional features such as erosive furrows troughs channel levee features and coarse grained sediment waves the most active area of the apron lies offshore sciara del fuoco on the nw flank where a large amount of coarse grained volcaniclastic material derived by the persistent strombolian activity is collected and deposited by means of high and low density turbidity currents on the lower slope down to 2600 m bsl more than 20 km far from the island conversely other areas are mostly dominated by deposition via settling of suspended sediments related both to hemipelagic sedimentation and to the dispersion of fine tephras by the prevailing wind and marine currents such processes interfinger and overlie in space and time giving rise to a very complex morpho sedimentary facies distribution however the structural bilateral symmetry of stromboli volcano allows defining distinct morpho sedimentary zones where one or more type of processes dominates and related different stratal architecture of the apron the unbuttressed portions of the island nw and se are characterized by the emplacement of wide and thick debris avalanche deposits volume in the order of 1 2 km 3 for each event related to large scale sector collapses representing the most important and efficient mass wasting processes making up the apron such deposits are embedded within different volcaniclastic sequences and can be eroded or exhumed by successive gravity flows the result is a highly complex both spatially and vertically succession of facies where it is often difficult to depict an arranged series of processes conversely on buttressed flanks sw and ne a more ordered evolution of processes and deposits making up the apron is observed giving rise to a less complex apron architecture

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

a gravitational spreading origin for the socompa debris avalanche abstract socompa volcano arguably provides the world s best exposed example of a sector collapse derived debris avalanche deposit new observations lead us to re interpret the origin of the sector collapse we show that it was triggered by failure of active thrust anticlines in sediments and ignimbrites underlying the volcano the thrust anticlines were a result of gravitational spreading of substrata under the volcano load about 80 of the resulting avalanche deposit is composed of substrata formerly residing under the volcano and in the anticlines the collapse scar can be traced up to 5 km from the edifice truncating two spreading related anticlines which collapsed in the event outcrops near the volcano preserve evidence of edifice material being carried along on top of mobilised substrata on the north side of the scar the avalanche motion was initially at right angles to the failure edge structural relations indicate that immediately prior to collapse the substrata disintegrated became effectively liquidised and were ejected from beneath the edifice catastrophic mobilisation of substrata probably resulted from breakdown of ignimbrite clasts and cement it may have occurred through progressive rock fracture by high shear strain during spreading material ejected from under socompa formed a layer on which volcanic edifice debris was transported this interpretation of events explains the puzzling observation that avalanche units with the lowest gravitational potential energy moved the furthest it can also account for avalanche motion normal to the collapse scar walls ignimbrites and other rock types probably capable of similar behaviour underlie many other volcanoes identification of spreading at other sites could therefore be a first step towards assessment of the potential for this style of catastrophic sector collapse

anatomy of a submarine pyroclastic flow and associated turbidity current july 2003 dome collapse soufriere hills volcano montserrat west indies the 12 to 13 july 2003 andesite lava dome collapse at the soufriere hills volcano montserrat provides the first opportunity to document comprehensively both the sub aerial and submarine sequence of events for an eruption numerous pyroclastic flows entered the ocean during the collapse depositing approximately 90 of the total material into the submarine environment during peak collapse conditions as the main flow penetrated the air ocean interface phreatic explosions were observed and a surge cloud decoupled from the main flow body to travel 2 to 3 km over the ocean surface before settling the bulk of the flow was submerged and rapidly mixed with sea water forming a water saturated mass flow efficient sorting and physical differentiation occurred within the flow before initial deposition at 500 m water depth the coarsest components 60 of the total volume were deposited proximally from a dense granular flow while the finer components 40 were efficiently elutriated into the overlying part of the flow which evolved into a far reaching turbidity current

active tectonics of the southeastern upper rhine graben freiburg area germany the upper rhine graben has two plio quaternary depocentres usually interpreted as resulting from tectonic reactivation the southern basin near freiburg im breisgau germany contains up to 250 m of sediments beneath the younger alluvial deposits related to the current drainage system a former river network deeply entrenched in the substratum reveals a very low regional base level of early pleistocene age the offset of channels at faults allows us to infer a pleistocene reactivation of the syn rift fault pattern and the estimation of slip rates maximum vertical movements along the faults have not exceeded 0 1 mm yr since the middle pleistocene current activity is concentrated along the westernmost faults morphologic markers indicate late pleistocene reactivation of the rhine river fault and geophysical prospecting suggests a near surface offset of young sedimentary deposits the size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than mw 6 3mw 6 3 could be expected in the area with a return interval of about 8000 years extrapolated to the duration of the plio pleistocene the strain rate estimates reveal that the tectonic forcing may account for only one third to one half of the whole thickness of the plio pleistocene sediments of the basin fill thus other processes must be invoked to understand the growth of the plio pleistocene basin especially the piracy of the rhine river to the north during the early pleistocene could explain these effects

p t t paths and tectonic history of an early precambrian granulite facies terrane jining district south east inner mongolia china abstract the widespread khondalite series of south east inner mongolia consists largely of biotite sillimanite garnet gneiss and quartzo feldspathic gneiss with some marble and mafic granulite layers it has experienced two metamorphic events at c 2500 and 1900 2000 ma a pre peak stage of the first metamorphism at t 600 700 c and p 6 7 kbar is recognized by the relict amphibolite facies assemblage ky grt bt pl qtz and protected inclusions of biotite hornblende sodic plagioclase and quartz in garnet or orthopyroxene the peak stage with t c 800 50 c and p 8 10 kbar is characterized by the widespread granulite facies assemblages sil grt bt kfs pl qtz in gneiss and opx cpx pl hbl grt in granulite the p t t path suggests that the supracrustal sequence was buried in the lower crust by tectonic thickening during d1 d2 the beginning of the second metamorphism is characterized by further temperature rise to 700 c or more at lower pressure this stage is manifested by the appearance of cordierite after garnet fibrolite sil2 after biotite in gneiss and transformation of hbl1 into opx2 and cpx2 in granulite coronas of symplectitic opx2 pl2 surrounding grt1 and cpx1 in mafic granulite are interpreted as products of near isothermal decompression the p t t path may be related tectonically to waning extension of the crust by the end of the early proterozoic

pressure temperature time paths and a tectonic model for the evolution of granulites petrologic studies and application of well calibrated mineralogic thermometers and barometers reveal several important features common to many granulite terrains 1 peak metamorphic pressure and temperature conditions cluster around values of 7 5 pm 1 kbar and 800 pm 50 c implying average geothermal gradients of 30 35 c km 2 in comparison with upper amphibolite facies rocks especially in paired amphibolite granulite terrains it is evident that granulites are distinguished from amphibolites by the former s higher metamorphic temperatures but not higher pressure 3 initial cooling of granulite terrains from peak conditions is nearly isobaric for garnet closure temperatures of 600 pm 50 c the dp dt retrograde paths inferred from compositionally zoned garnet rims are 2 8 b c in most granulites 4 primary coarse sillimanite is found in most granulites and retrograde kyanite is known in a few these data suggest that granulites form as a result of anomalous thermal gradients

metamorphic conditions and 40ar39ar geochronologic contrasts across the grenvile front zone coastal labrador canada the grenville front zone on the eastern labrador coast transects lower and middle proterozoic metamorphic and plutonic rocks and embodies elements of a protracted metamorphic history that involved two periods of pre grenvillian metamorphism onto which grenvillian effects were superimposed the earliest event minimum age 1 8 ga was a granulite facies metamorphism ca 650 750 c and minimum pressure between 4 0 and 6 0 kbar that occurred prior to emplacement of plutons of the benedict mountains intrusive suite bmis and produced the white bear islands granulite complex these rocks were subsequently affected by a progressive amphibolite facies retrogression from about 700 to 550 c at 5 kbar this event was synchronous with the intrusion and or deformation of the bmis which yields rb sr isochron crystallization ages of 1 7 1 8 ga hornblende within deformed units of the bmis north of the grenville front record 40ar39ar plateau ages of 1 66 1 64 ga interpreted to date cooling through temperatures needed for intracrystalline retention of 40ar following the pre grenvillian metamorphism following the intrusion of the michael gabbro ca 1 4 ga grenvillian orogenesis was superimposed on the area during the grenvillian orogeny the area was sliced into three thrust bound blocks which contain contrasting metamorphic mineral assemblages ranging from greenschist facies in the north to lower amphibolite facies maximum 560 630 c moderate pressures in the south collectively these represent a thrust induced telescoped metamorphic sequence precise 40ar39ar dating of individual grenvillian tectonothermal events in this area is precluded by the widespread incorporation of extraneous excess 40ar components within various mineral phases

new views of granular mass flows concentrated grain fluid mixtures in rock avalanches debris flows and pyroclastic flows do not behave as simple materials with fixed rheologies instead rheology evolves as mixture agitation grain concentration and fluid pressure change during flow initiation transit and deposition throughout a flow however normal forces on planes parallel to the free upper surface approximately balance the weight of the superincumbent mixture and the coulomb friction rule describes bulk intergranular shear stresses on such planes pore fluid pressure can temporarily or locally enhance mixture mobility by reducing coulomb friction and transferring shear stress to the fluid phase initial conditions boundary conditions and grain comminution and sorting can influence pore fluid pressures and cause variations in flow dynamics and deposits

behaviour of particle laden flows into the ocean experimental simulation and geological implications the behaviour of subaerial particle laden gravity currents e g pyroclastic flows lahars debris flows sediment bearing floods and jokulhlaups flowing into the sea has been simulated with analogue experiments flows of either saline solution simple suspensions of silicon carbide sic in water or complex suspensions of sic and plastic particles in methanol were released down a slope into a tank of water the excess momentum between subaerial and subaqueous flow is dissipated by a surface wave at relatively low density contrasts between the tank water and the saline or simple suspensions the flow mixture enters the water and forms a turbulent cloud involving extensive entrainment of water the cloud then collapses gravitationally to form an underwater gravity current which progresses along the tank floor at higher density contrasts the subaerial flow develops directly into a subaqueous flow the flow slows and thickens in response to the reduced density contrast which is driving motion and then continues in the typical gravity current manner complex suspensions become dense flows along the tank floor or buoyant flows along the water surface if the mixtures are sufficiently denser or lighter than water respectively flows of initially intermediate density are strongly influenced by the internal stratification of the subaerial flow material from the particulate depleted upper sections of the subaerial flow becomes a buoyant gravity current along the water surface whereas material from the particulate enriched lower sections forms a dense flow along the tank floor sedimentation from the dense flow results in a reduction in bulk density until the mixture attains buoyancy lifts off and becomes a secondary buoyant flow along the water surface jokulhlaups lahars and debris flows are typically much denser than seawater and thus will usually form dense flows along the seabed after sufficient sedimentation the freshwater particulate mixture can lift off to form a buoyant flow at the sea surface leading to a decoupling of the fine and coarse particles flood waters with low particulate concentrations 2 may form buoyant flows immediately upon entering the ocean subaerial pyroclastic flows develop a pronounced internal stratification during subaerial run out and thus a flow splitting behaviour is probable which agrees with evidence for sea surface and underwater flows from historic eruptions of krakatau and mont pelee a pyroclastic flow with a bulk density closer to that of sea water may form a turbulent cloud resulting in the deposition of much of the pyroclasts close to the shore dense subaqueous pyroclastic flows will eventually lift off and form secondary buoyant flows either before or after the transformation to a water supported nature

subaqueous density flow processes and deposits of an island volcano landslide stromboli island italy stromboli is a 3000 m high island volcano rising to 900 m above sea level it is the most active volcano of the aeolian archipelago in the tyrrhenian sea italy major large volume 1 km 3 sector collapses four occurring in the last 13 kyr have played an important role in shaping the north western flank sciara del fuoco of the volcano potentially generating a high risk tsunami hazard for the aeolian islands and the italian coast however smaller volume partial collapses of the sciara del fuoco have been shown to be more frequent tsunami generating events one such event occurred on 30 december 2002 when a partial collapse of the north western flank of the island took place the resulting landslide generated 10 m high tsunami waves that impacted the island multibeam bathymetry side scan sonar imaging and visual observations reveal that the landslide deposited 25 to 30 10 6 m 3 of sediment on the submerged slope offshore from the sciara del fuoco two contiguous main deposit facies are recognized i a chaotic coarse grained metre sized to centimetre sized clasts deposit and ii a sand deposit containing a lower cross bedded sand layer and an upper structureless pebbly sand bed capped by sea floor ripple bedforms the sand facies develops adjacent to and partially overlying the coarse deposits characteristics of the deposits suggest that they were derived from cohesionless sandy matrix density flows flow rheology and dynamics led to the segregation of the density flow into sand rich and clast rich regions a range of density flow transitions both in space and in time caused principally by particle concentration and grain size partitioning within cohesionless parent flows was identified in the deposits of this relatively small scale submarine landslide event

towards the determination of displacements in the upper rhine graben area using gps measurements and precise antenna modelling abstract the upper rhine graben is a north northeast trending rift system which belongs to the european cenozoic rift system today the southern part of the graben is seismically still active earthquakes of magnitude 5 have a recurrence time of approximately 30 years the eucor urgent project focuses on the seismic hazards and neotectonics in the upper rhine graben and the surrounding areas within the framework of this project five institutions have created and have been maintaining a gps network in the upper rhine graben and the surrounding area in order to monitor horizontal and vertical displacements in the study area two gps campaigns have been carried out in the network to monitor and to determine the horizontal and vertical displacements in the study area the first one was observed in 1999 and the second one in 2000 in 2002 2 weeks of data of the available permanent gps reference stations in the area have also been included in the investigations these permanent stations belong to the european reference frame permanent network international gps service network satellite positioning service of baden wurttemberg reseau gps permanent france rgp reseau gps permanent dans les alpes regal and the agnes operated by the swiss positioning service due to the small size of the displacements expected high accuracy requirements must be met in the gps processing in order to achieve this the results of the available absolute antenna calibrations have been considered in the data processing too the results have shown that the application of absolute antenna calibration models is crucial for the derivation of a highly accurate displacement field without these models large discrepancies on the level of few centimetres can be observed at those stations where the observations were carried out by different antennas in the various campaigns as expectedly due to the short time span no significant displacement could be detected in the study area however the deformation analysis shows that the horizontal displacements do not exceed the level of 1 mm yr this value agrees with the results of other investigations

review of ten years of volcano deformations recorded by the ground based insar monitoring system at stromboli volcano a tool to mitigate volcano flank dynamics and intense volcanic activity abstract stromboli volcano southern italy is one of the most monitored volcano in the world with a surveillance network that includes a permanently sited ground based sar interferometer gbinsar this work is the review of the gbinsar data gained from the last decade of monitoring activity the analysis of the entire dataset of gbinsar measurements allowed the assessment of the deformation field of the northern part of the summit crater area and the sciara del fuoco depression in detail the main displacements recognized can be related to different factors 1 the inflation deflation respectively immediately before and after each new effusive event 2 the bulging of localized sectors of the volcano involved in the vent opening 3 the gravitational sliding of the sciara del fuoco infill 4 the movement of lava flows accelerations in this sector are related to sheet intrusions while the possibility of vent opening associated with small sliding or catastrophic flank failure are related to highly overpressurized sheets able to produce high displacement rate in the sciara del fuoco in the summit crater area the increases in the displacement rate are related to the pressurization of the shallow conduit system as the consequence of the variation in the magma level magmastatic pressure or to the lateral magma migration lateral conduit expansion or dike intrusion in response to the increase of the overpressure component fluctuations in the displacement rate in the summit crater area can be related to the magma overturning within the conduit with the increases in displacement rate during the upwelling of less dense magma while displacement rate decreases as the degassed magma column is pushed out from the conduit lava flows or overflows instead the decrease in the displacement rate without coeval lava outpouring could be related to the sink of the degassed magma due to density contrast between the gas poor and the gas charged magmas using the displacement rate in the summit crater area as a proxy for the variation in the pressure condition in conduit both magmastatic and overpressure components thresholds for the crises characterized by the occurrence of overflows eventually associated with major explosions and flank effusions eventually associated with paroxysmal explosions are identified small conduit overpressure will produce overflows sometimes associated with crater rim collapses while large magma overpressure will laterally expand the conduit forming ne sw striking sheets feeding eruptive vents at the base of the summit crater area and within the sciara del fuoco generating conditions of instability that can evolve into catastrophic collapse of the instable flank

coarse grained debris flow deposits in the miocene fan deltas se korea a scaling analysis abstract the viscoplastic and inertial grain flow models have been widely used as tools for description and interpretation of ancient debris flow deposits providing a basis to estimate yield strength viscosity cohesion and internal friction angle recent studies suggest however that a debris flow is an intimate mixture of solid and fluid in which a number of momentum transfer mechanisms operate it is therefore necessary to evaluate the relative importance of different momentum transport processes to properly describe a debris flow scaling analysis may be useful to this end using the bagnold number the ratio of inertial grain stress to viscous shear stress savage number the ratio of inertial grain stress to shear stress borne by sustained grain contacts friction number the ratio of frictional shear stress to viscous shear stress and darcy number the ratio of grain fluid interaction stress to inertial grain stress scaling analyses of miocene gravelly debris flow deposits in korea suggest that different types of debris flows can be better distinguished by the analyses providing some implications for debris flow processes

crustal growth in south eastern australia evidence from lower crustal eclogitic and granulitic xenoliths mafic and ultramafic xenoliths in a basaltic cone at the anakies in south eastern australia are geochemically equivalent to continental basaltic magmas and cumulates the xenolith microstructures range from recognizably meta igneous for intrusive rocks to granoblastic for garnet pyroxenites contact relationships between different rock types within some xenoliths suggest a complex petrogenesis of multiple intrusive metamorphic and metasomatic events at the crust mantle boundary during the evolution of south eastern australia unaltered spinel lher zolite typical of the uppermost eastern australian mantle is interleaved with or veined by the metamorphosed intrusive rocks of basaltic composition geothermobarometry calculations by a variety of methods show a concordance of equilibration temperatures ranging from 880 c to 980 c and pressures of 12 to 18 kbar 1200 1800 mpa these physical conditions span the gabbro to granulite to eclogite transition boundaries the water vapour pressure during equilibration is estimated to be about 0 5 of the load pressure using amphibole breakdown data large fluid inclusions of pure co2 are abundant in the mineral phases in the xenoliths and it is suggested that flux of co2 from the mantle has been an important heat source and fluid medium during metamorphism of the mafic and ultramafic protoliths at the lower crust upper mantle boundary the calculated pressures and temperatures suggest that the south eastern australian crust has sustained a high geothermal gradient in addition the nature of the mineral assemblages and the contact relationships of granulitic rock with spinel lherzolite characteristic of mantle material suggest that the moho is not a discrete feature in this region but is represented by a transition zone approximately 20 km thick these inferences are in agreement with geophysical data including seismic heat flow and electrical resistivity data determined for south eastern australia underplating at the crust mantle boundary by continental basaltic magmas may be an important alternative or additional mechanism to the conventional andesite model for crustal accretion

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

the landslides and tsunamis of the 30th of december 2002 in stromboli analysed through numerical simulations on the 30th of december 2002 two tsunamis were generated only 7 min apart in stromboli southern tyrrhenian sea italy they represented the peak of a volcanic crisis that started 2 days before with a large emission of lava flows from a lateral vent that opened some hundreds of meters below the summit craters both tsunamis were produced by landslides that detached from the sciara del fuoco this is a morphological scar and is the result of the last collapse of the northwestern flank of the volcanic edifice that occurred less than 5 ka b p the first tsunami was due to a submarine mass movement that started very close to the coastline and that involved about 20 106 m3 of material the second tsunami was engendered by a subaerial landslide that detached at about 500 m above sea level and that involved a volume estimated at 4 9 106 m3 the latter landslide can be seen as the retrogressive continuation of the first failure the tsunamis were not perceived as distinct events by most people they attacked all the coasts of stromboli within a few minutes and arrived at the neighbouring island of panarea 20 km ssw of stromboli in less than 5 min the tsunamis caused severe damage at stromboli

sector collapses and large landslides on late pleistocene holocene volcanoes in kamchatka russia on kamchatka detailed geologic and geomorphologic mapping of young volcanic terrains and observations on historical eruptions reveal that landslides of various scales from small 0 001 km3 to catastrophic up to 20 30 km3 are widespread moreover these processes are among the most effective and most rapid geomorphic agents of 30 recently active kamchatka volcanoes at least 18 have experienced sector collapses some of them repetitively the largest sector collapses identified so far on kamchatka volcanoes with volumes of 20 30 km3 of resulting debris avalanche deposits occurred at shiveluch and avachinsky volcanoes in the late pleistocene during the last 10 000 yr the most voluminous sector collapses have occurred on extinct kamen 4 6 km3 and active kambalny 5 10 km3 volcanoes the largest number of repetitive debris avalanches 10 during just the holocene has occurred at shiveluch volcano landslides from the volcanoes cut by ring faults of the large collapse calderas were ubiquitous large failures have happened on both mafic and silicic volcanoes mostly related to volcanic activity orientation of collapse craters is controlled by local tectonic stress fields rather than regional fault systems specific features of some debris avalanche deposits are toreva blocks huge almost intact fragments of volcanic edifices involved in the failure some have been erroneously mapped as individual volcanoes one of the largest toreva blocks is mt monastyr a 2 km3 piece of avachinsky somma involved in a major sector collapse 30 40 ka bp long term forecast of sector collapses on kliuchevskoi koriaksky young cone of avachinsky and some other volcanoes highlights the importance of closer studies of their structure and stability

a new correlation of sapphirine granulites in the indo antarctic metamorphic terrain late proterozoic dates from the eastern ghats province of india abstract uranium lead and thorium lead ages were obtained from perrierite and zircons in two samples from the eastern ghats province of south india a sapphirine bearing granulite from anakapalle and a charnockite from visakhapatnam the isotopic data are concordant or close to concordant at 1 ga which is interpreted to be the age of granulite facies metamorphism and charnockite plutonism in the vicinity of anakapalle and visakhapatnam and provides the first report of a late proterozoic granulite facies event in the eastern ghats province in reassemblies of gondwanaland based on dutoit s original proposal the eastern ghats province is juxtaposed against a high grade terrain in east antarctica affected by a granulite facies event and charnockitic plutonic activity 800 1100 ma ago the ages reported here suggest that a portion of the eastern ghats province represents an extension of the late proterozoic terrain from antarctica into india the radiometric results on the anakapalle rocks are the first evidence in south india for sapphirine formation during the late proterozoic other south indian sapphirine localities appear to be archaean in age a review of sapphirine localities in the indo antarctic metamorphic terrain indicates that sapphirine developed under a range of pressure temperature conditions during the archaean and proterozoic evidence for a systematic change in peak metamorphic conditions with time is obscured by these regional variations characterization of the entire pressure temperature path in addition to estimates for the peak conditions is needed to distinguish the archaean and proterozoic metamorphic regimes