shallow magma transport for the 2002 3 mt etna eruption inferred from thermal infrared surveys abstract the 26 october 2002 28 january 2003 eruption of mt etna volcano was characterised by lava effusion and by an uncommon explosivity along a 1 km long eruptive fissure on the southern upper flank of the volcano the intense activity promoted rapid growth of cinder cones and several effusive vents analysis of thermal images recorded throughout the eruption allowed investigation of the distribution of vents along the eruptive fissure and of the nature of explosive activity the spatial and temporal distribution of active vents revealed phases of dike intrusion expansion geometric stabilization and drainage these phases were characterised by different styles of explosive activity with a gradual transition from fire fountaining through transitional phases to mild strombolian activity and ending with non explosive lava effusion here we interpret the mechanisms of the dike emplacement and the eruptive dynamics according to changes in the eruptive style vent morphology and apparent temperature variations at vents detected through thermal imaging this is the first time that dike emplacement and eruptive activity have been tracked using a handheld thermal camera and we believe that its use was crucial to gain a detailed understanding of the eruptive event

the volume of lava erupted during the 2014 to 2015 eruption at holuhraun iceland a comparison between satellite and ground based measurements

birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

an abrupt change in the african monsoon at the end of the younger dryas 1 high resolution studies of variations in the elemental and stable carbon and nitrogen isotope composition of organic matter in cores from lakes malawi tanganyika and bosumtwi tropical africa indicate an abrupt change in the wind driven circulation of these lakes that within the limits of available chronologies was contemporaneous with the end of the younger dryas in the northern hemisphere the change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of africa a range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics africa south of 5 10 s on the other hand initially suffered drought conditions together the evidence suggests an abrupt northward translation of the african monsoon system at circa 11 5 0 25 ka b p the data assembled here contribute to a growing body of work showing that the younger dryas was a major climatic excursion in tropical africa furthermore they add substance to recent suggestions that climatic events in the southern hemisphere may have played a significant role in the abrupt demise of the younger dryas

the mechanism of ascent and emplacement of granite magma during transpression a syntectonic granite paradigm we propose a model for syntectonic ascent and emplacement of granite magma based on structural relations in part of the northern appalachians in the study area in western maine strain was distributed heterogeneously during devonian acadian transpression metasedimentary rocks migmatites at high grades record two contrasting types of finite strain in zones that alternate across strike rocks in both types of zones have a penetrative moderately to steeply ne plunging mineral elongation lineation defined by bladed muscovite fibrolite sillimanite at high grades in straight belts of enhanced deformation rocks have s l fabrics that record apparent flattening to plane strain apparent flattening zones afzs but rocks between these belts have l s fabrics that record apparent constriction apparent constriction zones aczs at metamorphic grades above the contemporary solidus rocks in afzs developed stromatic structure in migmatite which suggests that percolative flow of melt occurred along the evolving flattening fabric stromatic migmatites are intruded by concordant to weakly discordant m scale composite sheet like bodies of granite to suggest magma transport in planar conduits through the afz rocks inhomogeneous migmatite is found in the intervening aczs which suggests migration of partially molten material through these zones en masse probably by melt assisted granular flow inhomogeneous migmatites are intruded by irregular m scale bodies of granite that vary from elongate to sub circular in plan view and seem cylindrical in three dimensions these bodies apparently plunge to the northeast parallel to the regional mineral elongation lineation to suggest magma transport in pipe like conduits through the acz rocks we postulate that the form of magma ascent conduits was deformation controlled and was governed by the contemporaneous strain partitioning magma ascent in planar and pipe like conduits through migmatites is possible because oblique translation during contraction displaces isotherms upward in the orogenic crust to form a thermal antiform within this hot corridor it is the difference in temperature between melt producing reactions in the anatectic zone and the wet solidus for granite melt that enables magma to migrate pervasively up through the orogenic crust without congealing heat advected with the migrating melt promotes amplification of the thermal antiform in a feedback relation that extends the zone of plastic deformation and pervasive melt migration to shallower levels in the crust at the wet solidus we suggest melt flows obliquely toward axial culminations in the thermal antiform which are sites of melt accumulation and perturbations from which magma may escape to form plutons batches of melt that escape from these perturbations may be trapped by tectonic structures higher in the crust or ascent may become inhibited with decreasing depth by thermal arrest and solidification if the rate of arrival of subsequent melt batches exceeds the rate of crystallization at the site of pluton construction melt pressure ultimately may lead to sub horizontal magma fracture or viscous flow of wall rocks may allow lateral spreading the resultant plutons have sub horizontal tabular geometries with floors that slope down to the ascent conduit as the thermal antiform decays the height of sub solidus crust that separates the deepest part of the pluton from the anatectic zone increases consequently pluton inflation declines and solidification leads to infilling of the magma feeder channel to form a root zone that passes downward into migmatite which may explain the difficulty of determining precisely the floor to these deeper segments of large plutons using gravimetry

oblique photogrammetry with visible and thermal images of active lava flows digital images from hand held cameras are increasingly being acquired for scientific purposes particularly where non contact measurement is required however they frequently consist of oblique views with significant camera to object depth variations and occlusions that complicate quantitative analyses here we report the use of oblique photogrammetric techniques to determine ground based thermal camera orientations position and pointing direction and to generate scene information for lava flows at mount etna sicily multiple images from a consumer grade digital slr camera are used to construct a topographic model and reference associated ground based thermal imagery we present data collected during the 2004 2005 eruption and use the derived surface model to apply viewing distance corrections to account for atmospheric attenuation to the thermal images on a pixel by pixel basis for viewing distances of 100 to 400 m the corrections result in systematic changes in emissive power of up to 3 with respect to values calculated assuming a uniform average viewing distance across an image

exogenous and endogenous growth of the unzen lava dome examined by satellite infrared image analysis abstract phase 1 of the most recent eruption of unzen volcano japan occurred between 1991 and 1993 and involved the endogenous and exogenous addition of magma to a growing summit lava dome the temporal variation between endogenous and exogenous styles of dome growth has an important bearing on the hazard posed by dome collapse and explosive events however such data are difficult to acquire and have previously only been obtained in a fully quantitative manner for the mount st helens dome in that case using detailed photogrammetry here we investigate these competing dome growth processes at unzen via analysis of their thermal emission signals present in shortwave infrared swir satellite imagery we find that both the endogenous and exogenous growth styles exhibit identifiable swir signatures whose magnitude can be related to their respective magma supply rates we find that the swir radiant area corresponding to endogenous growth is around four times larger than that corresponding to exogenous growth at the same magma discharge rate analysis of time series imagery indicates that like mount st helens unzen experienced a temporally decreasing magma discharge rate during phase 1 as time progressed and the discharge rate fell the growth style of the unzen dome changed from exogenous only through exogenous decreasing and endogenous increasing to endogenous only thus relative growth rates at the endogenous and exogenous areas of the unzen dome appear to be at least partly controlled by the overall magma discharge rate as with mount st helens the cause of this relationship was most likely the formation and strengthening of a brittle crust at the surface vent which impeded exogenous growth more effectively as time elapsed and the discharge rate fell these results suggest the similarity of the processes operating at the unzen and mount st helens domes though important differences remain in that dome growth was basically continuous at unzen whilst at mount st helens growth episodes were interspersed by significant periods of repose

the geology and structural evolution of a caledonian fold and ductile thrust zone kyle of tongue region sutherland northern scotland the middle to upper proterozoic metasedimentary rocks of the northern highland moine in sutherland are disposed in a series of major caledonian c 470 430 ma metamorphic thrust nappes produced by nw wnw directed shortening and reworking of parts of a pre existing precambrian c 1000 ma orogen lewisian inliers occur throughout sutherland and represent tectonically interleaved units of the original basement gneisses upon which the moine cover sequence was deposited in the western moine nappe of the kyle of tongue region the rocks are deformed by two main episodes d1 and d2 which are thought to represent the effects of precambrian and caledonian orogenesis respectively little basement cover interleaving or large scale folding occurred during the d1 event in the moine nappe but the associated metamorphism to ut leust garnet grade produced peak metamorphic mineral assemblages subsequent caledonian reworking d2 produced a foreland propagating system of wnw directed ductile thrusts and related major f2 sheath folds both of which resulted in much of the observed moine lewisian interleaving metamorphism associated with d2 decreases in grade westwards occurring at similar or slightly lower grades than the earlier d1 event this retrogressive overprint is most obvious at the w margin of the moine nappe the d2 folds and ductile thrusts are geometrically and kinematically similar to the caledonian structures recognized within the moine thrust zone to the west the very low 5 ramp angles suggesting that the thrusts must have very shallow dipping trajectories through the crust f2 fold formation is attributed to an early phase of wnw directed overthrusting compression which was then progressively superseded by a regional ductile extensional strain contemporaneous with continued wnw directed thrusting the occurrence of internal extension in the orogenic wedge during active thrust related foreshortening implies that the shear strength of the material close to the basal detatchment s was continuously reduced i e wedge motion became supercritical in this context strain softening processes within the ductile thrust mylonites were probably of major significance

dating deformation and cooling in the caledonian thrust nappes of north sutherland scotland insights from 40ar 39ar and rb sr chronology 40 ar 39 ar and rb sr mineral ages have been determined from various lithologies exposed in the caledonian foreland and structurally overlying thrust nappes of north sutherland scotland rb sr muscovite ages of c 428 c 421 and c 413 ma obtained from moine thrust zone mylonites are interpreted to date closely regional thrusting during the late silurian to early devonian 40 ar 39 ar muscovite ages within the lower parts of the moine nappe are mostly anomalously old with respect to rb sr analyses of muscovites from the same samples it is likely that this discrepancy results from a component of extraneous or excess argon 40 ar 39 ar hornblende ages and rb sr and 40 ar 39 ar muscovite ages obtained from structurally higher metamorphic units in the caledonian thrust nappes generally range between c 440 ma and c 410 ma these ages are interpreted to date cooling during and following d 2 regional thrusting and folding within internal sectors of the nappe sequence a possible tectonic model involves the silurian collision of baltica with scottish segments of laurentia resulting in the scandian orogeny and broadly coeval moine thrust zone d 2 structures were superimposed on structures and metamorphic fabrics formed during a regional mid ordovician tectonothermal event dated previously at c 470 460 ma syn d 2 temperatures were generally 600 c and sufficient to achieve more or less complete thermal rejuvenation of rb sr and 40 ar 39 ar isotopic systems in muscovite and hornblende even in areas of low d 2 strain

syn orogenic alkaline magmatism and its relationship to the moine thrust zone and the thermal state of the lithosphere in nw scotland the alkaline complexes of nw scotland lie in a zone sub parallel to the moine thrust and represent the nw edge of the otherwise overwhelmingly calc alkaline late orogenic magmatism of the caledonian fold belt the emplacement of intrusives in assynt overlapped the thrust movements and new u pb zircon ages for the loch ailsh intrusion 439 4 ma provide are liable bracket when combined with existing age data for the loch borralan intrusion 430 4 ma for the main movements on the ben more thrust plane a detailed history of the main tectonic and igneous events in the moine thrust zone is tabulated zircons from the undeformed cnoc nan cuilean syenite emplaced in moine rocks near loch loyal give an age of 426 9 ma in contrast to the deformed glen dessary syenite for which earlier work gave 456 5 ma the linear distribution of the alkaline complexes to the west of the calc alkaline plutons and the ultra potassic character of the loch borralan complex the most westerly are consistent with but do not prove generation related to a w dipping subduction zone the persistence of the magmatism over 30 ma in a belt being shortened by thrusting suggests a source in the mantle lithosphere the absence of magmatism further to the nw and the production of calc alkaline magmas to the se of this zone is compatible with a model in which the thermal state of the lithosphere exercises the most important control on the nature of late caledonian magmatism

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

the thermal stealth flows of santiaguito dome guatemala implications for the cooling and emplacement of dacitic block lava flows thick slow moving block lava flows are associated with extrusive activity in dacitic systems where lava core depressurization during flow front collapse generates devas tating block and ash flows dimensional and rare thermal data collected during jan uary 2000 for an active dacitic block flow at santiaguito guatemala provide insight into cooling and emplacement mechanisms flow velocity was low 12 5 m d 21 in spite ginal shear zones the axial part of the flow front was thicker than the marginal zones and was oversteepened this geometry can be explained by a higher vertical velocity gradient in the axial zone causing more frequent and larger volume flow front col lapses axial zone collapses also penetrate farther up flow but not sufficiently to de pressurize the flow core and generate a block and ash flow for such a block and ash flow to occur we calculate that an in crease in velocity and or thickness due to increased slope or topographic confine ment must occur whereas low surface temperatures make block flows invisible to short wave infrared sensors the low veloc ity also contributes to the stealthy behavior of these flows their stealthy nature how ever masks the fact that they can extend many kilometers moving block and ash flow sources closer to vulnerable communities

location of tremor sources and estimation of lava output using tremor source amplitude on the piton de la fournaise volcano 2 estimation of lava output abstract we propose several relations for estimating the amounts of lava emitted during eruptions of the piton de la fournaise volcano based on the use of tremor source amplitude sources for eruption tremor are located in several frequency bands with a location method based on the use of seismic amplitudes corrected for recording site effects sources are usually found at shallow depth and close to the eruptive vents suggesting that tremor is directly generated by the eruptive activity simultaneously with the location of the tremor sources our program gives the source amplitude of the phenomenon we assume a linear or a quadratic relation between the lava output and the tremor source amplitude both relations are calibrated using data for the march 1998 eruption and tested using the volumes emitted during the july and september 1999 and february 2000 eruptions we found that the 5 10 hz frequency band gives lava output much higher than for lower frequencies suggesting that for that band the tremor generation depends on the eruption site in addition to the lava output or that tremor at those frequencies is not directly caused by the outflow of lava but maybe rather by gas the best estimations are obtained using the quadratic relation for frequencies below 5 hz with an agreement better than 15 with the field observations for the july and september 1999 eruptions and 30 for the february 2000 eruption our results show that the cumulative amplitude of tremor recorded during eruptions of the piton de la fournaise is directly related to the amounts of lava erupted

calculation of lava effusion rates from landsat tm data we present a thermal model to calculate the total thermal flux for lava flowing in tubes on the surface or under shallow water once defined we use the total thermal flux to estimate effusion rates for active flows at kilauea hawaii on two dates input parameters were derived from landsat thematic mapper tm field and laboratory measurements using these parameters we obtain effusion rates of 1 76 0 57 and 0 78 0 27 m3 s 1 on 23 july and 11 october 1991 respectively these rates are corroborated by field measurements of 1 36 0 14 and 0 89 0 09 m3 s 1 for the same dates kauahikaua et al 1996 using weather satellite avhrr data of lower spatial resolution we obtain similar effusion rates for an additional 26 dates between the two tm derived measurements we assume that although total effusion rates at the source declined over the period the shut down of the ocean entry meant that effusion rates for the surface flows alone remained stable such synergetic use of remotely sensed data provides measurements that can a contribute to monitoring flow field evolution and b provide reliable numerical data for input into rheological and thermal models we look forward to being able to produce estimates for effusion rates using data from high spatial resolution sensors in the earth observing system eos era such as landsat 7 the hyperspectral imager the advanced spaceborne thermal emission spectrometer and the advanced land imager

progressive deformation structures associated with ductile thrusts in the moine nappe sutherland n scotland in the deeper parts of mountain belts polyphase structural sequences observed at outcrop scale can arise due either to overprinting of regionally distinct deformation phases e g reworking changes in orogenic boundary conditions or to localized controls that bring about transient changes in the patterns of ductile flow these are unlikely to be mutually exclusive processes and examples from scotland demonstrate that once regionally separate events are delimited using radiometric evidence it is possible to isolate complex deformation sequences arising due to local controls in the western moine nappe of sutherland the dominant structures were formed during caledonian ductile thrusting towards the wnw whilst earlier precambrian phases are relatively minor in importance two groups of caledonian folds and fabrics are recognized in many exposures main phase d2 structures which are broadly contemporaneous with ductile thrust fabrics and later secondary phase f3 folds the latter can be divided into two geometric groups sheath fold types which formed initially as wnw overturned buckles subsequently modified by ductile shearing and asymmetric types which are commonly open folds apparently formed with axes close or sub parallel to the thrust transport direction secondary structures show a close spatial association with high strain zones along ductile thrusts and can be shown to have formed during the later stages of thrusting in certain critical exposures i propose that they may form due to strain perturbations resulting from variations in the relative rates of ductile flow within the mylonites where differential shearing occurs due to flow normal perturbations wrench related asymmetric fold types may form in contrast secondary sheath fold structures may result from localized compression phases caused by flow parallel perturbations local flow perturbation models may be appropriate in situations where the distribution of later structures is apparently related to spatial variations in strain intensity and or there is a strong geometric and kinematic similarity between sets of folds and fabrics if such features are not observed a regional polyphase sequence is more likely and it is therefore necessary to obtain radiometric dates or some other independent source of data to demonstrate a time separation

modvolc near real time thermal monitoring of global volcanism modvolc is a non interactive algorithm developed at the hawaii institute of geophysics and planetology higp that uses low spatial resolution 1 km pixel size infrared satellite data acquired by the moderate resolution imaging spectroradiometer modis to map the global distribution of volcanic thermal anomalies in near real time modvolc scans the level 1b modis data stream on a pixel by pixel basis for evidence of pixel and sub pixel sized high temperature radiators once a hot spot has been identified its details location emitted spectral radiance time satellite observation geometry are written to ascii text files and transferred via ftp to higp from where the results are disseminated via the internet http modis higp hawaii edu in this paper we review the underlying principles upon which the algorithm is based before presenting some of the results and data that have been obtained since its inception we show how modvolc reliably detects thermal anomalies at a large number of persistently and sporadically active volcanoes that encompass the full range of common eruptive styles including erebus antarctica colima mexico karymsky kamchatka popocatepetl mexico etna italy and nyiragongo democratic republic of congo amongst others we also present a few cautionary notes regarding the limitations of the algorithm and interpretation of the data it provides

transcurrent shearing granite sheeting and the incremental construction of the tabular 3 1 ga mpuluzi batholith barberton granite greenstone terrane south africa structural petrographic and geochronological studies show that the tabular 3 1 ga mpuluzi batholith in the barberton granite gneiss terrane in south africa was emplaced via a combination of external and internal processes external structural controls are indicated by systematic variations in intrusive relationships and strain along the margins of the mpuluzi batholith and are consistent with an emplacement of the granite in a dilational jog within a ne ene trending system of dextral transcurrent synmagmatic shear zones internally the mpuluzi batholith is essentially made up of granite sheets the structurally higher parts of the granite are made up of shallowly dipping sheets that are underlain by an anastomosing network of steeply dipping variably deformed dykes and sheets these granite sheets at lower structural levels intruded either into the actively deforming shear zones or into extensional sectors between and along the bounding shear zones multiple intrusive relationships and geochronological evidence suggests that granite sheeting and the assembly of the pluton occurred over a period of 3 13 ma the spatial and temporal relationship between deformation and magma emplacement reflects episodes of incremental dilation related to deformation along the bounding shear zones and granite sheeting the transition to the mainly subhorizontal granite sheets at higher structural levels of the tabular mpuluzi batholith indicates the intrusion of the granites during subhorizontal regional shortening where the reorientation of the minimum normal stress to vertical attitudes at the shallow levels of emplacement allowed for vertical dilation and subhorizontal emplacement of the granite sheets

photogrammetric monitoring of lava dome growth during the 2009 eruption of redoubt volcano abstract the 2009 eruption of redoubt volcano alaska began with a phreatic explosion on 15 march followed by a series of at least 19 explosive events and growth and destruction of at least two and likely three lava domes between 22 march and 4 april on 4 april explosive activity gave way to continuous lava effusion within the summit crater we present an analysis of post 4 april lava dome growth using an oblique photogrammetry approach that provides a safe rapid and accurate means of measuring dome growth photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed wing volcanic gas surveys produced a series of digital elevation models dems of the lava dome from 16 april to 23 september the dems were used to calculate estimates of volume and time averaged extrusion rates and to quantify morphological changes during dome growth effusion rates ranged from a maximum of 35 m 3 s 1 during the initial two weeks to a low of 2 2 m 3 s 1 in early summer 2009 the average effusion rate from april to july was 9 5 m 3 s 1 early rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater in mid to late april the volume of the dome had reached 36 10 6 m 3 roughly half of the total volume and dome growth within the summit crater began to be limited by confining crater walls to the south east and west once the dome reached the steep north sloping gorge that breaches the crater growth decreased to the south but the dome continued to inflate and extend northward down the gorge effusion slowed during 16 april 1 may but in early may the rate increased again this rate increase was accompanied by a transition to exogenous dome growth from mid may to july the effusion rate consistently declined the decrease is consistent with observations of reduced seismicity gas emission and thermal anomalies as well as declining rates of geodetic deflation or inflation these trends suggest dome growth ceased by july 2009 the volume of the dome at the end of the 2009 eruption was about 72 10 6 m 3 more than twice the estimated volume of the largest dome extruded during the 1989 1990 eruption in total the 2009 dome extends over 400 m down the glacial gorge on the north end of the crater with a total length of 1 km width of 500 m and an average thickness of 200 m

reos and upb geochronological constraints on the eclogite tonalite connection in the archean man shield west africa abstract mantle derived eclogite xenoliths and tonalite trondhjemite granodiorites ttg that occur in the man shield west africa sample different levels of archean lithosphere chemical and oxygen isotope systematics indicate that low mgo eclogites from the koidu kimberlite are ancient remnants of subducted oceanic crust that may have been involved in regional archean crust formation re os whole rock isotopic data for these eclogites scatter about a line with slope corresponding to an archean age of 3 44 0 76 ga 2 with re os model ages ranging from 1 4 to 3 9 ga this wide range of model ages overlaps with the age range for crust formation and metamorphism in the man shield in situ u pb ages of zircons from crustal rocks have been measured by laser ablation icp ms a tonalitic gneiss has discordant zircons with rare old cores 3 6 ga and an upper concordia intercept at 2890 9 ma 2 zircons from a mafic lower crustal granulite xenolith are concordant at 2686 32 ma our results together with previously published ages for man shield rocks indicate an early archean crust formation event followed by major crustal growth at 2 9 3 0 ga and a last major metamorphic event at 2 7 ga these data show that the eclogites and the continental crust of the west african craton overlap in time of formation but only at the very broad age uncertainty provided by the eclogite re os results they are permissive of archean crustal growth by melting of the protoliths of the materials now sampled as the koidu eclogite xenoliths if so this suggests that archean crustal growth in the man shield occurred in a convergent margin setting

the distribution geometry and kinematic significance of caledonian buckle folds in the western moine nappe northwestern scotland within internal regions of orogenic belts systems of ductile thrusts and folds may form which are geometrically and kinematically analogous to those observed in foreland thrust belts the moine nappe of sutherland northwestern scotland developed during wnw directed caledonian displacements under amphibolite facies conditions broad zones of mylonite associated with the ductile ben hope and moine thrusts both contain numerous small scale folds which can be attributed to transient flow perturbations it is possible to isolate and differentiate generations of such folds basedon their association with particular major thrust zones and or their geometry in regions of lower strain between these thrusts there are a series ofkilometre scale buckle folds the axial traces of which define arcuate trends those with hinges orthogonal to transport are northwestvergent whilst those plunging subparallel to the mineral lineation display variable vergence the spatial distribution of these geometries suggests a causal relationship with displacements on specific underlying thrusts we propose that they reflect larger kilometre scale and possibly longer lived flow perturbations the transport parallel folds are persistent features that often centre on earlier structural culminations and are thought to reflect components of differential shear the most prominent set of regional buckle folds root downwards into the ductile moine thrust and openly refold the structurally overlying ben hope thrust and its associated buckle folds thus supporting a foreland propagating sequence of ductile displacements

near real time satellite monitoring during the 1997 2000 activity of volcan de colima mexico and its relationship with seismic monitoring abstract the 1997 2000 activity of volcan de colima provided a unique opportunity for the joint analysis of satellite and seismic monitoring techniques three stages of volcanic activity were observed pre lava stage stage of lava eruption stage of explosive eruptions advanced very high resolution radiometer satellite data provided observations of both summit thermal anomalies and ash emission daily monitoring of volcan de colima was performed using early morning or late night noaa 12 and 14 satellite passes gathered in real time at our satellite ground receiving station seismic observations were carried out by the red sismica del estado de colima good correlations are observed between seismic activity and parameters monitored by satellite during the three stages five seismic swarms were recorded during the reactivation period four of the seismic swarms coincided with periods of increase in summit temperature and strong ash emissions it is important to note that the ash emissions were observed a few days before the beginning of seismic swarms the thermal saturation at the summit was reached a few hours after the beginning of lava effusion on november 20 1998 and remained at this level until may 1999 even after the lava flow stopped in early february 1999 the lava front was also clearly identified as a source of thermal anomalies and ash plumes study of the summit temperature ash emission relationship allowed us to classify the strong explosions of 1999 2000 the strongest explosion on february 10 1999 produced the largest ash rich plumes that were detected over a wide area 150 km 2 and near saturation temperature anomalies 47 2 48 4 c the main limitation of volcano satellite monitoring occurs during overcast conditions clouds prevented us from monitoring the seismic swarm of july 1998 and the explosion of july 1999 this study shows that satellite monitoring on a near real time basis is a powerful tool not only for research in volcanology but also as an aid for scientific committees to define probable eruption scenarios during volcanic crisis and for civil protection authorities for risk mitigation due to ash emission and sudden heating of the crater without seismicity

where are the eburnian transamazonian collisional belts the reconstruction of early proterozoic crustal evolution and geodynamic environments in africa and south america is incomplete if cratonic areas alone are studied if the presence of high grade

new rb sr age determinations on the archaean basement of eastern sierra leone abstract the archean basement of sierra leone is a typical example of granite greenstone terrains found in ancient continental nucleii reconnaissance field mapping showed that the area can be subdivided into old gneiss which predates the greenstone belts and young granite which is later than the greenstone belts new rb sr whole rock age determinations on two suites of old tonalitic gneiss yield ages of 2786 49 ma and 2770 137 ma which either reflect the time of formation of the original tonalites or their metamorphism three new rb sr whole rock age determination on young granites yield ages of 2786 143 ma 2780 79 ma and 2770 50 ma which are interpreted as the time of emplacement the widespread occurrence of similar young granites throughout the archaean of west africa suggests that these results date a major event in the evolution of this segment of the crust a published pb pb age of the old gneiss and the new ages of the young granite bracket the age of the greenstone belts to 3000 2770 ma however if the rb sr ages of the old gneiss reported in this paper reflect the time of their formation the age of the greenstone belts is tightly bracketed to ca 2770 ma there is no isotopic evidence for rocks substantially older than 3000 ma in the west african archaean

lava effusion rates from hand held thermal infrared imagery an example from the june 2003 effusive activity at stromboli a safe easy and rapid method to calculate lava effusion rates using hand held thermal image data was developed during june 2003 at stromboli volcano italy we used a forward looking infrared radiometer flir to obtain images of the active lava flow field on a daily basis between may 31 and june 16 2003 during this time the flow field geometry and size where flows typically a few hundred meters long were emplaced on a steep slope meant that near vertical images of the whole flow field could be captured in a single image obtained from a helicopter hovering at an altitude of 750 m and 1 km off shore we used these images to adapt a thermally based effusion rate method previously applied to low and high spatial resolution satellite data to allow automated extraction of effusion rates from the hand held thermal infrared imagery a comparison between a thermally derived 0 23 0 87 m3 s 1 and dimensionally derived effusion rate 0 56 m3 s 1 showed that the thermally derived range was centered on the expected value over the measurement period the mean effusion rate was 0 38 0 25 m3 s 1 which is similar to that obtained during the 1985 86 effusive eruption and the time averaged supply rate calculated for normal non effusive strombolian activity a short effusive pulse reaching a peak of 1 2 m3 s 1 was recorded on june 3 2003 one explanation of such a peak would be an increase in driving pressure due to an increase in the height of the magma contained in the central column we estimate that this pulse would require the magma column to attain a height of 190 m above the effusive vent which is approximately the elevation difference between the vent and the floor of the ne crater our approach gives an easy to apply method that has the potential to provide effusion rate time series with a high temporal resolution

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

late brittle deformation in a caledonian ductile thrust wedge new evidence for gravitational collapse in the moine thrust sheet sutherland scotland abstract in the ductile regions of orogenic wedges late brittle structures formed at shallow crustal depths have received little attention however they are important as they of ten record the final stages in deformational history during uplift and erosion of the orogen in the moine rocks of sutherland late caledonian brittle folds and low angle faults post date ductile structures formed during wnw nw directed thrust movements earlier in the same orogenic event in the western moine nappe the late structures display geometries which indicate that they formed during regionally ese directed extensional movements down the dip of the pre existing regional foliation these late structures are correlated with similar wnw directed extensional low angle faults recognised in the moine thrust zone south of the assynt culmination both are thought to have formed in response to late caledonian gravity induced thinning of the moine thrust wedge and both pre date devonian extension associated with the formation of the west orkney basin along strike changes in the location and sense of extensional movements north and south of the assynt culmination are explained by changes in the pre existing structural geometry of the caledonian ductile thrust nappes within the moine hence earlier deformation patterns are thought to exert important controls over later events in an evolving orogenic wedge

gas driven lava lake fluctuations at erta ale volcano ethiopia revealed by modis measurements the long lived lava lake of erta ale volcano ethiopia is remotely monitored by moderate resolution imaging spectroradiometers modis installed on satellites the normalised thermal index nti wright et al remote sens environ 82 135 155 2002 is shown to be proportional to the volume of the lava lake based on visual observations the lava lake s variable level can be plausibly related to a stable foam i e a mixture composed of densely packed non coalescing bubbles in suspension within a liquid this foam is trapped at the top of the magma reservoir and its thickness changes in response to the gas flux feeding the foam being successively turned on and off the temporal evolution of the foam thickness and the resulting variation of the volume of the lava lake is calculated numerically by assuming that the gas flux feeding the foam initially constant and homogeneous since december 9 2002 is suddenly stopped on december 13 2002 and not restarted before may 2003 the best fit between the theoretical foam thickness and the level of the lava lake deduced from the nti provides an estimate of both the reservoir radius 155 170 m and the gas flux feeding the foam 5 5 10 3 7 2 10 3 m 3 s 1 when existing this is in agreement with previous estimates from acoustic measurements bouche et al earth planet sci lett 295 37 48 2010 the very good agreement between the theoretical foam thickness and that deduced from modis data shows for the first time the existence of a regime based on the behaviour of a stable foam whose spreading towards the conduit wide conduit condition can explain the long lived activity our predictive model which links the gas flux at the vent to the foam spreading could potentially be used on any volcano with a long lived activity the underlying gas flux and the horizontal surface area of the magma reservoir can then be deduced by combining modelling to continuous measurements of gas flux the lava lake when high often shows regular rise and fall of its level we have recognised a minimum of 26 very well marked cycles between january 2001 and december 13 2002 corresponding to a typical return time of 10 8 2 3 days and a gas volume of 8 3 105 2 0 105 m 3 this corresponds to a gas volume fraction in the reservoir equal to 0 023 0 063 the yearly gas flux estimated between december 13 2002 and september 27 2004 varies between 2 3 10 6 and 5 9 10 6 m 3 s 1 at the depth of the reservoir the long time series provided by infra red sensors mounted on satellites could be used on any persistent volcano to detect potential periodic variations in the level of lava lakes or lava columns providing that the vent has a funnel shape as often and is sufficiently large

effusion rate trends at etna and krafla and their implications for eruptive mechanisms abstract using effusion rates obtained from ground and satellite based data we build a data set of 381 effusion rate measurements during effusive activity at etna and krafla between 1980 and 1999 this allows us to construct detailed effusion rate curves for six fissure fed eruptions at etna and krafla and four summit fed eruptions at etna these define two trends type i and ii type i trends have effusion rates that rise rapidly to an initial peak before declining more slowly resulting in an exponential decrease in eruption rate and declining growth in cumulative volume type ii trends are characterised by steady effusion and eruption rates and hence a linear increase in cumulative volume the former is typical of fissure eruptions and can be explained by tapping of an enclosed pressurised system the latter are typical of persistent etnean summit eruptions plus one persistent effusive eruption at stromboli 1985 1986 examined here and can be explained by overflow of the time averaged magma supply we use our effusion rate data to assess the magma balance at etna 1980 1995 and krafla 1975 1984 between 1980 and 1995 etna was supplied at a time averaged rate of 6 8 2 3 m 3 s 1 of which 13 was erupted at krafla 817 30 10 6 m 3 was erupted and intruded during 1975 1984 and the ratio of erupted to intruded volume was 0 3 at etna there is evidence for intrusion of the unerupted magma within and beneath the edifice as well as storage in the central magma column at krafla unerupted magma was intruded into a rift zone but an increasing proportion of the supply was erupted from 1980 onwards a result of the rift zone capacity being reached magma intruded prior to an eruptive event may also be entrained and or pushed out during eruption to contribute to the initial high effusion rate phases of type i events the detail in our effusion rate curves was only possible using a thermal approach which estimates effusion rates using satellite data we look forward to analysing satellite derived effusion rate trends in real time using data from current and soon to be launched sensors

a 3 5 ga granite gneiss basement in guinea further evidence for early archean accretion within the west african craton abstract a granite gneiss formation guelemata orthogneiss was mapped on the northern and western slopes of the mount nimba hill range in guinea the original rocks were high al low yb medium to high k granites similar to most archean ttg analyses of u and pb isotopes in zircons using an ion microprobe shrimp gave ages of 3542 and 3535 ma respectively for the granite gneiss and a neighbouring granulitic metagabbro these are the oldest ages so far reported from the archean kenema man domain of west africa partial melting of an unfractionated basalt under eclogite facies conditions appears to be a suitable model for the origin of the granite gneiss

first recorded eruption of mount belinda volcano montagu island south sandwich islands the modvolc satellite monitoring system has revealed the first recorded eruption of mount belinda volcano on montagu island in the remote south sandwich islands here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption including modis landsat 7 etm aster and radarsat 1 data modvolc thermal alerts indicate that the eruption started sometime between 12 september and 20 october 2001 with low intensity subaerial explosive activity from the island s summit peak mount belinda by january 2002 a small lava flow had been emplaced near the summit and activity subsequently increased to some of the highest observed levels in august 2002 observations from passing ships in february and march 2003 provided the first visual confirmation of the eruption aster images obtained in august 2003 show that the eruption at mount belinda entered a new phase around this time with fresh lava effusion into the surrounding icefield modis radiance trends also suggest that the overall activity level increased significantly after july 2003 thermal anomalies continued to be observed in modis imagery in early 2004 indicating a prolonged low intensity eruption and the likely establishment of a persistent summit lava lake similar to that observed on neighboring saunders island in 2001 our new observations also indicate that lava lake activity continues on saunders island

subduction related shoshonitic and ultrapotassic magmatism a study of siluro ordovician syenites from the scottish caledonides syenites are important or predominant components of several plutonic complexes emplaced between 456 and 415 ma along the nw margin of the caledonian orogenic belt adjacent to the lewisian foreland in w and nw scotland although there are in detail chemical differences between the syenites from each centre they form a well defined compositional group overall ratios amongst their trace elements especially very high values of la nb are quite different from those trachytes and syenites formed by fractional crystallisation of ocean island basalts and their continental equivalents emplaced in regions of anorogenic crustal tension instead the scottish caledonian syenites closely resemble chemically the fractional crystallisation residua of potassic subduction related magmas such as the shoshonitic series a comendite minor intrusion from a swarm associated with the loch borralan and loch ailsh syenitic complexes is remarkably similar in composition to recent obsidian from the shoshonitic volcano of lipari in the aeolian arc published sr and pb isotopic ratios preclude a significant component of either upper proterozoic moine schists or lower crust granulite facies archaean lewisian or proterozoic grenvillian gneisses in all these syenites except in local syenitic facies of the glenelg ratagain complex fractional crystallisation appears to be the mechanism by which the liquids which formed these syenites evolved from basic parental magmas the phases involved in this process may have included plagioclase alkali feldspar pyroxene amphibole biotite garnet fe ti oxide sphene allanite apatite zircon and zirconolite and therefore all the ratios amongst even the so called incompatible elements may have changed during the evolution of the leucocratic magmas nevertheless a detailed study of the glen dessarry complex shows that the changes are insufficient to disguise the geochemical nature of the parental magmas these appear to be picritic shoshonite mgo 15 ni 400ppm la yb 20 la nb 5 for the glen dessarry loch borralan and loch ailsh syenites and picritic ultrapotassic magmas mgo 15 ni 400 ppm la yb 60 la nb 7 such as would crystallise to minettes for the loch loyal and glenelg ratagain syenites mafic shoshonites were erupted amongst the 410 ma lome lavas of this region and also occur as widespread approximately contemporaneous volcanic feeder plugs minettes of similar age are also common as dykes in nw scotland numerous large tonalite granite complexes with minor diorites and gabbros were emplaced in w and nw scotland between 435 and 400 ma these are generally acknowledged to be mixtures of magmas from crustal and mantle sources their more mafic members show compositional features such as very high ba and sr which group them with the rare syenites and the lorne lavas of the same region into a distinctive geochemical province within which shoshonitic and allied magmas were the mantle derived component two models are presented to account for the generation of strongly potassic subduction related magmas several hundred km behind a nw directed subduction zone or during the period immediately following continental collision

transport parallel cross folds within a mid crustal caledonian thrust stack northern scotland abstract cross folds are typically associated with zones of anomalous foliation trend that lie at high angles to orogenic strike this case study concentrates on a region of transport parallel cross folding developed by buckling during caledonian ductile thrusting within the moine and naver nappes of northern scotland detailed structural analysis reveals a systematic angular relationship between the trend of tectonic transport fold axes and the vergence of minor folds large scale cross folding is considered here to be related to wrench dominated differential shearing during thrust sense displacements along an important possibly out of sequence structure here termed the ben blandy shear zone this suggests that patterns of folding within the internal parts of the caledonian orogen in scotland are principally controlled by the kinematic constraints imposed by low angle thrusting thus early main phase folding is associated with the initiation and propagation of ductile thrusts whilst later secondary structures including cross folds can be related to the development of flow perturbations during displacement along well established regionally important detachments

high resolution satellite and airborne thermal infrared imaging of precursory unrest and 2009 eruption at redoubt volcano alaska abstract a combination of satellite and airborne high resolution visible and thermal infrared tir image data detected and measured changes at redoubt volcano during the 2008 2009 unrest and eruption the tir sensors detected persistent elevated temperatures at summit ice melt holes as seismicity and gas emissions increased in late 2008 to march 2009 a phreatic explosion on 15 march was followed by more than 19 magmatic explosive events from 23 march to 4 april that produced high altitude ash clouds and large lahars two or three lava domes extruded and were destroyed between 23 march and 4 april after 4 april the eruption extruded a large lava dome that continued to grow until at least early july 2009

deformation structures associated with the trachyte mesa intrusion henry mountains utah implications for sill and laccolith emplacement mechanisms abstract deformation structures in the wall rocks of igneous intrusions emplaced at shallow crustal depths preserve an important record of how space was created for magma in the host rocks trachyte mesa a small oligocene age intrusion in the henry mountains utah is composed of a series of stacked tabular sheet like intrusions emplaced at 3 3 5 km depth into sandstone dominated sedimentary sequences of late palaeozoic mesozoic age new structural analysis of the spatial distribution geometry kinematics and relative timings of deformation structures in the host rocks of the intrusion has enabled the recognition of distinct pre syn and late stage emplacement deformation phases our observations suggest a two stage growth mechanism for individual sheets where radial growth of a thin sheet was followed by vertical inflation dip slip faults formed during vertical inflation they are restricted to the tips of individual sheets due to strain localisation with magma preferentially exploiting these faults initiating sill sheet climbing the order in which sheets are stacked impacts on the intrusion geometry and associated deformation of wall rocks our results offer new insights into the incremental intrusion geometries of shallow level magmatic bodies and the potential impact of their emplacement on surrounding host rocks

deformation of granitic rocks across the brittle ductile transition abstract a microstructural analysis has been carried out on mylonites and mylonitic gneisses of the eastern peninsular ranges mylonite zone which were formed over a range of metamorphic conditions from lower greenschist to amphibolite facies composite planar fabrics in the form of c and s planes are found at all metamorphic grades fractured feldspars kinked biotites and ductile deformation of quartz characterize the lower greenschist facies mylonites at mid upper greenschist grade orthoclase grains show dynamic recrystallization textures whereas plagioclase exhibits low temperature plasticity with only minor recovery biotite ribbons form by progressive rotation and coalescence of kink band segments to produce chevron fold patterns at epidote amphibolite grade and above recovery processes and annealing recrystallization predominate in all minerals residual orthoclase porphyroclasts show strain related myrmekite formation along those sides of the grains that face the instantaneous shortening direction myrmekite formation due to replacement reactions cannot explain this geometry it is proposed that the myrmekites formed due to a combination of exsolution replacement and strain enhanced diffusion

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

granite magma generation ascent and emplacement within a transpressional orogen crustal thickening during transpressive orogenesis may produce anatectic granites which may then localize deformation leading to transcurrent movement granites may be transported from sites of generation through the mid crust in dyke like channelways within relatively narrow strike slip shear zones which link to major fault zones in the upper crust extensional jogs within fault systems provide developing sites for the assembly of plutons from magma arriving from below the model is based upon observations from the cadomian belt of nw france which exposes sections through middle and upper levels of the late precambrian crust within different elements of the orogen the mechanism provides a favourable alternative to diapirism and explains the common collocation of granites and shear zone fault systems within orogenic belts

significance of low symmetry fabrics in magmatic rocks abstract the significance of low symmetry fabrics monoclinic and triclinic in magmatic rocks is studied using theoretical models describing the motion of rigid markers embedded in a slowly deforming ductile matrix in agreement with curie s symmetry principle the development of these fabrics requires a non coaxial strain path simulations of monoclinic fabrics indicate that their characteristics depend on a the strain regime and the amount of strain and b the morphological composition of the population of rigid markers natural monoclinic fabrics contain precious information about the strain regime they result from type of the non coaxial strain path involved simple shear non coaxial flattening etc orientation of its axes and sense of shear the magnitude of the finite strain may eventually be estimated provided that the shape of the markers is precisely known

temporal trends in lava dome extrusion at santiaguito 1922 2000 we present a means of extracting lava dome extrusion rates from data provided by the thematic mapper and enhanced thematic mapper plus instruments flown on the landsat satellites extrusion rates derived from the landsat data for santiaguito dome complex guatemala during november 1987 and january 2000 of 0 72 0 08 and 0 48 0 09 m3 s 1 compare favorably with ground based estimates of 0 63 0 28 and 0 48 0 17 m3 s 1 a satellite data derived set of 18 extrusion rate estimates between 1987 and 2000 along with ground based volume estimates prior to 1987 allow us to infer volumes of magma erupted since 1922 these data reveal cyclic extrusion at santiaguito each cycle begins with a 3 6 year long phase of high extrusion rate 0 5 2 1 m3 s 1 followed by a longer 3 11 years phase of low extrusion rate 0 2 m3 s 1 the 8th cycle began in 1996 and was still in its high extrusion rate phase during january 2000 with time however the durations of the low extrusion rate phases have increased peak extrusion and time averaged extrusion rates for each cycle have decreased and the difference between extrusion rates during the high and low extrusion rate phases of each cycle has decreased these trends may be the result of depressurization and exhaustion of the source in this case the current eruption may be expected to end around 2020 alternatively santiaguito may be entering a period of persistent activity maintained by a stable magma supply in this case we may expect extrusion to become less cyclic and to stabilize at 0 2 0 4 m3 s 1 however a 2 wt decrease in sio2 content of erupted products since 1970 appears to be consistent with chamber exhaustion as well as an increase in block lava flow lengths during 1970 2000

significance of a hiatus in down temperature fabric development within syn tectonic quartz diorite complexes channel islands uk detailed fabric development histories have been deduced for neoproterozoic foliated quartz diorite complexes of the channel islands uk the plutons were emplaced during regional d2 deformation magmatic fabrics formed at low crystal contents pre rheologically critical melt percent are only locally preserved due to overprinting by solid state deformation which occurred at moderate temperatures 400 550 c this is demonstrated by brittle microcracking of plagioclase and amphibole with only local ductile bending and dynamic recrystallization marginal recrystallization and myrmekite development on alkali feldspar ductile deformation of quartz to form types 2 3 ribbons quartz recrystallization by sub grain rotation associated with a slip but not c slip biotite recrystallization within micro shears and variable amphibole recrystallization the deformation histories display a distinct division between magmatic state and moderate temperature solid state deformation features with little evidence for intervening high temperature solid state fabrics this contrasts with criteria widely considered diagnostic of syn tectonic plutons which envisage development of a continuum of magmatic through high temperature solid state deformation fabrics however we consider the plutons syn tectonic and attribute the hiatus to contrasting strain and pluton cooling rates length and nature of deformation events and host rock ambient temperatures intermediate magmas emplaced at moderate to shallow levels in the crust may be more prone to develop such apparently punctuated deformation histories than sio 2 richer granitoids

ducks low cost thermal monitoring units for near vent deployment abstract during 1999 we designed and tested a thermal monitoring system to provide a cheap robust modular real time system capable of surviving the hostile conditions encountered proximal to active volcanic vents in november 2000 the first system was deployed at pu u o o kilauea hawai i to target persistently active vents aside from some minor problems such as sensor damage due to tampering this system remained operational until january 2004 the success of the prototype system led us to use the blueprint for a second installation at stromboli aeolian islands italy this was deployed dug into a bomb proof bunker during may 2002 and survived the april 2003 paroxysmal eruption despite being located just 250 m from the vent in both cases careful waterproofing of connectors and selection of suitable protection has prevented water damage and corrosion in the harsh atmosphere encountered at the crater rim the pu u o o system cost us 10 000 and comprises four modules sensors transmission and power hub repeater station and reception site the sensor component consists of three thermal infrared thermometers housed in pelican cases fitted with germanium arsenide selenium windows two 1 field of view fov sensors allow specific vents to be targeted and a 60 fov sensor provides a crater floor overview a hard wire connection links to a pelican case housed microprocessor modem and power module from here data are transmitted via a repeater site to a dedicated pc at the hawaiian volcano observatory here data are displayed with a delay of 3 s between acquisition and display the modular design allows for great flexibility at stromboli 1 and 15 fov sensor modules can be switched depending changes in activity style and crater geometry in addition a direct line of site to the stromboli reception center negates the repeater site requirement reducing the cost to us 5500 for a single sensor system we have also constructed self contained units with internal data loggers for us 1500 unit these have been tested at kilauea stromboli etna masaya santiaguito fuego pacaya poas soufriere hills villarrica and erta ale these instruments have proved capable of detecting thermal signals associated with 1 gas emission 2 gas jetting events 3 crater floor collapse 4 lava effusion 5 lava flow in tubes 6 lava lake activity 7 lava dome activity and 8 crater lake skin temperature

the changing morphology of an open lava channel on mt etna an open channel lava flow on mt etna sicily was observed during may 30 31 2001 data collected using a forward looking infrared flir thermal camera and a minolta land cyclops 300 thermal infrared thermometer showed that the bulk volume flux of lava flowing in the channel varied greatly over time cyclic changes in the channel s volumetric flow rate occurred over several hours with cycle durations of 113 190 min and discharges peaking at 0 7 m3 s 1 and waning to 0 1 m3 s 1 each cycle was characterized by a relatively short high volume flux phase during which a pulse of lava with a well defined flow front would propagate down channel followed by a period of waning flow during which volume flux lowered pulses involved lava moving at relatively high velocities up to 0 29 m s 1 and were related to some change in the flow conditions occurring up channel possibly at the vent they implied either a change in the dense rock effusion rate at the source vent and or cyclic variation in the vesicle content of the lava changing its bulk volume flux pulses would generally overspill the channel to emplace p hoehoe overflows during periods of waning flow velocities fell to 0 05 m s 1 blockages forming during such phases caused lava to back up occasionally backup resulted in overflows of slow moving a that would advance a few tens of meters down the levee flank compound levees were thus a symptom of unsteady flow where overflow levees were emplaced as relatively fast moving p hoehoe sheets during pulses and as slow moving a units during backup small localized fluctuations in channel volume flux also occurred on timescales of minutes volumes of lava backed up behind blockages that formed at constrictions in the channel blockage collapse and or enhanced flow under around the blockage would then feed short lived wave like down channel surges real fluctuations in channel volume flux due to pulses and surges can lead to significant errors in effusion rate calculations

space based estimate of the volcanic heat flux into the atmosphere during 2001 and 2002 satellite remote sensing offers a convenient way to monitor changes in the thermal budgets of earth s subaerially active volcanoes by using data acquired by the national aeronautics and space administration s moderate resolution imaging spectro radiometer we have calculated the amount of heat released into the atmosphere by 45 volcanoes active during 2001 and 2002 in order to quantify the contribution active volcanism makes to earth s energy budget we report that the amount of heat radiated into the troposphere by these volcanoes as detected from space was 5 34 3 10 16 and 5 30 3 10 16 j yr during 2001 and 2002 respectively this energy flux is three orders of magnitude less than the amount of energy consumed by the united states of america for residential manufacturing and transportation purposes during 1999

the stereographic analysis of facing abstract facing directions represent an accurate means by which tectonic structure and sedimentary way up may be related a simple method is presented for determining facing directions accurately using a stereonet once determined larger amounts of facing data can be quickly collated and analysed using similar techniques to those employed for other lineations an example is given for some sheath fold structures in the moine rocks of sutherland n scotland

archaean crustal evolution in west africa a new synthesis of the archaean geology in sierra leone liberia guinea and ivory coast abstract a new synthesis of the geology and geochronology of the little known archaean rocks in sierra leone liberia guinea and ivory coast is presented in order to better understand the processes of archaean crustal evolution in this region and to attempt to interpret these data in the light of our current understanding of archaean crustal evolution in addition this study seeks to identify those aspects of archaean crustal evolution which are currently not known in this area and which need to become the subject of future studies given the economic importance of this region in terms of the mineral deposits hosted in the archaean rocks these include greenstone belt hosted iron ore lode gold chromite and columbite tantalite and younger diamondiferous kimberlites intrusive into archaean felsic gneisses the new results show that this cratonic nucleus comprises of four main geological units 1 the oldest crust is made up of 3 5 3 6 ga ttg tonalite trondhjemite granodiorite gneisses these only outcrop in the east of the craton in guinea but their presence is indicated elsewhere in the central part of the craton though xenocrystic zircon cores in younger rocks 2 the major rock type found throughout the craton is 3 26 2 85 ga ttg gneiss in detail these magmas are thought to have formed in two episodes one between 3 05 3 26 ga and the other between 2 85 2 96 ga the presence of inherited zircons in the younger suite indicate that this event represents the partial reworking of the older gneisses 3 4 ga eclogite xenoliths in kimberlite derived from the sub continental lithospheric mantle are thought to be the restite after the partial melting of a basaltic protolith in the production of the ttg magmas 3 supracrustal rocks form linear belts infolded into the ttg gneisses and metamorphosed to amphibolite and granulite grade they are of different sizes contain a variety of lithological sequences and may be of several different ages the larger supracrustal belts in sierra leone contain a thick basalt komatiite sequence derived by the partial melting of two different mantle sources unconformably overlain by a sedimentary formation they are seen as an important resource for gold iron ore chromite and columbite tantalite 4 a suite of late archaean granitoids formed by the partial melting of the ttg gneisses in a craton wide deformation metamorphic partial melting event at 2800 20 ma this thermal event is thought to be responsible for the stabilisation of the craton this new synthesis highlights major geological and geochronological similarities between the archaean rocks of sierra leone liberia guinea and ivory coast and those in the reguibat shield in the northern part of the west african craton suggesting that the two regions were once more closely related

thermal mapping of a pāhoehoe lava flow kīlauea volcano abstract p hoehoe lava flows are a major component of hawaiian eruptive activity and an important part of basaltic volcanism worldwide in recent years p hoehoe lava has destroyed homes and threatened parts of hawai i with inundation and disruption in this study we use oblique helicopter borne thermal images to create high spatial resolution 1 m georeferenced thermal maps of the active p hoehoe flow on k lauea volcano s east rift zone thermal maps were created on 27 days during 2014 2016 in the course of operational monitoring encompassing a phase of activity that threatened the town of p hoa our results illustrate and reinforce how p hoehoe flows are multicomponent systems consisting of the vent master tube distributary tubes and surface breakouts the thermal maps accurately depict the distribution and character of p hoehoe breakouts through time and also delineate the subsurface lava tube surface breakouts were distributed widely across the p hoehoe flow with significant portions concurrently active well upslope of the flow front often concentrated in clusters of activity that evolved through time gradual changes to surface breakout distribution and migration relate to intrinsic processes in the flow including the slow evolution of the distributary tube system abrupt disruptions to this system and the creation of new breakouts and associated hazards were triggered by extrinsic forcing namely fluctuations in lava supply rate at the vent which disrupted the master lava tube although the total area of a p hoehoe flow has been suggested to relate to effusion rate our results show that changes in the proportion of expansion vs overplating can complicate this relationship by modifying existing techniques we estimate time averaged discharge rates for the flow during 2014 2016 generally in the range of 1 2 m 3 s 1 mean 1 3 0 4 m 3 s 1 less than half of k lauea s typical eruption rate on the east rift zone and suggestive of a weak eruptive regime during 2014 2016 we caution however that this discharge rate approach requires further independent corroboration the thermal maps provide the first synoptic characterization of p hoehoe flow activity at high spatial resolution essential both for operational hazard assessment and fundamental understanding of p hoehoe behavior

factors affecting the accuracy of thermal imaging cameras in volcanology volcano observatories and researchers are recognizing the potential usefulness of thermal imaging cameras both before and during volcanic eruptions obvious applications include measurements of the surface temperatures of active lava domes and lava flows to determine the location of the most active parts of these potentially hazardous features if appropriate precautions are taken the new generation of thermal imaging cameras can be used to extract quantitative as well as qualitative information on volcanic activity for example they can be used to measure the temperature of lava on eruption and to reveal how the crust cools during flow emplacement this is important for the validation of lava flow models to ensure that meaningful temperatures are collected thermal imaging data must be corrected for instrumental errors emissivity of the surface being imaged atmospheric attenuation viewing angle and surface roughness controlled laboratory experiments have been undertaken to determine the emissivity of smooth and rough samples and the effects of viewing angle and to quantify the errors measured emissivities range from 0 973 0 002 for smooth samples of basalt and 0 984 0 004 for rough samples errors in emissivity corrected temperatures are within 15 c for lava at 1100 c variations from individual sensor receptors which provide individual pixel temperature data were found to be 0 6 and instrumental errors of the cameras used were 0 1 apparent temperatures were found to vary by less than the instrumental error for viewing angles up to 30 degrees from normal to lava and thereafter increased by 1 c per degree by increasing the apparent viewing distance of a small vent on mount etna from 1 5 to 30 m the maximum temperature is shown to decrease by 53 c due to integrated averaging of radiance over increased pixel areas at a viewing distance of 250 m the maximum temperature decreased by 200 c with a further 75 c decrease due to atmospheric attenuation for a relative humidity of 50 however errors in relative humidity measurements can lead to atmospheric attenuation correction inaccuracies up to 200 c at viewing distances of 1 km we show how temperatures measured using thermal imaging cameras can be corrected to give improved estimates of temperature distributions on the surface of active lava flows

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

satellite derived surface temperature and in situ measurement at solfatara of pozzuoli naples italy ground thermal anomalies in volcanic hydrothermal systems where the outflow of hot fluids gives rise to fumarolic fields soil degassing and hot soils have up to now rarely been investigated by using satellite here we report a comparison between surface temperature derived by satellite data and a large data set of measured soil temperatures and co2 fluxes for a volcanic hydrothermal system the solfatara of pozzuoli campi flegrei italy surface temperatures derived from aster advanced spaceborne thermal emission and reflection radiometer data are compared with soil temperatures and co2 fluxes from four surveys performed in 2003 2010 and in 2014 the good match between the spatial distributions of computed and measured temperatures suggests the adequacy of satellite data to describe the solfatara thermal anomaly while the correspondence between temperatures and co2 fluxes evidences the link between degassing and heating processes the aster derived surface temperatures 14 37 c are coherent with those measured in the soil 10 97 c at 10 cm depth considering the effect of the thermal gradients which characterize the degassing area of solfatara this study shows that satellite data can be a very powerful tool with which to study surface thermal anomalies and can provide a supplementary tool to monitor thermal evolution of restless volcanoes

p t conditions in coeval greenstone belts and granulites from the archaean of sierra leone supracrustal rocks in the archaean of sierra leone can be divided into two distinct geographical provinces which are characterised by high and low grades of metamorphism in the west of the craton greenstone belts up to 130 km long with thick successions of mafic lavas and clastic sediments are metamorphosed to amphibolite facies in the east of the craton there are smaller schist relics metamorphosed to granulite facies the dominant lithologies are banded iron formation and mafic granulites mineral equilibria indicate that the metamorphic climax in the greenstone beltswas 595 50 c 5 5 0 5 kbar nimini hills 565 50 c 4 9 2 5 kbar gori hills and in the granulites was 770 50 c 7 5 1 5 kbar the difference in p t conditions for the metamorphic maximum in the greenstone belt and granulites can be explained by four possible models for crustal thickening and subsequent uplift and erosion it is possible that the crustwas thickened by tectonic processes so that the greenstone belts and granulites formed part of the same vertical pile in this case the difference in recorded p t conditions results from variable erosion rates or from a variably thickened crust on the other hand the crust may have been thickened by the addition of magmas and similarly the recorded difference in p t conditions results from variable erosion rates or non uniform thickening geological evidence favours although does not prove a magmatic model for crustal thickening the recorded p t conditions reflect a difference in erosion level between the greenstone belts and granulites but it is not possible to show whether this is the product of variable erosion rates or a variably thickened crust

separating the thermal fingerprints of lava flows and simultaneous lava fountaining using ground based thermal camera and seviri measurements uring effusive eruptions thermal satellite monitoring has proved well suited to map thethermal flux from lava flows however during lava fountaining events thermal contributions from active flows and from the fountain itself cannot be separated in low resolution satellite data here using photogrammetry and atmospheric modeling techniques we compare radiance estimates from long range ground based thermal camera data from which the fountain can be excluded with those from seviri satellite images for a fountaining event at mount etna 12 august 2011 the radiant heat flux determined from the ground based camera showed similar behavior to values retrieved from spinning enhanced visible and infrared imager seviri thus the seviri signal is interpreted to be dominated by the lava flows with minimal contribution from the fountain furthermore by modeling the cooling phase of each pixel inundated by lava the mean thickness and lava volume 2 4 10 6 m3 derived from camera images are comparable with those calculated from seviri 2 8 10 6 m3

the paleoproterozoic djebel drissa ring complex eglab shield algeria post collisional intrusions in a transtentional tectonic setting abstract the eburnean a type granitic djebel drissa ring complex is part of the 2 08 ga post collisional aftout magmatic suites that intruded the 2 22 2 09 ga old paleoproterozoic granitoids in the eglab shield in west african craton it is composed of unfoliated granitoids arranged in near concentric zones the zoning is interpreted as resulting from multiple intrusions of continuous magmatic pulses leading to in situ growth of the complex new field observations anisotropy of magnetic susceptibility ams gravimetry and aeromagnetic data suggest that the regional deformation controlled the emplacement of this complex the sub circular form of the granitic body and the ams pattern are consistent with a transtensional tectonic setting along a nw se major shear zone and with an emplacement also related to an associated wnw ese extension fault this well dated regional deformation corresponds to the last main structural event of the paleoproterozoic evolution of the eglab shield

the influence of country rock structural architecture during pluton emplacement the loch loyal syenites scotland the late caledonian loch loyal syenites comprise three related but geographically separate composite intrusions the ben loyal ben stumanadh and cnoc nan cuilean bodies they were emplaced c 426 ma into moine and lewisian rocks of the moine and naver thrust sheets previously deformed by caledonian nw directed folding and thrusting at amphibolite facies metamorphic conditions the intrusions lie mainly within a zone of large scale cross folds in which the regional foliation trends nw se at high angles to regional orogenic strike nne ssw the cross folds are underlain by a broad ese dipping zone of high strain known as the ben blandy shear zone the nw basal contact of the ben loyal body dips generally se and strikes sub parallel to the foliation in the underlying ben blandy shear zone the higher parts of this syenite together with those of the ben stumanadh and cnoc nan cuilean intrusions form a series of variably coalesced dykes trending nw se sub parallel to the foliation in the pre existing zone of cross folds there is little evidence for significant country rock deformation during emplacement of the syenites minor components of top to the se extension occurred along the nw boundary of the ben loyal body whilst minor dextral shearing is associated with the emplacement of the nw se vertical sheet like units that are thought to form the se part of this intrusion and the other loch loyal syenites generally contact parallel magma tic state deformation fabrics are dominant in most of the intrusions and are thought to reflect limited magma pressure driven internal deformation of the igneous bodies during and immediately after emplacement the geometry of these fabrics and the loch loyal syenites as a whole has been directly controlled by the pre existing structural architecture of the surrounding country rocks this appears to be a previously overlooked feature of many plutons emplaced at mid to upper crustal depths below the region influenced by the free surface the siting and emplacement of the loch loyal syenites may have been initially facilitated by late caledonian gravity driven extension of the moine thrust sheets following the initial phase of intrusion it is also possible that the presence of magma actually promoted further nappe collapse in the adjacent country rocks there is no compelling reason to link the upper crustal extension observed during emplacement to the genesis of the alkaline magmas in the underlying mantle the siting and ascent of the syenites at depth may be linked to the presence of steeply dipping structures in the lewisian autochthon buried beneath the moine nappe

an experimental study of the surface thermal signature of hot subaerial isoviscous gravity currents implications for thermal monitoring of lava flows and domes received 22 july 2011 revised 23 november 2011 accepted 23 november 2011 published 7 february 2012 1 management of eruptions requires a knowledge of lava effusion rates for which a safe thermal proxy is often used however this thermal proxy does not take into account the flow dynamics and is basically time independent in order to establish a more robust framework that can link eruption rates and surface thermal signals of lavas measured remotely we investigate the spreading of a hot isoviscous axisymmetric subaerial gravity current injected at constant rate from a point source onto a horizontal substrate we performed laboratory experiments and found that the surface thermal structure became steady after an initial transient we develop a theoretical model for a spreading fluid cooled by radiation and convection at its surface that also predicts a steady thermal regime we show that despite the model s simplicity relative to lava flows it yields the correct order of magnitude for the effusion rate required to produce the radiant flux measured on natural lava flows for typical thermal lava properties and an effusion rate between 0 1 and 10 m 3 s 1 the model predicts a steady radiated heat flux ranging from 10 8 to 10 10 w the assessed effusion rate varies quasi linearly with the steady heat flux with much weaker dependence on the flow viscosity this relationship is valid only after a transient time which scales as the diffusive time ranging from a few days for small basaltic flows to several years for lava domes the thermal proxy appears thus less reliable to follow sharp variations of the effusion rate during an eruption

pāhoehoe flow cooling discharge and coverage rates from thermal image chronometry 1 theoretically and empirically derived cooling rates for active p hoehoe lava flows show that surface cooling is controlled by conductive heat loss through a crust that is thickening with the square root of time the model is based on a linear relationship that links log time with surface cooling this predictable cooling behavior can be used assess the age of recently emplaced sheet flows from their surface temperatures using a single thermal image or image mosaic this allows quantification of the variation in areal coverage rates and lava discharge rates over 48 hour periods prior to image capture for p hoehoe sheet flow at k lauea hawai i this gives coverage rates of 1 5 m2 min at discharge rates of 0 01 0 05 m3 s increasing to 40 m2 min at 0 4 0 5 m3 s our thermal chronometry approach represents a quick and easy method of tracking flow advance over a three day period using a single thermal snap shot

geochronological evidence for reworking of archean terrains during the early proterozoic 2 1 ga in the western coˆte d ivoire man rise west african craton abstract a period of accretion of continental crust is recognized during the archean at ca 3 2 3 3 ga on the basis of wholerock nd model ages and pb ages on detrital zircons from various gneisses of the man area in co te d ivoire there is no significant evidence of any older event such as the 3 5 3 6 ga accretion episode recognized in the archean of the reguibat rise in mauritania the earliest magmatic events recorded in the northern domain of the man area correspond to tonalitic grey gneisses of a minimum age ca 3 05 ga leonian event a subsequent major phase of igneous and metamorphic activity around 2 8 ga liberian event is recorded in the entire archean terrain without any evidence of new accretion this second event began at 2830 7 ma its climax is indicated by charnockitic intrusions followed by granodioritic magmas at ca 2800 10 pb pb and u pb ages on monazite and zircon cooling after the liberian event occurred ca 2 75 ga ago k feldspar whole rock garnet sm nd ages paleoproterozoic reworking is mainly found in the southern part of the archean terrain of the man area zircon monazite sphene and garnet geochronometers all indicate an important thermal effect during the birimian event i e 2 1 ga the earliest influence of this event is recorded in a range of 2250 40 70 ma with a major event ca 2 1 ga partial to total resetting of u pb and sm nd geochronometers indicate that high temperature conditions were reached during the birimian event this metamorphic overprint and the diapiric emplacement of coeval paleoproterozoic juvenile magmas at 2 1 ga in the southern domain toule pleu massif suggest that the 2 1 ga overprint could be related to major underplating processes under the archean basement the thermal flow related to the differentiation and the accretion of these juvenile birimian magmas may account for the reworking of the surrounding archean domain which had been possibly thinned during underplating these results suggest close proximity between the archean continents and an accretion zone associated with juvenile magmatism 2 1 ga ago

inferring phases of thermal unrest at mt asama japan from infrared satellite observations abstract on 1 september 2004 a vulcanian eruption the strongest since 1983 occurred at mt asama one of the most active volcanoes in japan an ash plume that rose 2 km above the crater was emitted together with incandescent blocks ejected several kilometers away from the summit crater subsequently after a short quiescence period of about 2 weeks a series of minor eruptions took place from 14 september they were considered unusual for mt asama for the presence of juvenile material dominant among fallout small and moderate eruptions continued even in the following months to end in december 2004 on the basis of gps observations a dike intrusion occurred under the western flank of mt asama about 6 weeks before 1 september eruption triggering the magma ascension towards the surface this phenomenon produced many signs of unrest including a thermal activity observed on the ground from the end of july 2004 the retrospective analysis presented in this paper performed applying the rst volc algorithm to moderate resolution imaging spectroradiometer modis data shows the occurrence of pre eruptive hot spots at mt asama during 1 31 august and 11 12 september 2004 these results extend observations of a previous modis based independent study and show the occurrence of a distinct phase of thermal unrest of short time duration a few days before the 14 september minor eruption moreover by the temporal trend of radiative power from infrared data time of occurrence of dome extrusion is also estimated in good agreement with independent radar observations these outcomes seem to be compatible with different mechanisms of upward propagation of magma speculated by previous authors confirming the potential of infrared satellite observations in identifying thermal precursory signals of volcanic eruptions provided that proper detection algorithms are used

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

thermal precursors in satellite images of the 1999 eruption of shishaldin volcano shishaldin volcano unimak island alaska began showing signs of thermal unrest in satellite images on 9 february 1999 a thermal anomaly and small steam plume were detected at the summit of the volcano in short wave thermal infrared avhrr advanced very high resolution radiometer satellite data this was followed by over 2 months of changes in the observed thermal character of the volcano initially the thermal anomaly was only visible when the satellite passed nearly directly over the volcano suggesting a hot source deep in the central crater obscured from more oblique satellite passes the zenith angle needed to see the anomaly increased with time presumably as the thermal source rose within the conduit based on this change an ascent rate of ca 14 m per day for the thermal source was estimated until it reached the summit on around 21 march it is thought that strombolian activity began around this time the precursory activity culminated in a sub plinian eruption on 19 april ejecting ash to over 45 000 ft 13 700 m the thermal energy output through the precursory period was calculated based on geometric constraints unique to shishaldin these calculations show fluctuations that can be tied to changes in the eruptive character inferred from seismic records and later geologic studies the remote location of this volcano made satellite images a necessary observation tool for this eruption to date this is the longest thermal precursory activity preceding a sub plinian eruption recorded by satellite images in the region this type of thermal monitoring of remote volcanoes is central in the efforts of the alaska volcano observatory to provide timely warnings of volcanic eruption and mitigate their associated hazards to air traffic and local residents

measuring effusion rates of obsidian lava flows by means of satellite thermal data abstract space based thermal data are increasingly used for monitoring effusive eruptions especially for calculating lava discharge rates and forecasting hazards related to basaltic lava flows the application of this methodology to silicic more viscous lava bodies such as obsidian lava flows is much less frequent with only few examples documented in the last decades the 2011 2012 eruption of cordon caulle volcano chile produced a voluminous obsidian lava flow 0 6 km3 and offers an exceptional opportunity to analyze the relationship between heat and volumetric flux for such type of viscous lava bodies based on a retrospective analysis of modis infrared data mirova system we found that the energy radiated by the active lava flow is robustly correlated with the erupted lava volume measured independently we found that after a transient time of about 15 days the coefficient of proportionality between radiant and volumetric flux becomes almost steady and stabilizes around a value of 5 106 j m 3 this coefficient i e radiant density is much lower than those found for basalts 1 108 j m 3 and likely reflects the appropriate spreading and cooling properties of the highly insulated viscous flows the effusion rates trend inferred from modis data correlates well with the tremor amplitude and with the plume elevation recorded throughout the eruption thus suggesting a link between the effusive and the coeval explosive activity modelling of the eruptive trend indicates that the cordon caulle eruption occurred in two stages either incompletely draining a single magma reservoir or more probably tapping multiple interconnected magmatic compartments

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

a comparison of field and satellite derived thermal flux at piton de la fournaise implications for the calculation of lava discharge rate we present thermal measurements made by high spatial resolution ground based a hand held thermal camera and low spatial resolution space based modis instruments for a lava flow field active during the last phase of the may july 2003 eruption at piton de la fournaise la reunion multiple oblique ground based thermal images were merged to provide full coverage of the flow field these were then corrected for path length attenuation and orthorectified allowing the at surface radiance emitted by the flow field to be estimated comparison with the radiance recorded by the modis sensors during the eruption reveals that for clear sky conditions and moderate to low viewing angles satellite zenith 40 the satellite measurements represent 90 of the at surface radiance and thus represent valuable data for quantifying volcanic thermal anomalies nevertheless extreme viewing geometries and the presence of clouds strongly affect the radiance reaching the sensor and affected data from 94 of the overpasses ground based thermal data were used to investigate an empirical relationship between the radiant heat flux and lava discharge rate during the emplacement of pahoehoe flows while the average radiation temperature for flow surface that were 6 24 h old ranged between 500 k and 625 k the ratio between radiative heat flux and time averaged lava discharge rate tadr ranged between 1 5 108 j m 3 and 3 5 108 j m 3 this relationship was used to estimate tadr values from optimal modis data and produced results in line with those obtained from gps surveys coppola et al 2005 our results underscore the importance of ground based thermal analysis for the interpretation of satellite measurements particularly in terms of calculating discharge rate trends

igneous emplacement in a transpressive shear zone ox mountains igneous complex the central and southwestern ox mountains inlier in western ireland comprises amphibolite facies metasediments and metavolcanic rocks which have been deformed by a major sinistral shear zone granitoid emplacement occurred in two distinct styles in the ox mountains shear zone the older pluton the ox mountains granodiorite was emplaced syn kinematically with respect to the main sinistral transpressional events in its wall rocks it was emplaced as a series of compositionally distinct sheets in the central part of the shear zone system thus suggesting the formation of transient dilational sites occurred in response to the transpressive deformation the younger lough talt and easky lough adamellites were emplaced as individual intrusions in dilational cavities produced by reactivated movements on a discrete zone within the ox mountains inlier the different intrusive styles are considered to be a product of the tectonic regimes operating during emplacement intrusion into transient dilational cavities may be one method by which granitoid magmas are emplaced into fault zones undergoing active contractional deformation

a simple explanation for the space based calculation of lava eruption rates abstract knowing how lava effusion rates vary during basaltic eruptions can be of great significance when trying to provide preliminary forecasts regarding how far lava will flow however problems exist in accurately determining effusion rates using conventional field based techniques to ameliorate this problem harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 developed a method for determining effusion rates using infrared satellite data and showed how the method could be used to provide realistic estimates of effusion rates repeatedly during several eruptions at kilauea hawai i krafla iceland etna and stromboli italy harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 indicate that their method allows instantaneous lava effusion rates to be determined thermodynamically by equating the amount of heat lost by an active lava flow derived from the satellite data to the amount of heat liberated by the cooling mass of lava the purpose of this paper is to provide a simpler alternative explanation we find that rather than being used to calculate heat loss harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 actually use the satellite data to estimate the area of active lava present within the satellite s field of view at the movement of data acquisition thus changes in the effusion rates they present can only be proportional to changes in this area the active flow areas were then multiplied by a constant the value of which is obtained from a crude approximation of the lava flows heat balance crucially the absolute value of this term falls within the range of an empirically derived parameter that was found by pieri and baloga j volcanol geotherm res 30 1986 29 45 to explain strong linear correlations between eruption rate i e the time averaged effusion rate and lava flow area for 34 historic hawaiian flows as a result we find that the method of harris et al j geophys res 102 1997 7985 8003 does not yield instantaneous effusion rates but instead provides a valid and useful way to estimate average effusion rates i e the eruption rate from measurements of flow area

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

automated volcanic eruption detection using modis abstract the moderate resolution imaging spectroradiometer modis flown on board nasa s first earth observing system eos platform terra offers complete global data coverage every 1 2 days at spatial resolutions of 250 500 and 1000 m its ability to detect emitted radiation in the short 4 m and long 12 m wave infrared regions of the electromagnetic spectrum combined with the excellent geolocation of the image pixels 200 m makes it an ideal source of data for automatically detecting and monitoring high temperature volcanic thermal anomalies this paper describes the underlying principles of and results obtained from just such a system our algorithm interrogates the modis level 1b data stream for evidence of high temperature volcanic features once a hotspot has been identified its details location emitted spectral radiance satellite observational parameters are written to an ascii text file and transferred via file transfer protocol ftp to the hawaii institute of geophysics and planetology higp where the results are posted on the internet http modis higp hawaii edu the global distribution of volcanic hotspots can be examined visually at a variety of scales using this website which also allows easy access to the quantitative data contained in the ascii files themselves we outline how the algorithm has proven robust as a hotspot detection tool for a wide range of eruptive styles at both permanently and sporadically active volcanoes including soufriere hills montserrat popocatepetl mexico bezymianny russia and merapi java amongst others we also present case studies of how the system has allowed the onset development and cessation of discrete eruptive events to be monitored at nyamuragira congo piton de la fournaise reunion island and shiveluch russia

evidence for significant granite space creation by the ballooning mechanism the example of the ardara pluton ireland the emplacement mechanism of the ardara granite a caledonian pluton located on the northwestern seaboard of ireland has been a widely cited and a key point of reference in the debate about the granite space problem for nearly half a century early models related its subcircular tailed shape concentric foliation pattern and concentrically deformed envelope to diapirism it was subsequently reinterpreted using strain data as a ballooning pluton that was created by 70 in situ expansion at the emplacement site and was later cut by a regional shear zone recently it was the leading example in a wide ranging review of forcefully emplaced plutons of this type and was reinterpreted as a series of nested diapirs associated with only modest amounts 30 of forceful space creation but a large component of inferred early block stoping we report the results of the complete remapping and extensive collection of new structural data from this 8 km diameter normally zoned three phase calc alkaline pluton we confirm the existence of the steeply inclined internal foliation pattern and that it was formed in the magmatic state although this and the outline of the pluton are modified by late stage high temperature solid state regional transcurrent shear zones along two of the pluton contacts structural mapping has failed to identify a macroscopic lineation in the magmatic foliation planes and this is confirmed by strain determinations using mafic enclave populations and magmatic crystal separations for the magmatic state deformation that show nearly pure flattening type strains k 0 strains measured by these techniques show an apparently smooth gradient increasing outward toward the pluton contacts from an inner low strain zone we argue that these features together with the simple normal petrographic zonation a lack of small scale structures that would indicate the pluton had moved up relative to the wall rocks and an exposure level that is not in the roof zone are inconsistent with diapirism either singly or multiply but are most easily explained by a ballooning emplacement mechanism synmagmatic shear sense data from both the pluton and the adjacent country rocks indicate however that within the overall context of radial ballooning there was a limited amount of late stage nonradial northward injection of magma an inversion of the deformed enclave and crystal spacing strain determinations and strain determinations within the country rocks suggest that more than 80 of the volume of the pluton was accommodated by the ballooning mechanism

regional earthquake as a trigger for enhanced volcanic activity evidence from modis thermal data 1 the magnitude 6 4 earthquake that occurred in java on 26 may 2006 provided us with data capable of revealing an immediate eruptive response at two javanese volcanoes merapi and semeru the availability of pre processed thermal data for volcanic hot spots detected by the moderate resolution imaging spectrometer modis and provided on http hotspot higp hawaii edu allowed us to produce heat and volume flux time series for these two erupting volcanoes covering a 35 day period spanning the earthquake our results revealed a coupled response by the volcanoes to the earthquake both experiencing increases in heat and volume flux beginning 3 days after the earthquake with the response lasting 9 days the response was felt at both volcanoes as a factor of two to three increase in the rate of volumetric output after which output returned to the pre response rates this implies that the earthquake triggered enhanced output at two erupting volcanoes 50 and 300 km distant from the earthquake epicenter and separated from each other by 260 km

field thermal monitoring during the august 2003 eruption at piton de la fournaise la reunion 1 a detailed set of thermal images collected during the last day of the august 2003 eruption of piton de la fournaise la reunion clearly revealed several dynamic processes associated with a spatter cone containing a lava pond and feeding a channelized lava flow periods of steady effusion were interrupted by brief pulses of lava effusion that closely coincide with peaks in seismic tremor amplitude the thermal measurements show that roofing of a lava channel during steady effusion and cooling of surface flows decrease thermal radiance in two different ways here we show that the decrease in thermal radiance because of channel roofing is not related to a decrease in volcanic activity as might be interpreted from satellite data in addition we introduce a new method of representing thermal data hereby named radiative thermogramme that successfully describes thermal patterns produced by distinct eruptive processes within the same span of time this graphic solution can be directly correlated with volcanic field processes and provides a useful tool for interpreting a high number of thermal data in a wide range of volcanic activities

low cost volcano surveillance from space case studies from etna krafla cerro negro fogo lascar and erebus satellite data offer a means of supplementing ground based monitoring during volcanic eruptions especially at times or locations where ground based monitoring is difficult being directly and freely available several times a day data from the advanced very high resolution radiometer avhrr offers great potential for near real time monitoring of all volcanoes across large 3000 3000 km areas herein we describe techniques to detect and locate activity estimate lava area thermal flux effusion rates and cumulative volume and distinguish types of activity application is demonstrated using data for active lavas at krafla etna fogo cerro negro and erebus a pyroclastic flow at lascar and open vent systems at etna and stromboli automated near real time analysis of avhrr data could be achieved at existing or cheap to install receiving stations offering a supplement to conventional monitoring methods

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

the archaean kasila group of western sierra leone geology and relations with adjacent granite greenstone terrane abstract the kasila group an archaean highly metamorphosed supracrustal succession composed of basaltic igneous clastic and chemical sedimentary rocks outlines the western border of the granite greenstone terrane of the west african craton in sierra leone the contact between the two tectonic units is characterised by intense overthrust ductile shear deformation operating during the late archaean at high metamorphic grade followed by increasingly brittle shear motions of the same sense indicating prolonged eastwards directed overthrusting subsequent to the formation of the adjacent granite greenstone terrane to the east the kasila group poor in granitic intrusives is unlike archaean granite greenstone and high grade gneiss terranes and may represent the deep seated remains of a telescoped supracrustal succession perhaps resulting from the collision and suturing of archaean terranes now represented by the west african craton and the guyana shield

effusive to explosive transition during the 2003 eruption of stromboli volcano the persistent explosive activity of stromboli volcano italy ceased in december 2002 and correlated with the onset of a seven month long effusive eruption on the volcano flank from new vents that opened just below the summit craters we intensively monitored this effusive event collecting and interpreting in real time an extensive multiparametric geophysical data set the resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical strombolian activity we present a direct link between gas flux magma volume flux and seismicity supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity this insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity

image based measurement of flux variation in distal regions of active lava flows 1 understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes here we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active a flows in order to investigate distal flow processes at mount etna sicily photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow fronts velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava significant variations of the magma flux were observed and pulses of increased flux arrived within the flow front region on timescales of several hours the pulses are believed to be the distal result of more frequent flux changes observed in the vent region hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short period variations in effusion rate in considering advance processes for the individual flow fronts it must be assumed that they were fed by a highly unsteady flux which was volumetrically at least an order of magnitude lower than that observed near the vent

analysis of volcanic activity patterns using modis thermal alerts we investigate eruptive activity by analysis of thermal alert data from the modis moderate resolution imaging spectrometer thermal infrared satellite instrument detected by the modvolc modis volcano alert algorithm these data are openly available on the internet and easy to use we show how such data can plug major gaps in the conventional monitoring record of volcanoes in an otherwise generally poorly documented region melanesia including characterising the mechanism of lava effusion at pago demonstrating an earlier than realised onset of lava effusion at lopevi extending the known period of lava lake activity at ambrym and confirming ongoing activity at bagana langila and tinakula we also add to the record of activity even at some generally better monitored volcanoes in indonesia but point out that care must be taken to recognise and exclude fires

rheological control on the radiant density of active lava flows and domes abstract during an effusive extrusive eruption the capability of an active lava body flow or dome to radiate thermal energy depends on how the lava discharge rate is accommodated by the expansion of the magma body and by the cooling of its surface this feature can be described by a single empirical parameter defined radiant density c rad in j m 3 that for a given discharge rate expresses the efficiency of the lava body to change its area and or to insulate its inner core thus modulating the heat radiated from the active surface by comparing the volcanic radiative energy vre in j detected by modis during 28 eruptions at 18 active volcanoes with their erupted lava volumes vol in m 3 we show that the radiant density c rad vre vol is inversely proportional to the silica content of the erupted lava basic lavas 45 52 wt sio 2 have the highest observed radiant density 1 to 4 10 8 j m 3 while intermediate 52 63 wt sio 2 and acidic 63 wt sio 2 lavas show a gradually lower radiant densities 1 5 to 9 10 7 j m 3 and 0 2 to 1 10 7 j m 3 for intermediate and acidic composition respectively we regard this correlation as the result of the control that the rheology of lavas exerts on cooling and spreading processes of related bodies in particular we found that for any given compositional group the radiant density is essentially related to a characteristic thickness of active lavas at the time of a satellite acquisition we suggest that the radiant density of effusive extrusive lava bodies can be predicted 50 by means of an empirical relationship based on the sio 2 content of the erupted lava this makes this parameter very useful in observing volcanic activity especially in remote regions where access may not be possible by measuring the energy radiated during an eruption and by assuming a lava composition based on the tectonic setting or magmatic province we suggest that the radiant density can be used to estimate lava discharge rates and erupted volumes for volcanoes characterised by effusive or extrusive activity