geomorphometric analysis of the 2014 2015 barðarbunga volcanic eruption iceland abstract topographical information is of fundamental interest for a wide range of disciplines including glaciology agriculture communication network planning or hazard management in volcanology elevation data are of particular importance when assessing material flows throughout a volcanic system to obtain accurate estimates of time varying topography in volcanic active regions high resolution digital elevation models dems are required to monitor and evaluate topographical changes and especially volumetric gains and losses during the 2014 2015 bar arbunga eruption iceland multi temporal tandem x dem sequences were evaluated the 2014 2015 volcanic eruption was associated with the rare event of a caldera collapse visible on the surface of the vatnajokull glacier as well as major lava effusion in the holuhraun plain before investigating topographical change at the two study areas the tandem x dems were analysed for absolute and relative height errors resulting from the radar system parameters the sar processing or the local environment the uncertainty investigation determined that acquisitions over the snow covered bar arbunga caldera were primarily affected by microwave penetration into snow and dems over the holuhraun lava field exhibited increased height errors due to active lava flows and dynamic outwash plain the topographical analysis of the 2014 2015 bar arbunga eruption revealed a maximum vertical displacement of approximately 65 m and 43 m at the study area of the bar arbunga caldera and holuhraun lava field respectively with a total subsidence volume of 1 40 0 13 km3 and a dense rock equivalent dre lava volume of 1 36 0 07 km3 known uncertainties in volume were decreased by approximately 35 and 77 accordingly taking into account the calculation of rates the temporal development of caldera collapse and lava effusion was found to exhibit a near exponential decrease the ratio between subsidence and dre lava volume moreover indicated the coupling between piston collapse and magma drainage

segmented lateral dyke growth in a rifting event at barðarbunga volcanic system iceland crust at many divergent plate boundaries forms primarily by the injection of vertical sheet like dykes some tens of kilometres long1 previous models of rifting events indicate either lateral dyke growth away from a feeding source with propagation rates decreasing as the dyke lengthens2 3 4 or magma flowing vertically into dykes from an underlying source5 6 with the role of topography on the evolution of lateral dykes not clear here we show how a recent segmented dyke intrusion in the bar arbunga volcanic system grew laterally for more than 45 kilometres at a variable rate with topography influencing the direction of propagation barriers at the ends of each segment were overcome by the build up of pressure in the dyke end then a new segment formed and dyke lengthening temporarily peaked the dyke evolution which occurred primarily over 14 days was revealed by propagating seismicity ground deformation mapped by global positioning system gps interferometric analysis of satellite radar images insar and graben formation the strike of the dyke segments varies from an initially radial direction away from the bar arbunga caldera towards alignment with that expected from regional stress at the distal end a model minimizing the combined strain and gravitational potential energy explains the propagation path dyke opening and seismicity focused at the most distal segment at any given time and were simultaneous with magma source deflation and slow collapse at the bar arbunga caldera accompanied by a series of magnitude m 5 earthquakes dyke growth was slowed down by an effusive fissure eruption near the end of the dyke lateral dyke growth with segment barrier breaking by pressure build up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries

modelling satellite derived magma discharge to explain caldera collapse many effusive eruptions are characterized by effusion rates that decay exponentially with time a trend which is generally ascribed to elastic relaxation of a deep magma chamber thermal emissions detected by satellite during the a d 2014 2015 bar arbunga holuhraun eruption iceland indicate that the volume of the erupted magma and effusion rates followed an overall exponential trend that fits the observed major subsidence of the bar arbunga caldera floor this trend continued until a critical flow rate was reached hence the subsidence slowed down and the eruption rapidly ceased reflecting the ultimate closure of the magma path we present a model of inelastic magma withdrawal that very closely reproduces all the observed phenomena and provides new insights into the caldera collapses and the driving pressure of other effusive eruptions

insar elevation bias caused by penetration into uniform volumes natural media like cold land ice vegetation and dry sand are subject to a substantial penetration at microwave frequencies for such media the synthetic aperture radar sar phase center is located below the surface and consequently the surface elevation determined with sar interferometry insar is biased downward for infinitely deep uniform volumes the elevation bias is often equated with the penetration depth but in this paper it is shown that the two quantities generally differ the interferometric bias is approximately equal to the two way power penetration depth if the latter is small compared to the ambiguity height but for increasing penetration depth the bias approaches one quarter of the ambiguity height consequently no phase wrapping results even if the penetration depth exceeds the ambiguity height the ratio of the insar elevation bias to the ambiguity height depends only on the ratio of the penetration depth to the ambiguity height and the bias can be expressed in terms of the insar coherence magnitude which makes it possible to correct the insar surface elevation for the bias the volume depth can be considered infinite if it exceeds the penetration depth by a factor of two to five and if the surface scattering from the top and the bottom of the volume is negligible

chronology and products of the 2000 eruption of miyakejima volcano japan lateral migration of magma away from miyakejima volcanic island japan generated summit subsidence associated with summit explosions in the summer of 2000 an earthquake swarm beneath miyakejima began on the evening of 26 june 2000 followed by a submarine eruption the next morning strong seismic activity continued under the sea from beneath the coast of miyakejima to a few tens of kilometers northwest of the island summit eruptive event began with subsidence of the summit on 8 july and both explosions and subsidence continued intermittently through july and august the most intense eruptive event occurred on 18 august and was vulcanian to subplinian in type ash lofted into the stratosphere fell over the entire island and abundant volcanic bombs were erupted at this time another large explosion took place on 29 august this generated a low temperature pyroclastic surge which covered a residential area on the northern coast of the island the total volume of tephra erupted was 9 3 106 m3 dre much smaller than the volume of the resulting caldera 6 108 m3 migration of magma away from miyakejima was associated with crustal extension northwest of miyakejima and coincident shrinkage of miyakejima island itself during july august 2000 this magma migration probably caused stoping of roof rock into the magma reservoir generating subsurface cavities filled with hydrothermal fluid and or magmatic foam and formation of a caldera oyama caldera at the summit interaction of hydrothermal fluid with ascending magma drove a series of phreatic to phreatomagmatic eruptions it is likely that new magma was supplied to the reservoir from the bottom during waning stage of magma s migration resulting in explosive discharge on 18 august the 18 august event and phreatic explosions on 29 august produced a conduit system that allowed abundant so2 emission as high as 460 kg s 1 after the major eruptive events were over at the time of writing inhabitants of the island about 3 000 have been evacuated from miyakejima for more than 3 years

origins of oblique slip faulting during caldera subsidence 1 although conventionally described as purely dip slip faults at caldera volcanoes may have a strike slip displacement component examples occur in the calderas of olympus mons mars miyakejima japan and dolomieu la reunion to investigate this phenomenon we use numerical and analog simulations of caldera subsidence caused by magma reservoir deflation the numerical models constrain mechanical causes of oblique slip faulting from the three dimensional stress field in the initial elastic phase of subsidence the analog experiments directly characterize the development of oblique slip faulting especially in the later non elastic phases of subsidence the combined results of both approaches can account for the orientation mode and location of oblique slip faulting at natural calderas kinematically oblique slip faulting originates to resolve the following 1 horizontal components of displacement that are directed radially toward the caldera center and 2 horizontal translation arising from off centered or asymmetric subsidence we informally call these two origins the camera iris and sliding trapdoor effects respectively our findings emphasize the fundamentally three dimensional nature of deformation during caldera subsidence they hence provide an improved basis for analyzing structural geodetic and geophysical data from calderas as well as analogous systems such as mines and producing hydrocarbon reservoirs

time averaged discharge rate of subaerial lava at kīlauea volcano hawai i measured from tandem x interferometry implications for magma supply and storage during 2011 2013 differencing digital elevation models dems derived from terrasar add on for digital elevation measurements tandem x synthetic aperture radar imagery provides a measurement of elevation change over time on the east rift zone ezr of k lauea volcano hawai i the effusion of lava causes changes in topography when these elevation changes are summed over the area of an active lava flow it is possible to quantify the volume of lava emplaced at the surface during the time spanned by the tandem x data a parameter that can be difficult to measure across the entirety of an 100 km2 lava flow field using ground based techniques or optical remote sensing data based on the differences between multiple tandem x derived dems collected days to weeks apart the mean dense rock equivalent time averaged discharge rate of lava at k lauea between mid 2011 and mid 2013 was approximately 2 m3 s which is about half the long term average rate over the course of k lauea s 1983 present erz eruption this result implies that there was an increase in the proportion of lava stored versus erupted a decrease in the rate of magma supply to the volcano or some combination of both during this time period in addition to constraining the time averaged discharge rate of lava and the rates of magma supply and storage topographic change maps derived from space based tandem x data provide insights into the four dimensional evolution of k lauea s erz lava flow field tandem x data are a valuable complement to other space air and ground based observations of eruptive activity at k lauea and offer great promise at locations around the world for aiding with monitoring not just volcanic eruptions but any hazardous activity that results in surface change including landslides floods earthquakes and other natural and anthropogenic processes

the collapse of barðarbunga caldera iceland lying below vatnajokull ice cap in iceland bar arbunga stratovolcano began experiencing wholesale caldera collapse in 2014 august 16 one of the largest such events recorded in the modern instrumental era simultaneous with this collapse is the initiation of a plate boundary rifting episode north of the caldera observations using the international constellation of radar satellites indicate rapid 50 cm d 1 subsidence of the glacier surface overlying the collapsing caldera and metre scale crustal deformation in the active rift zone anomalous earthquakes around the rim of the caldera with highly nondouble couple focal mechanisms provide a mechanical link to the dynamics of the collapsing magma chamber a model of the collapse consistent with available geodetic and seismic observations suggests that the majority of the observed subsidence occurs aseismically via a deflating sill like magma chamber

physicochemical models of effusive rhyolitic eruptions constrained with insar and dem data a case study of the 2011 2012 cordon caulle eruption abstract the 9 month long 2011 2012 eruption of cordon caulle southern andes chile is the best instrumentally recorded rhyolitic eruption to date and the first time that the effusion of a rhyolitic flow has been observed in detail we use interferometric synthetic aperture radar insar with time lapse digital elevation models dems and numerical models to study the dynamics of coupled magma reservoir deflation and lava effusion insar recorded 2 2 2 5 m of subsidence after the first three days of the eruption which can be modeled using a spheroidal magma reservoir at a depth of 5 km 20 km long and with a pressure drop of 20 30 mpa the source is elongated in the nw se direction and its large dimensions imply a large plumbing system active throughout the eruption and spanning neighboring volcanoes with a slight change in the geometry halfway through the effusive phase tandem x and pleiades dems record the extrusion of both the rhyolitic lava flow and the intrusion of a shallow laccolith around the eruptive vent after the third day of the eruption with a total volume of 1 45 km3 dre the laccolith was emplaced during the first month of the eruption during both the explosive and effusive stages of the eruption both the reservoir pressure drop and the extruded volume time series follow quasi exponential trends and can be explained by a model that couples the reservoir pressure decrease time and pressure dependent variations in the magma properties inside of the reservoir and conduit flow this model predicts both the temporal evolution and amplitude of both time series during the effusive phase and a magma compressibility of 10 10 pa 1 half the reported compressibility of the magma of the sub plinian explosive phase further we estimate that the reservoir contained 1 3 wt dissolved h2o at the onset of lava effusion with no exsolved co2 and h2o in the reservoir throughout the effusive phase this implies that the magma was significantly degassed after the explosive phase the remaining volatiles in the magma after the explosive stage might have caused magma fragmentation consistent with the hybrid explosive effusive style observed during the waning of the eruption

lava flow volume and morphology from digitised contour maps a case study at mount etna sicily abstract the volume and morphology of a lava flow field can be measured by mapping and comparing the topography before and after lava emplacement contour maps are a widely available source of topographic data containing a record of the geomorphological changes at volcanoes due to lava emplacement this paper explores the use of 1 25 000 scale digitised contour maps for mapping two lava flows of diverse eruption history and morphology at mount etna sicily we find that subtracting dems created from these maps gives a good representation of volume and shape for thicker lava flows 10 m mean thickness in the case of the 1983 lava flow however thinner

using tandem x to measure pyroclastic flow source location thickness and volume application to the 3rd june 2018 eruption of fuego volcano guatemala abstract the estimation of the volume of volcanic flows during an ongoing eruption is challenging but this information is crucial for improving risk assessment and for forecasting future events although previous studies have shown the ability of tandem x satellite data to derive the thickness and the volume of lava flow fields during effusive eruptions the method has not been explored yet for pyroclastic flows using bi static interferometry we produce tandem x dem on fuego volcano guatemala to measure the significant topographic changes caused by the 3rd june 2018 eruption which destroyed the town of san miguel los lotes we estimate the volume of the pyroclastic density currents pdcs to be 15 1 4 2 106 m3 the deposits are likely to be the source of lahars during future rainy seasons we identify the main channel of deposition positive elevation changes and the source region of pyroclastic material areas of significant substrate erosion and vegetation destruction negative elevation changes our results show that the june 3rd 2018 pyroclastic flow was predominantly composed of material which had gravitationally collapsed from a location close to the vent the eroded material increased the volume of the flow bulking and likely caused the run out distance of the 2018 pdc to be larger than previous eruptions 1999 2017 this study highlights the potential of remote sensing techniques for actively monitoring topography changes in inaccessible locations and to rapidly derive deposit volumes

size and volume evaluation of the caldera collapse on piton de la fournaise volcano during the april 2007 eruption using aster stereo imagery 1 the scale of summit collapse during the april 2007 eruption of piton de la fournaise volcano reunion island western indian ocean was evaluated using before and after differential digital elevation models dems derived from nadir and backward looking images from the advanced spaceborne emission and reflection radiometer aster instrument the dimensions of horizontal length and width volume and depth of the depression were estimated as 1 100 800 m 9 6 10 7 m 3 and 320 m respectively these estimates show excellent agreement with field survey data a ring shaped thermal anomaly diameter of about 500 m was found at dolomieu crater during or just after the collapse on nighttime aster swir image it may correspond to the high temperature areas associated with the cross section of a hydrothermal zone at a constant altitude inside the crater our analysis of aster orbital data documents topographic and related thermal changes as a result of the 2007 eruption and demonstrates the power of aster as a volcanological tool citation urai m n geshi and t staudacher 2007 size and volume evaluation of the caldera collapse on piton de la fournaise volcano during the april 2007 eruption using aster stereo imagery geophys

volumetric change quantification of the 2010 merapi eruption using tandem x insar abstract accurate and up to date information on the time varying topography of active volcanoes is crucial for assessing material flows through these volcanic systems and along their surfaces as dome building volcanoes can change on meter scale within short time intervals in active phases conventionally used repeat pass sar interferometry insar often fails due to decorrelation effects while other methods to measure topography like aerial photogrammetry or lidar depend on the availability of the local infrastructure and on good weather conditions here we show the potential of the spaceborne earth observation mission tandem x to monitor topographic changes at active dome building volcanoes in this innovative satellite mission two nearly identical satellites fly in a close formation taking radar images of the earth s surface at the same time in bistatic mode this opens the possibility to generate digital elevation models dems of volcanoes analyzing a series of repeated dems enables assessment of volume changes caused by lava dome activity we apply this method to merapi in indonesia by analyzing the volume changes during the hazardous 2010 eruption during this eruption the old lava dome collapsed and a new lava dome was extruded which collapsed again within twelve days we show three dems derived from bistatic tandem x insar in descending orbit taken before and after the eruption we found a mean volume change of 19 10 6 m 3 in the summit area the two estimates differ by 0 4 10 6 m 3 which is 2 of the average dome volume change the tandem x based results are about 25 lower than reference data which can be explained by the shadow masks that were introduced to exclude geometrically decorrelated areas resulting in conservative volume change estimates

volcanic sands of iceland diverse origins of aeolian sand deposits revealed at dyngjusandur and lambahraun the origin formation and evolution of volcanic sands are less well known than the formation of the much more common quartz rich sand sheets combining active volcanism and a cold climate iceland is covered for about 21 of its surface by sandy areas the sands were analyzed in detail at two sites and results reveal their diverse origins the first site is dyngjusandur located north of vatnajokull and the second site is the lambahraun area located south of langjokull at both sites the sand origin is determined from field observations wind directions from ventifacts chemical and mineralogical analyses of rocks and sands at dyngjusandur the sand is dominated by glass grains a situation typical of sand plains in iceland hyaloclastite ridges presently buried beneath vatnajokull are the dominant source of the sand and only large size plagioclase crystals 0 5 cm in sands seem to be derived from the lava flows hyaloclastite ridges were crushed by glaciers and mechanically eroded sediments were washed out by melt water onto flood plains the sand chemical composition is spatially homogeneous and similar to the average composition of neighboring sub aerial lava flows reflecting efficient mixing of distinct sources below the glacier the presence of sand north of dyngjujokull can be taken as a way to explore the average chemical composition of non exposed volcanic material beneath the glacier in the case of lambahraun prevailing winds indicate several potential sources of sand at the north of the sand sheet comparison of chemical and mineralogical analyses of sands and rock samples helped to refine the exact origin in contrast with the first site the sand is dominated by crystals and is chemically consistent with a mixture of material derived from the lava flows of eldborgir and skersli shield volcanoes analysis of the contact between the lava flows and the glacier reveals that basaltic sand grains formed as the result of recent advances of the glacier abrading the rocks the direct interaction of glacial and fluvio glacial activity with basaltic plains appears to be necessary to produce a large amount of sands in a relatively short period of time 4000years this site appears to be an excellent natural laboratory for further studies concerning the sand evolution and physical sorting processes in basaltic material which have important implications for understanding aeolian processes on mars copyright c 2011 john wiley sons ltd

high resolution tandem x dem an accurate method to estimate lava flow volumes at nyamulagira volcano d r congo nyamulagira and nyiragongo are two of the most active volcanoes in africa but their eruptive histories are poorly known assessing lava flow volumes in the region remains difficult as field surveys are often impossible and available digital elevation models dems do not have adequate spatial or temporal resolutions we therefore use terrasar x add on for digital elevation measurement tandem x interferometry to produce a series of 0 15 arc sec 5 m dems from between 2011 and 2012 over these volcanoes tandem x dems have an absolute vertical accuracy of 1 6 m resulting from the comparison of elevation with gps measurements acquired around nyiragongo the difference between tandem x derived dems from before and after the 2011 2012 eruption of nyamulagira provides an accurate thickness map of the lava flow emplaced during that activity values range from 3 m along the margins to 35 m in the middle with a mean of 12 7 m the erupted volume is 305 2 36 0 106 m3 height errors on thickness depend on the land covered by the flow and range from 0 4 m in old lavas to 5 5 m in dense vegetation we also reevaluate the volume of historical eruptions at nyamulagira since 2001 from the difference between tandem x and srtm 1 arc sec dems and compare them to previous work planimetric methods used in literature are consistent with our results for short duration eruptions but largely underestimate the volume of the long lived 2011 2012 eruption our new estimates of erupted volumes suggest that the mean eruption rate and the magma supply rate were relatively constant at nyamulagira during 2001 2012 respectively 23 1 m3 s 1 and 0 9 m3 s 1

dissolution of aerosol iron in the surface waters of the north pacific and north atlantic oceans as determined by a semicontinuous flow through reactor method aerosol iron dissolution in oceanic waters is determined with a semicontinuous batch leaching method in this procedure aerosol samples that were collected from the marine boundary layer were leached in an all teflon flow through reaction chamber by multiple aliquots of similar to 40 ml 0 4 mu m filtered oceanic surface water collected using ultraclean techniques each aliquot of seawater is permitted to leach the aerosol sample in the reaction chamber for a predetermined time before the seawater solution is separated from the aerosol sample by a 0 4 mu m nucleopore filter membrane a new aliquot of seawater is then added to the leaching chamber to continue leaching the same aerosol particles retained on the filter the procedure is repeated with progressive increases in leaching time the method allows the fe released from the aerosol particles to be continuously removed from the system before saturating the complexation capacity of the seawater leaching solution or adsorbing onto the leaching chamber wall this method results in accurate measurements of seawater dissolvable labile aerosol fe that is independent of the total aerosol fe concentrations in the sample the aerosol fe solubility determined using this method ranges from 3 5 1 5 for the north atlantic during september 2005 to 5 7 2 0 for the north pacific during april 2005 and april 2006

september 2005 manda hararo dabbahu rifting event afar ethiopia constraints provided by geodetic data faults the volume of the 2005 dike 1 5 2 0 km 3 is not balanced by sufficient volume loss at dabbahu and gabho volcanoes 0 42 and 0 12 km 3 respectively taking into account the deflation of a suspected deep midsegment magma chamber simultaneously to dike intrusion produces a smoother opening distribution along the southern segment above the dike faults slipped by an average 3 m yielding an estimated geodetic moment of 3 5 10 19 nm one order of magnitude larger than the cumulative seismic moment released during the earthquake swarm between dabbahu and ado ale volcanic complexes significant opening occurred on the western side of the dike the anomalous location of the dike at this latitude offset to the east of the axial depression may explain this phenomenon a two stage intrusion scenario is proposed whereby rifting in the northern manda hararo rift was triggered by magma upwelling in the dabbahu area at the northern extremity of the magmatic segment although vigorous dike injection occurred during the september 2005 event the tectonic stress deficit since the previous rifting episode was not fully released leading to further intrusions in 2006 2009

composition and evolution of ore fluids in a magmatic hydrothermal skarn deposit the chemistry of brine vapor and low salinity fluid inclusions measured by proton induced x ray emission from the bismark skarn deposit mexico is consistent with an evolving magmatic hydrothermal system with no evidence for external fluid inputs the results support a model that invokes early phase separation of magmatic fluids into brine and vapor two phase field at high temperature and lithostatic pressure followed by the entrapment of a low salinity magmatic fluid one phase field at lower temperature and hydrostatic pressure the early brine and vapor inclusions contain high pb and zn concentrations and low cu however the vapor contains significantly more cu than the brine and was likely transported as a sulfur complex the fluid phase changes observed and behavior of cu are comparable to those of porphyry cu systems the later low salinity fluid at bismark represents a distinct pulse of magmatic fluid with a high k ca ratio in which base metals including cu were transported by chloride complexes paragenetic relationships and variations in the relative concentrations of cu pb and zn suggest that this fluid was primarily responsible for ore deposition the relative cu pb and zn concentrations in fluid inclusions at bismark are consistent with those measured from base metal ores in high temperature carbonate replacement deposits throughout mexico and suggest that the bulk metal budget of these deposits is primarily controlled by magmatic hydrothermal fluids deficient in cu

crustal deformation caused by magma migration in the northern izu islands japan intense crustal activity including earthquake swarms eruptions and a caldera formation in the northern izu islands started on june 26 2000 accompanied with large crustal deformation permanent gps data reveals the spatial pattern and time evolution of ground deformation the observations reveal shrinking and subsidence of miyakejima and extension between kouzushima and niijima we constructed a source model to explain the observed displacements during the period between june 26 and the end of august the model consists of a deflation source 0 12km beneath miyakejima tensile faults 1 04km located between miyakejima and kouzushima and several shear faults mass balance considerations suggest that a large amount of magma migrated 30km from miyakejima toward kouzushima

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

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

the april 2007 eruption and the dolomieu crater collapse two major events at piton de la fournaise la reunion island indian ocean abstract after 10 years of high activity and 24 eruptions piton de la fournaise pdf produced on april 2 to may 1 2007 one of its most voluminous and intense eruption since at least one century the eruption focused at 590 m elevation in the grand brule on the south east flank of piton de la fournaise 7 km away from summit it was located close to the southern cliff of the grand brule volcano tectonic collapse the rempart du tremblet and to the nearby village called le tremblet and it highly rattled and incommoded the inhabitants there eleven hours after the beginning of the eruption the lava flows reached the sea and created 0 45 km 2 of new land until the end of eruption in the night of april 5 the rock column beneath dolomieu crater started to collapse with a piston like mechanism into the magma chamber forming within less than 24 h the most recent and well documented caldera we report in this paper the chronology of these two related major events in the recent activity of pdf seen by the scientific networks of the volcanological observatory ovpf ipgp and field observations which allowed to back up the scenario of the caldera formation and to quantify these two exceptional episodes

interferometric synthetic aperture radar study of okmok volcano alaska 1992 2003 magma supply dynamics and postemplacement lava flow deformation 1 okmok volcano located in the central aleutian arc alaska is a dominantly basaltic complex topped with a 10 km wide caldera that formed circa 2 05 ka okmok erupted several times during the 20th century most recently in 1997 eruptions in 1945 1958 and 1997 produced lava flows within the caldera we used 80 interferometric synthetic aperture radar insar images interferograms to study transient deformation of the volcano before during and after the 1997 eruption point source models suggest that a magma reservoir at a depth of 3 2 km below sea level located beneath the center of the caldera and about 5 km northeast of the 1997 vent is responsible for observed volcano wide deformation the preeruption uplift rate decreased from about 10 cm yr 1 during 1992 1993 to 2 3 cm yr 1 during 1993 1995 and then to about 1 2 cm yr 1 during 1995 1996 the posteruption inflation rate generally decreased with time during 1997 2001 but increased significantly during 2001 2003 by the summer of 2003 30 60 of the magma volume lost from the reservoir in the 1997 eruption had been replenished interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows most likely due to thermal contraction interferograms for periods after the eruption suggest at least four distinct deformation processes 1 volcano wide inflation due to replenishment of the shallow magma reservoir 2 subsidence of the 1997 lava flows most likely due to thermal contraction 3 deformation of the 1958 lava flows due to loading by the 1997 flows and 4 continuing subsidence of 1958 lava flows buried beneath 1997 flows our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes

tracking lava flow emplacement on the east rift zone of kīlauea hawai i with synthetic aperture radar coherence 1 lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior although maps are traditionally created through field surveys remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location synthetic aperture radar sar imagery in particular can detect changes in a flow field by comparing two images collected at different times with sar coherence new lava flows radically alter the scattering properties of the surface making the radar signal decorrelated in sar coherence images we describe a new technique sar coherence mapping scm to map lava flows automatically from coherence images independent of look angle or satellite path we use this approach to map lava flow emplacement during the pu u kupaianaha eruption at k lauea hawai i the resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows as well as the locations of active flow paths however the scm technique is only moderately successful at mapping flows that enter vegetation which is also often decorrelated between successive sar images along with measurements of planform morphology we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness finally we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post emplacement flow subsidence

icecap and subglacial crustal deformation inferred from sar pixel tracking the 2014 dike intrusion episode in the barðarbunga volcanic system iceland

sources of crustal deformation associated with the krafla iceland eruption of september 1984 a decade long plate boundary rifting episode in northern iceland ended with the september 1984 fissure eruption of krafla volcano we apply a nonlinear inversion method to geodetic data collected before and after the eruption to infer the location geometry and strengths of deformation sources associated with the eruption the net outflow of magma from a 3 km deep magma chamber beneath the krafla caldera was 30 120 106 m a similar volume of magma 50 70 106 m was emplaced in a 1 meter wide 9 km long dike extending from the surface to 7 km depth furthermore at least 110 106 m of magma erupted accordingly a surplus of magma must have been expelled from a second reservoir the location of which although uncertain is likely to lie at depths greater than 5 km beneath krafla volcano it would be difficult to detect this deeper source because of the narrow aperture of the geodetic networks

insights into the 3d architecture of an active caldera ring fault at tendurek volcano through modeling of geodetic data abstract the three dimensional assessment of ring fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field geodetic or seismological data or by only partial ring fault rupture or slip here we use a novel combination of spatially dense insar time series data numerical models and sand box experiments to determine the three dimensional geometry and kinematics of a sub surface ring fault at tendurek volcano in turkey the insar data reveal that the area within the ring fault not only subsides but also shows substantial westward directed lateral movement the models and experiments explain this as a consequence of a sliding trapdoor ring fault architecture that is mostly composed of outward inclined reverse segments most markedly so on the volcano s western flanks but includes inward inclined normal segments on its eastern flanks furthermore the model ring fault exhibits dextral and sinistral strike slip components that are roughly bilaterally distributed onto its northern and southern segments respectively our more complex numerical model describes the deformation at tendurek better than an analytical solution for a single rectangular dislocation in a half space comparison to ring faults defined at glen coe fernandina and bar arbunga calderas suggests that sliding trapdoor ring fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring faults at different scales worldwide

experimental study of caldera formation scaled experiments have been carried out on caldera collapse mechanisms using silicone as analogue magma and dry sand as analogue rock experiments were carried out in two and three dimensions using a range of roof aspect ratios thickness width 0 2 to 4 5 appropriate for caldera collapse they reveal a general mechanism of collapse only weakly dependent on the shape of the reservoir for low roof aspect ratios 1 subsidence starts by flexure of the roof and the formation of outward dipping reverse ring faults which in turn trigger formation of peripheral inward dipping normal ring faults the subsidence always occurs asymmetrically in cross section the reverse faults delimit a coherent piston bounded on each side by an annular zone of inwardly tilted strata located between the reverse and normal ring fault sets the surface depression consists of a nondeformed area piston surrounded by an annular extensional zone tilted strata for high aspect ratios 1 multiple reverse faults break up the roof into large pieces and subsidence occurred as a series of nested wedges 2 d or cones 3 d the extensional zone dominates the surface depression in the case where preexisting regional faults do not play a major role the collapse mechanics of calderas probably depends strongly on the roof aspect ratio calderas with low roof aspect ratios are predicted to collapse as coherent pistons along reverse faults the annular extensional zone might be the source of the large landslides that generate intracaldera megabreccias collapse into magma reservoirs with high roof aspect ratios may be the origin of some funnel calderas where explosive reaming is not dominant

april 2007 collapse of piton de la fournaise a new example of caldera formation collapse calderas are frequent in the evolution of volcanic systems but very few have formed during historical times piton de la fournaise is one of the world s most active basaltic shield volcanoes the caldera collapse which occurred during the april 2007 lateral eruption is one of the few large documented collapse events on this volcano it helps to understand the mode and origin of caldera collapses in basaltic volcanoes field observations gps and seismic data show that the collapse occurred at an early stage of the eruption the cyclic seismic signal suggests a step by step collapse that directly influenced the lateral eruption rate likely the caldera results from the combined effect of i the progressive collapse of the plumbing system above the magma chamber since 2000 and ii the large amount of magma withdrawal during the early stage of the eruption by both a significant intrusion within the edifice and an important emission rate

the 2007 8 volcanic eruption on jebel at tair island red sea observed by satellite radar and optical images we use high resolution optical images and interferometric synthetic aperture radar insar data to study the september 2007 january 2008 jebel at tair eruption comparison of pre and post eruption optical images reveals several fresh ground fissures a new scoria cone near the summit and that 5 9 0 1 km2 of new lava covered about half of the island decorrelation in the insar images indicates that lava flowed both to the western and to the northeastern part of the island after the start of the eruption while later lavas were mainly deposited near the summit and onto the north flank of the volcano from the insar data we also estimate that the average thickness of the lava flows is 3 8 m resulting in a bulk volume of around 2 2 107 m3 we observe no volcano wide pre or post eruption uplift which suggests that the magma source may be deep the co eruption interferograms on the other hand reveal local and rather complex deformation we use these observations to constrain a tensile dislocation model that represents the dike intrusion that fed the eruption the model results show that the orientation of the dike is perpendicular to the red sea rift implying that the local stresses within the volcanic edifice are decoupled from the regional stress field

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

dry deposition of trace elements to the western north atlantic 1 data for al fe na sb se v and zn in aerosol particles from bermuda are used in combination with parameterized dry deposition velocities to investigate trace element recycling on atmospheric sea salt during july and august which are in the high dust season 10 of the monthly mean aerosol na can be ascribed to crustal sources rather than sea salt but in general the contribution of mineral dust to na dry deposition is small 1 relative to that from sea salt in fall and winter 10 to 20 of the aerosol al a commonly used indicator of mineral dust is attributable to recycled sea salt but the dust fluxes then are small and longer term averages show a recycling effect of only 1 to 5 on dry deposition the percentage of recycled fe appears to be even less than for al noncrustal non sea salt nc nss sources account for 70 of the aerosol sb se v and zn but differences in the dry deposition velocities for three particle types strongly affect their air sea exchange dust can account for more than half of the new dry deposition inputs of v and zn while the amounts of sb and se recycled on sea spray approach or exceed their new inputs from dust and the nss nc sources

iron isotope fractionation during leaching of granite and basalt by hydrochloric and oxalic acids abstract transport of iron fe within hydrothermal and soil environments involves the transferral into aqueous solutions by leaching of complex polyminerallic rocks understanding the isotope fractionation mechanisms during this process is key for any application of the fe isotope system to biogeochemical studies here we reacted biotite granite and tholeiite basalt with 0 5 m hydrochloric acid and 5 mm oxalic acid solutions at ambient temperature solution aliquots were recovered over a seven day period and analysed for major and trace element concentrations and fe isotopic compositions in all experiments fe initially released into solution was isotopically lighter with 56fesolution rock as low as 1 80 in the granite hydrochloric acid system the oxalic acid experiments showed similar patterns but smaller fractionation in all experiments the 56fesolution rock reduced over time which would be in line with the formation of a leached layer as proposed before brantley s l liermann l j guynn r l anbar a icopini g a and barling j 2004 fe isotopic fractionation during mineral dissolution with and without bacteria geochim cosmochim acta 68 15 3189 3204 granite and basalts reacting with hydrochloric acid reached apparent steady state values of 0 60 0 15 and 0 40 0 20 respectively whilst experimental values with oxalic acid were 1 0 0 15 and 0 50 0 15 during the granite experiments alteration of biotite to chlorite followed by dissolution of chlorite were likely the dominant processes whilst in the basalt experiments dissolution of pigeonite was likely the principal source of fe variations in ph during the hydrochloric acid experiments were minimal remaining below 0 5 at all times in oxalic acid solutions the ph increased to over 4 leading likely to precipitation of secondary minerals and adsorption co precipitation of fe onto mineral surfaces these processes could contribute to the greater fractionation observed in the final stages of the oxalic acid experiments our results highlight the importance of mineralogy and fluid composition on the fe isotope systematics during weathering the fractionation processes identified for granites and basalts are in line with those inferred from field observations in soils sediments groundwater and hydrothermal deposits and from laboratory studies of single mineral leaching

caldera collapse during the 2000 eruption of miyakejima volcano japan a collapsed caldera 1 6 km in diameter and 450 m in depth was formed at the summit of miyakejima volcano during the 2000 eruption the collapsed caldera appeared on 8 july with a minor phreatic eruption 12 days after seismic activity and magma intrusion occurred northwest of the volcano growth of the caldera took from 8 july to the middle of august with seismic swarms associated with the continuous intrusion of magma northwest of the volcano the growth rate of the caldera was about 1 4 107 m3 day and the final volume of the collapsed caldera was about 6 108 m3 major phreatomagmatic eruptions produced a total of about 1 6 1010 kg 1 1 107 m3 of volcanic ash after caldera growth the caldera structure and the nature of the eruptive materials of the first collapse on 8 july suggest that the surface subsidence was caused by the upward migration of a steam filled cavity with stoping of the roof rock above the magma reservoir the diameter of the stoping column was estimated to be 600 700 m from circumferential faults that developed in the caldera floor and the collapse of the caldera wall enlarged the diameter of the caldera to 1 6 km the total volume of the caldera and the horizontal diameter of the stoping column gave a subsidence of the caldera floor of 1 6 2 1 km

temporal monitoring of subglacial volcanoes with tandem x application to the 2014 2015 eruption within the barðarbunga volcanic system iceland on august 29 2014 a lava eruption commenced in the holuhraun plain north east of the bar arbunga caldera in iceland the eruption ended on february 27 2015 thus lasting for a period of about 6 months during these months the magma chamber below the caldera gradually deflated feeding the eruption and causing the rare event of a slow caldera collapse in this scenario tandem x remote sensing data are of particular interest by producing medium high resolution and accurate elevation models of the caldera it is possible to evaluate volume losses and topographical changes to increase the knowledge about the ongoing activity in particular five tandem x bistatic acquisitions have been commanded between august 01 2014 and november 08 2014 two of them before the volcanic eruption and three of them during the event additionally to fully cover the volcanic activity the lava field 48 km north east of the caldera has also been monitored in the first part of the paper the expected elevation accuracy is studied on two levels absolute and relative height accuracies are analyzed by inspecting the x band signal propagation into snow and by investigating the impact of the main geometrical system parameters and the local geomorphology in the second part of the paper the analysis is applied to the bar arbunga volcanic system including a validation performed using complementary altimeter data the main geophysical outcome is the accurate temporal height tracking of the entire caldera and the glacial volcanic system the measured volume loss at the caldera location is about 1 billion cubic meters in two months with an average rate of subsidence of nearly 50 cm day these numbers confirm other independent sources and can be compared to lava volume measurements finally the last segment of the dyke that propagated from the bar arbunga caldera to the holuhraun lava field is mapped and a graben structure with a width of up to 1 km and a sinking of a few meters is reported

the vertical distribution of iron stable isotopes in the north atlantic near bermuda seawater dissolved iron isotope ratios 56 fe have been measured in the north atlantic near bermuda in a full depth profile seawater dissolved 56 fe is isotopically heavy compared to crustal values throughout the water column 56 fe irmm 014 0 30 to 0 71 iron isotope ratios are relatively homogenous in the upper water column between 0 30 to 0 45 above 1500 m and 56 fe increases below this to a maximum of 0 71 at 2500 m decreasing again to 0 35 at 4200 m the 56 fe profile is very different from the iron concentration profile in the upper water column fe is variable while 56 fe is relatively constant and in the deeper water column 56 fe varies while fe remains relatively constant the 56 fe profile is also not well correlated with other hydrographic tracers in the north atlantic such as temperature salinity or the concentrations of oxygen phosphate silica and cfc 11 the dissimilarity between 56 fe profiles and profiles of fe and other hydrographic tracers shows that fe isotope ratios provide a unique sort of information about ocean chemistry and they suggest that fe isotopes may therefore be a valuable new tool for tracing the global sources sinks and biogeochemical cycling of fe

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

penetration depths inferred from interferometric volume decorrelation observed over the greenland ice sheet radar interferometry provides a novel way to study the subsurface of glaciers interferometric correlation since the two complex images that comprise the interferogram have slightly different incidence angles at each point on the ground a decorrelating phase noise with statistics related to the scattering medium is present in the interferogram the amount of surface decorrelation is increased by volume scatter the larger the vertical extent of the scatterers contributing to the radar echo the greater the decorrelation will be by modeling this effect the authors can estimate radio wave penetration depths within the upper layers of the glacier or ice sheet observations of the greenland ice sheet using ers data yield penetration depths one way 1 e point for power that range from 12 to 35 m due to the contribution of volume scatter the critical interferometer baseline is decreased and the authors find for the greenland data the baseline must be restricted to be less than 300 m the authors also compare penetration depths measured within the dry snow zone with those found in the percolation zone and coastal areas they find that as expected the rocky coastal areas evidence minimal penetration interestingly the penetration depths that the authors measure in the percolation zone spl sim 23 m indicate a large degree of volume scatter which is contrary to earlier results that found the scattering in the percolation zone dominated by structures in the first few meters this discrepancy may be due to unmodeled scattering behavior or the radar return may indeed include significant contributions from scatterers far beneath the surface

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change

surface movements of emplaced lava flows measured by synthetic aperture radar interferometry lava flows continue to move after they have been emplaced by flow mechanisms this movement is largely vertical and can be detected using differential synthetic aperture radar sar interferometry there are three main components to this motion 1 movement of surface scatterers resulting in radar phase decorrelation 2 measurable subsidence of the flow surface due to thermal contraction and clast repacking and 3 time dependent depression of the flow substrate these effects act in proportion to the thickness of the lava flow and decay with time although there is a time lag before the third component becomes significant we explore these effects using sar data from the ers satellites over the etna volcano sicily phase decorrelation on young thick a a lava flows persists for a few years and probably results from surface block rotations during flow contraction maximum measured subsidence rates of the 1991 1993 lava flow over a period of 70 days are about 0 7 mm day 1 but are potentially greater in areas of data decorrelation these rates fall to 2 7 10 2 mm day 1 after about 20 years in flows about 50 m thick sooner for thinner flows comparison with measured subsidence rates on kilauean lava lakes suggests that thermal contraction only accounts for about one third of the observed subsidence the remaining motion is thought to come from surface clast repacking during cooling and from creep mechanisms in the flow substrate measurements of postemplacement surface movement provide new constraints on the thermomechanical properties of lava flows and have cautionary implications for the interpretation of interferometric sar data of volcanoes 2001 american geophysical union

the effect of inflation on the morphology derived rheological parameters of lava flows and its implications for interpreting remote sensing data a case study on the 2014 2015 eruption at holuhraun iceland abstract morphology derived lava flow rheology is a frequently used tool in volcanology and planetary science to determine rheological parameters and deduce the composition of lavas on terrestrial planets and their moons these calculations are usually based on physical equations incorporating 1 lava flow driving forces gravity slope and flow rate and 2 morphological data such as lava flow geometry flow width height or shape of the flow outline all available methods assume that no geometrical changes occur after emplacement and that the measured flow geometry reflects the lava s apparent viscosity and or yield strength during emplacement it is however well established from terrestrial examples that lava flows may inflate significantly after the cessation of flow advance this inflation affects in turn the width to height ratio upon which the rheological estimates are based and thus must result in uncertainties in the determination of flow rheology as the flow height is one of the key parameters in the morphology based deduction of flow properties previous studies have recognized this issue but to date no assessment of the magnitude of this error has been presented this is likely due to a lack of digital elevation models dems at sufficiently high spatial and temporal resolution the 2014 15 holuhraun eruption in central iceland represents one of the best monitored large volume 1 5 km3 lava flow fields 85 km2 to date an abundance of scientific field and remote sensing data were collected during its emplacement moreover inflation plays a key role in the emplacement dynamics of the late stage of the lava field here we use a time series of high resolution dems acquired by the tandem x satellite mission prior during and after the eruption to evaluate the error associated with the most common methods of deriving lava flow rheology from morphological parameters used in planetary science we can distinguish two dominant processes as sources of error in the determination of lava flow rheology from morphology 1 wholesale inflation of lava channels and 2 post halting inflation of individual lava toes these result in a 2 4 to 17 fold overestimation of apparent viscosity and a 0 7 to 2 4 fold overestimation of yield strength when applied in planetary sciences this overestimation in rheological parameters translates directly to an overestimation of the respective lavas silica content we conclude that although qualitatively informative morphological analysis is insufficient to discern lava rheology and composition instead in situ analysis together with high resolution remote sensing data is needed to properly constrain the compositions involved in planetary volcanism