lava flow identification and aging by means of lidar intensity mount etna case 1 an application of light detection and ranging lidar intensity for the identification and mapping of different lava flows from the mount etna italy active volcano is described in september 2004 an airborne lidar survey was flown over summit sectors of mount etna the information derived from lidar intensity values was used to compare the lava flows with respect to their age of emplacement analyzed lava flows vary in age between those dating prior to a d 1610 and those active during the survey 2004 2005 eruptions the target emitter distance as well as surface roughness and texture at the lidar footprint scale is the main parameter controlling the intensity response of lava flows variations in the roughness and texture of surfaces at a meter scale result from two main processes initial lava cooling and subsequent surface weathering both lead to variations in the original surface roughness of the flow in summary 1 initially from the time of emplacement the lidar intensity of lava flow surfaces decreases and 2 about 6 years after emplacement the lidar intensity of lava surfaces starts to increase with the age of flows lidar capability in terms of geometric accuracy of 1 m in plan position and less than 1 m in elevation and spectral lidar intensity depends on surface reflection at 1 064 m information can thus be effectively used to map lava flows and to define a relative chronology of lava emplacement

terrestrial laser scanning of rock slope instabilities this manuscript presents a review on the application of a remote sensing technique terrestrial laser scanning tls to a well known topic rock slope characterization and monitoring although the number of publications on the use of tls in rock slope studies has rapidly increased in the last 5 10 years little effort has been made to review the key developments establish a code of best practice and unify future research approaches the acquisition of dense 3d terrain information with high accuracy high data acquisition speed and increasingly efficient post processing workflows is helping to better quantify key parameters of rock slope instabilities across spatial and temporal scales ranging from cubic decimetres to millions of cubic metres and from hours to years respectively key insights into the use of tls in rock slope investigations include a the capability of remotely obtaining the orientation of slope discontinuities which constitutes a great step forward in rock mechanics b the possibility to monitor rock slopes which allows not only the accurate quantification of rockfall rates across wide areas but also the spatio temporal modelling of rock slope deformation with an unprecedented level of detail studying rock slopes using tls presents a series of key challenges from accounting for the fractal character of rock surface to detecting the precursory deformation that may help in the future prediction of rock failures further investigation on the development of new algorithms for point cloud filtering segmentation feature extraction deformation tracking and change detection will significantly improve our understanding on how rock slopes behave and evolve perspectives include the use of new 3d sensing devices and the adaptation of techniques and methods recently developed in other disciplines as robotics and 3d computer vision to rock slope instabilities research

identification of structural controls in an active lava dome with high resolution dems volcan de colima mexico monitoring the topography of active lava domes is critical for detecting changes that may trigger or influence collapse or explosive activity internal dome structure and conditions are more difficult to elucidate but also play vital roles here we describe the exposure following an explosion of significant scarps in the active dome at volcan de colima mexico that are interpreted as evidence of brittle failure planes and a complex internal dome morphology in the first use of automated 3d computer vision reconstruction techniques structure from motion and multi view stereo sfm mvs on an active volcanic dome we derive high resolution surface models from oblique and archive photographs taken with a consumer camera the resulting 3d models were geo referenced using features identified in a web sourced orthoimage no ground based measurements were required in december 2010 the dome 2 14 106 m3 had a flat upper surface reflecting an overall ductile emplacement regime between then and may 2011 a period of low explosivity was accompanied by a small volume loss 0 4 105 m3 and arcuate steps appeared in the dome surface suggesting the presence of localized planes of weakness the complex array of summit scarps was exposed following a significant explosion in june 2011 and is interpreted to be the surface expression of fault planes in the dome the 1 m resolution dems indicated that the region of greatest volume loss was not coincident with the assumed location of the conduit and that heterogeneity within the dome may have been important during the june explosion

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

another look at downslope windstorms part i the development of analogs to supercritical flow in an infinitely deep continuously stratified fluid abstract numerical simulations are conducted to examine the role played by different amplification mechanisms in the development of large amplitude mountain waves it is shown that when the static stability has a two layer structure the nonlinear response can differ significantly from the solution to the equivalent linear problem when the parameter nh u is as small as 0 3 in the cases where the nonlinear waves are much larger than their linear counterparts the highest stability is found in the lower layer and the flow resembles a hydraulic jump simulations of the 11 january 1972 boulder windstorm are presented which suggest that the transition to supercritical flow forced by the presence of a low level inversion plays an essential role in triggering the windstorm the similarities between breaking waves and nonbreaking waves which undergo a transition to supercritical flow are discussed

the horizontal momentum balance in the marine atmospheric boundary layer during code 2 abstract the horizontal momentum balance in the marine atmospheric boundary layer during the coastal ocean dynamics experiment code is analyzed using meteorological data from an array of surface moorings previous studies have indicated the presence of orographically generated mesoscale features that are induced by strong southward flow around point arena the present analysis demonstrates that during periods of strong southward flow the cross shore momentum equation is dominated by a balance between the ageostrophic acceleration associated with the flow curvature around point arena and the cross shore pressure gradient while the along shore momentum equation is dominated by a balance between vertical stress divergence and alongshore pressure gradient these balances are consistent with results from a shallow water model of the marine layer the calculations provide evidence for orographic modification of the horizontal structure of the boundary layer under a broader range of southward flow conditio

the emplacement of the active lava flow at sinabung volcano sumatra indonesia documented by structure from motion photogrammetry abstract an effusive eruption at sinabung volcano in indonesia began in december 2013 we use structure from motion sfm photogrammetric techniques to create digital elevation models dems of the active lava flow we build dems from photographs taken during two separate time periods and from two separate low cost handheld cameras and compare them with a pre eruption dem to assess the quality and accuracy of photogrammetric dems created using different cameras calculate flow volume and long term average effusion rate and document changes in flow morphology on september 22nd 2014 the lava flow was 2 9 km long and had a volume of 1 03 0 14 108 m3 leading to an estimated time averaged discharge rate of 4 8 0 6 m3 s 1 differencing the photogrammetric dems shows that during the two week field campaign topographic changes of the flow occurred in zones along the flow front and on the upper flank a finding supported by relatively high temperatures in corresponding thermal images the deformation can be explained by active advance at the flow front and development of instabilities and collapse on the upper flanks large pyroclastic density currents associated with gravitational collapse of upper flank instabilities in october 2014 and june 2015 were caused by lava growing over ridges that had initially confined the flow to a pre existing channel this work demonstrates the ability of sfm photogrammetry to measure or identify the lava flow volume time averaged discharge rate flow emplacement rate and style as well as the development of gravitational instabilities our results show the potential of sfm photogrammetry as a cost and time effective method of repeatedly measuring active volcanic features and monitoring hazards at sinabung and during similar eruptions

studying monogenetic volcanoes with a terrestrial laser scanner case study at croscat volcano garrotxa volcanic field spain erosional processes natural or anthropogenic may partly destroy the relatively small sized volcanic edifices characteristic of monogenetic volcanic zones leaving their internal structure well exposed nevertheless the study of these outcrops may be extremely challenging due to restricted accessibility or safety issues digital representations of the outcrop surface have been lately used to overcome such difficulties data acquired with terrestrial laser scanning instruments using light detection and ranging technology enables the construction of such digital outcrops the obtained high precision 3 d terrain models are of greater coverage and accuracy than conventional methods and when taken at different times allow description of geological processes in time and space despite its intrinsic advantages and the proven satisfactory results this technique has been little applied in volcanology related studies here we want to introduce it to the volcanological community together with a new and user friendly digital outcrop analysis methodology for inexperienced users this tool may be useful not only for volcano monitoring purposes but also to describe the internal structure of exposed volcanic edifices or to estimate outcrop erosion rates that may be helpful in terms of hazard assessment or preservation of volcanic landscapes we apply it to the croscat volcano a monogenetic cone in the la garrotxa volcanic field catalan volcanic zone ne spain quarrying of which leads to a perfect view of its interior but restricts access to its uppermost parts croscat is additionally one of the most emblematic symbols of the la garrotxa volcanic field natural park and its preservation is a main target of the park administration

lidar derived morphology of the 1993 lascar pyroclastic flow deposits and implication for flow dynamics and rheology abstract pumice flows are potentially destructive volcanic events that derive from eruption column collapse and whose dynamics are poorly understood the challenges in studying these flows include the lack of constraints on the dynamics kinematics and initial conditions that control their emplacement we present a morphological study of the distal deposits lobes of the pumice flows resulting from the 1993 eruption at lascar chile the surface geometry of the lobes was measured in detail using a lidar device which allowed for detailed characterisation of their morphology consisting of central channel and lateral levees and terminal frontal snout in particular we find that the ratio of channel levee height as a function of the ratio of the distance between levees total width of the lobe has a characteristic curve for these pumice flow lobes our analysis of several of the lascar pumice lobe deposits south east sector identified several dimensionless groups of the available parameters which when compared against published results from both experimental and numerical investigations allowed us to constrain crucial kinematic and dynamic information on the terminal phase of the pumice flows notably we estimate the velocity of the terminal phase of pumice flows to be 5 10 m s froude numbers of 1 5 2 are comparable with values found for experimental granular flows height width aspect ratios for the levee channel section of the pumice lobes are similar to those for experimental flows although these same aspect ratios for the snout are much larger for the natural deposits than their small scale analogues finally we discuss the possible emplacement dynamics of the terminal lascar 1993 pumice flows a pseudo reynolds number based on the velocity estimation is found to be up to 100 times larger for the pumice flows than experimental scale flows this suggests that the flow retarding frictional forces for large scale flows are relatively unimportant compared to flows at smaller scales mechanical effects such as fluidisation mobilisation of material lying on the slopes over which they propagate and lubrication due to polydispersivity could provide an explanation for their ability to propagate on shallow slopes 6 11

the transition from summit to flank activity at mt etna sicily italy inferences from the petrology of products erupted in 2007 2009 abstract mt etna is an active basaltic volcano where both flank and summit eruptions take place in recent decades the south east summit crater sec has in particular been characterized by episodic eruptions consisting of recurrent lava fountains associated with lava flow emissions and lasting from a few weeks to months recent volcanic activity shows that if there is a transition from an episodic summit eruption to a flank eruption then this usually takes place while the last paroxysm of the episodic eruption is still underway by contrast the 2007 08 episodic eruption at sec was followed by the 2008 09 flank activity which started three days after the conclusion of the last paroxysm coinciding with the strong earthquake m 7 9 in sichuan china whose perturbations were recorded by the monitoring network of mt etna we therefore investigated the transition from a summit episodic eruption at sec to flank activity utilizing a petrologic study of the products erupted from 2007 to 2009 integrated with literature data the compositional variability of the products may largely be explained by a mixing between an evolved magma stored in the sec reservoir and a more primitive magma which intrudes it in the studied period the most significant episodes of magma recharge occurred before the onset of the 2007 08 episodic eruption and during the 2008 09 flank activity more precisely before june 2008 according to previous studies the seven paroxysms of the 2007 08 episodic eruption at sec have been interpreted as resulting from the disruption of a foam layer at the top of the sec reservoir which was rebuilt before each subsequent episode the transition from the 2007 08 episodic eruption at sec to the 2008 09 flank activity was essentially triggered by the sichuan earthquake which caused a variation of dynamic stress it caused the volatile exolution the pressurization of sec stored magma and the consequent fracturing of the surrounding rocks where magma intruded to then be erupted during the 2008 09 flank activity

mesoscale simulation of supercritical subcritical and transcritical flow along coastal topography abstract a mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline initial froude number values are varied through alteration of marine inversion strength permitting examination of supercritical subcritical and transcritical flow regimes encountering several coastal configurations consistent with shallow water models sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends however significant flow response occurs in the stratified layer aloft which is unexplained by conventional shallow water theory the strongest flow acceleration occurs in the transcritical case while regardless of inversion strength the deformation of the isentropes aloft shows general structural similarity advection of horizontal momentum is an important component of the horizontal force balance a simulation having several coastline bends exhibits a detached oblique hydraulic jump upwind of a concave bend t

drone high resolution infrared imaging of the lusi mud eruption abstract the use of low cost hand held infrared ir thermal cameras based on uncooled micro bolometer detector arrays became more widespread during the recent years thermal cameras have the ability to estimate temperature values without contact and therefore can be used in conditions where targets are difficult or dangerous to reach such as volcanic eruptions since may 2006 the indonesian lusi mud eruption continues to spew boiling mud water aqueous vapour co2 ch4 and covers a surface of nearly 7 km2 here we performed surveys above and around the erupting crater using a specifically equipped remote controlled aerial vehicle drone despite the harsh logistics and the continuously varying gas concentrations we managed to collect ir images composing mosaics to estimate the crater zone spatial and temporal thermal variations as well as that in the surrounding regions in this manuscript we provide a a description of the main processes that affect and control the acquisition of ir images b an overview of still non disclosed physical model used by the thermal camera employed during our survey i e flir i7 ir c a method for capturing high resolution infrared images over an erupting clastic system d analysis and interpretation of the acquired data and scientific results the results show that it is possible to obtain good quality mosaics also in inaccessible areas such as erupting craters where fixed reference points are not constant and where the presence of ir attenuation factors introduce errors in terms of temperature estimates however the ir camera radiative transfer model based on lowtran model allows the control of only some of the parameters that affect the attenuation of the ir spectrum this results in obtained crater temperature estimates up to 20 lower than those measured with hand held thermometers providing however very important information about the thermal gradient and the potential radioactive absorption factors the imaged lusi vent thermal pattern suggests the presence of shallow convective chambers inside the caldera zone these are activated by the rise of boiling mud breccia that suddenly cools and sinks the thermal survey conducted on the dry mud region to the ne of the crater reveals temperatures matching with those measured directly on the field with a hand held thermometer here the presence of hot spot anomalies and colder circular features is consistent with the migration of deeper warm fluids along a faulted and fractured area and with widespread pools distribution

terrestrial laser scanning observations of geomorphic changes and varying lava lake levels at erebus volcano antarctica abstract a terrestrial laser scanning tls instrument was used to image the topography of the main crater at erebus volcano each december in 2008 2009 and 2010 our high spatial resolution tls scans provide unique insights into annual and decadal scale geomorphic evolution of the summit area when integrated with comparable data collected by an airborne instrument in 2001 we observe both a pattern of subsidence within the inner crater of the volcano and an 3 m per year drop in the lava lake level over the same time period that are suggestive of decreasing overpressure in an underlying magma reservoir we also scanned the active phonolite lava lake hosted within the inner crater and recorded rapid cyclic fluctuations in the level of the lake these were sporadically interrupted by minor explosions by bursting gas bubbles at the lake surface the tls data permit calculation of lake level rise and fall speeds and associated rates of volumetric change within the lake these new observations when considered with prior determinations of rates of lake surface motion and gas output are indicative of unsteady magma flow in the conduit and its associated variability in gas volume fraction

testing the utility of structure from motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly however proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion herein we compare terrestrial laser scanning tls and both unmanned aerial vehicle uav and ground photography gp structure from motion sfm derived topography we compare the cost effectiveness and accuracy of both sfm techniques to tls for erosion gully surveying in upland landscapes treating tls as a benchmark further we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre erosion surface soil loss estimates from uav and gp sfm reconstructions were comparable to those from tls whereby the slopes of the relationship between all three techniques were not significantly different from 1 1 line only for the tls to gp comparison was the intercept significantly different from zero showing that gp is more capable of measuring the volumes of very small erosion features in terms of cost effectiveness in data collection and processing time both uav and gp were comparable with the tls on a per site basis 13 4 and 8 2 person hours versus 13 4 for tls however gp was less suitable for surveying larger areas 127 person hours per ha 1 versus 4 5 for uav and 3 9 for tls annual repeat surveys using gp were capable of detecting mean vertical erosion change on peaty soils these first published estimates of whole gully erosion rates 0 077 m a 1 suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates which largely characterize wind and rainsplash erosion of gully walls copyright c 2017 john wiley sons ltd

geomorphology and structural development of the nested summit crater of lascar volcano studied with terrestrial laser scanner data and analogue modelling abstract many volcano summits host craters that are partially overlapping the formation of such nested craters has been commonly interpreted as vent migration here we present an additional mechanism that may explain the geometry of nested craters at volcanoes lascar volcano the most active volcano of the central volcanic zone in the chilean andes hosts ene wsw trending summit craters that are partially overlapping nested details on the evolution and interaction between the different craters remain unclear to create a robust dataset terrestrial laser scanner tls data were collected at the summit of lascar in 2013 the resulting topographic data set consisting of more than 15 million data points with centimetre sampling allows visualising almost the complete eastern edifice of the volcano s summit from the tls data a digital elevation model dem and a slope map were generated allowing us to create a lineament map and quantify the observed morphological and structural features to further improve our understanding of the processes responsible for the formation of the craters and geomorphology we designed sandbox analogue models results suggest that one of the craters is a parasite crater formed as a consequence of ongoing activity in the adjacent crater our data suggest that the nested craters have all been modified since the last major eruption in 1993 by near surface effects associated with cooling compaction and gravitational sliding of the crater floor infill as the active crater deepens the adjacent inactive crater extends and partially slumps towards the active one understanding the structural development of these nested craters is relevant for assessing potential future eruption sites thus making lascar a dynamic target for a detailed morphology study these findings may similarly be applied to other volcanoes where nested craters have developed

morphology of basaltic lava channels during the mt etna september 2004 eruption from airborne laser altimeter data 1 the morphological features of active lava channels acquired over mt etna by means of airborne laser altimeter data are presented the data were acquired on 16th september 2004 using an optech altm 3033 laser altimeter the flight height was about 2000 m above ground during the flight the lava erupted from the eastern part of the mt etna summit area flowed into the valle del bove the measured morphologic features are channel width wc flow width wf levee height hl flow thickness tf and channel depth dc the main lava flow shows a well developed channel with levees the average measured values for the morphologic features of this flow are wc 16 m wf 52 m hl 7 m tf 5 m and dc 2 m the wc parameter shows linear increase from about 7 m near the vent up to about 25 m close to the front 1600 m in length

insights into pāhoehoe lava emplacement using visible and thermal structure from motion photogrammetry we present the evolution over 3 months of a 2016 2017 p hoehoe flow at k lauea as it changed from a narrow sheet flow into a compound lava field fed by a stable system of tubes the portion of the flow located on k lauea s coastal plain was characterized using helicopter based visible and thermal structure from motion photogrammetry to construct a series of georeferenced digital surface models and thermal maps on eight different days results reveal key influences on the emplacement and evolution of such long lived p hoehoe flows this region of the flow grew by 12 10 6 m 3 with a near constant time average discharge rate of 1 2 2 7 m 3 s the development of two tube systems is captured and shows an initial nascent tube enhanced by a narrow topographic confinement which later inflated and created a topographic inversion that modulated the emplacement of a second flow lobe with its own tube system the analysis of breakouts at various stages of the field s life suggests that the evolution of the thermal and morphological properties of the flow surface reflect its maturity thermal properties of breakouts were used to expand the empirical relationship of breakout cooling to longer timescales this study contributes to the long term development and validation of more accurate predictive models for p hoehoe required during the management of long lasting lava flow crises in hawai i and elsewhere

lava channel roofing overflows breaches and switching insights from the 2008 2009 eruption of mt etna during long lived basaltic eruptions overflows from lava channels and breaching of channel levees are important processes in the development of extensive a lava flow fields short lived breaches result in inundation of areas adjacent to the main channel however if a breach remains open lava supply to the original flow front is significantly reduced and flow field widening is favoured over lengthening the development of channel breaches and overflows can therefore exert strong control over the overall flow field development but the processes that determine their location and frequency are currently poorly understood during the final month of the 2008 2009 eruption of mt etna sicily a remote time lapse camera was deployed to monitor events in a proximal region of a small ephemeral lava flow for over a period of 10 h the flow underwent changes in surface elevation and velocity repeated overflows of varying vigour and the construction of a channel roof a required prelude to lava tube formation quantitative interpretation of the image sequence was facilitated by a 3d model of the scene constructed using structure from motion computer vision techniques as surface activity waned during the roofing process overflow sites retreated up the flow towards the vent and eventually a new flow was initiated our observations and measurements indicate that flow surface stagnation and flow inflation propagated up flow at an effective rate of 6 m h 1 and that these processes rather than effusion rate variations were ultimately responsible for the most vigorous overflow events we discuss evidence for similar controls during levee breaching and channel switching events on much larger flows on etna such as during the 2001 eruption

vtfs project development of the lava flow simulation code lavasim with a model for three dimensional convection spreading and solidification 1 the lava flow simulation code lavasim has been developed to give accurate predictions of volcanic disasters and to support evacuation plans the code uses three dimensional analysis with free surface evaluation including boundary transport between the melt and the crust it is therefore applicable to various types of lava flows and flow behaviors such as flood basalts subaqueous lava flows and levee formation heat transfer between the lava and the ground air and water and between the melt and crust of the flow is calculated by using appropriate relations the code has been verified by applying it to actual lava flows and the simulation results have been compared with observations of the izu osima flows of 1986 the lava flow rate temperature and properties were assigned values based on data from existing literature the comparisons demonstrated the code s capability for prediction of inundated areas and maximum flow lengths the present code is expected to be useful for real time prediction during eruptions in addition to assessing volcanic hazards and designing protection structures for existing installations against possible future lava flows

review of earth science research using terrestrial laser scanning abstract the application of advanced remote sensing technologies including terrestrial laser scanning tls to the earth sciences has increased rapidly in the last two decades improving the spatial and temporal resolution of data terrestrial laser scanning units have evolved into a common tool in studies of spectral and structural geology seismology natural hazards geomorphology and glaciology special consideration of the advantages and limitations of tls in each of these fields is discussed in depth in the context of important work published in each field the workflow used in a tls survey is crucial to the success of the survey and field specific earth science workflows are therefore also discussed products based on tls data such as triangulated irregular networks tin and digital surface models dsm are commonplace tools throughout the earth sciences and the use of these tools to measure slip distributions fault geometries aeolian transport river bed morphologies and flows and other research problems is expanded on where appropriate the review concludes with a discussion of recent trends in tls instrument development and their potential impact on the use of tls in the earth sciences in the future

uav based remote sensing surveys of lava flow fields a case study from etna s 1974 channel fed lava flows during an eruption time scales of topographic change are fast and involve vertical and planimetric evolution of millimeters to meters as the event progresses repeat production of high spatial resolution terrain models of lava flow fields over time scales of a few hours is thus a high value capability in tracking the buildup of the deposit among the wide range of terrestrial and aerial methods available to collect such topographic data the use of an unmanned aerial vehicle uav as an acquisition platform together with structure from motion sfm photogrammetry has become especially useful this approach allows high frequency production of centimeter scale terrain models over kilometer scale areas including dangerous and inaccessible zones with low cost and minimal hazard to personnel this study presents the application of such an integrated uav sfm method to generate a high spatial resolution digital terrain model and orthomosaic of mount etna s january february 1974 lava flow field the sfm method applied to images acquired using a uav platform enabled the extraction of a very high spatial resolution 20 cm digital elevation model and the generation of a 3 cm orthomosaic covering an area of 1 35 km2 this spatial resolution enabled us to analyze the morphology of sub meter scale features such as folds blocks and cracks over kilometer scale areas the 3 cm orthomosaic allowed us to further push the analysis to centimeter scale grain size distribution of the lava surface using these data we define three types of crust structure and relate them to positions within a channel fed a flow system these crust structures are i flow parallel shear lines ii raft zones and iii folded zones flow parallel shear lines are found at the channel edges and are 2 m wide and 0 25 m deep zones running along the levee base and in which cracking is intense they result from intense shearing between the moving channel lava and the static levee lava in zones where initial levees are just beginning to form these subtle features are the only marker that delimits the moving lava from the stagnant marginal lava rafts generally form as the system changes from a stable to a transitional channel regime over this 170 m long zone the channel broadens from 8 to 70 m and rafts are characterized by topographically higher and poorly cracked areas surrounded by lower heavily cracked areas we interpret the rafts as forming due to breakup of crust zones previously moving in a coherent manner in the narrow proximal channel reach folded zones involve arcuate cross flow ridges with their apexes pointing down flow where ridges have relatively small clasts and depressions are of coarser grained breccia our folds have wavelengths of 10 m and amplitudes of 1 m are found towards the flow front down flow of the raft zones and are associated with piling up of lava behind a static or slowly moving flow front the very high spatial resolution topographic data available from uav sfm allow us to resolve surfaces where roughness has a vertical and horizontal scale of variation that is less than 1 m this is the case over p hoehoe and a flow surfaces and thus allows us to explore those new structures that are only apparent in the sub metric data moreover during future eruptions the possibility to acquire such information in near real time will allow a prompt analysis of developing lava flow fields and structures therein such as developing lava channel systems so as to contribute to timely hazard assessment modeling and projections

imaging the 2013 explosive crater excavation and new dome formation at volcan de colima with terrasar x time lapse cameras and modelling abstract the summit region of steep volcanoes hosting lava domes often displays rapid geomorphologic and structural changes which are important for monitoring the source region of hazards explosive crater excavation is often followed by new lava dome growth which is one of the most dynamic morphometric changes that may occur at volcanoes however details of these crater formations and the ensuing new dome growth remain poorly studied a common problem is the lack of observational data due to hazardous field access and the limited resolution of satellite remote sensing techniques this paper describes the destructive constructive crater activity at volcan de colima mexico which occurred between january and march 2013 the crater geometry and early dome formation were observed through a combination of high resolution terrasar x spotmode satellite radar images and permanently installed monitoring cameras this combined time lapse imagery was used to identify ring shaped gas emissions prior to the explosion and to distinguish between the sequential explosion and crater excavation stages which were followed by dome growth by means of particle image velocimetry the digital flow field is computed from consecutive camera images showing that vertical dome growth is dominant at the beginning the upward growth is found to grade into spreading and a lateral growth domain after approximately two months of gradually filling the excavated craters with new magma the dome overflows the western margin of the crater and develops into a flow that produces block and ash flow hazards we discuss and compare the observations to discrete element models allowing us to mimic the vertical and lateral growth history of the dome and to estimate the maximum strength of the bulk rock mass moreover our results allow a discussion on the controls of a critical dome height that may be reached prior to its gravitational spreading

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

the application of a long range laser scanner for monitoring volcanic activity on mount etna abstract there is a requirement for rapid remote monitoring of ground deformation of volcanoes especially during eruptions a long range reflector less laser scanning instrument manufactured by riegl laser measurement systems was used on mount etna in october 2000 and its potential for monitoring ground surface changes associated with volcanic activity was evaluated the 3dlm lr1 scanner system can measure distances up to 2 km with an accuracy of 25 mm in typical conditions measurement rates range from 1 point per second at 2 km to 4 points per second at 10 m the system also records reflective intensity and this proved useful in distinguishing between different types of volcanic material cloud and gas obscured some measurements but the scanning nature of the instrument coupled with effective data filtering software allowed robust digital terrain models to be created

what we can and cannot learn about earthquake sources from the spectra of seismic waves earthquake sources are commonly viewed as shear dislocations this imposes distinct limitations on what source parameters can be realistically determined from radiated shear wave spectra first the slip velocity on the fault is the real parameter that controls the strength of the high frequency radiation it can be directly determined from acceleration spectra by fitting their high frequency level second the relationship between corner frequency of the spectrum and the radius of the source is fundamentally unclear as a result the source dimensions cannot be accurately determined from the spectra such an estimate would be as accurate as any other informed guess third the stress drop only serves as a proxy for the source radius in the relationship between the radius and the corner frequency it thus cannot be reliably determined from the spectra the quantity usually obtained from the spectra and referred to as the stress drop is a poorly defined parameter that may bear little relevance to the actual stresses acting on faults this parameter has little meaning unless converted to the maximum slip velocity which is the only quantity that can be accurately determined from the spectra the typical value of stress drop of 100 bars established from the spectra of california events may imply that the typical slip velocities have been on the order of 0 5 m sec although it is more accurate to determine slip velocities directly from the spectra

pointcatcher software analysis of glacial time lapse photography and integration with multitemporal digital elevation models terrestrial time lapse photography offers insight into glacial processes through high spatial and temporal resolution imagery however oblique camera views complicate measurement in geographic coordinates and lead to reliance on specific imaging geometries or simplifying assumptions for calculating parameters such as ice velocity we develop a novel approach that integrates time lapse imagery with multi temporal digital elevation models to derive full 3d coordinates for natural features tracked throughout a monoscopic image sequence this enables daily independent measurement of horizontal ice flow and vertical ice melt velocities by combining two terrestrial laser scanner surveys with a 73 day sequence from solheimajokull iceland variations in horizontal ice velocity of 10 were identified over timescales of 25 days an overall surface elevation decrease of 3 0 m showed rate changes asynchronous with the horizontal velocity variations demonstrating a temporal disconnect between the processes of ice surface lowering and mechanisms of glacier movement our software pointcatcher is freely available for user friendly interactive processing of general time lapse sequences and includes monte carlo error analysis and uncertainty projection onto dem surfaces it is particularly suited for analysis of challenging oblique glacial imagery and we discuss good features to track both for correction of camera motion and for deriving ice velocities

generalized hydraulic solutions pertaining to severe downslope winds abstract nonlinear steady state solutions for stratified two layer flow over a ridge are found in parameter space these solutions lie between the interfacial case of long and the constant stratification case of smith the solutions predict the depth of the layer which will descend and accelerate qualitative agreement with bora and boulder observations is found

detecting the development of active lava flow fields with a very long range terrestrial laser scanner and thermal imagery regular topographic surveys of active lava flows could provide significant insight into the development of flow fields but data of sufficient accuracy spatial extent and repeat frequency to quantify the processes involved have yet to be acquired here we report results from the use of a new very long range terrestrial laser scanner tls on active lavas at mount etna sicily the scanner proved capable of providing useful topographic data from volcanic terrain at ranges up to 3500 m with laser returns from ash covered slopes as well as from lava despite very low effusion rates 1 m3s 1 topographic changes associated with the emplacement and inflation of new flows and the inflation of a tumulus were detected irregular data spacing resulting from oblique views makes the interpretation of laser derived digital elevation models alone difficult but fusing topographic data with thermal images allows active flow features to be clearly visualized

use of a portable topographic mapping millimetre wave radar at an active lava flow a ground based millimetre wave radar avtis all weather volcano topography imaging sensor has been developed for topographic monitoring the instrument is portable and capable of measurements over ranges up to 7 km through cloud and at night in april and may 2005 avtis was deployed at arenal volcano costa rica in order to determine topographic changes associated with the advance of a lava flow this is the first reported application of mm wave radar technology to the measurement of lava flux rates three topographic data sets of the flow were acquired from observation distances of 3 km over an eight day period during which the flow front was detected to have advanced 200 m topographic differences between the data sets indicated a flow thickness of 10 m and a dense rock equivalent lava flux of 0 20 0 08 m3s 1

supercritical marine layer flow along a smoothly varying coastline abstract a model for hydraulically supercritical atmospheric marine layer flow along a smoothly varying coastline is formulated and solved numerically the model is motivated by a recent comparison of code observations to a simple hydraulic theory which suggested the presence of an expansion fan and a compression jump downstream of topographic features the marine layer is modeled as a homogeneous rotating fluid layer decelerated by surface friction and forced by imposed upper level pressure gradients the equations are solved by a characteristic based gridpoint scheme the results indicate that the expansion fan is a robust feature that persists under most conditions in the present more realistic model but is dramatically altered in structure by the presence of friction while the jump may weaken rapidly offshore due mainly to offshore variations of the layer height upstream of the jump the agreement between observations and model predictions is good enough to suggest that a first order description of

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

modeling river bed morphology roughness and surface sedimentology using high resolution terrestrial laser scanning 1 recent advances in technology have revolutionized the acquisition of topographic data offering new perspectives on the structure and morphology of the earth s surface these developments have had a profound impact on the practice of river science creating a step change in the dimensionality resolution and precision of fluvial terrain models the emergence of hyperscale survey methods including structure from motion photogrammetry and terrestrial laser scanning tls now presents the opportunity to acquire 3 d point cloud data that capture grain scale detail over reach scale extents translating these data into geomorphologically relevant products is however not straightforward unlike traditional survey methods tls acquires observations rapidly and automatically but unselectively this results in considerable noise associated with backscatter from vegetation and other artifacts moreover the large data volumes are difficult to visualize require very high capacity storage and are not incorporated readily into gis and simulation models in this paper we analyze the geomorphological integrity of multiscale terrain models rendered from a tls survey of the braided river feshie scotland these raster terrain models are generated using a new computationally efficient geospatial toolkit the topographic point cloud analysis toolkit topcat this performs an intelligent decimation of point cloud data into a set of 2 5 d terrain models that retain information on the high frequency subgrid topography as the moments of the locally detrended elevation distribution the results quantify the degree of terrain generalization inherent in conventional fluvial dems and illustrate how subgrid topographic statistics can be used to map the spatial pattern of particle size grain roughness and sedimentary facies at the reach scale

rapid updating and improvement of airborne lidar dems through ground based sfm 3 d modeling of volcanic features we present a workflow to create scale georeference and integrate digital elevation models dems created using open source structure from motion sfm multiview stereo mvs software into existing dems as derived from the light detection and ranging data in the presented cases the workflow also maps the root mean square error between the base dem and the sfm surface model this allows dem creation from field based surveys using consumer grade digital cameras with open source and custom built software we employ this workflow on three examples of different scales and morphology 1 a scoria cone on mt etna 2 a lava channel on mauna ulu k lauea and 3 a flank collapse scar on mt etna this represents a new approach for rapid low cost construction and updating of existing dems at high temporal and spatial resolutions and for areas of up to several thousand square meters we assess the self consistency of the method by comparison of dems of the same features created from independent data sets acquired on the same day and from the same vantage points we further evaluate the effect of grid cell size on the reconstruction error this method uses existing dems as a georeferencing tool and can therefore be used in limited access and potentially hazardous areas as it no longer relies exclusively on control targets on the ground

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales

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