Model For Lava Flows Research Articles

Lava flow hazard at Fogo Volcano, Cabo Verde, before and after the 2014–2015 eruption

Abstract. Lava flow simulations help to better understand volcanic hazards and may assist emergency preparedness at active volcanoes. We demonstrate that at Fogo Volcano, Cabo Verde, such simulations can explain the 2014–2015 lava flow crisis and therefore provide a valuable base to better prepare for the next inevitable eruption. We conducted topographic mapping in the field and a satellite-based remote sensing analysis. We produced the first topographic model of the 2014–2015 lava flow from combined terrestrial laser scanner (TLS) and photogrammetric data. This high-resolution topographic information facilitates lava flow volume estimates of 43.7 ± 5.2 × 106 m3 from the vertical difference between pre- and posteruptive topographies. Both the pre-eruptive and updated digital elevation models (DEMs) serve as the fundamental input data for lava flow simulations using the well-established DOWNFLOW algorithm. Based on thousands of simulations, we assess the lava flow hazard before and after the 2014–2015 eruption. We find that, although the lava flow hazard has changed significantly, it remains high at the locations of two villages that were destroyed during this eruption. This result is of particular importance as villagers have already started to rebuild the settlements. We also analysed satellite radar imagery acquired by the German TerraSAR-X (TSX) satellite to map lava flow emplacement over time. We obtain the lava flow boundaries every 6 to 11 days during the eruption, which assists the interpretation and evaluation of the lava flow model performance. Our results highlight the fact that lava flow hazards change as a result of modifications of the local topography due to lava flow emplacement. This implies the need for up-to-date topographic information in order to assess lava flow hazards. We also emphasize that areas that were once overrun by lava flows are not necessarily safer, even if local lava flow thicknesses exceed the average lava flow thickness. Our observations will be important for the next eruption of Fogo Volcano and have implications for future lava flow crises and disaster response efforts at basaltic volcanoes elsewhere in the world.

Conclusion: recommendations and findings of the RED SEED working group

Abstract RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters, and combines stakeholders from the remote sensing, modelling and response communities with experience in tracking volcanic effusive events. The group first met during a three day-long workshop held in Clermont Ferrand (France) between 28 and 30 May 2013. During each day, presentations were given reviewing the state of the art in terms of (a) volcano hot spot detection and parameterization, (b) operational satellite-based hot spot detection systems, (c) lava flow modelling and (d) response protocols during effusive crises. At the end of each presentation set, the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors, modellers and responders during an effusive crisis. The results of collating the final reports, and follow-up discussions that have been on-going since the workshop, are given here. We can reduce our discussions to four main findings. (1) Hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min. (2) Spectral radiance metrics can also be provided with high degrees of confidence. However, if we are to achieve a truly global system, more local receiving stations need to be installed with hot spot detection and data processing modules running on-site and in real time. (3) Models are operational, but need real-time input of reliable time-averaged discharge rate data and regular updates of digital elevation models if they are to be effective; the latter can be provided by the radar/photogrammetry community. (4) Information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities. All of this requires a sophisticated and centralized data collection, distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust. While the next chapter carries out an exercise to explore the viability of the last point, the detailed recommendations behind these findings are detailed here.

SCIARA: cellular automata lava flow modelling and applications in hazard prediction and mitigation

Abstract The use of thematic volcanic hazard maps is essential for policy managers and administrators in land use planning and to determine the best form of action during emergencies. In particular, hazard maps are a key tool in emergency management and are used to describe the threat expected at a certain location in the event of future eruptions. We applied the latest version of the SCIARA lava flow cellular automata model using parallel computing through general purpose graphics processing units technology to derive lava flow hazard maps for Mt Etna, Sicily. The methodology relies on an accurate analysis of the past behaviour of the volcano and is appropriate for land use planning and civil defence applications.

Lava flow mapping and volume calculations for the 2012–2013 Tolbachik, Kamchatka, fissure eruption using bistatic TanDEM-X InSAR

The bistatic acquisition mode of the German TanDEM-X radar satellite mission provides a reliable source for measuring morphological changes associated with volcanic activity. We present the use of this system to measure key lava flow parameters including thickness, volume, runout, and flow extent by using two TanDEM-X data pairs to generate digital elevation models (DEMs) prior to and immediately following the 2012–2013 eruption of Tolbachik Volcano, Kamchatka. Morphometric parameters and areal distribution of the new lava flow field are determined using a cell-by-cell elevation difference between the two DEMs. A total flow volume of 0.53 ± 0.07 km3, a mean flow thickness of 14.5 m, and a modal thickness of 7.8 m are calculated. We use these calculated flow parameters as input to a volume-limited lava flow emplacement model. Model simulations are able to reproduce the SW portion of the 2012–2013 Tolbachik lava flow using a 75-m Shuttle Radar Topography Mission (SRTM) DEM and the 15-m TanDEM-X derived DEM, with goodness-of-fit measures of 56.3 and 59.6 %, respectively, based on the Jaccard similarity coefficient. The flow simulation done using SRTM data underestimates the observed 14.4 km flow runout by over 3 km, while the simulation with TanDEM-X data overestimates flow runout by about 1.5 km. Performance of the lava flow modeling algorithm is highly dependent on the modal lava thickness, highlighting the importance of using TanDEM-X DEMs to provide precise lava flow measurements in order to constrain input parameters for numerical modeling of lava flows.

Quantifying lava flow hazards in response to effusive eruption

The integration of satellite data and modeling represents a step toward the next generation of quantitative hazard assessment in response to effusive volcano eruption onset. Satellite-based thermal remote sensing of hotspots related to effusive activity can effectively provide a variety of products suited to timing, locating, and tracking the radiant character of lava flows. Hotspots show the location and occurrence of eruptive events (vents). Discharge rate estimates may indicate the current intensity (effusion rate) and potential magnitude (volume). High-spatial-resolution multispectral satellite data can complement field observations for monitoring the front position (length) and extension of flows (area). Physics-based models driven, or validated, by satellite-derived parameters are now capable of fast and accurate forecast of lava flow inundation scenarios (hazard). Here, we demonstrate the potential of the integrated application of satellite remote-sensing techniques and lava flow models by using a retrospective analysis of the 2004–2005 effusive eruption at Mount Etna in Italy. The lava flow hazard was assessed by using the HOTSAT volcano hotspot detection system, which works with satellite thermal infrared data, and the MAGFLOW lava flow emplacement model, which is able to relate the flow evolution to eruption conditions at the vent. We used HOTSAT to analyze Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and InfraRed Imager (SEVIRI) data to output hotspot location, lava thermal flux, and effusion rate estimation. This output was used to drive the MAGFLOW simulations of lava flow paths and to continuously update flow simulations. We also show how Landsat-7 Enhanced Thematic Mapper+ (ETM+) and Earth Observing 1 ( EO-1 ) Advanced Land Imager (ALI) images complement the field observations to track the flow front position in time and add valuable data on lava flow advancement with which to validate the numerical simulations. Such integration at last makes timely forecasts of lava flow hazards during effusive crises possible at the great majority of volcanoes for which no monitoring exists.

Testing a geographical information system for damage and evacuation assessment during an effusive volcanic crisis

Abstract Using two hypothetical effusive events in the Chaîne des Puys (Auvergne, France), we tested two geographical information systems (GISs) set up to allow loss assessment during an effusive crisis. The first was a local system that drew on all immediately available data for population, land use, communications, utility and building type. The second was an experimental add-on to the Global Disaster Alert and Coordination System (GDACS) global warning system maintained by the Joint Research Centre (JRC) that draws information from open-access global data. After defining lava-flow model source terms (vent location, effusion rate, lava chemistry, temperature, crystallinity and vesicularity), we ran all available lava-flow emplacement models to produce a projection for the likelihood of impact for all pixels within the GIS. Next, inundation maps and damage reports for impacted zones were produced, with those produced by both the local system and by GDACS being in good agreement. The exercise identified several shortcomings of the systems, but also indicated that the generation of a GDACS-type global response system for effusive crises that uses rapid-response model projections for lava inundation driven by real-time satellite hotspot detection – and open-access datasets – is within the current capabilities of the community.

Benchmarking lava-flow models

Abstract Prediction of the emplacement of volcanic mass flows (lava flows, pyroclastic density currents, debris avalanches and debris flows) is required for hazard and risk assessment, and for the planning of risk-mitigation measures. Numerical computer-based models now exist that are capable of approximating the motion of a given volume of volcanic material from its source to the deposition area. With these advances in technology, it is useful to compare the various codes in order to evaluate their respective suitability for real-time forecasting, risk preparedness and post-eruptive response. A ‘benchmark’ compares codes or methods, all aimed at simulating the same physical process using common initial and boundary conditions and outputs, but using different physical formulations, mathematical approaches and numerical techniques. We set up the basis for a future general benchmarking exercise on volcanic mass-flow models and, more specifically, establish a benchmark series for computational lava-flow modelling. We describe a set of benchmarks in this paper, and present a few sample results to demonstrate output analysis and code evaluation methodologies. The associated web-based communal facility for sharing test scenarios and results is also described.

Virtual tools for volcanic crisis management, and evacuation decision support: applications to El Chichón volcano (Chiapas, México)

Decision making regarding massive evacuation of a population threatened by a probable volcanic eruption is a major problem in crisis management. Such a decision is general on the number of people to be evacuated, available resources and infrastructure, quantity and quality of the escape routes and shelters, and the economic, social and political costs involved in the operation, coupled with the updated information provided by scientists about the forecast of future activity and probable eruption scenarios. Knowing time-lapse between the evacuation decision-making time and the time in which the evacuation is completed is another critical issue that must be carefully considered in densely populated areas. In such areas, it is really important to estimate in advance this time-lapse, as the forecast must be released with enough time to complete all the evacuation process before the destructive manifestations of the eruption begin. In this context, evacuation planning is a crucial component of emergency management. It is common for Emergency Plans to include pre-established strategies. However, an evacuation procedure should be flexible, depending on the above-mentioned timing, and on the decisions, evacuation schemes, environmental characteristics and other factors. In this work, several hazard models such as a lava flow model based on a Monte Carlo algorithm, a pyroclastic density current based on energy cone model, a semi-empirical inversion model to estimate the thickness of ash deposits, and all available information about the El Chion volcano have been used to obtain the area that should be evacuated in case of an eruption. Then, multiple evacuation strategies at El Chichon volcano have been designed, considering not only the characteristics of the eruption forecast, but also environmental factors (e.g., weather conditions) and social factors (e.g., tourism and farming seasons). The variable scale evacuation model has been used to estimate the evacuation time. In the paper, those virtual tools are briefly described as well as the information obtained from the drill of 2009. In addition to the optimization of evacuation under variable conditions and situations, one of the main objectives of this work is to provide a reliable estimation of the mitigation action time, for an Emergency Plan.

Numerical experiments on the dynamics of channelised lava flows at Mount Cameroon volcano with the FLOWGO thermo-rheological model

As for many other effusive volcanoes, Mount Cameroon (MC) is a volcano for which only limited information exists on lava flow properties and emplacement dynamics for recent eruptions. This study provides new quantitative constraints for rheological and dynamic characteristics of lava flow effusion for the 1982 and 2000 eruptive events, used to calibrate the FLOWGO thermo-rheological model for these lava flows. The FLOWGO 1-D physical model is used to simulate down-flow evolution of the geometry and rheology of channel-contained cooling-limited lava flows. Morphometric data from historical lava flows were acquired from the field, e.g. channel geometry, levee and background slope, in order to estimate lava yield strength, velocity and effusion rate. Lava density and viscosity were also estimated from compositional data and laboratory methods. To account for uncertainty in the input rheological and geometrical data, three end-member scenarios were used to bracket the potential range in lava channel initial dimension, initial lava temperature and phenocryst content. For each of these scenarios, two crustal growth models were used: one assuming strong insulation due to lava flow surface crusting, the other a much lower crusting rate. Twelve numerical simulations were made per flow and the results were compared against the channel geometry, microlite content, yield strength and viscosity estimates from field and laboratory investigations. Best-fit models where obtained for both the 1982 and 2000 lava flows using a low rate of surface crusting, high initial temperature and low phenocryst content. Model-predicted lengths were within 5% of the actual lengths. Modelled mean effusion rates for the 1982 (52–64m3s−1) and 2000 (10m3s−1) flows closely matched field data derived estimations (26–68 and 9.5m3s−1 respectively). FLOWGO model results are highly sensitive to initial channel dimensions, phenocryst content and the FLOWGO model is unable to reproduce the observed rapid near-vent increase in microlite content. Near-vent rapid cooling induced by lava degassing is yet to be fully documented and integrated into numerical lava flow models such as FLOWGO, but obtained results already provide valuable insights for lava flow hazard assessment at Mount Cameroon.

Mapping and modelling lava flow dynamics and hazards at mount Cameroon volcano

Destruction of human property and agro-allied plantations by lava flow invasion is a significant volcanic hazard at Mount Cameroon volcano (Cameroon), where reliable hazard and risk maps are required for risk mitigation. This thesis is dedicated to the study of lava flows at Mount Cameroon, a volcano situated in a densely populated region with over 450000 inhabitants on its flanks. Mount Cameroon (MC) is the largest (~ 4095 m a.s.l.) active continental volcano in West Africa based on its recorded historic eruptions for the 20th and 21st century (1909, 1922, 1925?, 1954, 1959, 1982, 1999 and 2000). This volcano is subject to a variety of hazards: volcanic eruptions, earthquakes and lahars. Although records of eruptions at MC are found back to 2500 BC, few of its eruptions have been documented. This is in great contrast to other volcanoes like Mount Etna whose documented eruption history dates back to more than 2500 years. Previous work carried out for eruptions resulting from MC mostly centred on its seismicity, tectonics, petrology and geochemistry. Recently, focus on lava flow studies at Mount Cameroon has shifted towards morphological and lava flow hazard assessment. This thesis is the first to assess lava flow hazard and risk at MC through a combination of a systematic field approach supplemented with remote sensing observation and lava flow modelling techniques. It illustrates the systematic use of a field-based approach to describe lava flow surface morphology for the 2000 lava flow field and structure to retrieve the flow’s deformation history. The 1982 lava flow field was also investigated for its channel geometry and its lava rheology. This information together with petrographic and channel geometrical data collected were used to model these flows with the FLOWGO model in a first phase. This model’s performance was evaluated based on its ability to reproduce the total length and the internal channel geometry observed for these lava channels. In the last part of this thesis, the spatial distribution of lava flow hazard was evaluated through the use of the VORIS stochastic model in combination to FLOWGO. Using a combination of free/low-cost multispectral datasets, pre-historical lava flows and lava flows from the last century were mapped at MC. This map showed that lava flows that issued at elevations of ~ 1500 m a.s.l. along the NE and SW flanks could represent a hazard for settlement and infrastructure. From MODVOLC data, direct eruption observation, seismic data, field observations and optical RS datasets, the 2000 eruption duration was estimated at ~ 52 days. Other facts revealed that at some places eruptions previously thought to have produced only pyroclastics emplaced an 850 m-long lava flow field. At some some sites aa lava was the dominant flow morphology while pahoehoe lava dominated at other sites. For this 2000 eruption, we realised that it was the slow-moving pahoehoe lava that covered a more extensive area and attained a longer length than the fast-moving aa lava flow. Calibrating the 1982 and the 2000 lava flows using FLOWGO produced satisfactory results for the former flow (1982) with slight mismatches for the latter (2000) flow. Lava flow hazard maps produced emphasised the vulnerability of coastal and the NE habitats from lava flow invasion from MC eruptions. The findings from this study presents the FLOWGO and VORIS models as useful tools to forecast/manage future eruptions from MC.

An emergent strategy for volcano hazard assessment: From thermal satellite monitoring to lava flow modeling

Spaceborne remote sensing techniques and numerical simulations have been combined in a web-GIS framework (LAV@HAZARD) to evaluate lava flow hazard in real time. By using the HOTSAT satellite thermal monitoring system to estimate time-varying TADR (time averaged discharge rate) and the MAGFLOW physics-based model to simulate lava flow paths, the LAV@HAZARD platform allows timely definition of parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. We used LAV@HAZARD during the 2008–2009 lava flow-forming eruption at Mt Etna (Sicily, Italy). We measured the temporal variation in thermal emission (up to four times per hour) during the entire duration of the eruption using SEVIRI and MODIS data. The time-series of radiative power allowed us to identify six diverse thermal phases each related to different dynamic volcanic processes and associated with different TADRs and lava flow emplacement conditions. Satellite-derived estimates of lava discharge rates were computed and integrated for the whole period of the eruption (almost 14months), showing that a lava volume of between 32 and 61million cubic meters was erupted of which about 2/3 was emplaced during the first 4months. These time-varying discharge rates were then used to drive MAGFLOW simulations to chart the spread of lava as a function of time. TADRs were sufficiently low (<30m3/s) that no lava flows were capable of flowing any great distance so that they did not pose a hazard to vulnerable (agricultural and urban) areas on the flanks of Etna.

Numerical simulation of lava flow using a GPU SPH model

A smoothed particle hydrodynamics (SPH) method for lava-flow modeling was implemented on a graphical processing unit (GPU) using the compute unified device architecture (CUDA) developed by NVIDIA. This resulted in speed-ups of up to two orders of magnitude. The three-dimensional model can simulate lava flow on a real topography with free-surface, non-Newtonian fluids, and with phase change. The entire SPH code has three main components, neighbor list construction, force computation, and integration of the equation of motion, and it is computed on the GPU, fully exploiting the computational power. The simulation speed achieved is one to two orders of magnitude faster than the equivalent central processing unit (CPU) code. This GPU implementation of SPH allows high resolution SPH modeling in hours and days, rather than in weeks and months, on inexpensive and readily available hardware.

Hazard assessment at Mount Etna using a hybrid lava flow inundation model and satellite-based land classification

Using a lava flow emplacement model and a satellite-based land cover classification, we produce a map to allow assessment of the type and quantity of natural, agricultural and urban land cover at risk from lava flow invasion. The first step is to produce lava effusion rate contours, i.e., lines linking distances down a volcano’s flank that a lava flow will likely extend if fed at a given effusion rate from a predetermined vent zone. This involves first identifying a vent mask and then running a downhill flow path model from the edge of every pixel around the vent mask perimeter to the edge of the DEM. To do this, we run a stochastic model whereby the flow path is projected 1,000 times from every pixel around the vent mask perimeter with random noise being added to the DEM with each run so that a slightly different flow path is generated with each run. The FLOWGO lava flow model is then run down each path, at a series of effusion rates, to determine likely run-out distance for channel-fed flow extending down each path. These results are used to plot effusion rate contours. Finally, effusion rate contours are projected onto a land classification map (produced from an ASTER image of Etna) to assess the type and amount of each land cover class falling within each contour. The resulting maps are designed to provide a quick look-up capability to assess the type of land at risk from lava extending from any location at a range of likely effusion rates. For our first (2,000 m) vent zone case used for Etna, we find a total of area of ~680 km2 is at risk from flows fed at 40 m3 s−1, of which ~6 km2 is urban, ~150 km2 is agriculture and ~270 km2 is grass/woodland. The model can also be run for specific cases, where we find that Etna’s 1669 vent location, if active today, would likely inundate almost 11 km2 of urban land, as well as 15.6 km2 of agricultural land, including 9.5 km2 of olive groves and 5.2 km2 of vineyards and fruit/nut orchards.

OpenMP parallelization of the SCIARA Cellular Automata lava flow model: performance analysis on shared-memory computers

Parallel Computing represents a valid solution for reducing execution times in simulations of complex geological processes, such as lava flows, debris flows and, in general, of fluid-dynamic processes. In these cases, Cellular Automata (CA) models have proved to be effective when the behavior of the system to be modeled can be described in terms of local interactions among its constituent parts. Cellular Automata are parallel computing models, discrete in space and time; space is generally subdivided into cells of uniform size and the overall dynamics of the system emerges as the result of the simultaneous application, at discrete time steps, of proper local rules of evolution to each one of them. Due to their intrinsic parallelism, CA models are attractive since they are suitable to be effectively and naturally implemented on parallel computers achieving also high performance. In the recent past, CA models were efficiently executed on distributed memory architectures, such as Beowulf clusters and many-node Supercomputers, while fewer implementations are found regarding shared-memory computers, such as in multi-core machines. This paper shows performance results of the parallelization of a well-known CA model for simulating lava flows – the SCIARA model – in a shared memory environment, by means of OpenMP, an Application Programming Interface which supports multi-platform shared-memory parallel programming.

Sounding the subsurface of Athabasca Valles using MARSIS radar data: Exploring the volcanic and fluvial hypotheses for the origin of the rafted plate terrain

To test the volcanic and fluvial hypotheses for the origin of the rafted plate terrain observed in the vicinity of Athabasca Valles (5°N, 150°E, Central Elysium Planitia), we investigated the subsurface radar echo from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) 5‐MHz band data over this area. The backscattered signal losses were compared to finite difference time domain (FDTD) simulations of those arising from three hypothetical geoelectrical subsurface models, which differed in their assumed composition (percentage basalt versus ice) and assumed mode of origin (fluvial discharge/“frozen sea,” mudflow, and low‐viscosity lavas). The dielectric values used in these models are derived from laboratory measurements of Mars analog materials under Mars‐like conditions. FDTD simulations suggest that if the near‐surface environment is ice‐rich, it will result in an average loss rate of 0.053 dB/m for massive ice (having less than 1% of suspended particulates) and 0.065 dB/m for a mudflow (consisting of a 50/50 mixture of ice and basaltic dust). Whereas the losses associated with a lava flow model increase to 0.19 dB/m. In comparison, the actual signal losses experienced by MARSIS within this region were on the order of 0.18 dB/m within the first 160 m beneath the surface. This suggests that propagation characteristics of Athabasca's near‐subsurface are more consistent with a volcanic rather than a fluvial or mudflow origin of the rafted plate terrain, although limitations on radar sounding depth in this region cannot rule out the possibility of more deeply buried massive ice deposits.

A hybrid model for leveed lava flows: Implications for eruption styles on Mars

Many channelized lava flows on the plains of Mars have substantial embanking margins and levees inferred to have been stationary while the central channel was active. Levee formation can be attributed to two end‐member processes during emplacement: construction during passage of the flow front and growth along the entire length of the flow while it is active. It is shown here that the amount of lava that can be deposited by the flow front alone is limited. Estimates of the levee volume for many Mars plains flows exceed this limit and must have formed by processes that continued after the passage of the front. Experimental studies of analogous laboratory flows also indicate a combination of both modes of emplacement. A model that combines both modes of levee formation is presented, including a method for estimating volumetric flow rate, eruption duration, and viscosity. Six lava flows on the plains of the Tharsis volcanic province are used as illustrative examples. Crustal thicknesses for the six flows examined range from 9 to 23 m. Estimated emplacement times required to cool crusts of these thicknesses range from 1 year to 10 years. Corresponding viscosities are on the order of 105–106 Pa s. Effusion rates range from 25 to 840 m3 s−1 and are all within the range of terrestrial observations. Therefore, the large leveed plains flows on Mars are not dramatically different in eruption rate or lava viscosity from large terrestrial analogs.

A new approach to assess long‐term lava flow hazard and risk using GIS and low‐cost remote sensing: the case of Mount Cameroon, West Africa

Mount Cameroon (MC), West Africa's most active volcano, is a typical example of a hazardous volcano in a densely populated area, often inflicting damage by lava flows. The spatial variation of the lava flow hazard has not been mapped systematically at MC and at many other volcanoes in developing countries because they are insufficiently documented and not continuously, systematically monitored with integrated state‐of‐the‐art methods. Sophisticated lava flow models requiring the specification of numerous physical properties cannot yet be applied in such cases. Hence, a low‐cost approach is proposed to assess the medium‐ to long‐term spatial variation of lava flow hazard. The ‘lava flow zonation system using low‐cost methods’ (LAZSLO) approach takes advantage of freely available topographic data and moderate‐resolution (10–100 m) satellite imagery. For any eruption, the formulation used here expresses the probability of lava flow invasion at any location as a product of the spatial variation of eruption probability and exposure of low‐lying terrain to lava flow reach. The last term is derived by determining the upslope area from where lava flows can invade a given site. A standard UNESCO formula is then used to estimate the lava flow risk. Hazard assessment results at MC indicate that the southwest and northeast flanks are the most hazardous from lava flows, whereas the risk of damage is greatest in the area between Limbe, Mapanja and Batoke, where industrial, urban and tourism infrastructures are developing rapidly. The presented approach can be applied to assist local authorities with disaster preparedness and emergency planning at many poorly studied volcanoes, particularly in developing countries with limited financial resources.

New estimates for Io eruption temperatures: Implications for the interior

The initial interpretation of Galileo data from Jupiter's moon, Io, suggested eruption temperatures ⩾ 1600 ° C . Tidal heating models have difficulties explaining Io's prodigious heat flow if the mantle is > 1300 ° C , although we suggest that temperatures up to ∼ 1450 ° C may be possible. In general, Io eruption temperatures have been overestimated because the incorrect thermal model has been applied. Much of the thermal emission from high-temperature hot spots comes from lava fountains but lava flow models were utilized. We apply a new lava fountain model to the highest reported eruption temperature, the SSI observation of the 1997 eruption at Pillan. This resets the lower temperature limit for the eruption from ∼1600 to ∼ 1340 ° C . Additionally, viscous heating of the magma may have increased eruption temperature by ∼ 50 – 100 ° C as a result of the strong compressive stresses in the ionian lithosphere. While further work is needed, it appears that the discrepancy between observations and interior models is largely resolved.

Topographic variability on Mars: Implications for lava flow modeling

A new data analysis technique is presented for quantifying topographic variability on the surface of Mars directly from Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Record (PEDR) elevation data. The statistic expressing the degree of variability is the mean standard deviation of the residuals resulting from regressions on MOLA PEDR elevation profiles. This topography statistic is determined for ten volcanic areas on the basis of thousands of data points from 181 PEDRs. The topography statistic varies considerably, exhibiting a strong correlation to volcanic area. Despite the correlation with volcanic area, the correlation between topographic variability and slope is weak. Lava flow thickening behavior is quantified with two statistics that are, in turn, used as a rough measure of rheologic change. There is a strong, significant correlation between both flow thickening statistics and topographic variability. These results suggest that the influence of local topographic variability is more important than previously thought in modeling lava flows on Mars.

Factors affecting the accuracy of thermal imaging cameras in volcanology

Volcano observatories and researchers are recognizing the potential usefulness of thermal imaging cameras both before and during volcanic eruptions. Obvious applications include measurements of the surface temperatures of active lava domes and lava flows to determine the location of the most active parts of these potentially hazardous features. If appropriate precautions are taken, the new generation of thermal imaging cameras can be used to extract quantitative as well as qualitative information on volcanic activity. For example, they can be used to measure the temperature of lava on eruption and to reveal how the crust cools during flow emplacement. This is important for the validation of lava flow models. To ensure that meaningful temperatures are collected, thermal imaging data must be corrected for instrumental errors, emissivity of the surface being imaged, atmospheric attenuation, viewing angle and surface roughness. Controlled laboratory experiments have been undertaken to determine the emissivity of smooth and rough samples and the effects of viewing angle and to quantify the errors. Measured emissivities range from 0.973 ± 0.002 for smooth samples of basalt and 0.984 ± 0.004 for rough samples. Errors in emissivity‐corrected temperatures are within ±15°C for lava at 1100°C. Variations from individual sensor receptors, which provide individual pixel temperature data, were found to be 0.6% and instrumental errors of the cameras used were 0.1%. Apparent temperatures were found to vary by less than the instrumental error for viewing angles up to 30 degrees from normal to lava, and thereafter increased by ∼1°C per degree. By increasing the apparent viewing distance of a small vent on Mount Etna from 1.5 to 30 m, the maximum temperature is shown to decrease by 53°C due to integrated averaging of radiance over increased pixel areas. At a viewing distance of 250 m the maximum temperature decreased by ∼200°C with a further 75°C decrease due to atmospheric attenuation for a relative humidity of 50%. However, errors in relative humidity measurements can lead to atmospheric attenuation correction inaccuracies up to 200°C at viewing distances of 1 km. We show how temperatures measured using thermal imaging cameras can be corrected to give improved estimates of temperature distributions on the surface of active lava flows.