Lava Flow Volume Research Articles

Applications of ArcticDEM for measuring volcanic dynamics, landslides, retrogressive thaw slumps, snowdrifts, and vegetation heights

Topographical changes are of fundamental interest to a wide range of Arctic science disciplines faced with the need to anticipate, monitor, and respond to the effects of climate change, including geohazard management, glaciology, hydrology, permafrost, and ecology. This study demonstrates several geomorphological, cryospheric, and biophysical applications of ArcticDEM – a large collection of publicly available, time-dependent digital elevation models (DEMs) of the Arctic. Our study illustrates ArcticDEM's applicability across different disciplines and five orders of magnitude of elevation derivatives, including measuring volcanic lava flows, ice cauldrons, post-failure landslides, retrogressive thaw slumps, snowdrifts, and tundra vegetation heights. We quantified surface elevation changes in different geological settings and conditions using the time series of ArcticDEM. Following the 2014–2015 Bárðarbunga eruption in Iceland, ArcticDEM analysis mapped the lava flow field, and revealed the post-eruptive ice flows and ice cauldron dynamics. The total dense-rock equivalent (DRE) volume of lava flows is estimated to be (1431 ± 2) million m3. Then, we present the aftermath of a landslide in Kinnikinnick, Alaska, yielding a total landslide volume of (400 ± 8) × 103 m3 and a total area of 0.025 km2. ArcticDEM is further proven useful for studying retrogressive thaw slumps (RTS). The ArcticDEM-mapped RTS profile is validated by ICESat-2 and drone photogrammetry resulting in a standard deviation of 0.5 m. Volume estimates for lake-side and hillslope RTSs range between 40,000 ± 9000 m3 and 1,160,000 ± 85,000 m3, highlighting applicability across a range of RTS magnitudes. A case study for mapping tundra snow demonstrates ArcticDEM's potential for identifying high-accumulation, late-lying snow areas. The approach proves effective in quantifying relative snow accumulation rather than absolute values (standard deviation of 0.25 m, bias of −0.41 m, and a correlation coefficient of 0.69 with snow depth estimated by unmanned aerial systems photogrammetry). Furthermore, ArcticDEM data show its feasibility for estimating tundra vegetation heights with a standard deviation of 0.3 m (no bias) and a correlation up to 0.8 compared to the light detection and ranging (LiDAR). The demonstrated capabilities of ArcticDEM will pave the way for the broad and pan-Arctic use of this new data source for many disciplines, especially when combined with other imagery products. The wide range of signals embedded in ArcticDEM underscores the potential challenges in deciphering signals in regions affected by various geological processes and environmental influences.

Monogenetic scoria cone and associated lava flow volume estimates and their controlling factors

Estimating eruption volumes of volcanoes is crucial for studying the development and evolution of volcanoes and assessing volcanic hazards. Volume estimates for polygenetic volcanoes are well-explored but individual monogenetic volcanoes have received less attention. This could be attributed to the lower perceived hazards resulting from their smaller size and rare eruptive occurrences within volcanic fields. However, accurately determining the volume of individual monogenetic volcanoes is significant for understanding volcanic field development and evolution. Estimates of individual monogenetic eruptions may be challenging due to overlapping lava flows from different vents within a volcanic field or underestimation resulting from the breaching of small-volume scoria cones. This study aims to evaluate the relationship between the morphometric parameters of scoria cones and the volumes of associated lava flows using the globally free Advanced Land Observing Satellite (ALOS) World 3D 30 m (AW3D30) DEM, the US National Elevation Dataset (NED) 10 m DEM, and related satellite images and terrain maps. The results show that the diameter of the scoria cone base (Wco) correlates best with the associated lava flow volume, and Wco is the parameter least affected by later onlapping lava flows. Numerous factors influence the volumes of monogenetic volcanic eruptions. The regional tectonic environment, such as tectonic setting and crust thickness, has been found to control Wco and hence the volume of monogenetic volcanoes. Subduction zones and thicker crust settings are characterized by the most voluminous monogenetic volcanoes. These environments facilitate the accumulation of magma, supporting larger volcanic eruptions. Magma density also correlates with monogenetic eruption volume. Lower density magma is more likely to erupt and form larger monogenetic volcanoes. Furthermore, pre-existing crustal weaknesses such as fault systems are the main factors affecting magma movement in monogenetic shallow plumbing systems and facilitate magma ascent to the surface. Local stresses appear to have a lesser influence on eruptive volumes. Magma source shape has minor influence on monogenetic eruption volumes. Evaluation of all these parameters will provide more robust estimates of potential eruption volumes, hence informing volcanic field hazards assessment.

Lava deltas, a key landform in oceanic volcanic islands: El Hierro, Canary Islands

Marine and subaerial erosion of volcanic ocean islands form coastal cliffs and shore platforms, particularly during stable sea levels. Posterosional lava flows can spill over these coastal cliffs and fill the platforms, leading to the progradation of lava deltas. This work aims to analyze this volcanic rocky coast setting at the island scale and to assess the volcanic constructional and erosive degradational effects on the coast at the scale of one volcanic edifice. El Hierro Island, Canary Islands, exemplifies a rocky coast with an active sea-cliff profile, reflecting its early evolutionary stage as a young ocean volcanic island with no fringing reef. The occurrence of a contemporary insular shelf formed during the Holocene sea-level highstand (<7 ka) allows constraining the ages of those eruptions forming lava deltas affecting this geomorphological landform. A detailed bathymetry around the island allowed us to distinguish 17 eruptions fulfilling this criterion. The Montaña del Tesoro, which occurred about 1050 years BP, is one of these eruptions and was selected as a case study for morphometric modeling integrating subaerial and submarine data at the scale of a volcanic edifice. This eruption was a Strombolian basaltic volcanic event that produced a scoria cone, pyroclastic fall deposits, and lava flows that reached the ocean in the eastern rift zone of El Hierro island. We combine field-based observations with topographic and bathymetric data analysis to reconstruct the pre- and post-eruption Digital Elevation Models (DEMs) and, comparing with present-day DEM, to analyze morphometrically the influence of volcanism on the coastal landscape's development. The resulting landform complexity required the discretization of the lava field according to the coastline evolution and lava front sectors, and the subaerial or submarine lava placement. The pyroclastic materials' total erupted bulk volume (12,829,578 m3) corresponds to a volcanic eruption index (VEI) of 3. This event was primarily effusive. From a dense rock equivalent (DRE) volume of 25,615,424 m3, 87 % flowed as lava, 10 % formed the cinder cone, and 3 % the tephra fall deposits. We quantitatively demonstrate that dominant degradation occurs in the lava field, mainly disturbed by marine erosion. Marine erosion removed 9 % of the erupted volume of lava flows against 1 % by fluvial erosion. This work provides methods and results of great interest with different implications in oceanic volcanic islands, among which we can mention coastal planning (e.g., rock coast evolution) and volcanic risk assessment (e.g., the importance of Holocene sea-level rise on the development of shore platforms facilitating the progradation of lava deltas).

The Magmatic Architecture of Continental Flood Basalts I: Observations From the Deccan Traps

AbstractFlood basalts are some of the largest magmatic events in Earth history, with intrusion and eruption of millions of km3 of basaltic magma over a short time period (∼1–5 Ma). A typical continental flood basalt (CFB) is emplaced in hundreds of individual eruptive episodes lasting decades to centuries with lava flow volumes of 103–104 km3. These large volumes have logically led to CFB models invoking large magma reservoirs (–105 km3) within the crust or at Moho depth. Since there are currently no active CFB provinces, we must rely on observations of past CFBs with varying degrees of surface exposure to develop and test models. In the last few decades, significant improvements in geochronological, geochemical, paleomagnetic, volcanological, and paleo‐proxy measurements have provided high‐resolution constraints on CFB eruptive tempo ‐ the volume, duration, and frequency of individual eruptive episodes. Using the well‐studied Deccan Traps as an archetype for CFB systems, we compile multiple lines of evidence–geochronology, eruption tempo, dike spatial distribution, intrusive‐extrusive ratio, geochemical variations, and volcanological observations–to assess the viability of previous models. We find that the presence of just a few large crustal magma reservoirs is inconsistent with these constraints. Although observations from the Deccan Traps primarily motivate our model, we discuss constraints from other CFBs to illustrate that this conclusion may be broadly applicable for CFB magmatic systems in general.

Anatomy of a Paroxysmal Lava Fountain at Etna Volcano: The Case of the 12 March 2021, Episode

On 13 December 2020, Etna volcano entered a new eruptive phase, giving rise to a number of paroxysmal episodes involving increased Strombolian activity from the summit craters, lava fountains feeding several-km high eruptive columns and ash plumes, as well as lava flows. As of 2 August 2021, 57 such episodes have occurred in 2021, all of them from the New Southeast Crater (NSEC). Each paroxysmal episode lasted a few hours and was sometimes preceded (but more often followed) by lava flow output from the crater rim lasting a few hours. In this paper, we use remote sensing data from the ground and satellite, integrated with ground deformation data recorded by a high precision borehole strainmeter to characterize the 12 March 2021 eruptive episode, which was one of the most powerful (and best recorded) among that occurred since 13 December 2020. We describe the formation and growth of the lava fountains, and the way they feed the eruptive column and the ash plume, using data gathered from the INGV visible and thermal camera monitoring network, compared with satellite images. We show the growth of the lava flow field associated with the explosive phase obtained from a fixed thermal monitoring camera. We estimate the erupted volume of pyroclasts from the heights of the lava fountains measured by the cameras, and the erupted lava flow volume from the satellite-derived radiant heat flux. We compare all erupted volumes (pyroclasts plus lava flows) with the total erupted volume inferred from the volcano deflation recorded by the borehole strainmeter, obtaining a total erupted volume of ~3 × 106 m3 of magma constrained by the strainmeter. This volume comprises ~1.6 × 106 m3 of pyroclasts erupted during the lava fountain and 2.4 × 106 m3 of lava flow, with ~30% of the erupted pyroclasts being remobilized as rootless lava to feed the lava flows. The episode lasted 130 min and resulted in an eruption rate of ~385 m3 s−1 and caused the formation of an ash plume rising from the margins of the lava fountain that rose up to 12.6 km a.s.l. in ~1 h. The maximum elevation of the ash plume was well constrained by an empirical formula that can be used for prompt hazard assessment.

Lava effusion rate evolution and erupted volume during the 2018 Kīlauea lower East Rift Zone eruption

The 2018 eruption on the lower East Rift Zone of Kīlauea Volcano produced one of the largest and most destructive lava flows in Hawai’i during the past 200 years. Over the course of more than 3 months, twenty-four fissures erupted, and the rate of lava effusion varied by two orders of magnitude, with significant implications for evolving flow behavior and hazards. Syn-eruptive data were collected to quantify these changes in lava effusion rate, including video of flow through channels and digital elevation models acquired using small unoccupied aircraft systems, airborne lidar, and airborne single-pass interferometric synthetic aperture radar. Topographic data through time allowed calculation of subaerial lava flow volume and time-averaged discharge rate over the course of the eruption, which we integrated with pre- and post-eruption bathymetric surveys. Repeat videos of the near-vent channel were analyzed with particle velocimetry to extract flow velocities, and these were combined with open channel flow theory to calculate a time series of instantaneous effusion rates. Results show a general increase in dense rock equivalent (DRE) effusion rate from ~7 to ~100 m3/s from early to late May for the whole flow field and ≥ 200 m3/s by mid-June after the eruption had focused at a primary vent. By the end of the eruption in August, 0.9–1.4 km3 DRE of lava had erupted, with 0.4 km3 deposited on land and at least 0.5 km3 offshore. The trends in effusion rate through time reflect magmatic processes in the connected summit and rift zone system that controlled eruption rate, with resulting implications for lava flow dynamics and hazards.

Lava flows of Mt Etna, Italy: the 2019 eruption within the context of the last two decades (1999–2019)

ABSTRACT UAVs have become a useful tool for natural hazard monitoring. In volcanic areas, they allow wider observations of the eruptive behaviour, with no risk for the operator. The SfM technique enables obtaining orthoimages of lava flows and a DEM in a short time. These data are also useful to estimate lava flow volumes and the mass output rate characterizing an eruption. We present the results of ten UAV surveys made during and after the 30 May – 6 June 2019 eruption of Etna volcano, projecting the data in a time context back until 1999. Orthoimages taken on different days allowed monitoring the morpho-structural evolution of the fissures, capturing the lava flows propagation and the accumulation of pyroclastic deposits. From 1999 to 2018, there were nine flank-eruptions and dozens of summit-eruptions, which for graphic simplicity have been grouped by year in the map. The resulting map represents the most updated of the recent lava flows of Etna.

Historical lava flow fields at Hekla volcano, South Iceland

Hekla volcano is known to have erupted at least 23 times in historical time (last 1100 years); often producing mixed eruptions of tephra and lava. The lava flow volumes from the 20th century have amounted 80\% to almost 100\% of the entire erupted volume. Therefore, evaluating the extent and volume of individual lava flows is very important when assessing the historical productivity of Hekla volcano. Here we present new maps of the historical lava flow fields at Hekla in a digital format. The maps were produced at a scale of 1:2000–10000 using a catalogue of orthophotos since 1945, acquired before and after each of the last five eruptions, combined with field observation of stratigraphy, soil profiles, tephra layers and vegetation cover. The new lava flow maps significantly improve the historical eruptive history of Hekla, prior to the 1947 eruption. The historical lava flow fields from Hekla cover ∼233 km² and the lavas reach up to 16 km from Hekla volcano. Flow lengths up to 20 km are known, though lava flows only travelled up to 8–9 km from Hekla in the last 250 years. Identified historical vents are distributed between 0 and 16 km from Hekla volcano and vents are known to have migrated up to 5 km away from Hekla during eruptions. We have remapped the lava flow fields around Hekla and assigned the identified flow fields to 16 eruptions. In addition, ca. 60 unidentified lava units, which may be of historical age, have been mapped. It is expected that some of these units are from known historical Hekla eruptions such as the 1222, 1341, 1510, 1597, 1636 and potentially even from the previously excluded eruptions such as 1436/1439.

UAVs for volcano monitoring: A new approach applied on an active lava flow on Mt. Etna (Italy), during the 27 February–02 March 2017 eruption

Mt. Etna (Italy) with 55 effusive events in the last six years is one of the most active volcanoes in the world, with a million people living on its flank and thousands of tourists who visit it every summer.For this reason, the lava flow monitoring for risk mitigation and Civil Protection purposes is one of the fundamental tasks of the Cartographic Laboratory of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo. This activity was traditionally performed using data collected from the field (with terrestrial GPS surveys) and from helicopter taking visible and thermal images. During the 27 February–02 March 2017 eruption the FlyEye Team, applied Unmanned Aerial Vehicles to monitor the active lava flow. Two high-resolution UAV surveys were performed on the lava flow field on the south flank of Mt. Etna, between 3050 and 2600 m a.s.l., obtaining almost 1170 images. Structure-from-Motion techniques were applied to create orthophotos and Digital Elevation Models (DEM) of the lava flow field and surroundings. The obtained DEM has a resolution of 14.2, and 20.7 cm/px for the main lava flow and the west branch, respectively. On the wall, the 96% of the lava flow field was mapped using aerial images by UAV covering an area of 0.3 × 106 m2. Lava flow volume was calculated with the topographic approach: difference between post- and pre-eruption surface, DEM 2017 and DEM 2014, respectively. The impossibility of spreading the GCPs homogenously distorted the resulting DEM; for this reason, it was necessary to align the lava flow point clouds, obtained from the photogrammetry software, to the basal 2014 DEM. Subtracting the two DEMs a lava flow thickness grid resulted leading to a total volume of 1.4 × 106 m3 and an error estimation of about 20%. Finally, dividing the total volume for the effusion duration (63 h) a mean output rate of 6.2 m3/s resulted. The calculated volcanological parameters have the same order of magnitude of the previous activity of Mt. Etna, between 2011 and 2016. This research demonstrates that UAV photogrammetry was successfully exploited during an eruptive crisis, allowing a first fast processing, to obtain an orthophoto of the lava flow field, useful for “decision makers” and a further slower processing for the realization of a high-resolution DEM. The latter makes it possible to update the topography, another important argument for Civil Protection purpose. This paper describes a methodology that could be applied during other natural events in extreme environmental conditions.

The emplacement of the active lava flow at Sinabung Volcano, Sumatra, Indonesia, documented by structure-from-motion photogrammetry

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 2.9km long and had a volume of 1.03±0.14×108m3, leading to an estimated time-averaged discharge rate of 4.8±0.6m3s−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.

Compositional and volumetric development of a monogenetic lava flow field: The historical case of Paricutin (Michoacán, Mexico)

Paricutin volcano is the youngest and most studied monogenetic volcano in the Michoacán-Guanajuato volcanic field (Mexico), with an excellent historical record of its nine years (February 1943 to March 1952) of eruptive activity. This eruption offered a unique opportunity to observe the birth of a new volcano and document its entire eruption. Geologists surveyed all of the eruptive phases in progress, providing maps depicting the volcano's sequential growth. We have combined all of those previous results and present a new methodological approach, which utilizes state of the art GIS mapping tools to outline and identify the 23 different eruptive phases as originally defined by Luhr and Simkin (1993). Using these detailed lava flow distribution maps, the volume of each of the flows was estimated with the aid of pre- and post-eruption digital elevation models. Our procedure yielded a total lava flow volume ranging between 1.59 and 1.68km3 DRE, which is larger than previous estimates based on simpler methods. In addition, compositional data allowed us to estimate magma effusion rates and to determine variations in the relative proportions of the different magma compositions issued during the eruption. These results represent the first comprehensive documentation of the combined chemical, temporal, and volumetric evolution of the Paricutin lava field and provide key constraints for petrological interpretations of the nature of the magmatic plumbing system that fed the eruption.

TanDEM‐X Time Series Analysis Reveals Lava Flow Volume and Effusion Rates of the 2012–2013 Tolbachik, Kamchatka Fissure Eruption

AbstractAssessing eruption volumes is one of the major challenges in volcano research but provides valuable insights into the dynamics of an eruption and the associated hazard. One way to estimate this important parameter is the generation and differencing of digital elevation models (DEMs) acquired before, during, and after an eruption. The satellite mission TanDEM‐X enables generation of time series of DEMs using synthetic aperture radar satellite imagery. We use these data to study the 2012–2013 eruption of Tolbachik in Kamchatka. We developed a processing scheme for generation of 18 DEMs from TanDEM‐X imagery that relies on the generation of a preeruption DEM which is used to process the syneruption and posteruption data pairs. Differencing each DEM with the preeruption DEM enables mapping the lava flows and measuring lava flow volume over time and to estimate lava extrusion rates. We find a final lava flow volume of 0.53 km3 covering an area of 36 km2 by the end of the eruption. An uncertainty analysis is performed while analyzing the DEM differences in areas where no topographic change is expected, leading to an error of ±0.01 km3 for the final lava flow volume. The lava effusion was with 247.92 m3/s very high in the first days of the eruption and rapidly decayed toward its end. While many basaltic eruptions follow an exponentially decaying flow model, the extrusion rates at Tolbachik are more compatible with a 1/t model. This special characteristic might be useful to gain further insight into the eruption process at Tolbachik.

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.

High‐resolution digital elevation model from tri‐stereo Pleiades‐1 satellite imagery for lava flow volume estimates at Fogo Volcano

AbstractResolving changes in topography through time using accurate high‐resolution digital elevation models (DEMs) is key to understanding active volcanic processes. For the first time in a volcanic environment, we utilize very high‐resolution tri‐stereo optical imagery acquired by the Pleiades‐1 satellite constellation and generate a 1 m resolution DEM of Fogo Volcano, Cape Verde—the most active volcano in the Eastern Atlantic region. Point cloud density is increased by a factor of 6.5 compared to conventional stereo imagery, and the number of 1 m2 pixels with no height measurements is reduced by 43%. We use the DEM to quantify topographic changes associated with the 2014–2015 eruption at Fogo. Height differences between the posteruptive Pleiades‐1 DEM and the preeruptive topography from TanDEM‐X give a lava flow volume of 45.83 ± 0.02 × 106 m3, emplaced over an area of 4.8 km2 at a mean rate of 6.8 m3 s−1.

High‐resolution TanDEM‐X DEM: An accurate method to estimate lava flow volumes at Nyamulagira Volcano (D. R. Congo)

AbstractNyamulagira and Nyiragongo are two of the most active volcanoes in Africa, but their eruptive histories are poorly known. Assessing lava flow volumes in the region remains difficult, as field surveys are often impossible and available Digital Elevation Models (DEMs) do not have adequate spatial or temporal resolutions. We therefore use TerraSAR‐X add‐on for Digital Elevation Measurement (TanDEM‐X) interferometry to produce a series of 0.15 arc sec (∼5 m) DEMs from between 2011 and 2012 over these volcanoes. TanDEM‐X DEMs have an absolute vertical accuracy of 1.6 m, resulting from the comparison of elevation with GPS measurements acquired around Nyiragongo. The difference between TanDEM‐X‐derived DEMs from before and after the 2011–2012 eruption of Nyamulagira provides an accurate thickness map of the lava flow emplaced during that activity. Values range from 3 m along the margins to 35 m in the middle, with a mean of 12.7 m. The erupted volume is 305.2 ± 36.0 × 106 m3. Height errors on thickness depend on the land covered by the flow and range from 0.4 m in old lavas to 5.5 m in dense vegetation. We also reevaluate the volume of historical eruptions at Nyamulagira since 2001 from the difference between TanDEM‐X and SRTM 1 arc sec DEMs and compare them to previous work. Planimetric methods used in literature are consistent with our results for short‐duration eruptions but largely underestimate the volume of the long‐lived 2011–2012 eruption. Our new estimates of erupted volumes suggest that the mean eruption rate and the magma supply rate were relatively constant at Nyamulagira during 2001–2012, respectively, 23.1 m3 s−1 and 0.9 m3 s−1.

Magma emission rates from shallow submarine eruptions using airborne thermal imaging

The effusion rate is the most important parameter to gather when a volcanic eruption occurs, because it controls the way in which a lava body grows, extends and expands, influencing its dimensional properties. Calculation of lava flow volume from thermal images collected by helicopter surveys has been largely used during the last decade for monitoring subaerial effusive eruptions. However, due to the depths where volcanic activity occurs, monitoring submarine volcanic eruptions is a very difficult task. The 2011–2012 submarine volcanic eruption at El Hierro, Canary Islands, has provided a unique and excellent opportunity to monitor eruptive processes occurring on the seabed. The use of a hand-held thermal camera during daily helicopter flights allowed us to estimate for the first time the daily and total erupted magma volumes from a submarine eruption. The volume of magma emitted during this eruption has been estimated at 300Mm3, giving an average effusion rate of ~25m3s−1. Thermal imagery by helicopter proved to be a fast, inexpensive, safe and reliable technique of monitoring volcanic eruptions when they occur on the shallow seabed.

Lava discharge rate estimates from thermal infrared satellite data for Pacaya Volcano during 2004–2010

Pacaya is one of the most active volcanoes in Central America and has produced lava flows frequently since 1961. All effusive activity between 1961 and 2009 was confined by an arcuate collapse scarp surrounding the northern and eastern flanks. However, the recent breaching of this topographic barrier, and the eruption of a large lava flow outside of the main center of activity, have allowed lava to extend into nearby populated areas, indicating the need for assessment and monitoring of lava flow hazards. We investigated whether a commonly used satellite-based model could produce accurate lava discharge rates for the purpose of near-real-time assessment of hazards during future eruptions and to assess the dynamics of this persistently degassing system. The model assumes a linear relationship between active lava flow area and time-averaged discharge rate (TADR) via a simple conversion factor. We calculated the conversion factor via two methods: (1) best-fitting of satellite-derived flow areas to ground-based estimates of lava flow volume, and (2) theoretically via a parameterized model that takes into account the physical properties of the lava. To apply the latter method, we sampled four lava flows and measured density, vesicularity, crystal content, and major element composition. We found the best agreement of conversion factors in the eruption with the most complete satellite coverage, and used data for these flows to define the linear relationship between area and discharge rate. The physical properties of the sampled flows were essentially identical, so that any discrepancy between the two methods of calculating conversion factors must be due to modeling errors or environmental factors unaccounted for by the parameterized model. However, our best-fitting method provides a new means to set the conversion appropriately, and to obtain self-consistent TADRs. We identified two distinct types of effusive activity at Pacaya: Type 1 activity characterized by initially high TADRs of about 1–10m3·s−1, followed by a waning phase, and Type 2 activity characterized by low, scattered TADRs of about 0.1–1m3·s−1. The risk associated with Type 1 activity is much higher, so identifying the Type 1 radiance signature in satellite imagery is useful for monitoring an ongoing eruption.

Variations in eruptive style and depositional processes of Neoproterozoic terrestrial volcano-sedimentary successions in the Hamid area, North Eastern Desert, Egypt

Two contrasting Neoproterozoic volcano-sedimentary successions of ca. 600m thickness were recognized in the Hamid area, Northeastern Desert, Egypt. A lower Hamid succession consists of alluvial sediments, coherent lava flows, pyroclastic fall and flow deposits. An upper Hamid succession includes deposits from pyroclastic density currents, sills, and dykes. Sedimentological studies at different scales in the Hamid area show a very complex interaction of fluvial, eruptive, and gravitational processes in time and space and thus provided meaningful insights into the evolution of the rift sedimentary environments and the identification of different stages of effusive activity, explosive activity, and relative quiescence, determining syn-eruptive and inter-eruptive rock units.The volcano-sedimentary deposits of the study area can be ascribed to 14 facies and 7 facies associations: (1) basin-border alluvial fan, (2) mixed sandy fluvial braid plain, (3) bed-load-dominated ephemeral lake, (4) lava flows and volcaniclastics, (5) pyroclastic fall deposits, (6) phreatomagmatic volcanic deposits, and (7) pyroclastic density current deposits. These systems are in part coeval and in part succeed each other, forming five phases of basin evolution: (i) an opening phase including alluvial fan and valley flooding together with a lacustrine period, (ii) a phase of effusive and explosive volcanism (pulsatory phase), (iii) a phase of predominant explosive and deposition from base surges (collapsing phase), and (iv) a phase of caldera eruption and ignimbrite-forming processes (climactic phase). The facies architectures record a change in volcanic activity from mainly phreatomagmatic eruptions, producing large volumes of lava flows and pyroclastics (pulsatory and collapsing phase), to highly explosive, pumice-rich plinian-type pyroclastic density current deposits (climactic phase). Hamid area is a small-volume volcano, however, its magma compositions, eruption styles, and inter-eruptive breaks suggest, that it closely resembles a volcanic architecture commonly associated with large, composite volcanoes.

A new comprehensive classification of the Piton de la Fournaise activity spanning the 1985–2010 period. Search and analysis of short-term precursors from a broad-band seismological station

Piton de la Fournaise volcano (La Réunion Island) is one of the most active basaltic volcanoes, with an average of one eruption every 10months. This study provides the first exhaustive compilation of all volcanic events (intrusions, eruptions, seismic crises) and related parameters at Piton de la Fournaise in the 1985–2010 period. This compilation has been correlated with the analysis of the records from the very broad-band seismological RER station (Geoscope network), located 8.5km north of the summit. Our approach allowed us to identify short-term long period seismic precursors for most eruptions and intrusions. After a signal filtering process that consists in removing the instrumental response and the theoretical Earth tides effect, these precursors can be distributed into 4 classes that depend on their waveform and are globally considered as tilt related with magma transfer inside the sub-aerial part of the volcano edifice. The shapes and characteristics of these transient phenomena (time delay, duration or class) exhibit particular features that can be partly related to other simple eruption or intrusion parameters (location, altitude, volume). Statistical analyses of all events (intrusions and eruptions) are then derived. Estimates of acceleration rates of tilt signal at the RER station have been retrieved for eruptions and intrusions, with the challenge of providing a way to differentiate one from the other in real-time. Acceleration rates seem to correlate with eruptive lava flow volume and a threshold value can be determined allowing us to discriminate between intrusions and eruptions, illustrating the interest of analyzing them for real‐time monitoring. The correlation with the initial seismic crisis marking the opening of magma ascent path was investigated, showing that the delay between the RER transient phenomenon and the start of the seismic crisis has been increasing since the major caldera formation event of 2007. This longer delay may be due to a combination of drastic changes in the internal structure of the edifice: a concomitant decrease in volume of magma batches and a deeper origin of magma setting off volcanic unrest. Our study highlights the additional role of external factors like loading and unloading related to the rainy season and stress field evolution due to Earth tides in influencing magma propagation and volcanic activity.

LIDAR strip adjustment: Application to volcanic areas

DEMs derived from LIDAR data are nowadays largely used for quantitative analyses and modelling in geology and geomorphology. High-quality DEMs are required for the accurate morphometric and volumetric measurement of land features. We propose a rigorous automatic algorithm for correcting systematic errors in LIDAR data in order to assess sub-metric variations in surface morphology over wide areas, such as those associated with landslide, slump, and volcanic deposits. Our procedure does not require a priori knowledge of the surface, such as the presence of known ground control points. Systematic errors are detected on the basis of distortions in the areas of overlap among different strips. Discrepancies between overlapping strips are assessed at a number of chosen computational tie points. At each tie point a local surface is constructed for each strip containing the point. Displacements between different strips are then calculated at each tie point, and minimization of these discrepancies allows the identification of major systematic errors. These errors are identified as a function of the variables that describe the data acquisition system. Significant errors mainly caused by a non-constant misestimation of the roll angle are highlighted and corrected. Comparison of DEMs constructed using first uncorrected and then corrected LIDAR data from different Mt. Etna surveys shows a meaningful improvement in quality: most of the systematic errors are removed and the accuracy of morphometric and volumetric measurements of volcanic features increases. These corrections are particularly important for the following studies of Mt. Etna: calculation of lava flow volume; calculation of erosion and deposition volume of pyroclastic cones; mapping of areas newly covered by volcanic ash; and morphological evolution of a portion of an active lava field over a short time span.