Lava Discharge Research Articles

Dynamical changes in seismic properties prior to, during, and after the 2014–2015 Holuhraun eruption, Iceland

Abstract. When a volcano is monitored using only a single discipline or a single seismic station, it becomes important to harvest information from the limited data set. Changes in the seismic complexity could reveal a dynamic change due to magma propagation. We evaluated permutation entropy (PE) and phase permutation entropy (PPE) to monitor the 2014–2015 Holuhraun eruption in Iceland. These methods provide fast and robust quantification of time series complexity. We additionally calculated the instantaneous frequency (IF), commonly used to monitor the frequency changes in a non-stationary signal; the root-mean square (RMS); and the root-median square (RMeS) of the seismic amplitude. We observed distinct changes in the temporal variation in PE, PPE, and IF, which are consistent with the changing state from quiescence to magma propagation and then to eruption. During the eruption, PE and PPE fit the lava discharge rate, showing their potential to forecast the duration of the eruption. While one parameter may be more sensitive to one stage, the other may respond better to another stage. Therefore, combining them may provide more reliable information. Cluster analysis of these combined parameters shows clusters consistent with the expert interpretation, confirming the power of these parameters to distinguish different eruption stages.

Tracking changes in magma transport from very-long-period seismic signals at Piton de la Fournaise volcano

Changes in magma properties and transport geometry can have a direct impact on volcanic activity. However, such variations can be difficult to track during eruptions. We report previously undetected very-long-period (VLP) signals at Piton de la Fournaise that can be used to probe changes in magma transport. Source analysis of VLP events during the August-October 2015 eruption indicates a source depth of about 0.9-1.2 km and points to the resonance of the magma dike feeding the eruption. The evolution of the resonance period reveals a shortening of the dike when the magma flux decreases at the end of the eruption. VLP events are actually quite frequent at Piton de la Fournaise: all eruptions analyzed in this study exhibit VLP signals that are indicative of rapid drops in lava discharge. This work encourages the detection of VLP signals to monitor changes in magma flow during volcanic eruptions, and anticipate the corresponding evolution in effusive activity.

Long-term ion hydration process and lithosphere-atmosphere coupling following the 2021 Fagradalsfjall volcanic eruption using remotely sensed data

After a series of earthquakes, the Reykjanes peninsula in Iceland faced a volcanic eruption for the first time in 800 years. This volcanism of the 2021 Fagradalsfjall started on March 19, 2021, and lasted until September 18, 2021. In this study, the vestiges of the mutual interplay of Earth’s different geophysical shells due to the local lithospheric changes around the Fagradalsfjall were extensively investigated with the help of satellite-based remotely sensed datasets. Firstly, the regional surface deformations caused by the pre-eruption seismic activity are determined using interferometric image pairs, and horizontal and vertical displacement rates are analyzed. Secondly, the satellite observations revealed that the land surface temperature of the entire area increased to a maximum of 40 °C during the maximum phase of lava discharge by the end of May 2021. Moreover, we observed that the surface mass concentrations of SO2 and CO trace gases started to ascend in parallel with the lava discharge after the initial eruption, where their concentrations were doubled in April before reaching their maximum phases (three to four times more than the initial eruption) in May 2021. The cumulative concentrations of the trace gases in the atmosphere emitted from the Fagradalsfjall volcano pushed the regional atmospheric balance into a non-equilibrium state by creating air ionization through various chemical reactions with other atmospheric gases. These ion clusters underwent an ion hydration process that changed the electric conductivity of the atmospheric boundary layer, which covers the first two kilometers of the atmosphere. Finally, our observations showed a sharp decrease in the atmospheric relative humidity that led to an increase in the atmospheric air temperature due to this ion hydration process. The large ion clusters in the atmospheric boundary layer produced a vertical electric field that penetrated over the affected region and brought long-term changes in the ionosphere layer. This unique phenomenon of the simultaneous interaction of different geophysical layers was specifically observed during the maximum phase of the lava discharge and increased ion concentrations in the atmosphere. The used data sets cover the first three months of the volcanism, and this interval seemed to be sufficient to reveal the atmospheric traces. Our comprehensive study provides an important contribution to the theory of the coupling of volcanism and the Earth's atmospheric dynamics.

Can Lava Flow Like Water? Assessing Applications of Critical Flow Theory to Channelized Basaltic Lava Flows

AbstractFlowing lava and water have dramatically different physical properties but can form similar hydraulic structures, including undular hydraulic jumps, or standing wave trains. In water flows, undular hydraulic jumps are evidence of critical flow (Froude number ∼1) and open‐channel hydraulic theory provides a powerful tool for estimating flow depth and velocity. Monitoring these parameters in an active lava channel is inherently challenging, but essential for calculating lava discharge (effusion rate), a primary control on the rate of flow front advance and ultimate flow runout distance. We analyze undular hydraulic jumps in both water and lava flows to assess the conditions under which they form and, by extension, the potential use of critical flow theory to estimate, in real time, lava flow velocity, depth, and discharge. Experimental data for water flows show that these structures mark the transition from supercritical to subcritical flow. Undular hydraulic jumps in the near‐vent lava channel of the 2018 lower East Rift Zone eruption of Kīlauea, Hawaiʻi also reflect critical flow conditions; their wavelengths scale with flow depth and velocity, consistent with hydraulic theory. Calculated lava effusion rates are similar to estimates made using more traditional approaches (Jeffreys', 1925, https://doi.org/10.1080/14786442508634662, equation based on lava viscosity, density, and channel slope) and with lava volumes derived from topographic‐change mapping. From this we conclude that critical flow phenomena show great potential to track flow dynamics and inform hazard assessment for a wide range of geophysical fluids.

Lava Volume from Remote Sensing Data: Comparisons with Reverse Petrological Approaches for Two Types of Effusive Eruption

Five effusive eruptions of Piton de la Fournaise (La Réunion) are analyzed to investigate temporal trends of erupted mass and sulfur dioxide (SO2) emissions. Daily SO2 emissions are acquired from three ultraviolet (UV) satellite instruments (the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), and the Tropospheric Monitoring Instrument (TROPOMI)) and an array of ground-based UV spectrometers (Network for Observation of Volcanic and Atmospheric Change (NOVAC)). Time-averaged lava discharge rates (TADRs) are obtained from two automatic satellite-based hot spot detection systems: MIROVA and MODVOLC. Assuming that the lava volumes measured in the field are accurate, the MIROVA system gave the best estimation of erupted volume among the methods investigated. We use a reverse petrological method to constrain pre-eruptive magmatic sulfur contents based on observed SO2 emissions and lava volumes. We also show that a direct petrological approach using SO2 data might be a viable alternative for TADR estimation during cloudy weather that compromises hot spot detection. In several eruptions we observed a terminal increase in TADR and SO2 emissions after initial emission of evolved degassed magma. We ascribe this to input of deeper, volatile-rich magma into the plumbing system towards the end of these eruptions. Furthermore, we find no evidence of volatile excess in the five eruptions studied, which were thus mostly fed by shallow degassed magma.

The impact of vent geometry on the growth of lava domes

SUMMARY Thick lava flows that are a feature of many volcanic fields on the Earth and Venus vary from sheet-like to nearly perfect axisymmetric domes. Here, we investigate how these geometrical characteristics depend on the shape of the feeder vent. We study the gravitational spreading of viscous lava erupting from elliptical vents onto a flat surface using 3-D numerical models. The aspect ratio of the vent, defined to be the major to minor axes ratio, varies between 1 and 25. In the limit of an aspect ratio of one, the vent is circular and spreading is axisymmetric. In the limit where the ratio is large, the vent behaves as a fissure. The numerical models rely on an isoviscous lava rheology and a constant volumetric eruption rate. In all cases, the initial phase of the dome’s evolution is in a lava-discharge dominated regime such that spreading is insignificant and the height of the dome increases at a constant rate over the vent area. For vent aspect ratios greater than five, three successive regimes of spreading are identified: 2-D spreading in the direction perpendicular to the major axis of the vent, a transient phase such that the dome shape evolves towards that of a circular dome and a late axisymmetric spreading phase that does not depend on the vent shape. These regimes are delimited by the times required for the flow thickness above the vent to reach a given height and for the flow to spread axisymmetrically up to a length equal to the semi-major axis of the vent. Numerical results for the flow height and runout length tend towards the similarity solutions in the 2-D and axisymmetric regimes. Two main implications for highly viscous (rhyolitic) fissure eruptions can be drawn. First, the fissure length determines the flow regimes. The longer the vent fissure length, the longer the early lava discharge regime and 2-D spreading perpendicular to the length of the fissure. Second, the aspect ratio of fissure-fed lava flows can be used as an indicator of the fissure length and the duration of lava discharge. The ellipticity of some terrestrial fissure-fed flows provides evidence for viscous gravity-driven spreading terminated before the onset of the axisymmetric regime. On the other hand, the circular domes on Venus appear to be the result of fissure-fed eruptions sustained enough for the spreading to reach the axisymmetric regime. We propose relationships providing estimates of the fissure length and the duration of lava discharge based on fossil dome dimensions.

Estimates of lava discharge rate of 2018 Kīlauea Volcano, Hawaiʻi eruption using multi-sensor satellite and laboratory measurements

ABSTRACT The 2018 lower East Rift Zone eruption (LERZ) at Kīlauea Volcano, Hawaiʻi, was the largest event of the last 200 years at the LERZ. Here, we present a lava discharge rate estimation of this eruption by combining a joint analysis of multi-sensor infrared (IR) satellite remote sensing imagery of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) with laboratory measurements of lava properties. The time-averaged discharge rate (TADR) based estimation of the erupted lava volume resulted in circa 9.24 × 108 ± 4.62 × 108 m3 for the subaerial part of the 2018 LERZ eruption. The lava effusion at the LERZ began on 3 May 2018, with relatively low mean output rates of 2.82 ± 1.41 m3 s−1, which then almost doubled after 12 May to 4.94 ± 2.47 m3 s−1, increased after 19 May to 64.97 ± 32.48 m3 s−1 and from 28 May onwards until beginning of August 2018 up to 137.67 ± 68.83 m3 s−1.

Rhyolitic volcano dynamics in the Southern Andes: Contributions from 17 years of InSAR observations at Cordón Caulle volcano from 2003 to 2020

In this article I present a review of InSAR observations of ground deformation at Cordón Caulle volcano, whose 2011–2012 VEI 4-5 eruption is the best scientifically observed and instrumentally recorded rhyolitic eruption to date. I document a complete cycle of pre-eruptive uplift, co-eruptive subsidence and post-eruptive uplift with InSAR data between March 2003 and May 2020, and produced by a complex interplay of magmatic processes. Pre-eruptive data show ~0.5 m of ground uplift in three distinct episodes between 2003 and 2011, with uplift rates between ~3 and ~30 cm/yr. The uplift was likely caused by magma injection resulting in pressurization of the magmatic system at depths of 4–9 km. Data spanning the first 3 days of the eruption show ~1.5 m of deflation produced by two distinct sources at 4–6 km depth located 18 km from each other and up to 10 km from the eruptive vent -- suggesting hydraulic connectivity of a large magma mush zone. A third source of deformation was recorded during the rest of the eruption at a depth of ~5 km, resulting in a total subsidence of ~4.2 m during the whole eruption. On a much smaller spatial scale (~25 km2), InSAR-derived digital elevation models recorded ~250 m of uplift in the area of the eruptive vent interpreted as the intrusion of a shallow laccolith during the first 2.5 months of the eruption and time averaged lava discharge rates up to ~150 m3/s. The co-eruptive time series of reservoir pressure drop and extruded volume follow exponential trends that can be explained by a model of magma reservoir depressurization and conduit flow. Since the end of the eruption, the surface of the volcano was uplifted ~1 m in a sequence of three transient episodes of unrest during 2012 and 2019, with uplift rates between 6 and 45 cm/yr and lasting between 0.5 and 3.2 years. These pulses can be modeled by the same source, a sub-horizontal sill at a depth of ~6 km. Viscoelastic relaxation is not significant on these time scales, hence I interpret these uplift signals as being produced by episodic pulses of magma injection in the crystal mush that likely underlies the volcano. The episodic and abrupt changes of the ground deformation suggest a restless trans-lateral magmatic system at depths of 4–9 km, and active across multiple spatial and temporal scales. Finally, I also discuss challenges of the InSAR technology that should be addressed to detect ground deformation on short time scales, particularly under the low coherence conditions of Cordón Caulle.

Lava Discharge Rate of Sinabung Volcano Obtained from Modis Hot Spot Data

DOI:10.17014/ijog.7.3.241-252To find out the long term data of Sinabung magma discharge rate and how long a series of eruption will be ended, time series of the volume of magma discharge is required. The dominant eruption product is pyroclastic flow that begins with the growth of the lava dome, so it is important to determine the volume of the lava dome over time. The method of determining the volume of magma issued is carried out by using hotspot data to resolve the problem of prevented visual observations and ground measurements. The heat and volume flux data expressed within a long period for a better view of variations in the Sinabung volcanic activity are based on thermal satellite data. Related lava dome volume and seismic data are also displayed to be compared with the heat and volume flux data. The numbers of thermally anomalous pixels and sum of radiance for all detected pixels at Sinabung during an overpass in the period of 2014 to 2018 have a downward trend. The discharge rates in the period of January 2014 to April 2015, Mei 2015 to March 2016, April 2016 to March 2017, and June 2017 to February 2018 are 0.86 m3/sec, 0.59 m3/sec, 0.36 m3/sec, and 0.25 m3/sec, respectively. Assuming no new intrusion or deformation rate changes, the lava discharge will be in the lowest rate in the early 2020s.

Evidences of Plug Pressurization Enhancing Magma Fragmentation During the September 2016 Basaltic Eruption at Piton de la Fournaise (La Réunion Island, France)

AbstractIn September 2016, Piton de la Fournaise volcano, well known for its effusive and Hawaiian fountaining activity, produced, at the end of the eruption, an unusual phase of pulsating ash and bomb emission. Integration of geophysical data, with textural and petrological analysis of the samples, allowed us to constrain the main factors that controlled this sudden shift in activity, potentially dangerous for the tourist population that usually approach these “gentle” eruptive sites. Volcanic tremor, lava discharge rates, fountain heights, and SO2 emission changed rapidly during the eruption. Grain size and componentry of the tephra beds evolved from unimodal all along the sequence to bimodal on the last day of the activity, reflecting the contribution of both Hawaiian fountaining at the main vent (Vent A) and transient explosive activity at the second vent (Vent B). Hawaiian fountaining produced highly vesicular and almost microlite‐free tephra (golden pumice and fluidal scoria) while transient explosive activity emitted denser and crystal‐rich tephra (sideromelane and tachylite scoria) sometimes mingled with vesicular fragments. Permeability measurements on lapilli and bomb‐sized samples reveal that golden pumice and fluidal scoria were more gas‐permeable than the sideromelane and tachylite ones, while textural and chemical analyses of the ash support the hypothesis that these sideromelane and tachylite components were inherited from the subsurface crystallization of the initial golden pumice and fluidal scoria components. We thus suggest that Vent B accumulated a plug of degassed, cooled, and low‐permeable magma, which modulated overpressure pulses under the late input of ascending magma.

Automated Volcano Monitoring Using Multiple Space and Ground Sensors

From 2004 to 2017, an effort was undertaken to integrate space-borne sensing and in situ sensing in an automated system to improve global volcano activity monitoring. This paper reviews a sensor web concept in which a number of volcano monitoring systems were linked together to more accurately monitor volcanic activity, and used this activity measurement to automatically task space assets to acquire further satellite imagery of the detected volcanic activity. This paper discusses the space and ground sensors and how they were linked together as triggers and responses. Over a 13-year period, more than 160,000 alerts coming from various sources lead to 9050 observations by NASA’s Earth Observing-1 spacecraft—imaging about 218 volcanoes. This paper describes the science products automatically produced onboard the satellite and on the ground such as temperature maps and lava discharge volume estimates that are automatically delivered to subscribing users. To evaluate the effectiveness of an out-tasked volcano monitoring system, this study compares the hit rate of our tasked monitoring system to the systematic monitoring system MODVOLC.

Volcano-stimulated marine photosynthesis.

Lava discharge to the ocean from volcano Kīlauea, Hawai'i, triggers phytoplankton blooms

Monitoring the time-averaged discharge rates, volumes and emplacement style of large lava flows by using MIROVA system: the case of the 2014-2015 eruption at Holuhraun (Iceland)

The 2014-2015 eruption at Holuhraun has produced more than 1.5 km 3 of basaltic magma and can be considered one of the major effusive events of the last two centuries in the world. During this eruption the MIROVA system (a volcanic hot-spot detection system based on MODIS middle infrared – MIR - data) has been used to detect and locate the active portions of the lava flow(s), and to measure the heat radiated by the growing lava field. According to these data the eruption was characterized by a slow decay of the radiant power, accompanied by a change in the lava transport mechanism that shifted from open channels, at the beginning of the eruption, to lava tubes, during the last months of activity. Despite the evident evolution of lava transport mechanism, we found that the overall decreasing trend of the thermal flux was mainly controlled by the exponential decline of lava discharge rates, while the increasing insulation of the flow field had a strong impact in transporting efficiently the lava at the distal flow front(s). Our results suggest the apparent time averaged lava discharge rates ( TADR ), derived from satellite thermal data, may fluctuate around the real effusion rate at the vent, especially in the case of large lava flows emplacing in nearly flat conditions. The magnitude and frequency of these fluctuations are mainly controlled by the emplacement dynamic, (i.e. occurrence of distinct major flow units), while the transition from channel- to tube-fed lava transport mechanism play only a minor role (±30%) in the retrieval of TADR using MIR data . When the TADR values are integrated to calculate erupted lava volumes, the effects of pulsating emplacement dynamic become smoothed and the eruptive trend become more clear. We suggest that during the Holuhraun ’s eruption, as well as during many other effusive eruptions, the MIR-derived radiant flux essentially mimic the overall trend of lava discharge rates, with only a minor influence due to the emplacement style and evolving eruptive conditions. From a monitoring and operational perspective, MIROVA demonstrates to be a very valuable tool to follow and, possibly, forecast the evolution of on-going effusive eruption.

The Volume of Lava Erupted During the 2014 to 2015 Eruption at Holuhraun, Iceland: A Comparison Between Satellite‐ and Ground‐Based Measurements

AbstractThe 31 August 2014 to 27 February 2015 eruption at Holuhraun created the largest lava flow field in Iceland since the 1783–1784 Laki eruption. Emplacement of a basaltic flow field of this magnitude onto an effectively flat surface (<0.1°) is a rare occurrence. Lava discharge rate, a fundamental variable that controls flow field emplacement, allows us to estimate the total volume of lava erupted when integrated over time. Thus, discharge rate data are important for volcano monitoring and lava flow modeling. Here we compare discharge rates estimated using data from National Aeronautics and Space Administration's MODerate Resolution Imaging Spectroradiometer (MODIS) and the method of Harris et al. (1997a, https://doi.org/10.1029/96JB03388; 1997b, https://doi.org/10.1007/s004450050174; 2007, https://doi.org/10.1007/s00445‐007‐0120‐y), with estimates of discharge rates derived from comparing intermittent ground‐based measurements of flow field volume. The time‐averaged discharge rates (TADR) reveal a pulsed increase in the first few days of the eruption. Although the trends of the satellite‐ and ground‐based discharge rates are similar, the ground‐based estimates are systematically higher than the satellite‐derived estimates (about 2 to 3 times higher) in the first 30 days of the eruption, and relatively close (within 30%) for the next 20 days. Conversely, during the final 130 days, the satellite‐based estimates are systematically higher than the ground‐based estimates (about 2 times higher). This difference likely arises from the assumption of the lava flow surface temperature used in the space‐based calculation, which may not be entirely representative of this uniquely large and intense basaltic eruption. However, the satellite‐based technique yields a total erupted volume of about 1.21 km3 in good agreement with the 1.2 km3 (84 km2) derived from field observations and mapping.

Measuring effusion rates of obsidian lava flows by means of satellite thermal data

Space-based thermal data are increasingly used for monitoring effusive eruptions, especially for calculating lava discharge rates and forecasting hazards related to basaltic lava flows. The application of this methodology to silicic, more viscous lava bodies (such as obsidian lava flows) is much less frequent, with only few examples documented in the last decades. The 2011–2012 eruption of Cordón Caulle volcano (Chile) produced a voluminous obsidian lava flow (~0.6km3) and offers an exceptional opportunity to analyze the relationship between heat and volumetric flux for such type of viscous lava bodies. Based on a retrospective analysis of MODIS infrared data (MIROVA system), we found that the energy radiated by the active lava flow is robustly correlated with the erupted lava volume, measured independently. We found that after a transient time of about 15days, the coefficient of proportionality between radiant and volumetric flux becomes almost steady, and stabilizes around a value of ~5×106Jm−3. This coefficient (i.e. radiant density) is much lower than those found for basalts (~1×108Jm−3) and likely reflects the appropriate spreading and cooling properties of the highly-insulated, viscous flows. The effusion rates trend inferred from MODIS data correlates well with the tremor amplitude and with the plume elevation recorded throughout the eruption, thus suggesting a link between the effusive and the coeval explosive activity. Modelling of the eruptive trend indicates that the Cordón Caulle eruption occurred in two stages, either incompletely draining a single magma reservoir or more probably tapping multiple interconnected magmatic compartments.

A review of mass and energy flow through a lava flow system: insights provided from a non-equilibrium perspective

A simple formula relates lava discharge rate to the heat radiated per unit time from the surface of active lava flows (the “thermal proxy”). Although widely used, the physical basis of this proxy is still debated. In the present contribution, lava flows are approached as open, dissipative systems that, under favorable conditions, can attain a non-equilibrium stationary state. In this system framework, the onset, growth, and demise of lava flow units can be explained as a self-organization phenomenon characterized by a given temporal frequency defined by the average life span of active lava flow units. Here, I review empirical, physical, and experimental models designed to understand and link the flow of mass and energy through a lava flow system, as well as measurements and observations that support a “real-world” view. I set up two systems: active lava flow system (or ALFS) for flowing, fluid lava and a lava deposit system for solidified, cooling lava. The review highlights surprising similarities between lava flows and electric currents, which typically work under stationary conditions. An electric current propagates almost instantaneously through an existing circuit, following the Kirchhoff law (a least dissipation principle). Flowing lavas, in contrast, build up a slow-motion “lava circuit” over days, weeks, or months by following a gravity-driven path down the steepest slopes. Attainment of a steady-state condition is hampered (and the classic thermal proxy does not hold) if the supply stops before completion of the “lava circuit.” Although gravity determines initial flow path and extension, the least dissipation principle means that subsequent evolution of mature portions of the active lava flow system is controlled by increasingly insulated conditions.

Growth process of the lava dome/flow complex at Sinabung Volcano during 2013–2016

Mount Sinabung, North Sumatra, Indonesia, erupted for the first time in 2010 and reactivated again in 2013. The eruption started with a phreatic phase, changed to phreatomagmatic, and then andesite lava appeared at the summit crater in late December 2013. Lava effusion continued and has been associated with partial to complete collapses of the lava complex, which successively generated pyroclastic density currents (PDCs). The lava complex grew first as a lava dome and then developed into a lava flow (lava extension stage). It extended up to about 3km in horizontal runout distance by late 2014. When the front of the lava complex moved onto the middle and lower slope of the volcano, PDC events were initially replaced by simple rock falls. Inflation of the upper part of the lava complex began in mid-2014 when the movement of the lava flow front stagnated. The inflation was associated with hybrid seismic events and frequent partial collapses of the upper part of the lava complex, generating PDC events with long travel distances. From mid-September 2014, new lobes repeatedly appeared near the summit and collapsed. Cyclic vulcanian events began in August 2015 when hybrid events peaked, and continued >1.5years (vulcanian stage). These events sometimes triggered PDCs, whose deposits contained vesiculated lava fragments. The distribution of PDC deposits, which extended over time, mostly overlapped in areal extent with that of the 9th–10th century eruption. Eruption volumes were estimated based on measurements with a laser distance meter during 6 periods, digital surface model (DSM) analysis of satellite images during one period, and the cumulative number of seismically detected PDC events, assuming a constant volume of each PDC event. The total volume of eruption products reached about 0.16km3 DRE as of the end of 2015. The lava discharge rate was largest during the initial stage (>7m3/s) and decreased exponentially over time. The discharge rate during the vulcanian stage was ≪1m3/s. The trend of decreasing discharge rate is in harmony with that of ground deflation recorded by a GPS measurement. The chemical composition of lava slightly evolved with time. Cyclic vulcanian events may have been triggered by limited degassing conditions in the upper conduit and by unloading of the conduit by lava dome collapses.

Predicting the end of lava flow-forming eruptions from space

Although the volcanological community places great emphasis on forecasting the onset of volcanic eruptions, knowing when an effusive eruption will end is just as important in terms of mitigating hazards. Wadge (J Volcanol Geotherm Res 11:139–168, 1981) postulated that the onset of an episodic, lava flow-forming basaltic eruption is characterized by a rapid increase in effusion rate to a maximum, before decaying over a longer period of time until the eruption ends. We used thermal infrared remote-sensing data acquired by NASA’s MODerate Resolution Imaging Spectroradiometer (MODIS) to derive time-averaged discharge rate (TADR) time series using the method of Harris et al. (J Geophys Res 102(B4):7985–8003, 1997) for 104 eruptions at 34 volcanoes over the last 15 years. We found that 32 eruptions followed the pattern described by Wadge (J Volcanol Geotherm Res 11:139–168, 1981). Based on the MODIS-derived maximum lava discharge rate and a decay constant that best fits the exponential waning phase (updated as each new MODIS TADR observation is added to the time series), the time at which the discharge equals zero, and thus the point at which effusion ends, can be predicted. The accuracy of the prediction improves with the number of data points so that, in the ideal case, the end of effusion can be retro-casted before half of the eruption duration has passed. This work demonstrates the possibility of predicting when an eruption will end using satellite-derived TADR time series acquired in near real time during that eruption. This prediction can be made after an eruption has reached its maximum lava discharge rate and the waning phase of the Wadge trend has begun. This approach therefore only applies to the case of eruption from a chamber undergoing an elastic release of energy during lava flow emplacement, and we provide examples of eruptions where it would not be applicable.

Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)

Basaltic magma chambers are often characterized by emptying and refilling cycles that influence their evolution in space and time, and the associated eruptive activity. During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system (>240×106 m3) and resulted in collapse of the 1-km-wide summit crater. Following these major events, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composition, and lava chemistry), we here show that the progressive migration of magma from a deeper (below sea level) storage zone gradually rejuvenated and pressurized the above-sea-level portion of the magmatic system consisting of a vertically-zoned network of relatively small-volume magma pockets. Continuous inflation provoked four small (<5×106 m3) eruptions from vents located close to the summit cone and culminated, during August–October 2015, with a chemically zoned eruption that erupted 45±15×106 m3 of lava. This two-month-long eruption evolved through (i) an initial phase of waning discharge, associated to the withdrawal of differentiated magma from the shallow system, into (ii) a month-long phase of increasing lava and SO2 fluxes at the effusive vent, coupled with CO2 enrichment of summit fumaroles, and involving emission of less differentiated lavas, to end with, (iii) three short-lived (∼2 day-long) pulses in lava and gas flux, coupled with arrival of cumulative olivine at the surface and deflation.The activity observed at Piton de la Fournaise in 2014 and 2015 points to a new model of shallow system rejuvenation and discharge, whereby continuous magma supply causes eruptions from increasingly deeper and larger magma storage zones. Downward depressurization continues until unloading of the deepest, least differentiated magma triggers pulses in lava and gas flux, accompanied by rapid contraction of the volcano edifice, that empties the main shallow reservoir and terminates the cycle. Such an unloading process may characterize the evolution of shallow magmatic systems at other persistently active effusive centers.

Elevated gas flux and trace metal degassing from the 2014–2015 fissure eruption at the Bárðarbunga volcanic system, Iceland

AbstractThe 2014 Bárðarbunga rifting event in Iceland resulted in a 6‐month long eruption at Holuhraun. This eruption was characterized by high lava discharge rate and significant gas emission. The SO2 flux for the first 3 months was measured with satellite sensors and the petrologic method. High‐resolution time series of the satellite data give 1200 kg/s that concurs with 1050 kg/s obtained from melt inclusion minus degassed lava sulfur contents scaled to the mass of magma produced. A high‐purity gas sample, with elevated S/Cl due to limited chlorine degassing, reveals a similar degassing pattern of trace metals as observed at Kīlauea (Hawai'i) and Erta Ale (Ethiopia). This suggests a common degassing mechanism at mantle plume‐related volcanoes. The trace metal fluxes, calculated from trace element to sulfur ratios in the gas sample and scaled to the sulfur dioxide flux, are 1–2 orders of magnitude stronger at Holuhraun than Kīlauea and Erta Ale. In contrast, volcanoes at convergent margins (Etna and Stromboli, Italy) have 1–2 orders of magnitude higher trace element fluxes, most likely caused by abundant chlorine degassing. This emphasizes the importance of metal degassing as chlorine species. Short‐lived disequilibria between radon daughters, 210Pb‐210Bi‐210Po measured in the gas, suggest degassing of a continuously replenished magma batch beneath the eruption site. Earlier and deep degassing phase of carbon dioxide and polonium is inferred from low (210Po/210Pb) in the gas, consistent with magma transfer rate of 0.75 m/s.