Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that ...resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation rates, the stability of deep magma bodies is governed by the magma-host rock density contrast and the magma body thickness. During eruptions, inelastic processes including magma mush erosion and thermal effects, can form a sustained channel that supports magma flow, driven by the pressure difference between the magma body and surface vents. At failure onset, it may be difficult to forecast the final eruption volume; pressure in a magma body may drop well below the lithostatic load, create under-pressure and initiate a caldera collapse, despite only modest precursors.
The 39-day long eruption at the summit of Eyjafjallajökull volcano in April-May 2010 was of modest size but ash was widely dispersed. By combining data from ground surveys and remote sensing we show ...that the erupted material was 4.8±1.2·10¹¹ kg (benmoreite and trachyte, dense rock equivalent volume 0.18±0.05 km³). About 20% was lava and water-transported tephra, 80% was airborne tephra (bulk volume 0.27 km³) transported by 3-10 km high plumes. The airborne tephra was mostly fine ash (diameter <1000 µm). At least 7·10¹⁰ kg (70 Tg) was very fine ash (<28 µm), several times more than previously estimated via satellite retrievals. About 50% of the tephra fell in Iceland with the remainder carried towards south and east, detected over ~7 million km² in Europe and the North Atlantic. Of order 10¹⁰ kg (2%) are considered to have been transported longer than 600-700 km with <10⁸ kg (<0.02%) reaching mainland Europe.
In April and May 2010 the Icelandic volcano Eyjafjallajökull experienced an explosive eruption that led to substantial ashfall across the central-southern parts of the island. The resulting ash ...deposits covered Eyjafjallajökull, Mýrdalsjökull and parts of Vatnajökull ice caps. In order to quantify the influence of these deposits on albedo, we analyzed albedo evolution across Eyjafjallajökull and Mýrdalsjökull ice caps over the period 2001–2016 using the MOD10A1 and MCD43A3 data products of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Terra and Aqua satellites. A geostatistical model with a daily temporal resolution was used to delineate areas on the ice caps that show distinct ash cover-related albedo reductions over the post-eruption period. Results suggest that despite an overall decrease of the ash cover-related albedo reductions with time, noticeable albedo reductions persist on both, Eyjafjallajökull and Mýrdalsjökull over the entire post-eruption period. These reductions show means of 0.19 ± 0.11 and 0.17 ± 0.10, respectively, and occur most prominently during the summer seasons. Persistent albedo reductions are in agreement with and limited to areas of higher ash deposition during the volcanic eruption such as the southern parts of Eyjafjallajökull and Mýrdalsjökull ice caps. In addition, redistribution of Eyjafjallajökull ash deposited on the lowlands in southern Iceland contributed to dust storm events in the years after the eruption and caused additional albedo reductions.
•Persistent albedo reduction across southern Eyjafjallajökull and Mýrdalsjökull•Persistent albedo reduction in areas of highest ashfall especially at convex terrains•Ash influence-related albedo reduction across all other areas diminishes over time
Alteration of basaltic glass and in situ mineral growth are fundamental processes that influence the chemical and material properties of Earth's oceanic crust. These processes have evolved at the ...basaltic island of Surtsey (SW Iceland) since eruptions terminated in 1967. Here, subaerial and submarine lapilli tuff samples from a 192 m-deep borehole drilled in 2017 (SE-02b) are characterized through petrographic studies, X-ray powder diffraction analyses, and SEM-EDS imaging and chemical analyses. The integrated results reveal (i) multi-stage palagonitization processes in basaltic glass and precipitation of secondary minerals from matrix pore fluids, (ii) multi-stage crystallization of secondary phillipsite, analcime and Al-tobermorite in the vesicles of basaltic pyroclasts and (iii) variations in palagonitization processes as a function of thermal and hydrological domains. Although temperature appears to be an important factor in controlling rates of secondary mineralization, the chemistry of original basaltic components and interstitial fluids also influences reaction pathways in the young pyroclastic deposits. The integration of systematic mineralogical analyses of the 50-year-old tuff from one of the most carefully monitored volcanic sites on Earth, together with temperature monitoring in boreholes since 1980, provide a reference framework for evaluating mineralogical evolution in other Surtseyan-type volcanoes worldwide.
Detailed observations of the 2010 Eyjafjallajökull eruptions in Iceland show seismic activity propagating vertically through the entire crust during a ten‐week period of volcanic unrest comprising ...multiple eruption episodes. Systematic changes in magma chemistry suggest a complex magmatic plumbing system, tapping several accumulation zones at different depths containing magma of differing ages and compositions. During the eruption, a systematic downward propagation of seismicity through the crust and into the upper mantle to ∼30 km depth occurred in a series of steps, each of which preceded an explosive surge in eruption rate. Here we show that the sequence of seismicity and eruptive activity may be explained by the downward propagation of a decompression wave that triggers magma release from progressively deeper sills in the crust. Comparing observations of the downward‐propagating seismicity with the decompression of a series of model elastic sills suggests that each sill was 1–10 km3 in size.
Key Points
Seismicity propagates downwards during eruption; swarms precede eruptive surges
Melt from depth is mobilized by depressurization of the shallow plumbing system
Modeling of elastic sills supports our proposed mechanism
The emergence and growth of Surtsey during volcanic activity in 1963–1967, from an oceanic depth of 130 m off the south coast of Iceland, remains one of the best-documented island-forming eruptions ...to date. By extracting information from seismic bulletins and analyzing archived analog seismic data, principally from SID, the most sensitive station in the seismic network existing at the time (131 km from Surtsey), we address key questions on precursors, timing of eruption onset, and duration of the submarine phase. We estimate the magnitude of completeness for earthquakes at Surtsey to have been M
L
= 2.5. Several seismic events of magnitude M
L
< 3 in November 3–10, 1963, with epicentral distance fitting with Surtsey are considered to be precursory earthquakes. Continuous tremor of dominant frequency 1–2 Hz, starting in the early afternoon of November 12, is considered to mark the onset of the submarine eruption, about 40 h before the start of subaerial eruption at 06:30 on November 14. The number of earthquakes larger than the threshold magnitude of 2.5 detected in 1963–1966 was 123, with the largest being of magnitude 4.5. Six earthquakes ranging in magnitude between 3.7 and 4.5 were felt in Heimaey, 22 km to the NE of Surtsey. Changes in vent location occurred five times in 1964–1966. Significant earthquake activity after the eruption start occurred in swarms considerably stronger than observed at the start. These swarms preceded vent migration and lasted days to weeks, apparently caused by intrusive activity prior to eruption at the new vents.
The morphology of glaciovolcanoes is considered one of the distinctive characteristics of their ice-confining eruption environment. However, a thorough morphometric analysis of a large number of ...glaciovolcanic edifices has never been performed. Based on semi-automatic geomorphometric mapping, we present a morphometric database of 155 glaciovolcanic edifices within the Icelandic neovolcanic zones, formed during the last 0.78 Ma. This database enables a comprehensive analysis of the morphometric diversity of a large suite of glaciovolcanic edifices. Sheet-like formations, however, are not considered due to lack of data. Using three planimetric measurements (basal length, average basal width and average summit plateau width) and their ratios, three main morphometric groups can be distinguished in a ternary diagram: 1) conical edifices with no or small summit plateaus, 2) linear ridges and 3) flat-topped edifices (subdivided into equidimensional and elongated). All three groups contain edifices with and without lava caps. These morphometric groups can be fitted to the commonly accepted terminology for cone/mound, tindar and tuya. However, since lava caps occur in all morphometric groups, a grouping based on its existence is not practical. This suggests that by adding the descriptor “lava-capped” to any of the three classes may be a useful way to refine the classification. Based on the ternary diagram, ridges are the most morphometrically distinct glaciovolcanic edifice, because of their extreme elongation, followed by flat-topped edifices and finally conical edifices. However, morphometric parameters cannot be used singlehanded to identify glaciovolcanic edifices from other types of volcanic edifices such as composite volcanoes, shields or submarine volcanoes, and should always be complemented with other observations. The glaciovolcanic edifice volumes range from 0.15 · 10−2 km3 to 32 km3. Conical edifices are the smallest (<0.1 km3) and the group of flat-topped edifices has the largest edifices (>1 km3). Overall, with growth three morphological evolutions can be considered: (A) an initial eruptive fissure concentrates into one vent generating an equidimensional edifice, that either can be a conical or a flat-topped edifice; (B) the edifice maintains its elongation, suggesting that a fissure is the dominating vent structure, and during continued eruption develops significant summit plateaus, generating elongated flat-topped edifices; and (C) the edifice increases in elongation because the fissure lengthens during the eruption, and a plateau-building stage does not occur, producing increasingly elongated ridges.
•We present a morphometric database of 155 Icelandic glaciovolcanic edifices.•This enables analysis of the morphometric diversity of glaciovolcanic edifices.•Three main morphometric groups can be distinguished in a ternary diagram.•1) conical edifices 2) linear ridges and 3) flat-topped edifices•Morphometry cannot be used singlehanded to identify glaciovolcanic edifices.
We report how data from satellite and aerial synthetic aperture radar (SAR) observations were integrated into monitoring of the 2014–2015 Holuhraun eruption in the Bárðarbunga volcanic system, the ...largest effusive eruption in Iceland since the 1783–84 Laki eruption. A lava field formed in one of the most remote areas in Iceland, after the propagation of a ∼50 km-long dyke beneath the Vatnajökull ice cap, where the Bárðarbunga caldera is located. Due to the 6 month duration of the eruption, mainly in wintertime, daily monitoring was particularly challenging. During the eruption, the European volcanological project FutureVolc was ongoing, allowing collaboration of many European experts on volcano monitoring activities. Icelandic volcanoes are also a permanent Supersite within the Geohazard Supersites and Natural Laboratories (GSNL) initiative, with support from the Committee on Earth Observation Satellite (CEOS) in the form of a large collection of SAR images. SAR data were acquired by Cosmo-SkyMed (CSK) and TerraSAR-X (TSX) satellites and complemented by aerial SAR images. The large set of SAR satellite data significantly contributed to the daily monitoring during the unrest at Bárðarbunga caldera, the Holuhraun eruption and the year following the eruption. Detection of surface changes using both SAR amplitude and phase information was conducted throughout the whole duration of the volcano-tectonic event, and in the following months, to quantify and track the evolution of volcanic processes at Holuhraun and geothermal activity at Bárðarbunga volcano. Combination of SAR data with other data sets, e.g., satellite optical images and geodetic Global Positioning System (GPS) measurements, was essential for the evaluation of the volcanic hazard in the whole area. International collaboration within the FutureVolc project formed the basis for successful analyses and interpretation of the large SAR data set. Information was provided at Scientific Advisory Board meetings of the Icelandic Civil Protection and used in decision-making, as well as for supporting field-deployment and air-based surveys.
Real-time monitoring of volcanic ash plumes with the aim to estimate the mass eruption rate is crucial for predicting atmospheric ash concentration. Mass eruption rates are usually assessed by 0D and ...1D plume models, which are fast and require only a few observational input parameters, often only the plume height. A model’s output, however, depends also on the plume height data handling strategy (sampling rate, gap reconstruction methods and statistical treatment), especially in long-term eruptions with incomplete plume height records. To represent such an eruption, we used Eyjafjallajökull 2010 to test the sensitivity of six simple and two explicitly wind-affected plume models against 22 data handling strategies. Based on photogrammetric measurements, the wind deflection of the plume was determined and used to recalibrate radar-derived height data. The resulting data was then subjected to different data handling strategies, before being used as input for the plume models. The model results were compared to the erupted mass measured on the ground, allowing us to assess the prediction accuracy of each combination of data handling strategy and model. Combinations that provide highest prediction accuracies vary, depending on data coverage, eruption intensity and fragmentation mechanism. However, for this type of moderate-to-weak eruption (VEI 3 in terms of maximum intensity), the most important factor was found to be the prevailing wind speed. When wind speeds exceed 20 m/s, most combinations of strategies and models provide predictions that underestimate the erupted mass by more than 40%. Under such conditions, the optimal choice of data handling strategy and plume model is of particular importance.
Fissure eruptions are associated with lava fountains which often show complex distinct venting activity in pulsating form, and the development of characteristic morphological features such as scoria ...or spatter cones. Most morphological studies are based on observations of old structures and are not related to direct observations and systematic records of vent activity. The 2014–2015 Holuhraun eruption site, Iceland, offered an exceptional opportunity to study the location and evolution of these cones and their relationship to venting dynamics in unprecedented detail. Here we analyze records from lava fountain activity at distinguished vents, captured during the 2014–2015 Holuhraun eruption, and compare them with the morphology of spatter cones that developed. We conducted a fieldwork mapping project combining terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) aerophoto techniques to characterize the cone morphologies. We recorded videos of the eruption and used edge detection and particle image velocimetry to estimate venting heights and particle velocities. We find that the number of active vents producing lava fountains decreases from 57 along the whole line of fire to 10 lava fountains at distinct vents during the first 5 days of the eruption. We suggest that this happens by channeling the magma supply in the subsurface developing conduits. Thereby we see that at the locations where spatter cone morphology developed, the strongest and the highest lava fountains with high ejection velocities were recorded on the very first days of the eruption. In addition, the sites that eventually developed moderate or weak cone morphologies were identified as less active lava fountain locations during the early stage of the eruption. The comparison of our topographic datasets shows that the spatter cones remained similar in shape but increased in size as the eruption progressed. In addition, we suggest that the observed changes in morphology may have affected lava ponding in the crater, which in turn strongly influenced the lava fountain heights. Our results improve the general understanding of landscape evolution in rift zones and demonstrate the close relationship between cone morphology and lava fountain activity at the onset of an eruption.
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