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By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use. Home Earth Environment. Two people walk as lava spews from a volcano on the Canary island of La Palma, Spain in the early hours of Saturday Sept. A volcano in Spain's Canary Islands is keeping nerves on edge several days since it erupted, producing loud explosions, a huge ash cloud and cracking open a new fissure that spewed out more fiery molten rock.
The prompt evacuations are credited with helping avoid casualties but scientists say the lava flows could last for weeks or months. This document is subject to copyright.
Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Synthesizing nanomaterials from nature's blueprints 9 hours ago. Sections U. Science Technology Business U. Volcanic ash cloud halts flights to and from Spanish island. September 26, GMT. A volcano in Spain's Canary Islands is keeping nerves on edge several days since it erupted, producing loud explosions, a huge ash cloud and cracking open a new fissure that spewed out more fiery molten rock.
Connect with the definitive source for global and local news. The Associated Press. All rights reserved. In the first two days, the eruption formed ice cauldrons 11 over the vents Fig. The main activity on 14 April was in the south ice cauldron, but moved to the west cauldron on 15 April where it remained until the end of the eruption Fig. Part of the erupted material was water-transported pyroclasts, essentially identical to the air transported tephra.
This phase is conveniently divided into 14—16 April when the tephra formed a well-defined sector towards the east and to early 18 April, when northerly winds carried the tephra southwards Figs.
The composition of the erupted melt is predominantly evolved benmoreite Fig. Airborne ash was detected over 1. Low-discharge effusive phase 18 April — 4 May. Satellite-detected ash spread out over 0. Second explosive phase 5—17 May. The onset of this phase is marked by abrupt rejuvenation of explosive activity that coincides with sudden change in melt composition from benmoreite to trachyte Fig. The magma output was variable, shifting between periods of relatively low 0. Final phase 18—22 May , the period when the eruption declined and eventually continuous activity stopped.
A steam plume from the summit crater persisted for months after the eruption. Inset on right: an airborne synthetic aperture radar image from 15 April. The location and form of subsurface volcanic conduits is highly schematic. The graphs are based on tephra sampling Figs. The groundmass glass falls into distinctive compositional groups, designated as benmoreite, trachyte and rhyolite. The relative abundance of more evolved groundmass glass compositions highlighted in the initial and second explosive phases is given by the percentage above the black squares.
Shifts in the melt composition are in phase with shifts in magma discharge and style of activity. The inset shows the concentration on a section S-N over the Faroe Islands. On the graph H marks the position of the sampling locality at Hoyvik. One image is used per day but data for some days are missing, usually because of unfavorable cloud cover.
The sectors identified for each image denote the area over which ash can be detected on the images and no distinction is made between dense and highly diluted clouds.
Isopach maps thickness in cm of tephra distribution during Phase I the first explosive phase 14—18 April and the whole eruption c. The nine localities where grain size analysis was carried out and the three zones on land I—III used to estimate the grainsize distribution for 14—16 April are shown.
The most intense fallout occurred from on 14 April into the early hours of 15 April. Daily ash mass loadings that exceed 0.
No attempt is made to indicate the amount of ash retrieved or the concentration, rather the plot shows the spatial distribution of the ash over the domain considered. The tephra from 14—16 April is estimated seperately since it forms a well defined sector and was responsible for the first ash transported to Europe.
The volume within Iceland is found by direct integration of the onland part of the maps in Fig. The volume outside Iceland is found by integrating the exponential curves e. The volume is found by integrating the exponential curves for 14—16 April and the whole eruption from the point on the square root of area axis on a out to infinity, using eqs. On the basis of the magma petrology and its evolution with time 12 and the deformation and seismicity before and during the eruption 8 , the course of events has been explained by injection of basaltic magma from the mantle and its mixing and mingling with pre-existing silicic magma residing in the crust under the volcano The lack of injection of new basalt in late May is considered to have stopped the eruption, not the exhaustion of silicic magma in the crust On 14—16 April ash was carried eastward by westerly upper-tropospheric winds, while on 17 April northerly winds directed the plume to the south Fig.
Ash clouds were reported in Northern and Western Europe in the period 15—21 April and again between 6 and 17 May 6 , 7. The strong northwesterly flow persisted until 24 April, when it was replaced by weaker westerly flow Fig. In early May, when the vigour of the eruption again intensified, the atmospheric flow turned northwesterly and remained through the latter half of May although the strength of the air flow gradually weakened.
The eruption plume was directed east- or southwards for 28 out of 39 days of sustained activity. The weather situation during the spring of was indeed rather unusual with frequent northwesterly winds and a large deviation from the climatological mean atmospheric circulation The persistent northwesterly winds contributed strongly to the dispersal of ash clouds to Europe. This value is obtained by combining isopach map integration on land with integrating a piecewise exponential model of decline of thickness with distance for the area south of Iceland see Methods.
When taking into account the water transported tephra and the lava flow, the total mass erupted is 4. The partitioning of the erupted material with total volumes and mass are given in Table 1. Estimates of production rates of tephra for each day of the eruption, main direction of dispersal estimated from ground observations and satellite images and grain size characteristics, when available, are given in Table 2.
The 14—16 April tephra fall sector is well constrained. By integrating the model of piecewise exponential decline in tephra thickness with distance Fig. The satellite data Fig.
Ash transported beyond that distance was of order 0. During 5—17 May, ash transport in any single phase probably never reached the intensity of 14—16 April. On the basis of analysis from eight sampling localities Fig. Considering that the total mass of airborne tephra erupted in 14—16 April was 1. Comparable whole deposit grain size analyses have not yet been completed for later phases of the eruption. During high magma discharge in Phase III 5—17 May , tephra was sampled in a systematic manner with a number of traps around the volcano.
In Table 2 , results of grain size analysis of samples from traps located on the dispersion axis or very close to it are included. This is slightly lower, but comparable to that of the initial phase of the eruption. The clast populations Fig. Analyses of grain morphology for the different phases indicate that phreatomagmatic activity was influential in the first explosive phase, evidence of both magmatic and phreatomagmatic fragmentation were found during the second weak phase, while in the third, explosive phase, magmatic fragmentation had become dominant Dellino et al.
The prolonged duration Fig. It is likely that the high proportion of fine-grained ash was of major importance, allowing a fraction of the finest ash to disperse widely. However, the abundance of very fine ash beds often loaded with ash aggregates on land in Iceland testifies to the importance of aggregation in explaining the heavy fallout observed in the proximity of source vents 24 , 25 , At larger distances, sedimentation of the very fine ash was much slower within the widespread diluted ash clouds over Europe Fig.
However, aggregation is also important during sedimentation in the far-field regions as clearly indicated by the observations in the UK It should be noted that the synoptic meteorology also influences the ash sedimentation rate, as indicated by lidar observations in the UK and Germany showing the ash cloud to be a sloping structure and parallel to a weather front Application of satellite data to infer mass loading of the atmosphere during volcanic eruptions holds great potential in enhancing aviation safety and successful routing of aircraft in the vicinity of ash clouds.
Stohl et al 7. A likely reason for such a discrepancy might be that satellite retrievals for mass concentration do not work in dense, optically opaque eruptions clouds 28 and may therefore not provide reliable estimates close to a volcano where aggregation-enhanced settling can be a major factor.
Helens in dacite , El Chichon in trachyandesite 23 and the phreatoplinian C phase of the Askja eruption in rhyolite 29 and considerably larger than in e. Helens where elutriation of ash derived from pyroclastic flows may be partly responsible for the large percentage of very fine ash In Europe, a number of Italian volcanoes have and will in the future produce intermediate to silicic explosive eruptions with large amounts of fine ash.
However, in terms of eruption frequency and potential for disruption, Icelandic volcanoes are the most potent 30 , Upper tropospheric winds are usually most influential in determining the direction of dispersal of tephra from Icelandic eruptions, tending to have a component of eastbound flow, with northwesterly winds slightly less common than southwesterlies Quantitative analysis of the probabilities for magnitude and duration of explosive eruptions in Iceland is beyond the scope of this study.
Southwesterly upper tropospheric winds were dominant during these events carrying tephra towards northeast. Hence, only minor disruption to air traffic occurred and the busy air routes in central and western Europe were not affected. Iceland, unpublished data. Distal fallout was observed in at least the British Isles and Norway University of Edinburgh, unpublished data , yet disruption to air traffic was minor compared to the previous year, despite higher eruption rates and total volume.
The relatively short duration and absence of strong upper tropospheric and stratospheric winds prevented dispersal at the scale observed in April—May This illustrates the complicated nature of the hazard caused by ash dispersal from volcanic eruptions. Our results are based on measurements of tephra thickness on land in Iceland, records of tephra fallout outside Iceland, reconstruction of plume dispersal from satellite images, monitoring and mapping of ice melting, eruption plume height, grain size analysis of tephra, tephra grain morphology and chemistry of the erupted products.
Monitoring of vents and ice cauldron formation Figs. Ice melting rates were estimated from 1 growth of ice cauldrons as measured from the SAR images, 2 evolution of crevasse patterns and other subsidence structures around the ice cauldrons from photographs and the SAR images and 3 mapping of ice surface with GPS in July The tephra on land consisted of airfall dominant and water transported minor.
For the airfall tephra thicknesses were measured in about locations and used to construct the isopach maps.
Tephra volume within the mapped area was found by directly integrating the isopach maps. Volume outside the 0. Separate isopach maps were constructed for the east-directed sector formed on 14—16 April, the south-directed sector formed on 17 April and for the whole deposit Fig. The volume of tephra deposited on land for the period 18 April—22 May was obtained by subtracting the volume erupted on 14—18 April from the whole-deposit map.
The partitioning between 18 April—4 May, 5—17 May and 18—22 May is estimated from 1 the integrated plume height over the two periods eq. We assume piecewise exponential decline with distance 37 , 38 , The form of the dotted contours outside the coast on Fig. Error estimates for material deposited outside Iceland are based on a minimum extrapolation that still allows for some material to be transported past the Faroe Islands and a maximum estimate that still limits fallout equivalent to 0.
The same value is used for water-transported tephra. Total grain size partitioning for the 14—16 April east-directed sector was done by defining the three zones on land Fig.
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