Limits...
First recorded eruption of Nabro volcano, Eritrea, 2011.

Goitom B, Oppenheimer C, Hammond JO, Grandin R, Barnie T, Donovan A, Ogubazghi G, Yohannes E, Kibrom G, Kendall JM, Carn SA, Fee D, Sealing C, Keir D, Ayele A, Blundy J, Hamlyn J, Wright T, Berhe S - Bull Volcanol (2015)

Bottom Line: It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar.The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight.The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1RJ UK ; Department of Earth Sciences, Eritrea Institute of Technology, PO Box 12676, Asmara, Eritrea.

ABSTRACT

We present a synthesis of diverse observations of the first recorded eruption of Nabro volcano, Eritrea, which began on 12 June 2011. While no monitoring of the volcano was in effect at the time, it has been possible to reconstruct the nature and evolution of the eruption through analysis of regional seismological and infrasound data and satellite remote sensing data, supplemented by petrological analysis of erupted products and brief field surveys. The event is notable for the comparative rarity of recorded historical eruptions in the region and of caldera systems in general, for the prodigious quantity of SO2 emitted into the atmosphere and the significant human impacts that ensued notwithstanding the low population density of the Afar region. It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar. The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight. The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor. Substantial infrasound was recorded at distances of hundreds to thousands of kilometres from the vent, beginning at the onset of the eruption and continuing for weeks. Analysis of ground deformation suggests the eruption was fed by a shallow, NW-SE-trending dike, which is consistent with field and satellite observations of vent distributions. Despite lack of prior planning and preparedness for volcanic events in the country, rapid coordination of the emergency response mitigated the human costs of the eruption.

No MeSH data available.


Related in: MedlinePlus

Left panel shows a differential analysis of backscattered SAR amplitude for the Nabro area based on analysis of two TerraSAR-X scenes from 11 June 2010 (pre-eruption) and 1 July 2011. The normalised difference of the amplitude images is computed using the formula: Delta_amp = 2 × (amp_1 − amp_2) / (amp_1 + amp_2). Red areas indicate decreased SAR amplitude and topographic smoothing (at the cm scale), while blue areas correspond to increased SAR amplitude and increased surface roughness. The upper-right panel shows the Nabro caldera and 2011 lava flow. The lower-right panel shows the corresponding topography. Coloured triangles indicate different generations of eruptive vents identified from time series analysis of SAR and thermal imagery (Fig. 10)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4562108&req=5

Fig2: Left panel shows a differential analysis of backscattered SAR amplitude for the Nabro area based on analysis of two TerraSAR-X scenes from 11 June 2010 (pre-eruption) and 1 July 2011. The normalised difference of the amplitude images is computed using the formula: Delta_amp = 2 × (amp_1 − amp_2) / (amp_1 + amp_2). Red areas indicate decreased SAR amplitude and topographic smoothing (at the cm scale), while blue areas correspond to increased SAR amplitude and increased surface roughness. The upper-right panel shows the Nabro caldera and 2011 lava flow. The lower-right panel shows the corresponding topography. Coloured triangles indicate different generations of eruptive vents identified from time series analysis of SAR and thermal imagery (Fig. 10)

Mentions: X-band SAR images can map geological structures down to the decametric scale. However, geometric distortions associated with complex topography complicate their interpretation. At large scale (from tens of pixels across), the average amplitude of the SAR images is mostly sensitive to the local illumination angle and therefore to slope. Due to the inclined line-of-sight direction of SAR images (usually about 30° from the vertical), systematic geometric distortions and radiometric variations are evident in scenes with topographic relief: while slopes facing towards the sensor appear bright and compressed, slopes inclined away from the satellite are darker and stretched. SAR amplitude images thus provide a qualitative characterisation of topographic changes (Fig. 2).Fig. 2


First recorded eruption of Nabro volcano, Eritrea, 2011.

Goitom B, Oppenheimer C, Hammond JO, Grandin R, Barnie T, Donovan A, Ogubazghi G, Yohannes E, Kibrom G, Kendall JM, Carn SA, Fee D, Sealing C, Keir D, Ayele A, Blundy J, Hamlyn J, Wright T, Berhe S - Bull Volcanol (2015)

Left panel shows a differential analysis of backscattered SAR amplitude for the Nabro area based on analysis of two TerraSAR-X scenes from 11 June 2010 (pre-eruption) and 1 July 2011. The normalised difference of the amplitude images is computed using the formula: Delta_amp = 2 × (amp_1 − amp_2) / (amp_1 + amp_2). Red areas indicate decreased SAR amplitude and topographic smoothing (at the cm scale), while blue areas correspond to increased SAR amplitude and increased surface roughness. The upper-right panel shows the Nabro caldera and 2011 lava flow. The lower-right panel shows the corresponding topography. Coloured triangles indicate different generations of eruptive vents identified from time series analysis of SAR and thermal imagery (Fig. 10)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4562108&req=5

Fig2: Left panel shows a differential analysis of backscattered SAR amplitude for the Nabro area based on analysis of two TerraSAR-X scenes from 11 June 2010 (pre-eruption) and 1 July 2011. The normalised difference of the amplitude images is computed using the formula: Delta_amp = 2 × (amp_1 − amp_2) / (amp_1 + amp_2). Red areas indicate decreased SAR amplitude and topographic smoothing (at the cm scale), while blue areas correspond to increased SAR amplitude and increased surface roughness. The upper-right panel shows the Nabro caldera and 2011 lava flow. The lower-right panel shows the corresponding topography. Coloured triangles indicate different generations of eruptive vents identified from time series analysis of SAR and thermal imagery (Fig. 10)
Mentions: X-band SAR images can map geological structures down to the decametric scale. However, geometric distortions associated with complex topography complicate their interpretation. At large scale (from tens of pixels across), the average amplitude of the SAR images is mostly sensitive to the local illumination angle and therefore to slope. Due to the inclined line-of-sight direction of SAR images (usually about 30° from the vertical), systematic geometric distortions and radiometric variations are evident in scenes with topographic relief: while slopes facing towards the sensor appear bright and compressed, slopes inclined away from the satellite are darker and stretched. SAR amplitude images thus provide a qualitative characterisation of topographic changes (Fig. 2).Fig. 2

Bottom Line: It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar.The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight.The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1RJ UK ; Department of Earth Sciences, Eritrea Institute of Technology, PO Box 12676, Asmara, Eritrea.

ABSTRACT

We present a synthesis of diverse observations of the first recorded eruption of Nabro volcano, Eritrea, which began on 12 June 2011. While no monitoring of the volcano was in effect at the time, it has been possible to reconstruct the nature and evolution of the eruption through analysis of regional seismological and infrasound data and satellite remote sensing data, supplemented by petrological analysis of erupted products and brief field surveys. The event is notable for the comparative rarity of recorded historical eruptions in the region and of caldera systems in general, for the prodigious quantity of SO2 emitted into the atmosphere and the significant human impacts that ensued notwithstanding the low population density of the Afar region. It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar. The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight. The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor. Substantial infrasound was recorded at distances of hundreds to thousands of kilometres from the vent, beginning at the onset of the eruption and continuing for weeks. Analysis of ground deformation suggests the eruption was fed by a shallow, NW-SE-trending dike, which is consistent with field and satellite observations of vent distributions. Despite lack of prior planning and preparedness for volcanic events in the country, rapid coordination of the emergency response mitigated the human costs of the eruption.

No MeSH data available.


Related in: MedlinePlus