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Nabro eruption subdued but ongoing 21 June 2011

Posted by admin in activity reports, Africa, Eritrea, eruptions, Ethiopia, Nabro.
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Nabro eruption SO2 emissions 19 June 2011 (NASA/Aura/OMI)

Above. Nabro eruption SO2 emissions 19 June 2011 (NASA/Aura/OMI).

Overall the eruption of Nabro volcano in Eritrea seems to have been going through a quieter phase over the past two days, with rather small plumes (or none at all) visible in satellite images and little evidence of further explosive activity. Toulouse VAAC issued two advisories yesterday, the first at 1200 UTC reported ‘eruption mainly producing SO2’ with a small ash cloud at FL180 (18,000 feet/5,500 metres altitude) extending to the WSW/SW of the volcano, and the second at 1800 UTC reporting ‘eruption ongoing’ with no identifable ash emission: ‘only SO2 detected since 1230Z’. The sulphur dioxide emissions from Nabro have been on a very large scale: with reference to data from last week NASA reported that ‘On June 13, OMI captured high SO2 concentrations – exceeding thousands of Dobson units – from the eruption of Nabro (Eritrea) on June 12th. Total tonnage is estimated to exceed 1Tg’. There have of course been significant further SO2 emissions from Nabro since that report was written on 16 June. A gallery of Aura/OMI SO2 data for Afar showing the size and movement of the SO2 plume from Nabro can be viewed at NASA’s Goddard Space Flight Center global SO2 monitoring site. The image at the top of the post shows the SO2 plume detected by Aura’s OMI on 19 June 2011.

NASA satellite images from yesterday show the presence of a small plume over the seat of the eruption with no significant downwind emissions cloud visible. Below are images from Aqua (top) and Terra (bottom): in each case click on the image to go to the original at the NASA Rapidfire site.

Nabro volcano, Eritrea, 20 June 2011, 1050Z, 1px = 500m (NASA/Aqua)

Above. Nabro volcano, Eritrea, captured by NASA’s Aqua satellite on 20 June 2011, 1050Z. Scale: 1px = 500m.

Nabro volcano, Eritrea, 20 June 2011, 1050Z, 1px = 500m (NASA/Terra)

Above. Nabro volcano, Eritrea, captured by NASA’s Terra satellite on 20 June 2011, 0750Z. Scale: 1px = 500m.

A dark patch is visible on the surface to the SW of the volcano. The atmosphere is murky and it is difficult to see precisely what this is: it looks too fuzzy at the edges and too brown in colour to be a lava flow. Burnt vegetation? An ash deposit? Below is a close-up from the Terra image:

Nabro volcano, Eritrea, 20 June 2011, 0750Z, 1px = 250m (NASA/Terra)

Above. Nabro volcano, Eritrea, captured by NASA’s Terra satellite on 20 June 2011, 0750Z. Scale: 1px = 250m.

The human impact of the eruption is starting to become clearer, althouth reports from the area affected by the Nabro eruption have been hard to come by: even in this modern age communications can be difficult in this part of the world, the political character of the region tends not to encourage the free spread of information, and enduring tension between Ethiopia and Eritrea does not help. However, an article in the Ethiopian business newspaper Addis Fortune published yesterday (although the date ’12 June 2011′ confusingly appears at the top), ‘Eritrean volcano erupts economic mayhem for Ethiopia’, gives some idea of the problems the eruption has been causing across the area: flight delays and cancellations, potential health problems, and the poisoning by SO2 of local salt deposits formally exploited for consumption. The report also refers to ‘small eruptions in Afambo and Sireru areas’ as well as ‘the major eruption at Nabro’, although it is not clear precisely what’s being described here: earthquake activity, perhaps, rather than ‘eruptions’. The BBC, meanwhile, reports on appeals from aid organizations for help for the local people in Ethiopia: the inhabitants of villages in the Biddu region near the border ‘have been left without food and traditional springs and streams have been polluted’. Teshome Assefa of Save the Children tells the BBC, ‘Many community members and especially children are reported sick and in desperate need of medical attention’. It’s good to see the BBC reporting this, not so good that more than a week into the eruption they still haven’t got the name of the volcano right (‘Dubbi’ again). [Update: the BBC has corrected its report: Nabro. Thank you.]

In Eritrea itself official news on the eruption has been sparse. A brief bulletin was issued by the Eritrean Government Ministry of Information at the beginning of the eruption stating that there had been no loss of life or any other ill-effects. It seems, however, that there have been evacuations from the affected area within Eritrea, according to a further brief announcement made on 16 June:

Assab, June 16, 2011- The inhabitants of Afambo, Nebro and Sireru have disclosed that they have been moved to a safer location. Pointing out that there were occasional quakes in their areas, the inhabitants thanked the government for the fast relocation after the eruption, as a result of which there were no causalities [sic]. It is to be recalled that the eruption of June 12th around the areas of Afambo, Nebro and Sireru released large quantities of dust and smoke and the quake of 5.7 Richter it caused was felt in our region.

On the subject of earthquakes, the staff at the Observatoire Géophysique d’Arta (OGA) in Djibouti are clearly working very hard to keep track of the seismic activity in their northern neighbour and are providing the best coverage they can via their website. Today a strapline on their front page reports a decrease in tremors, with ‘few earthquakes on the Nabro volcano site’, but there are no details as yet.

News
Eritrean volcano erupts economic mayhem for EthiopiaAddis Fortune, 20 June 2011
Eritrea volcano ash hits Ethiopia villagers – BBC News, 20 June 2011

Information
Global Volcanism Program: Nabro – summary information for Nabro (0201-101)

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A look at Nabro’s history 19 June 2011

Posted by admin in Africa, Dubbi, Eritrea, Erta Ale, eruptions, Ethiopia, Nabro, volcanoes.
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Nabro is a little-known volcano. Its remote and inhospitable location has meant that very limited fieldwork has been carried out, and much of what we do know comes from remote sensing. Pierre Wiart and Clive Oppenheimer have analysed much of what is known about Nabro in a very useful paper published in the Bulletin of Volcanology in 2005: ‘Large magnitude silicic volcanism in north Afar: the Nabro Volcanic Range and Ma’alalta volcano’. The article is based upon remote sensing data and very limited fieldwork: thus eruptive sequences are established with reasonable clarity, but there is little dating information.

The authors note that much research on north Afar has focused on Quaternary basaltic volcanism, but that silicic volcanism in the region has been little considered, although ‘comparable volumes of silicic magma [compared with basaltic] have been erupted in the region’ (99). The Nabro Volcanic Range (NVR), which the authors identify as a single volcanic massif covering approximately 110 km and trending SSW-NNE from the Afar Depression to the Red Sea, is one significant but little-studied focus of silicic activity. The NVR encompasses the Edd Islands off the Red Sea coast, Dubbi volcano and the Edd lava field, Mabda volcano and the Bidu volcanic complex (Nabro and Mallahle calderas, and Bara Ale and Sork Ale volcanoes). The paired calderas of Nabro/Mallahle are described as follows:

Nabro has an 8 km diameter horseshoe-shaped caldera breached to the SW, and facing the 6 km diameter caldera of Mallahle. Nabro’s caldera contains a young volcanic centre, topped by two additional collapse craters. The flanks of the volcano are strongly dissected by gullies, whereas the inner walls of the caldera form 400-m high cliffs. The older of the two craters inside Nabro’s main caldera is also horseshoe-shaped and similarly open towards the SW. The walls of the innermost crater are 200 m high. (102)

Nabro and Mallahle are described as very similar in geomorphology and lithology, both being predominantly composed of trachytic lava flows. ‘On Nabro, geochemical and spectral evidence highlight at least two main periods of eruption of these flows’ (103). Both basaltic and silicic products are evident: ‘Whereas the main periods of edifice growth, collapse, and post-collapse volcanism have been characterized by silicic products, later volcanics of the Bidu Volcanic Complex include NNW-SSE basaltic lava flows, which streamed from vents or fissures located between the two calderas’. The authors suggest that these flows probably tapped separate source regions to those that fed the silicic volcanism, and note that ‘their superimposition on the boundary between the two calderas and orientation (i.e., perpendicular to the NVR axis), are enigmatic, but clearly not coincidental’ (103).

A very large eruption or eruptions in the past is evidenced by the presence of extensive ignimbrites, which the authors believe are ‘associated with collapses of both Nabro and Mallahle that formed the present day calderas’ (103). The age of these ignimbrites is unknown, but their spectral characteristics and state of preservation suggest their creation in a single eruptive sequence. The present-day ignimbrites cover an area of ~600 square kilometres, with a bulk volume tentatively estimated at 20 cubic kilometres. Prior to erosion of course a much greater bulk must have been present: the combined ignimbrite outcrop today lies within a 30 km radius of Mallahle, and the authors propose that if there was originally a single ignimbrite sheet extending this distance with a mean thickness of 40 m, the eruption magnitude may have exceeded 100 cubic kilometres (bulk volume):

These speculative upper and lower bounds on the ignimbrite volume [20-100 cubic kilometres] suggest an eruption (or eruptions) comparable in magnitude to the largest known historic eruption, that of Tambora in Indonesia in 1815, which expelled around 50 km3 of (dense rock equivalent) magma. This inference is compatible with the comparable caldera dimensions of Tambora (6 km), Nabro (8 km) and Mallahle (6 km). (107)

The total volume of the NVR is estimated by Wiart and Oppenheimer to be ~550 cubic kilometres, broadly comparable to that of Erta Ale. Overall they conclude that ‘the Erta’Ale range and NVR are, therefore, of broadly comparable area, volume, and age (Quaternary)’ but differ markedly in their composition and eruptive nature, with the Erta Ale range being composed of 91.4% basalt, 8.1% dark trachyte and 0.5% rhyolite, while the NVR is estimated as being 50% composed of trachyte and rhyolite (109). The authors suggest that the nature of the basement is responsible for this difference in composition, with the presence of continental crust on the margin of the Danakil region promoting the evolution of volatile-rich and ultimately explosive magmas.

The overall picture of Nabro is of a complicated and fascinating volcanic complex with a violent but varied history involving both explosive and effusive activity, some of the latter being possibly relatively recent in date, and set apart from the more northerly Afar volcanoes by its greater involvement of silicic and explosive magmas. The current eruption involved some initial explosive activity, but appears to have subsequently settled down to an intermittent and relatively low-level effusive event. It is to be hoped that clear images from the satellites will soon show the extent of the lava flows, and their sources. Given the evidence of Nabro/Mallahle’s history, it could be that their sources lie between the two calderas, replicating the behaviour which seems to have characterized the most recent activity at this obscure and intriguing volcano.

N.B. Several people have been in touch or left comments here to say that the Wiart & Oppenheimer paper is freely available via ‘a well-known file hosting site’. However, the paper in question is copyright Springer-Verlag 2004, and this blog respects copyright. Accordingly I won’t be providing the link here, and I respectfully ask that no-one else does so via the comments.

Reference
Pierre Wiart and Clive Oppenheimer, ‘Large magnitude silicic volcanism in north Afar: the Nabro Volcanic Range and Ma’alalta volcano’, Bulletin of Volcanology, vol. 67, no. 2 (2005), pp. 99-115 [DOI: 10.1007/s00445-004-0362-x]

Information
Global Volcanism Program: Nabro – summary information for Nabro (0201-101)

The Volcanism Blog

Stress change may provide clues to possible eruption locations 27 September 2010

Posted by admin in Africa, current research, Ethiopia, geoscience, volcano monitoring, volcanology.
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It’s all rifts, dykes and magmatic intrusions at Nature Geoscience right now. Along with the paper by Pallister et al on the Saudi quake swarms of 2009, the journal is hosting advanced online publication of a paper on a recent episode of dyke emplacement in the Afar region of north-eastern Africa: ‘Stress transfer between thirteen successive dyke intrusions in Ethiopia‘, by Ian J. Hamling et al.

The study looks at the emplacement of thirteen magmatic dykes in north-eastern Ethiopia between 2006 and 2009. A rift zone produced by the spreading boundary between the African and Arabian plates runs through this region; most such rift zones are situated on the ocean floor, so this remote area provides a valuable opportunity to study the processes associated with spreading plate boundaries without getting one’s feet wet. A team led by Ian Hamling of Leeds University measured changes in ground tension associated with each successive dyke emplacement, and found that subsequent eruptions were most likely in locations where the tension had been increased. Although the initial level of stress along a rift zone that becomes active is unknown, measurements of stress transfer will reveal whether eruptions in one location cause compressive stress change (clamping) or tensile stress change (unclamping) elsewhere. New dyking would be expected in locations subject to unclamping – in other words, where the ground has been stretched and is under increased tension – and the study shows that such is indeed the case: ‘the mean percentage of opening in unclamped sections of the rift has been 70%, with seven of 12 dykes having over 75% of their opening in regions unclamped by the previous intrusion’. The study concludes: ‘This result indicates that the stress change, induced by a new dyke, is a controlling factor on the location of future events and should therefore be incorporated into routine volcanic hazard monitoring’.

  • Ian J. Hamling, Tim J. Wright, Eric Calais, Laura Bennati & Elias Lewi, ‘Stress transfer between thirteen successive dyke intrusions in Ethiopia’, Nature Geoscience, published online: 26 September 2010 | doi:10.1038/ngeo967 [abstract]

News
Pinpointing where volcanic eruptions could strike – EurekAlert, 26 September 2010

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Ethiopian eruption: scientists on ground, shoes melt 13 July 2009

Posted by admin in activity reports, Africa, eruptions, Ethiopia, Manda Hararo.
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The first on-the-ground reports from the location of the recent eruption in the Manda Hararo volcanic field in Ethiopia have come from David Ferguson, a doctoral student in geology at the University of Oxford. He is reporting on his work on the volcanics of the Afar region in a series of blog postings for The Guardian.

Part 1 describes how he dropped everything and flew out there to take a look at what was going on, part 2 and part 3 (with photographs, including a wonderful aerial view of an eruptive fissure) see him reach the location courtesy of the Ethiopian Army, while part 4 (with more pictures) is an account of what he found once he got there with his Ethiopian colleagues:

As we reached the front of the lava flow one of our group, Dr Elias Lewi, walked out over its brittle surface, quickly turning back as his shoes begin to melt. Although only a few days old, the lava had a dark black crust and was deceptively similar to other, much colder flows. The real temperature was revealed by Talfan Barnie, a PhD student from Cambridge, who used a thermal infra-red camera to ‘see’ temperatures of up to 162C around the cracks and fractures across the flow surface.

We had to be very careful where we trod.

David Ferguson reports extensive (~10 square km) fresh lava flows from the eruption, about 3 m high at the margins, gas emissions, and a 5-kilometre fissure and central vent producing a small plume. There is more on Manda Hararo in the Global Volcanism Program’s Weekly Volcanic Activity Report for 1-7 July.

The Volcanism Blog

SI/USGS Weekly Volcanic Activity Report, 1-7 July 2009 13 July 2009

Posted by admin in activity reports, Africa, Batu Tara, Chaitén, Chile, Dukono, Ecuador, El Salvador, eruptions, Ethiopia, Hawaii, Indonesia, Japan, Kamchatka, Kilauea, Krakatau, Manda Hararo, Mayon, Papua New Guinea, Peru, Philippines, Rabaul, Russia, Sakura-jima, San Miguel, Santa María, Sarychev Peak, Shiveluch, Suwanose-jima, Tungurahua, Ubinas, United States, Weekly Volcanic Activity Reports.
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SI/USGS Weekly Volcanic Activity Report 1-7 July 2009

The Smithsonian Institution/United States Geological Survey Weekly Volcanic Activity Report for 1-7 July 2009 is available on the Global Volcanism Program website. The following is a summary and not a substitute for the full report.

New activity: Manda Hararo (Ethiopia), Mayon (Philippines), San Miguel (El Salvador), Sarychev Peak (Russia).

Ongoing Activity: Batu Tara (Indonesia), Chaitén (Chile), Dukono (Indonesia), Kilauea (Hawaii, USA), Krakatau (Indonesia), Rabaul (Papua New Guinea), Sakura-jima (Japan), Santa María (Guatemala), Shiveluch (Russia), Suwanose-jima (Japan), Tungurahua (Ecuador), Ubinas (Peru).

(more…)

New eruption in the Afar region of Ethiopia 2 July 2009

Posted by admin in activity reports, Africa, eruptions, Ethiopia.
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Thermal anomalies and dense sulphur dioxide plumes in Ethiopia appear to indicate that a significant effusive eruption has taken place in the Manda Hararo area of the western Afar region. There is as yet no visual confirmation of the eruption from the ground.

There was a VEI=2 eruption at the Manda Hararo volcanic complex in August 2007, and a larger (possibly VEI=3) eruption in the Alu-Dalaffilla region in November 2008. In terms of size, volcanic SO2 expert Prof Simon Carn of Michigan Technical University reports that the current Manda Hararo event seems to lie somewhere between the two.

The MODIS thermal alerts service at the University of Hawaii has shown hotspots of varying intensity over a considerable area of the Manda Hararo region since 27 June, while the OMI Sulfur Dioxide Group has mapped considerable SO2 emissions on 29 and 30 June:

Aura/OMI - 06/29/2009 10:21-12:03 UT (NASA/KNMI/NIVR/FMI)

Aura/OMI - 06/30/2009 11:04-11:08 UT (NASA/KNMI/NIVR/FMI)

[Thanks to Volcanism Blog reader Gijs de Reijke for information received.]

UPDATE: Dr Erik Klemetti has an informative post about this event at Eruptions. He has also wisely used maps showing up-to-date political boundaries, thus saving himself a heap of trouble.

For other Ethiopian volcanism coverage: Ethiopia « The Volcanism Blog.

Information
Global Volcanism Program: Manda Hararo – summary information for Manda Hararo (0201-115)

The Volcanism Blog

BBC documentary probes the volcanoes of Danakil 19 March 2009

Posted by admin in Africa, Erta Ale, Ethiopia, volcanology.
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There’s only one thing that is more important than news on the BBC News website, and that’s self-promotion: hence the thinly-disguised plugs for BBC television and radio programmes that regularly infest the BBC News pages. Just occasionally, however, the BBC self-publicity machine throws up something worthwhile.

A new two-part documentary on the Danakil region of north-eastern Ethiopia, Hottest Place on Earth, will (among other things) look at the fascinating geology of the region. As part of the programme Dr Dougal Jerram of Durham University will be using 3D technology to provide high resolution maps of the interior of the Dabbahu fissure and the crater of Erta Ale volcano. BBC News has an interesting article by Dr Jerram in which he tells us all about it. The video extract showing his descent into Erta Ale is fascinating, and visually stunning.

The Danakil region was the setting for last November’s dramatic fissure eruption at Alu/Dalaffilla. It would be really nice if some enterprising scientific documentary maker went there and had a look around.

(The BBC likes to get its geologist-presenters to abseil into Erta Ale whenever possible. It’s not that long ago that Dr Iain Stewart was doing it for Earth: Power of the Planet. The video of that found its way onto the BBC News website as well.)

The Volcanism Blog

Alu/Dalaffilla fissure eruption at the NASA Earth Observatory 6 February 2009

Posted by admin in Africa, Alu, Dalaffilla, eruptions, Ethiopia, NASA Earth Observatory.
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November 2008 Alu/Dalaffilla Fissure Eruption (NASA Earth Observatory. Formosat image copyright 2008 Dr Cheng-Chien Liu, National Cheng-Kung University, and Dr An-Ming Wu, National Space Organization, Taiwan.)

The NASA Earth Observatory image of the day for 4 February 2009 is a crystal-clear Formosat-2 true-colour image of the Alu/Dalaffilla area of the Afar region of north-eastern Ethiopia, for which I have written the caption. This is the place where a notable fissure eruption occurred in November 2008 (see earlier coverage at the Earth Observatory).

The original image (reduced size version above) is available at 720 x 540 pixels and a huge and beautiful 7700 x 9720 pixels (7MB). For the full picture visit the Earth Observatory, and do also have a look at the other wonderful images of the day, going back to 1999, available via the Image of the Day index page.

(Credit: NASA Earth Observatory. Formosat image copyright 2008 Dr Cheng-Chien Liu, National Cheng-Kung University, and Dr An-Ming Wu, National Space Organization, Taiwan.)

Information
Global Volcanism Program: Dalaffilla – information about Dalaffilla (0201-07=)
Global Volcanism Program: Alu – information about Alu (0201-06=)
Global Volcanism Program: volcanoes of Africa (northeastern) and the Red Sea – regional list of volcanoes from the Global Volcanism Program

The Volcanism Blog

Alu/Dalaffilla eruption – photographs 19 December 2008

Posted by admin in activity reports, Africa, Alu, Dalaffilla, eruptions, Ethiopia, geoblogosphere.
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In November an eruption occurred in the Afar region of north-east Ethiopia. Two pictures of that eruption from ground level have been published by Sylvie and Daniel Chereau’s volcano site: they were taken by Claude-Henri Mussat on 3 and 4 November and show a lofty plume. The pictures are copyrighted, so are not reproduced here – click on the link above to view.

In a new post today at the same site, there is an interesting (French language) summary, with many images, of the debate over the location of the eruption: Alu, Dalaffilla, or a point in between? The evidence from satellite imagery is strongly in favour of the latter – a fissure eruption from between Alu and Dalaffilla – but the possibility remains that the two volcanic centres are part of the same complex. More research needed …

For more on the Ethiopian eruption: Ethiopia « The Volcanism Blog.

The Volcanism Blog

Ethiopia eruption at NASA Earth Observatory 19 November 2008

Posted by admin in Africa, Alu, Dalaffilla, eruptions, Ethiopia.
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The ‘Image of the Day’ slot at the wonderful NASA Earth Observatory today features the ASTER images of the eruption in the Afar region of Ethiopia that were previewed here yesterday (thanks to our generous friends at NASA). There is an informative commentary and links to very large versions of the original images – 2000 pixels square, around 4MB – which reveal a lot of detail. It is clear from these that the origin of this eruption lies between Alu and Dalaffilla, without showing the precise character of the vents/fissures involved.

Alu/Dalaffilla eruption - ASTER images from 2006 and 2008 (NASA)

Above, detail views of the area of the activity from before and after the eruption (from the large ASTER images) are juxtaposed. The new flows appear to originate from cones along the line of the fissure(s). The south-eastern rim of the Alu horst can be seen at top left, the north-western fringes of Dalaffilla’s cone at bottom right.

N.B. For more discussion of this eruption, see Boris Behncke’s comment on yesterday’s TVB post.

Viewing the Ethiopia category will bring up previous posts from The Volcanism Blog on this eruption.

Information
Global Volcanism Program: Dalaffilla – information about Dalaffilla (0201-07=)
Global Volcanism Program: Alu – information about Alu (0201-06=)
Global Volcanism Program: volcanoes of Africa (northeastern) and the Red Sea – regional list of volcanoes from the Global Volcanism Program

The Volcanism Blog