A multidisciplinary study of the final episode of the Manda Hararo dyke sequence, Ethiopia, and implications for trends in volcanism during the rifting cycle

Barnie, T.; Keir, Derek; Hamling, I. J.; Hofmann, Beda A.; Belachew, M.; Carn, S. A.; Eastwell, David; Hammond, James; Ayele, Atalay; Oppenheimer, Clive; Wright, Tim

doi:10.1144/sp420.6

Cited by 32 publications

(64 citation statements)

References 65 publications

(75 reference statements)

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“…Over the next 5 years there were 12 more dykes with an average length of 9.5 km, width of 1.7 m, depth range of 0-10 km and volume of 90 × 10 6 m 3 (Hamling et al, 2009;Ferguson et al, 2010). These were all fed by a magma source below the middle of the rift segment that deflated as rising magma intruded (Grandin et al, 2009 (Ferguson et al, 2010;Barnie et al, 2015). Sulfur dioxide plumes were consistent with volatile loss solely from the extruded volumes of lava.…”

Section: Dabbahu-manda Hararo (2005-2010)mentioning

confidence: 92%

Historical Volcanism and the State of Stress in the East African Rift System

et al. 2016

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Crustal extension at the East African Rift System (EARS) should, as a tectonic ideal, involve a stress field in which the direction of minimum horizontal stress is perpendicular to the rift. A volcano in such a setting should produce dykes and fissures parallel to the rift. How closely do the volcanoes of the EARS follow this? We answer this question by studying the 21 volcanoes that have erupted historically (since about 1800) and find that 7 match the (approximate) geometrical ideal. At the other 14 volcanoes the orientation of the eruptive fissures/dykes and/or the axes of the host rift segments are oblique to the ideal values. To explain the eruptions at these volcanoes we invoke local (non-plate tectonic) variations of the stress field caused by: crustal heterogeneities and anisotropies (dominated by NW structures in the Protoerozoic basement), transfer zone tectonics at the ends of offset rift segments, gravitational loading by the volcanic edifice (typically those with 1-2 km relief) and magmatic pressure in central reservoirs. We find that the more oblique volcanoes tend to have large edifices, large eruptive volumes, and evolved and mixed magmas capable of explosive behavior. Nine of the volcanoes have calderas of varying ellipticity, 6 of which are large, reservoir-collapse types mainly elongated across rift (e.g., Kone) and 3 are smaller, elongated parallel to the rift and contain active lava lakes (e.g., Erta Ale), suggesting different mechanisms of formation and stress fields. Nyamuragira is the only EARS volcano with enough sufficiently well-documented eruptions to infer its long-term dynamic behavior. Eruptions within 7 km of the volcano are of relatively short duration (<100 days), but eruptions with more distal fissures tend to have lesser obliquity and longer durations, indicating a changing stress field away from the volcano. There were major changes in long-term magma extrusion rates in 1977 (and perhaps in 2002) due to major along-rift dyking events that effectively changed the Nyamuragira stress field and the intrusion/extrusion ratios of eruptions.

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Section: Dabbahu-manda Hararo (2005-2010)mentioning

confidence: 92%

Historical Volcanism and the State of Stress in the East African Rift System

et al. 2016

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“…At the southern edge of the Danakil depression, there are the Amarta-Barawli volcanic complex (ABVS), Afdera volcano (AV), and Alayta volcano (ALV) (Barberi and Varet, 1970). To the south of the Danakil depression in central west Afar, the rift axis steps en echelon to the southwest into the Dabbahu segment (DVS), which underwent a major dike intrusion episode during (Wright et al, 2006Ebinger et al, 2008;Barnie et al, 2015). Nabro volcano (NVS), which erupted in June 2011, is on the eastern margin of the Danakil depression near the Eritrean-Ethiopian border (Hamlyn et al, 2014;Goitom et al, 2015;Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Illsley‐Kemp¹,

Keir²,

Bull³

et al. 2017

Bulletin of the Seismological Society of America

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The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup. To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale. The accurate calculation of earthquake magnitudes allows the estimation of b-values and maximum magnitudes, both of which are essential for seismic-hazard analysis. Earthquake data collected between February 2011 and February 2013 on 11 three-component broadband seismometers were analyzed. A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km. A total of 32,904 zero-to-peak amplitude measurements (A) were measured on the seismometer's horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (M L ), 22 station correction factors (C), and 2 distance-dependent factors (n, K) in the equation M L logA− logA 0 C. The resultant distance correction term is given by − logA 0 1:274336 logr=17 − 0:000273r − 17 2. This distance correction term suggests that attenuation in the upper and mid-crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt. In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band. The calculated station corrections serve to reduce the M L residuals significantly but do not show a correlation with regional geology. The cumulative seismicity rate produces a b-value of 0:9 0:06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading.Electronic Supplement: List of all local earthquakes used in the study with calculated local magnitudes and associated magnitude error.

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“…Over the next five years, 13 smaller dykes intruded a further c. 1 km 3 of magma (Hamling et al , 2010Grandin et al 2010b;Belachew et al 2011;Barnie et al 2015) and there were three further eruptions (Ferguson et al 2010;Barnie et al 2015). These were also fed from the Ado 'Ale Volcanic Complex at the centre of the rift Belachew et al 2011;Grandin et al 2011).…”

Section: The Dabbahu Rifting Episode and The Afar Rift Consortiummentioning

confidence: 99%

“…The investigations have been wide in scope and have included the production of a new geological map of the Dabbahu (Manda -Hararo) spreading centre (Vye-Brown et al 2016a). Detailed forensic investigations have revealed the details of dyke intrusions and eruptions using data from local seismic arrays Grandin et al 2011), satellite geodesy Grandin et al 2010b), geology/petrology (Ferguson et al 2010) and combinations of these techniques Barnie et al 2015). These studies have shown that dykes can interact in space and time, possibly through stress interactions (Hamling et al 2010), and that the style of volcanism and intrusion is highly variable in space (Pagli et al 2012).…”

Section: The Dabbahu Rifting Episode and The Afar Rift Consortiummentioning

confidence: 99%

Magmatic rifting and active volcanism: introduction

Wright

Ayele

Ferguson

et al. 2016

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A major rifting episode began in the Afar region of northern Ethiopia in September 2005. Over a 10-day period, c. 2.5 km 3 of magma were intruded into the upper crust along a 60 km-long dyke separating the Arabian and Nubian plates. There was an intense seismic swarm and a small rhyolitic eruption; extension of up to 10 m occurred across the rift segment. Over the next five years, a further 13 dyke intrusions caused continued extension, eruptions and seismicity. The activity in Afar led to a renewed international focus on the role of magmatism in rifting, with major collaborative projects involving researchers from Ethiopia, the UK, the USA, France, Italy and New Zealand working in Afar and Ethiopia to study the ongoing activity and to place it in a broader context. This book brings together articles that explore the role of magmatism in rifting, from the initiation of continental break-up through to full seafloor spreading. We also explore the hazards related to rifting and the associated volcanism. This renewed focus on magmatism and its role in rifting has implications for our understanding of how continents break-up and the associated distribution of resources in rift basins and continental margins.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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A multidisciplinary study of the final episode of the Manda Hararo dyke sequence, Ethiopia, and implications for trends in volcanism during the rifting cycle

Cited by 32 publications

References 65 publications

Historical Volcanism and the State of Stress in the East African Rift System

Historical Volcanism and the State of Stress in the East African Rift System

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Magmatic rifting and active volcanism: introduction

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