Current kinematics and dynamics of Africa and the East African Rift System

Stamps, D. S.; Flesch, L. M.; Calais, E.; Ghosh, A.

doi:10.1002/2013jb010717

Cited by 88 publications

(108 citation statements)

References 98 publications

(153 reference statements)

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“…The boundary forces at the plates' sides and bases and the buoyancy forces from lateral variations in gravitational potential energy are responsible for this motion and the resultant horizontal stress field (Craig et al, 2011;Stamps et al, 2014; Figure 2A). A normal faulting regime (vertical stress component (σ v ) greater than the two horizontal stress components: σ v = σ 1 > σ 2 > σ 3 ) dominates in the EARS, with a strike slip regime (vertical stress component is intermediate relative to the horizontal stress components: σ 1 > σ v > σ 3 ) more evident in some places (e.g., Asal-Ghoubbet Rift, Delvaux and Barth, 2009).…”

Section: Factors That Could Affect Stress and Strain In The Earsmentioning

confidence: 99%

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: Factors That Could Affect Stress and Strain In The Earsmentioning

confidence: 99%

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

et al. 2016

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“…A seaward propagation was recently revisited by Wiles et al (2014) as a probable cause for up to 31 km long and 18 km wide seafloor mounds observed northwest of the MozR. Other authors proposed that the western boundary of the Lwandle microplate traces along the eastern border of the MozR (Stamps et al 2008;Saria et al 2014;Stamps et al 2014), thus presenting another probable connection of neotectonic activity to a southward propagation of the EARS in the vicinity of the MozR.…”

Section: Post-sedimentary Magmatism At the Mozambique Ridgementioning

confidence: 99%

The Mozambique Ridge: a document of massive multistage magmatism

et al. 2016

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S U M M A R YThe Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous. The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin. High-resolution seismic reflection data reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intrabasement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic of eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge. We observe evidence for widespread post-sedimentary magmatic activity that we correlate with a southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ∼131 and ∼125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.

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“…However, unlike the usual assumption, according to paleomagnetic data (Besse and Courtillot, 2003), Africa has a southward component of motion, supporting the shallow hotspot reference frame (Muluneh et al, 2014). Recently, Stamps et al (2014) found deviatoric stress resulting from GPE gradient is sufficient to drive Africa and Somalia plate separation and Quaternary to Recent deformation in East African Rift System (EARS).…”

Section: Introductionmentioning

confidence: 89%

“…However, Trampert et al (2004) questioned the existence of a deep mantle plume beneath Africa, arguing how the low-velocity of seismic waves could be related to denser Fe-rich lower mantle than to hot raising material. Stamps et al (2014) and Bird et al (2008) quantified the basal shear traction beneath Africa plate. These studies showed shear traction magnitudes varying by 1 order of magnitude.…”

Section: Comparison Of Side and Basal Torques In The Ethiopian Riftmentioning

confidence: 99%