Observations of seafloor spreading in Afar during the November 1978 fissure eruption

Allard, P.; Tazieff, Haroun; Dajlevic, D.

doi:10.1038/279030a0

Cited by 53 publications

(20 citation statements)

References 11 publications

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“…Basalt lava was extruded from the northwestern end of the rift axis over 7 days (Allard et al, 1979) and fissuring also extended SE beneath the Gulf of Ghoubbet. The central volcano, Fieale, between Asal and Ghoubbet, marks the main source of mantle magma supply .…”

Section: Ardoukoba (1978)mentioning

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: Ardoukoba (1978)mentioning

confidence: 99%

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

et al. 2016

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“…Despite this, many regional events do not correlate with changes in lake activity and there is a significant chance of finding such coincidences with regional events randomly located in time. However, there may still be a relationship over longer timescales, as the change in behaviour at Erta 'Ale stating with the rise in lake level in 2002 (1) pre-empts an apparent regional upsurge in magmatic-tectonic events over the following decade and (2) appears to be the first major change at the lava lake since the overflows of the early 1970s, which themselves preceded the Asal Ghoubbett rifting event in November 1978 (Allard et al 1979). This may indicate that Erta 'Ale responds to region-wide developments on a timescale of years to decades and anticipates them, perhaps due to the open vent nature of the volcano rendering subtle perturbations at depth visible more rapidly at the surface than other magmatic systems.…”

Section: Synthesis and Interpretationmentioning

confidence: 99%

Does the lava lake of Erta ‘Ale volcano respond to regional magmatic and tectonic events? An investigation using Earth Observation data

Barnie

Oppenheimer

Pagli

2016

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Erta 'Ale volcano lies at the centre of the Erta 'Ale rift segment in northern Afar, Ethiopia and hosts one of the few persistent lava lakes found on Earth in its summit caldera. Previous studies have reported anecdotal evidence of a correlation between lake activity and magmatic and tectonic events in the broader region. We investigated this hypothesis for the period 2000-15 by comparing a catalogue of regional events with changes in lake activity reconstructed from Earth Observation data. The lava lake underwent dramatic changes during the study period, exhibiting an overall rise in height with concomitant changes in geometry consistent with a change in heat energy balance. Numerous paroxysms occurred in the lake and in the north pit; a significant dyke intrusion with subsequent re-intrusions indicated a role for dykes in maintaining the lake. However, despite some coincidences between the paroxysms and regional events, we did not find any statistically significant relationship between the two on a timescale of days to weeks. Nevertheless, changes in lake activity have preceded the broad increase in regional activity since 2005 and we cannot rule out a relationship on a decadal scale.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…An extensive set of faults up to 10 km long slipped by up to 0.5 m (ref. 46), and 16 × 10 6 m 3 of basaltic lava was erupted from a 0.75-km-long fissure 44 . Geodetic measurements showed that up to 1.9 m of extension occurred across the rift 46,47 , with a 3-km-wide central graben subsiding by 70 cm and rift flanks uplifting by ~20 cm (ref.…”

Section: Subaerial Rifting Episodes In the Modern Eramentioning

confidence: 99%

“…Geodetic measurements showed that up to 1.9 m of extension occurred across the rift 46,47 , with a 3-km-wide central graben subsiding by 70 cm and rift flanks uplifting by ~20 cm (ref. 46). The geodetic data have been modelled by the intrusion of two dykes along 20 km of the rift axis with a total thickness of 1.5-3 m in the upper ~5 km of crust [48][49][50] .…”

Section: Subaerial Rifting Episodes In the Modern Eramentioning

confidence: 99%

Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

et al. 2012

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Most of the Earth's crust is created along 60,000 km of mid-ocean ridge system. Here, tectonic plates spread apart and, in doing so, gradually build up stress. This stress is released during rifting episodes, when bursts of magmatic activity lead to the injection of vertical sheets of magma -termed dykes -into the crust. Only 2% of the global mid-ocean ridge system is above sea level, so making direct observations of the rifting process is difficult. However, geodetic and seismic observations exist from spreading centres in Afar (East Africa) and Iceland that are exposed at the land surface. Rifting episodes are rare, but the few that have been well observed at these sites have operated with remarkably similar mechanisms. Specifically, magma is supplied to the crust in an intermittent manner, and is stored at multiple positions and depths. It then laterally intrudes in dykes within the brittle upper crust. Depending on the availability of magma, multiple magma centres can interact during one rifting episode. If we are to forecast large eruptions at spreading centres, rifting-cycle models will need to fully incorporate realistic crust and mantle properties, as well as the dynamic transport of magma.

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Observations of seafloor spreading in Afar during the November 1978 fissure eruption

Cited by 53 publications

References 11 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

Does the lava lake of Erta ‘Ale volcano respond to regional magmatic and tectonic events? An investigation using Earth Observation data

Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

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