School of Earth and Environment

Institute for Geophysics and Tectonics (IGT) PhD Projects

What controls the magmatic plumbing systems of spreading centres in Afar?

[Fully Funded NERC studentship] 

Supervisors: Professor Tim Wright (SEE), Professor Andy Hooper (SEE), Dr Juliet Biggs (Bristol) 

Contact email: t.j.wright(at)leeds.ac.uk

Funding is provided by the UK Natural Environment Research Council (NERC) and is subject to standard eligibility regulations; normally UK nationals are eligible for a full scholarship, whilst EU candidates are awarded a Fees Only scholarship, although there are some exceptions.  Please check with the administrator.  Proposed start date October 2016.

Background

Simple thermal models developed at mid-ocean ridges suggest that the depth of magma chambers at spreading centres is controlled primarily by spreading velocity and rates of magma supply (e.g. Phipps Morgan and Chen, 1993).  In such models, isolated, deep magma chambers underneath central volcanoes are found at slow-spreading ridges such as the Mid-Atlantic Ridge, and elongated, shallow axial magma chambers are only found at fast-spreading ridges such as the East Pacific Rise. 

However, recent observations from the subaerial spreading centre in Afar (Pagli et al, 2012) of a shallow axial magmatic system under the slow-spreading Erta Ale magmatic segment suggest that existing models may need revision.  This project will use existing and new InSAR observations of surface motions at volcanoes in Afar and elsewhere to test and constrain current models of magmatic systems at spreading centres. 

The studentship forms part of the NERC RiftVolc project, which aims to improve the understanding of rift volcanism past, present and future, largely focusing on the central Main Ethiopian Rift (MER).  This region is of particular significance as it displays all the main features of rift volcanism, the volcanoes are a significant threat to the local population, and the potential for geothermal exploitation is enormous.  This project will expand the existing reach of the RiftVolc project to the Afar region, which was the focus of the Afar Rift Consortium project, providing new constraints on magmatic systems that can be compared to those made in the MER. 

It would suit a numerate physical scientist with a background in Earth sciences, physics, or similar fields. They will be expected to interact with the RiftVolc project team, providing opportunities for fieldwork in both the MER and Afar regions. 

Objectives

The student will work with leading scientists at both Leeds and Bristol to improve understanding of deformation at Afar volcanic centres.  In particular, they will:  

  • make new, systematic observations of deformation (e.g. Wright et al., 2012) using the full 20 year archive of SAR data from ERS and Envisat, and new data acquired by Sentinel-1. 
  • determine the depths and geometries of magmatic systems using elastic models, along with complementary constraints acquired during the Afar Rift Consortium project from GPS, seismicity, petrology, and magnetotellurics (e.g. Field et al., 2012). 
  • examine how the depth of the magmatic systems varies as a function of spreading velocity and rates of magmatic supply, and compare the observations with those made on mid-ocean ridges, and elsewhere on the East African Rift system. 
  • use the data to test simple thermal models of magmatic systems at spreading centres. 

Potential for high impact outcomes

The volcanoes of Afar have been very active over the last 20 years, and activity is expected to continue.  As part of the collective RiftVolc project, the work has immediate relevance for a wide range of stakeholders with regard to the geohazard that active volcanism presents, including through the provision of practical advice and support to local communities, and research outputs and methodologies that will assist both policy makers and those working in natural hazard assessment and management more broadly. 

In scientific terms, the project will ensure that the outcomes of the Afar Rift Consortium are built upon so that the research community continues to benefit from improved understanding of this active and dramatic region.

Figure1: Data and model for the 2008 eruption on the Erta Ale range, from Pagli et al., 2012. (a) Plan view of the sill contraction, overlain by topographic contours and the outline of the lava flow; (b) cross section through the model geometry along line K-K’; (c,d,e) real, model, and residual interferograms. Data from the ALOS satellite; (f,g,h) cross sections through the data and model.
Figure1: Data and model for the 2008 eruption on the Erta Ale range, from Pagli et al., 2012. (a) Plan view of the sill contraction, overlain by topographic contours and the outline of the lava flow; (b) cross section through the model geometry along line

Training

The student will work under the supervision of Professors Wright and Hooper in Leeds, and Dr Biggs in Bristol.  The project will provide a high level of specialist scientific training in the processing of satellite radar data, and the development of numerical models.

Although based in the Institute for Geophysics and Tectonics in the School of Earth and Environment at Leeds, co-supervision will involve regular meetings between all partners and extended visits to Bristol’s School of Earth Sciences, where they will benefit from the expertise of members of the Volcanology and Geophysics groups.

They will also interact with the wider RiftVolc team, specifically the geodetic and modelling aspects of the project, and be a member of NERC’s Centre for the Observation and Modelling of Earthquakes and Tectonics (COMET), a collaboration between scientists in Leeds, Oxford, Cambridge, Bristol, UCL, Glasgow, and Reading. 

Finally, the student will also have access to a broad range of Faculty- and University-led training via the EME Hub.

References

Field L; Blundy J; Brooker RA; Wright TJ; Yirgu G (2012) Magma storage conditions beneath Dabbahu Volcano (Ethiopia) constrained by petrology, seismicity and satellite geodesy, Bulletin of Volcanology, 74, pp.981-1004.

Pagli C; Wright TJ; Cann JR; Ebinger CJ; Yun S-H; Barnie T; Ayele A (2012) Shallow axial magma chamber at the slowspreading Erta Ale Ridge, Nature Geoscience, 5, pp.284-288.

Phipps Morgan J; Chen YJ (1993) Dependence of ridge-axis morphology on magma supply and spreading rate, Nature 364, 706-708.

Wright TJ et al. (2012) Geophysical constraints on the dynamics of spreading centres from rifting episodes on land, Nature Geoscience, 5, pp.242-250.