Lecture - Witnessing the birth of Africa's new ocean: the Afar Rift Consortium

The Anglo-Ethiopian Society

Lecture - Wednesday 26th January 2011

Witnessing the birth of Africa's new ocean: the Afar Rift Consortium

Given by - Dr Tim Wright

Reviewed by - Diana Skingle

The Society's 2011 series of lectures opened with a fascinating and well attended presentation by Dr Tim Wright, based at the University of Leeds and principal investigator of the Afar Rift Consortium. The Consortium,¹ funded by NERC, has brought together an international multidisciplinary scientific team to study the active magmatic rift in Afar.²

Aerial photograph of the Da 'Ure volcanic vent which opened up in September 2005.
Photo - © Elizabeth Baker

Dr Wright began his lecture by explaining the scientific importance of the volcanic activity between 2005 and 2009 in the remote Afar Region. On 26 September 2005 an eruption in the Dabbahu magmatic segment resulted in a large volcanic dyke - a vertical crack which is created when magma seeps from underground through rifts in the surface of the earth - about 60km long, 15km wide and 60 metres deep between the Dabbahu and Gab'ho volcanoes at the northern end and the Ado'Ale volcanic complex at the southern end. Scientific investigations and modelling by the Afar Rift Consortium, using satellite and other data, has shown that events were even more dramatic and complex than at first thought. The pace and extent of the volcanic activity in Afar is said to be nothing short of extraordinary. Scientists believe they are witnessing the African continent splitting apart and the beginnings of a new ocean.

Erta 'Ale lava lake.
Photo - © James Hammond

Continental splits usually take place beneath the ocean with a large earthquake cracking the surface and moving the oceanic plates, resulting in a mid-ocean ridge. Afar Region is the only place on Earth today where this continental rupture and the beginning of sea floor spreading are occurring above sea level. It offers scientists a unique opportunity to study the transition from continental break-up to the birth of a new ocean. The site of this rare occurrence is the Afar Triple Junction where the Nubia, Somalia and Arabia tectonic plates intersect. For a stretch of about 40 miles, the plates are pulling apart at the rate of a few centimetres a year, about the speed that our fingernails grow.

Numerous faults and fissures can be seen from the ground and from the air. The seismic data from Ato Atalay Ayele of the Geophysical Observatory in Addis Ababa showed that an unexpectedly massive event took place in Afar in 2005. Initially it was thought to be fairly simple volcanic activity. However, detailed examination of the Dabbahu magmatic segment data showed that a complex series of quakes had taken place, with no big earthquake but lots of aftershocks, ash and pumice. 2.5 km3 of magma (about twice the volume of Mount St Helens in 1980 and ten times the volume of the Eyjafjallajökull eruption in Iceland in 2010) had been intruded along the dyke. Satellite radar interferometry (InSAR) imagery showed over 60km of intense activity mostly over 10 days. Evidence on the ground revealed extensive rock uplift of 2 metres and subsidence of 2 metres across a wide area. Three-dimensional modelling of the magma 'plumbing system' identified several deflating magma chambers 2-4 kilometres below the surface.

Dr Wright explained that ESA imaging showed that recent deformation of the Afar Region area had in fact been taking place since 1996. Significant volcanic activity continues. On 17 June 2006, molten rock broke through the Earth's surface, followed by a series of similar events in 2007-2009. In each case, magma was injected into cracks along the rift, moving at the rate of 8km in 4 hours. Scientists expect that more deformation and eruptions will take place in the next few years, possibly even larger than those that have already taken place. The Afar Region is therefore experiencing a unique moment and is the most rapidly deforming area on Earth today. The Consortium continues to monitor these momentous events.

The Society extends its thanks to Dr Tim Wright for giving such a fascinating lecture about the Afar Region, an area well-known and experienced by many of our members. Dr Wright should also be commended for making a complex scientific subject accessible to his largely non-technical audience.

Further information about the Afar Rift Consortium's work can be found at www.see.leeds.ac.uk/afar. The website also contains technical data related to the project and many of the images and diagrams with which Dr Wright illustrated his lecture.

¹ The Afar Rift Consortium is a project funded by the UK Natural Environment Research Council (NERC) with additional support from the British Geological Survey, the Centre for the Observation and Modelling of Earthquakes and Tectonics, the European Space Agency, Incorporated Research Institutions in Seismology, the National Science Foundation, The Royal Society, SEIS.UK Geophysical Equipment Facility, and UNAVCO.
² The Consortium is made up of scientists from the Universities of Leeds, Bristol, Oxford, Edinburgh, and Cambridge with partners in Ethiopia, France and the United States.