Huge rift study throws up Earth's secrets

An extraordinary seismic experiment in the Horn of Africa will shed new light on one of the fundamental processes on Earth - the break-up of continents.

EAGLE (The Ethiopian-Afar Geophysical Lithospheric Experiment) is a major British initiative to investigate how the African continent is splitting along the Ethiopian Rift.

Dr Cindy Ebinger and Dr Mary Fowler of Royal Holloway's Department of Earth Sciences are leading a team of scientists from the Universities of Leicester and Leeds in collaboration with the University of Addis Abeba and Ethiopian government groups. Ongoing field and satellite photo interpretation studies by Ebinger, Fowler and colleagues Prof K McClay, Dr C Elders, Dr R Gloaguen, Dr C Tiberi, and PhD students E Wolfenden and I Ukstins form the framework for Project EAGLE.

Seismic "echoes" from controlled explosions and natural earthquakes will be recorded to provide an image of the top 100km or so of the Earth - a 3-D picture of a continental rift system immediately prior to the formation of an ocean basin.

The East African Rift Valley is one of the very few places on Earth where it is possible to study the active processes of volcanism and stretching of the continental plate immediately before flooding by a newly formed ocean. The area extends from the Zambesi valley in the south through Malawi, Tanzania, Congo, Uganda and Kenya into the Main Ethiopian Rift Valley before emerging into the furnace-hot region of Afar at the junction with the Red Sea and Gulf of Aden. In time the African plate may split apart along the line of the Rift Valley and form a new ocean.

Between October 2001 and January 2003, 20 scientists will carry out two large deployments of seismic recording instruments. 180 instruments will be distributed over an area of 250x250 square kilometres covering the rift and centred on a chain of dormant volcanoes to the south-east of Addis Abeba. 400 instruments will be deployed on a 400km long profile from the Blue Nile in the Ethiopian Highlands to the north of Addis Abeba, across the Rift and the volcanic chain, and up and over the southeastern flank of the Rift.

Apart from providing a missing snapshot in the study of continental break-up, there are also immediate economic, environmental and cultural objectives for EAGLE. It seeks to identify possible geothermal fields in the Rift and to inform oil and geothermal exploration geologists in their work to discover and exploit reserves along other continental margins where plates have successfully rifted. The project will help in both earthquake and volcanic risk assessment, and will inform anthropologists, archaeologists and geographers, in their studies of early Man and his interaction with the environment.

In 2000 a consortium of Royal Holloway, University of London with Leicester, Leeds, and Cambridge universities netted a JIF award of £2.1 million for a project on seismic data acquisition. The EAGLE project is one of three projects proposed in the original grant application. The JIF funding allowed the SEIS-UK (Seismic Equipment Infra-Structure in the UK) consortium to purchase field seismic instrumentation, computers, support staff and software for experiments involving onshore recording of controlled source and natural seismic events. The facility - together with a complete data archiving facility - is housed at the University of Leicester.

The 1500m high fault scarp between the plateau and the rift valley where active volcanoes are located.

A map of the area in which seismic equipment will be deployed and controlled explosions carried out for the project.