The Anglo-Ethiopian Society
Lecture - Wednesday 16th February 2005
The ‘EAGLE’ Project
Given by - Professor Peter Maguire
Reviewed by - Geoffrey Ben-Nathan
The 'break-up' of Africa! What's this? A machiavellian plot?
Perish the thought!
No politics here. This was an evening of Science: Science for the sake of Science. And as with most things scientific these days, scientific truth is much stranger than non-scientific fiction. Would you believe, for example, that volcanic activity in Ethiopia has its source down in the South Atlantic? It's like having a boil on your hand originating from activity in your foot!
But let's start at the beginning. Our speaker, Peter Maguire, is a professor at Leicester University. Peter is a geophysicist, a seismologist to be precise. “Earth science is a means of getting to travel the Earth, and Ethiopia has become very close to my heart”, he told us.
Why Ethiopia? Well, the East African rift system is the biggest rift system in the world. There are others: Lake Baikal and the Rio Grande, and the Central European rift. None of them compare to East Africa. The northern Ethiopian Rift Valley is one of the few places on Earth where the break-up of the continent is visible.
And the scientific question is: what's happening in the rift system? Is it getting wider? Or not? The Ethiopia Afar Geoscientific Lithospheric Experiment (EAGLE) was set up to find out.
Leading the project was Ato Mulugeta Amha of the Ethiopian Geological Survey based at Addis Ababa University. He headed a team of 40 Ethiopian scientists with a further 80 scientists participating from Leicester, Leeds, Royal Holloway and Stanford, Texas.
Jules Verne, it seems, got it wrong. The centre of the Earth is nothing but bad news. The inner 'core', as it's called, is many hundreds of degrees hot. Travelling at 500 km a day and you might want to do more if you could - it would take you two weeks to cover the 7,000 km to the surface. Before you get to the surface, you encounter a 'plate', 50-100 km thick, a 'crust', 35 km thick and a 'mantle' 8 km thick. None of all of this is enough to suppress seismic activity emanating from the molten core. There are, Peter Maguire told us, 'hotspots' all over the place - Ethiopia and the Rift Valley having more than their fair share. It's of course the seismic activity now, and through the ages, on land and under the sea, that is responsible for continents being forced apart. Gigantic forces and pressures, as we all know, are at work all the time.
The EAGLE project was conceived to monitor the progress of these forces. The project was carried out in three phases.
Phase one was conducted between October 2001 and February 2003. In a huge working area of 400 square kilometres, seismometers were placed into the ground. The seismometers recorded vibrations and variations in movement to within five metres. Prof Maguire described the process as similar to a brain-scan. The result is an accurate picture from which to start.
Phase two coincided with part of phase one time-wise and ran between October 2002 and February 2003. This compared land 'rifting' with ocean 'rifting'. The two work in different ways - one thermally, the other by 'magmatic extension'.
Phase three involved 'self-induced' seismic activity: detonating 27 tons of explosives imported into Ethiopia from the UAE on the SS Omo. The explosions, you will be pleased to learn, were conducted in an orderly fashion and not all in one go. This was science for the sake of science. Using recorders and geophones, the explosions were arranged to determine how fast seismic waves travel through the crust of the earth's surface.
Work carried out by seismologists, Prof. Maguire told us, is not just academic. The Naivasha Power Station developed where it did due to work done in Kenya in the l970s. Ethiopia, we learned, “is richer in natural resources than almost any other country in Africa. Ethiopia could power the whole of the continent geothermally”.
And not just that. Geophysicists have calculated the thickness of sediments and as a result, it is known, Prof Maguire claimed, that there is oil in the western part of the country near the Sudanese border.
A fascinating subject, a fascinating talk supported by excellent graphics, we are extremely grateful to Prof Maguire for giving us a geophysical knowledge of Ethiopia.
And the $64,000 question? Yes! The rift is slowly widening.
Addendum
With serious earthquakes occurring off Sumatra it was particularly appropriate that the Society should hear of the geological volatility of the Rift Valley region. Africa is breaking up along certain well-known fault lines but it is important to try to discover to what extent and how fast this is happening in Ethiopia: To this end, Professor Peter Maguire told us, the EAGLE project (Ethiopia Afar Geoscientific Lithospheric Experiment) took subterranean soundings at various points on the Rift Valley edge where it is at its least steep - between Akaki and Modjo (more or less). The results are still being evaluated. We have not had many geological subjects and so it was especially good for us to learn these things.
I like to point out to tourists as we pass the volcano Fantalle in the Awash National Park the geologically recent (1820) lava flow on its southern flank. I am grateful to Peter Maguire for giving me more interesting, up-to-date information to shoot at them about this area.
Richard Snailham