Active Development of Continental Rifts: Wide Swath Interferometry in East Africa.

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We like to think of the ground as a solid, immovable platform in an uncertain world, but even the continents are slowly drifting beneath our feet; the patterns of land and sea constantly changing. East Africa is being gradually pulled apart by the forces of plate tectonics - eventually there will be a new ocean, but at the present day, we can already see the beginnings: the three thousand kilometre long Great Rift Valley containing a string of volcanoes and prone to earthquakes. But what happens next? The established view is that stretching takes place during earthquakes as two blocks slide past each other on faults. Yet recent satellite observations have shown that magma is important. Imagine sliding apart two pieces of wood stacked on top of each other - the forces of friction resist you. Now imagine the pieces of wood are floating on a pond: this is a much easier task, there is less friction and the water flows to fill the gap. This is similar to what happens in East Africa - the presence of magma alters the way in which the continent stretches. Scientists are working on a new paradigm, one in which magma plays a crucial role in continental rifts. Before new models can be developed, we need a clear set of observations against which to test them. Currently only a few case studies are available - yet we need to see the patterns of magma and fault movement throughout the rift: Is the stretching focused on the faults or near the volcanoes the centre of the valley? How much magma is there? Magma rises in short pulses, like drips, but what controls how these drips form? The best way to begin answering these questions is to use satellite observations - avoiding the need for time-consuming expeditions to remote and dangerous terrain. Using satellite-based radar, it is possible to cover hundreds of kilometres of the rift with a single image and detect small amounts of uplift or subsidence associated with stretching and magma moving underground. Once particular areas of concern have been identified, ground-based instruments can be used to provide more detailed observations on individual examples. Using the archive of large satellite images, I will analyse ground movement spanning 7 years and covering the length of the rift, from Ethiopia to Malawi. These observations will describe the pattern of faulting and magma movement in space and time, allowing the development of a new class of continental rifting models, to include the effects of magma. In addition to these scientific goals, this project will generate information on what is currently an underestimated source of potential hazard and we will communicate the results to local and global management bodies.