Volcanoes commonly form on the flanks of young continental rifts, whereas in more evolved rifts the volcanism is more commonly in the rift centre. Derek Keir, Lecturer in Earth Science from the Geology and Geophysics research Group, contributed to a team that modelled the stress field below rift grabens of varying width and depth caused by the gravitational unloading, and then simulated the influence of the stress field on magma migration. They showed that when rifts are narrow and deep, as is typical of many young rifts, the stress field is focused beneath the rift and causes magma coming from the base of the crust to be deflected outwards and erupt at the rift flanks. When rifts are wider the stress field is more diffuse and facilitates vertical migration of magma through it. The work explains the distribution of volcanism in rift valleys globally.
A link to the paper in Nature Geoscience is available here: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2110.html.