Volcanism in continental rifts is generally observed to shift over time
from the inside of the basin to its flanks and conversely, but the
controls on these switches are still unclear. Here we use numerical
simulations of dike propagation to test the hypothesis that the
spatio-temporal evolution of rift volcanism is controlled by the crustal
stresses produced during the development of the rift basin. We find that
the progressive deepening of a rift is accompanied by a developing
stress barrier under the basin, which deflects ascending dikes, causing
an early shift of volcanism from the inside to the flanks. The
intensification of the barrier due to further deepening of the basin
promotes the formation of lower crustal sill-like structures that can
stack under the rift, shallowing the depth of magma injection,
eventually causing a late stage of in-rift axial volcanism.