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The northern Afar Rift is a region where the earliest stages of the splitting of a continent and creation of new oceanic crust can be observed. New oceanic-type crust is at present being emplaced along the axis of the rift. The axis is offset at several places; offsets of the western margin of the rift (scarp of the Ethiopian Plateau) correspond to the axial offsets. The main tectonic extensional features of the region are parallel to this axis; however, tectonic structures which are transversal relative to this axis were also observed at the offsets and elsewhere. These transversal structures are characterized by 1.(a) alkalibasalt volcanism which contrasts with the tholeiitic or intermediate basaltic volcanism of the axial structures2.(b) upward intrusion of mantle material, as shown by geophysical data and by the presence of mantle-derived peridotite inclusions in the basalts from the transversal structures. The transversal tectonic structures developed by rejuvenation of older, pre-rift structures. These characteristics are similar to features observed in the equatorial Atlantic, where the large fracture zones, which probably also developed along ancient tectonic structures, are characterized by alkali-basalt volcanism, and by upbulging and upward intrusion of the mantle. The development of axial offsets and transverse tectonic structures both in the Afar Rift and in the early stages of the Atlantic Rift can be explained by essentially the same model.

Three main types of volcanism, viz. oceanic, continental and stratoid, reflect the tectonic evolution of Afar.