The Arabian-Nubian Shield (ANS) is the northern half of a great collision zone called the East African Orogeny. This collision zone formed near the end of Neoproterozoic time when East and West Gondwana collided to form the supercontinent Gondwana. The East African orogeny extends southward to the Mozambique Belt, and is a subset of the overall Pan-African orogeny. The assembly of Gondwana coincided with the breakup of Rodinia, closure of the Mozambique Ocean, and growth of the shield at 870 Ma This shield growth extended for the next 300 Ma., and included island arc convergence and terrane suturing at 780 Ma, with final assembly by 550 Ma. At this time, the East African Orogen became a passive margin and the southern shore of the Paleo-Tethys Ocean.