The WIO is notable for its narrow shelves (Figure 8.2), with the exceptions of the central Mozambican region, where sediments from the largest river in East Africa, the Zambezi River, have extended the shelf break some 140 km offshore, and off parts of the Malagasy west coast, where large rivers such as the Betsiboka have been similarly influential. The East African shelf only averages 15-25 km in width (UNEP-GEF 2008), compared to a global average of around 80 km (Shepard 1963, Pinet 2009). Other areas where the shelf widens considerably beyond the local average are off the Thukela River in South Africa, the Limpopo River in southern Mozambique, the Ruvuma, Rufiji and Pangani rivers in Tanzania, and the Tana and Sabaki Rivers in Kenya. In parts of Kenya, northern Mozambique and the east coast of South Africa, the shelf break is as little as a few hundred metres to <4 km from the coast (Flemming 1981, Abuodha 2003, Green 2009a).