Estuaries – where the waters of seas and rivers mix – on the northwestern coast of Madagascar, a large African island in the Indian Ocean. The Mozambique Channel (top) separates Madagascar from the southeastern coast of Africa. The Betsiboka River, which flows into Bombetoka Bay (upper left), leaves striking red floodplain sediments. Mahajamba Bay (right) is fed by several rivers including the Mahajamba and Sofia. Like the Betsiboka, the floodplains of these rivers contain reddish sediments eroded from their basins upstream. (Nasa, CC BY-NC 2.0)