The Alexandria Coastal Dunefield to the east of Port Elizabeth was formed over the past 6 500 years when the sea level returned to its present level after the last Ice Age. The dunes can rise up to 140 metres, with the average dune height being 30 metres above sea level. The Alexandria Coastal Dunefield, of which the Colchester section of the dune field falls within the metro, is the largest coastal dunefield in the Southern Hemisphere one of the most impressive in the world. The dunefield has formed as a result of the interaction between the local wind climate, ready sand supply on the 40 km long beach, and the configuration of the bay shoreline. Only in desert areas, are bigger and more extensive dunes found. It is currently on the Tentative list as a potential future UNESCO World Heritage Site.