The South Atlantic Ocean can be defined as the waterbody that stretches from the equator in the north to its border with the Southern Ocean in the south. The Pacific and Indian Oceans also border the South Atlantic, as well as smaller water bodies such as the Scotia and Weddell Seas. Due to the vastly different climates between the northern and southern areas of the South Atlantic as well as their varied origins, the islands have extremely varied geographical features. The biodiversity of the islands of the South Atlantic is high and much of the flora and fauna is endemic to the area.
The waters of the South Atlantic Ocean are biologically rich due to the mixing of warm and cold water from the mid-Atlantic and the Southern Ocean. This mixing upwells large quantities of plant nutrients to the surface, providing a source of food for numerous species who are, in turn, prey for larger organisms. Between the southern tips of South America and South Africa there is a strong air current known as the ‘Roaring Forties’, which causes large waves that contribute towards coastal erosion on islands and continents.
The longest mountain range in the world, the Mid Atlantic Ridge, runs along the centre of the Atlantic Ocean, although most of it is covered by water. Some parts of these mountains are visible above sea level, creating islands that and have been colonised by humans as well as animals and plants. There is also a range of underwater volcanoes, known as the Walvis Ridge, whose eruptions are responsible for the formation of many islands through the accumulation of volcanic debris.