Africa’s population is the youngest amongst all the continents, the median age in 2012 was 19.7, when the worldwide median age was 30.4. Africa straddles the equator and the prime meridian. It is the only continent to stretch from the northern temperate to southern temperate zones. The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.
The continent is cut almost equally in two by the Equator, so that most of Africa lies within the tropical region, bounded on the north by the Tropic of Cancer and on the south by the Tropic of Capricorn. The whole of Africa can be considered as a vast plateau rising steeply from narrow coastal strips and consisting of ancient crystalline rocks.