This week the southern part of Sudan is voting on whether to secede from the north after two decades of civil war. Like many other formerly colonized nations, the boundaries imposed by outsiders have little to do with physical or cultural geography. This BBC article includes a series of maps that do a good job of illustrating the north/south divide in Sudan.
Geographically, the country is divided between desert in the north and vegetation in the south as seen from this NASA image. The white line is the proposed boundary.
The ethnic and religious divides are also pretty apparent.
Comparing education, infant mortality, water and sanitation shows that north is doing much better than the south. On the maps below showing education levels (green) and sanitation and fresh water (blue), the darker areas are more advanced.
Of course oil is a big issue, with many of the oil fields being in the border region and the pipelines carrying the oil to the north for transport. The oil producing border area of Abyei, shaded below, is expected to hold a separate referendum in whether to join the south or not.
More maps and descriptions be be found on the BBC site. For an even more detailed map of Sudan's oil resources see this previous Map of the Week.
3 years ago