Every sovereign state needs a line where its authority stops. Geographers sort these boundaries two ways: by what the line follows, and by when it was drawn compared with settlement.
Key idea
By what they follow, boundaries are physical (a river, mountain range or lake), cultural (a language or religion line) or geometric (a straight line of latitude or longitude). By when they were drawn, they are antecedent (before most settlement), subsequent (after settlement, as the land filled in), superimposed (forced on an area by outsiders) or relict (no longer working, but still visible).
| Type | Meaning | Example |
|---|---|---|
| Physical | Follows a natural feature | The Rio Grande (U.S. and Mexico); the Pyrenees (France and Spain); the Andes (Chile and Argentina) |
| Cultural | Follows a language, religion or ethnic line | Many borders in Europe roughly follow language areas |
| Geometric | A straight line, often a parallel or meridian | The 49th parallel between the U.S. and Canada; many lines across the Sahara |
| Antecedent | Drawn before most of today's settlement | The 49th parallel, set by treaties in 1818 and 1846 |
| Subsequent | Drawn after settlement, as groups settled their limits | Many European borders, fixed and refixed over centuries |
| Superimposed | Imposed by outside powers | Much of Africa, divided by European powers after the Berlin Conference (1884-1885) |
| Relict | No longer a boundary, still seen on the land | The former border between East and West Germany (1949-1990); the Great Wall of China |
Why it works
Why so many straight lines in Africa and the American West? A straight line is easy to draw on a map and to describe in a treaty ("along the 49th parallel"), even by people who have never seen the land. In Africa, European powers at and after the Berlin Conference divided the continent with little regard for the peoples living there; some peoples, such as the Somali, ended up split among several states.
Worked example: Two labels for one border
The U.S.-Canada border west of the Great Lakes runs along the 49th parallel, agreed in 1818 and 1846, when few settlers of either country lived there. Name its type by shape and by timing.
- Shape: it is a straight line of latitude, so it is geometric.
- Timing: it was drawn before most of today's settlement, so it is antecedent.
Answer: Geometric and antecedent.
Worked example: A wall that is no longer a border
East and West Germany reunited in 1990. Traces of the old border remain as a strip of land, museums and a line still visible in some statistics. What type of boundary is it now?
- It no longer divides two states.
- But you can still see it on the land and in the data.
- That is a relict boundary.
Answer: A relict boundary.
Common mistake
Thinking straight borders are natural. Straight lines usually mark borders drawn on maps by outsiders or by treaty, as in much of Africa and the western United States. Natural borders follow rivers and mountain crests, and they wiggle.