To shutcho biscuit
They are formed as borders because they are formed naturally.
Because they are formed naturally. Therefore they are not manmade.
Spain's borders do no follow rivers.
The rivers
Tigris and Euphrates Rivers.
Some examples of natural borders separating countries include rivers (such as the Rio Grande between the US and Mexico), mountain ranges (like the Andes between Chile and Argentina), and bodies of water (like the English Channel between the UK and France). Oceans, deserts, and forests can also act as natural borders.
Rivers
There are four rivers that provide natural borders for the state of Florida. They are the Flint River, the Chattahoochee River, Saint Mary's River, and the Perdido River.
lakes
The Atlantic Ocean and rivers.
because they form a natural barrier