How did countries divide apart? How did the affect later landforms?

A divide is the elevated boundary separating areas that are drained by different river systems. For this reason, the feature is often called a drainage divide. Water flowing on one side of a divide empties into one body of water, while water flowing on the other side empties into another.

Divides range in height from a slight rise in the land to the crest of a mountain range. A divide on the low-lying flood plains of northern Belgium, for example, may rise no higher than a few meters. At the other extreme, the Andes—one of the longest mountain ranges in the world—form a divide in South America. A mountain range that forms a divide is called a dividing range.

Explanation:

new evidence is discovered.

oversights and errors are corrected,

new technology is applied to evidence.

health and medicine because people are dying from not being healthy or not strong enough medicine