The altitude and climate change
The atmosphere and Earth's interior are layered by density. Gravity pulls more strongly on denser materials so denser materials are at the center of things. Earth's core, at its center, is denser than its crust.
Weathering, plate tectonics, gulf stream, mountain roads, evaporation...
In the age of exploration.... Prince Henry showed the Portuguese how to navigate by studying the sun and stars until later on, he showed them the compass navigation as the only technology advance which made possible for them.