The Rocky Mountains run from Canada down through the western United States.

The longer version

A long belt of ranges forms where the crust has been compressed and uplifted over a wide region. Unlike a single chain from one plate boundary, this system includes many parallel ranges, basins and plateaus built during several episodes of mountain building spread over a long span of time.

Erosion has since cut deep valleys and exposed ancient rock. The ranges act as a barrier to moist air moving inland, creating drier conditions on the eastern side and shaping river systems that drain in both directions. High passes allow roads and railways to cross at manageable gradients, and snowmelt feeds rivers far downstream.

Where this entry sits

These facts wander across maps, borders, deserts, rivers, mountains, and the extreme corners of the natural world. Each one is short and self-contained, offering a small surprise about places you may never visit rather than anything you actually need. The full list sits on the Geography page, where every entry is listed in order.