Formation and elevation patterns
The Himalayas are the highest range at roughly 8.8 kilometers (Everest) and still rising as India collides with Asia. The Andes are the longest range and form the spine of South America due to subduction of the Nazca plate. The Rocky Mountains and Appalachians are older, more eroded ranges in North America. The Alps formed by collision of European and African plates. Peak elevation correlates directly with tectonic activity: young mountains from active collisions are higher than old mountains worn down by weathering.
Mountains as climate and population barriers
Mountain ranges trap moisture and create rainshadows, profoundly affecting climate on either side. The Himalayas block monsoons, creating dry zones in Central Asia. The Andes separate wet Pacific slopes from dry inland basins. High mountains are difficult to cross, historically isolating populations and languages. Modern transportation has reduced this isolation, but mountains still determine regional climate and remain geopolitically significant.