Why are the Appalachians smaller than the Rockies?

Answer 1

When the Supercontinent broke apart, the Appalachian Mountains were forming. Their formation was part of the tetonic plate activity going on at that time, and scientists believe the Appalachians once had active volcanos. So the Appalachian Mountains are millions of years older than the Rocky Mountains in the west. Therefore, the Appalachians have also had millions of years of erosion; though still having high elevations, they are more much more rounded than the Rocky's peaks, and have lush valleys surrounding the Appalachians.

Answer 2

The Appalachians are older and have been eroded over time, resulting in lower elevations compared to the Rockies. The Rockies are geologically younger and have experienced more recent tectonic activity, which has led to higher peaks and more rugged terrain.