Why are the applichian mountains more rounded and shorter than the Rocky Mountains?

The Appalachian Mountains are older than the Rocky Mountains and have undergone extensive erosion over millions of years, resulting in their more rounded and shorter profiles. In contrast, the Rockies are younger and have experienced more recent tectonic activity, leading to their steeper and more jagged peaks. Additionally, the Appalachian range has been shaped by different geological processes, including weathering and glaciation, contributing to its smoother, worn appearance.