Final answer:
The three largest mountain ranges in the US are the Pacific Mountain system, Appalachian Mountains, and the Rocky Mountains.
Step-by-step explanation:
The three largest mountain ranges in the US are the Pacific Mountain system, Appalachian Mountains, and the Rocky Mountains.
The Pacific Mountain system, notably different from the Rockies, extends from Mexico to Alaska and includes diverse ranges such as the Coast Range of British Columbia, the Cascades, and the Sierra Nevada.
The Rocky Mountains, also known as the Spine of the Continent, stretch from the Brooks Range of Alaska through the United States to the uplands of Western Mexico.
Between these mountain systems lies intricate geology including the Columbia Plateau, known for its volcanic rocks and the classic geysers of Yellowstone National Park, as well as the Colorado Plateau, characterized by mostly horizontal layers of sedimentary rock rich in fossils.
Southeast of this is the Basin and Range Province, recognized by its horsts and grabens landscape.
The Appalachian Mountains have a complex geology resulting from ancient collisions, with their present form spanning rolling hills mostly across the Southeastern United States.