Glaciers have caused extensive erosion in all of these places except: the Appalachian Mountains the northern United States the Cascade Mountains the Rocky Mountains
Answers
The Rocky Mountains formed 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began sliding underneath the North American plate. The angle of subduction was shallow, resulting in a broad belt of mountains running down western North America. Since then, further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks and valleys. At the end of the last ice age, humans began inhabiting the mountain range. After Europeans, such as Sir Alexander Mackenzie, and Americans, such as the Lewis and Clark expedition, began exploring the range, minerals and furs drove the initial economic exploitation of the mountains, although the range itself never experienced dense population.
Public parks and forest lands protect much of the mountain range, and they are popular tourist destinations, especially for hiking, camping, mountaineering, fishing, hunting, mountain biking, skiing, and snowboarding.
West of the Great Plains the United States seems to become a craggy land whose skyline is rarely without mountains—totally different from the open plains and rounded hills of the East. On a map the alignment of the two main chains—the Rocky Mountains on the east, the Pacific ranges on the west—tempts one to assume a geologic and hence topographic homogeneity. Nothing could be farther from the truth, for each chain is divided into widely disparate sections.