Question

The Appalachian Mountains are a range of mountains that run from the Southeast all the way to Acadia National Park in Maine. The Appalachian Mountains are not, on average, as tall as the Rocky Mountains to the west. What BEST explains the difference in average peak height for these two mountain ranges?
Responses
A The Rocky Mountains are older and have had a longer time to form, reaching higher altitudes in height.The Rocky Mountains are older and have had a longer time to form, reaching higher altitudes in height.
B The Appalachian Mountains are older and have been subjected to greater weathering and erosion, decreasing the height.The Appalachian Mountains are older and have been subjected to greater weathering and erosion, decreasing the height.
C The Appalachian Mountains have formed from minor volcanic eruptions while the Rocky Mountains formed from volcanic eruptions of greater magnitude.The Appalachian Mountains have formed from minor volcanic eruptions while the Rocky Mountains formed from volcanic eruptions of greater magnitude.
D The Rocky Mountains have been subjected to longer periods of deposition by the Colorado River, adding geologic mass to the base of the mountain range.The Rocky Mountains have been subjected to longer periods of deposition by the Colorado River, adding geologic mass to the base of the mountain range.

Answer 1

B. The Appalachian Mountains are much older (Paleozoic orogenies) and have been worn down by weathering and erosion for hundreds of millions of years, so their peaks are lower on average. The Rocky Mountains are geologically younger (Laramide uplift, mainly Late Cretaceous–early Cenozoic) and therefore retain higher, more rugged peaks. Options A, C, and D are incorrect because the Rockies are not older (A), the ranges are not primarily different because of volcanic eruption size (C), and river deposition does not explain the Rockies' greater peak heights (D).