Why Are the Rocky Mountains Higher and More Jagged Than the Appalachians?

The Appalachian mountain range is significantly older from a paleontological perspective compared to the Rocky Mountains. While the Rocky Mountains began to rise approximately 70 million years ago during the Laramide Orogeny, the Appalachian range experienced several significant geological events, with the first major rise occurring around 480 million years ago during the Ordovician Period.

The Role of Age in Mountain Characteristics

The standard answer is that the Appalachians are older mountains and have been subject to erosion for a longer period. This extended time has shaped the mountains to be more rounded. In contrast, the Rockies, being much younger, retain their more jagged and pointed features, which are more vulnerable to change, much like a tall person in an overhang.

One useful model to understand this can be created by observing the erosion of a snow or sand mound with a spiked top. As water, wind, and ice erode the peaks, the jagged edges are more easily worn down, leaving smoother, rounded tops. Similarly, natural weather events like hail storms can similarly smooth out a landscape, creating rounded shapes over time.

Geological Context and Erosion Patterns

Consider the immense geological context: Pangea formed around 335 million years ago and began breaking apart around 170-175 million years ago. The Appalachian Mountains are older than this massive supercontinent. Over the past 500 million years, the Appalachian mountains have experienced numerous climate changes and forces of erosion, leading to their current, more weathered and rounded appearance. Think about the majestic peaks these mountains once might have had before millions of years of erosion.

Glaciation Impact on the Rocky Mountains

The Rockies, on the other hand, were more recently affected by extensive glaciation, primarily in the Pleistocene epoch. This glaciation carved the peaks into the jagged shapes we see today. While the Ancestral Rockies, which predated the current Rocky Mountains, had a more similar appearance to the Appalachian range, this is because they too were subjected to significant erosion over millions of years.

The Himalayas, in comparison, are the youngest mountain range and continue to grow due to ongoing tectonic activity. Located at the boundary of the Indian Subcontinent Plate and the Asian Continental Plate, the Himalayas are still rising, growing roughly two inches per year. This constant upward thrust is why they retain their towering and jagged peaks. In contrast, the Rockies, despite being younger than the Himalayas, still retain their pointed features thanks to the recent effects of glaciation.

Conclusion: Understanding Mountain Characteristics

In summary, the difference in the geological age and the history of erosion play a significant role in the distinct characteristics of the Appalachian and Rocky Mountains. The Appalachians have been subject to a longer period of erosion, resulting in smoother, rounded peaks, while the Rockies, despite being a younger range, hold onto their jagged features due to recent glaciation events. Understanding these factors helps us appreciate the dynamic processes shaping our planet's landscape.