Surely, many of you have read the short story “Rip Van Winkle” by the American author Washington Irving. If not, the story recounts a man named Rip Van Winkle falling asleep in the Catskill Mountains of New York for 20 years.
This weaving of mountains and sleep seems to be a common premise of the literary world – as well as other crafts like music and the visual arts. I imagine due to the serenity felt when gazing upon soft ridges, for example. However, when I think of the mountains of Arizona – near my home – little about them makes me think of sleep.
I wrote previously on how hiking and climbing in different regions makes for entirely different experiences. Now I’m going to discuss some of the geoscientific reasons for these variations, focussing first on what makes the “sleepy”-type mountains so gentle. I’ve chosen to create a series of posts that focus on what I feel impacts my experiences the most: topography, vegetative cover, and climate.
Starting with topography: it’s a pretty broad term but generally refers to the spatial arrangement of physical features in a landscape. There are many related characteristics of mountainous landscapes like relief, prominence, and elevation that are more specific, so I’ll define those here.
Elevation is height of a topographic feature relative to something else – usually the mean elevation of the surface of the oceans (mean sea level). Relief is the difference in elevations (between a high point and low point) within a landscape. This can be expressed numerically by subtracting the elevations of the lowest point in the landscape from the highest point in the landscape. The larger the difference in elevation, the higher the relief. Prominence is similar to relief in that it is a measure of relative elevations in a landscape; however, it refers specifically to the height of a particular feature (like a mountain) relative to the surrounding terrain. Therefore, a mountain with great prominence is much higher than the other features in the landscape surrounding it.
So when I think of the mountainous landscapes of my youth – the “sleepy mountains” of Appalachia, these factors like elevation, relief, and prominence typically take low values. In fact, the highest elevation in Virginia – the state in which I grew up – is at Mt. Rogers and is a mere 5,729 ft (1,746 m). In Arizona – where I live now – the highest elevation is at Humphrey’s Peak and is more than double the elevation of Mt. Rogers at 12,637 ft (3,852 m).
And while Virginia has a varied topography with a lot of changes in elevation (and therefore relief), the relief is still less dramatic than some of the world’s other mountainous regions. For example, the average relief in Teton Range of Wyoming is ~3,000 ft (~900 m) – and while there are examples of these kind of changes in elevations in some parts of the Appalachians, the overall relief is relatively low.
When it comes to prominence, I return to the examples of Mt. Rogers (Virginia) versus Humphrey’s Peak (Arizona). The prominence of Humphrey’s Peak (6,039 ft (1,841 m)) is more than double that of Mt. Rogers (2,449 ft (746 m)). That means that while you’re in for a challenging hike in either case attempting a summit of these peaks, Humphrey’s Peak is definitely going to be more difficult.
Another factor that impacts my experience while hiking is the climate and the vegetative cover present in the landscape. The Appalachian mountains – particularly the central region where I grew up – are very lush and heavily vegetated. This actually makes geological field work a little more difficult in this region because exposure to the bedrock is more limited! So in regions with more vegetation, the paths are more likely to be covered in dirt and the trees are more likely to offer shade. These factors lead to a more pleasant outdoor experience in my opinion.
So why is this the case, that the central Appalachians are “sleepy”? Simply put, the reason is that the Appalachian mountain ranges are relatively old. The major mountain building event that led to the most of the uplift forming the Appalachians began about 325 million years ago and the mountains that formed as a result have been eroding since. Not only does this play a role in reducing the overall elevation, relief, and prominence but also, because collisional orogenesis in the region has ceased, the area is said to be “tectonically quiescent” or inactive and therefore there has been ample time for the landscape to adjust and for large plants to root and grow.
So if you ever find yourself with the urge to take a long nap in the great outdoors (hopefully not as long as our friend Rip Van Winkle!) perhaps head on out the the central Appalachians and enjoy some gentle, sleepy mountains. Just beware of black bears!