Mountains

I may be a prairie boy now, but I didn’t start out that way. I was born in Silver City, New Mexico, and as a small child, whenever we went back to New Mexico, I always said we were going to “my mountains.” This time of year, lots of people go to the mountains, even if they don’t claim ownership.

The Earth is mostly molten rock; the crust, several kilometres thick, floats on this “magma” in several distinct pieces, called “plates.” As these plates collide or pull apart, mountains form. Where plates collide, mountains can be either vast wrinkles, like you’d get in your car hood if you ran into a wall, or the edge of one plate thrust up into the sky by the edge of the other plate diving under it. Where plates pull apart, one edge tends to sink, leaving the other edge towering above it. Places where plates meet are also sites of volcanic activity, and volcanoes, too, build mountains, by piling up lava and ash.

A few low mountains are formed simply by erosion, in places where hard rock is surrounded by soft material. As the soft material erodes, the harder material is left standing.

The most famous mountains in North America are the Rockies, wrinkles caused by the collision of the North American and Pacific crustal plates between 65 million and 100 million years ago. They’ve been shaped since by erosion, which has a huge effect on mountains because air rising over a mountain cools and drops most of its moisture on the steep slopes. As the water runs down, it takes soil with it and wears away rock.

Mountains ranges can be either a single complex ridge of mountains, or a series of similar ridges. Several closely related parallel or linked ranges are called a system; an elongated series of systems is known as a chain; and an extensive complex of ranges, systems and chains is known as a belt, or cordillera. The Rockies are a chain; they’re part of the North American cordillera, which stretches from Alaska to Baja.

On a mountain peak the air seems thin because there’s less air above you pressing down. As a result, each breath you take has fewer air molecules packed into it than at sea level. This has other effects, too: water boils at a lower temperature (with less air pressure holding the water molecules together, it doesn’t take as much energy to make them fly apart into steam), it’s colder (air is an insulator) and you sunburn faster (air helps block ultraviolet rays).

Climbing a mountain takes you through a series of climates. In the Rockies, five vegetation zones are usually recognized. Below 1,645 metres, you get grassy plains. In the foothills, up to 2,135 metres, you’ll find sagebrush, juniper and pinon. From there to 2,750 metres, ponderosa pine, Douglas fir, lodgepole pine and aspen are most common. In the subalpine zone, up to 3,500 metres, englemann spruce, lodgepole pine and aspen grow. Above 3,500 metres, trees can’t survive; instead, you find alpine flowers and grasses, specially adapted to survive the rigors of high-altitude living. For example, many of them are tufted or hairy, grow very densely and have dark-green leaves, to help them retain heat. Their cells tend to be very small and contain high concentrations of soluble chemicals, which helps prevent freezing. Alpine plants are so efficient at gathering and hanging on to heat that some of them, as they release oxygen, melt the surrounding snow.

Although we think of the mountains as havens for wildlife, they actually support relatively few animals, for the same reason they support relatively few humans: the real estate tends to be vertical. Like the plants, the animals in the mountains have adapted to their rigorous life. Elk and bighorn sheep migrate downslope in autumn and upslope in spring. Ground squirrels hibernate to avoid winter; meadow voles remain active under the snow, which acts as an insulator. The Rocky Mountain goat scorns such wimpish ways of weathering winter, however: it does not migrate, hibernate or burrow. Instead, it has evolved a digestive tract that enables it to extract virtually all the available nourishment from its food, so it can feed all winter long.

The mountains seem to have an irresistible appeal for flatland folk, just ’cause they’re so dang different from what we look at every day. My advice is, don’t try to resist. Go! Enjoy!

And don’t worry. Even though they are “my” mountains, I don’t charge admission.

Permanent link to this article: https://edwardwillett.com/1996/07/mountains-2/

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