I have always had a love for mountains. I’m not sure if it’s a spiritual connection, an emotional connection, or if there’s any reason for it at all, but I am always awed and humbled by their beauty and majesty. That’s why Jackson Hole in Teton County, Wyoming is perhaps my favorite place in the entire world. My family has a place there, about a mile from the Snake River, and I’ve been going there ever since I was an infant. Jackson is a place where I can get away from all the noise, traffic, and smog of Los Angeles, and even though it too is becoming a very popular tourist destination, I always cherish my time there.
With Yellowstone National Park to the north, the Wind River Range to the east, the Wyoming Range to the south, and the Teton Range to the west, Jackson truly is spectacular. It lies at the south-southeastern end of the large valley that spans from the northern boundary of Snake River Canyon at the south of town all the way up north into the Yellowstone valleys. Besides being able to name a few peaks here and there, I am woefully unfamiliar with the geology of the area. I know that a fault runs through the area, so I assume that the Tetons were formed as a result of seismic activity. Having been there so many times and having familiarized myself with various peaks, lakes, canyons, and buttes, and now having taken this geology class, I think that I’ll be able to explain some of the basic geological processes of Teton County’s past.
Above all, I know that the area was sculpted by glaciers. There is plenty of evidence for this, which, now that I have taken this class, I think I can recognize. Firstly, the mountains themselves are characteristic of a glacial past, with sharp jagged peaks, beautiful U-shaped valleys, canyons, and cirques. At the foot of these valleys lie several lakes. Two of the most popular hikes are Phelps Lake, which lies at the bottom of Death Canyon, and Jenny Lake, which lies at the bottom of Cascade Canyon. The U-shaped valleys are indicative of the presence of glaciers, as are the moraines that line the shores of the lakes. I had never understood what these rises were, but now that I have learned about glacial erosion and deposition, I recognize that, yes, the pine-covered little ridges that surround these lakes are in fact glacial moraines. As I write this, more and more things pop into my mind as evidence of the presence of glaciers. At Phelps Lake, the southernmost lake in Grand Teton National Park, there is what everyone calls the Jump Rock. Self-explanatory: there is a huge 30-something foot boulder sitting on the shore of the lake and protruding out into the water. Besides, along the trails to all these lakes lie humongous boulders that, I now know, could only have been deposited by glaciers. I would like to go to one of these moraines and dig up the soil to try to see firsthand the glacial sediment left behind.
However, these lakes are approximately a thirty-minute drive from the house, and so I do not see them everyday. But I do see evidence of a glacial past right on our property. I have spent countless hours walking along the Snake River, inner-tubing down it, and throwing rocks into it. Every year, though, it looks different––there are new channels, new islands, and the few beaches that there are also seem to move. I had always thought this had to do with the dam at its headwaters at Yellowstone Lake and Jackson Lake, and while how much water is released by the dam may in fact affect the river’s appearance, I now know that it is mainly because the Snake is a braided river. Although it is not coming directly from a glacier, braided rivers are characteristically always creating new and different channels over time. Of course, I think this now, being able to recognize the growing and shrinking of mid-channel bars and how crystal-clear the water is. It is only a gentle braided river towards its headwaters, however, as it soon becomes narrow and deep as it carves its way through menacing Snake River Canyon, where it eventually leaves Wyoming and enters Idaho. Also on our property, though, is a small hill, no taller than 100 feet, that, to me, has always looked like a coffin. I have not been to it enough times to remember its shape exactly, but now I know it could either be a roche moutonnee, a drumlin, or even an esker. Because there is not one side that is significantly steeper than the other and because it is rather straight in shape, my guess is that it is a drumlin. To know for certain, though, I would have to go out to it and dig into it to see if it is made up of unsorted or sorted sediment.
Scattered throughout the valley are several buttes. However, they don’t really look like Devil’s Tower or the buttes of the deserts of the American Southwest, so I have never understood why they are called buttes in Jackson. I guess I assumed that they were just a different type of butte, but now I think that they could in fact be roche moutonnees because they generally have a steep side and a more gradual side. My only hesitation in thinking that they’re roche moutonnees is how large they are. Of course, they look like gentle rolling hills when standing in the Tetons, but from the valley floor, they are enormous, often a mile in length and a thousand feet high. Are roche moutonnees that big? Compositionally, are they made up of bedrock or till? Could they be enormous boulders that were left behind by glaciers before the glaciers in the last ice age, and then the glaciers from the most recent ice age carved them out? They are not curvy, but some slopes are rather sandy, so are some of these depositions sandy kames? The more I think about it, the more questions I have, so I would have to look at a surficial geologic map to look at the topography and the sediment types that make up these formations.
All this new knowledge and all these new questions have only made me want to know more. Having been going to Jackson for so long, I never even thought to look at it through a geologic lens, but hopefully now, next time I go, I can appreciate it in a new light. What did the valley look like before the last ice age? How much has the valley changed morphologically since that time? What geologic processes are happening there now? For many years, the Army Corps of Engineers have been creating and regulating the levees that line the Snake River and Gros Ventre River down to Snake River Canyon, so what would the valley look like if (1) there was no dam, and (2) if there were no levees to protect from flooding? Is the vast sagebrush-covered prairie the river’s floodplain, or the outwash plain from the glaciers? Both? What will the valley look like 10,000 years from now? 100,000? As all these questions rush through my mind, I can’t help but wonder how inconsequential we are. Yes, we have left our geologic mark from fossil fuel burning, but we’ve only been emitting for the past couple hundred years. That period of time is insignificant when you think about Earth history as a whole. During the first lab and in the readings for the first lab, it was calculated that if Earth’s history were spread out on someone’s wingspan, human history would be at the tip of your fingernail. That is mindboggling. To think so much of ourselves given how little time we have been around seems almost sacrilegious. This is not to say that nothing matters; I think we should strive to do as much good in the world as we can and make the most of the time that is given to us, but no matter how much we may think we are in control, we are not and never have been. Geologic processes will continue, cycles will continue, and change will continue, just as we as a species continue to put ourselves above others. Perhaps that is why I have always liked mountains: they provide me an opportunity to reflect on our insignificance and how everything is subject to the geologic processes that govern the world.
Liam Flockhart Ford