The Mountains that Remade America, by Craig Jones
CIRES Fellow Craig Jones releases new book about how Sierra Nevada geology impacts us today
CIRES Fellow and Professor of Geology Craig Jones has released a new book: The Mountains that Remade America: How Sierra Nevada Geology Impacts Modern Life. The book explores the intimate connection between this well-known mountain range, its geology, and the evolution of human history in America. Jones gives us answers to questions like: Why do these mountains exist where they do? How have they changed the way Americans live? And just how different would the modern United States be today if these mountains had not formed?
See below for a Q&A with the author, and an excerpt from the book. Craig Jones blogs as the Grumpy Geophysicist.
CIRES: What drew you to the Sierra Nevada?
Jones: My interest began when I backpacked there in high school and college. Then, as a graduate student at MIT, I did my fieldwork in the Basin and Range area just to the east. During this time I kept maps taped up on the wall by my desk. I would look at them and think of questions like: Why is Mount Whitney so close to Death Valley? What caused such a high point and low point to be so close together?
A thought-provoking question. So, what happened next?
When I reached my postdoc at Caltech, I hoped to answer my questions. More specifically—to figure out what was under the Sierra Nevada. To do this, my team and I deployed a parade of “bubble gum and shoestring” seismometers in the southern Sierra. This meant we were borrowing equipment from all over: we were lent huge old prototype seismographs that we had to transport by mule and manpower into the wilderness. Out there in the backcountry, we didn’t even have an accurate clock. We had to jerry-rig a set-up to record accurate time.
So how did the Sierra Nevada come to be?
Many mountain ranges were easily understood in the wake of plate tectonics as the product of two plates moving together, squishing the crust and thickening it. Typically, the crust in the low interiors of continents is about 40 km thick. You can think of the crust is being like ice, and the mantle below being much like the ocean. So for example, if we look at an iceberg, using this analogy, we can see that the height of the iceberg is proportional to how thick it is. In a mountain formed by thickening crust, we should see this same type of proportionate thickness to height. But in the Sierra, we found the crust was only 35 to 40 km thick, a little less that areas sitting near sea level. So this begs the question: What happened to the mantle underneath? Subsequent experiments were about answering that question.
What is so interesting about the Sierra Nevada?
This region gives us a window to study a process that could be a universal one—without the complications that attend the same process elsewhere.
I’m interested in mountain ranges that don’t fit a typical plate tectonic cartoon. Let’s say you drew a map of plates in North America: you’d expect some hills and valleys in the San Andreas system, and east of that—nothing. So how is the Sierra Nevada even there? There’s also no evidence of earthquakes or trauma in the range itself, and that’s puzzling. Exceptions like this one give you the insight to try and understand the things that you don’t know. They aren’t the products of the processes of the things you understand—there’s something else going on.
Why write this book?
I've spent thirty years working here. Anytime I meet up with non-geoscientists, say like at Thanksgiving dinner, I get asked “So, what do you do?” I might explain the seismometers and crustal thickness and all that, but then the question is often “Why?” This book is kind of my answer to all those conversations.
So then… why include history?
There’s a scientific answer to why certain geology behaves the way it does—but it’s also fair to point out the geology of the Sierra Nevada had some extraordinary impacts to human history. And this is what’s missing from most history books. If you read histories, they will discuss, for example, the impacts of gold on people. But they won’t tell you how that gold got there—or that there are three different types of geologic gold deposits: Placer, paleoplacer (meaning ancient river deposits) and lode deposits. Historians don’t pick up on this and that this is a very unique characteristic of the Sierra. They just talk about how the gold changed things. But these three types of gold are why things changed so much. The science of the land is vital to truly understanding the history of its people.
And then there’s Yosemite Valley, for example, the first piece of land to be preserved as a park by the national government and so the cornerstone of the national park system. Its creation is rooted in its geology. And the Sierra Club, the first politically active environmental group, which emerged because of all the devastation associated with the Gold Rush was so close to seemingly virgin landscapes at risk of destruction. That juxtaposition, so central to changing views on conservation, is rooted in the Sierra's geology, too.
“Hardly an American soul has been untouched by the Sierra Nevada. You need only to have consumed a fruit cup or a handful of almonds, to count among your ancestors a former slave, or to benefit from living in the world’s number-one economy to cite an example of how a mountain range you may never have seen has altered your life. Even more directly, sitting in a cool movie theater on a hot summer day, visiting a national park, gambling in Las Vegas, or skiing down a mountain in the West, you owe your experience in no small part to the Sierra Nevada and the way it has shaped our nation’s historical development.
Certainly the Sierra Nevada is not alone among geographic features in influencing the course of American history. The same could be said for the Appalachian Mountains, the Mississippi River, the Great Plains, the Rocky Mountains, or any number of other landscape icons. What’s special about the Sierra? For one thing, the Sierra’s existence and characteristics have impacted our lives and our history in ways that are startlingly diverse, manifestly consequential, and often unexpected. Further, while other mountains and some large rivers arguably helped define America—the British prohibition on moving past the Appalachians, for example, energized colonial revolutionaries—the Sierra emerged on the national stage quite unexpectedly and in the process redefined the country. Of particular interest from my standpoint as a geologist, the enormous impact of the Sierra was far more tied to the peculiarities of the geologic history of the range than was the case with the Appalachians. Change any of a number of aspects of the deep-time history of the Sierra—move erosion back a few million years, shift a major fault a few miles east or west—and American history would have followed a dramatically different path.
For evidence of the Sierra Nevada’s imprint on our lives, consider the theatergoers I mentioned above. Aside from making appearances in movies—the Sierra has stood in for the Yukon’s Chilgoot Pass in Chaplin’s The Gold Rush and for Afghanistan in Iron Man, to name just two of several hundred guest shots—the Sierra has played a significant role in the development of Hollywood. The capital of the film industry has been in the greater Los Angeles area for about a century. While the locale’s appeal was mainly climatic, for the industry to grow there needed to be a vibrant city. By the beginning of the twentieth century, this was far from guaranteed. Los Angeles had pretty nearly exhausted its local water resources. City officials and leading businessmen in the region arranged for water to be brought from the Sierra, a process later memorialized (or vilified) in the movie Chinatown. This water would fuel the growth of the region and with it the film industry through a good part of the twentieth century. Not only was the water Sierran, but the development of the laws, culture, and infrastructure allowing the water to move over such distances owed a great deal to events in the range.”