A Sawtooth Cross-Section

The natural world, wilderness, appears as a static object to most. There are perpetual weather changes, animals might pass by, perhaps you get lucky and see a rock-slide. On the large part, humans are evolved to only think of time in short spans – twenty years is a quarter of most peoples’ lives. And within twenty years, landscapes will most likely look the same as they do from now, barring some sort of extreme event.

Now imagine you are a lodgepole pine tree. They are abundant in the Sawtooths, with a countless amount along every trail and stream. The seeds begin to germinate in the aftermath of a fire, peeking their heads out into an ashy wasteland – tabula rasa. Year by year, flowers and grasses begin to enter from the boundaries, turning the black carbon into green leaves. The lodgepole grows densely in a new stand, each vying for the right mixture of sun.

Within ten years, the lodgepole has started to produce pinecones. They fall in between growing shrubs, nestled in the newly breaking soil. While they may not release their seeds for several years, the parent continues to grow. Tree rings record droughts, heavy rains, beetle infestations. Decades will pass, and the roots continue to rise. A single lodgepole can see multiple fires happen throughout its multiple century lifetime. It will only feel like a hot summer, a cyclical period of destruction and regrowth. Thousands of organisms may live and die within the rough bark, gnarling further and further through time. If it’s lucky, the lodgepole will live for over three hundred years, eventually collapsing into a stream where it will alter the water flow.

This is nothing new for the stream. Mapping the shape of a stream is similar to catching air in a fishnet. Moving water likes to meander, tying loops in weak soil banks, shortcutting its path through a depression in rock, turbulence at every bump it hits. Perhaps trees will fall (or be chewed and felled), and new ponds form. The stream continues to recreate itself over hundreds and thousands of years, more firmly embedding itself into the landscape. Fish evolve to spawn on its gravel beds, willow communities establish themselves as key ecosystems, slow water will create places for predator and prey to clash daily. The stream is still relatively new though, only a remnant of the silent giant that sank there before; glaciers.

Glaciation in the Sawtooths occurred in the Pleistocene era, only around 300,000 years ago. Giant forms of ice, some near a thousand feet at their tallest, tore through the landscape at a speed of ten inches per day. This occurred over thousands of years, pulling back like a handsaw each summer, and striking back through in the winter. Without these, there would likely be no lakes in the mountains, only puddles in the granite. There would be very few plants either – the continual back and forth erosion created the nutrient-rich soil that streams can travel through and plants can root into.

About fifty to a hundred million years before that, an even more impressive force tore through the ground, giving places for snow to start collecting into glaciers. An ancient coastline on the west side of Idaho crashed into the Pacific ocean plate, and over millions of years, magma began to rise and cool. The Sawtooth batholith and Idaho batholith, the two masses of granite that form the Sawtooth Mountains, laid underground for millions of years. To them, the extinction of the dinosaurs would have been a third-page newspaper article. Once they cooled and hardened, all they had was time – millions of years of erosion and plate movement put them where they are today, and continue to shape and move them constantly. They have seen every glacier, every stream, every lodgepole, every single grass blade be born, live, and fade away.

Deep time is something hard to consider. We can look at a lodgepole stand, cut through by a river, sitting on the side of the mountain. We might be able to see the Sawtooths fully in a spatial sense, but never in a temporal sense. Author Marcia Bjornerud wrote “I often feel I live not just in Wisconsin but in many Wisconsins.”, and the same is true for the Sawtooths. Every landscape has evidence of every previous geologic period – erratic boulders from the Quaternary glacial deposit, granite spires from Eocene batholithic formation, even gravel beds formed during the Holocene – our current era. To compress all of our geologic past into one period, ‘the past‘, is the same as calling a single sagebrush the Sawtooth Valley landscape. Despite this seemingly long period of subtle change, we are entering a new period.

The Anthropocene, the new proposed current geological era, is a time of perpetual change. While a river may take millennia to form into a new lake, humans can do it now in a few years through dams. Mining can move more soil in a single day than a glacier could in decades. Deforestation since 1990 has occurred at a rate of about 14000 acres per day worldwide. Based on some estimates, we are causing global erosion to happen ten times faster than it could be naturally.

This proposed geological era is not a prescription, it is a description. While we have caused our landscapes to change faster than in any other geological era, we are still able to reduce our impacts. The oldest known object in the Sawtooths is metamorphic rock under Thompson Peak, ancient schist dated to around two billion years old. From this, we know our world is resilient – despite the many changes that could have erased that rock forever, it has resided in the sun and may continue to do so for eons more. Whether you have only a day or a lifetime in the Sawtooth mountains, they will remain here longer than we can ever conceive, we just need to learn how to appreciate it now.