Beth Porter: The Coal We Burn

bethTwo things that have never failed me on our journey through Montana are the nightly series of lilac sky sunsets, encompassing fiery red and pink clouds and a lingering lightness, and an ever-changing landscape. As we rolled from Yellowstone County through Musselshell, Golden Valley, Wheatland, Meagher and currently Lewis and Clark County, I have witnessed the surrounding landscape evolve day by day. I have been mesmerized by the folded and slanted stratification of sandstone from ancient marine sediment and outcrops of archaic igneous dikes that have surpassed time and the rock that once overlaid it.

In the past weeks as we’ve pedaled toward the Rocky Mountain Front, we’ve had the pleasure of passing several other mountain ranges including the Crazy Mountains — a marvelous sight and one of my personal favorites — and the Big and Little Belt ranges. The hills are getting steeper, meaning harder uphill climbs and more fun downhill spirals. But coming from Oregon, where mountains make more sense to me (due to a subducting oceanic plate and active volcanoes), I was curious as to how these mountains all came to be in the middle of a continent with no obvious tectonic motion.

Early in our journey, as we rode from Billings to Roundup and then Ryegate, we were surrounded by broad plains of grasses and wildflowers and rolling golden hills — perfect for cattle to graze and cyclists to build massive quads. This is also where we came across the Signal Peak coal mine, an underground operation where they said they had at least 20 years of mining left in that seam (layer of coal) alone. As we toured the mine, they explained that two thirds of their roughly 300 employees work underground at up to 800-foot under burden. This work is dangerous, but in this instance that depth illustrates just how long ago that coal was formed. The miners are literally carving out a layer of earth that first settled there about 300 million years ago and has since been compacted and covered with much more.

But why can we dig up this specific layer and burn it for energy? Hundreds of millions of years ago, when the fossil fuels we know of now were first being created, the landscape of the earth was very different than it is today. Instead of deserts and rolling ranchlands, the earth was covered in swampy forests and shallow seas that were densely populated with carbon rich plant life and peat — or layers of accumulated biomass and decayed vegetation. This was known as the Carboniferous period because a high density of carbon was being stored, along with energy from the sun via photosynthesis, in plants that sank to the bottoms of the swamps as they died. All of this stored carbon and energy was just sitting in the swamps, slowly condensing, and eventually being covered with layers of other sediment. As millions of years passed, the pressure and heat from compaction and increasing depth transformed the biomass from peat to lignite and eventually to the coal we see today. While the production of coal is a natural process, this time span makes it non-renewable and modern day earth rarely has the right conditions to again stimulate this type of production.

All in all, between the Rocky Mountains and the Bakken Formation, Montana is a geologic jackpot and it is for this reason that it is rapidly being excavated. As we toured the mine, there was a plethora of machinery, conveyer belts and crushing machines, rapidly pulling the coal from the earth and processing it for consumption. We witnessed it flying from underground and then stood atop the massive black piles, ready to be loaded into a train and shipped over seas. It was an incredible experience, but the difference in time spans still blows my mind. Something that takes millions of years to form was being processed within hours. From the mind of a student of geology, it is efficient, but slightly unsettling.

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