by Daniel B. Botkin, originally published by Perigee Books, a division of Penguin/Putnam, 1999.

This book, originally published as “Passage of Discovery“, is an ecologist’s guide to the first half of the Lewis and Clark trail, their travels up the Missouri River from St. Louis to Three Forks, MT.  I have decided to share this book with the readers of my website, and I am going to present the entire book here, one chapter at a time, with a new chapter appearing each week.  There are more than 40 chapters.  If you follow along and read all of them, you will learn about the entire Missouri River as seen by Lewis and Clark at the beginning of the 19th century, and as I visited it during the 1990s to see what they had seen, and to learn how the countryside had changed.  Comparing what Lewis and Clark saw with what we see today is one of the best insights we can get of how nature and environment in American has changed since European settlement.   I hope you enjoy it and find it rewarding.

- Daniel B. Botkin

All of the chapters published thus far can be found in the Passage of Discovery category. Please note that they are listed in reverse order of date posted.

More books by Daniel Botkin are available for purchase from the Center For the Study Of the Environment bookstore.

41. Gates of the Mountains: Continents Collide and We Are Rafted Along in Their Wake

Traveling south on Interstate 15, about  65 miles south of Great Falls, take the exit to the Gates of the Mountains Recreation Area.  Drive east on a paved road about four miles to the recreation area.  The area between Great Falls and Helena is an excellent place to experience the river where it has cut a broad and scenic canyon — either by following an access road and trail system along the river or by boat or raft.  This is also a good area for bicycling and picnicking. There are several good locations between Great Falls and Helena to launch and take out a boat, among them Craig and Wolf Creek.  Boat trips into the Gates of the Mountains are available at the recreation area (406) 458-5421.

On Friday, July 19, 1805, the expedition neared the location of modern Helena, Montana and came to an area of impressive scenery.  In the evening Lewis wrote that “we entered much the most remarkable clifts that we have yet seen.”  They seemed to “rise from the waters edge on either side perpendicularly to the hight of about 1200 feet.”  It was impressive and a little forbidding. “Every object here wears a dark and gloomy aspect.  The tow[er]ing and projecting rocks in many places seem ready to tumble on us,” Lewis continued, then discussed the geology of the location, as Jefferson had instructed him to do. “The river appears to have forced it’s way through this immence body of solid rock for the distance of 5 3/4 miles and where it makes it’s exit below has thrown on either side vast collumns of rocks mountains high,” he wrote.   It was so steep that for more than a mile there was only “a few yards in extent on which a man could rest the soal of his foot.”  Then Lewis notes, with a bit of understatement, “It was late in the evening before I entered this place and was obliged to continue my route untill sometime after dark before I found a place sufficiently large to encamp my small party.”

The rocks were of many shades and hue, from black to “yelloish brown and light creem colourd yellow.”  Clark described the hills as made up of “a dark grey Stone & a redish brown intermixed and no one Clift is Solid rock, all the rocks of everry description is in Small pices appears to have been broken by Some Convulsion.” The snow-capped mountains were in view, so Lewis wrote that “from the singular appearance of this place I called it the gates of the rocky mountains.”

Today the land nearby the river is little developed and, in spite of the fact that Gates of the Mountains is now between the reservoirs of Holter and Hauser Dams on the Missouri, this area looks much as Lewis and Clark saw it. Large areas are becoming protected for conservation.  The Montana Land Reliance has obtained conservation easements on 24 ranches, totaling 73,000 acres, protecting almost 150 miles of streams and riverbanks.

In early May the daunting mountains are snow-capped, while the land just above the river is stark and dry, after an exceptionally warm early spring.  At the Gates of the Mountain Recreation Area it is hot, just the way Lewis described it.  “Whever we get a view of the lofty summits of the mountains the snow presents itself,” he wrote, “ alto’ we are almost suffocated in this confined vally with heat.”  Above the river Lewis saw Douglas fir and Ponderosa pine, a “scattering of timber on the river and in the valley.”  There were bighorn sheep, beaver, and otter.  These are still found in this area today and if if you are lucky you will see one of them. The area also remains a prime habitat for many birds, including pelicans, gulls, bald eagles, merganzers, meadowlarks, osprey, loons, Canada geese, peregrine falcons, and the turkey vulture — to name a few of the 118 species spotted over a year by Tim Crawford, director of the Gates of the Mountains Foundation.

Crawford maintains the recreation area and conducts boat tours on three large open air river boats. Tours run several times a day from Memorial Day until October and during this time you can travel on a boat through the same passage between the cliffs where Lewis and Clark came. A tour lasts close to two hours and includes a stop at Meriweather picnic area, where Crawfold speculates the expedition camped for a night.  From there, hikers may choose to explore the Gates of the Mountains wilderness area, catching a later boat ride back to shore.

We’re a little early for a tour, but we watch as people prepare their boats for the season.  The day is warm with a light breeze, the sky a deep blue.  Despite activity in the area, as we look out on the expanse of Holter Lake the scene is one of peace and tranquility, unlike the feeling Lewis must have had as the expedition fought its way through the canyon to find a safe place to spend the night.

The power of the river and the even more powerful forces that created the surrounding mountains capture your attention when you visit this location.  If you take a boat tour, you might experience the power of the river as it cuts through the mountainous canyons and get a sense of the awe men of the expedition must have felt as they saw the nearby canyon opening up to the valley in the distance and snow-capped mountains beyond.  Crawford tells us the tour boat runs in a sort of circle within the close canyon area, giving the impression to passengers of the mountains opening and closing, like a gate.

“The river appears to have woarn a passage just the width of it’s channel or 150 yrds,” Lewis wrote.  Confronted with such an amazing landscape, one can’t help wondering what brings us the mountains.   Since the early nineteenth century, soon after the Lewis and Clark journey, early geologists recognized the processes of mountain building and mountain erosion.  But no one had an explanation about how this mountain building came about; where came the energy for the incredible forces that must have been involved. The answer is one of the great discoveries of twentieth century geology.

In 1914 Alfred Wegener, a German scientist,  proposed a radical theory that continents moved – drifted – based on the similarity of fossils of animals and plants found on different continents, and the parallelism of coastlines of African and South America.  But at the time the theory was dismissed; no one could conceive of a source of energy for that process, and it was too radical an idea for the dominant theories about the constancy of nature.  As the understanding of radioactivity increased, it became clear that the decay of radioactive elements deep in the Earth provided a source of energy and with intense heat and pressure the material forming the crust of the Earth could act as a semi-liquid.  Today this theory of plate tectonics is well accepted.

The term tectonics comes from the Greek word for carpenter or builder.  And if the river is the painter, the continents are the carpenters.  Mountains come about from the collision of the gigantic continental plates in motion.  The deep earth acts as a semiliquid and the cooler, lighter continents float on the surface, shifting about over time. The “solid” earth on which we stand moves.  Heated from below, the continents are to the rest of the Earth as the skim that forms on the top of chocolate pudding.   The depth of the continents are no thicker relative to the rest of the planet than the skim on the pudding. When the huge continental plates collide, mountains form as mere wrinkles on the surface.

The plates move slowly, but not so slowly that the movement cannot be measured.  The average rate is about 3 ½  inches a year — 108 inches in the two hundred years since Lewis and Clark passed by the Gates of the Mountains.   So where we stand today the Missouri River is nine feet further west in terms of a fixed longitude on the Earth, than it was when Lewis and Clark were here.

Mountains have formed whenever continental plates collide, and some mountains are old, like the Appalachians of Virginia, the home of Lewis and Clark.  The Rocky Mountains Lewis and Clark confronted at Gates of the Mountain, and were soon to cross, are comparatively young mountains, too young to have been worn smooth by rivers like the Gallatin, Jefferson and Madison, the rivers that form the Missouri.  That geological youth meant that in 1804 as in our time the Rockies were still high, steep, and rough, a challenge unexpected by the expedition.

Geologist Brian Skinner has written that “it is not just the continents that move, it is the entire lithosphere. The continents, the ocean basins, and everything else on the surface of the Earth are moving along like passengers on large rafts; the rafts are huge plates of lithosphere that float on the underlying convecting material.”

The colliding continental plates that formed the Rockies began their mountain building here near the end of the age of the dinosaurs and at the beginning of the age of mammals, more than  60 million years ago.  They are built from even more ancient deposits. The lighter, brighter colored rocks are ancient limestones that geologists call part of the Madison formation.  These formed in a seabed, deposits of ancient seashells and other materials from biological processes, in the Mississippian, more than 300 million years ago, when shallow seas were common on many continents, especially in North America. The darker gray rocks that Clark described are even older.  They are Greyson Shale formed more than 600 million years ago.

Before the Rocky Mountains began to rise, when dinosaurs roamed this country, most of Montana was coastline — near sea level or under water, part of a shallow sea that covered two-thirds of the state.  After a continental plate previously in the Pacific Ocean collided with the plate that formed North America, several things happened: The colliding westward plate formed the land that is now Washington and Oregon, where Lewis and Clark were soon to go. The Rockies began to rise; the land to the east that had been seashore rose also above sea level, and the sea was forced to retreat eastward.

Before the Rocky Mountains there was no Missouri River, and without the Rocky Mountains there would still be none.  A river is a necessary consequence of a mountain range.  Water must flow downhill and as it does it begins to carry sediment and erode a path.  Tributaries begin to come together and form a young river.  The young river cuts steeply through the rocks.  But just how a river will form depends on bedrock, climate, and the stresses and strains, the cracks and bends, to which the rocks have been subjected over their longer history on the Earth.

And so at Gates of the Mountain you have a dramatic view, as did Lewis and Clark, of these primary forces that bring us the landscape from which begins the river that drains one-sixth of the continental United States.  If you are able to take one of the excursion boats through Gates of the Mountain, you can imagine that you are on the continental raft being carried on a journey into the collision of continental plates.  This is part of the new view of our planet, one of constant motion at all scales, all materials, all levels.  It is a great journey, symbolized by the travel of Lewis and Clark up the Missouri River through the Gates of the Mountains.