Cliffs High and Steep

By editor

Lincoln, Lewis and Clark County, Montana

In the summer of 1806, Meriwether Lewis, having separated from William Clark’s party at Travelers’ Rest near what is now Missoula, embarked on a solitary journey eastward over the Continental Divide by a route less traveled than that of his companion. On July 7, Lewis and his small party crossed what the Salish people long before had known as a vital passage through the mountains -- now called Lewis and Clark Pass, at an elevation of 6,325 feet. From this vantage, the eastern slopes fall away toward the Sun River valley and the vast plains beyond, a landscape both stark and wild, where the Rocky Mountain front meets the broad horizon.

The Salish, or Flathead people, had for generations used this pass as a gateway between their forested homelands and the buffalo-rich plains to the east. Their path, worn by countless feet and hooves, was a natural corridor through the rugged mountains, a route of trade and hunting that Lewis recognized immediately on his crossing. In his journal, Lewis described the pass plainly yet appreciatively, noting “an excellent road” and remarking on the “timber and open meadows” that carpeted the eastern descent. This route allowed him to bypass the longer, more arduous journey down the Yellowstone River taken by Clark, offering a more direct path to the Missouri River basin.

Beneath the pass lies the Blackfoot River, carving its way through ancient rock, exposing in its canyon walls the deep history of this land. These cliffs rise high and steep, fashioned from the Precambrian Belt Supergroup formations -- sedimentary rocks laid down in a shallow inland sea more than a billion years ago, long before the age of dinosaurs or even the Cambrian explosion of life. The layers here tell of ancient mudflats, tidal pools, and microbial mats, preserved in stone with an exquisite clarity that geologists today prize. The river’s relentless flow has worn away the softer layers over millions of years, revealing vertical dikes and laccoliths formed much later during the Cretaceous period, about 75 million years ago.

These volcanic intrusions belong to the Adel Mountain Volcanics, a sprawling sheet of volcanic rock over 40 miles long and 20 miles wide, remnants of a violent geological episode when magma forced its way into the earth’s crust. This magma did not always erupt explosively to the surface; instead, it often squeezed into cracks, pushing the walls apart and forming dikes that now appear as nearly perpendicular stone walls climbing the canyon sides. Horizontal intrusions, or laccoliths, like Square Butte, Shaw Butte, and Cascade Butte, rose beneath the surface, lifting the overlying strata into domes and cliffs that dominate the landscape between Ulm and Cascade, Montana.

This volcanic activity occurred along the Great Falls Tectonic Zone, a profound weakness in the earth’s crust created over a billion years ago when two continental plates collided. This ancient suture not only shaped the regional geology but also influenced the topography and hydrology that Lewis and Clark encountered. The Adel Mountain Volcanics’ rugged cliffs and dikes bear silent witness to these primordial events, carved into sharp relief by the ceaseless work of erosion and time.

Lewis’s observations, though made with the limited geological knowledge of his era, reveal a keen eye and respect for the land’s natural features. He wrote of the “cliffs high and steep” that lined the Blackfoot River canyon, and despite complaints about mosquitoes and prickly pear cactus, the Corps of Discovery recognized the significance of the volcanic formations. Their journals capture a moment when the overwhelming scale of geologic time and process was beginning to dawn on explorers who had crossed a continent largely unknown to Euro-Americans.

Today, Lewis and Clark Pass forms part of the Lewis and Clark National Historic Trail, a corridor preserving the route of these early explorers. From the Alice Creek trailhead, about twelve miles east of Lincoln, Montana, hikers can ascend to the pass, retracing the footsteps of the Salish hunters and Meriwether Lewis himself. Standing at the summit, one beholds the same panorama that greeted Lewis on that July day -- the forested mountains rolling down to open meadows, then the rocky front giving way to the endless plains, a vantage both commanding and humbling.

The pass and its surrounding geology provide a tangible connection to deep time and human history, where the earth’s ancient processes and the movements of peoples intersect. The enduring cliffs and volcanic ridges speak of a land shaped by fire and water, of continental collisions and volcanic eruptions, of rivers cutting through stone over epochs. Meriwether Lewis’s journey here was not merely a passage across a mountain range but a crossing into the immense story recorded in rock and river.

In reflecting on these cliffs, one might recall the words of Lewis himself, who, though primarily focused on his mission of exploration and diplomacy, could not help but acknowledge the grandeur before him: “The road over the mountains is difficult, but the prospect from the summit is one of the finest I have ever beheld.” This succinct statement captures both the challenge and the reward of venturing into the wild country of Montana -- a place where natural history reveals itself in towering cliffs, volcanic ridges, and ancient rock layers.

As we walk these trails today, the shadows lengthen over the jagged dikes and laccoliths, and the Blackfoot River murmurs far below, its waters still tracing the paths carved by deep time. The cliffs high and steep endure, inviting contemplation of the forces that shaped them and the people who have used this rugged corridor for centuries.

See also

• Cliffs High and Steep at Lincoln, Lewis and Clark County
• Lewis and Clark Pass at Lincoln, Lewis and Clark County
• Crossing Lewis and Clark Pass at Lincoln, Lewis and Clark County