Distinctly Montana Magazine

66 D I S T I N C T LY M O N TA N A M A G A Z I N E • S P R I N G 2 0 2 3 One of the most striking features of the Shonkin Sag is its deep canyon surrounded by tall cliffs. This depression was created by ero- sion and weathering, as water and wind gradu- ally wore away at the softer clay and shale lay- ers. The cliffs, on the other hand, were created by much older sandstone and volcanic rocks that are more resistant to erosion. Cathy Whitlock is an earth scientist and Re- gents Professor at Montana State University. As a geologist she has spent much time studying the history of geology, vegetation, and climate in the western U.S. She even spent time studying pollen samples of sediment cores taken from the bottom of Lost Lake to reconstruct the vegetation history of the Shonkin region since the last ice age. "The Shonkin Sag is an impressive landscape that was formed in a blink of an eye, geological- ly speaking," she said. "Many think of the land- scapes created by the release of Glacial Lake Missoula, but the Shonkin Sag is another fan- tastic example of a glacial outburst flood. And when the ice dam broke holding Glacial Lake Great Falls, the result was an enormous flood with tremendous erosion." No one knows for certain where the name "Shonkin" came from, but it is believed to origi- nate from a Blackfoot Indian chief by that name. Indigenous people, such as the Blackfoots, lived in this area for centuries before the arrival of Eu- ropeans. The name "Shonkin" is derived from the Blackfoot word "shonkan," which means "to be brave" or "to be fearless." Though there is a very small town named Shonkin, it is also the name given to this part of Chouteau County along the edge of the Highwood Mountains. An old grain elevator still stands today in the small town of Shonkin, which is about halfway between Geraldine and Highwood, Montana. The Chicago, Milwaukee, St. Paul and Pacific Rail- road built part of the Milwaukee Road inside the Shonkin Sag, which included a stop in Shonkin. The beautiful landscapes found along the Shonkin Sag have had a significant impact on art, too. Its rugged terrain, as well as the buttes and mountains that flank it, influenced the work of Charles Russell, one of the most famous West- ern artists of the 20th century. Before becoming an artist, Russell worked on a sheep ranch in the Judith Basin not far from the Shonkin Sag and the buttes nearby. The Sag's tall cliffs and deep canyons provided a sense of drama and grandeur that was central to his artistic vision. He used these dramatic landscapes to convey a sense of the vastness and wildness of the West, and to depict the struggles and triumphs of the people who lived and worked there. Anyone can experience the grandeur of the Shonkin Sag, though many parts of this beau- tiful landscape are not easily accessible or are located on private land. But for the parts that are easily seen, all you need to do is take Highway 331 north from Belt and drive 16 miles in the di- rection of Highwood. There you will notice the terrain change suddenly and the elevation drop. This is where you enter the Sag. On your left and right you will see erosion and land "sluff- ing" from the hillsides as gravity, water, and time slowly erodes the outer rim. Just before reaching Highwood, you will cross Highwood Creek. Though you can't see it from there, the Sag extends west along High- wood Creek another 10 miles and ends at the confluence of the Missouri River. Farther ahead on the road between Shonkin and Geraldine is arguably one of the most THE TIMELINE OF EVENTS THAT SHAPED THIS PORTION OF MONTANA: 80 TO 40 MILLION YEARS AGO Volcanos were active in central Montana. 50 MILLION YEARS AGO Highwood Mountains were formed because of volcanic activity. 2.6 MILLION YEARS AGO The Highwood volcano (and many other volcanos in the region) became dormant. The Shonkin Sag Laccolith was formed, and shortly thereafter Earth's glacial period be- gan. The Laurentide ice sheet covered huge swaths of North America, including eastern Montana, which formed several large gla- cial lakes. 1.5 MILLION YEARS AGO Pleistocene glacial Lake Missoula had its first cataclysmic flood that swept vast amounts of water across eastern Washing- ton and down the Columbia River Gorge. 17,000 TO 13,000 YEARS AGO The Laurentide ice sheet blocked the an- cient route of the Missouri River and creat- ed Glacial Lake Great Falls. 15,000 YEARS AGO The first Glacial Lake Great Falls outburst flood occurred, which carved out the Shonkin Sag. 15,000 AND 13,000 YEARS AGO Floods occurred several more times over the next 2,000-year period, moving water through the Shonkin Sag. One the channels would move large amounts of water over the Dry Falls, which forms what we today know as Lost Lake. 10,000 YEARS AGO The most recent ice age ended after one occurring almost every 100,000 years over the span of more than 2 million years. GREAT FALLS GREAT GREAT FALLS FALLS FORT FORT BENTON BENTON BIG BIG SANDY SANDY BOXELDER BOXELDER CONRAD CONRAD VALIER VALIER CHOTEAU CHOTEAU CASCADE CASCADE LEWISTOWN LEWISTOWN DENTON DENTON ULM ULM THE SHONKIN SAG IS ANOTHER FANTASTIC EXAMPLE OF A GLACIAL OUTBURST FLOOD. WHEN THE ICE DAM BROKE HOLDING GLACIAL LAKE GREAT FALLS, THE RESULT WAS AN ENORMOUS FLOOD WITH TREMENDOUS EROSION.

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