Distinctly Montana Magazine

68 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 Lost Lake, when the final ice sheet retreated, the spigot of water was turned off, and the cataract feeding the falls dried up, leav- ing what we know as Lost Lake and the Dry Falls behind. "There was a lot more water in eastern Montana than there is today," said Whitlock. "Can you imagine what a Paleo Indian might have thought standing near the Dry Falls with all that wa- ter rushing over the top? It must have been an impressive sight." I had permission to visit and photograph Lost Lake some years ago. The following year, the landowners grew tired of people traipsing onto the property without first asking for permission and leaving trash behind. Today no one has access to the site except its landowners, the Bureau of Land Management and the State of Montana. When you leave the area on Highway 80, south from Geral- dine, look far off to the west just before you get to Square Butte, Montana. There you will see the rugged cliffs of the Shonkin Sag Laccolith, which is also a significant geological feature. This laccolith was formed by crystallization of magma slowly cooling below the surface of the earth at the same time the Highwood Mountains were formed. The Shonkin Sag Laccolith is notable for its size and the type of laccolith it is. It is made of several dif- ferent types of rock, including granite, syenite, and diorite. "It is not common to be able to view the cross section of a lac- colith, such as the Shonkin Sag Laccolith," said Whitlock. "This laccolith is well known among people who study volcanos where the lava never made it to the surface. The chance to look at its minerals on the side of a laccolith almost never happens." Once you drive past Square Butte you will then see the Chalk Cliffs on your left. This is a series of towering cliffs composed of cemented layers of sediment that were laid down on the bottom of the shallow sea that once covered the area. The thin strip of white rock in the middle is composed mostly of a marine fossil called Inoceramus, which is a type of clamshell. This is where the Chalk Cliffs get their name. They are also a popular spot for photographers and artists, as the cliffs provide yet another strik- ing contrast to the surrounding landscape. After driving through a valley filled with sagebrush, you will once again begin climbing out of the canyon and leave the Shonkin Sag behind. But before you do, you will pass through an area known to many as the Arrow Creek Slide. For more than 60 years it has been nearly impossible to keep asphalt on this section of Highway 80. What man has spent decades trying to build and maintain, Mother Nature has easily broken up and swept down the slopes of the Sag. Rugged topography and un- stable soils kept pushing the highway farther down the Arrow Creek Slide, quite possibly leaving behind a dangerous surprise for drivers along the route. About ten years ago, tens of millions of dollars were spent to fix the problem, but no one knows if the fix will last. Those familiar with the story of the Shonkin Sag, however, would likely to bet against it. Members of the geological community consider the Shonkin Sag one of the most significant geological landscapes in North America. Outside of Washington, Siberia, Iceland, and Alaska, there are few examples of laccoliths similar to the Shonkin Sag Laccolith anywhere in the world. And the story of the Shonkin Sag and Lost Lake is uniquely Montanan. "The Shonkin Sag region is vastly understudied," said Whit- lock. "It is significant and important to the history of Montana and should be protected." Montana has 55 state parks, most of which serve a recreation- al purpose. Some have suggested that parts of the Shonkin Sag should be turned into a state park and saved from development because they hold so much educational value. When you stand on the precipice of Lost Lake, it's hard to believe this place. It re- minds you both of Niagara Falls and a miniature Grand Canyon, and maybe it is something every future generation should have a chance to see. One day I hope people much smarter than me find the funds and temerity to purchase Lost Lake and the Shonkin Sag Lac- colith and turn them into a state park. Maybe Montana's 56th. Because if there is a landscape worth preserving anywhere in central Montana, whose impact has shaped the history of our entire state, it would be Lost Lake and this portion of the Shonkin Sag. Big Sag Ranch located inside the Shonkin Sag in Chouteau County, Montana. Round bales of hay on the plateau above the Shonkin Sag looking north toward Round Butte, one of a handful of buttes in the area between the Highwood Mountains and the Shonkin Sag that were seen in some of C.M. Russell's paintings.

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