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A full "Flower Moon" rises off the horizon among the sandstone towers at Rock City north of Valier. The mushroom-like hoodoos form when sandstone layers erode at a different rate than their harder sedimentary rock caps.

KURT WILSON, Missoulian

VALIER — A rock band could shoot a pretty trippy video here.

Stephen King could set a creepy scene as well. Or with the Flower Moon rising in the May night sky, one could just marvel at the otherworldly oddness of Valier Rock City.

Located halfway between Cut Bank and Valier, this sandstone formation attracts determined nature lovers and occasional keggers. Watch out for lots of broken glass. In warm weather, watch out for lots of rattlesnakes. If it’s rained recently, watch out that you don’t lose your vehicle in the gumbo mud.

If that hasn’t scared you off, take a few hours on the road between Glacier and Yellowstone national parks to experience one of Montana’s sideshow attractions. The hoodoo towers sprouting among fields of wildflowers deserve attention.

“You turn right at the stoplight and keep going north,” Valier assistant librarian Duane Sheble directed. “You’ll pass the oil road in about 3 miles — keep going. When you come to the ‘dead end’ sign, keep taking the turkey track. You can’t miss it. Or if you do, you’ll be in the river.”

Sheble does not exaggerate. The rolling grasslands surrounding Valier play hide-and-seek with the horizon. One minute, the prairie extends forever. Pass a hump, and 80 miles of the Rocky Mountain Front leap into view. With even less warning, the toadstool towers of Valier Rock City appear. Throw a dirt clod across the formation, and you’ll never hear it land. That’s because it will sail over the 200-foot cliff above the Two Medicine River.

The 60-mile river ends just a few miles to the east, where it pours its sediment into the Marias River. The Marias in turn feeds the Missouri River near Virgelle, which leaves the Midwest via the Mississippi River. This gets mentioned because rocks from the Virgelle geologic formation have been found in the Mississippi Delta.

“You’d have no idea this river’s there, until you come to the edge and there’s a giant canyon,” said University of Montana sedimentary geologist Marc Hendrix. “That’s what results when the land surface gets lifted up while the river tries to stay at the same elevation.”

The prairies east of the Rocky Mountain Front used to form the western edge of the Cretaceous Interior Seaway, a shallow inland sea that covered much of the Midwest 80 million years ago. What was once barely above modern-day sea level elevation rose up nearly 5,000 vertical feet. Hendrix said the river remains determined to erode its way to that earlier state, one sandstone layer at a time.

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The full moon sets behind a formation of hoodoos at Rock City, located on a tiny swath of state land on a bluff above the confluence of Two Medicine River and Birch Creek.

The most expansive rock city occurs just east of the confluence of Two Medicine River and Birch Creek, on a tiny swath of state land. More rock groups can be seen up and down the canyon. The high bench on the river’s northwest side marks the southeast corner of the Blackfeet Indian Reservation.

Hoodoos form when a relatively hard sedimentary rock gets laid over much softer layers, and then water and wind cut channels through the formation. In Valier’s case, a reddish cap about a foot thick covered gray sandstone deposited in hundreds of 1- and 2-inch-deep layers. Eons of spring runoff floods must have passed through cracks in that cap, seeking paths of least resistance on their way down to the riverbed.

The “hard” or mineralized quality of the local water reversed what might seem the normal way of things. Hendrix said while sedimentary rock forms as water-borne material sinks to the bottom of a basin, groundwater can also wick upward through the layers. When it reaches the surface, the minerals fill in the gaps and harden.

“That cements the surrounding soil particles together and protects the sandstone layers beneath,” Hendrix said. “It takes a long time for that caprock to be eroded or destroyed. But eventually, you get a complicated gully system that breaks up the caprock and generates interesting land forms.”

The erosion leaves ranks of shapes resembling milk bottles, morel and bolete mushrooms, and interplanetary desk furniture. Some passages between the towers are wide enough for cattle to graze through. Others would pop a jacket button off a hobbit.

Where the reddish caps have worn away, the towers melt into beehive-like humps. The formation is so soft, a handful of nails left from some abandoned art project were embedded in the gray stone just by the weight of passing footsteps.

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Eons in the making, the hoodoos offer both a stark and beautiful landscape where one's imagination can run. The bright yellow locoweed flowers will vanish before the hot days of summer arrive.

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