The Front Range of the Rockies

The panel's duck-billed hadrosaurs have an address south of here, near Choteau. In 1978 Marion Brandvold, who kept a rock shop in Bynum, showed Jack Horner and Bob Makela tiny bones she had found; they were baby duck-billed dinosaurs. In 1979 the two named the species Maiasaura peeblesorum, good mother reptile, for the Peebles family whose land held the nests, and it became Montana's state fossil in 1985. The nesting grounds were named an International Geoheritage Site in 2024. One correction to the panel: the thrust carried older rock east, not west.

What the plaque says

The Front Range of the Rockies The geological history of the front range of the Rocky Mountains is just as jumbled and complicated as the mountains appear from this vantage point. Geologic forces far to the west caused this remarkable backdrop. About seventy million years ago, the subduction of the Farallon tectonic plate under the North American plate gave rise to the Rockies. Over millions of years, the crust pushed upward and then slid the older rock west over the top of the younger rock. Called an overthrust fault, it pushed up, deformed, and folded the rocks as it moved. Pleistocene ice sheets later carved the rocks into the scrambled geological appearance we see today. The gray rocks are Madison Limestone. About 350 million years ago, much of Montana was submerged under a shallow sea. Billions of tiny marine creatures thrived in the water and when they died their bodies settled into the muck on the sea bed. After hundreds of millions of years of accumulation and many more millions of years it metamorphosed into the pale gray rocks of the front range. Because Madison Limestone resists weathering and erosion much better than most other kinds of rocks, it created the spectacular cliffs and dramatic ridges you see west of here. The front range range has been a paradise for wildlife for at least seventy million years. Duck-billed hadrosaurs and triceratops once roamed the shores of an ancient sea. Now it is the home of many different species, including grizzlies, elk, mountain lions, deer, wolves, moose, and rattlesnakes.

Where it stands

More markers nearby

• Dupuyer — steps away
• The 564th Missile Squadron — 8.7 mi
• Old Agency 1880-1894 — 19 mi
• Chief Mountain and Old North Trail — 22 mi