Professor outlines Lewis and Clark–themed geologic road‑sign project across Montana

Sheila Roberts, a professor of geology at the University of Montana Western, described a years‑long project to place interpretive geologic road signs at Lewis and Clark‑related sites across Montana and said the effort was funded by a federal grant routed through the Montana Department of Transportation. “Thomas and I got together and said, ‘We should build a legacy of geologic road signs for Montana,’ ” Roberts said.

The project grew from Roberts’s experience seeing geologic signs in Wyoming and from the Lewis and Clark journals. Roberts told the audience that she and co‑professor Rob Thomas designed signs to tie geological interpretation to places Lewis and Clark described, and to use the expedition’s narratives as a consistent theme so signs could be placed across a large part of the state. “We got about a third of what we asked for, which is typical,” she said of project funding.

Roberts said the team focused on sites where the geology is visible and public access (or long‑term private permission) existed. They worked primarily with the National Park Service, Montana state parks, the Bureau of Land Management and the U.S. Forest Service, and placed signs at a mix of park‑maintained viewpoints and cooperating private sites. Examples Roberts described include a sign at the Fort Union Trading Post parking area on the Montana side of the state line (the trading post itself is in North Dakota), markers at Milk River overlooks and James Kipp Recreation Area, interpretive panels in the Terry Badlands, and multiple signs in the Great Falls and Gates of the Mountains area.

Roberts used the Lewis and Clark journals to locate moments when the expedition interacted with the landscape — for example, Clark’s observation of large boulders and glacial erratics at Milk River, and Lewis’s extended description of the Great Falls. She emphasized that Lewis and Clark often recorded biological and human observations but included geological notes that could be interpreted today. Roberts also described geological features the signs explain: the regionally widespread Madison limestone that forms cliffs and prominent outcrops; “clinker” formed when burning coal beds baked overlying rock; and the Belt Basin rocks around Missoula that formed roughly 1,400–1,500 million years ago.

The presentation included geothermal and igneous features tied to the expedition route. Roberts said the Lolo (Lolo Batholith) rock and local hot springs were sites where the project placed signs; she gave an approximate age for the Lolo batholith as about 50 million years and discussed how deep fractures allow rain and snowmelt to heat at depth and return as springs. Roberts provided outlet temperatures cited in the talk for the springs discussed and noted the project put signs at Lolo Hot Springs and Jackson Hot Springs where private site owners agreed to host panels.

Roberts said practical limits governed site selection: the team needed visible geologic features and reassurance that site hosts would allow long‑term public access. When money ran out, the program stopped adding signs; a statewide map the presenter displayed shows current sign locations and gaps. Roberts also noted an online resource with images and sign texts at the University of Montana Western website (www.umwestern.edu/enviroside) and said co‑organizer Tom served as the project webmaster.

Roberts framed the project as public outreach and landscape interpretation: she described Lewis and Clark’s journals as a tool to draw people’s attention to deep geologic time and to connect human history to the physical landscape in Montana. She said the signs aim to help visitors see features such as glacial erratics, remnants of ancient seaways, and igneous bodies exposed at the surface. Questions from the audience addressed details such as specific site locations, rock identifications, and the origin of booms heard historically at Great Falls; Roberts offered geologic explanations where possible and acknowledged some historical observations remain unexplained.

The presentation concluded with Roberts directing attendees to the project’s web pages for full sign texts and a map of installed panels. She said the signs are displayed in national‑park–style frames at the listed sites and that contributors included federal and state land managers and private hosts; she encouraged visitors and educators to use the online materials.