GEOLOGIC INTERPRETIVE SIGNS ON THE LEWIS AND CLARK TRAIL IN MONTANA

The overriding challenge confronting informal geoscience education/interpretation for the public is capturing the audience's attention. Many people are more familiar and comfortable with historical or archeological information. But human history and prehistory occurred within a physical landscape, which often exerted a defining influence on the events. To make this point, we piggybacked geologic interpretive signs onto the history of the Lewis and Clark Expedition in Montana (1805-1806). The Expedition journals are full of geological observations and interactions that make good sign content. For example:

• A major Expedition goal was to locate the Continental Divide and determine if the route across it to the Pacific was navigable for trade -- that geology problem had a surprising resolution!

• The explorers were awed by the beauty of the Great Falls of the Missouri River and then delayed by a month-long portage, partly routed on the pre-Ice Age Missouri River valley!

• Salts released by Cretaceous marine shales into the Missouri made the explorers' eyes sore and gave them diarrhea.

• Lewis and Clark were the first to realize that the pervasive clinker of eastern Montana was not volcanic, but caused by coal beds burning underground.

Finding public-access sites where the signs would be welcome was an additional challenge. We eventually cooperated with the U.S. National Park Service, Bureau of Land Management, Bureau of Reclamation, Forest Service, Army Corps of Engineers, Montana Fish Wildlife & Parks, and several private entities to put a series of over 20 geological interpretive signs at sites along the Trail (to be displayed).