Cliffs of Big Sheep Canyon

by Rick & Susie Graetz
Big Sheep Creek Limestone Caves
Big Sheep Creek | Rick & Susie Graetz

Big Sheep Canyon west of Lima, Montana separates the Lima Peaks from the Tendoy Mountains. These cliffs consist of Madison Limestone – calcium carbonate as limestone is called in chemistry speak – it is a compound (CaCO3) formed by carbon, oxygen, and calcium. The rocks dissolve when they encounter acidic groundwater forming, caves, sinkholes, and a rough surface.

Weathering from snowmelt, rain and wind further enlarge them. In geologic talk they are referred to as karst features.

Warm springs seeping from the rock beds helps keep the creek flowing at a steady pace offsetting summer flood irrigation taking place upstream in the Big Sheep Creek Basin.