As you drive along Tipperary Road towards the Dry Creek Petrified Tree Environmental Education Area, you may notice red buttes around you. The reddish scoria or clinker is made of shale or sandstone that is fused underground in burning coal beds, turning red when the iron in the rock is exposed. Due to the abundance of scoria in the area, the material is used in road construction, giving roads in Johnson County their red color.
Wyoming has many extensive coal beds. Long ago, Wyoming was the site of an inland sea. Later swamps formed in the region during the Paleocene Era and supported vegetation. Peat, a form of vegetation, is created when leaves, branches, stems, trees, aquatic plants, etc. accumulate and decay. Over time, and with consistent accumulation of sand and mud from the flooding of rivers, peat becomes buried and finally turns into coal due to pressure from the layers above. The Powder River Basin, which includes Johnson County, contains thick seams of coal that run for hundreds of miles beneath the surface.