North Dakota Water Science Center
Lightning, prairie fires, and spontaneous combustion (due to the presence of heat and sulfur) may cause coal veins to burn. Once ignited, the coal veins burn slowly because of a lack of oxygen, and many veins burn for years. As the veins burn, the ground settles causing faults, as shown in the picture at right. These faults may emit gases, smoke, and sparks and also admit oxygen that keeps the coal veins burning.
The gas emission may affect the growth of nearby vegetation. At the Burning Coal Vein Campground near Amidon, normally bushy junipers have grown in columnar shapes around the cracks of a burning coal vein.
The heat generated by burning coal bakes nearby sediments to form a brick-like material called clinker. Lewis and Clark noticed this process and commented on "strata" of coal, "birnt earth," and "pumice stone" in the river bluffs along the Missouri and Little Missouri Rivers where layers of red clinker are visible in eroded buttes. The color of clinker varies depending on the minerals present in the sediment, but red is the most common and noticeable color.
Clinker is used for road surfacing in place of gravel in western North Dakota. Although clinker commonly is called scoria, scoria is not the appropriate term. Scoria and pumice stone (the term Lewis and Clark used for clinker) are the result of volcanic activity.
Bluemle, J. P., n.d., North Dakota’s Clinker: North Dakota Geological Survey North Dakota Notes No. 13 accessed November 21, 2002, at URL http://www.state.nd.us/ndgs/ndnotes/ndn13.htm.
Swan, K. D., May 15, 1946, Burning coal mine near Logging Camp Ranch, Little Missouri Valley north of Bowman: Forest Service Historical Photograph Collection, National Agricultural Library, Special Collections, Natural Phenomena accessed November 14, 2002, at URL http://www.nal.usda.gov/speccoll/collect/phenomena/.
Umber, h., ed., 1988, "Burning Coal Vein," Natural Areas of North Dakota. North Dakota Outdoors 50(8):2-25. Jamestown, ND: Northern Prairie Wildlife Research Center Home Page accessed November 21, 2002, at URL http://www.npwrc.usgs.gov/resource/habitat/natareas/index.htm (Version 16FEB99).
"Scoria," Photo glossary of volcano terms: U.S. Geological Survey
Volcano Hazards Program accessed November 12, 2002, at URL http://volcanoes.usgs.gov/Products/Pglossary/scoria.html.