OBSERVATIONS OF BURNING COAL VEINS AND RECOGNITION OF THE ORIGIN OF CLINKER BY MEMBERS OF THE LEWIS AND CLARK EXPEDITION IN NORTH DAKOTA

Members of the Corps of Discovery included a number of geological observations in their journal entries during their journey through the area that is now North Dakota in 1804-1806. Several of these entries related to observations of burning coal or the presence of clinker, rock that is baked or fused by heat generated from burning of coal. Meriwether Lewis and William Clark used volcanic terminology to describe these rocks, referring to the vesicular type of clinker as pumice stone and the molten clinker as lava. Using this terminology reflects their preconceived notions that these rocks were formed by volcanic processes. They sent a sample of each of these clinker varieties back to President Thomas Jefferson in a shipment from Fort Mandan. These clinker samples are housed at the Academy of Natural Sciences in Philadelphia and are among only a handful of the original 68 rock, mineral, and fossil specimens collected during the Lewis and Clark Expedition that are extant.

The Expedition first observed burning coal on April 8, 1805 in exposures of the Paleocene Sentinel Butte Formation along the Missouri River just north of Fort Mandan in what is now central North Dakota. Patrick Gass noted in his journal that the area had recently been a burning volcano, again indicating preconceived thoughts that volcanism had occurred in this area. The Corps also encountered burning coal on April 10, 1805 near present day Beulah Bay on Lake Sakakawea. Although Gass’s entry and the use of volcanic rock terminology indicates the explorers initially thought clinker was formed by volcanic processes, Lewis (April 16, 1805) correctly attributed the creation of clinker to burning coal. Clark accurately and succinctly described the process in an undated journal entry likely written the following winter at Fort Clatsop. As such, Lewis and Clark were the first to record the phenomenon of burning coal on the Northern Great Plains, the first to collect clinker specimens for scientific study, and the first to make scientific observations regarding how clinker is formed.

Clinker is forming today in North Dakota in areas where there are active coal bed fires. This phenomenon occurs less commonly than it did 200 years ago because prairie fires were more frequent as a result of prairie burning by Native Peoples to promote growth of grasses to attract bison.