On my recent journey through Nebraska and eastern Wyoming, I was amazed at the number of coal trains that were streaming eastward; each more than a mile long, the trains were spaced by no more than a few miles. Originating at surface mines in the vicinity of Gillette, Wyoming, this caravan delivers a million tons of coal per day to power plants across the central and eastern U.S.
The Powder River Basin is defined by both its geography and its geology. Covering most of northeast Wyoming and part of southeast Montana, the basin stretches between the Bighorn Mountains of north-central Wyoming and the Black Hills of western South Dakota. Its southern border is the topographic divide between the North Platte watershed, to the south, and the watersheds of the Powder and Cheyenne Rivers to the north; more northern parts of the basin are also drained by the Tongue and Little Missouri Rivers. Geologically, the Powder River Basin is a broad bowl of Precambrian basement rock that gradually filled with sediments from the Paleozoic, Mesozoic and Cenozoic Eras; Cretaceous sandstones and shales, deposited by an inland seaway, form the thickest layer of sediments and lie just beneath Paleocene coal, the remnant of vast swamps and peat bogs that covered this region 60 million years ago. Compressed by younger Tertiary sediments, the plant debris turned to coal, since brought near the surface by the Miocene Uplift and subsequent erosion.
Powder River Basin coal, desired for its low sulfur and ash content, provides 40% of the coal used in the United States. Unfortunately (for coal advocates), much of this coal, buried under thick layers of Tertiary rock, is not economically accessible; nevertheless, seams near the surface should last for another 20 years or so and mining leases are still being granted by the U.S. government. While most Americans remain dependent on coal for their electric power, environmentalists continue to push for cleaner, renewable sources of energy; the Powder River Basin is, after all, the leading source of carbon-bearing fuel in our country.