#1 - Strip Mine Near Colstrip, MT

Photo credit: Los Angeles Times, click on it to enlarge. No need to go underground
This photo shows a coal "strip mine" located near Colstrip, 90 miles east of Billings. Known as the Powder River Basin, this region contains thick seams of coal that formed as coastal swamps were buried by sediments millions of years ago. Strip mining can be used in this area because the coal seams are closer to the surface than seams located in the eastern United States where underground coal mines are more common. Strip mining is much safer because miners do not have to go underground where collapses, gas explosions, and lung diseases are risks.

The 1970's brought changes.
The majority of coal mined in the U.S. is from seams varying in thickness from 3 to 10 feet, although the seams in the Powder River Basin of southeastern Montana and northeastern Wyoming average 40 feet in thickness. Mining of this region's low-sulfur coal increased drastically in the early 1970s when the Clean air Act mandated that industries decrease emissions of sulfur dioxide, a gas that contributes to acid rain. The graph on the right shows how much coal was mined in Montana during the 1900's. The increase in the 1970's centered around the town of Colstrip - and in Wyoming, the town of Gillette became the hub of coal mining activity. Although Montana has more coal than any other state, Wyoming leads the way in the amount of coal mined. One reason for this is that Montana has a significant tax on coal sales, called the "Coal Severance Tax." Money collected from this tax is saved in a state "trust fund" for future generations.

What is it used for?
Montana's coal is primarily used for electricity generation. Some is burned at coal-fired power plants in Colstrip, with most mined coal (around 75%) shipped by rail to large, coal-fired power plants in the Midwest and Western states (like WA, OR), or exported internationally to countries like Japan, South Korea, and China for electricity generation. If you live in southern or western Montana, you've probably seen long trains loaded with coal on their way to these places.

Fossil fuels.
Coal, along with petroleum (oil), and natural gas are called "fossil fuels." Oil is used to make liquid fuels for trains, planes, and automobiles, and much of the natural gas is piped into homes where it is burned to heat air and water in furnaces and water heaters. Coal is not our only source of electricity, but coal-fired generators like those at Colstrip provide much of the electricity used in Montana. Hydroelectric dams provide the next biggest portion for Montanans. Nuclear plants (none in Montana) and wind generators are two other sources of electricity in the USA. Fossil fuels have been a focal point in the debate over climate change because carbon dioxide is emitted into the air as fossil fuels are burned. According to the "greenhouse theory" this carbon dioxide traps heat in our atmosphere, warming the world.

One Strip at a Time.
In the photo at the top of this page overburden has been removed, exposing a seam (layer of coal) that is ready to be mined. The long pile of rock (spoils) to the right is material recently removed from the strip of coal. The spoils sit atop the seam that was mined before the strip shown in the photo was exposed. After the exposed strip of coal is removed, the area to the left will become the next "strip". Its topsoil has already been taken away and stored. Next the coal will be removed and then eventually the broken up rock will be put back, smoothed out, the topsoil will be replaced, and the area will be seeded with native plants.

Term: overburden

Can you figure it out?
The diagram below is a cross-section of an area very similar to the area shown in the photo. Try to figure out which of the lettered areas on the diagram correspond to the following: coal, solid sedimentary rock layers, spoils, undisturbed topsoil, subsoil that has been returned, broken up rock that has been re-shaped, topsoil ready to be replanted, undisturbed subsoil.