The United States’ highest rate of coal production is in Wyoming, with almost 4 million short tons extracted in 2004. The majority of this coal is burned to generate electrical power within the United States, but a small percentage is also goes to Spain and Canada. The Powder River Basin in the northeastern portion of the state is the most productive of Wyoming’s coal fields. The extensive coal deposits—ranging in thickness from 21 to 53 meters (70 to 175 feet)—formed over 38-66 million years ago. The source of organic material for the coal originated in swamps, estuaries, and deltas associated with the regression (retreat) of a large inland seaway that occupied central North America during the Cretaceous Period, which spanned the years between about 144 to 65 million years ago.
Since the mid- to late 1990s, the number and size of coal mines known as mountaintop removal mines increased dramatically in parts of Virginia, West Virginia, Pennsylvania, and Kentucky. The final step in processing this coal creates sludge that contains coal dust, sediment, and possibly heavy metals and chemicals. Mine operators contain the coal sludge in nearby valleys, behind huge earthen dams known as valley fills.
Surface mines and fly-ash deposits in the Tuzla Basin reveal the region’ long history as a coal-production hub for Bosnia and Herzegovina. This image of the altered landscape was captured on September 21, 2003.
Mountaintop removal mining dramatically changes the topography across thousands of acres. Mountaintop removal mining alters this topography by reducing the elevation of the ridge lines, flattening out the steep slopes, and also by filling in hollows and stream beds with the excess rock and dirt that once topped the mountains.