A major part of the resource industry in Indiana is the mining of coal. Coal commands a much higher price than limestone or sand and gravel, and thus can be economically shipped longer distances from where it is mined.
Where is Coal Mined?
Coal mining takes place in southwest Indiana, primarily in counties that border Illinois between the cities of Terre Haute and Evansville. This coal mining is also continued on in southeastern Illinois. The coal in Indiana formed in a geologic structure known as the Illinois Basin, which is a series of thick, buried sedimentary rocks deposited in the Pennsylvanian time period. When these rocks were deposited, Indiana was in a tropical location (remember: plate tectonics causes continents to move around) that included dense swampland similar to the Everglades in Florida. This organic material piled up over geologic time to form thick layers of organic material that did not decay. Over geologic time, the pressure of overlying material converted the organic material into coal. This coal is intermixed with the sedimentary rocks of sandstone and shale.
Coal is typically easy to locate since it occurs in layers that extend over long distances. The challenge is usually finding a coal layer that is near the surface and away from the groundwater table.
This strip mine near Phillipsburg, Pennsylvania is representative of a typical strip mine operation. The photo has been labeled by Pennsylvania's environmental regulatory agency. This gives you a sense of the amount of overburden that must be moved to access the coal. (Photo: PA DEP.)
Coal is only exposed in southwest Indiana, other areas of the state either never had these thick organic deposits, or they were eroded away. If the coal occurs in thick enough layers, usually one meter or greater, it is usually economical to mine the coal.
Who Uses Coal?
The primary users of coal are the electric utility industry. Most electricity in Indiana is derived from burning coal, so most coal mined in Indiana serves the power plants in Illinois and Indiana. One railroad company, the Indiana Railroad, gets most of its business from hauling coal from mines in southwest Indiana and adjacent Illinois to power plants in Indiana. Other major users include institutions and large facilities (corporate campuses, hospitals, colleges, and manufacturing plants) that burn coal on site to produce electricity or steam to heat and cool facilities.
How is Coal Mined?
Front end loaders drive on top of a coal seam in a strip mine in southern Indiana. Once large equipment removes the overburden, the coal is easily scooped up. (Photo: Indiana Geological Survey.)
Coal is extracted by either strip mining, where the overburden is dug away and removed and the coal is extracted by surface equipment, or it is extracted by underground mining. Unlike other mineral resources, coal tends to occur in relatively thin layers, usually no more than 30 feet thick, and more typically 4-8 feet thick.
Strip mining is the preferred practice in Indiana, where coal resources are fairly close to the surface. Like limestone quarrying, explosives are used to break the overburden (waste rock) overlying the coal. The coal itself is soft, and can be removed by heavy equipment. Surface mining is much cheaper, but has much higher environmental costs since it completely destroys the landscape, requiring remediation.
There are approximately seven underground coal mines in Indiana. All of these mines use the "room and pillar" method, meaning they have to leave some coal behind as pillars to prevent the mine from collapsing. While there are far fewer active underground mines, there are many abandoned underground mines in southwestern Indiana dating back 150 years or more.
Because of the spike in global coal prices due to increasing energy demands (including spikes in the price of oil, which is also used for electric generation) mine operators are mining in riskier locations via underground mining. Many risky locations are reopened abandoned mines from the 1800s and 1900s that are being "re-mined" to remove coal using newer technology not available then. As a result, several bad accidents involving old mines (and poor safety practices) resulted in the August 2003 "9 Alive" mine rescue in Sipesville, Pennsylvania. There, an active mine in Pennsylvania flooded when it hit groundwater stored in an unknown abandoned mine, trapping nine miners several hundred feet below ground. Another accident in 2007 in Crandall Canyon, Utah involved a collapse of "pillars"removed nearby pillars in an abandoned mine, a dangerous technique. The result killed six miners and three rescuers.
Another recent accident in April of 2010 at the Massey Energy Company Mine in Montcoal, West Virginia where 25 people were killed in an explosion continue to highlight the human cost of mining, an industry that accepts that safety violations are “ unfortunately a normal part of the mining process” (Don L. Blankenship, Chief Executive, Massey Energy Company). (The links in this paragraph are not required reading.)