The coal formation process involves the burial of peat, which is made of partly decayed plant materials, deep underground. The heat and pressure of burial alters the texture and increases the carbon content of the peat, which transforms it into coal, a type of sedimentary rock. This process takes millions of years.
Types, or “ranks,” of coal are determined by carbon content. There are four types of coal, ordered from highest to lowest rank below.
The U.S. Department of Energy's visualization of annual energy production in each state allows you to explore how much and what type of energy each of America's states produced in 2012, from Rhode Island with 2.8 trillion Btu energy produced, to Texas with 14,201 trillion Btu. The visualization is interactive and allows users to view the breakdown of energy production by type and state.
The Virginia Department of Mines, Minerals, and Energy's interactive map shows the locations of abandoned coal mines throughout the state of Virginia. The map allows users to explore a range of mine features. These features are important because abandoned mines have many land-related problems such as landslides, stream sedimentation, hazardous structures, dangerous highwalls, subsidence, loss of water, acid mine drainage, and open mine portals.