In the centuries since early man learned the pieces of black rock he picked up on the ground would produce heat when burned, we have had to look for coal beyond the places where we could find it on the ground. One of the areas it was easiest to find was where it appeared as one of many layers of materials along the side of a hill. Some mining sites today in the United States may be close to 500 feet underground.
Mining is classified by the method needed to reach the coal seam.
When the coal is found close to the Earth's crust and taking away the overlying layers of material is not too expensive, surface mining is used to remove the top layers of materials and expose the coal. If coal is found in layers far from the surface, underground mining is the preferred technique. Common types of underground mining are the drift, shaft, and slope mining methods. The crushed coal can then be sent by truck, ship, railroad, or barge. You may be surprised to know that coal can also be shipped by pipeline.