How are surface mining and underground mining different?

Surface mining and underground mining are the two primary methods for extracting coal, with the choice between them dictated by technological, economic, and social factors.1

Surface Mining

Surface mining is used when coal seams are relatively close to the surface. The process involves removing the overlying soil and rock (strata) to expose the coal. Key operations include:12
* Clearing vegetation and removing topsoil.2
* Drilling and blasting the hard strata.2
* Loading and transporting the exposed coal.2
* Reclaiming the land after mining is complete.2

Underground Mining

Underground mining is employed when coal seams are located at depths where removing the overlying waste material becomes economically prohibitive. In this method, the working environment is enclosed by the geologic medium. Access is gained through openings from the surface, followed by "mine development"—the creation of a network of roadways to facilitate ventilation, power, and transport.134

While surface mining often involves moving large amounts of waste, underground mining is generally more expensive per ton due to limited access, smaller equipment, and the need for complex rock mechanics to manage pressure at depth.3