What are the differences between open pit mining, underground mining, and strip mining?
Strip mining and subsurface mining
Strip mining (or surface mining) is performed when surface soil and rock are stripped off to reach the mineral of concern. When such operations are done, surface water bodies (lakes, streams, etc) gets acidity. Acid mine drainage occurs when water molecules infiltrates the spoil banks. The water reacts with sulfide minerals to produce sulfuric acid. The acid then contaminates streams, impoundments, and groundwater resources.
In the USA, 40 billion metric tons of coal are accessible by surface mining methods. Nearly 90 billion metric tons of coal within 50 meters of the ground level are potentially available for strip mining.
Underground mining is done in the subsurface. Underground mining is dangerous for mine workers. In Turkey, for instance, two years ago (almost 3 years ago) one underground mining accident killed 310 workers. There are always risks of collapse, explosion and fire in such operations. Some ilnesses are seen frequently in miners (e.g. black lung disease).
Acid mine drainage from mines and waste piles can pollute many kilometers of streams and rivers. Land subsidence might ocur over mines. Coal fires in underground mines can cause illnesses and ecological damage.