Last night, I watched an older movie about unions in coal country (Matewan) and a documentary that was mostly about "mountaintop removal" or "mountaintop extraction." (Even the term is contested.) It was trying to be incendiary. There was a lot of tension in the beginning and the end, but the middle kind of lost traction.
Here's a trailer for the movie Coal Country:
There's a site for the movie (careful, there's music that kicks in when you go there) - Coal Country Site.
I think one of the more interesting parts was the treatment of anti-coal activists. People who are trying to fight the coal mining companies are getting threats, mistreatment, and the kind of thing that happened to Civil Rights activists in the South in the 60's (like, for example, standing in the woods next to a person's house, in the dark, at night, and yelling evil names at them - my favorite was "tree hugger" - as if trees don't deserve a good hug now and then).
The most significant problems with mountaintop mining, according to my "reading" of the film, are air and water pollution. These huge explosions spread coal dust for miles, and it is affecting people's breathing and overall health. Worse, perhaps, is the runoff from rain on exposed coal seams. Toxic chemicals are entering the water supply through this process. Other, perhaps less serious consequences of this process are the long-term change to the landscape (fewer mountains and valleys, a flattened landscape where companies try to re-grow the "overburden") and the subsequent carbon emissions from all of this coal being burned and used to make electricity. Landscaping is a significant concern, but it doesn't have the same "bite" as people being poisoned. Carbon emissions are also significant, but that's a much larger and more complex problem.
The other concern is the fact that mountaintop mining is a response to the dangerous conditions involved in older mining operations that involved underground mining. Mountaintop mining is much safer for the workers (assuming they know how to handle the explosives).