Complex sentence: The film focuses on the impacts of mountaintop mining in the Appalachians, where mountain ridges are scraped away by heavy machinery to access coal seams below, a process which cheaper and faster than traditional mining methods, but is damaging to the environment.
Split into simpler sentences: The film focuses on the impacts of mountaintop mining in the Appalachians, where mountain ridges are scraped away by heavy machinery to access coal seams below. This process is cheaper and faster than traditional mining methods, but is damaging to the environment.