Overview[ edit ] The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. You may improve this article , discuss the issue on the talk page , or create a new article , as appropriate. The MTR process involves the removal of coal seams by first fully removing the overburden lying atop them, exposing the seams from above. This method differs from more traditional underground mining , where typically a narrow shaft is dug which allows miners to collect seams using various underground methods, while leaving the vast majority of the overburden undisturbed. Mountaintop removal has been practiced since the s. Its prevalence expanded further in the s to retrieve relatively low-sulfur coal , a cleaner-burning form, which became desirable as a result of amendments to the U.