Mountaintop removal mining (MTR) is a relatively new form of coal mining which takes the mountain off the coal. Up to 1,000 vertical feet of local relief are blasted away to get to the thin coal seams underneath. MTR requires that the targeted land be clear-cut and then blasted by heavy use of explosives. The debris created is typically scraped into the adjacent river valleys in what is called a valley fill. Most mountaintop removal in the United States occurs in West Virginia.