Below the densely forested slopes of the Appalachian Mountains in southern West Virginia is a layer cake of thin coal seams. To uncover this coal profitably, mining companies engineer large—sometimes very large—surface mines. This time-series of images of a surface mine in Boone County, West Virginia, illustrates why this controversial mining method is also called “mountaintop removal.”

Based on data from Landsat 5, 7, and 8, these natural-color images document the growth of the Hobet mine as it moves from ridge to ridge between 1984 to 2015. The natural landscape of the area is dark green forested mountains, creased by streams and indented by hollows. The active mining areas appear off-white, while areas being reclaimed with vegetation appear light green. A pipeline roughly bisects the images from north to south. The town of Madison, lower right, lies along the banks of the Coal River.

In 1984, the mining operation is limited to a relatively small area west of the Coal River. The mine first expands along mountaintops to the southwest, tracing an oak-leaf-shaped outline around the hollows of Big Horse Creek and continuing in an unbroken line across the ridges to the southwest. Between 1991 and 1992, the mine moves north, and the impact of one of the most controversial aspects of mountaintop mining—rock and earth dams called valley fills—becomes evident.

The law requires coal operators to try to restore the land to its approximate original shape, but the rock debris generally can’t be securely piled as high or graded as steeply as the original mountaintop. There is always too much rock left over, and coal companies dispose of it by building valley fills in hollows, gullies, and streams. Between 1991 and 1992, this leveling and filling in of the topography becomes noticeable as the mine expands northward across a stream valley called Stanley Fork (image center).

The most dramatic valley fill that appears in the series, however, is what appears to be the near-complete filling of Connelly Branch from its source to its mouth at the Mud River between 1996 and 2000. Since 2004, the mine has expanded from the Connelly Branch area to the mountaintops north of the Mud River. Significant changes are apparent to the ridges and valleys feeding into Berry Branch by 2009. The images from 2013 and 2015 show some green-up of restored lands. The images also show expanded operations in the southwest and northeast. Over the 31-year period, the disturbed area grew to more than 10,000 acres (15.6 square miles).

According to a report from the U.S. Fish and Wildlife Service, nearly 40 percent of the year-round and seasonal streams in the Mud River watershed upstream of and including Connelly Branch had been filled or approved for filling through 1998. In 2009, the EPA intervened in the approval of a permit to further expand the Hobet mine into the Berry Branch area, and worked with mine operators to minimize the disturbance and to reduce the number and size of valley fills. In 2010, the EPA reported that Hobet 45 mine met the requirements of the Clean Water Act.