The Appalachian Mountains are not quite so mountainous as they used to be, according to a new study by Duke University researchers, who found that mining practices in the region have flattened some peaks by as much as 40 percent.

The principal mining technique practiced in Appalachia is mountaintop removal, which is as destructive as it sounds. It involves lopping off the top of a mountain using explosives and land removal to get at the underlying seams of coal. Of course, once the summit has been removed, there's no putting it back. And most of the excess gravel, rock and soil is typically dumped into neighboring valleys, which transforms the landscape both high and low.

“There hasn’t been a large-scale assessment of just the simple full topographic impact of mountaintop mining, which occupies more than 10 percent of the land in the region we studied,” said Matthew Ross, an ecology PhD student and lead author on the study.

“[We found] the impact is deep and extensive. It is locally large and more wide-ranging than other forms of mining.”

The ruinous practice is the chief reason that the region has occasionally been listed as one of the most toxic places to live. When all of that earth is dumped into valleys, which is also where streams and rivers runoff from the mountains, pollutants are carried into the water table, poisoning local ecosystems.

“The depth of these impacts is changing the way the geology, water and vegetation interact in fundamental ways that are likely to persist far longer than other forms of land use,” said Emily Bernhardt, co-author on the study.

A Web-based app is available that allows users to toggle between pre- and post-mining topographic maps in the region. The differences are staggering.

Worse of all, there's no easy fix to the problem. Mountains can be leveled within a few years, but they take epochs to form. The damaging effects of mountaintop removal could last for generations, even if the practice was halted immediately.

“We have data that the water quality impacts can last at least 30 years, but the geomorphology impacts might last thousands of years,” said Ross. “Once you have these flat plateaus, it sets up a whole new erosion machine and a whole new way that the landscape will be shaped into the future.”