The West Texas desert is home to two infamously large sinkholes. One, near the town of Wink — about 230 miles east of El Paso — opened up in 1980 near an abandoned oil well. The next, a mile away, appeared in 2002. These giant, empty pits are now part of the weird desert landscape, but scientists report Thursday in Scientific Reports that they’re not likely to be the last ones to pockmark the West Texan terrain.

The scientists from Southern Methodist University show in their new study that a large region close to the existing sinkhole — an area covering 4,000 square miles — is sinking and uplifting at an abnormal rate. This denotes an instability that the researchers say could lead to more sinkholes in the future.

“The ground movement we’re seeing is not normal. The ground doesn’t typically do this without some cause,” said geophysicist Zhong Lu, Ph.D., a professor in the Roy M. Huffington Department of Earth Sciences at SMU in a statement published Thursday.

The large sinkhole by Wink, Texas, as seen from Google Earth. Google Earth

That cause, the authors of the paper write, is likely the preponderance of oil wells and injection wells in the area. West Texas is oil country, and to harvest that oil, wells have been drilled deep into the ground for nearly 70 years. Turns out that doing so isn’t great for the stability of the region, especially considering that its geology isn’t the strongest: It’s mostly underlaid by water-soluble salt and limestone, as well as shale, a soft rock.

“We’re fairly certain that when we look further, and we are, that we’ll find there’s ground movement even beyond that,” said study co-author and research scientist Jin-Woo Kim, Ph.D., a research scientist in the SMU Department of Earth Sciences, in a statement. “This region of Texas has been punctured like a pin cushion with oil wells and injection wells since the 1940s and our findings associate that activity with ground movement.”

Another sinkhole, about a mile away from the Wink sinkhole. Google Earth

In previous studies, the SMU team had shown that the two Wink sinkholes were expanding and even had the potential to collapse into one another. In the new study, they show that the surrounding areas are just as vulnerable to the sudden appearance of gaping holes, using their analysis of radar images snapped of the region by European Space Agency satellites between November 2014 and April 2017.

Combined with data from oil well production data from the Texas Railroad Commission, the images suggest that oil production — especially pressurized fluid injection deep into the Earth — is to blame for the increasingly unstable ground. Pressurized fluid injection is the process of forcing high-pressure fluid into a well to help push oil out of it.

The land surrounding West Texas's sinkholes is shifting at an alarming rate, say scientists. Zhong Lu and Jin-Woo Kim, SMU

The 4,000-square-mile area they observed comprises four counties that include the towns of Pecos, Monahans, Fort Stockton, Imperial, Wink, and Kermit. This region is known for processing hydrocarbons from the West Texas Permian Basin, a 300-mile expanse known to be particularly oil-rich.

In 2017, a study by IHS Markit showed that the Permian Basin could contain between 60 and 70 billion barrels of recoverable oil estimated to be worth some $3.3 trillion. As U.S. oil exports are currently surging, it doesn’t seem likely that this vulnerable area — and other similarly oil-rich regions of the country — will experience a respite from drilling anytime soon.

This image from the study shows the amount of vertical movement present in the unstable region. Zhong Lu and Jin-Woo Kim, SMU

The researchers will have to keep an eye on the “subsidences” — small cavities that can be thought of as pre-sinkholes — that they found in this region during their study. Now, there’s a subsidence bowl a half-mile east of the second, a smaller Wink sinkhole, and others are growing near Imperial and Pecos. They’ll also have to watch out for areas that appear to be “uplifted” — raised by several inches — as a result of pressurized fluid injection, as these are just as unstable.

Then, there’s the problem of seismic activity occurring in the region near Pecos at an unnatural rate. “Before 2012, earthquakes had not been recorded there,” said Kim. “At the same time, our results clearly indicate that ground deformation near Pecos is occurring.”

For now, all the team can do is use their new radar analysis techniques to monitor what’s happening in this region. There’s no promise that doing so will slow down the human activities that continue to punch holes in the landscape, but at the very least, they can make sure a minimum number of humans are there if those holes cave in.