It began with bubbles. Bubbles of gas throughout the bayou. Nothing to get hysterical about. But it kept getting worse.
So residents of Bayou Corne, Louisiana, turned to state regulators, who in the summer of 2012 determined that it wasn't naturally occurring swamp gas, according to Mother Jones. And the U.S. Geological Survey also found that there was increased seismic activity.
What could it be? With bubbling getting worse, the suggestion was floated that it could be the beginnings of a sinkhole, perhaps caused by the mining of a salt dome beneath the town. The company in charge of the mining, Texas Brine, told state officials a sinkhole was highly unlikely.
Then, on August 3, 2012, crude oil began gushing out of a gaping pit nearby. That afternoon, governor Bobby Jindal ordered residents of the small town to evacuate.
Texas Brine drilled a relief well, only to find that the wall of the salt dome, which they were mining, had collapsed. "The breach allowed sediment to pour into the cavern, creating a seam through which oil and explosive gases were forced up to the surface," Mother Jones noted. It was previously thought that it was impossible for salt domes to collapse from the side in this manner, illustrating a lack of knowledge about the geology of these formations and the effects of mining them.
Today, the sinkhole in Bayou Corne covers 24 acres and is 750 feet deep—and keeps growing, according to news reports. Many of the town's residents have evacuated, while some have defied the order and remained. Earlier this month, the state of Louisiana sued Texas Brine LLC for environmental damages, according to the Times-Picayune.
Booms have been put in place to protect the surrounding wetlands from oil release. But much damage has already been done, and the state of Louisiana's suit alleges the company didn't and hasn't done enough to correct the problem, according to the Associated Press.
The incident is one of the unforeseen effects of a rise in "injection" mining in southern Louisiana, and throughout the South.
Bayou Corne's sinkhole was caused by this kind of mining, according to Louisiana state officials. In injection mining, water is injected into salt domes deep underneath the ground's surface. The resulting salt water is then brought up and evaporated, where it can yield products like sodium hydroxide, or lye, used in the manufacture of many products, according to Mother Jones. The empty caverns that this practice creates may also then be filled with other materials, like wastewater or even radioactive materials.
Petrochemical companies, many of which use injection mining, are amongst the biggest employers in Louisiana.
The U.S. Geological Survey notes that sinkholes are common in areas where the underlying rock is limestone, salt or carbonate rock, and circulating water is present to hollow out holes. But recent examples in the South show mining may cause these incidents. In 1954, one brine cavern in Bayou Choctaw, near Baton Rouge, collapsed, birthing a lake 820 feet wide. In 2008, another sinkhole appeared virtually overnight, reaching a width of 600 feet and a depth of 150 feet, according to the New York Times. This one, dubbed "Sinkhole de Mayo," may have been caused by the injection of saltwater wastes into empty wells within salt domes.
Perhaps the most spectacular and tragic sinkholes happened in November 1980 in Louisiana's Lake Peigneur. In that case, operators miscalculated where they were drilling, piercing a salt dome. This opened a hole into which the lake catastrophically drained, creating an otherworldly vortex that swallowed 11 barges.
Texas Brine may have also stored naturally occurring radioactive material in the well beneath the sinkhole, and state officials are investigating to see if they were illegally placed there. So far there hasn't been evidence that radioactive materials have reached the surface.
Sinkholes are also a major problem in Florida, where they are becoming increasingly common. According to NBC News, some researchers think that this is due in part to more water being removed from the ground for agriculture and other reasons, which changes the underlying geology and makes sinkholes more likely to form.