Three decades of pumping freshwater into a salt layer about 400 feet below the surface, and then its extraction to help with oil well drilling, have already caused two sinkholes to open up last year.
State officials now say the ground around the city is heaving in some areas while other parts are sinking.
"It would be a mess. It would be like a bomb going off in the middle of town," Jim Griswold, a hydrologist with the New Mexico Oil Conservation Division, told the Associated Press.
The city of about 26,000 residents has declared an emergency and says government-installed sensors should give several hours of warning before any cave-in occurs.
That should be enough time to evacuate the population, but such a collapse could potentially damage the Carlsbad Irrigation Canal. It provides water to crops south of the brine well.
If the canal goes, then these crops could not be irrigated, potentially causing $100 million in damage.
Carlsbad residents are no strangers to caverns, being home to Carlsbad Caverns National Park. But those world renowned caves were carved out by natural processes, not human activity.
Photo: National Cave And Karst Research Institute