In 2008, a 20-foot hole opened in Daisetta, Texas; by the next day, it was a 900-foot, 260-foot-deep, water-filled crater that swallowed cars and oil tanks

Located in Liberty County, Texas, about sixty miles northeast of Houston, Daisetta is a sleepy town with about a thousand residents. It has mostly been recognised, if at all, for perched above the Hull salt dome, a massive subterranean rock salt pillar that has attracted brine and oil drillers to the region since the early 1900s. The town's obscurity came to an abrupt end in the spring of 2008 when the ground beneath it collapsed, transforming a small pit into one of the biggest sinkholes ever discovered in the US. In just one day, what started out as a hole that was only twenty feet across grew into a churning crater that was hundreds of feet wide and deep enough to swallow telephone poles, cars, oil tanks and other equipment.A town built on a salt domeSalt domes like the one underneath Daisetta are formed when layers of heavy salt beneath progressively rise up over millions of years because they are lighter than surrounding rock. These domes are often near to the surface and trap pockets of oil and gas, which is why Liberty County has had drilling activities for decades. Sinkholes associated with salt domes can form when cavities develop within the cap rock or salt, and human activity can exacerbate or induce the process. For years the land above may look perfectly secure while the ground beneath is being silently hollowed away. According to the USGS, the ultimate Daisetta collapse was a textbook case of this process, with fluid poured into the dome. That slow underground erosion set the stage for what happened on the morning of 7 May 2008.The earth cracks openOn that Wednesday morning, residents saw a little sinkhole spring up along Farm to Market Road 770 on the edge of town. At first it seemed inconspicuous, little bigger than a swimming pool, and few people paid it much attention. But within hours the hole was expanding at an alarming rate and by the next day was a crater some 900 feet big and 260 feet deep. Local residents watched as the ground crumbled and swallowed up oil storage tanks, barrels, tyres, power poles and several vehicles. Witnesses said the sound was like a freight train going by. Emergency officials halted the nearby stretch of highway, evacuated buildings around the location and eventually had to alert curious sightseers who wanted a closer look at the widening pit. Around two days after the collapse, researchers from the University of Texas at Dallas quickly deployed a mobile laser scanning team to the site in the hope of capturing the changing shape of the crater before it stabilised.What led to its downfallThe Houston Geological Society placed the collapse on the northwest flank of the Hull salt dome, within a dense band of active and abandoned petroleum wells. Its 2008 bulletin noted at least four earlier sinkholes in the same band and said their occurrence, like that of the Daisetta collapse, might be related to oilfield operations that had begun in the early 1920s. The investigation highlighted that at least four other sinkholes had already occurred in the same region of active and abandoned wells, suggesting the 2008 occurrence was less a freak accident than the latest chapter in a trend related to decades of drilling. The Daisetta sinkhole is one of the largest ever documented along the salt domes of the Gulf Coast, averaging a diameter of around 620 feet. Fortunately no-one was killed or badly harmed, mostly because the fall was slow enough for bystanders to move away from the edges.A crater that remained part of DaisettaMore than a decade later, parts of the ground around the original crater crumbled again, a reminder that a salt dome filled with old wells rarely stops moving in one go and that a community founded on one has to live with that uncertainty forever. Today, the crater is partially filled with water and has become an unlikely local monument, visible from the highway, a lasting feature that still draws occasional curious visitors even as Daisetta has largely returned to normal. It is still a useful example for geologists to analyse how activities in an oilfield can speed up a natural process that might otherwise have taken centuries to reach the surface.Catch the latest World News and Live updates. Download the TOI app.