The world’s largest blue hole is deeper than previously thought and houses tunnels

Discovered in Mexico in 2021, the world’s deepest blue hole is deeper and more connected to the ocean than previously measured — and could be even bigger

Three years ago, scientists discovered the world’s largest blue hole — called Taam Ja’, in Chetumal Bay, Mexico — but they continue to discover that the underground cave is even larger than previously measured. Also called marine sinkholes, blue holes appear when the seabed is made of soluble material, such as marble, limestone or gypsum.

A new investigation at Taam Ja’ has found that the structure extends to a depth of 420 meters, 146 m deeper than the initial measurement and 119 m deeper than the previous record holder, Sansha Yongle’s Blue Hole. Located in the China Sea, it is “only” 301 meters deep.

Assessing Mexico’s blue hole

In 2023, a submarine expedition sought to identify the environmental conditions of Taam Ja’, whose data were published last Monday (29) in the scientific journal Frontiers in Marine Science. A conductivity, temperature and depth profiler was used — the equipment comes with a series of probes that evaluate and transmit properties of local waters.

Several different aquatic layers were revealed, such as one that is 400 m and has a temperature and salinity similar to that of the Caribbean Sea and the coral lagoons on the coast. This, according to the researchers, indicates that the blue hole may be connected to the ocean by a network of tunnels and caves that are still unknown.

Initially, Taam Ja’ was measured using an echo sounder, a device that sends sound waves to the bottom of the water and measures the speed at which they return to calculate the distance. There are limitations to the procedure, however, as the density of water in blue holes can vary and each of them can have unexpected shapes, not being completely vertical.

With the depth profiler, the measurement was more accurate, but it still failed to reach the bottom of the underwater structure. The equipment has a range of 500 meters, but the cable moved due to water currents or collided with a rock, as it ended up stopping at 420 meters, according to the scientists. For future research at the site, the plan is to reach the bottom and explore Taam Ja”s network of caves and tunnels — perhaps even its biodiversity.

Source: Frontiers in Marine Science

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