The enormous underwater sinkhole known as the Great Blue Hole can be found near the center of Lighthouse Reef, a small atoll located 43 miles away from the mainland and Belize City. Stretching out in a circular shape, it measures 1,043 feet across and is 407 feet deep. The formation of this natural wonder occurred during multiple instances of glacial activity in the Quaternary period, which caused sea levels to drop significantly.
For many years, scuba divers and snorkelers have explored the Great Blue Hole’s surface waters. However, only a few adventurers have dared to venture deeper and discover what lies at the bottom of this natural wonder. Back in 1971, Jacques Cousteau attempted to map the hole’s entirety using his ship, the Calypso. He confirmed that it was a typical karst limestone formation formed before sea levels rose.
In 2018, a team from Aquatica Submarines made their way to the Great Blue Hole’s depths to try and map its interior, revealing some surprising findings.
Upon starting their descent, the crew encountered typical sea creatures such as reef sharks, turtles, and giant corals. However, at a depth of 90 meters, life began to disappear due to a thick layer of toxic hydrogen sulfide floating like a blanket across the entire sinkhole. Below that layer, there was no oxygen or life, only a graveyard of shells and hermit crabs that had fallen into the hole and suffocated. Surprisingly, as the crew ventured further towards the bottom of the hole at around 120 meters, they discovered small stalactites, providing scientists with clues to the hole’s ancient history.
The formation of stalactites is due to water dripping down stone, leading scientists to believe that the Great Blue Hole was once a dry cave inhabited by various creatures during a prolific era on Earth. It is thought that the cave formed during the last Ice Age, which ended about 14,000 years ago when rising sea levels caused it to flood and collapse, leaving behind the stunning Blue Hole we see today. Other marine sinkholes like Dragon Hole in the South China Sea and Dean’s Blue Hole in the Bahamas likely formed in a similar manner.
During an exploration of the bottom of the hole, scientists discovered a 2-liter Coke bottle and a lost GoPro containing vacation photos. They also came across two of the three people who were lost in the Blue Hole but chose not to attempt a recovery as it is a peaceful and dark resting place.
Although the Great Blue Hole won’t be around forever, currently we can still appreciate its beauty and study its many mysteries as sand continues to fall into it, slowly filling it up like an underwater hourglass.
