A recent expedition plunged into the Great Blue Hole, the singularly charming marine chasm within the Belize Lighthouse Reef, and brought back a collection of stunning photographs detailing this geological strangeness.
Between November 27 and December 13, 2018, an expedition team conducted more than 20 dives in the Blue Hole using the Aquatica Stingray submarine and Roatan Institute of Exploration Deepsea (R.I.D.E.) Idabel submarine. The crew includes none other than Richard Branson, rich in human beings and founder of the Virgin group, and Fabien Cousteau, grandson of the famous underwater explorer Jacques Cousteau who drew attention to the Blue Hole at early 1970s, as well as many scientists and underwater experts.
In addition to impressive holiday photography, their work has also produced a 3D Blue Hole sonar chart and collected environmental data on its water. Once processed, all this information will be shared with the Government of Belize and the global scientific community to help preserve the Great Blue Hole and its biodiversity.
With over 300 meters wide and 125 meters deep, the Great Blue Hole is the second largest sump in the world, after Dragon hole in the South China Sea. It is found in the reserve system of the Belize Barrier Reef, a World Heritage of UNESCO. Charles Darwin described this reef as "the most remarkable reef in the West Indies". And for good reason too: the region is home to a number of unique reef types and is one of the purest reef ecosystems in the Western Hemisphere. It is also rich in biodiversity, frequented regularly by many marine creatures, including hammerhead sharks and reef sharks.
"Over the last 14,000 years, the polar ice caps, formed during the last glacial maximum, have thawed and elevated sea levels in stages." Aquatica's operations director, writes in a blog post.
"The Great Blue Hole, aptly named, is a collapsed cave, filled with stalactite caves and made up of layers of fine limestone walls and rougher calcium carbonate," she added. "Preserved by temporal disturbances and isolated in the darkness, the hole contains clues to a very natural part of the life cycle of our planet – it is these terraces and stalactites that we have begun to map."
One of the most interesting features of Great Blue Hole is its hydrogen sulphide layer. At a depth of about 90 meters (~ 300 feet), a sulphurous hydrogen mantle sits in the hole. This product is toxic, corrosive and it really stinks. When you sink a little deeper, the water also becomes devoid of oxygen (anoxic). The result is a cemetery of molluscs and crustaceans about 106 meters (thousands of feet) where thousands of unsuspecting creatures dared to swim too deeply and perished.