EXPLORING BLUE HOLES
The remains of crocodiles, bats and even humans have been found in these openings in the ocean floor
WORDS RICHARD EDWARDS
There’s no rule that says the great wonders of the natural world have
to be on dry land. Described by legendary underwater explorer
Jacques Cousteau as one of the ten best diving sites on the planet, the Great Blue Hole, situated off the coast of Belize in Central America, is believed to be the world’s largest submarine sinkhole. Some 300 metres wide and 125 metres deep, the UNESCO World Heritage Site is a near-perfect circular formation where the seafloor drops sharply away from the surrounding shallows of the Lighthouse Reef atoll.
The warm waters are a beautiful, clear blue. But it wasn’t just the scenery that got Cousteau excited when he took his ship, the Calypso, there in 1971. The Great Blue Hole is also a paradise for geologists, who can marvel at its unusual rock formations and intriguing history. This hole in the ground was formed in drier times. In past ice ages, the sea level was 100 to 120 metres lower than it is now, and so the area around the Great Blue Hole would have been dry land. Cave systems formed in the limestone, and when the ceiling of one cave collapsed as a result of water erosion, a sinkhole formed. It was submerged when the ice melted and the sea rose to its current level.