The Great Blue Hole lies 100 km off the coast of Belize in Central America.
A world heritage site of the UNESCO, the Great Blue Hole is part of the Belize Barrier Reef Reserve System. It is round in shape with a distinct colour measuring 300m across and 108m in depth.
The Great Blue Hole, which was once an island, is a result of the geological factors at play. Few thousand years ago during the ice age, the sea level was much lower. Limestone rocks were found below the island, which dissolved in rain and groundwater. Over a period of time, this process formed hollow places or caves below the earth’s surface.
In due course, the roof of the cave became so thin that it crumpled creating a vast sink hole. When the ice age ended, glaciers melted and sea levels rose. As a result, the entire cave system beneath flooded.
This sinkhole, when viewed from above, has a dark blue tinge because of its depth. It can be easily distinguished in contrast to the shallow aqua blue water of its surroundings. The stalactites and stalagmites are huge and measure 9 to 12m in length.
The Great Blue Hole is deep and considered as one of the top 10 best diving spots in the world. Since the Great Blue Hole lies close to the centre of the Lighthouse Reef, sea kayaking and snorkelling to view the coral reef is an attraction. The Lighthouse ring-shaped reef houses open-water fish and parrot fish. You might also catch a glimpse of the hawksbill turtle and stingrays.
The Great Blue Hole is not the only sinkhole in the world. The Dean’s Blue Hole close to Clarence town on Long Island in Bahamas is the world’s deepest sinkhole measuring a depth of 200m.
On the coast of the Red Sea, towards the north of Dahab in Egypt is the second deepest blue hole. There have been many unsuccessful attempts by divers trying to uncover a tunnel connecting the Blue Hole of Dahab to its surrounding waters.
The Blue Hole of Gozo is only 15 metres deep and lies on the west coast of the island of Gozo in the Maltese archipelago in the Mediterranean Sea.