The Great Blue Hole

Travel to Central America with me today to one of the more striking spots on our rocky orb: The Great Blue Hole of Belize.

We don’t often associate sinkholes with the ocean, but TGBH is a spectacular version of a phenomenon called, fittingly, blue holes. They are marine caverns or sinkholes, which have openings at or near water surfaces. On land, most sinkholes form in limestone via karst processes – a chemical dissolution of soluble rock. If conditions are right, karst processes form caves.

If you’re wondering how this giant void formed in the ocean, good on you. The feature was born thanks to glaciation, as long as 150,000 years ago, on land when sea levels were much lower. Eventually worldwide levels rose and the above-ground cave became a below-ocean wonder.

In 1971 the inimitable Jacques Cousteau brought his famous craft, the Calypso, to probe the depths of the hole. The expedition confirmed the hole’s origin story and witnessed stalactites from submerged portions. The popularity of the site soared after Cousteau’s visit and it is now a scuba-diving Mecca.

The contrast between the blues of the water arises due to the differences in depth. Since the hole is nearly vertical, the depth increases dramatically and suddenly, causing a deep midnight shade, which is surrounded my aquamarine shallows. Near the surface and around the hole, divers encounter typical reef flora and fauna, making this spot a true “bucket” list destination.

In late 2018 a scientific team used a submersible to explore and map the depths of the hole. They were armed with sonar and high-tech cameras. Check out the video below for footage of the expedition, a look at some of the giant stalactites, and a three-dimensional model of the entire hole!