Dispatches from the bottom of Belize's Blue Hole
Francesca Street, CNN

- A team of scientists -- including Virgin billionaire Richard Branson -- has returned from a groundbreaking mission to the bottom of Belize's Great Blue Hole with exciting findings.
The Great Blue Hole is the world's largest sinkhole, measuring an incredible 300 meters (984 feet) across and roughly 125 meters (410 feet) deep.
The team also included Fabien Cousteau, grandson of underwater explorer Jacques Cousteau -- who put the Blue Hole on the map back in 1971. The group embarked on their odyssey in December 2018, determined to discover the secrets at the bottom of the Blue Hole.
Using two submarines, the expedition captured new images and footage inside the Blue Hole and created the first 3D map of its interior.
"We did our complete 360 sonar map and that map is now almost complete. It looks really cool, it's this mesh-layered, sonar scan of the entire thousand-foot diameter hole," Erika Bergman, chief pilot, oceanographer and operations manager, tells CNN Travel.
[Linked Image]
Bergman says one of the most exciting findings was never-before-seen stalactites -- a type of mineral formations shaped like icicles -- roughly 407 feet into the hole, very near the bottom.
"That was pretty exciting, because they haven't been mapped there before, they haven't been discovered there before," she says.
Bergman says the whole experience of being submerged in the murky depths was pretty incredible.
"One of the crazy things about the hole is the hydrogen sulfide layer," says Bergman.
The layer descends at roughly 300 feet, cutting out all the light and plunging divers into darkness.
"You lose all of that Caribbean sunlight and it just turns completely black, and it's totally anoxic down there with absolutely no life," explains Bergman.

But thanks to their high-resolution sonar, Bergman and her team were able to see the hole's intricate features.
"You can be 20 or 30 meters away from a stalactite or a hunk of the wall and see it in every perfect detail, better than eyesight could even provide," she says.
Intriguingly, not everything the team found could be identified. They found some unidentifiable tracks at the bottom of the hole -- Bergman says these remain "open to interpretation."

The team was also really pleased to see that the Blue Hole was pretty free from trash.
"There were basically two or three little pieces of plastic -- and other than that, it was really, really clear," says Bergman, spotlighting the work of the Belize Audubon Society, which helps protect the hole.
Bergman says there's very little visible human impact.
"It's neat that there are spaces on our planet -- and most of them in the oceans -- that are exactly the way they were thousands of years ago and will remain exactly the way they are thousands of years in the future."


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