Into the Great Blue Hole

Recently, a team of scientists returned from a journey to the bottom of Belize’s Great Blue Hole after having gone down in submarines back in December 2018. This Great Blue Hole is the world’s biggest sinkhole, measuring 300 meters across and 125 meters deep (1000 and 410 feet, respectively).

The team of scientists used two submarines to capture new images and footage from inside the Blue Hole. The team was also able to use sonar imaging to create a 360 degree map of the entire hole, according to chief pilot, oceanographer, and operations manager Erika Bergman.

Bergman also said that one of the most exciting finds of the trip were the never-before-seen stalactites near the bottom of the Hole. Stalactites are mineral formations that hang from the ceilings of caves and hot springs.

“That was pretty exciting,” Bergman said. “Because they haven’t been mapped there before, they haven’t been discovered there before.” These scientists have discovered pieces of the Earth that have never before been seen by a human.

Bergman also said one of the craziest things about being down there was the hydrogen sulfide layer, which descends at roughly 300 feet deep and cuts out all light.

“You lose all of that Caribbean sunlight and it just turns completely black,” Bergman added. “And it’s totally anoxic down there with absolutely no life.”

This layer of hydrogen sulfide occurs as a by-product of the breakdown of plants and animals in the ocean by bacteria. The reason it only occurs as far down as it does and not closer to the surface is because the oxygen from the atmosphere mixes in the surface of the water and controls the diffusion of hydrogen sulfide in these areas. Layers of hydrogen sulfide can be found in oceans all over the world.

The amount of hydrogen sulfide in the water of the Blue Hole make it impossible to see anything, and impossible for anything to survive. If a human were to breathe in this concentration of hydrogen sulfide, they would die instantly. But, fortunately, these scientists were in submarines that kept them safe. Also, their high resolution sonar technology allowed them to see every detail of the hole through the pitch darkness.

“You can be 20 or 30 meters from a stalactite or a hunk of the wall and see it in every perfect detail, better than eyesight could even provide,” Bergman said.

Interestingly, the team could see tracks on the bottom of the hole that could not be identified. The tracks remain, “open to interpretation,” according to Bergman.

The team was also pleasantly surprised to find relatively few signs of human impact, reporting only two or three little pieces of plastic.

The expedition was broadcast live on Discovery Channel on Dec. 2, 2018. After the dive in December, vessels monitored the bottom of the hole for two weeks in order to collect enough data to make the sonar maps.

The team made sure not to leave any equipment behind to leave their impact as small as possible.

“We take only pictures, leave only footprints,” Bergman said. The hope is to keep the oceans as undisturbed by humans as possible.