Measured by an ROV with the help of a Czech-Polish dive-team, it is around 12m deeper than the cave previously considered the deepest, Pozzo del Merro in Italy.
Polish deep cave-diver Krzysztof Starnawski, who first explored Hranická Propast in 1999, has over the past two years carried out many dives at the site with his team.
In 2014 he reached what he had believed to be its maximum depth of 200m, but then found a narrow opening leading into another vertical tunnel, which he measured using a probe as exceeding 384m. The following year he returned, found that the passage had widened and managed to squeeze through and descend to 265m.
As the cave extends beyond scuba-diving limits, on 27 September this year the divers descended to 200m to prepare the route for an ROV, which was deployed by technicians from the surface to determine the exact depth.
“I’ve been to this cave many times before, and a dozen times to the depth of approximately 200m, so I felt pretty confident,” Starnawski told National Geographic, which has supported the team’s expeditions. “The goal for this particular dive was to make the ROV operation smooth, easy and most effective.
“But robots do not do the job instead of us. We, the humans, are still needed to show them where to go.”
Trees, logs and branches found at the bottom suggest that the “surprisingly large” limestone cave must have changed its shape over time to allow them to fall through.
Starnawski believes that the cave developed in an unusual way, with hot water bubbling up under great pressure to wear away the rock from the bottom up. The divers say that the CO2-saturated water makes any exposed skin itch.
Further exploration is now being planned.
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