The Hranice Abyss in the Czech Republic is known as the deepest freshwater cave on the planet. Recently, researchers announced that they have identified a new depth for this cave.
In 2016, a team led by renowned Polish cave diver Krzysztof Starnawski ventured to explore the cave in the Czech Republic and concluded that it was at least 404 meters deep. However, this estimate was based on the diving equipment that allowed them to reach a certain depth. The true depth of the Hranice Abyss remains a mystery.
So far, the exact depth of the freshwater cave Hranice Abyss has not been accurately determined.
Recently, researchers conducted several geophysical tests above the Hranice Abyss and estimated that this cave system is actually at least 1 kilometer deep. However, there are still opinions suggesting that the underwater cave could be even deeper.
Located in the Přerov district of the Czech Republic, the underwater cave Hranice Abyss is not merely a water-filled hole but rather a complex system of tunnels resembling a cave that extends through the Earth.
Underwater cave tunnels are often carved through rock dissolved by slightly acidic rainwater and melting snow, gradually eroding the surrounding limestone. Previously, it was believed that the Hranice Abyss might have formed from the bottom up.
National Geographic reported in 2015 that the Hranice Abyss may have been formed by acidic groundwater that was heated from below the Earth’s surface by the Earth’s crust and seeped up like a volcano, dissolving limestone from underneath.
Although this is an intriguing theory, the new survey found evidence of structures formed by top-down processes that seem more convincing.
Experts have been trying to understand the scale of Hranice Abyss for centuries. There are historical reports that someone attempted to measure the depth of the cave in 1580 by holding their breath and diving as deep as possible. Naturally, that effort was unsuccessful, but advancements in technology have allowed divers and scientists to go deeper over the past century.
However, exploring the Hranice Abyss is very challenging. Divers have entered the cave but faced numerous difficulties due to extremely poor visibility and the highly acidic water within the cave. The air above the water surface is also unbreathable due to high carbon levels. Many logs, leaves, and trees have fallen into the cave over the years, blocking paths in various areas.
The shape of the Hranice Abyss also makes ensuring safety for divers a significant challenge. If a diver loses control of their buoyancy, they could sink deeper into the cave. “We focused on exploring at a depth of 200 meters. Everything was going well, so we decided to surpass that limit. The space we are exploring and mapping is vast. At a depth of 450 meters, we had to stop because of the technical limitations of our underwater robot,” shared Michal Guba, president of the Czech Speleological Society.
Previous studies indicated that the Hranice Abyss formed due to groundwater seeping down rather than up, a process known as subterranean formation. However, Guba and his colleagues believe that this cave was created by underground water flow causing erosion.
