The border gap


August 14, 2022

Hranická propast is a chasm in the Hranické karst, located on the right bank of the Bečva river in the national nature reserve Hůrka u Hranice on the cadastre of the town of Hranice in the Přerov district in the Olomouc region. The depth of the dry part of the abyss is 69.5 m. The maximum measured depth of the flooded part is 450 m without reaching the bottom. The Hranická Propast is thus the deepest flooded freshwater cave in the world. According to findings from 2020, the depth of the flooded part can reach up to 1 km.


It is located near the publicly accessible Zbrašovské aragonite caves. The total depth of the chasm (at least 519.5 m as of August 2022) is not known, as its lower part is flooded by Lake Hranicky. The chasm has an elliptical shape and is situated in a SE-NW direction. Its length at its longest point is approximately 110 meters and its width at its widest point is about 50 meters. For most visitors, the most interesting data is the depth of the chasm, including the submerged part, but in reality it is a rather fragmented karst system. Karst phenomena (e.g. sinkholes) can also be observed in the immediate vicinity of the abyss. At a depth of 48 meters below the surface of the lake, after crossing the Zubatice siphon, you can climb up to the dry caves (Rotunda dry, Nebe I-III, Monika). These are continuously monitored, including water and air temperature measurements. The dry Rotunda is also known as a nesting ground for bats, which enter it through a very narrow passage from the Jezírka area. At the same time, they have to overcome about 7 meters of rock massif. The occurrence of bats is monitored and examined by experts from the Biological Institute of the Academy of Sciences of the Czech Republic.


The depth of the dry part of the abyss is 69.5 m. At the bottom is the Lake. Below the surface, the abyss was mapped to a depth of -170 m (Pavel Říha, 2005), followed by a dive to a depth of -181 m (Starnawski, 2000) and a dive on June 21, 2012 to a depth of -217 m (Starnawski with a six-member team of Czech and Polish divers ). An examination was also carried out using the Hyball robot and the HBZS Ostrava robot. The robot (R.O.V.) Hyball was at a depth of -205 m (1995). The bottom was not reached because, according to further research, such a configuration of the terrain was found, which made further progress of the robot impossible. The measurement of the depth of the chasm was carried out on October 1, 2012, when Krzysztof Starnawski lowered a probe from a depth of 217 meters to a depth of 373 meters during an event of cave divers from the organization ZO ČSS 7-02 Hranický karst Olomouc. He himself then briefly descended to a depth of 225 meters, which is the greatest depth reached by a diver in this location. On October 12, 2014, Krzysztof Starnawski once again measured the new maximum depth of the flooded part of the Hranická Abyss – 384 meters. On 27 September 2016, an ROV manufactured by GRALmarine reached a depth of 404 meters without reaching the bottom. The depth of the border chasm thus surpassed the Italian Pozzo del Merro, which until then had been recorded as the deepest flooded chasm in the world with a maximum measured depth of 392 meters. The total confirmed depth of the dry and wet parts was 519.5 meters (69.5 + 450) by 2022. . According to estimates, the chasm could reach a depth of between 800 and 1200 m, which is indicated by the temperature and chemical composition of the water in the Lake. This is also confirmed by other research published in 2020 in the professional press. From a historical point of view, it is interesting that Jiří Pogoda states that on April 13, 1980, during a solo dive, he launched a probe of a special design (glider) from Zubatica to a total water depth of 260 meters without would bottom out. However, his measurement data is incomplete and is considered to have little credibility as it has not been further verified. From the point of view of today's knowledge, Pogod's measurement is in line with reality, but due to the obscurity of the restriction at a depth of 205 meters, it would have to be a huge coincidence for his probe to be able to sink lower and, above all, to reach it�