Chapter 25 - Ice Caves in Romania

Abstract

Romanian karst harbors more than 12,500 caves, of which only a very few fulfill the appropriate conditions for ice formation and maintenance. In the Retezat Mountains (Southern Carpathians), several high-altitude (>1900 m a.s.l.) vertical caves contain permanent snow and ice deposits that can reach up to 20 m in thickness. More remarkable are three caves in the Apuseni Mountains (northwestern Romania), where large ice bodies form by the freezing of percolating water under favorable local conditions during winter. The three caves (Scăris‚oara Ice Cave, Focul Viu Ice Cave, and Borţig Ice Cave) share common features that favored the development and long-term survival of subterranean glaciers. These caves are located at relatively low (~1200 m a.s.l.) altitudes, and they all share similar morphology, with large entrances located in their upper sections, only. This peculiar morphology leads to cold air inflow inside the cave during winter months, triggered by the higher density of the cold external air masses compared to the warmer ones inside, while in summer, the same density difference prevents the exchange of air masses between the two environments. As a direct consequence of this peculiar climate, the water that percolates during warmer seasons into the cave freezes during winter, leading to the formation of layers of ice that subsequently accumulate to build up a large deposit of perennial ice. The most remarkable example is that of Scăris‚oara Ice Cave, which hosts one of the largest deposits of cave ice in the world (~100,000 m3 of ice) and the oldest such ice reported (~10,500 years). In Scăris‚oara Ice Cave, the environment is divided into three zones on the basis of the presence and influence of ice. A glacial zone resides in the entrance area where the massive ice block is present, and where the temperature has the widest fluctuations. A periglacial climate is present in the three rooms flanking the ice block, where the temperatures are more stable and favor the formation of ice speleothems. In the deep sectors of the cave, where the temperatures are positive (~4°C), ice does not develop, leaving room for the formation of a typical cave environment with calcite speleothems of various shapes and sizes. Here, cave fauna including beetles, spiders, springtails, amphipod crustaceans, and several species of bats can be encountered. The ice caves in the Apuseni Mountains have been the subjects of scientific scrutiny for almost a century, with the various studies conducted here leading to the development of novel theories on the mechanisms behind ice formation and dynamics, cave climate, and the functioning of underground glacial ecosystems, and providing evidence of past climate and vegetation dynamics during the past 10,000 years.