Kálmán Péntek’s research while affiliated with Eötvös Loránd University and other places

This study deals with the karren formation of bare surfaces. The used methods are theoretical calculations, field mapping, laboratory experiments, and digital modelling. The denudation rate of karren surfaces on bare slopes and based on the data of measurements, the denudation rate of karren in different vegetation belts were given. Mostly, the development of rinnenkarren and meanderkarren was analysed. A function relation was determined between the density of rinnenkarren types and the slope angle. The effect of the main channel and tributary channels on each other was studied by computer modelling. The impact of the wind on the development of karren and the conditions for the development of tropical karren was also investigated.

This study interprets the development of various flow types of the Transdanubian Mountains. For this, pressure was calculated at different depths and along some profiles the horizontal, specific temperature was calculated based on geoisotherms. This is the value of temperature distribution calculated to a given place. It has been established that upwellings develop at sites where the value of horizontal specific temperature is more than 0.8 • C, and partial upwelling can be detected where this value is between 0.6 • C and 0.8 • C. Outflow from the karst is present where this value is below 0.4 • C. Taking into consideration these values, the water temperature of karst springs and the caves of heat effect, the distribution of various flow types are determined. The flow type is also affected by the fault structure of the basin. In the case of horsts subsided to a great degree, since the sediment is thick above such horsts, the water is not able to flow upwards and towards the mountains because the hydrostatic pressure does not prevail any more. Above horsts subsided to a lower degree, the sediment is thin and thus, the water moving upwards is able to flow through.

Shaft development can be documented on the basis of comparative studies of specific shaft lengths and shaft patterns. We calculated the specific length of shafts and the average specific shaft length of the shafts in some karst areas and we investigated the relation between the altitude of shaft floors and the specific shaft length. Taking the registered specific shaft lengths and the shaft patterns into consideration, it can be stated that some parts of the shafts developed paragenetically in the studied karst areas. In the Bakony Region, this was caused by surface water influx, rise of karst water level, and their simultaneous effect. As a result, shaft systems, bifurcating shafts and storeyed shafts developed. On glaciokarst areas, shafts may constitute a system with phreatic passages: either because a phreatic environment developed in the vadose zone due to the permanent impoundment of karst water or because a phreatic passage got into the vadose zone since the karst became elevated. On the studied karst areas, the following shaft development types are distinguished: glacial-high mountain surface flood development type (1), glacial-high mountain karst water and surface flood development type (2), glacial karst water and surface flood later phreatic development type (3), shaft with a passage that got into the vadose zone (4).

The study deals with the Lena Pillars (Sakha Republic, Russia, Siberia). The Lena Pillars are pinnacle features which are characteristic on karsts. The importance of these features is that they are extremely large and occur on very large areas. Their occurrence is interesting because they do not appear on tundra karst. We investigated the veneers of cliffs, the fracture density of the building rock, the distribution and dispersion of the fracture directions, direction distribution and dispersion of the giant grikes between the pillars, the layer thickness of the building rock, the size and dispersion of debris. We distinguished pillar types, and then we classified the features on the area of the pillars from a morphogenetical point of view. According to investigations and morphological analyses, the pillars developed from palaeokarsts. During the former karstification grikes and caverns developed close to the surface. These features coalesced into each other. The giant grikes of great size became filled and the pillars were covered. After the cut of the Lena River these features were revealed and became exhumed. Now the pillars are destroyed and continue developing by frost weathering.

The width and depth of the main channels were measured along the length of seven rinnenkarren systems on the floor of the glacier valley under the Tragl peak in the Totes Gebirge, Austria. The cross-section areas of the channels were calculated which were considered in relation to the distances between their location along the flow path and the margin of the slope. It can be stated that hollowings (local maxima) occur on the main channels at the connecting sites of the tributary channels. According to laboratory experiments, turbulent zones develop on the rivulet of the main channel, where the rivulet of the tributary channel joins the rivulet of the main channel. The length and the location of the turbulent zones depend on the slope angle, the joining angle of the tributary channel, the ratio of the water flow of the rivulets of the main and tributary channels as well as the water flow of the tributary channel. The pattern of the local maxima of the main channels is explained by the turbulence pattern which develops in the rivulets of the main channels. The turbulence pattern may be continuous (the turbulence is uninterrupted) or non-continuous (the turbulence is separated into turbulent zones of different lengths and densities). The length and density of turbulent zones determine the size and density of hollowings.

We studied the evolution of dolines in ground ice environment, in a paleouvala of the Hochschwab Mts. (Northern Calcareous Alps, Austria) as well as in laboratory conditions. We measured the ground ice thickness of the exploration area by geophysical methods. We estimated the melting (thinning) speed and the pertinent parameters for ground ice samples at different temperatures in laboratory conditions. After simulating the process we were able to determine the physical conditions generating the ground ice melting phenomena, and based on this we calculated its melting speed. Due to the air circulation in the karst, the lower level of the ground ice starts to melt and the covering sediment particles fall down. Thus the thinned covering sediments will fall-in and dropout dolines will mould the ground, or the surface may sink by the progress of the melting, entailing suffosion dolines to be generated.