Tamás Telbisz

Preferred Clast Orientation in Volcaniclastic Mass-Flow Deposits: Application of a New Photo-Statistical Method

A photo-statistical method has been developed to quantify the strength of directional clast fabric in various types of volcaniclastic mass-flow deposits. Fabric strength (R) is defined as the resultant vec- tor length of clast alignment computed from clast angles visible on a vertical outcrop face. R can be obtained from photographs of an ex- posure via image analysis and statistical assessment with regard to clast number and direction of exposure face vs. paleoflow. Relative to tra- ditional, manual field measurements, the photo-statistical method gives reproducible quantitative results that are independent of subjective clast selection. On average, one hundred and fifty clasts are the mini- mum number necessary to obtain reliable R values. For determining the strength of directional fabric, it is more accurate to measure ran- domly collected clasts than only the most elongated ones (normally the practice during manual measurements), because more elongated clasts display a stronger fabric. Clast size generally does not influence clast alignment. R values obtained from lower or upper portions of vertical exposure faces may show significant differences if pronounced imbri- cation is developed in the lower part of the beds passing upward to purely bed-parallel clast alignment. Bimodality caused by the coexis- tence of imbricated and bed-parallel clasts tends to reduce R values. The studied examples include (1) near-vent breccias, (2) block-and- ash flow deposits, and (3) mostly cohesive volcaniclastic debris-flow deposits from 49 selected exposures (24 in Hungary, 6 in France, 4 in Japan, 3 in New Zealand, 2 in Indonesia, and 1 in the U.S.A., Argen- tina, Chile, Turkey, and Romania, each). Near-vent breccias show a relatively weak fabric (R

The impact of topography on social factors, a case study of Montenegro

Relationships between environmental and social factors have long been studied by geographers. Nowadays, GIS-aided statistical analysis provides new tools to explore these relationships. In order to detect the impact of topography on social factors, we selected the country of Montenegro as a case example due to its high topographic variability. We compared the spatial pattern of population, settlements and ethnic minorities to physical geographic factors, especially to topography, but lithology and land cover data were also taken into consideration. We found that certain factors are closely correlated, e.g. the settlement density linearly decreases with elevation, while the characteristic settlement area shows an exponential increase upwards. The population density is not related to absolute elevation, but it is in close correlation with height (i.e. elevation relative to the local minimum). Population change and illiteracy are also topography-related social factors. On the contrary, the variable ethnic pattern of Montenegro is influenced by historical, political and economic effects rather than by environmental factors or topographic features. As a conclusion we state that in the scale of a country or a region, the environment can strongly impact some social factors.

Heterogeneous forest classification by creating mixed vegetation classes using EO-1 Hyperion

ABSTRACT Hyperspectral satellite data is an efficient tool in vegetation mapping; however, previous studies indicate that classifying heterogeneous forests might be difficult. In this study, we propose a mapping method for a heterogeneous forest using the data of the Earth Observing-1 (EO-1) Hyperion supplemented by field survey. We introduced a band reduction method to raise classification accuracy of the Support Vector Machine classification algorithm and compared the results to the one reduced by principal component analysis (PCA), stepwise discriminant analysis (SDA), and the original data set. We also used a modified version of the Vegetation–Impervious–Soil model to create mixed vegetation classes consisting of the commonly mixing species in the area and classified them using Decision Tree classification method. We managed to achieve 84.28% approximately using our band reduction method which is 2.36% increase compared to PCA (81.92%), 1.43% compared to the SDA (82.85%), and 7.61% compared to the original data set (76.67%). Introducing the mixed vegetation classes raised the overall accuracy even higher (85.79%).

Towards reconstruction of the lost Late Bronze Age intra-caldera island of Santorini, Greece

During the Late Bronze Age, the island of Santorini had a semi-closed caldera harbour inherited from the 22 ka Cape Riva Plinian eruption, and a central island referred to as ‘Pre-Kameni’ after the present-day Kameni Islands. Here, the size and age of the intracaldera island prior to the Late Bronze Age (Minoan) eruption are constrained using a photo-statistical method, complemented by granulometry and high-precision K-Ar dating. Furthermore, the topography of Late Bronze Age Santorini is reconstructed by creating a new digital elevation model (DEM). Pre-Kameni and other parts of Santorini were destroyed during the 3.6 ka Minoan eruption, and their fragments were incorporated as lithic clasts in the Minoan pyroclastic deposits. Photo-statistical analysis and granulometry of these lithics, differentiated by lithology, constrain the volume of Pre-Kameni to 2.2–2.5 km3. Applying the Cassignol-Gillot K-Ar dating technique to the most characteristic black glassy andesite lithics, we propose that the island started to grow at 20.2 ± 1.0 ka soon after the Cape Riva eruption. This implies a minimum long-term lava extrusion rate of ~0.13–0.14 km3/ky during the growth of Pre-Kameni.

Changing human-environment interactions in medium mountains: the Apuseni Mts (Romania) as a case study

The study of human-environment relationships in mountain areas is important for both theoretical and practical reasons, as many mountain areas suffer similar problems, such as depopulation, unemployment and natural hazards. Medium mountains constitute a special case within mountains, because they are more populated but less attractive as tourist destinations than high mountains. In this context, the Apuseni Mts (Romania) are considered as a case study. In this paper, we apply GIS-based, quantitative methods to characterize the strength and dynamics of human-environment interactions, taking into consideration some environmental factors (elevation, relative height, slope, river distance, lithology, land cover, natural attractions) as well as historical population and recent tourism data. We found that population density has strong (r2>0.8) relationships with all relief factors (elevation, relative height, slope, river distance), and that best-fit functions are nonlinear. We outlined the varying demographic scenarios by elevation zones and interpreted the historically switching sign of population change versus elevation relationship. We demonstrated that lithology also has an impact on the spatial distribution of population, although it is not independent from the relief effect. The land cover of the mainly cultural landscape is very strongly correlated with relief parameters (especially slope), which suggests good adaptation. We pointed out the dominance of karst objects in the natural tourism potential of the Apuseni Mts and also explored further components of real tourism (spas, heritage, towns). Finally, we concluded that the environmental settings investigated do in fact constrain the spatial framework of society, but socio-economic changes in history can be explained from the side of society, which conforms to the theory of cultural possibilism.

Notable Glaciokarsts of the World

In this chapter, notable glaciokarsts of the world are presented. Geographical location, geologic and tectonic settings, climatic conditions, glaciation phases as well as surface and underground karst landforms are presented about each selected region. Obviously, the areal extent, the degree of exploration and the amount of publicly available information are different in each case. Historically, the first glaciokarst studies were based on the Alps, the Pyrenees, the Dinaric Alps and the British Isles, and they have remained in the focus since then. Hence, these regions are presented here in more detail, but even these presentations can be considered only short overviews. Some other glaciokarst terrains, such as Scandinavia or the Rocky Mountains, have also been thoroughly studied but later in history; nevertheless, there are abundant internationally available publications about them. Certain parts of the Balkan Peninsula, the Apennines or even Anatolia received high attention more recently and novel methods have been used to investigate their glaciokarst terrains. The Carpathians and the Appalachians, which are also discussed in this chapter, are extensively studied mountains in general, but glaciokarsts occupy a relatively small proportion in them. On the other hand, there are still regions, which are difficult to access, where glaciokarsts are poorly explored, and/or the available literature is limited (or the publications are only in Russian, for instance). Some of them, namely, the Altai Mountains, the Greater Caucasus, the Tian Shan, the Pamir and the Patagonian archipelago, are also briefly presented here. Finally, it is noted that our selection does not contain all glaciokarsts of the world because it is beyond the scope of this chapter.

History of Glaciokarst Research

In this chapter the research history of glaciokarsts is described from 1880 in the following topics: morphological descriptions (landforms on glaciokarst terrains, cave explorations on glaciokarsts), hydrologic and speleological analysis of subglacial and periglacial karst aquifers, new methodologies in glaciokarst research (dating methods, formal stratigraphy, GIS, computer simulations), age of synthesis, anthropogenic effects and climate change on glaciokarsts.

Characteristics and Genesis of Subsurface Features in Glaciokarst Terrains

Glaciokarst terrains are rich not only in specific landforms, but in subsurface forms as well. Long, complex cave systems are widespread in glaciokarst terrains, and the deepest caves are almost all found in glaciokarsts. On the other hand, as for the volume of cave chambers and passage dimensions, glaciokarst caves are not among the largest ones. One of the most important questions about glaciokarst speleogenesis is whether subglacial cave development exists at all, and if so, how effective it is. Other important issues are the age of glaciokarst caves and the karst hydrology of glaciokarst terrains. Characteristic features of alpine caves are vadose shafts and (sub)horizontal passage levels. The two main variations of passage profiles are the tubular phreatic and the canyon-like vadose cross-sections, moreover, the combination of the previous two also exists, it is the so-called keyhole profile. Among small-scale cave features, paragenetic shapes and scallops are presented in this chapter. Characteristic glaciokarst cave sediments are coarse debris, which are mainly the results of extreme high discharges, fine-grained varved carbonates, which are deposited due to back-flooding conditions, and speleothems, which grow mostly during warm periods, but if some special conditions are satisfied, they may grow even below actually glacier-covered terrains due to the so-called “common-ion effect”. Further on, cryogenic cave calcites are also formed in glaciokarst caves, but their amount is insignificant. As for the karst hydrology, extreme fluctuations are characteristic to glaciokarsts, meaning both high seasonal changes and relatively high daily changes according to melt cycles. Using U-series and cosmogenic nuclide methodology to date speleothems and detrital cave sediments, it is now evident that the majority of glaciokarst caves are polygenetic in origin, surviving one or more glacial periods. Preglacial caves (i.e. caves evolving since at least the Pliocene) are common in the Alps. On the other hand, there are approved postglacial caves as well, which are related to drumlins or isostatic fissures. Finally, subglacial speleogenesis is also proved to be possible, though it has a low rate. Ice-contact cave development takes place when a connected aquifer is formed in the glacier ice and in the neighbouring karstic rock mass.

DEM-based morphometry of large-scale sand dune patterns in the Grand Erg Oriental (Northern Sahara Desert, Africa)

Formerly, sand dune patterns were investigated mostly by aerial and satellite images, but more recently, geomorphometric analysis based on digital elevation models (DEMs) has become an important approach. In this paper, sand dune patterns of the Grand Erg Oriental (Sahara) are studied using the De Ferranti (2014) DEM, which is a blending of SRTM (Shuttle Radar Topography Mission), ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) and other elevation datasets. In the Grand Erg Oriental, there are four large-scale dune pattern types with gradual transitions between them and with several subtypes, namely P1, consisting of large, branching linear dunes; P2, a complex pattern including small-size and widely spaced star and dome dunes; P3, a network type created mostly from crescentic dunes; and finally, P4, consisting of large and closely spaced star dunes. The largest dunes with 90–100-m mean height can be found in the southern parts of the Grand Erg Oriental, where P1 and P4 patterns dominate, and these areas are also characterised by the most intensive sand accumulation with 25–30-m equivalent sand thickness. In the present study, we use regression analysis to investigate the functional relationships between sand dune characteristics. Further on, we have elaborated a DEM-based method to delineate dunes and calculate sand volumes and dune orientations. Comparing wind rose data and sand dune axis rose diagrams, it is concluded that in some parts of the Grand Erg Oriental, the present dune types and patterns are in agreement with the actual wind regime, but in other cases, the present dune patterns are at least partially the results of former wind regimes.

DEM-derived markers of drainage network changes in the Eastern Alpine Foothills

The study area is situated between the uplifting Alps and the subsiding Little Hungarian Plain, between 16°–17° E and 47°–47.5° N. The differential vertical motion implies neotectonic activity and some associated geomorphologic features (e.g. wind gaps, small streams in large valleys, etc.) may be observed as a result of drainage reorganization. After ∼8.7 Ma the area was characterized by a wide alluvial plain and a marsh zone. Later on, rivers spread their gravelly sediment over the whole area, creating gravel terraces in the west and an almost continuous gravel cover in the eastern, planar terrain. The drainage network in the hilly region is oriented to the NW–SE alluviation direction, but each river has several abrupt turns in its lower course. In order to identify wide and planar features some DEM-derived markers were used. First, two parameters were considered for each pixel: slope angle and relative height. Second, two parameters were used to classify wind gaps: incision of the valley bottom and relative elevation. In our case, the less uplifted, but more deeply incised valleys are the most obvious markers of drainage reorganization. Using the mentioned methods, terraced valleys, wide alluvial valleys and deeply incised valleys, as well as wind gaps, are recognizable and help interpretation of former river connections. The spatial pattern of the identified wind gaps suggests that drainage reorganization was significantly influenced by north-facing escarpments. Therefore, the map provides additional information to the scientific debate concerning the post-Miocene tectonic activity of the Eastern Alpine Foreland.