Slovak Yellowstone - a travertine pile at Bešeňová contains vast masses of precipitated carbonate that was dissolved in strongly mineralised water from deep springs

The relief of Slovakia features two distinct geological and geomorphological formations: the Carpathian Arc and its adjacent lowlands. It was shaped by young tectonics, Tertiary volcanism, glacial sculpturing as well as peri-glacial, glacio-fluvial and fluvial processes.

The geologico-morphological conditions in the lowlands are affected particularly by less consolidated sediments, primarily sand, gravel and clays. Lowlands are former marine basins filled by silicoclastics - friable sandstone/sand, siltstone/silt, gravel/conglomerate with a maximum thickness of several thousand meters.

Floodplain forests in the Záhorská Lowland. Photo: P. Plesník

Erosive - denudating processes toward the end of Tertiary generally tended to level out the relief on the territory of Slovak lowlands and created an extensive peneplain. Through a revival of vertical movements in the Earth’s crust in the Quarternary, rivers and streams formed valleys in which they modelled their terraces. From the ancient, leveled-out surface, only remnants have survived in the form of flat hogbacks or elevated plateaux which occasionally occupy a larger surface in the form of tablelands. The relief of weakly resistant less consolidated Neogene sediments is smooth, softly cut, with small vertical differences. During the cold intervals of the Quarternary glaciations, winds blew off finer material from weathered rocks and fluvial deposits, and deposited it in the form of blankets and dunes of eolian sands, whereas fine dust material was deposited in a form of loess.

Hilly landscape of the Danubian Downs. Photo: P. Plesník

West Carpathians are composed of mountain ranges separated by intramountain depressions and river valleys. Most of them are of tectonic origin. Rivers flowing through the depressions formed plains and terraces. Intramontaneous depressions are filled mostly by lacustrine rocks. The broad and flat summits of hills inside lowlands and depressions are the remnants of ancient levelled-out surface.

Tectonic processes and the geological composition also substantially affect the relief of mountain massifs. As a result, three arch-shaped zones may be distinguished in the mountainous area of Slovakia: a zone of Flysh Belt along the northern margin of the Carpathians, a group of central core mountain ranges in the middle, and several volcanic ranges on the southern periphery of the Carpathians.

Flysh Belt landscape with a natural oil spring. Sandstone often serves a an oil collector

The Flysh Belt or outer Carpathian Flysh is built by several units which were thrust during the Tertiary and formed a huge pile of relatively flat, unrooted nappes. Layers of more resistant sandstone rhythmically alternate with softer and less resistant siltstones / claystones. In general, the relief of Flysch Belt is smoothly modelled with rare occurrence of outcropping rocky forms. More massive strata of flysh sandstones usually appear as conspicuous, bulky, steeper rising peaks and hogbacks. The predominating strata of less resistant clays show a softer relief with smaller variations in levels. A narrow Klippen Belt (from a few hundred metres to a few kilometres wide) runs along the southern edge of the flysch zone. The Klippen Belt is the most conspicuous and intricate geological feature of the Carpathians. It is a giant tectonic melange whose rocks originated in the ocean. Later when the ocean disappeared, the ocean sediments were extremely tectonically affected, squeezed, thrust and desintegrated. Solid and resistant Mesozoic carbonate rocks in a form of verticalised blocks penetrated younger and softer periKlippen sediments. The belt continues to the Eastern Carpathians and its length reaches around 600 kilometers.

A Klippen Belt carbonate "tooth" on which Orava Castle was built. Photo: P. Plesník

The core mountain ranges or central West Carpathians are built by Paleozoic cristalline core covered by late Paleozoic but mostly Mesozoic sediments. The core mountains have a nappe structure: the Tatric unit is overthrust by the Veporic one and both are tectonically covered by a pile of carbonate nappes (Krížna, Choč or Hronicum nappes). Further, the Gemeric unit of the Paleozoic age was tectonically superposed on the Veporic unit and in turn, the southern margin of the Gemeric unit was tectonically covered by the Meliatic unit of the oceanic origin, Silica unit and other nappe units. In the core ranges, erosive-denudating processes have removed the cover of the younger sedimentary rocks to such a degree that the crystalline underlay, made up of granitoid rocks or of various crystalline slates on which Mesozoic sedimentary rocks had been partially preserved, outcropped on the surface. The pile of nappes, beginning from Gemericum in the North, constitute Inner West Carpathians.

Central West Carpathians are partly covered by marine Flysh like Paleogene rocks. Inner Carpathians and south slopes of central Carpathians are covered by Buda or Hungarian marine Paleogene deposits.

Vysoké Tatry Mts. are an unmistakable product of the glacial sculpturing. Photo: P. Plesník

In the Central and Inner Carpathians, erosive denudating processes have removed the cover of the younger sedimentary rocks as well as the upper pile of nappes to such a degree that the crystalline basement, made up of granitoid rocks or of various crystalline shales outcropped on the surface. These include the highest mountain ranges of Slovakia - the High and the Low Tatras. Their relief is considerably broken up in dependence on the resistance of the rocks. The cores of granitoid rocks representing a solid and thereby also a more resistant basement usually form rounded, smoothly modelled surface forms with a rare steep rocky relief (with the exception of a glacial relief).

Landscape known as the Slovenský Kras (Slovak Karst) consists mainly of mighty Mesozoic limestones. Photo: P. Plesník

The relief on Mesozoic rocks, on the other hand, is very diversified. Resistant Mesozoic sedimentary rocks, particularly the thicker limestone formations, dolomites and quartzites often outcrop in a form of rocky peaks and various rocky forms. They sharply contrast with smoothly modelled and generally also softer cut relief on less resistant Mesozoic marlstones, slates and other sediments.

Remnants of the andesite lava flow in the Poľana Mts. Photo: V. Pichler

Volcanic mountain ranges of Slovakia have predominantly a strato-volcanic structure. It is an alternation of less resistant pyroclastic rocks with resistant massive andesite lava flows. Less frequent rhyolitic rocks have been preserved as extrusive domatic bodies, short lava flows and tuff layers frequently altered into bentonite or zeolite. The youngest volcanics are basalts. The basalt lava flew originally through the river valleys. Because of the relief inversion, they often form rocky peaks and elevated ridges. Formations of less resistant pyroclastic rocks (tuffs, tuffites) are usually related to smooth parts of slopes, while steeper to rocky parts of slopes are bound to outcropping massive andesites and basalts.

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