Vihorlat mountains (abbreviated Vihorlat) are mountains of volcanic origin, the landscape of Vihorlatsko-gutínska section, that is placed in Eastern Slovakia. It includes the Protected Land Area Vihorlat. Vihorlat mountains in the southern and western borders with Eastern Slovak hills, in the north of the Bukovské mountains, Laborec mountains and Beskydy foothills. The Vihorlat mountains sharply emerge from the Eastern Slovak lowland. While the edges of the Eastern Slovak lowlands reach 250-300 meters above sea level, the peak of the Vihorlat reaches 1 000 meters above the sea level, while the vertical difference is 800 meters.
Young volcanic mountains in Slovakia emerged by the end of Tertiary period. In Vihorlat volcanic activity emerged later, about 15 million years ago and is connected to the emergence of deep fractures exposing roads to volcanic material. To break this system, all important volcanic center on the mountain ridges - nearby Sea Eye, by the end of Porubský and Sokolský Creek, on the Vihorlat mountain and in Kyjov mountain were placed. The most elevated mountains as Vihorlat, Veľká Trestia, Motrogon, Ščob, Veža and others were formed in the final stage of volcanic activity about 9 million years ago and are formed mostly by andezit.
Volcanic activity in Vihorlat occurred in low reaching territory and later the whole mountain was highlighted throughout the mountains high above the surroundings. As a result, most of the land does not meet the typical volcanic relief such as volcanic cones etc., but for the most part there prevails erosion-breakage forms with a demonstration of the strato volcanic structure.
Even though Vihorlat belongs amongst the youngest mountains, its surface was significantly damaged. Originally higher mountains, under the impact of erosion and frequent large landslides have gradually become smaller. The numerous slope streams carried soil-forming material and on this basis large alluvial cones were formed. The uncovered magma flows have disintegrated on large stone blocks and stone seas.