Komorní hůrka (literally meaning "Chamber Hill") is a rather inconspicuous hill rising to 503 metres above sea level in the flat country of the Tertiary Cheb Basin. It belongs to the youngest volcanoes in the Bohemian Massif. It was formed in the late Tertiary and early Quaternary period and in the final volcanic phase of the Upper Pleistocene some 115,000 – 15,000 years ago, with after-effects dating to the Holocene period, i.e. less than 10,000 years ago. The volcano was formed on the bed of a drying-out salt lake that had covered the territory of the present-day Cheb and Sokolov Basin. The extraordinary cultural and historical significance of the hardly noticeable hill is mainly based on the fact that it probably is the most thoroughly explored volcano in Europe and perhaps even in the world. Exploration and research conducted in and around the volcano markedly contributed to the final settlement of the dispute between Neptunists and Plutonists at the turn of the 18th and 19th century. At that time, Komorní hůrka was frequently visited and studied by leading world experts.
First reports of a targeted research of the volcano date back to 1766, when Count Zedtwitz (BR 2059, Podhradí through point) ordered the excavation of a 100-metre long drift in hope of finding coal beds. In the 19th century, experts – divided into Neptunists and Plutonists – were arguing about the origin of the hill. The Neptunists (Neptune was the Roman God of the Sea) were convinced that the hillock of Komorní hůrka was the result of sedimentation in water, while the Plutonists (Pluto was the Roman God of the Underworld) claimed that the formation of the hill was associated with "fire in the entrails of earth", i.e. the source of volcanic eruptions. The volcano was also the object of interest of J. W. Goethe, who was a famous poet, as well as a passionate natural scientist. Goethe had first visited the volcano in summer 1808 and after initially siding with Plutonists, he ultimately changed his viewpoint. Goethe persuaded Kašpar Šternberk (the co-founder of the National Museum in Prague) to participate in the exploration. He proposed to excavate an adit to prove that the hill was a volcano. Work commenced in 1826. Approximately 300 metres of drifts had been excavated before the volcanic neck was finally discovered in Trpasličí díra (Dwarf Hole) and provided clear evidence that the hill was indeed a volcano. Goethe, unfortunately, had not lived to see the triumph. Today, most of the drifts are caved in. The last relic of the period of explorations is a decorated entrance portal.
Komorní hůrka is a layered volcano created by a single Strombolian eruption, during which burning lava is ejected from the crater by gas eruptions occurring at various time intervals. Due to air flow, the several metres high slag layers accumulated mostly to the east of the crater on the site of the present-day hilltop. Towards the end of volcanic activity, lava filled the neck and the crater of the volcano, and the volcanic effusion covered a part of the slag material located near the present-day drift entrance on the southwest slope of the volcano.
In the past, volcanic ash was extracted in the area and used for park paths in Františkovy Lázně. A 15-metre deep pit, which the visitors mistakenly believe to be the volcano crater, is in fact the result of mining activities. The eruptive basalt is porous nephelenite, which constitutes a rather rare form of lava in Central Europe. A considerable volume of basalt rock was quarried for building purposes in the Middle Ages. It was used as building stone for the Black Tower of Cheb Castle. In the 1880’s Komorní hůrka was still exploited only partially and not overgrown with trees. Mining activities ultimately ended in 1951 when the locality was declared a state nature reserve. Today, the volcano belongs among National Nature Monuments and extraction of any minerals is strictly prohibited.
Source: Průvodce Komorní hůrka (A Guide to Komorní hůrka) by Karel Brož, published by: Czech Union of Conservationists in Františkovy Lázně.