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Educational Trail Rotava

Basalt Organ

The situation map

The Rotava Varhany (“Organ“) is a wall of the abandoned quarry, which opened the eastern side of the basalt hill. From here goes to the west a ridge, which is by narrow saddle separated from the hill Skalka. Both places are traditional destinations of naturalists, tourists and artists. The first report of the existence of the quarry on the hill called Flössberg dates to 1785. Basalt was added to the iron ore molten up to 1818 in the manor iron works at Rotava because contains 14.6% iron oxides (mainly magnetite) and high content of fluxes, to 26.5%. Even a hundred years ago, the rock was manually mined using crowbars and hammered to aggregate for roads in count's forests.

The Rotava Organ

The present beauty of the Rotava Organ has an origin in the human activity. The adjacent meadow lined by old spruces is carefully restored bottom of the former quarry. The site was declared to be a protected area in 1953, is now registered as a Natural monument Rotava.

The Rotava Organ ridge

The Varhany volcanic body originated during the young Tertiary period 20 million years ago. The semisolid lava was pushed from the volcanic chimney to the steep volcanic dome. Therefore, we don’t find the crater on the top of the hill. By very fast cooling originated a glassy rock called limburgite, which composition resembles basalt. Limburgite consists primarily of volcanic glass in which microscopic crystals of augite, olivine, nepheline and magnetite are enclosed.

Formation of columnar jointing

The organ has “a charcoal kiln” arrangement of basalt columns. Organ originated „within moments“ during a single volcanic event. A regular column grouping shows that the lava effused calmly and without turbulence. The jointing is a response to rapid cooling of lava, accompanied by internal stress and volume shrinkage in the direction of the temperature gradient. Curved section of the flue caused the radial arrangement of columns that now we can admire the old quarry.

This text was written by Petr Rojík.

GPS position

N 50° 18.184', E 12° 34.454'
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