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Educational Trail Rotava

Skalka

Situation map

Skalka (“Rock“) is a rocky basalt hill above Rotava close to the famous nature monument “Basalt Organ”. Both volcanic bodies of Skalka and of “Basalt Organ” lie on a fault of east-west direction.

„Skalka” („Rock”)

Recently, using geological mapping and petrographic, geochemical, radiometric, magnetic and structural geological techniques were described the architecture and the composition of the hills. They are probably small domes of from lava extruded above the original terrain. By fast solidification of lava originates nepheline basanite, the rock type similar to basalt. It consists of microscopic grains of augite, olivine, nepheline, plagioclase and magnetite. In the matrix dominates volcanic glass.

View from „Skalka” to Rotava

The Tertiary volcano was formed in several stages by repeatedly extrusion of viscous, gas-saturated lava from the mouth of the crater. Gradual increase of the mountain up to the near tower shape yielded to form of open fissures filled by last portions of the lava. Intrusions of lava were turbulent, accompanied by crushing of rocks around the chimney. Absorption of debris of schists and older basalt lava originated breccia-similar rock structures with alternating of compact and porous parts. Fragments of foreign rocks (mica schists, quartzites, granites and older basalts) constitute about a quarter of the whole volume of the rock. Rapid cooling of lava around larger xenoliths led to the creation of "stone suns”.

„Stone sun“

Fans and staircases of almost horizontally arranged columns reveal penetration of lava in open cracks in the older basalt. Skalka is also botanically significant location with different types of plants and their communities.

Fan of basalt columns

This text was written by Petr Rojík.

GPS position

N 50° 18.157', E 12° 34.307'
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