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Volcanoes

Muzsky

Mužský is the highest peak of the western margin of Bohemian Paradise Geopark. Nort-south trending feeder dyke of olivine nephelinite runs across the hill in the length of 140 m and width of 30–40 m. The coherent feeder is partly exposed by selective erosion and partly mantled by remnants of pyroclastic deposits. Apart of small outcrops on the top of the hill, the volcanic rocks are exposed in two abandoned quarries. The larger quarry to the south exploited the coherent feeder and left walls of coarse-grained pyroclastic deposits. The quarry on the western slope exposes olivine nephelinite with nice columnar jointing. A crack-formed cave is also result of exploitation. There are medium-grained bedded pyroclastics exposed at the margin of the quarry. The pyroclastic deposits are ill-sorted and consist of angular fragments of non-vesicular nephelinite and xenoliths of Cretaceous sediments reaching 1–5 cm in diameter. The structure of pyroclastics is clast-supported with lack of ash-fraction. These pyroclastics are products of phreatomagmatic eruption resulting from interaction of magma with surface water. Thermal shock led to intensive fragmentation of magma. Surface condition of magma/water interaction results in relatively low content of xenoliths. The age of this volcano has been determined to 19 Ma.

Face of Quarry

Basalt

Ice in the cave

GPS position

N 50° 31.695', E 15° 2.733'
[GPX]

[MAPY.CZ]

Contact

Geopark UNESCO Český ráj
Jiří Vlasák
e-mail:vlasak@geopark-ceskyraj.cz
http://www.geopark-ceskyraj.cz