Volcanic rocks
Description
In the northern part of West Bohemia, there are relicts of volcanic forms such as table rocks and monadnocks. Origin of these volcanic rocks is connected with tectonic and volcanic activity of the Ohersky rift in Tertiary. Period of this activity was determined as transition from Oligocene to Miocene (40-18 Ma) – this is a main phase of neovolcanic activity of the Bohemian massif. After this period the development of the volcanic forms continued by lateral extension of the volcanic rock masses and subsequent gravitational processes such as toppling, block slides and rock falls. These gravitational processes still continue. The well-preserved rock tables and monadnocks are located especially in the Manětínská pánev (Manětínská basin).
Relict of volcanic forms are situated also in the southern part of Pilsen. These volcanic forms pertains to Neoproterozoic Era (1000 Ma – 545 Ma) and they are concentrated into belts with SW-NE direction.
References:
[1]Geologická mapa 1:50 000, 2014. Česká geologická služba. [cit. 2014-12-17]. From http://mapy.geology.cz/geocr_50/
[2]CHLUPÁČ, I., et al., 2002, Geologická minulost České republiky. Vyd. 1. Praha: Academia, 436 s., ISBN 80-200-0914-0.
[3]MENTLÍK, P. Georeliéf Plzeňského kraje. Atlas geomorfologických forem Plzeňského kraje. [cit. 2014-12-17]. From http://www.kge.zcu.cz/geom_atlas/georelief_uvod.html