Commune: Pielgrzymka (pow. złotoryjski, woj. dolnośląskie)
Framework element or context represented:
Cenozoic basalt volcanism of Central Europe and characteristic landforms developed upon hard basalt.
Primary geological/geomorphological interest:
Basalt monadnock (volcanic neck) with well-exposed columnar jointing and extensive scree slopes.
Comparative assessment justification:
The most impressive and the highest basalt monadnock in the Sudetes, untoched by quarring activity (a rarity in the region); basalt scree slopes belong to the best developed in the Bohemian Massif.
Protection status and accessibility:
The upper part of the hill, above 400 m a.s.l. is protected since 1962 as nature reserve "Ostrzyca Proboszczowicka" (2.49 ha). Access to the summit via a marked trail.
Character of site: Hill with natural basalt outcrops.
Area: 2.5 ha
Altitude: 350-501 m a.s.l.
Lithology: other igneous rocks, sandstones, conglomerates, breccias
Discipline: Geomorphology, Petrography
Process Age: Pleistocene, Neogene, *all periods
Bedrock Age: Neogene, Paleogene, *all periods
Description of primary interest:
Ostrzyca (501 m a.s.l.) is a residual hill built of Cenozoic basalt, towering by 150 m above the sourrounding gently rolling landscape cut across Lower Permian sandstone and conglomerates. It assumes a characteristic conical shape with steep slopes up to 40º inclination, therefore the hill is often mistakenly considered as a volcanic cone. Basalt builds the uppermost 60-70 m of the hill and displays well-developed columnar jointing, with individual columns 15-30 cm across. Columns dip in various directions and at various angles, which is reflected in details of slope geomorphology. Rock spurs up to 10 m high form in places where columns dip steeply into the slope, whereas benches occur where the dip is more horizontal. A crag 20 m long occurs in the summit part. Slopes are covered by extensive, largely unvegetated scree aprons supplied by mechanical disintegration of spurs and crags. Scree micromorphology indicates past transport aided by deformation of cementing ice, whereas current gravitational movement is shown by tree trunks being progressively buried by basalt scree.
Literature:
BARANIECKI L. 1951–Gołoborza Ostrzycy i Sobótki (Polish only). Czas. Geogr. 21/22: 439-440. MIGOŃ P., MACIEJAK K., ZYGMUNT M. 2002–Periglacial morphology of basalt hills in the Kaczawa Upland (Western Sudetes) (English sum.). Przegląd Geograficzny 74: 491-508.