Ostrzyca () is a forested conical hill in southwestern

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

. Rising 501 metres above the Kaczawskie Foothills, it is a

volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcano, volcanic object created when magma hardens within a Volcanic vent, vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if risi ...

formed during the

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

period, featuring distinctive hexagonal columnar jointing in its

basanite Basanite () is an igneous, volcanic ( extrusive) rock with aphanitic to porphyritic texture. It is composed mostly of feldspathoids, pyroxenes, olivine, and calcic plagioclase and forms from magma low in silica and enriched in alkali metal ox ...

rock. The hill is protected within the Ostrzyca Proboszczowicka nature reserve, established in 1962 to preserve its unique

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

and geological features. Ostrzyca serves as a key geopoint in the Land of Extinct Volcanoes Geopark, providing educational opportunities about volcanic processes and

geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...

Location and conservation

Ostrzyca rises above the Kaczawskie Foothills in Lower

Silesia Silesia (see names #Etymology, below) is a historical region of Central Europe that lies mostly within Poland, with small parts in the Czech Silesia, Czech Republic and Germany. Its area is approximately , and the population is estimated at 8, ...

, within the Ostrzyca Proboszczowicka nature reserve, established in 1962 to protect its valuable floristic communities and geological features. Its flanks are strewn with angular debris formed by

periglacial Periglaciation (adjective: "periglacial", referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing and freezing, very often in areas of permafrost. The meltwater may refreeze in ice wedg ...

weathering during the last Ice Age.

Geology

The summit exposes a well-developed hexagonal columnar jointing, formed as the Cenozoic basanite neck cooled and contracted. This neck intruded

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

-age via a conduit piercing Lower

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

sandstones and conglomerates.

Petrology and mineralogy

In thin section, Ostrzyca's rock reveals large

clinopyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron (Fe ...

crystals—so-called "megacrysts"—up to 3 cm long set in a fine-grained matrix of

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

, clinopyroxene,

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

and

nepheline Nepheline, also called nephelite (), is a rock-forming mineral in the feldspathoid groupa silica-undersaturated aluminosilicate, Na3 K Al4 Si4 O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatit ...

. These megacrysts are aluminian-sodian

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...

(magneiusm number 0.61–0.70) and frequently host well-formed

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

crystals up to 7 mm across. Geochemical analysis shows they are strongly enriched in light

rare-earth elements The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), are a set of ...

—up to 18 times primitive- mantle levels—and show clear positive anomalies in

zirconium Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...

hafnium Hafnium is a chemical element; it has symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dm ...

and

tantalum Tantalum is a chemical element; it has Symbol (chemistry), symbol Ta and atomic number 73. It is named after Tantalus, a figure in Greek mythology. Tantalum is a very hard, ductility, ductile, lustre (mineralogy), lustrous, blue-gray transition ...

. A narrow reaction rim around each megacryst matches the composition of the surrounding clinopyroxene in the matrix, indicating it crystallised directly from the same basanitic melt. Together, these features imply the megacrysts grew as cumulate fragments in the mid-crust and were then carried to the surface by a later pulse of primitive basanitic magma.

Geotourism

Since 2017, Ostrzyca has been promoted as a key geopoint within the Land of Extinct Volcanoes Geopark. The Sudetic Educational Centre organises field trips—co-financed by the Lower Silesian Fund for Environmental Protection—to the summit, using the hill as an open-air classroom for volcanic processes, geomorphology and the effects of climate change. Excursion content is adjusted to participants’ ages and backgrounds to maximise educational value.

References

{{DEFAULTSORT:Ostrzyca Tourist attractions in Lower Silesian Voivodeship Landforms of Lower Silesian Voivodeship Mountains of Poland Neogene volcanoes Sudetes Volcanic plugs of Europe Volcanoes of Poland Złotoryja County