Volcanic Vein Kacov EarthCache
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Volcanic basaltic dyke, Kácov hill, Middle Bohemian region, Czech Republic
The goal of this earthcache is to show some facts about geological history of an interesting part of Central Bohemian Region.The Kácov hill is located closely to the Geopark Cesky Raj. This geopark was founded as a 25th European geopark (10/2005) mainly for unique sandstone phenomenon combined with volcanic activities. Volcanic dykes are important scenic and regional dominants, often with historical context (a double-hill Trosky with famous medieval ruins is a symbol of Bohemian Paradise, hill Muzsky is known as a place of prehistoric hillfort, other ones are Kozakov, Vysker, Baba etc.)
Kácov hill is also one of recommended places for visit. The geological importance of Kácov hill could be shown in fact, that photo with the typical shape of this rock was used as a cover for textbook „Geological history of the Czech Republic„ (Chlupac I. et al, Praha: Academia, 2002). The nature preserve of Kácov hill is one of the oldest in Czech Republic (pre-from in 1925, certified in 1953). Hill Kacov (350 m) is a natural place of interest. It is a volcanic basaltic dyke situated at the confluence of the rivers Mohelka and Jizera in the Czech Republic (Stredocesky kraj, Central Bohemian Region, near to Bohemian Paradise), about 3 km N from town Mnichovo Hradiste.
The geological bedrock (the rock underlying surface soil) in the vicinity of Kacov hill is composed of turonian sandstones and marlite (sandstone is a medium-grained sedimentary rock formed by the cementation of sand grains, marlite is a partly lithificated pelitic sediment with significant amount of CaCO3 and cenomanian (aka woodbinian), turonian and coniacian are stages of late Cretaceous epoch. Igneous lava mass of leucithic basalt (fine-grained, mafic, igneous rock composed predominantly of ferromagnesian minerals) during volcanic eruption in the period of Terciary (probably in the miocen epoch) caused perforation of superficial turonian and coniac sandstones. Later, in the periods of Terciary and Quaternary - the process of erosion (the physical removal of rock by an agent such as running water, glacial ice, or wind) caused that superficial layers of volcano were removed.
Presently, only denude basalic part of volcano (so-called volcanic chimney) remains there and this bizzare rock shape is one of geomorphological dominant of region. The igneous lava originated metamorphic rocks (rocks formed as a result of contact between magma and some rock - metamorphism under conditions in which high temperature is the dominant factor) called „kácovák„ (a stone from Kácov) – a spongious sandstone with silica grains that was succesfully used for dam construction in the past.
After visiting this site, try to answer one simple question. The question is : Are there any other hills with the same volcanic history in this region?
If yes, send at least two names to wenny.gc@c e n t r u m.cz. (remove spaces). Also put (optional condition) photo with you or your team with typical shape of the Kácov rock as a background to the listing of the cache (you can stay at the base or near top of the hill). Then your log will be granted.
Access point, free parking place : N 50 33.234 E 14 58.796 (see additional waypoints), please park here!
Cedicový suk, Vrch Kácov
Vrch Kácov se nachází severne od Mnichova Hradište, 1 km ze Zásadky a 3 km z Breziny. Tato tretihorní sopka ležící u soutoku Jizery s Mohelkou tu zanechala památku v podobe obnaženého sopecného komínu bizarního tvaru.
Geologické podloží blízkého okolí Kácova tvorí krídové (turon) pískovce a slínovce. V tretihorách, pravdepodobne ve spodním miocénu, zde došlo k sopecnému výbuchu, pri kterém žhavé lávy leucititického cedice prorazily nadložní vrstvy svrchního turonu a koniaku. V tretihorách a ctvrtohorách pak docházelo k erozním pochodum a povrchová cást sopky byla znicena.
Dnes je obnažena pouze prívodní cást sopky - sopecný komín. Ta má bizarní tvar a skalka patrí k geomorfologickým dominantám zdejšího kraje. Žhavá láva pri své ceste k zemskému povrchu kontaktne premenila okolní horniny. Vznikl tzv. kácovák - kontaktne premenený pískovec, který má natavená zrna kremene. Díky tomu se dá snadno mlít. Pískovec mel puvodne vápnitý tmel, a tak vlivem vysoké teploty vznikl pórovitý pískovec, který je lehký a navíc ve vode tvrdne. Proto se užíval ke stavbe jezu. Vlastní cedicová skalka se vypíná asi 10 m nad své okolí, není shodná s vrcholkem Kácova.
Po návšteve tohoto místa zodpovezte prosím následující jednoduchou otázku : Jsou zde v okolí i jiné vrchy se stejnou geologickou minulostí jako Kácov ? (Nehledejte po cedulích, použijte vlastní selský rozum.)
Pokud ano, pošlete aspon dve jména na e-mail: wenny.gc@c e n t r u m.cz (odstrante mezery). Na stránky listingu rovnež (nepovinné, ale uděláte mi radost ) můžete vložit fotku s vámi nebo vaším týmen s typickým tvarem vyvreliny v pozadí (vzhledem k deklarovane nizke obtiznosti a terenu postaci fotka dole u zaklady, ale maximalne doporucuji vystoupat po pesince az k vrcholu - budete odmeneni jedinycnym, vyhledem do kraje).
Po splnení podmínek Vám bude uznán log na této třetí nejstarší earthkeši v ČR.
Pristupový bod, parkovište v obci (zdarma): N 50 33.234 E 14 58.796 (viz. additional waypoints), prosim ponechte auto zde!
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arav geron