Crkva sv. Vlaha
Crkva sv. Vlaha, jedan od najljepših sakralnih objekata u Dubrovniku...
Kakvu je vidimo danas, potječe iz 1715. godine. Oduševljava stilom kićenog venecijanskog baroka. Gradio ju je graditelj Marino Gropelli iz Venecije od 1706. godine i to prema zahtjevu dubrovačkog Senata koji je želio novu crkvu na mjestu stare, romaničke iz XIV. st. Prvo oštećenje doživjela je u potresu, a u pepelu je cijela nestala 1706. godine, za vrijeme strašnog požara.
Sve je tada u vatri nestalo, jedino je, nekim čudom, preživio srebreni kip sv. Vlaha. Nakon “izgnaničkih” godina provedenih u crkvici sv. Nikole na Prijekome gdje ga smjestiše, od 1715. godine na starome je mjestu. U crkvi posvećenoj njegovim imenom. Tada Dubrovčani kipu pridodaše i zapis kako su “svi ostali kipovi od zlata, srebra i mjedi bili rastopljeni u vatri, dok je kip svečev, zaštićen čudom, izvađen iz požara neoštećen”. Taj kip predstavlja jedno od najznačajnijih skulptura u Dubrovniku, a iz makete koju svetac drži u ruci iščitava se nekadašnja arhitektura grada.
U Dubrovniku se sv. Vlaho štuje od 10. stoljeća. On je parac Grada.
Prema zapisima dubrovačkih ljetopisaca sv. Vlaho je spasio Dubrovčane u 10. st. kada Mlečani usidriše svoje brodove u Gružu i pred Lokrumom. Dubrovčani s povjerenjem prihvatiše njihove priče kako će nakon što nabave hrane i pića, krenuti prema Levantu. Iskoristili su tu priliku i razgledali grad, tražeći mu slabe točke za osvojit ga. No, sv. Vlaho objavi župniku Stojku njihove namjere i spasi Grad od noćnog prepada. Opisao ga je župnik kao sijedog starca duge brade s biskupskom kapom na glavi i štapom u ruci. Onako kako nam se predstavlja s gradskih zidina i kula.
Dan sv. Vlaha slavi se 3. veljače, a parčev blagdan proglašen je i Danom Grada Dubrovnika.
VIŠE O CRKVI
Festa sv. Vlaha
O blagdanu se iz udaljenih dubrovačkih mjesta zapute vjernici u narodnim nošnjama.
Nose oznake svojih crkava i kako dolaze pred crkvu posebnim se povijanjem barjaka, tako da njegovo platno ne dosegne pod, javljaju svecu zaštitniku. Ujutro je u prepunoj crkvi svečana misa, a potom Ulicom od puča ide procesija svećenika i vjernika. Tom se prigodom nose svete moći, bizantska kruna svetog Vlaha, relikvijar ruke i noge, sveta monstranca pa Isusova pelenica. To se ljudsko mnoštvo kreće glavnom dubrovačkom ulicom, proslavljenim Stradunom i potom vraća u crkvu.
Postoji u Dubrovniku razvalina crkvice sv. Stjepana u Pustijerni za koju se vezuje jedna od najljepših i najznačajnijih legendi ovoga južnoga kamenog grada. Po toj su se priči godine 971. usred zime, u noći od 2. na 3. veljače pred gradskim zidinama ukotvile mletačke lađe. Služeći se izgovorom da se trebaju snabdjeti hranom i vodom prije putovanja prema istoku, Mlečani su slobodno ulazili u srednjovjekovni Dubrovnik, ali su njihove uhode pomno motrile broj stražara na zidinama i količinu oružja u arsenalu.
Usred zimske noći, u vrijeme kad su ulice opustjele, gradskim trgom je prema Pustijerni i crkvi sv. Stjepana išao plovan - svećenik Stojko. Crkvu je našao otvorenu, a u njoj četu nebeske vojske i pred svima sijedog starca. Obratio se svećeniku molbom da obavijesti gradske oce kako Mlečani planiraju napad na Dubrovnik, a on ih je sa svojom vojskom već nekoliko noći odbijao od gradskih zidina. Bio je obučen u biskupsko odijelo, na glavi mu mitra, u ruci štap, a na upit Stojkov tko je, odgovorio je da mu je ime Vlaho.
Tako je jedne zimske noći Dubrovnik upoznao svoga zaštitnika, svoga parca-svetog Vlaha. Sutradan se njegov glasnik uistinu obratio gradskim ocima i prenio poruku. Čim su počele užurbane pripreme na zidinama, a gradska se vrata zatvorila, Mlečani su znali da su im namjere otkrivene i krenuli su dalje.
Već se sljedeće godine 972. u Dubrovniku započinje slaviti dan zaštitnika, a u blizini gradskih vrata gradi se i prva njegova crkva. Proći će stoljeća blagostanja i slobode, a prve će se kosti svetog Vlaha, sebatskog mučenika i biskupa, u Dubrovnik prenijeti tek 1026. godine. Za njega se zna da je poginuo mučeničkom smrću za cara Dioklecijana, a živio je u 3. st. u Sebasti u Kapadociji.
Dubrovčani su noćni događaj 3. veljače označili svojim najvećim blagdanom kad se gradska vrata širom otvore svim prijateljima i vjernicima iz okolice.
U prošlosti je za svečev blagdan iz Dvora izlazio knez zaogrnut u crvenu togu, a misu pred okupljenim plemstvom, gradskim pukom i svećenstvom održavao dubrovački biskup. Pred knezom su ispred Dvora ples plesale tržnice, posebno obučene djevojke s košarama punim smokava, naranača i tek ispečenog peciva. Grad bi bio svečano urešen, a iz udaljenih seoskih župa, sve dokle je sezalo područje Dubrovačke Republike, dolazili su vjernici u svečanim narodnim nošnjama, s barjacima svojih crkava.
Za više od tisuću godina što grad pod Srđem proslavlja dan svoga zaštitnika, nije se puno toga promijenilo. Istina, Dubrovnik više nema svoga kneza niti plemstvo, ali je lijepi kameni Knežev dvor još tu, uz njega barokna crkva svetog Vlaha i na usponu prema Pustijerni četvrta po redu dubrovačka katedrala.
Svakog 2. veljače Dubrovnik proslavlja Gospu Kandeloru. Tada se u narodu ponavlja stara izreka:"Kandelora, zima fora, za njom ide sveti Blaž i govori da je laž." I uistinu, taj dan, kad se kopneni gradovi kupaju kišom, a Europa često mete snijeg, Dubrovnik je pun mimoze, sunovrata i - sunčanih, pravih proljetnih dana. Pred svečevom crkvom od jutra se puštaju bijele golubice i čitav se dan pred oltarom mole vjernici, a svećenici ih sa dvije u križ isprepletene svijeće blagosiljaju i usnama im prinose srebrnu monstrancu, rad dubrovačkih zlatara. U njoj se nalazi kost iz grla sveca za kojega se zna da je bio čudotvorac i da je u Sebasti liječio svojim dodirom.
O blagdanu se iz udaljenih dubrovačkih mjesta zapute vjernici u narodnim nošnjama. Nose oznake svojih crkava i kako dolaze pred crkvu posebnim se povijanjem barjaka, tako da njegovo platno ne dosegne pod, javljaju svecu zaštitniku. Ujutro je u prepunoj crkvi svečana misa, a potom Ulicom od puča ide procesija svećenika i vjernika. Tom se prigodom nose svete moći, bizantska kruna svetog Vlaha, relikvijar ruke i noge, sveta monstranca pa Isusova pelenica. To se ljudsko mnoštvo kreće glavnom dubrovačkom ulicom, proslavljenim Stradunom i potom vraća u crkvu.
Ne zna se što je u Dubrovniku tog dana ljepše i uzbudljivije: narodne nošnje Primorja, Župe dubrovačke ili Konavala. Izgleda kao da se vratilo vrijeme starih običaja. Pozornost plijeni šarenilo crkvenih barjaka, njihovo lepršanje na trgu iza Orlanda i skupina trombunjera, što na ramenu nose kratke široke puške čijom su bukom nekad davno Dubrovčani plašili neprijatelje.
Oni ispaljuju salve prije ulaza u Grad, na Brsaljama gdje se i u doba Republike vježbalo gađanje iz pušaka i topova. Tek u večernjim satima, kad se Grad obuče u tamu, a svečeve se moći odmaraju u riznici, gosti iz seoskih bratovština odlaze svojim kućama. Pred lijepim baroknim ulazom u parčevu crkvu zeleni se vijenac lovorike, blistaju vitraji pročelja, a sa zidina, raskošnih zgrada i crkve u prolaznike gledaju kipovi svetog Vlaha koji već stoljećima drži na ispruženoj ruci maketu Grada, kao da je prinosi svome srcu i zaštitničkom zagrljaju.
Što je vapnenac?
Vapnenac je sedimentna stijena sastavljena uglavnom od kalcijevog karbonata (CaCO3) u obliku mineralnog kalcita. Vapnenačke forme najbolje su vidljive i prepoznatljive u toplim, plitkim morskim vodama. Vapnenac je obično biološka (organska) sedimentna stijena nastala taloženjem školjaka, koralja, algi i fekalnih ostataka.
Također, može biti i kemijski (anorganski) formirana sedimentna stijena nastala taloženjem kalcijevog karbonata iz jezera, mora ili oceana.
Nastajanje vapnenca - marinski
Većina vapnenaca nastaje u plitkim, mirnim i toplim morskim vodama. U morskom okruženju lako dolazi do izvlačenja kalcijevog karbonata iz školjaka i kostura potrebnih za formiranje vapnenca. Nakon što morski organizmi izumru njihove oklopne i skeletne krhotine talože se kao sediment koji se pretvara u vapnenac. Njihovi otpadni proizvodi (kakica) također mogu doprinijeti taloženju. Vapnenci nastali na ovakav način nazivaju se biološkim sedimentnim stijenama. Njihovo biološko podrijetlo otkrivamo prisutnošću fosila u stijeni.
Neki vapnenci mogu nastati izravnim taloženjem kalcijeva karbonata iz morske ili slatke vode. Vapnence nastale na ovaj način nazivamo kemijskim sedimentnim stijenama. Po svojoj strukturi manje su obilni od biološkim vapnenaca.
Danas je na Zemlji puno vapnenačko oblikovanih okruženja. Većina ih se nalazi u pličinama između 30 stupnjeva sjeverne geografske širine i 30 stupnjeva južne geografske širine.
Nastajanje vapnenca - isparavanjem
Vapnenac može nastati i isparavanjem. Stalaktiti, stalagmiti i ostali spiljski oblici takvi su primjeri vapnenca. U pećini, kapljice vode cure odozgo kroz pukotine ili pore i dolaze do spiljskih stropova. Prije pada na pod spilje može doći do isparavanja. Kako voda isparava tako se kalcijev karbonat taloži na stropu spilje. Tijekom vremena proces isparavanja može rezultirati nastankom vrhova kalcijeva karbonata na stropu spilje. Takve naslage počinju tvoriti stalaktite. Moguć je i obrnuti proces kada se isparavanje događa na tlu spilje što omogućava nastanak stalagmita.
Vapnenac koji tako tvori spiljske oblike poznat je i kao „sedra“ te pripada kemijskim sedimentnim stijenama. Stijena poznata kao „tuf“ vapnenac je nastao isparavanjem vrućih izvora, obala jezera ili sličnih područja.
Sastav vapnenca
Vapnenac je po definiciji kamen koji sadrži najmanje 50% kalcijevog karbonata u obliku kalcitne mase. Svi vapnenci sadržavaju barem nekoliko postotaka drugih materijala. To mogu biti maleni udjeli kvarca, feldspata, gline, pirita, siderita i ostalih materijala. Također mogu sadržavati veće komade rožnjaka, pirita ili siderita.
Prisustvo kalcijevog karbonata u vapnencu daje mogućnost lake identifikacije stijene, koja se izložena hladnoj otopini 5%-tne solne kiseline – zapjeni.
Vrste vapnenca
Postoji puno naziva koji se koriste za vapnenac. Ti se nazivi temelje na tome kako je stijena nastala, njezinom izgledu, sastavu i ostalim čimbenicima. Slijedi nekoliko najčešćih naziva:
Kreda: meki vapnenac s vrlo finom teksturom obično bijele ili svijetlo sive boje. Uglavnom nastaje od vapnenačkih ostataka ljusaka mikroskopskih morskih organizama, npr. foraminifera ili vapnenačkih ostataka mnogobrojnih vrsta morskih algi.
Kokvina: Slabo-zacementiran (povezan) vapnenac koji je uglavnom nastao od krhotina slomljenih ljusaka.
Fosilizirani vapnenac: kao što mu naziv govori sadrži obilje fosila. Najčešće se radi o školjkama i kostima organizama koji tvore vapnenac.
Litografski vapnenac: gusti vapnenac s vrlo finim i vrlo ujednačenim veličinama zrna koji se pojavljuje u tankim naslagama koje se mogu lagano raslojavati u vrlo glatku površinu. Krajem 18. stoljeća razvijena je litografija. Litografija je postupak nastanaka likovnog djela u kojoj se po vapnenačkoj ploči crta masnom kredom ili litografskim tušem, pri čemu se stvara vapneni sapun. Zatim se ploča prekrije dušičnom kiselinom pomiješanom s arapskom gumom rastopljenoj u vodi. Vapneni sapun odbija zakiseljenu otopinu te su tako njenom djelovanju izloženi samo neiscrtani dijelovi kamena. Nakon toga se kamen ovlaži vodom i prijeđe valjkom premazanim tiskarskom bojom. Vlažna čista površina ne prima masnu boju, prima je jedino crtež (vapneni sapun) koji nije upio vodu. Litografija je omogućila vrlo laganu proizvodnju kopija te je postala jako raširena.
Oolitski vapnenac: sastavljen uglavnom od kalcijevog karbonata "oolites", male sfere nastale koncentričnim taloženjem kalcijevog karbonata na pješčanom zrnu ili ostatku školjke.
Sedra: vapnenac nastao isparavanjem oborina, najčešće u spiljama, nastaju spiljski oblici poput stalaktita ili stalagmita.
Tuf: vapnenac nastao taloženjem voda bogatih kalcijem iz vrućih izvora, obala jezera ili sličnih mjesta.
Fosili
Na svim spomenutim lokacijama, pronaći ćete ne samo lijep primjer sedimentne stijene vapnenca, već i veliki broj fosila. Što su uopće fosili? Oni su sve ono što dokazuje život u prošlim vremenima. Taj se dokaz prošlog života javlja u dva oblika. On može biti izravan ili neizravan.
Izravan dokaz života su fosili koje čine čvrsti dijelovi organizama. U slučaju životinja, to mogu biti fosilizirane kosti ili školjke. Ili, kada su u pitanju biljke, to može biti fosilizirano drvo ili lišće. U nekim slučajevima, fosiliziran može biti i cijeli organizam, i njegovi meki i njegovi čvrsti dijelovi. Primjeri takvih fosila su insekti zarobljeni u jantaru ili mamuti smrznuti u ledu.
Neizravan dokaz života su fosilni tragovi. To su različiti otisci stopala, repova, tragova, koje su organizmi ostavljali, a zatim su fosilizirani. Koproliti (fosilizirana kakica) su također jedan primjer fosilnih tragova.
Klasifikacija
Dva su velika klasifikacijska sustava kojima se služimo prilikom identifikacije i klasifikacije vapnenačkih i karbonatnih stijena: Folkov i Dunhamov.
Folkova klasifikacija
Robert L. Folk razvio je klasifikacijski sustav koji u prvi plan stavlja detaljnu strukturu zrna i naglašava primarnu detaljnost sastava zrna i ostalih materijala u karbonatnim stijenama. Razlikuje tri vrste sastojaka: alokeme (zrna), matriks (uglavnom mikrit) i cement (sparit). Folkov sustav koristi dvodijelne nazive: prvi dio se odnosi na dominantnost zrna, a drugi na prevladavajuće vezivo (mikrit ili sparit). Prilikom korištenja Folkovog sustava preporuča se koristiti petrografov mikroskop jer je lakše odrediti prisutne komponente u svakom uzorku.
Dunhamova klasifikacija
Dunhamova klasifikacija temelji se na strukturnim značajkama. Svako ime temelji se na teksturi zrna koje čini vapnenac. Dunham je 1962. godine objavio svoj sustav klasifikacije koji dijeli stijene u četiri glavne skupine temeljem relativnih proporcija grubljih klastičnih čestica. Dunhanovi nazivi osnova su za određivanje stijena.
Bavio se pitanjem jesu li ili nisu izvorna zrna u međusobnom kontaktu, podržavaju li se međusobno ili su karakteristična vidljiva razgraničenja. Za razliku od Folka, Dunham se bavio poroznošću stijena. Dunhamova klasifikacija je korisnija i kvalitetnija jer se temelji na teksturi, a ne na ispitivanju zrna u uzorku.
Prošećite oko crkve te da biste prijavili pronalazak odgovoritie na sljedeća pitanja:
1. Opišite teksturu i boju vapnenca na Crkvi sv. Vlaha!
2. Jesu li ovi vapnenci biološki ili kemijski vapnenci? Objasnite?
3. Pretražite lokaciju i pronađite barem jedan fosil. Je li taj fosil direktan ili indirektan dokaz o prošlom životu? (objasnite)
4. Dignite pogled! Svetac zaštitnik gleda vas s vrha crkve! Koliko je visok kip sv. Vlaha?
5. Zašto je Dunhamova metoda klasifikacije bolja od Folkove?
6. Priložite sliku s GPS-om (nije obvezno)
Pošaljite odgovore e-poštom (putem GC profila). Slobodno upišite pronalazak, a ako nešto nije u redu, obavijestit ću vas!
Church of St. Blaise
One of the most beautiful sacral buildings in Dubrovnik, the present-day Church of St Blaise...
Was constructed in 1715 in the flamboyant Venetian Baroque style. It was constructed by the Venetian master Marino Gropelli in 1706, on the commission of the Dubrovnik Senate which requested a new church on the site of the old 14th century Romanesque church.
Damaged during the earthquake for the first time, the church was destroyed completely by the devastating fire in 1706. Everything disappeared in flames, apart from the silver statue of St Blaise, which was saved by some miracle. After the years spent in exile at the Church of St Nicholas at Prijeko, the statue was returned to its old place in 1715. The people of Dubrovnik added the following inscription on the statue all other statues made of gold, silver and bronze melted in the fire, while the saints statue was miraculously undamaged. The statue is one of the most important statues in Dubrovnik, and the model of the city which the saint holds in his hand reveals the city architecture at the time.
St Blaise has been honored as the patron saint of Dubrovnik from the 10th century. According to the chroniclers of Dubrovnik, St Blaise saved the people of Dubrovnik in the 10th century when the Venetians anchored their ships in Gruž and in front of the Island of Lokrum. The people of Dubrovnik believed the Venetians assurances that they would leave for Levant after they supplied themselves with food and drink. The visitors used the opportunity to see the sights and observed the weaknesses in the City defence. However, St Blaise revealed their intentions to the parish priest Stojko and thus saved the City from the night attack. The priest described him as an old grey-haired man with a long beard, a bishops cap and a stick in his hand. Precisely the way his statues on the city walls and towers look like.
Celebrated on 3 February, St Blaises Day is also the City of Dubrovnik Day.
MORE ABOUT CHURCH
The Celebration of St. Blaise
On the saints day, churchgoers arrive from distant Dubrovnik areas, dressed in national costumes.
They carry their church emblems, and as they come before the church, they salute the patron saint by twirling the banners in such a manner that they never touch the ground.
The holy mass is held in the morning in an overcrowded church. Afterwards, a procession of priests and churchgoers line up for a procession through the street Ulica od puča. Holy reliquaries are carried on this occasion: the Byzantine crown of St. Blaise, the hand and leg reliquaries, the holy monstrance, and the shroud of Jesus. This multitude proceeds along the main street of Dubrovnik, the famous Stradun, and subsequently returns to the church.
In Dubrovnik, the ruins of the Church of St. Steven located at Pustijerna is tied to one of the most beautiful and most important legends of this southern city of stone. According to the tale, Venetian ships anchored before the city walls on the eve of February 3rd, 971, in the middle of winter. The Venetians gained free access to medieval Dubrovnik under the pretense of stocking up on food and water for their journey eastwards. However, their spies carefully noted the number of guards on the city walls, as well as the amount of ammunition in the arsenal.
In the middle of the winter night, when the streets lay deserted, Priest Stojko, the parish priest, went from the city square towards Pustijerna and the Church of St. Steven. He found the church open, and inside, the troops of a heavenly army led by a grizzled old man. He addressed the priest with a request that he inform the city fathers of how the Venetians planned to attack Dubrovnik. The old man had repelled them from the city walls with his own army for a number of nights already. He was garbed as a bishop, with a mitre on his head, and a staff in his hand. When Stojko asked him to identify himself, he answered that his name was Vlaho.
So it was that on a winter’s night, Dubrovnik met its patron, St. Blaise. The next day, his messenger did in truth confront the city fathers with the message. The Venetians knew that they had been discovered when they noted the hasty activity on the city walls and the closed city gates, and so moved on.
Already in the following year, in 972, Dubrovnik began to celebrate a day in honor of the patron saint. His first church was built near the city gates. A century of prosperity and freedom would pass. It was only in 1026 that the first remains of St. Blaise, the martyr and bishop of Sebaste, were transferred to Dubrovnik It is known that he died a martyrs death for the emperor Diocletian, and that he lived in the 3rd century in Sebaste in Capodocsia.
>The citizens of Dubrovnik marked February 3rd as their greatest holiday in memory of the nights events. A day when the city gates are wide open to all friends and churchgoers of the region.
In former times on the saints day, the Rector would leave the palace wrapped in a red toga. The Bishop of Dubrovnik would hold a mass for all the gathered nobility, the city plebeians and the priesthood. In front of the Palace and the Rector, specially garbed market-maidens would dance with baskets overflowing with figs, oranges and freshly baked rolls. The city would be festively decorated. Churchgoers would arrive in festive national costumes from far away village parishes, that extended to the far reaches of the Dubrovnik Republic, carrying their church banners.
Not much has changed in over a thousand years of patron saint celebrations in the city located under Mount Srđ. True, Dubrovnik no longer has its Rector or nobility, but the beautiful stone Rectors Palace is still here. As well as the neighboring baroque Church of St. Blaise, and up towards Pustijerna, fourth in line, the Dubrovnik Cathedral.
Regularly, on February 02nd, Dubrovnik celebrates its Virgin Mary Candlemas. An old saying is then repeated: Candelora, winters gone, followed by Saint Blaise, who says it is untrue. Indeed, on this day, when inland cities are bathed in rain, and Europe is frequently swept by snow, Dubrovnik is full of mimosa, narcissi, and - sunny, springtime days. In the morning, white pigeons are released in front of the saints church, and prayers are said in front of the altar by the faithful the entire day. The priests bless everyone with a cross shaped out of two intertwined candles, and raise a silver monstrance to their lips, the work of Dubrovnik goldsmiths. The monstrance contains a bone from the throat of a saint known as a miracle-worker in Sebaste, who healed by touch.
On the saints day, churchgoers arrive from distant Dubrovnik areas, dressed in national costumes. They carry their church emblems, and as they come before the church, they salute the patron saint by twirling the banners in such a manner that they never touch the ground. The holy mass is held in the morning in an overcrowded church. Afterwards, a procession of priests and churchgoers line up for a procession through the street Ulica od puča. Holy reliquaries are carried on this occasion: the Byzantine crown of St. Blaise, the hand and leg reliquaries, the holy monstrance, and the shroud of Jesus. This multitude proceeds along the main street of Dubrovnik, the famous Stradun, and subsequently returns to the church.
In Dubrovnik on this day, it is difficult to say what is more beautiful and more exciting: the national costumes of Primorje, Župa Dubrovačka or Konavle. It looks like the return of old traditional times. Focus is drawn towards the colorful church banners, and their fluttering, on the square behind Orlando and the group of trombunjera, who carry short, broad rifles on their shoulders. Long ago in Dubrovnik, the noise they issued used to frighten enemies away.
They emit volleys before entering the city, and at Brsalje, where rifle and cannon shooting were practiced in the days of the Republic. Only when the city is covered in evening darkness, and the saints reliquaries are resting in the treasury, do the village confraternities return home. Green laurel wreaths decorate the front of the beautiful baroque entrance of the saints church, while the stained-glass windows on the façade shine. The statue of St. Blaise gazes down at the passers-by from the city walls, elaborate buildings and churches, with an outstretched hand that holds a model of the city as it has for centuries, as if to bring it closer to the heart and embrace of the patron.
What is Limestone?
Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water.
Limestone-Forming Environment - Marine
Most limestones form in shallow, calm, warm marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and skeletons can easily extract the needed ingredients from ocean water. When these animals die their shell and skeletal debris accumulate as sediment that might be lithified into limestone. Their waste products can also contribute to the sediment mass. Limestones formed from this type of sediment are biological sedimentary rocks. Their biological origin is often revealed in the rock by the presence of fossils.
Some limestones can form by direct precipitation of calcium carbonate from marine or fresh water. Limestones formed this way are chemical sedimentary rocks. They are thought to be less abundant than biological limestones.
Today Earth has many limestone-forming environments. Most of them are found in shallow water areas between 30 degrees north latitude and 30 degrees south latitude.
Limestone-Forming Environment - Evaporative
Limestone can also form through evaporation. Stalactites, stalagmites and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor. When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited on the cave ceiling. Over time this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These deposits are known as stalactites. If the droplet falls to the floor and evaporates there a stalagmite could grow upwards from the cave floor.
The limestone that makes up these cave formations is known as "travertine" and is a chemical sedimentary rock. A rock known as "tufa" is a limestone formed by evaporation at a hot spring, lake shore, or other area.
Composition of Limestone
Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite and other minerals. It can also contain large nodules of chert, pyrite or siderite.
The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid.
Varieties of Limestone
There are many different names used for limestone. These names are based upon how the rock formed its appearance or its composition and other factors. Here are some of the more commonly used.
Chalk: A soft limestone with a very fine texture that is usually white or light gray in color. It is formed mainly from the calcareous shell remains of microscopic marine organisms such as foraminifers or the calcareous remains from numerous types of marine algae.
Coquina: A poorly-cemented limestone that is composed mainly of broken shell debris. It often forms on beaches where wave action segregates shell fragments of similar size.
Fossiliferous Limestone: A limestone that contains obvious and abundant fossils. These are normally shell and skeletal fossils of the organisms that produced the limestone.
Lithographic Limestone: A dense limestone with a very fine and very uniform grain size that occurs in thin beds that separate easily to form a very smooth surface. In the late 1700's a printing process (lithography) was developed to reproduce images by drawing them on the stone with an oil-based ink and then using that stone to press multiple copies of the image.
Oolitic Limestone: A limestone composed mainly of calcium carbonate "oolites", small spheres formed by the concentric precipitation of calcium carbonate on a sand grain or shell fragment.
Travertine: A limestone that forms by evaporative precipitation, often in a cave, to produce formations such as stalactites, stalagmites and flowstone.
Tufa: A limestone produced by precipitation of calcium-laden waters at a hot spring, lake shore or other location.
Fossils
On EarthCache location, you can find not only nice example of sedimentary rock limestone, but also nice examples of fossils. What are fossils, anyway? Well, they are anything that provides evidence of life in past ages. That evidence of life in past ages can come in two types. It can be either direct evidence or indirect evidence of past life.
Direct evidence of life are fossils of hard body parts of organisms. They can be fossilized bones or shells in case of animals. Or it can be fossilized wood or leaves in case of plants. In some cases, the entire organism can be fossilized, together with both soft and hard parts. Example of such fossils are insects trapped in amber or mammoths frozen in ice.
Indirect evidence of life are trace fossils. They are various footprints, trails, marks that were left by organisms and then fossilized. Coprolites (fossilized poo) is also one example of trace fossils.
Classification
Two major classification schemes, the Folk and the Dunham, are used for identifying limestone and carbonate rocks.
Folk classification
Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names; the first refers to the grains and the second is the root. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample.
Dunham classification
The Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains that make up the limestone. Robert J. Dunham published his system for limestone in 1962; it focuses on the depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are essentially for rock families. His efforts deal with the question of whether or not the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample.
To get the log permission, please answer the following questions:
1. Walk around Church and try to describe the texture AND color of the limestone at walls!
2. Is this limestone biological or chemical limestone? Why?
3. Search the EC location and find at least one fossil. Is this fossil direct evidence or indirect evidence of past life? (explain)
4. Look up! On the top of church is St. Blaise statue. What is the high of statue?
5. Why Dunham’s classification is better than Folk’s classification?
6. Take a photo with GPS (optional)
Please email me your answers in english (via GC-Profile). You don't have to wait for a permission to log. If your answers are incorrect, I will inform you
