Obeliscul

In anul 1773, in cartierul Fabric, in piata din fata bisericii ortodoxe-sarbe purtand hramul Sfantului George, se construieste un obelisc. Finantarea sa este asigurata de enoriasii ortodocsi ai parohiei. In fiecare an, in 6 ianuarie, de Boboteaza, si in 23 aprilie, de ziua Sfantului George, credinciosii se perinda si se roaga in fata acestui monument.

Obeliscul se sprijina pe un soclu masiv de marmura si se termina in varf cu o cruce. Pe partea din fata a soclului se gaseste o inscriptie in limba sarba.

Pe soclu se pot observa numeroase fosile, in spatele sau gasindu-se fosila unui amonit de dimensiuni exceptionale.

Amonitii

Amonitii (cunoscuti ca si amonoizi) sunt un grup extinct de moluste, animale din sublcasa Ammonoidea din clasa Cephalopoda. Aceste moluste sunt mai apropiate de caracatite, calamari si sepii decat de speciile cu cochilie din grupul nautiloids, precum Nautilus (specie care traieste si in zilele noastre) Primii amoniti au aparut in denovian, iar ultimele au disparut in urma extinctiei din Cretacic-Paleogen.

Termenul stiintific de amonit provine de la forma spiralei, care are forma unor coarne de berbec. Plinius cel batran (decedat in 78 e.n. langa Pompeii) a numit fosilele acestor animale ammonis cornua ("coarnele lui Ammon"), facand referire la zeul egiptean Ammon (Amun), care era infatisat purtand coarne de berbec. Adeseori la capatul unui gen de amonit se gaseste terminatia -ceras, care provine din limba greaca (κέρας) si inseamna corn.

Amonitii traiau in cochilii ce erau subdivizate in mai multe "camere", corpul sau gasindu-se in ultima camera, cea aflata aproape de deschidere. Camera cea mai interioara era si cea mai veche. Pe masura ce animalul crestea si avea nevoie de mai mult spatiu, crea o cavitate mai mare in fata deschiderii, unde se muta cu totul, apoi izola aceasta camera nou formata. Acest proces se repeta de fiecare data cand amonitul crestea. Camerele lasate in urma serveau ca si "camere de plutire". O membrana delicata numita Siphuncle conecta toate aceste camere si asigura reglarea nivelului de gaz sau lichid din interiorul cochiliei pentru a ajusta pozitia in apa si pentru a-l face sa pluteasca precum un submarin. Pompand aer si umpland camerele cu gaz, amonitul putea sa pluteasca deasupra nisipului.

Majoritatea amonitilor aveau cochilii cu spirala intr-un singur plan, aplatizate cu marginile perfect ondulate, acestia fiind cunoscuti ca si amoniti homomorfi (cu forme egale). Dar existau si cochilii partial incovoiate, in forma elicoidala si totusi drepte, acest timp fiind cunoscut ca si heteromorf (forme diferite). Pe langa formele mentionate anterior, au existat si cochilii ornamentate de diferite tipuri, netede, cu modele de brazda, coaste sau ghimpi.

 Earthcache

Pentru a loga acest Earthcache, mergeti in spatele obeliscului si observati fosila cea mare . Raspundeti la intrebarile de mai jos si trimiteti-mi raspunsurile intr-un mesaj.

1. Calculati diametrul fosilei mari. (aproximativ)

2. Numiti tipul de piatra (soclul) in care se afla fosilele.

3. Ce rol avea membrana Siphuncle?

4. (Optional) Puteti incarca o fotografie cu alte fosile mai mici gasite.

The obelisk

In 1773, in the Fabric distric, right in front of the Serbian orthodox church, dedicated to Saint George, an obelisk was built. Its funding is provided by the Orthodox parishioners.

Every year on 6th January, and on 23th April (Saint George's day), the christians walk around the monument and pray. The obelisk rests on a massive marble that ends at the top with a cross. There is an inscription in Serbian on the front of the pedestal. 

The pedestal has many fossils, on the back there is a fossil of an ammonite of exceptional size.

Ammonites

Ammonoids (also known as ammonites) are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e.,octopuses, squids, cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appear during the Denovian, and the last species died out in the Cretaceous-Paleogene extinction event.

The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder (d. 79 AD near Pompeii) called fossils of these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns. Often the name of an ammonite genus ends in -ceras, which is Greek (κέρας) for "horn".

The ammonites lived in shells subdivided in chambers, and the body was housed in the last of them, near the opening. The innermost chamber was also the oldest. As the animal grew and needed more space, it would build a larger cavity in front of the opening, where it moved, and isolate a new chamber. This process was repeated as the ammonite grew. The chambers left behind served as float tanks. A delicate pipe (the siphuncle) ran through them and allowed to regulate the amount of gas or liquid inside the shell to adjust its position in the water as a submarine. By pumping air and filling the chambers with gas, the ammonite became light enough to float above the marine substrate.

Most of the ammonites had shells with the spiral in a single plane, flattened of the sides and perfectly curly, these are denominated by homomorphous amonites (equal forms). But there were also partially coiled shells, in helical form, and still straight, these ammonites, are known as heteromorphs (different forms). In addition to the previously spoken forms also emerged ornamented shells of various types: smooth, patterns of furrows, ribs and thorns.

 Earthcache

To log this Eartcache, walk behind the obelisk and observe the big ammonoid fossil . Answer the following questions and send me the answers.

1. Calculate the diameter of the big fossil. (approx.)

2. Name this type of rock (the pedestal) that contains the fossils.

3. What was the role of Siphuncle pipe?

4. (Optional) You can upload a photo of other fossils you found on the pedestal.