Kolac natural arch
Definition: A natural arch is a rock exposure that has a hole completely through it formed by the natural, selective removal of rock, leaving a relatively intact frame.
Several processes of erosion can contribute, usually in combination, to natural arch formation. Different sequences or combinations of these individual processes conspire to form natural arches of different types. Because the type of arch is critically dependent upon them.
Every single process relevant to natural arch formation involves the action of water, gravity, temperature variation, or tectonic pressure on rock. Wind is not a significant agent in natural arch formation. Wind does act to disperse the loose grains that result from microscopic erosion. Further, sandstorms can scour or polish already existing arches. However, wind never creates them.
Weather-eroded arches
1. Deep cracks penetrate into a sandstone layer. 2. Erosion wears away exposed rock layers and enlarges the surface cracks, isolating narrow sandstone walls, or fins. 3. Alternating frosts and thawing cause crumbling and flaking of the porous sandstone and eventually cut through some of the fins. 4. The resulting holes becomee enlarged to arch proportions by rockfalls and weathering. Arches eventually collapse, leaving only buttresses that in time will erode.
Water eroded arches
Some natural bridges may look like arches, but they form in the path of streams that wear away and penetrate the rock. Pothole arches form by chemical weathering as water collects in natural depressions and eventually cuts through to the layer below.
Fin Natural Arch
This type of natural arch is the result of erosion acting on a thin fin or wall of rock. The fin of rock can be created through any number of different processes. The important distinction is that wall collapse did not cause the opening. Rather the opening was caused by any combination of weathering, differential erosion, exfoliation, or bedding plane expansion. As a result, the opening is either an upright oval or upright slotted aperture. Many of the natural arches that have been labeled as "natural windows" fall into this category.
Several possibilities exist for why an opening might be present in a rock fin in the absence of wall collapse. The opening may be the coincidental result of an area of relatively weak cementing between the grains of the rock, e.g., in sandstone.
This usually leads to an oval aperture. Alternatively, cross-bedding may have led to a localized weakness in the rock that weathering and gravity have evacuated. Another possibility is that the opening may be so young that wall collapse has not yet started, i.e., the opening is a small precursor to what will become a semicircular aperture. In this case, the fin natural arch will evolve into a shelter natural arch or, in certain cases, a meander natural bridge. Finally, if an oval aperture expands upward such that a catenary shape is approximated under a relatively slender lintel, the opening can become quite large and last a long time. It is possible for a fin natural arch to evolve into either an arc natural arch or abandoned natural arch before it collapses.
Abandoned Natural Arch
This type of natural arch is invariably isolated and the lintel is arched. There are two roughly vertical abutments, each having a vertical rise greater than its horizontal extent. For many natural arches of this type, the lintel and abutments form a single strand of rock whose breadth varies little over most of its curved length. In other examples, one of the abutments is noticeably broader than the lintel and other abutment, but this broadening is roughly in the plane of the opening aperture. Natural arches of this type are considered old, i.e., at the end of their lifecycle. Although there is no conclusive evidence for a specific formation process, it is clear that the natural arch continues to survive due to compression strengthening. Compression strengthening made the remnant rock more resistant to erosion than the rock that once surrounded it, and hence, gave it its characteristic arched shape. This type of natural arch is rare.
How to log:
In order to log this 
(Earthcache) as 
(found) you must do the following:
Optional: Take a picture of yourself with your GPS in your hand and the arch in the background.
Answer the following questions and mail the answers to the cacheowner:
1. Estimate or measure the height of the arch.
2. How was this arch formed do you think? Motivate your answer!
3. Is this a fin natural arch or abandoned?
4. What is the second word on the nearby sign?
You do not need to wait for approval from the cacheowner to log as found. If I need additional information, I let you know. Remember to post a picture and not to
write answers in your log!
Žalostan za siromašne prijevod, njegova ispunjavanja mimo Google Translate. Možda ti može pomoc mene sa bolji prijevod?
Definicija: prirodna luka rock izlaganje koji ima rupu kroz nju potpuno formira prirodnu, selektivno uklanjanje stijena, ostavljajuci relativno netaknut okvira.
Nekoliko procesi erozije mogu doprinijeti, obicno u kombinaciji, na prirodni luk formacije. Razlicite slijed ili kombinacija od tih procesa konspirirati obliku prirodnih lukova razlicitih vrsta. Buduci da je vrsta luka je od presudne ovisi o njima.
Svaki pojedini proces relevantni za formiranje prirodnih luka ukljucuje djelovanje vode, gravitacija, temperatura varijacije, odnosno tektonske pritisak na stijeni. Vjetar nije znacajna sredstva u prirodnom lukom formaciji. Vjetar ne djeluje kako bi rastjerala labave žitarice koje proizlaze iz mikroskopskih erozije. Nadalje, oluje mogu pretraživati ili poliranje postojecih svodova. Medutim, vjetar ih nikada ne stvara.
Vrijeme-erodiranom lukova
1. Duboko prodire u pukotine pješcenjaka sloj. 2. Erozija nosi daleko izložene slojevima stijena i povecava površinske pukotine, izoliraju uske pješcenjaka zidova ili peraje. 3. Izmjenicna mrazeva i odmrzavanje uzrok pucaju i ljuštenja od poroznog pješcenjaka i eventualno rez kroz neke od peraja. 4. Rezultat rupa becomee povecati na luk omjere po rockfalls i atmosferilija. Lukovi na kraju propasti, ostavljajuci samo upornjacima da je u vrijeme ce nagrizati.
Voda bila ugrožena lukova
Neki prirodni mostovi svibanj izgledaju kao lukovi, ali oni cine na putu potoka koji nose daleko i prodiru u stijenu. Rupa lukovi obliku kemijskog trošenja su voda skuplja u prirodnim depresijama i na kraju usjecena u sloj ispod.
Fin Prirodne Arch
Ova vrsta prirodnih luka rezultat je erozije koje djeluju na tanke peraje ili zid od stijena. Fin stijena može biti kreiran kroz bilo koji broj razlicitih procesa. Važna razlika je da zid nije uzrok propasti otvaranja. Umjesto otvaranja je uzrokovan bilo koju kombinaciju trošenja, diferencijalne erozije, piling, ili ravan sloja ekspanziju. Kao rezultat toga, otvaranje je bilo uspravno ili ovalni otvor uspravno prorezom. Mnogi od prirodnih lukova koji su oznacene kao "prirodni prozora" spadaju u ovu kategoriju.
Nekoliko mogucnosti postoje za otvaranje zašto može biti prisutan u stijeni peraja u odsutnosti zida kolapsa. Otvorenje mogu biti slucajne rezultat podrucju relativno slaba cementiranja izmedu zrna stijene, na primjer, u pješcenjaka. To obicno dovodi do ovalni otvor. Alternativno, cross-platforma bi mogle dovesti do lokalizirane slabosti u stijeni koja starenje i gravitacija su evakuirani. Druga mogucnost je da je otvaranje može biti tako mlada da je zid kolaps još nije pokrenut, tj. otvor je mala prethodnica onoga što ce postati polukružni otvor. U ovom slucaju, fin prirodna luka ce se razviti u sklonište prirodni luk ili, u nekim slucajevima, meandar prirodni most. Konacno, ako je ovalni otvor širi prema gore tako da oblik lancanice aproksimiran pod relativno tanak nadvratnik, otvaranje može postati dosta velik i zadnji dugo. To je moguce za fin prirodni luk da se razvije u bilo luk prirodnih luka ili napuštena prirodni luk prije nego što ga sruši.
Napuštena Prirodne Arch
Ova vrsta prirodnih luka uvijek je izolirano i nadvratnik je zaobljena. Dva su otprilike okomite nosaca, svaki ima vertikalni rast veci od njezina horizontalnog mjeri. Za mnoge prirodne lukova ove vrste, nadvratnik i nosaca u jednu cjedilu stijena cija širina varira malo više od vecinu svojih zakrivljenih dužine. U drugim primjerima, jedna od
bataljcima primjetno je širi od nadvratnik i drugih nosaca, ali to je grubo širi u ravnini
otvor blende. Prirodna luka ove vrste smatraju se stari, tj. na kraju svog životnog ciklusa. Iako ne postoji uvjerljiv dokaz za odredene procesu formiranja, jasno je da prirodna luka i dalje da preživi, zbog kompresije jacanje. Kompresija je jacanje ostatak rock otpornije na eroziju od stijene koja jednom je tu bilo, a time, dade svojim karakteristicnim zakrivljeni oblik. Ova vrsta prirodnih luka je rijetkost.
Kako se prijaviti:
Da bi se ovaj log (Earthcache) kao (found), morate uciniti sljedece:
Opcionalno: Uzmi sliku o sebi sa svojim GPS u ruci i luk u pozadini.
Odgovorite na sljedeca pitanja i odgovore na mail cacheowner:
1. Procijeniti ili izmjeriti visinu thr luka.
2. Kako je ovaj luk formiran da li vi misliti? motivirati svoj odgovor!
3. Je li to fin prirodni luk ili napuštene?
4. Koja je druga rijec o blizini znaka?
Ne morate cekati odobrenje cacheowner da se prijavite kako se javlja. Ako trebam dodatne informacije, ja pustiti te znati. Ne zaboravite postaviti sliku, a ne na
pisati odgovore u log!
References: http://www.naturalarches.org/index.html http://en.wikipedia.org/wiki/Natural_arch
Visit my other Earthcaches:
Sweden: 
Svedsmossen Earthcache Ersdalen Earthcache Svavelbruket Kalkbrottet Rosenlunds bankar Gautelfr Druim Kamlungeforsen
Cape Verde: As dunas de Bubista
Montenegro: Vapnenac
Cuba: Mirador de Bacunayagua
Greece: Afantou beach
Italy: Torre pendente di Pisa
