Flišni velikan / Flysch giant EarthCache

SLO

FLIŠNI VELIKAN

Slovenija sicer spada med manjše države z 20.000 km², a kljub temu ima bolj raznoliko površje kot dosti večje države. Tako je Slovenija tudi morska država z izhodom na Jadransko morje. S svojimi 43 kilometri je slovenska obala tretja najkrajša obala v Evropi in sedma najkrajša na svetu. Kljub svoji kratkosti je ta obala izjemno slikovita in ponuja bogato mešanico naravnih lepot, kulturne dediščine in zgodovinskih znamenitosti.

Slovenska obala je razdeljena med več manjših, a očarljivih mest, kot so Portorož, Piran, Izola, Koper in Ankaran, kjer se prepletajo vplivi različnih kultur in zgodovinskih obdobij. Posebno pozornost si zasluži Debeli rtič, slikovit polotok na severnem delu obale, znan po svojih strmih klifih, peščenih plažah in razgibanih obalah.

NASTANEK SLOVENSKE OBALE

Današnja podoba slovenske obale je nastala z delovanjem morja. Več o tem lahko spoznate z geozakladom Naravni raj slovenske obale. Sama geološka zgradba obale pa se je konstrurirala že miljone let nazaj. Klif, tako kot večino naše obalne regije in celotno območje Krajinskega parka Debeli Rtič, gradijo flišne kamnine srednje eocenske starosti. Fliš ni ena sama kamnina, ampak ciklično zaporedje več kamnin, ki so nastale pred 40 milijoni let v globokem morju. Podvodni plazovi, ki so se sprožali ob potresnih sunkih, močnih nevihtah ali cunamijih, so odnašali mešane sedimente in jih odlagali na dno globokega morja: spodaj večje drobce, pri vrhu pa najfinejši material. Iz tako nakopičenih sedimentov so s strjevanjem nastale flišne kamnine. Kasneje se je zaradi tektonskega delovanja morski bazen zožil, morje se je umaknilo, flišne kamnine pa so se prelomile, nagubale in dvignile na površje, kjer jih lahko občudujemo še danes.

TIPI OBAL PO SVETU

Dalmatinski tip obale je podolžna obala, ki poteka vzporedno s slemeni goratega zaledja. Otoki in polotoki so del nekdanje hribovite pokrajine, ki jo je po koncu zadnje ledene dobe zalilo morje. Nekdanje doline so postale morski prelivi, nekdanji hribi pa otoki in polotoki.

Riaški tip obale poteka prečno glede na slemenitev bližnjega kopnega. Po koncu zadnje ledene dobe se je gladina morja dvignila in zalila spodnje dele nekdanjih rečnih dolin. Nastali so široki zalivi, ki jih imenujemo rie (ednina ria). Iz vmesnega hribovitega sveta so nastali višji polotoki.

Fjordski tip obale je nastal ob koncu zadnje ledene dobe, ko je morje zalilo ledeniške doline in so se te spremenile v fjorde − ozke, globoke in daleč v notranjost segajoče zalive. Stene fjordov so zelo strme, prek njih se v slapovih spuščajo reke in potoki.

Estuarski ali lijakasti tip obale je nastal tam, kjer se rečne doline v obliki lijaka odpirajo proti morju. V potopljenih rečnih ustjih plimovanje sega daleč navzgor po reki. Zaradi prepletanja rečne in morske akumulacije ter mešanja sladke in slane vode nastajajo posebni ekosistemi.

Lagunski tip obale je dobil ime po lagunah. To so plitvi zalivi, ki jih proti odprtemu morju zapirajo lidi (ednina lido) in zemeljske kose. Obala je značilna za območja, kjer je abrazijska moč vode majhna, morski tok pa prinaša večje količine peska in ga odlaga ob obali. 

Deltasti tip obale nastaja na območjih močne akumulacije pred izlivom reke v morje. Z nasipavanjem reka podaljšuje kopno. Delte so lahko v obliki pahljače, ki spominja na istoimensko grško črko delto (Nil), ali ptičje noge (Misisipi).

FLIŠNA SESTAVA

Posamično ciklično zaporedje v flišni kamnini se začne z grobozrnatimi konglomerati, ki jim običajno sledijo peščenjaki, zaključi pa se ponavadi z drobnozrnatimi muljevci oziroma laporovci. Posamezne plasti kamnin v fliših so različnih debelin, v Sloveniji so povečini dokaj tanke (debele od nekaj cm do nekaj 10 cm). Posebnost flišnih kamnin na slovenski obali je v tem, da se v zaporedjih kamnin pojavljajo posamezni sloji apnenca, ki ponekod dosegajo debeline tudi do več metrov, zato jim rečemo kar megaplasti.

GROBOZRNATI KONGLOMERATI

Konglomerati so vrsta sedimentnih kamnin, sestavljeni iz večjih zaobljenih fragmentov kamnin in mineralov, ki jim pravimo klasti. Delci so povezani z naravnim cementom, ki je lahko kremen, kalcit, železov oksid ali drugi minerali, ki zapolnjujejo praznine med klasti in jih vežejo skupaj.  Konglomerati so grobozrnati, saj vsebujejo delce, večje od 2 milimetrov.

PEŠČENJAK

Peščenjak je sedimentna kamnina. Glavna sestavina so zrna peska, običajno kremena, ki so premera med 0,0625 in 2 milimetra. Vmes med peskovitimi zrni se lahko nahajajo tudi manjši delci, kot so glina ali silt. Delci peska pa so med seboj povezani z minerali, kot so kremen, kalcit ali železovi oksidi, ki delujejo kot cement. Površina peščenjaka je običajno zrnata zaradi prisotnosti peskovitih delcev. Kamnina med posameznimi zrni vsebuje tudi pore ali praznine, zato je precej porozna. To vpliva na njeno sposobnost shranjevanja in prepuščanja vode.

Železo je pogost sestavni del peščenjaka, bodisi v obliki železovih mineralov (kot je hematit) bodisi kot del cementa, ki veže zrna peska skupaj. Ko je peščenjak izpostavljen zraku in vodi, železo oksidira in tvori železove okside, kot sta limonit ali hematit, ki dajeta kamnini rumeno, rdečo ali rjavo barvo. V notranjosti peščenjaka, kjer ni toliko stika z zrakom in vodo, je oksidacija železa manj izrazita, kar lahko povzroči sivo barvo kamnine.

LAPOROVEC

Laporovec je prav tako sedimentna kamnina, katere glavna sestavina so glineni materiali, kot so kaolinit, ilit in smektit. Med posameznimi delci se nahajajo tudi drobna zrna kremena, kalcita in dolomita, kar mu daje določeno stopnjo trdote in odpornost. Lahko vsebujejo tudi organsko snov, kar daje kamnini temnejšo barvo. Laporovec je drobnozrnat, z delci, ki so manjši od 0,0625 milimetra, površina pa je običajno gladka ali rahlo hrapava. 

EROZIJA KLIFA

Vse od svojega nastanka flišni klif nenehno spreminja svojo podobo. Procesi erozije, ki potekajo na flišu izjemno hitro, povzročajo, da se površje znižuje, pobočja pa pomikajo v smeri proti kopnemu. Zato pravimo, da se klif umika, in sicer v povprečju okrog en centimeter na leto. Zaradi delovanja morja, dežja, sonca in vetra flišne kamnine pokajo, se lomijo, drobijo in padajo na morsko obalo. Tam drobno prepernino in mehkejše laporovce morje hitro odnese , večji kamniti bloki tršega peščenjaka pa ostanejo na obali in se s časoma zaradi delovanja morskih valov spremenijo v manjše zaobljene prodnike.

UPORABA FLIŠNIH KAMNIN

Flišne kamnine se že dolgo uporabljajo kot naravni gradbeni kamen in večina starejših hiš v slovenski Istri je zgrajena prav iz blokov flišnega peščenjaka. Posebno vrednost imajo flišne kamnine tudi pri izdelavi cementa, saj je najpomembnejša surovina za pridobivanje cementa laporovec, in prav tega je v flišnih kamninah največ.

NALOGE ZA VPIS GEOZAKLADA

Odgovore pošljite preko GC profila. Zaklad lahko brez čakanja na povratne informacije logirate. V primeru napačnega ali pomanjkljivega odgovora vas informiram. Vpisi ne smejo vsebovati odgovorov na vprašanja, prav tako pa ne smejo biti vpisani brez vnaprej poslanih odgovorov. Takšni odgovori bodo nemudoma izbrisani.

1. V opisu si spoznal različne tipe obale. Pod katerega po tvojem mnenju uvrščamo slovensko obalo in zakaj?

Točka 1: FLIŠNE PLASTI

1. Kateri kamnini pripadajo debelejši plasti v flišu? Na točki 1 izmeri debelino najdebelejše plasti.
2. Peščenjak ima na morski obali za razliko od tistega v klifu zaobljene robove. Kaj je vzrok temu?

Točka 2: POD KLIFOM

1. Peščenjak na obali prepoznamo po značilni rumeni barvi. Kaj je vzrok, da na nekaterih mestih v klifu opazimo tudi sive peščenjake?
2. Na lokaciji oceni najvišjo višino klifa. 

NEOBVEZNO! K vpisu priložite sliko sebe ali predmeta z vašim GC imenom in datumom obiska. Najlepše so tiste na vrhu klifa s sončnim zahodom v ozadju.

ENG

FLYSH GIANT

Slovenia is a relatively small country with an area of 20,000 km⊃2;, yet it has a more varied landscape than many much larger countries. Slovenia is also a maritime nation with access to the Adriatic Sea. With its 43 kilometers of coastline, the Slovenian coast is the third shortest in Europe and the seventh shortest in the world. Despite its brevity, this coastline is exceptionally picturesque and offers a rich mix of natural beauty, cultural heritage, and historical landmarks.

The Slovenian coast is divided among several smaller but charming towns, such as Portorož, Piran, Izola, Koper, and Ankaran, where influences from various cultures and historical periods intertwine. Special attention should be given to Debeli Rtič, a scenic peninsula on the northern part of the coast, known for its steep cliffs, sandy beaches, and rugged shorelines.

FORMATION OF THE SLOVENIAN COAST

The current appearance of the Slovenian coast was shaped by the action of the sea. More about this can be learned from the earthcache Slovenian coast. The geological structure of the coast was formed millions of years ago. The cliff, like most of our coastal region and the entire area of the Debeli Rtič Landscape Park, is composed of flysch rocks from the middle Eocene epoch. Flysch is not a single rock type but a cyclic sequence of several rocks that formed 40 million years ago in a deep sea. Underwater landslides triggered by earthquakes, strong storms, or tsunamis transported mixed sediments and deposited them on the ocean floor: larger fragments at the bottom and the finest material at the top. These accumulated sediments eventually lithified into flysch rocks. Later, due to tectonic activity, the sea basin narrowed, the sea receded, and the flysch rocks fractured, folded, and emerged on the surface, where they can be admired today.

TYPES OF COASTLINES AROUND THE WORLD

Dalmatian type: This is a long, narrow coastline running parallel to the ridges of the mountainous hinterland. Islands and peninsulas are remnants of a once hilly landscape submerged by the sea after the last ice age. Former valleys have become marine straits, and former hills are now islands and peninsulas.

Ria type: This type runs perpendicular to the ridges of nearby land. After the last ice age, sea levels rose and inundated the lower parts of former river valleys, creating wide bays known as rias. Higher peninsulas emerged from the surrounding hilly terrain.

Fjord type: This type formed at the end of the last ice age when the sea flooded glacial valleys, turning them into fjords—narrow, deep bays that extend far inland. Fjord walls are very steep, with rivers and streams cascading down them in waterfalls.

Estuarine or Dendritic type: This type occurs where river valleys open into the sea in a funnel shape. In submerged river mouths, tidal effects extend far upstream. The mixing of river and sea sediments and the blending of fresh and saltwater create unique ecosystems.

Lagoon type: Named after lagoons, these are shallow bays separated from the open sea by sandbars (lidos) and landmasses. The coastline is typical for areas with low wave energy where coastal currents deposit large amounts of sand.

Delta type: Formed in areas of strong sediment accumulation at river mouths. Rivers build out land through sediment deposition. Deltas can be fan-shaped, resembling the Greek letter delta (Nile), or bird-foot shaped (Mississippi).

FLYSCH COMPOSITION

A single cyclic sequence in flysch rock starts with coarse-grained conglomerates, usually followed by sandstones, and ends with fine-grained siltstones or marls. The individual layers of rock in flysch are of varying thicknesses; in Slovenia, they are mostly quite thin (ranging from a few centimeters to several tens of centimeters). A unique feature of the flysch rocks on the Slovenian coast is that individual layers of limestone appear in the sequences, some of which can be several meters thick, and are referred to as megaplates.

COARSE-GRAINED CONGLOMERATES

Conglomerates are a type of sedimentary rock composed of larger rounded fragments of rock and minerals called clasts. The particles are bound together by natural cement, which can be quartz, calcite, iron oxide, or other minerals filling the gaps between the clasts and binding them together. Conglomerates are coarse-grained, containing particles larger than 2 millimeters.

SANDSTONE

Sandstone is a sedimentary rock with sand-sized grains, typically quartz, with a diameter between 0.0625 and 2 millimeters. Smaller particles, such as clay or silt, can also be present between the sand grains. The sand grains are cemented together by minerals like quartz, calcite, or iron oxides. The surface of sandstone is usually gritty due to the presence of sand particles. The rock also contains pores or voids between the grains, making it quite porous. This affects its ability to store and transmit water.

Iron is a common component of sandstone, either in the form of iron minerals (such as hematite) or as part of the cement binding the sand grains together. When sandstone is exposed to air and water, iron oxidizes and forms iron oxides, such as limonite or hematite, which give the rock its yellow, red, or brown color. In the interior of the sandstone, where there is less exposure to air and water, iron oxidation is less pronounced, leading to a gray color of the rock.

MARLSTONE

Marlstone is also a sedimentary rock, primarily composed of clayey materials like kaolinite, illite, and smectite. Among the clay particles, there are also small grains of quartz, calcite, and dolomite, giving it some degree of hardness and resistance. It may also contain organic matter, which gives the rock a darker color. Mudstone is fine-grained, with particles smaller than 0.0625 millimeters, and its surface is usually smooth or slightly rough.

CLIFF EROSION

Since its formation, the flysch cliff has been continuously changing its appearance. The erosion processes occurring on the flysch are extremely rapid, causing the surface to lower and the slopes to move towards the land. This results in the cliff retreating, averaging about one centimeter per year. Due to the actions of the sea, rain, sun, and wind, flysch rocks crack, break, crumble, and fall onto the shore. The sea quickly carries away the finer weathered material and softer mudstones, while larger, harder sandstone blocks remain on the shore and gradually become smaller, rounded pebbles due to the action of sea waves.

USES OF FLYSCH ROCKS

Flysch rocks have long been used as natural building stone, and most of the older houses in Slovenian Istria are built from blocks of flysch sandstone. Flysch rocks are also particularly valuable in cement production, as mudstone is the most important raw material for cement, and it is most abundant in flysch rocks.

GEOCACHE TASKS

Send your answers through GC profile. You can log the cache without waiting for feedback. In the event of an incorrect or incomplete answers, I will inform you. Logs with answers will be deleted immediately.

1. In the description, you learned about different types of coastlines. Under which type do you think the Slovenian coast falls and why?

Point 1: FLYSCH LAYERS

1. Which rock type makes up the thicker layers in flysch? Measure the thickness of the thickest layer at Point 1.
2. Sandstone on the coastal shore has rounded edges compared to that in the cliff. What is the reason for this?

Point 2: UNDER THE CLIFF

1. Sandstone on the coast is recognized by its distinctive yellow color. What causes some sandstone in the cliff to appear gray?
2. Estimate the maximum height of the cliff at the location.

OPTIONAL! Attach a photo of yourself or an object with your GC name and the date of your visit. The best photos are those from the top of the cliff with the sunset in the background.