Taevaskoja EarthCache

Kirjeldus ja huvitavaid kohti :

Ahja jõe ürgorg on maastikukaitseala ja see on üks vanimaid Eestis (asutatud 1957). Ahja jõgi algab Erastvere järvestja suubub Emajõkke. Keskjooksul asub Ahja jõe ürgoru maastikukaitseala (10,4 km²), mis ulatub 18 km pikkuselt piki jõge Koorverest kuni Valgesoo küla (Otteni) veskini. Kaitsealal kaitstakse Ahja jõe keskjooksul asuvaid Devoni ladestu Burtnieki lademe liivakivipaljandeid, mitmeid koopaid (näiteks Emalätte koobas, Neitsikoobas), jõeorgu ja seal leiduvaid kaitsealuseid liike (näiteks austria roidputke, alssosja, mets-vareskolda, nõmm-vareskolda, ungrukolda ja karukolda). .

Ahja jõe ürgoru veerudel esinevad ja taevaskodadeks või paedeks kutsutavad liivakivipaljandid on kujunenud Kesk-Devoni Burtnieki lademe liivakividesse. Ahja jõe maastikukaitseala ligikaudu 19 kilomeetri pikkusel lõigul esineb kokku 43 liivakivipaljandit, neist 27 jõe paremal ja 16 jõe vasakul kaldal. Liivakivide värvus on tugevasti varieeruv: valkjas- ja kollakashallidest kuni roosade, kohati punakate, oranžide või kollasteni. Mitmete paljandite (Puusta pae, Piirioidu pae, Savioidu pae, Savimägi, Valgemäe pae) ülaosas esineb neid katvat moreeni, mis allub üsna kergesti erosioonile. Seetõttu esineb nendelt paljanditelt sagedamini kasvavate puude varinguid.

Suur Taevaskoda on Eesti üks ilusaimaid looduslikke vaatamisväärsusi. Ahja jõe kaldal on ta kõrges okasmetsas hästi jälgitav. Paljand tõuseb jõepinnalt 22,5 meetrini, oruperve suhteline kõrgus on kuni 38 meetrit. Lühikese jalutuskäigu kaugusel on Väike Taevaskoda , mis on 190 meetrit pikk ja kuni 13 m kõrge. Legendid pajatavad Suure Taevaskoja kaljus asunud koobastest ja salakäikudest, kuraditest, hirmsast maost ja ennast kuldkammiga sugevast näkineiust

Suur-Taevaskojast umbes 400 meetrit lõuna poole jääb tuntud Võrumaa metsa¬vendade juhi Jaan Rootsi metsaven¬da¬de salga viimase punkri asukoht. Praegu on punkrist säilinud ainult suur auk metsa all. .

Saesaare veehoidlal asuv Saesaare hüdroelektrijaam ehitati 1950–1952. See töötas 1972. aastani ja renoveeriti 1991. ja 2012. aastal. Tammi betoonosa remonditi 2015. sügisel. .

Loodusele tekitatud kahju oli korvamatu ja ka majanduslik kasu jäi napiks - kolhoosidevaheline kohalik elektrijaam kaotas oma tähtsuse, kui paari aasta pärast kõrgepingeliin piirkonda jõudis. .

Pargis käitumine :

Parki sissepääs on tasuta. Pargis on mitmed matkarajad, heas seisukorras olevad jalgrajad ning mitmed infotahvlid. Taevaskoja loodusrada on 3 km pikk ja läheb piki Ahja jõe mõlemat kallast. Parkimisplatsil on ka tualetid. Võib endale ka giidi tellida ning lubatud on korajata marju ja seeni enda tarbeks. Palun ärge astuge radadelt kõrvale! Ärge visake prügi maha! Ärge kirjutage liivakivile! Kui grupis on külastajaid rohkem, kui 50, tuleb külastus eelnevalt maastikukaitseala haldajatega kokku leppida.

Geoloogia : rohkem:http://www.hkhk.edu.ee/vanker/devon

Devoni ajastul asus Eesti ala Laurussia kontinendil, mis asus ekvaatori lähistel. Laurussia koosseisu kuulusid praegune Põhja-Ameerika, Gröönimaa, Teravmäed, Inglismaa, Baltoskandia ja Vene tasandik. Kesk-Devoni ajal laius meie alal vahelduva veerežiimiga meri, kus kuhjusid erisugused setted. Peale valdavate liivakivide leiab läbilõikes savisid, dolomiitseid mergleid, paiguti ka lubjakive. Kesk-Devonis hakkas mereline bassein uuesti madalduma ning merelised olud vaheldusid mitu korda maismaalistega. Sel ajal settisid savikate kihtidega vahelduvad liivakad setted, mille paksus Võrumaal on üle 200 meetri. Tegu on põhiliselt madalmeres ja jõgede deltapiirkonnas tekkinud setetega (foto 2, 3). Paljanduv läbilõike osa algab Kesk-Devoni Pärnu lademega. Heledavärvuselised liivakivid on tüüpilised Pärnu, Gauja ja Amata lademele; Aruküla ja Burtnieki lademes valdavad punasevärvuselised erimid. Narva lademes leidub lisaks savisid ning dolomiite. .

Uus mere pealetung, mis algas Ülem-Devonis, haaras vaid Eesti kaguosa. Ülem-Devoni lademeis (Plavinase, Dubniki, Daugava) leidub savide ja dolomiitide kõrval ka lubjakive, kuid lademe kihtide paiknemisala on Eestis väga väike (foto 4). Devoni ladestu settekivimid lasuvad põikselt Siluri ja paiguti Ordoviitsiumi kihtidel. Avamused kulgevad idakirde- ja lääneedela-sihiliste vöönditena lõuna pool Pärnu-Mustvee joont. Eraldi asuv Devoni avamus on Narva jõe keskjooksul.

Burtnieki lade Burtnieki lade on Kesk-Devoni ladestiku lade. Lademe absoluutne vanus on 380,5–377 miljonit aastat. Burtnieki lade lamab Gauja lademel ja temal lasub Aruküla lade. Seda hakkas esimesena eristama Walther Gross aastal 1940. Rahvusvahelise kronostratigraafia järgi kuulub Burtnieki lade paleosoikumi aegkonna Kesk-Devoni ajastiku Givet' lademesse. Lademe avamusala kulgeb Eestis vööndina Iklast Mehikoorma–Karisilla jooneni. Vööndi laius on 25–30 km. Lätis avaneb lade Kuramaal Roja jõe ümbruskonnas, valdavalt aga Vidzeme põhjaosas, lasudes Eesti piirist Salacani, samuti ka Koiva ülemjooksul kuni Valmiera linnani. Lade paljandub nt Ahja ja Võhandu jõe kallastel. Lademe kivimkoosseisus on palju liivakivi, lademe ülemises osas esineb Lätis ka savikat aleuroliiti.

Liivakivi Liivakivi on tsementeerunud liivast koosnev settekivim, mis kuulub purdkivimite hulka, olles nende tüüpilisimaks esindajaks. Mineraloogiliselt koosneb liivakivi põhiliselt kvartsist. Tsementeerivaks materjaliks liivaterade vahel on enamasti peenike kvartsipuru, kaltsiumkarbonaat või rauaoksiidid. Rauaoksiidid annavad liivakivile ka punaka värvuse. Puhtast kvartsist koosnev liivakivi on valget värvi. Liiv, millest liivakivi on moodustunud, on setitatud reeglina, kas vooluvee või tuule poolt. Liivakivi on enamasti kihiline, sageli esineb põimkihilisus. Liivakivi sisaldab tihti konkretsioone ja kivistisi, ehkki viimastest on reeglina säilinud vaid fragmendid. Liivakivi moondumise tulemusel tekib kvartsiit. Liivakivist koosneb suur osa Eesti aluspõhjast. Suurem osa Eesti all lasuvast Devoni ladestust koosneb liivakivist (Devoni liivakivi). Liivakivi kasutatakse ehitusmatejalina.

Selle Maaaarde logimiseks pead saatma vastused järgnevatele küsimustele:

1) Kui sa kõnnid piki jõge Saesaarelt lõunasse (jõe läänekallast mööda) siis jõuad Emalätteni. Milliseid huvitavaid geoloogilisi nähtusi sa siin näed ja kuidas need on tekkinud .

2) Mida sa näed Väikese Taevaskoja kaljul enda ees, kuidas see tõenäoliselt tekkis? Iga teooria on teretulnud :)

3) Jalutuskäigu lõpus premeeritakse sind tõeliselt ilusa vaatega Suurele Taevaskojale. Istu, lõõgastu ja joonista üles osa kaljust. Ära unusta eristada erinevaid kihte, nende värve ja kujundeid... Kas sa näed nihkega või lainelisi kihte? Kirjelda oma sõnadega, kuidas nad tõenäoliselt tekkisid. Mõtle liivakivi värvusele... Mis põhjustab seda, et liivakivi võib olla erinevat värvi? (Info stratigraafia kohta / https://et.wikipedia.org/wiki/Stratigraafia) Märka ka ilusat bioerosiooni kalju ülemises osas.

4) Vaata jõkke, seal on tõesti ilus jäänuk liustiku tegevusest - mis see on ?

5) Hüdroelektrijaam on kohe jõe kõrval ja üle Savimäe minna. See mägi on täiesti moodustunud jää ladestumisest ja seetõttu selles piirkonnas ainulaadne. Mis tüüpi muld katab liivakivi künka jalamil? Seda saab lihtsalt kindlaks teha – võta pinnaseproov ja tunneta seda oma kätega... kui see on väga kuiv, niisuta seda väheke. Otsuse võib teha selle lihtsa küsimusega: kas see laguneb käes kiiresti, tundub sõmer või on tal suured osakesed? – Siis on see liiv. Kas sel on sile või jahune tekstuur ? – Siis on see muda. Kas see tundub veidi kleepuv ning koosneb väga väikestest osakestest? – Siis see on savi.

Description and interesting places:

The Ahja River Ancient Valley is a landscape protection area and it is one of the oldest in Estonia (established 1957). The Ahja river begins in lake Erastvere and debouches into the River Emajõgi. Taevaskoja area is located along the midstream of the river between Otteni mill (a.k.a Valgesoo) and Koorvere (it is aprox. 19 km long). The aim of the park is to protect the landscape integrity of the Ahja river. The main features you can see here are the deep valley of the river itself, sandstone outcrops on the valley slopes and nice natural sandstone cliffs. The area is surrounded by high spruce forest that indicates that the soil here is rich in nutrients and can support tree growth. Understory of the forest is covered by different plants and moss.

In this area of the park the relief of the ancient valley is the most diverse and very beautiful. In geomorphology terms the surrounding tablelands have an absolute height between 50 to 100 m. They cleave their way through the large Polva-Ahja-Luutsna valley. These negative surface forms divide the area into individual uplands. The gradient of the river within the park is 1.1.-1.6 m/km, mid-course mountain river character. One of the main reasons to visit the area is to see these amazing sandstone coutcrops. They date back to the Middle Devonian Burtnieki Regional Stage and are about 380 million years old, within the park there are 43 of them. The outcrops are denuded which mean that they are exposed. The maximum height is in the Kiidjarve-Valgesoo area. The most famous outcrop is 150 m long and 24 m high, it is called Suur-Taevaskoja. Short walk from it is Väike Taevaskoda that is 190 metres long and up to 13 metres high. The word Taevaskoja means in translation Heaven’s Hall.

Legends in this area talk of caves and secret passageways and of demons and mermaids (e.g. Legend of Taebaskoja).

Approximately 400 metres to the south of the Suur Taevaskoda Cliff is the location of the last bunker of Jaan Roots, the notorious leader of Forest Brothers in Võrumaa, and his group of followers. Now you can see only a large hole in the forest in place where the bunker once was standing.

Hydroelectricity station was build in this area between 1951 and 1953, due to this Saesaare mill pond was created. This caused destruction on Saesaare rapids – the most beautiful and the largests cascades in Estonia at the time. The destruction was proven pointless in few years when electricity reached the region from Narva.

Interesting rare and protected organisms you can encounter: Austrian rippensame, dwarf scouring rush, stagshorn clubmoss, flat-stemmed clubmoss, creeping lady`s tresses, lesser butterfly orchid, Scottish wood ant, clouded apollo, kingfisher and white-throated dipper. The following river inhabitants are under protection: the sea trout, grayling, spined loach, bullhead, and thick shelled river mussel.

Park management:

Entry to the park is free of charge. There are several hiking trails, good managed pathways and many information boards. Taevaskoja nature trail is 3 km long and goes along both banks of the Ahja River. On a parking lot there are also toilets available. Also you can ask for a guide. It is allowed to collect berries and mushrooms for your consumtion.

Please do not walk of the pathways! Do not litter! Do not write into the sandstone!

Visits of more than 50 people group must be announced previous to visit to park management and coordinated with ranger.

Geology:

In Devonian era Estonia was part of Laurussia continent, which was located near the equator. (note: do not mistake with Laurasia). Laurussia contained today’s areas of North America, Greenland, Svalbard, England, Balto and the Russian plains.

The Middle Devonian rocks in South Estonia have more terrestrial origin (meaning they come from terrestrial environments like rivers, lakes, desserts, alluvial, glacial outwash). They form the typical South-Estonian red sandstone which is up to 500 meters thick in some parts. The landscape was formed during the last (Weichselian) glaciation, when various glacial materials, predominantly basal tills, were deposited on top of the underlying sandstone bedrock. The thickness of the glacial deposits can reach up to more than 100-150 m. The glacial deposits act as aquifers in cases where they are thick enough, but the underlying Devonian sandstone is the main aquifer. In simple terms an aquifer is a body of saturated rock through which water can easily move. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than other types of rocks. The aquitard (note: An aquitard is a rock with low permeability) underlying the Devonian sandstone consists of Middle-Devonian marls, dolomitic marls, and claystones. Primeval valleys of Ahja River are deep, it were formed by melting ice water near the edges of glaciers (10 000 years ago).

Burtnieki Stage is independent stratigraphical unit (note: A body of rock forming a discrete and definable unit), was distinguished in 1940s. The stratotype.is the bank of the Salaca River, 12 km northwest of Lake Burtnieki in northern Latvia. Stratotype is designated exposure of stratigraphic unit that serves as the standard of reference. In Estonia, main exposures (note: similar to term outcrops, simply meaning that rocks are showing themselves above ground) are situated at Helme and on the banks of the Ahja and Võhandu rivers. The outcrops of Karksi, Härma, Koorküla and Essi are known as localities of fossil fishes. The outcrop area of Burtnieki stage forms a 25–50 km wide belt. It is mainly represented by light (white, yellowish, pinkish and greyish-brown) fine-grained medium- to weakly-cemented cross-bedded sandstones with interlayers of siltstone and clay. Cross-beddingsare sedimentary structures of horizontal units (parts) that are formed inside by incline layers.

Along the Ahja River valley typical soil types include Podzoluvisols, Planosols and Podzols on sandy loams and loamy sands of the uplands and Histosols in the peaty seepage areas along the rivers and peat bogs at the drainage divides. The landscape is intersected by primeval valleys of early Holocene origin which are 200-500 m wide and 20-40 m deep. At many places they cut into the sandstone.

Sandstone is clastic sedimentary rock composed mainly of sand sized minerals or rock particles. The formation of sandstone involves two basic stages: 1) accumulation of sand layer by layer as the result of sedimentation, either from water (as in a stream, lake, or sea) or from air (as in a desert). In our area it was mostly done by water. 2) compaction by pressure and cementing by minerals the sand is transformed to sandstone. The cement in sandstone is usually one of three materials: silica (chemically the same as quartz), calcium carbonate or iron oxide. Depending on the mix and amount of these materials sandstone can have variety of colours. The colour could be very light, reddish, grey or even dark. For example if there is many Fe the sandstone would turn red.

Sandstone can be very easily eroded. On this site you can see bioerosion done by birds that are nesting in the sandstone cliff (making holes in them) and by roots of trees. Erosion by natural forces as wind and especially by water (by river itself, different streams, rain...). And of course erosion done by humans as they wrote their messages inside the sandstone. In case of really strong erosion sandstone can easily colapse and create landslides.

To log this Earthcache you must send answers to these questions and complete simple task:

1) as you walk along the river south from Saesaare (west river bank) you will encounter Emaläte (Mother´s spring), What kind of interesting geological feature you can see here and how it was formed.

2) What do you see on the Vaike Taevaskoja cliff in front of you, how it was formed probably? Any theory :)

3) at the end of the walk you will be rewarded by really nice view of Suur Taevaskoja. Sit down, relax and draw a part of the cliff. Do not forget to distinguish different layers, their colours and shapes... Do you see any shift or wavy strata? Describe in your own words how they was probably formed. Think about the coloration of the sandstone... What causes that sandstone can have different colours? (Information about stratigraphy)Also notice nice bioerosion on upper part of the cliff.

4) Look into river, there is really nice remain from glacier activity - what it is?

5) Water power plant is next to the river and above it is hill called Savimägi. This hill is totally formed by glacial deposition and therefore it is unique for its ground foundation in this area . What type of soil (material) is covering the sandstone base of the hill? You can easily find this out- take a sample of soil, feel it in your hands...moist it a little if it is very dry.

Decision can be make via this simple key: Does it fall apart quickly, feels gritty. have large particles? - it is sand Does it has a smooth or floury texture? - it is silt Does it feel a little sticky, compose of really small particles? - it is clay

Sources and suggested future reading:

www.rmk.ee

http://www.hkhk.edu.ee/vanker/devon

http://sarv.gi.ee/geology/

http://www.sciencedirect.com/science/article/pii/S001282521100016X

E. Pirrus, A Kleesmentb, M Soota (2002) Joint systems in Devonian sandstones in the Kiidjarve-Taevaskoda area, southeastern Estonia; Proceedings of the Estonian Academy of Sciences, Geology

Kleesment A., Pirrus N. (2000) Fracture systems in Devonian sandstone, South Estonia; Proceedings of the Estonian Academy of Sciences, Geology 49: 284-293

Wikipedia.org