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Borhola Traditional Cache

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Difficulty:
1 out of 5
Terrain:
1.5 out of 5

Size: Size:   micro (micro)

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Geocache Description:

Here we'll get to know a little about the geology in Akranes // Hér fræðumst við aðeins um jarðfræði Akraness.


In this area there are lava rocks. In 1967 a well was drilled down 1400m to look for geothermal water. There was no hot water in it as had been hoped for. The heat at the bottom was 186°C. One of the reasons why the hole is "dry" and the area therefore is considered "cold" could be that the lower part of the hole consists of a very old rock, probably a lot older than 12 million years old and originates from an ancient (extinct) volcanic zone in Snæfellsnes. The upper part, on the other hand, consists of a much younger rock from the Reykjanes and Langjökull volcanic zones. The rock in the lower part of the hole is probably similar to the rock in Deildartunguhver in Borgarfjörður where huge amount of very hot water comes to the surface. The difference between these two areas is that around Deildartunguhver there are recent cracks in the bedrock and also the active volcanic zone in Snæfellsnes streches up there with recent volcanos. Nothing like this is to be found in Akranes. We can also point out that in Akranes intrusions are very rare. Intrusions are vertical intrusions that often lead hot water to the surface. // Vestan við Kalmansbraut, við gatnamótin hjá Stillholti, eru hraunklappir og þar er borhola frá 1967. Hérna var framkvæmd djúpborun niður á 1400 m vegna jarðhitaleitar. Ekki fékkst heitt vatn úr henni eins og vonast var til. Hiti í botni reyndist 186°C og hitastigull var 129°C/km. Ein ástæða þess að holan er “þurr” og svæðið telst “kalt” gæti verið sú að neðri hluti holunnar hefur mjög gamalt berg, líklega nokkuð yfir 12 milljón ára gamalt sem á uppruna sinn í fornu gosbelti kennt við Snæfellsnes (gamalt, útdautt gosbelti). Efri hlutinn, hins vegar, hefur mun yngra berg sem ættað er úr Reykjanes-Langjökulsgosbeltinu. Bergið í neðri hluta holunnar er líklega svipað að gerð og við Deildartunguhver í Borgarfirði en þar vellur samt upp gríðarlegt magn af mjög heitu vatni. Munur þessara svæða er hins vegar sá að við Deildartunguhver eru nýlegar sprungur í berggrunni auk þess sem virka gosbeltið á Snæfellsnesi teygir sig að því með nýlegum eldstöðvum og innskotum á dýpi. Ekkert slíkt er á Akranesi. Einnig má benda á að á Akranesi eru berggangar mjög fátíðir en þeir eru lóðrétt innskot sem oft veita heitu vatni til yfirborðs.

Additional Hints (Decrypt)

rusty cap

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)