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Landmannalaugar - Fjallabak Reserve

A cache by spuzva Send Message to Owner Message this owner
Hidden : 08/07/2011
Difficulty:
3 out of 5
Terrain:
3.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

Fjallabak Nature Reserve was established in 1979. The Nature reserve is 47.000 hectares and is over 500 meters above see level. The land is mountainous, sculptured by volcanoes and geothermal activity, covered by lavas, sands, rivers and lakes...



Landmannalaugar

Landmannalaugar is the largest rhyolite area of Iceland.
Here can be found composite lavas and tephra. This rhyolite area is a part of volcanic system named after Torfajökkul. The magma belongs to the transitional rock series and the volcanic system is active, having erupted during the Pleistocene and Holocene right up to historical tmes. The system is part of the South Iceland Volcanic Belt, where there is no plate rifting.

Rhyolite

Rhyolite is the most acidic eruptive rock and very similar to dacite.
It is very light in colour, oftern cream coloured, microcrystalline and seldom contains phenocrysts. Flow-banding is common and the rock cleaves into this slabs. It is very like dacite and the two rocks are difficult to distinguish in a hand specimen. However, dacite does have a better ring, when struck with hammer. Iron oxide precipitation is common and gives the rock a rusty – brown colour. Rusty streaks and tongues are common, lending rhyolite slabs and bright colour, and they are often used as a decorative material in buildings.



More information
Bedrock of the Fjallabak Nature Reserve dates back 8-10 million years. At that time the area was on the Reykjanes - Langjokull ridge rift zone. The volcano has been most productive during the last 2 million years, that is during the last Ice Age. Interglacial lava (Brandsgil) and sub-glacial (erupted under ice/water, examples being Blahnukur and Brennisteinsalda are characteristic formations in the area. To the north of the Torfajokull region sub-glacial volcanic activity produced the hyaloclastites (moberg) mountains, such as Lodmundur and Mogilshofdar. Volcanic activity in recent times (last 10.000 years) has been restricted to a few northeast ? southwest fissures, the most recent one, the Veidivotn fissure from 1480, formed Laugahraun (by the hut at Landmannalaugar), Namshraun, Nordurnamshraun, Ljotipollur and other craters which extend 30 km, further to the north Eruptions in the area tend to be explosive, previous known eruptions being around A. D 150 and 900. The area sorrounding Torfajökull glacier and Landmannalaugar contains the country's largest expanse of "most acidic eruptiv rock". It is very light in colour, often cream coloured, microcrystalline and seldom contains phenocrysts. It normally comes in grey, yellow, pink or green colour. The name of this kind of lava is rhyolitic lava

Three major types of lavas
Types of lava: Erupted lavas, the end of volcanic geosystems, usually solidify into one of the three major types of igneous rock:

1. Basaltic lavas– Basalt is an extrusive igneous rock of mafic composition (high in magnesium, iron and calcium) and has athe lowest silica content of three ignous rock types, its intrusive equivalent is gabbro. Basaltic magma is the most common magma type. It is produced along midocean ridges and at hot spots within plates, as well as in continental rift valleys. Basaltic lavas erupt when hot, fluid magmas fill up a volcano’s plumbing system abd overflow. Basaltic eruptions are rarely explosive. On a land a basaltic eruption send lava downthe flanks of volcano in great streams that can engulf everything in their path. When cool, these lavas are black or dark grey, but at their high eruption temperatures – 1000C – 1200C, they glow in red and yellows.

2. Andesitic lavas– Andesit is an extrusive igneouse rock with an intermediate silica content, its intrusive equivalent is diorite. Andesitic magmas are produced mainly in the volcanic mountain belts above subduction zones. The name comes from a prime example the Andes. The temperatures of andesitic lavas are lower then basalts, and because their silica content is higher, they flow more slowly and lumo up in sticky masses plugs the central vent of a volcano, gases can be build up beneth the plug and eventually blow off the top of the volcano.

3. Rhyolitic lavas– this is very typical lava of the sorrounding of Landmannalaugar. Rhyolite is an extrusive igneous rock of felsci composition (high in sodium and potassium) with a silica content greater then XX%. its intrusive equivalent is granite. It is light in color, often a pink, yellow or green color. Rhyolitic magmas are produced in zones, where heat from the mantle has melted large volumes of continental crust. Rhyolite has a lower melting point then andesite, becoming liquid at temperatures only from yyy C - zzz C.

When the rhyolitic lava is cooled abruptly, the magma turns into shiny black volcanic glass. You can find in the sorrounding of the coords and on the way down to the camp many stones like that. How is the name of this compact glassy rock which forms fragments with a conchodial fracture pattern, often black?? This answer has nr. 3.


Questions for you:
1. WHAT IS XX ?
2. WHAT IS yyy C - zzz C ?
3. ANSWER nr. 3.?
4. WHAT IS THE NAME OF THE PEAK ON THE COORDS?
5. ON THE PIC nr.3 YOU CAN SEE THE SCENERY VISIBLE FROM THE COORDS. WHAT IS THE DIRECTION OF THIS SCENERY?
6. WHAT YOU CAN FIND ON THE SUMMIT - close to coords?
7. NOT OBLIGATORY - BUT I APPRECIATE THE PICTURE OF YOU ON COORDS


Additional Hints (Decrypt)

Uvag gb gur dhrfgvba ae. 3 - lbh pna svaq va gur cubgbf

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)



 

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