Jordbrugrotta

Coordinates: 66°13′10″N 14°46′21″E / 66.21944°N 14.77250°E / 66.21944; 14.77250

Jordbrugrotta
Pluragrotta
Location Rana, Norway
Depth 130 feet (40 m)[1]
Length 12,600 feet (3,800 m)[1]
Discovery 1966
Geology Limestone[2] and marble[3][4]
Entrances 2[2]
Hazards Narrow passages, cold water[5]
Access Plura and Steinugleflåget[3]

Jordbrugrotta (also known as Pluragrotta) is a cave in Rana, Norway.[4] It is the deepest cave in Northern Europe.

Cave divers occasionally visit Jordbrugrotta. It is the most dived cave in Scandinavia. Most of the other approximately 200 caves in Rana are not suitable for diving, and formation of caves has been limited due to granite forming most of the ground. Another diveable cave nearby is Litjåga.[3] Damming of Kallvatnet made diving in Jordbrugrotta possible. There have been multiple cases of fatalities and injuries among visiting cave divers. However, accidents are not more common than what can be expected from the amount of the divers.

The cave's passages were formed by the river Plura's flow on porous limestone.[2] Rock formations include marble.[3][4] Visibility in the cave is high.[6]

Discovery and exploration

Flow of river Plura in Plurdalen valley has decreased since lake Kallvatnet was dammed, and these developments have opened the cave for diving.

Jordbrugrotta was discovered in 1966 by an English team of cave explorers.[1]

Damming of lake Kallvatnet in the mid 1960s[1] decreased flow of river Plura enough to allow diving in the cave. The river still flows partially underground.[2]

Norwegian divers have explored the passages since 1990s. There has been rivalry between Finnish and Norwegian divers about exploration.[2] Two Norwegian diver's organizations have been exploring the cave system. Norsk Teknisk Dykkekrets did much of early surveying, and since 2002 Reel Action Diving has continued the work.[7] Finnish explorers discovered connection between two entrances of the cave first in September 2013. The cave has attracted Finns in recent years.[2]

Exploration is complicated by cold water and narrow passages in the underwater cave system. Side passages make it possible to get lost in the cave.[5][2] Connection between Plura and Steinugleflåget caves was not discovered for dozens of years, and the discovery was complicated by the dry cave Steinugleflåget's difficult position. Reaching its head pool requires vertical climbing of over 100 meters.[3] On the other hand, visibility in the cave's water is considered to be extremely good. It is possible to see up to 20 meters horizontally. In addition of the usually good visibility, the cave is open on all seasons.[6]

Geology

The cave's passages were formed by river Plura's flow on porous limestone.[2] Rock formations include marble.[3][4] Most of the other approximately 200 caves in Rana are not suitable for diving, and formation of caves has been limited due to granite forming most of the ground. Another similar diveable cave nearby is Litjåga. The caves are beneath Scandinavian Mountains.[3]

Sediments, boulders and sands in the cave appear to be from a periglacial or subglacial origin.[8]

Fauna

Desoria olivacea
Dicyrtoma fusca

Harsh climate in Norway limits the amount of species living in caves in comparison to Southern Europe. However, several different invertebrates have been identified by a study to live in Jordbruggrotta.[9] It is believed that there are no fish living in the cave (but footage in the 2016 documentary Diving into the Unknown[10] clearly shows a fish in one scene).[2]

Species living in the cave include:[9]

Diving accidents

Compared to amount of cave divers, accidents have been relatively uncommon at Jordbrugrotta.[6]

One of the divers who was exploring the cave in August 1988 had a hole torn in his diving suit's right leg by a sharp rock. He survived the incident with a mild case of hypothermia.[5]

On 16 August 2006, a Norwegian diver was reported missing. His body was recovered on 28 August 2006 by a team of British divers.[11][12][13]

On 6 February 2014 two Finnish divers died at the cave, and three other divers were injured. Survivors suffered from decompression sickness. Norwegian authorities summoned an international team from Britain to recover the bodies, but they deemed the operation too difficult. A diving ban was later given for the cave. However, the involved Finnish divers recovered the bodies.[2] The diving ban was overturned on 31 March 2014.[14]

See also

References

  1. 1 2 3 4 "Plura cave / Jordbru cave". Go Norway. Retrieved 9 April 2017.
  2. 1 2 3 4 5 6 7 8 9 10 "The Finns' fateful cave dive in Norway was a ghastly struggle". Helsingin Sanomat. 2014.
  3. 1 2 3 4 5 6 7 "Arctic cave diving - TEKDiveUSA". 20 January 2016.
  4. 1 2 3 4 "Verdens dypeste sumpgrotte". NRK.
  5. 1 2 3 Lundgren, Ingemar. "Cave diving Norway". Ocean Discovery. Retrieved 9 April 2017.
  6. 1 2 3 "Jordbrugrotta on pohjoismaisten luolasukeltajien suosikki – luolaston syvän osan vaarat tunnetaan". Yle. 7 February 2014.
  7. ↑ Gunnar. "Plura". Norsk Grottedykkerforbund.
  8. ↑ "The Geophysical Journal of the Royal Astronomical Society". Royal Astronomical Society. 1 January 1984. p. 232 – via Google Books.
  9. 1 2 Østbye, Eivind; Lauritzen, Stein-Erik (20 December 2013). "A checklist of invertebrates from Norwegian caves and mines" (PDF). Fauna norvegica. 33 (2013): 35–51. ISSN 1502-4873. doi:10.5324/fn.v33i0.1585.
  10. ↑ Juan Reina (2016). Takaisin pintaan [Diving into the Unknown] (in Finnish). Monami Agency Oy.
  11. ↑ "Incident Report for Period 1st January 2006 – 31st December 2006" (PDF). British Cave Rescue Council.
  12. ↑ "Grottedykker ikke funnet". NRK. 17 August 2006.
  13. ↑ "Døde under grottedykking". Dagbladet. 16 August 2006.
  14. ↑ "Opphever Plura-forbud". Rana Blad. 31 March 2014. Retrieved 17 December 2016.

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