Jordbrugrotta (also known as Pluragrotta) is a cave in Rana, Norway.[4] It is the deepest cave in Northern Europe. Most caves in Rana, of which there are some 200, are not suitable for diving.

LocationRana, Norway
Depth130 feet (40 m)[1]
Length12,600 feet (3,800 m)[1]
GeologyLimestone[2] and marble[3][4]
HazardsNarrow passages, cold water[5]
AccessPlura and Steinugleflåget[3]

A popular cave diving destination, Jordbrugrotta attracts more divers than any other cave in Scandinavia. Visibility in the cave waters is high. The cave's passages were formed by the flow of the Plura river over limestone, and the cave system includes marble formations. A number of species have been identified in the cave ecosystem.

Diving became possible in Jordbrugrotta with the damming of lake Kallvatnet in the 1960s. There have been multiple injuries and fatalities among cave divers at the site, which is accessible year-round.

Discovery and exploration

Jordbrugrotta was discovered in 1966 by a team of British cave explorers.[1]

The damming of lake Kallvatnet in the mid-1960s greatly reduced water flow in the partially subterranean Plura river, making diving possible in the cave.[1][2]

Norwegian divers have been exploring and surveying the Jordbrugrotta cave system since the 1990s. Exploration has been undertaken by two Norwegian diving organizations, with Norsk Teknisk Dykkekrets doing much of the early surveying and Reel Action Diving continuing the work since 2002.[6] The cave has attracted Finnish divers in recent years, with rivalry developing between Finnish and Norwegian teams. Finnish explorers were the first to discover a connection between the two known entrances: Jordbrugrotta, and the nearby dry cave Steinugleflåget, in September 2013.[2].

Exploration is complicated by the cold water and narrow passages of the underwater cave system, and divers can get lost in its side passages.[5][2] The connection between Jordbrugrotta and Steinugleflåget caves remained undiscovered for decades, in part because of the difficult access route to the dry cave, Steinugleflåget. Reaching its head pool requires a vertical dry-cave climb of over 330 feet (100 m).[3]

Visibility in the cave's waters is considered extremely good, with divers able to see up to 66 feet (20 m). An added attraction of the cave is its accessibility in all seasons.[7]


The cave system, with its marble formations, lies beneath the Scandinavian Mountains.[3][4] It was formed by the flow of the river Plura across porous limestone.[2] Sediments, boulders and sands in the cave appear to be periglacial or subglacial in origin.[8]

A similar diveable cave nearby is Litjåga. Of some 200 caves in Rana, however, most are not suitable for diving, and cave formation has been limited owing to a predominance of granite in the region's geology. [3]


Although the harsh Norwegian climate limits the diversity of cave-dwelling species in comparison with Southern European caves, several invertebrate species have been identified in Jordbruggrotta.[9]

No fish are believed to live in the cave. Footage from the 2016 documentary Diving into the Unknown,[10] however, clearly shows a fish in one scene.[2]

Species living in the cave include:[9]

  • Arpedium quadrum
  • Belba spp.
  • Chamobates cuspidatus
  • Desoria olivacea
  • Dicyrtoma fusca
  • Leptus spp.
  • Liogluta alpestris
  • Oxypoda spectabilis
  • Porrhomma convexum
  • Psephidonus longipes
  • Siphonoperla burmeisteri

Diving accidents

Given the number of divers in the cave, accidents have been relatively infrequent at Jordbrugrotta.[7] There have, however, been a number of injuries and deaths.

In August 1988, a diver exploring the cave tore the right leg of his diving suit on a sharp rock. He survived the incident, suffering only mild hypothermia.[5]

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

On 6 February 2014, two Finnish divers died at the cave, and another three divers were injured. Survivors suffered from decompression sickness. Norwegian authorities called on an international team, which included British divers Richard Stanton, John Volanthen and Jason Mallinson, to recover the bodies. After reconnaissance diving at the site, the operation was judged too difficult, and a diving ban was subsequently placed on the cave. The Finnish divers involved returned later, without official authorization, and recovered the bodies.[2][14] Their recovery expedition was filmed as the documentary Diving Into The Unknown. The diving ban was lifted on 31 March 2014.[15]

See also


  1. "Plura cave / Jordbru cave". Go Norway. Retrieved 9 April 2017.
  2. "The Finns' fateful cave dive in Norway was a ghastly struggle". Helsingin Sanomat. 2014.
  3. "Arctic cave diving - TEKDiveUSA". 20 January 2016.
  4. "Verdens dypeste sumpgrotte". NRK.
  5. Lundgren, Ingemar. "Cave diving Norway". Ocean Discovery. Retrieved 9 April 2017.
  6. Gunnar. "Plura". Norsk Grottedykkerforbund.
  7. "Jordbrugrotta on pohjoismaisten luolasukeltajien suosikki – luolaston syvän osan vaarat tunnetaan". Yle. 7 February 2014.
  8. "The Geophysical Journal of the Royal Astronomical Society". Royal Astronomical Society. 1 January 1984. p. 232 via Google Books.
  9. Østbye, Eivind; Lauritzen, Stein-Erik (20 December 2013). "A checklist of invertebrates from Norwegian caves and mines" (PDF). Fauna norvegica. 33 (2013): 35–51. doi:10.5324/fn.v33i0.1585. ISSN 1502-4873.
  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. Kremer, William (9 May 2016). "The cave divers who went back for their friends". BBC News. Retrieved 3 July 2018.
  15. "Opphever Plura-forbud". Rana Blad. 31 March 2014. Retrieved 17 December 2016.

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