Shannon Cave
Encyclopedia
Shannon Cave is an active stream passage cave situated in County Fermanagh
, Northern Ireland
and County Cavan
in the Republic of Ireland
.
At 130 metres (426.5 ft) vertical depth, it stands joint 6th with Poulnagree in County Clare in the deepest caves of Ireland
. The cave is recorded at 5.4 kilometres (3.4 mi) in length (making it 6th longest on the island of Ireland
), but exploration is ongoing and further passage is expected to be found.
, two kilometres to the west of the terminal sump, which is the traditional source of the River Shannon
. Inlets
to the main passage are numerous. Some, such as the large "Mistake Passage" have been pushed only a short distance. Since the cave is undergoing active exploration, there remain many issues to be sorted out and the sink
s for many of these inlets remains unclear. The stream passage itself is of considerable proportions in parts, but also contains many higher level fossil passages which have been deserted by the stream. The cave contains numerous calcite
formations, with large amounts of helictites in places. Boulder chokes are frequent with several parts of the cave being quite unstable, especially the JCP passage.
, the majority of the cave lies under County Cavan
. The original entrance to the cave was in Cavan, however this is now inaccessible. The current entrance of Polltullyard is located north of the Marlbank area of Fermanagh, high in the moors.
system. The entrance was made in a shakehole adjacent to the sink point of the Hune stream, and close the border in County Cavan. The initial route was dug through a highly unstable area of glacial fill, making it extremely treacherous. Once in the cave the cavers encountered a "main" streamway into which the Hune flowed, with the upstream section leading to "JCP Passage" and the downstream section passing another significant inlet, "Mistake Passage". By the end of August, the team had progressed past several boulder chokes and explored cave passages some 1.6 kilometre (0.994196378639691 mi) in length.
Downstream, the team reached a terminus at a prominent boulder choke, through which they attempted to dig. In October 1980 a section of the choke collapsed on Rev. George Pitt while he attempted to force a passage at river level. He became trapped for 10 hours, but was freed after a major rescue effort. By 1990 the explorers had passed the newly named George's Choke. The end of the cave was reached, 400 metres downstream, at the terminal sump beneath another large boulder choke, and the extension to this point was named "The Mayfly Extension".
While discoveries were being made in Shannon Cave in 1980, attention was also being paid to a large doline
less than a kilometre away in County Fermanagh. Members of the Reyfad Group (including the aforementioned Rev. Pitt) and the Irish Caving Club worked together to dig their way into passage leading to a 30 metres (98.4 ft) underground shaft, with boulder chokes and crawls at its base. They named this cave Co-operation Pot in honour of their collaboration, but later the name Polltullyard, after the local townland, was adopted.
. Various groups of cavers attempted to dig through the terminal boulder choke, but none were successful in stabilising the passage. In 2004 cavers from the Shannon Group began in earnest to attempt to re-enter the system, and initiated a new dig in the direction of Shannon Cave. By 2005 Shannon Cave had been re-entered via a very tight section of passage named the "Rebirth Canal". The cavers had regained JCP Passage, and access to the rest of the cave as far as George's Choke, which had collapsed again as reported by cavers on the last trip into Shannon Cave. In 2007, after two years' work digging and stabilising, George's Choke was passed. The explorers reached the terminal sump, the first people to do so in twelve years.
, from the top of which led 70 metres (229.7 ft) of crawling passage to a number of deep pitch heads. The last of these pitches was found to take a small stream, which was followed at the base of the pitch to a sump. Although it has not been traced, it is likely that this stream joins the main Shannon watercourse further downstream.
Upstream, beyond the pitches, a further 150 metres (492.1 ft) of active stream passage was followed upstream to a sump. The total surveyed length of all branches in the extension came to 635 metres (2,083.3 ft).
County Fermanagh
Fermanagh District Council is the only one of the 26 district councils in Northern Ireland that contains all of the county it is named after. The district council also contains a small section of County Tyrone in the Dromore and Kilskeery road areas....
, Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...
and County Cavan
County Cavan
County Cavan is a county in Ireland. It is part of the Border Region and is also located in the province of Ulster. It is named after the town of Cavan. Cavan County Council is the local authority for the county...
in the Republic of Ireland
Republic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
.
At 130 metres (426.5 ft) vertical depth, it stands joint 6th with Poulnagree in County Clare in the deepest caves of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
. The cave is recorded at 5.4 kilometres (3.4 mi) in length (making it 6th longest on the island of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
), but exploration is ongoing and further passage is expected to be found.
Description
The cave consists in the main of a large mainstream passage running to a terminal sump. The water flowing in the cave has been dye traced to Shannon PotShannon Pot
Shannon Pot is a small lake in the Karst topography found on the slopes of Cuilcagh Mountain in County Cavan, Ireland. An aquifer-fed naturally fluctuating pool, it is the traditional source of the River Shannon.The pool itself is approximately in diameter. It was first explored by divers in 1971...
, two kilometres to the west of the terminal sump, which is the traditional source of the River Shannon
River Shannon
The River Shannon is the longest river in Ireland at . It divides the west of Ireland from the east and south . County Clare, being west of the Shannon but part of the province of Munster, is the major exception...
. Inlets
Tributary
A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...
to the main passage are numerous. Some, such as the large "Mistake Passage" have been pushed only a short distance. Since the cave is undergoing active exploration, there remain many issues to be sorted out and the sink
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
s for many of these inlets remains unclear. The stream passage itself is of considerable proportions in parts, but also contains many higher level fossil passages which have been deserted by the stream. The cave contains numerous calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
formations, with large amounts of helictites in places. Boulder chokes are frequent with several parts of the cave being quite unstable, especially the JCP passage.
Location
While the location of the entrance to the cave is in County FermanaghCounty Fermanagh
Fermanagh District Council is the only one of the 26 district councils in Northern Ireland that contains all of the county it is named after. The district council also contains a small section of County Tyrone in the Dromore and Kilskeery road areas....
, the majority of the cave lies under County Cavan
County Cavan
County Cavan is a county in Ireland. It is part of the Border Region and is also located in the province of Ulster. It is named after the town of Cavan. Cavan County Council is the local authority for the county...
. The original entrance to the cave was in Cavan, however this is now inaccessible. The current entrance of Polltullyard is located north of the Marlbank area of Fermanagh, high in the moors.
Discovery and initial exploration
The cave was discovered in August 1980 by members of the Reyfad Group, the cavers' collective responsible for exploring the ReyfadReyfad
Reyfad is a townland in County Fermanagh, Northern Ireland. It lies in the land division of Old Barr, in the civil parish of BohoThis mountainous townland is well known for its extensive cave system and Neolithic stones.The summit of the nearby hill is known as Tullybrack or Reyfad Mountain but...
system. The entrance was made in a shakehole adjacent to the sink point of the Hune stream, and close the border in County Cavan. The initial route was dug through a highly unstable area of glacial fill, making it extremely treacherous. Once in the cave the cavers encountered a "main" streamway into which the Hune flowed, with the upstream section leading to "JCP Passage" and the downstream section passing another significant inlet, "Mistake Passage". By the end of August, the team had progressed past several boulder chokes and explored cave passages some 1.6 kilometre (0.994196378639691 mi) in length.
Downstream, the team reached a terminus at a prominent boulder choke, through which they attempted to dig. In October 1980 a section of the choke collapsed on Rev. George Pitt while he attempted to force a passage at river level. He became trapped for 10 hours, but was freed after a major rescue effort. By 1990 the explorers had passed the newly named George's Choke. The end of the cave was reached, 400 metres downstream, at the terminal sump beneath another large boulder choke, and the extension to this point was named "The Mayfly Extension".
While discoveries were being made in Shannon Cave in 1980, attention was also being paid to a large doline
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
less than a kilometre away in County Fermanagh. Members of the Reyfad Group (including the aforementioned Rev. Pitt) and the Irish Caving Club worked together to dig their way into passage leading to a 30 metres (98.4 ft) underground shaft, with boulder chokes and crawls at its base. They named this cave Co-operation Pot in honour of their collaboration, but later the name Polltullyard, after the local townland, was adopted.
Collapse and re-entry
The Hune inlet entrance to Shannon was always dangerous, often dumping rocks on passing cavers and finally in 1995 it collapsed, making the cave inaccessible. During subsequent years attention was turned to Polltullyard, the downstream end of which lay within 60 m of upstream JCP Passage, according to the surveysCave survey
A cave survey is a map of all or part of a cave system, which may be produced to meet differing standards of accuracy depending on the cave conditions and equipment available underground. Cave surveying and cartography, i.e. the creation of an accurate, detailed map, is one of the most common...
. Various groups of cavers attempted to dig through the terminal boulder choke, but none were successful in stabilising the passage. In 2004 cavers from the Shannon Group began in earnest to attempt to re-enter the system, and initiated a new dig in the direction of Shannon Cave. By 2005 Shannon Cave had been re-entered via a very tight section of passage named the "Rebirth Canal". The cavers had regained JCP Passage, and access to the rest of the cave as far as George's Choke, which had collapsed again as reported by cavers on the last trip into Shannon Cave. In 2007, after two years' work digging and stabilising, George's Choke was passed. The explorers reached the terminal sump, the first people to do so in twelve years.
2008: Saint Patrick's Extension
A new dig began on a balcony above the terminal sump, attempting to push a route through the boulder choke, but progress was slow and the choke proved unstable. In early 2008 a team of British cave divers were invited over to dive the sump, now named "Young, Free and Desperate". After 40 metres (131.2 ft) the divers emerged at the far side of the choke and made a voice connection with the dry cavers on the other side. After exploring downstream for one kilometre they returned to help dig from the other side of the choke. A connection was made a week later, after a further dive. 1.2 kilometres of cave was surveyed beyond the choke, eventually terminating at a new terminal sump. This new section was named "St. Patrick's Extension".2009: Easter Extension
Methodical exploration of high-level leads in St. Patrick's Extension in 2009 led to the discovery of a tight cross-rift intercepting a section of the main streamway named "Paddy's Parade" at right-angles. The dry, tightly meandering rift, the "Snake Escape", was followed for 30 metres to a 10 metres (32.8 ft) upward pitchPitch (vertical space)
-Climbing:In rock climbing and ice climbing, a pitch is a steep section of a route that requires a rope between two belays, as part of a climbing system...
, from the top of which led 70 metres (229.7 ft) of crawling passage to a number of deep pitch heads. The last of these pitches was found to take a small stream, which was followed at the base of the pitch to a sump. Although it has not been traced, it is likely that this stream joins the main Shannon watercourse further downstream.
Upstream, beyond the pitches, a further 150 metres (492.1 ft) of active stream passage was followed upstream to a sump. The total surveyed length of all branches in the extension came to 635 metres (2,083.3 ft).