At the end of the Devonian time period there was a global sea level rise. Ireland was flooded and most of it then sat under water.
During the Carboniferous period, the majority of limestone in Ireland was formed at the bottom of a warm, tropical sea.
At this time, Ireland lay south of the Equator, covered by a warm sea containing reefs and animals, many of which are now extinct. The sea was near a large continent known as Laurussia (modern day North America, Greenland and Europe).
This rock is dated using the fossils of the shells and skeletons of sea creatures that settled on the seafloor before becoming cemented by mud to form the limestone we now see today.
Ireland was part of the Eurasian tectonic plate. During this time the African and the Eurasian plate collided causing the landscape to uplift and fold.This exposed the limestone on the surface where it weathered and eroded.
Crag Cave began to form as mildly acidic rain water dissolved the limestone along weaknesses in the joints and bedding. Eventually, a sinkhole opened up which allowed rivers and streams to flow underground. This increased the rate of cave formation.
The river continued to move deeper into the limestone as it eroded its way downwards. A system of caves and caverns developed by this point and cave formations such as stalactites and stalagmites began to grow. The last ice age had just ended and as the large volumes of ice began to melt, there was an increase in the volume of water flowing through the cave.
The Geological Survey Memoir to Sheet 162 made note of caves in the area of Castleisland. It stated that there are “caves worn by water, some of which can be traversed for some distance” (Foot et al. 1859).
Jack Coleman noticed and commented on “a line of unnamed holes running north and south approximately east of Crag House''. This may have been in reference to sinkholes that allowed the Ahroe stream to flow underground and form the Crag Cave system (Coleman, 1965).
While investigating water pollution in the Castleisland area, the waterworks supervisor David Keane told Professor John Gunn about a cave near Crag House that he had explored as a child. John Gunn and Bridget Scalon undertook some minor exploration and 3 entrances were discovered, 2 of which were blocked up. John Gunn returned to Castleisland with some students and explored the area further and mapped it. They uncovered a 300m cave consisting of two main sub-parallel passages running in a north/south direction. It culminated in a complex boulder choke with a sump pool (a flooded passage) at the foot. This cave became known as Crag Lower Cave.
Crag Lower Cave was surveyed to the north of the entrance, Poll na Gollum. Following the course of the underground Crag stream, the passage made its way through (what is now called) the Hall of Moira chamber, through the Cirith Ungol passage to the end of the section and the Green Lake. It returned through Balrog’s Bathtub to the entrance.
John Gunn published “Crag Cave, County Kerry” through the Irish Naturalists’ Journal.
After much persuasion on the part of John Gunn, cave divers examined the sump, or “Green Lake” as it was now termed.
World-renowned cave diver, Martyn Farr, visited Castleisland from Wales to explore the sump at the end of Crag Lower Cave. He found the sump to be only 2 metres deep and 8 metres long. He emerged, after a short dive, into what he later described as “caverns measureless to man”. He was followed through by John Cooper, and both explored the newly discovered Crag Upper Cave. They quickly named the cavern “Diver’s Delight”.
The boulder choke on the west side of the sump was eventually cleared and made accessible to the remainder of the team.
They surveyed 1,670m over two days and christened many of the newly-found passages and chambers with names taken from JRR Tolkien's “Lord of the Rings”.
Emerging through Aerobes Ecstasy into Diver’s Delight, the team made their way to Minas Tirith (The Big Chamber) through a well-decorated walking passage.
Beyond this large passage were the Cliffs of Emyn Muil, a 6 metre slope leading into an even larger chamber 27 metres long, 15 metres wide and 9 metres high.
They explored further into the Forest of Fangorn, an area of fine stalagmites, including The White Tower, a superb pillar.
They then proceeded into the Hall of Gondor and into other complex and superb passages.
A further 1,179m of passage was surveyed in the Spring of 1984. At the time, surveyors thought that Crag Cave was at least 3.5 kilometres long.
Today, the explored cave system now measures approximately 3.82 kilometres making it the 10th longest cave on the island of Ireland.
Future development and exploration of the cave system is likely to reveal further passages and caverns. Crag Cave might well be close to 4 kilometres long.
The development of Crag Cave into a show cave began in 1988.
Brian Judd, a cave engineer, began constructing a stairwell that led from the surface down into Diver’s Delight Chamber. Theatrical designer Michael Scott designed a special lighting system to “create a uniquely evocative visual and aural landscape”. In 1989, Crag Cave opened to the public and was officially opened by An Taoiseach, Charles Haughey, on May 31st, 1991.
In 2003, Crag Cave reached a landmark achievement with 1 million visitors who enjoyed the spectacular beauty of Ireland's most exciting showcave.
Between 1994 and 1996, Crag Cave participated in a scientific project to reconstruct the climate conditions over the past 10,000 years.
In 2000, we joined the International Show Cave Association and two years later we became part of the Association of Irish and British Show Caves.
To date, Crag Cave has welcomed over 2 million visitors.
We continue to develop the cave system as an educational, scientific and visitor resource.