Imagine the tour you are about to take, where the route curves away past a maze of side passages, down some of which comes the sound of underground streams and rivers traversing the depths. Exploring the cave along a path, passing the spacious chambers, clusters of stalactites and other spectacular limestone formations.
The cave begins with a limestone outcrop. It is from this rock the cave was formed. Limestone, if you remember from your geography is a sedimentary rock. It is formed form the bones and shells of sea creatures laid down on what used to be the sea bed about 350 million years ago. During the great earth movements about 270 million years ago, the sea bed lifted up and formed the continents.
One of the most important features of limestone with regard to cave formation is that it is a porous rock. Rainwater falling on the surface permeates the rock. Once inside, it finds weak patches at the joints. Water runs along these joints cutting out a tunnel as it goes. What we have got underground is a series of these tunnels which have eroded their way into each other and it is this series of tunnels which make up the passages and caverns we are now going to see.
When the cave was discovered in 1983, the only natural entrance was via a sump (which is a caving term for a flooded passageway). This is a 24ft. u-tube. It goes down 12ft., under a shelf in the rock, up 12ft. on the other side and into another cavern and it was from this other cavern the cave was first found.
In the 1980’s during a waterworks investigation a hydrologist Professor John Gunn from UCC was working locally. He was advised of the existence of the cave by a waterworks supervisor David Keane. The Professor brought with him a number of students the following summer who made a map and explored the area which subsequently became known as Crag lower cave. The cave was said to run in a north/south direction and was 300 metres long. At the northern end of it there was a pool, or sump. The Professor felt there was more of the cave to be found beyond this pool, so in 1983 he invited a Welsh cave diver called Martin Farr to explore the sump.
The dive turned out to be a surprisingly short one. A few minutes later he emerged and when he shone his flashlight in the total darkness he was thrilled. He was the first form of life to enter these caverns, and he discovered what he called “Diver’s delight”.
Even though the dive turned out to be short, it was still quite dangerous because when the mud and silt was disturbed and agitated in the sump visibility was zero … so his only way forward was by touch and feeling his way through.
Many parts of the cave were given names from J. R. Tolkein's Lord of the Rings.
The cave was developed between 1987 and 1989 by building a shaft (which is the only man-made entrance) and putting in pathways, railings, lights and a music system. It was opened to the public on 20th May 1989.
The Big Stalactite
This is a good example of a stalactite and stalagmite formation. These are made from crystals of limestone. The rainwater falls on the surface and filters through the rock, as it does so it dissolves the rock because the water is slightly acidic. So as that water arrives in the cave it contains a solution of calcium bicarbonate (dissolved limestone).
In the act of dripping from the ceiling tiny crystal deposits are left behind it is this constant dripping of water over a long period of time that form stalactites. This is one of the biggest stalactites in the cave system. A recent lab test dates it as approximately 6000 years old. We call this stalagtite 'Corn on the Cob'.
Underneath what looks like soft mud is a stalagmite, this is solid rock, it is made from the same material as the stalactite above. Water falls from the top of the stalactite and hits a hard surface underneath, it splashes forming a wider deposit below. These two are forming to meet each other and when they do join they make up what is known as a column or pillar. Behind we can see a good example of a column. These formations grow approximately 4cm. every 1,000 years.
The Big Chamber
The reason that this chamber is bigger than the chambers we have been through so far, is that three separate sections of the cave come together at this point. Earlier we discovered that the oldest part of the cave is at the top and water erodes its way downwards.
The original floodwater would have come gushing through this milky white passage high up in the cave. The water flowed at this level above one's head and one can see the remains of that passage behind. Because the rock was softer in this part of the cave the upper section wore away. The water flowed at a level we are standing at now, and we can see that passage intact just across the stream.
So the youngest part of the cave is at the bottom; where the stream flows, obviously this is only a small trickle of water in comparison to the massive volumes which once filled the cave. We can get an idea of the volume of water by the size and shape of the milky white passage.
Most of the formations we have looked at so far the stalactites and stalagmites are collectively known as Dripstone . . . these were formed by the process of water dripping from the ceiling. The formation in front of us is made from the same material Crystalline Calcite. This formation was made by the process of water oozing out through the rock. As the water flows across the rock, calcite is left behind. What is remarkable about this formation is if you notice in the center of it there is a whiter part . . . . . this whiter part is pure calcite, whereas most of the calcite is more tainted in colour.
The purest of the calcite is always at the higher level of the cave. Rainwater seeps through the rock, bringing with it impurities as it goes . . . . . so the deeper you go the more tainted the formation becomes, therefore it is a little unusual to have pure white calcite down this deep. The reddish - brown colour in the rocks is copper / iron oxide.
If you look behind you can see the purest and the prettiest of the calcite . . . . . on the ceiling looking back into the big chamber. Almost all is pure calcite apart from the red/pink where ironoxide has been washed in. Here we can also see the remains of the floor of the old high level part.
The area we have just entered is known as the kitchen. Here we ask you to use your imagination. On the right of this area of the cave we can see a wine bottle, (on the far left of the cave is a tray with drinking glasses to compliment our wine bottle!). Here we can also see a carrot and a parsnip.
Diarmuid and Grainne
The area surrounding Castleisland is known as the Sliabh Luachra area this area is rich in folklore. We have a particular story told about a couple Diarmuid and Grainne. They were a couple who were very much in love, however they had one problem, a man named Fionn also wished to marry Grainne, not for true love but because she was a king’s Daughter. He pursued them continually and the couple had to go into hiding. It is said they spend a night in a cave in the Sliabh Luachra area. Naturally we believe this was Crag Cave where Diarmuid and Grainne lived, surrounded by their six children and their dog. Unfortunately Fionn is said to be still chasing them to this day.
We call this area the Cathedral because of its nice domed shaped roof. The focus of attention for most people is this unusual shaped stalagmite. This is said to resemble a candlestick. (It gives people an indication of the rate at which calcite grows).
The bottom fat part represents a particularly wet period in pre-history... with a plentiful supply of water, therefore the bottom is round and thick. The middle part corresponds with a dry period that ended 5,000 years ago. Therefore the top part represents 5,000 years of growth. (This in not an exceptional rate of growth. It is just an example to give you an idea).
The Crystal Gallery
This area is known as the Crystal Gallery because of the white calcite and the many thousands of straw stalactites. These stalactites are like drinking straws in that they are hollow in the centre. Rainwater falls down through the centre hollow part of it and as it drops from the end of it, a tiny deposit is left behind.
With bigger ones a piece of grit comes down through the centre hollow part and becomes blocked at the end of it. Water fills up to the top of the straw and the calcite is deposited at the outside top...and this is what is what makes up the many carrot type formations we have seen a lot of in the cave system. Most of the calcite is deposited at the outside top, then less and less until it reaches a point at the bottom. These straws are extremely brittle and they often break off under their own weight.
This is one of our most famous stalagmites in the cave system. It is said to resemble the Madonna.
The Michelin Guide who rated Crag Cave with 2 stars describes the Crystal Gallery as "Eliciting Gasps of Wonder."
The cave is 3.8km. We have been through 400 metres. There are many other beautiful showcaves in Ireland, includung Ailwee in Clare, Mitchelstown in Tipperary, Dunmore in Kilkenny and Marble Arch in Fermanagh.