A turlough or turlach is a limestone feature that is almost unique to Ireland.
The name comes from the Irish word tuar, meaning dry, and the feature is a disappearing lake. The lake fills from water rising up through the holes in the limestone ground and it later disappears in the same way, back into the ground.
Some turloughs result from a period of heavy rain. The underground passageways become full of water and some of it comes out above ground and sits on the surface for a while, until water levels drop again.
Other turloughs are seasonal, filling up in the autumn and draining away again in spring or early summer.
Where the cave system ends under the sea, turloughs can be controlled by the tide, with the water level in the lake rising and falling as the tide comes in and out.
Most touloughs flood to just a few metres in depth and Ireland’s largest covers about 1 square mile.
Turloughs are common in Ireland but rare elsewhere. This is because in Ireland the limestone forms low land close to sea level, whereas usually limestone tends to form higher land, leaving plenty of space for water to drain down through the rock, without all the passageways becoming flooded.
There is a turlough in the UK, at Pant-y-Llyn, near Llandeilo, in South Wales. It is seasonal in nature, filling in late autumn and emptying again by June.
Last week, in the Burren, we met Clint and Grike. Today I want to introduce you to Kamenitza and Karren.
You will have noticed that although the clints have a relatively level surface overall, if you look in detail they have many little pits and small channels on them.
As you can see here, the depressions collect water. Rainwater is naturally slightly acidic so is able to dissolve the limestone, causing the depressions to gradually get bigger, meaning they collect even more water and so on. The depressions are known as kamenitza.
When rain falls on limestone pavement, some collects in kamenitza, while the rest of the water flows to the edge of the clint and disappears down the grike.
The flowing water will also dissolve the limestone beneath it, so where the water flows most, will be dissolved most, forming a channel. These channels are called karren. They are easiest to spot where they go over the edge of the clint.
Join me next week to look at some of the larger limestone landforms.
Meanwhile, on Saturday, on the Blog About Britain Facebook page, I’ll be starting a new competition based on today’s post!
Characters from a cartoon? Or a movie?
Features of a limestone pavement.
This is a limestone pavement. Clints are the blocks and grikes (or grykes) are the gaps between.
Looks a bit like pavement doesn’t it? For an area of rocks, it has a pretty even surface, but the clints have irregular shapes. Their shapes are controlled by the grikes, which have formed by enlarging what were originally just cracks in the rock.
Rainfall is naturally slightly acidic and acidic water is able to dissolve limestone. When it rains, the water tends to flow down the cracks. The rock at the crack dissolves and the crack gets wider and deeper – so more water can get in, more rock dissolves, crack gets even bigger etc. At some point you can’t call it a crack any more – it’s a grike!
With a rock that dissolves, you don’t get much soil, so the clints remain bare, but plants do grow in the grikes.
The plants tend to prevent you seeing how deep the grikes actually are so, if you take a walk on limestone pavement, I recommend clint hopping! Tread carefully.
County Clare, Ireland has some awesome landscapes. Last week we were at the Cliffs of Moher on the west coast…
…but further inland is the moon-like landscape of The Burren.
From a distance the bare rock looks barren, but up close, you can see that is not the case.
There is an abundance of wildflowers, including many types of orchid…
…while the gaps between the slabs of rock provide a sheltered damp environment suited to mosses and ferns.
In fact 70% of Ireland’s native plant species can be found in The Burren, with the unique environment providing conditions for Arctic, Alpine and Mediterranean species all within the area. And so many different plants means many different animals can thrive too, particularly butterflies.
The area is within the Geopark and is also a National Park. Careful management conserves the landscape but at the same time encourages visitors, so that local businesses benefit from tourism. Money from the tourist industry can be used for conservation. Local people can make money by providing places to stay and entertainment. Tourists like to experience the local culture which helps to keep traditions alive. This is ecotourism.
The people who live in The Burren make the landscape what it is. The tree cutting activities of early settlers, causing soil to be lost, was at least in part responsible for creating the bare rock look.
And it is human activity that maintains the landscape today. The farming practice of winterage involves allowing cattle and sheep to graze the rocky landscape through the winter. This ensures that The Burren doesn’t become overrun with bushy scrub and, by removing the animals again in the spring, the wildflowers don’t get eaten.
Join me again next Wednesday for a more detailed look at the features of this intriguing landscape.
So I left you last Wednesday with a view of some cliffs.
Pretty ordinary cliffs you may be thinking, but let me give you a different perspective.
This is O’Brien’s Tower, built as a viewing point in 1835. Use the people to give you an idea of the height of the tower.
Now use the tower to give you an idea of the height of the cliffs.
These are the Cliffs of Moher. They are 214 metres at the highest point and stretch along 5 miles of County Clare’s Atlantic coastline.
Not surprisingly this is Ireland’s most visited natural attraction, with nearly a million visitors per year.
An impressive eco-friendly visitor centre has been built into the hillside to minimize visual impact.
But you can visit the cliffs for free simply by parking elsewhere along the coast and taking a walk along the cliff path.
The Cliffs of Moher are part of a designated Global Geopark. This status helps protect the natural landscape of the area, and the livelihoods of the local people, by encouraging carefully managed tourism. The rest of the Geopark contains County Clare’s other spectacular landform, which we will take a look at next week.
Incidentally if you are thinking that perhaps you have seen these cliffs somewhere before, that may indeed be the case. They have been used in many movies and TV shows. Here’s a link to a clip from the 1987 family friendly (PG) classic The Princess Bride.