Limestone Pavement, The Burren
A stunning and unusual landscape, the Burren in western Ireland is a striking subject for an image, full of shapes and patterns that you don’t often find in nature. This picture is from a place called Sheshymore, where the character of the limestone has allowed striking geometric, almost square lines to develop. I was there in my undergraduate days on a fieldtrip, looking at a range of physical features all over the Burren, and this was one of the most powerful places we visited. Another was the Cliffs of Moher a way to the south, but the photos weren’t much good -I was still working with my old compact at this time.
Like any landscape, what you see here is the result of thousands of years of geomorphological agents, millions if you include how the rock itself was formed and shaped. We’re talking about the combination of ice, water and wind, with water the most important in this instance, because in its natural form (rainwater) is slightly acidic and therefore able not only to erode, but also dissolve limestone. For any chemists out there, it’s a carbonation reaction, with carbonic acid (rain + carbon dioxide) reacting with the calcium carbonate of the limestone to create calcium bicarbonate, which renders the normally-hard rock soluble. (This solution process of course leads to stalactites and stalagmites in caves, which form when the gas content of the air changes and the calcium carbonate is precipitated.)
Before the last ice age, the exposed bedrock you see here was probably covered with a thin layer of organic soil, which would have taken thousands of years to form. (That is to say the soil would have been made up of predominantly organic matter, as the limestone dissolves so quickly in rainwater that very little is then incorporated into the bottom layers of soil and subsequently mixed through it.) Under the soil, more CO2 is present, and so dissolution is quite rapid, with water finding its way into any weaknesses within the grain of the rock, working through gaps between crystals or granules, until eventually channels form, then underground rivers, forming caves, all the while the water working away at the rock, dissolving the surface of the channels further, creating beautiful scalloped edges (see there picture in my site’s background for some lovely scalloping!). Then the ice age comes along and glaciers strip away those layers of soil, allowing meltwater to get into those cracks, and because it’s cold the carbonation process is even more effective (partial pressure of CO2 being higher in cold temperatures), plus you get things like freeze-thaw working away at the rock too. When the ice is gone, all you are left with is a lot of bare rock, with occasional piles of moraine, so there’s very little for plants to grow in, only wind-blown sediments called loess which settles in the cracks. That wind would have helped to remove any overlying glacial sediment that hadn’t consolidated -it’s quite exposed to winds coming off the Atlantic in this part of Ireland. Without plants, there’s very little soil development, so it’s a vicious circle, and that rock stays exposed for ages, so that when man comes along there’s still not much there. This must have looked very strange to nomadic hunter-gatherers, used to the wild woods, crawling with wolves. Therefore this place gained a special meaning to them, and as a result there’s prehistoric settlements and archaeology all over this area, such as the Poulnabrone Portal Dolmen. Their activity, and human activity since then (well mostly sheep actually), have kept the bedrock exposed, which would have otherwise have eventually disappeared under slowly developing soil and scrubby woodland, in fact mankind probably stripped away a bit of soil too. So what we see today is limestone pavement, with lush vegetation growing in the cracks (known as grykes, at least in the UK), and bare rock plinths in between (called clints). (By the way, the Burren is known for the vast array of wildflowers that grow in the grykes and on its thin soils.) It’s a landscape which is unusual in this part of the world, and so has a great deal of legal protection in conservation terms -not least because limestone is such a sought-after rock for gardens, agriculture and the construction industry. It’s also a landscape which we don’t fully understand: there are some things that don’t quite add up, like calcifuges (lime-intolerant) plants like heather growing in limestone country.
At Sheshymore, the combination of the granular construction of the rock and the gentle gradient of the land surface permitted very even solution, with the water seemingly following great long faults through the rock, stretching off into the distance, cut at almost at right angles (I think this is to do with cleavage in the calcium carbonate) with surprising regularity, nearly parallel. It’s really quite unique to have such regularity -next week I’ll show probably you some welsh pavement, which looks nothing like this! I think this creates an interesting sense of perspective in this picture, which is why I like it so much, that and the space created by having so little going on in the foreground, giving it that wild feel. Oh, and the sky too -there were really big skies out there!
Prints are available to buy -I would go a for a nice big one, like an A3 to make the most of this picture, but other standard sizes would work well too.
All images © Stephen Tyrrell, Mountains, Wild Places & Water, 2013. All rights reserved.