A rocky diversion

It is still cold, and because all the May colour has been wiped out by frost, I don’t have any pretty photographs of flowers. So this is a post about rocks. Do gardeners need to know geology? Probably not, although being curious about your soil – where it comes from, what lies underneath it, what minerals it holds, does help when it comes to avoiding expensive mistakes.This geological  map of East Central Scotland (source here – an interesting booklet) shows that I live in an interesting area as far as rocks are concerned. The red bits are volcanic, the pink is Devonian red sandstone, and the grey, dark green and light green are carboniferous rocks containing coal seams, oil shales, and not a lot, respectively.

But as a gardener, what affects me most is the last ice age – about 15,000 years ago. The blue arrows on the map show the direction the glaciers travelled in, but also the course of the water that poured over the land when the ice started to melt. Now, here’s a look at my humble burn, a little upstream of my gardenYou can see how the valley was carved out by a much bigger river than the little burn that runs through it today. And that river of meltwater created the banks and slopes in what is now my garden. Maybe it looked something like this Icelandic river (although there would have been no humans with outstretched arms)The river, and the glaciers before the river, left behind the yellow clay in which I try to grow things. But underneath the clay – sometimes exposed where the ancient river has washed most of the clay away, are older rocks – sandstones laid down when central Scotland was a shallow sea.At the back of the pond, where that ancient river carved a bend, I’ve dug out the covering of clay. I’ve always wanted a cliff face – and this is the nearest I’m going to get.  But the layers of sandstone aren’t consistent. Conditions in that ancient sea must have changed quite often, and between the beds of sandstone, there are layers of mudstone – little more than compressed clay. This wears away easily, leaving the sandstone blocks unstable:Of course, once humans arrived on the scene and needed to build mills or dams, these loose sandstone blocks were a godsend:And in digging them out to build the mill, they created my pond:Now and again I find fragmentary fossils in the clay – ripped from carboniferous rock by the glaciers and dumped in my garden. They would appear to be stigmaria – roots of a club-moss which flourished in central Scotland about 350 million years ago. Its modern descendant, the horse-tail (equisetum) infests the garden today – there’s continuity for you!


22 thoughts on “A rocky diversion

  1. Awesome post Andrew! That pic of your pond is just lovely. Sometimes your garden makes me feel all wistful – streams and trees and moss are some of my favourite things.

  2. I like the pond very much. And any huge chunks of sandstone rock may be delivered directly to my garden whenever you truly cannot endure their mossy presence any longer– I will even send you one hummingbird in exchange.

    Have the hedgehogs awoken?

  3. You certainly are gardening at the edge, Mr K. Glacial features always fascinate me; hanging and U-shaped valleys, arrettes and erratics – it’s always a challenge to imagine a huge slap of ice sitting on top of Cumbria or the Highlands. Though there is melt-water evidence here in the South Downs too; river valleys where there are no rivers for instance. I have a small amount of horsetail at the Priory but luckily confined to one small area – I think the roots can be metres deep! I wish you a flowery June. Dave

  4. I think I read somewhere that the ice was 1500 metres thick – that’s a lot of water to get rid of. Horsetail is a truly horrible weed, but a remarkable plant. I must write something about it.

  5. So it’s Andrew your real name. Beware: I’m starting to put pieces together! (unless Libby left her comment on the wrong blog…)

    I love your pond, why you never posted a wide picture of it before? It looks like a place you can refugee…
    That fossil of yours looks like a portion of steamed salmon to me. Maybe a very ancient one…

    • Way to go Alberto! When I first found one of those fossils, I did hope it would be a fish or an interesting dinosaur. But it’s just a very common plant, even though it looks like salmon.

  6. Aha, Andrew. You’re a dark horse.
    I suspect that we have a lot of the red sandstone in Angus. Not only is our house built of it but many of the fields are a rich red colour. Montrose however is built on sand. Give me the dark peaty soil of Orkney anytime.

  7. A fascinating post and an incredible photo of Iceland. I’ve always wanted to go there. The landscape looks stunning but so too does the countryside where you live. How amazing to have fossils in your garden. And your pond is stunning. I sympathise with you about the weather. It has actually stopped raining here in Wales and we’ve had a fairly dry week but it still isn’t warm although warmer than where you are. Hopefully things will get better soon I need to plant out my french beans!!!

    • I’m afraid I stole the picture of the Iceland river from Google (but they stole one of mine). Never been myself – though I would like to. I’m sure you would find some fossils if you dug deep enough….

  8. Very interesting post, didn’t know our Devonian sandstone reached all the way up to you! All the stones in our garden are very round and smooth, worn by glaciers and then dumped when there was a huge river going all the way up to York apparently. Hope the weather soon improves for you and your plants!

    • Hi Pauline; The Devonian goes further north than me. Janet (planticrunotes) in Montrose lives right amongst it, the lucky girl. I’ve always wanted to live on Devonian – but no such luck here.

  9. Another excellent read – I love geology and their effect on landscapes and soils – much to the horror of the family. I’m sorry there’s nae pretty flowers down where you are either. I went wayward sooth for a while and on return the winds had torn the primula’s heads off. I’m not a fan of this season so far. Geology however – far more interesting and reliable. The geogical maps of shetland and orkney are amazing – if the weather continues in its current fashion – look them up – very amazing to see how the land moved and the different types of geology underfoot.

    • And Orkney has that wonderful flat-bedded stone – no wonder your dry-stane dykes are so easily built! I read somewhere that all Edinburgh pavements are made from Caithness and Orkney slabs – must have cost a bit to get them south. You are right – when the seasons fail, we can rely on the rocks.

  10. Brilliant post, thank you, and fascinating to see where your gorgeous stream came from. Totally flat here in North Wilts (flood plain – ditch at the bottom of the garden we like to think is the real source of the Thames) but in the space of a warm week the apple blossom has been and gone and we’re knee deep in all shades of mauve pink and blue from self-seeded aquilegia. What a weird year.

      • Oh, mine is heavy grey clay, overlaid on some of the gravel that is extracted nearby. It means a narrow weather window between the soil being too cold and wet to work / rock hard. Been adding compost and organic matter etc to it for years! On the other hand, we never get a hosepipe ban, and I have a clay-lined pond that never dries out. After a few days’ sun, it all looks lush and, dare I say it, colourful. Peonies love it, irises don’t. Delighted to have found your brilliant blog.

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