Walking through the (ice) ages

Devil's Point, Cairngorms, showing its form as a glacier-truncated spur

The Devil’s…ahem…Point, chopped off in its prime. But how far did it extend?

How far did the Devil’s Point stretch?

It’s an odd question, but one that occurred to me one day as I sat on the side of Ben MacDui looking across Glen Dee at the rocky face of Bod an Deamhain, chopped off almost cleanly by the irresistible force of a glacier, where once it must have continued eastwards to… Where?

An instinct to symmetry would suggest it stretching out to link with Carn a Mhaim. Even if the glacier had shaved rather than bulldozed, it must have reached a good way across the current glen. Of course you could argue that it may well have. There needn’t have been a massive hollow behind it: perhaps the glacier was so powerful it trenched out the whole glen in a oner. But then what about Coire Odhar, whose position and shape surely argues for its existence prior to the glacier which gouged out the Dee? It seems a classic hanging corrie after all.

Map of Cairngorms showing Devil's Point and Glen DeeYou can ponder this while looking at the map, but how much more powerful a mind venture it is when you sit on the hillside (even in the snow) and try to visualise the mountains as they were, the all-enveloping icefields, the valley-forming glaciers and the smaller corrie glaciers, the plucking of bedrock, the tumbling of whole mountainsides, the bulldozing of debris, the glacial dams and lakes, the gradual and sudden changes effected by water, by freeze-thaw cycles. Add the massive timescales and the mystery of what sequence it all happened in and you have endless source of contemplation.

I’ll come clean before you’re troubled to read any further under false expectations: I don’t know how far towards Carn a Mhaim the Devil’s Point extended; I don’t even know if there’s anyone who does know. There’s a lot written about geology and the hills, about glaciology and geomorphology, but it makes my brain hurt and I retain only tantalising fragments. What I would dearly love is for someone to make one of those computer animations which shows the sequence of the Cairngorms’ formation and evolution through geological upheaval and multiple ice ages. I doubt such a thing is possible, but I crave it.

But even those tantalising traces we are left with – those indications of what must or might have been – provide fuel for wonder. In solitary wanderings I can find myself stopped in long reveries, emerging perhaps none the wiser but much the richer in awe and depth of appreciation of these mountains I love.

And even beyond the obvious glens and corries there’s a lot to see: so many features which hint at the deep history of these hills and, even without full comprehension, add to understanding and to the pleasure of being there.

I’ve read a thesis which talks of a glacial lake in what’s now the Corrour Bothy stretch of Glen Dee, dammed in between ice flowing from the Garbh Choire in the north and from Glen Geusachan in the south. Imagine such a thing!

Maybe easier to visualise is the great loch that must once have occupied Glen Derry. The area referred to as the Derry Dam refers to two dams – one historic and dating back to the logging days of the 1800s, and the other far into prehistory when a glacier bulldozed a great rampart of sand and rock which is still there and which held back a lake whose extent can still be seen in the large flat area of the glen.

Glen Derry, Cairngorms, showing flat glen floor once home to a great loch

Glen Derry. It’s no stretch of the imagination at all to see a great loch where the grassy floor of the glen now stretches

The lake eventually drained when its outflow wore a way down through the body of the dam – the course taken yet by the Derry Burn. Indeed, when Sandy Davidson created his own dam there in the 1800s he was just blocking the breach in the glacial dam and recreating a tiny fraction of the original lake.

But there’s another lake whose traces can be seen in Glen Derry, reaching down into Glen Lui and up into Glen Luibeg. If you stand on the higher part of the path up the east side of Glen Derry you can see a faint line in the hillside of Carn Crom – a horizontal fault-like line which runs southward out of Coire na Saobhaidh. Look further and you can see a continuation of the line, faint but discernible, along the side of Sgor Dubh, across on the other side of Glen Lui. And if you head round the corner past the Derry Flats and into Glen Luibeg, you can look up and see the same line picked out along the slopes of Coire Craobh an Oir.

Carn Crom, Cairngorms, showing faint trace of glacial loch shore.

Not very clear in this photo, but you can just about pick out the ancient shoreline on the side of Carn Crom, cutting through the lower of the two sandy patches on the left and continuing faintly through the start of the broken rock. Much easier to see in person.

I’d always assumed this to just some quirk of geology, but the same thesis (by Matthew Richard Standell at Loughborough University in 2014) says these lines in the landscape are relic of the shoreline of an ancient lake far more vast than that once behind the Derry Dam. Indeed, while trying in awe to visualise this mega-loch, consider that the pass of Clais Fhearnaig, between Glen Lui and Glen Quoich, was created as the outflow of this loch which once drained into Glen Quoich rather than down the present course of Glen Lui, which would have been blocked still with ice.

How long ago? Well long enough to make your brain hurt, because there are other traces of glaciers past which to my small mind at least must have come much later – in fact Glen Lui (as with the other glens) is full of them.

There are the two ‘fairy mounds’ in the flats above the Black Bridge, conical gravel moraines created I think from debris carried down through the ice by a moulin – a stream running down and into the glacier. A similar but much larger complex of mounds can be seen almost blocking the glen just west of Luibeg Cottage, as well as more moraine ridges running down the eastern side of Coire Craobh an Oir.

'Fairy mound' - glacial moraine in Glen Lui, Cairngorms

One of the ‘fairy mounds’ in Glen Lui

Then there are the terminal moraines. How many people walking up the track to Derry Lodge are aware of walking through at least two of these? Blithely walking through what was once a bulldozed ridge of rubble at the nose of a glacier, but conscious only of two kinks in the road as it negotiates raised, sandy ridges. And how many sitting outside Bob Scott’s Bothy realise when they look across the river they’re looking at a cross section through another terminal moraine, and sitting where once a great snout of glacier would have been tumbling lumps of stone and ice on their heads?

Terminal moraine in Glen Lui, Cairngorms

Again, easier to see in real life than in the photo, but the curved ridge just above the pale grass is what’s left of a terminal moraine. Once this would have marked the nose of a glacier filling the glen

All these traces and so many more of events so deep in the past, which have shaped the landscape – and the ecology – we see today, add to the richness of the picture we have of time and place in the Cairngorms. And though it all may have happened tens of thousands or even millions of years ago, there are always reminders that there is no switch between  ‘then’ and ‘now’ in the mountains, but a continuum, with changes started deep in the past still in motion; barely discernible at times, yet sometimes sudden. Visit the deepest recesses of the Garbh Choire, where, with few exceptions, snows still lie year round and you see and feel ground still unstable, with shifting screes at the foot of cliffs and every year fresh scree added from the rocks above. Or walk the granite blockfields and pancaked outcrops of the MacDui plateau and see the progression of splits and laminations as the bedrock even yet is prised and forced apart by the freeze and thaw of water. Walk the glens and corries and see where modern floods have caused slope failures in what seemed stable hillsides, weaknesses built-in in the distant past suddenly revealed.

Rock exposure on Ben MacDui, Cairngorms

Bedrock still fragmenting and spilling down the hillside on Ben MacDui

I stood once on snow, enveloped in cloud, in the innermost bowl of the remote Garbh Choire Mor and, effectively blind, listened as the spring thaw brought rocks clicking and cracking down the cliffs, noises echoing in a corrie that suddenly felt so claustrophobic, that was still, I realised, being hollowed out from the mass of the mountain.

It’s times like that which make you realise that, no matter how much geologists and geomorphologists talk of the distant past, the mountains are still making and telling their stories today – if only we could understand better what their signs are saying.

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16 Responses to Walking through the (ice) ages

  1. piper says:

    Very interesting stuff Neil .

  2. Excellent, thanks and most of this new to me, cheers Neil. Love the loch shoreline feature.

  3. DAVID JOHNSTONE says:

    Neil You are a bad man Sitting in Rome replying to your excellent post For some reason my phone will not let my do the usual chap on the post. I was fully aware of most of what you have written here but not really joined it all up. Hope to see you in June

    David

    Sent from my iPhone

    >

  4. Doug Palmer says:

    Great read Neil had hoped to meet you in person at Bobs this Easter but poor weather and lack of sleep drove me home. May have met in the distant past but not certain. Have printed this latest gem of wisdom off to leave a copy at the Bothy in the pennines that I look after. Old McRed will enjoy the reading of it.

  5. Donald Sinclair says:

    One of the best posts I’ve read. Great writing.
    Regards
    Donald

  6. Ah – so the Devil’s been circumcised! 😉 (sorry couldn’t resist that comparison)…

    All I know is that, whatever the glaciers got up to in the ice age, it made some of my favourite walking country 🙂

  7. Andy Mayhew says:

    I love looking at the map (reading it in a proper sense) and speculating on how drainage patterns were changed by the glaciers. For example, did the Guesachan burn and the upper Dee once flow east to Glen Luibeg? I suspect so ….. Before the glaciers carved out a new route to the south.

  8. RAnderson says:

    ‘morning Neil,
    You badly need a field class in glaciology that I am happy to offer any time.
    The answer to your first question re the Deil’s point has to do with the Truncated Spurs that successive glaciers will have created by bulldozing the Interlocking Spurs that pre-dated the glacial periods that we commonly refer to as the Ice Age.
    Post glacial temporary water features and depositional features such as Eskers, Kames and Drumlins demand quite a lot more imagination (in the absence of a time machine to nip back and check out what/when/where and the sequence which they happened) but I absolutely share your fascination while sitting taking in yet another version of the elements of the views that make up our special hills. We humans mostly think in ridiculously short time scales.
    As a Geography teacher it is a lifelong professional frustration trying to engage students at school with such things. They spend far too long in bus shelters exercising their thumbs, texting and swiping, to make engaging with such thoughts in a class room interesting.
    As ever, “so many hills, so few days”……
    Richard

    • Cheers Richard. You sort of lost me at interlocking spurs, but I think a glaciologist would make a fascinating hill companion. There’s always something sneaks into the grey cells before the eyes glaze over.

  9. Bill says:

    Neil, absolutely fascinating and beautifully written – no doubt facilitated by an Aitken’s roll or-two and cup-of-tea!

  10. Angus Robson says:

    I like this article a lot. Many a time I’ve sat on the edge of Ben MacDhui looking across to the Garbh Coire or by the Feith Bhuide overlooking Loch Avon and wondered in awe at the glaciation processes that carved out the Cairngorms. Every time I venture into the mountains I am filled with wonder at their creation and eventual destruction. I have a booklet titled “Cairngorms, A Landscape Fashioned By Geology”, which takes a look at the glaciation and post glaciation processes of much of the Central Cairngorms. According to the info on the back, a copy can be obtained from The Publications Section of Scottish Natural Heritage. Much of the information is credited to the British Geological Survey in Edinburgh.

  11. Stuart Anderson says:

    Fascinating read for someone who recently wandered thru the Larig Ghru, passing Bob Scotts en route to Braemar on the TGO Challenge………really must lift my eyes and have a right good look at my surroundings next time :~)
    Stuart

  12. Kenny Ferguson says:

    Fascinating Neil. i really enjoyed this post. I knew i should have attended Mr. Kennedys’ Geography class instead of bunking off school to go fishing in the Lothrie burn.

    • I seem to remember school geography being more interested in how many sheep there were in Australia than in how our mountains and glens were formed. But yeah, I wish I had the sort of brain that could take all that in – and keep it there!

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