Tag Archives: llanberis

A Groovy Kind of Rock

Glacier scarred morain rock near Llanberis (Photo:Tim Jones)
Boulder

A Short Vacation

On a winding stretch of the A5 road from North Wales to London – around Betys-y-coed and Llangollen – mountain scenery combined with the challenge of balancing speed, driver satisfaction, and passenger nausea makes the journey almost enjoyable.  On the other hand, the interminably boring alternations of dual-carriageway and roundabouts that follow – between Oswestry and Shrewsbury – are a recipe for brain death.

Except, that is, one day last week, returning prematurely from a weather-killed ‘Welsh Break’, my mind buzzed over two critical questions the whole trip: What would our broken tent cost to fix?  And why did the grooves on that boulder point to the North East?

Well spotted that woman at the back; this is a post where I obsess about a rock.

Snowdon (Photo:Tim Jones)
Boulder and Snowdon
Location relative to Wales
Location in Wales
Location relative to Llanberis

The boulder in question sits about a half mile down the old Rhyd Ddu road outside Llanberis in Snowdonia.  Its top surface is covered with North East-facing parallel grooves.

And that’s puzzling, because it looks like a moraine boulder dropped by a glacier, in an area where – having walked these valleys for years – I always assumed the ice had flowed towards the North West, away from Snowdon.  Seeing as though the scrape marks left by glaciers – which is almost certainly what these are –  align with the direction of glacial flow, something is amiss.

At this point, lest I raise galactic doubt and uncertainty beyond already dangerous levels, as Douglas Adams might say, rest assured this is all sorted – after a fashion but in a reasonably scientific way –  by the end of the post.  I also got a new tent pole: £15 – thanks for asking.

South Sea Wales

The relevant history starts around 400 million years ago with successive phases of volcanism, weathering, and glaciation (plus some folding and other geological processes).  When the oceanic plate of Iapetus undercut the adjacent tectonic plate of Avalonian – all in the Southern Hemisphere back then – the resulting subduction generated enough heat for volcanoes to punch through Avalonia and form the upland region we now call Snowdonia1.

Source: Wikicommons
Subduction Zone (Source:IAN Symbol Libraries)

The ensuing millenia saw wind, rain, and rivers transform the resulting mountain range from Himalayan grandeur to the more modest heights we see today; yet some of the most dramatic re-modelling was reserved for only the last 20,000 years or so.  And it was caused by ice.

20,000 years ago we were at the peak of a major ice-age that buried the whole region under 1.4 km of ice, with just the tops of the highest mountains poking out.  Moving under gravity, glaciers of rock-bearing ice flowed down the river valleys, gouging out the Llanberis, Nant Ffrancon, and other steep-walled passes, cutting through hard volcanic rock in a series of breaches, and scooping out rounded recesses, or cwms (known as corries in Scotland).

Llanberis Pass on the right, Cwm Brwynog to the left
Llanberis Pass on the right, Cwm Brwynog to the left
View down Llanberis Pass from Llanberis (Photo: Tim Jones)
View down Llanberis Pass from Llanberis

Chunks of rock, liberated by repeated melting and expansion of ice, or plucked out by other rocks, joined the glacier and travelled as an abrasive slurry beneath the ice – scoring anything in their path, before being released as ‘moraine’ when the glacier descended to a warmer altitude or the general climate warmed up sufficiently for the ice to melt.

Boulders falling on the surface of the glacier were likewise dumped, sometimes in incongruous isolation, their angular forms undamaged – like this one just off the Snowdon Ranger Path:

Moraine boulder east of Snowdon near Snowdon Ranger Path / Llyn Ffynnon-y-gwas

A Popular Destination

Glacier-scarred morain rock near Llanberis, North Wales. Photo:Tim Jones
Did Darwin or Huxley pause at this one?

No shortage of historical figures are associated with glaciation and its geographical consequences, including: Louis Agassiz, Charles Lyell, Charles Darwin, Alfred Russel-Wallace, John Tyndall and Thomas Henry Huxley.  Agassiz observed glaciers in Switzerland, and in 1840 was the first to suggest similar processes had operated in the upland areas of Britain (an assertion on which he was closely supported by William Buckland and Charles Lyell.)

Charles Darwin knew the region well2:

“I cannot imagine a more instructive and interesting lesson for any one who wishes (as I did) to learn the effects produced by the passage of glaciers, than to ascend a mountain like one of those south of the upper lake of Llanberis, constituted of the same kind of rock and similarly stratified, from top to bottom. The lower portions consist entirely of convex domes or bosses of naked rock generally smoothed, but with their steep faces often deeply scored in nearly horizontal lines, and with their summits occasionally crowned by perched boulders of foreign rock.”

The glacial boulders of North Wales, with their strange grooving, made a particular impression on Alfred Russel Wallace, the co-discover with Charles Darwin of evolution; commenting in his paper Ice Marks in North Wales3:

..it frequently happens that grooves or scratches are made upon the rocks by the hard materials imbedded in the bottom or sides of the glacier. Owing to the enormous weight and slow motion of glaciers, they move with great steadiness, and thus the markings on rock-surfaces are almost straight lines parallel to each other, and show the direction in which the glacier moved.

and:

Nothing is more striking than to trace for the first time over miles of country these mysterious lines, ruled upon the hardest rocks, and always pointing in the same direction.

Suddenly I feel less alone in my fascination.

In his hugely popular textbook on physical geography – Physiography4 – Thomas Huxley describes how glaciers flow over exposed bedrock to produce characteristic Roches Moutonnees formations (sheep-backs), complete with parallel striations:

Roches Moutonnees, Colorado (from Huxley's Physiography, p.162, 1878)

The Mystery Solved?

But back now to the North West / North East question; a closer look at the Ordnance Survey and Google 3D map projections suggests an answer.

For directly to the South West of our boulder is a more local gouging of the hills in the form of Cwm Dwythwch and its attendant lake – Llyn Dwythwch, suggesting the area was subject to local glaciation running perpendicular to the main ice-flow from Snowdon.  Indeed, the feature is discussed in a paper from the 1950s describing the glaciation as a distinct event, separated from the main ice-flows by 10,000 years in the last period of UK glaciation – the ‘Loch Lomond Advance’.   The cwm certainly aligns with our boulder (pink X marks the spot):

Things are even clearer in glorious Google 3D, North at top:

or looking toward Snowdon:

In Late Glacial Cwm Glaciers in Wales5, Brian Seddon references Cwm Dwythwch and 32 other cwms or cirques in the region arguing they developed from snow and ice preferentially deposited on the sun-sheltered North and North Eastern faces of hillsides, assisted by snow-drifting induced by South Westerly prevailing winds (like we have today).  Seddon recorded the moraine fields of 33 such cirques, plotting their altitude(circles) and aspect(radii) to illustrate the dominance of North/North East facing cwms.  He placed the lowest extent of moraines in the Snowdon Group, containing Cwm Dwythwch, at 275 metres, which is above, but not far off, our boulder’s height at 240 metres.  Maybe he didn’t count every individual boulder at the boundary?  That Snowdonia was formed by a mix of ice-cap and localised glaciation is now widely accepted6,7.

Moraine altitude, aspect, direction in Seddon's Snowdon Group' After Seddon (Ref.5)

All of which, in conclusion, suggests our boulder most likely started life as a volcanic outcrop at the top of Cwm Dwthwch, was carried to its present position by a glacier in a secondary period of low temperatures and glaciation around 10,000 years ago, and picked up abrasions as it was overrun or carried in the North Easterly underflow.

All that with three qualifiers: (a) it’s not 100% certain the boulder is not actually an outcrop of bedrock (need to take a closer look next visit!); in which case it’s fair to assume it was simply overrun by the glacier; and (b) it’s possible the boulder was carried down from Snowdon in the first glacial episode and  subsequently overrun by the secondary glacier (again, more research); or even (c) the boulder  was scarred in the first episode and somehow got spun around 90 degrees just to fool us.

Clearly no rest for the rigorous –  or obsessive weekend geographers – it would seem.

p.s. If any seasoned geologists out there want to put me right / out of my misery, please feel free :-).

Basecamp with pre-broken tent

References / Sources

1. Rock Trails, Snowdonia: A Hillwalker’s Guide to the Geology and Scenery. Gannon, Paul. Pesda Press, 2008

2. Notes on the Effects produced by the Ancient Glaciers of Caernarvonshire, and on the Boulders transported by Floating Ice, Charles Darwin, The Edinburgh New Philosophical Journal, 1842, p.362.

3. Ice Marks in North Wales (With a Sketch of Glacial Theories and Controversies) Alfred Russel Wallace, Quarterly Journal of Science, January 1867

4. Physiography: An Introduction to the Study of Nature. T.H.Huxley, Macmillan, 1878, p.162.

5. Late Glacial Cwm Glaciers in Wales. Brian Seddon, Journal of Glaciology, 1957. In International Glaciological Journal, Volume 3, Issue 22 pp.94-96

6. The last glaciers (Loch Lomond Advance) in Snowdonia, North Wales. Gray JM 1982. Geological. Journal 17: 111-133.

7. Allometric development of glacial cirque form: Geological, relief and regional effects on the cirques of Wales, Ian S. Evans, Geomorphology Issues 3-4, 1986

8. The Early History of Glacial Theory in British Geology. Bert Hansen, Journal of Glaciology, Vol 9, No.55, 1970.

Huxley and Tyndall, Ill-Prepared Alpinists ?

It’s many years since that winter weekend I met up with friends in the UK’s Lake District National Park, intent on hiking the slopes of Helvellyn.

Helvellyn(SimonLedingham)Dec2004

Helvellyn (Photo: Simon Ledingham, WikiCommons)

We’d arrived in groups from various locations, and it was during the traditional kitting-up ritual, managed out the back of our respective vehicles, that the full realisation of my ill-preparedness struck home.

Confidence in my sturdy boots and fleece failed to counter the sinking dread I felt as my friends systematically bedecked themselves, NASA pre-flight-ops style, with all the latest snow gear.  The thing was, I simply didn’t own, or had neglected to bring, the mittens, over-trousers, goggles, and miscellaneous species of crampons and ice-axe recommended by the now darkening sky.

Just as well I was in the safe invincibility of my early twenties.

Much better...

So off up the hill went we.  Almost immediately it started snowing – gently at first, with a serious deterioration setting in at 2000 feet; a full-blown blizzard now: horizontal snow, near zero-visibility, heavy reliance on compass etc.

I stood clown-like, my gaiterless cotton trousers stiff as boards, the ice caking and cracking as I lifted my legs through the thick snow.  My fingers and face went numb.  Resplendent in Gortex, my fellow hikers peered out from their hermetic cocoons, reflectorised goggles glinting from deep within wind-cheating hoods.  Proffered spare socks were gratefully accepted and fashioned into makeshift gloves.

Then as the storm blew into near total white-out, we made the only possible decision, irrespective of equipment, and turned around.

Had we pushed on, things could have got nasty.  As it was, we’d still managed something of a walk, and I guess I got what I deserved by way of a sound freezing and lesson learned.  You’ve got the picture.

In Good Company

John Tyndall

This mildy embarrassing tale comes to mind because of research I’ve been doing into the history of botany (and science stuff in general) in Wales.

And as it turns out, I’m not the first to show up for a mountain ascent without the proper kit.  What’s surprising perhaps is that, among scientists of the Victorian age, that honour goes to none other than seasoned Alpinist John Tyndall and ‘Darwin’s Bulldog’ Thomas Huxley for their 1860 ascent of – not Helvellyn this time – but Mount Snowdon in North Wales.

Thomas Huxley

Snowdonia was a major stomping ground for botanists in the 18th and 19th centuries, and by the 19th century, professional guiding had become quite a local industry.

In ‘The Botanists and Guides of Snowdonia’, Dewi Jones describes how mountain guide Robin Hughes first met up with Tyndall and Huxley:

Robin Hughes was 61 when he guided John Tyndall, the famous alpine mountaineer and scientist, up Snowdon from Gorffwysfa (now Pen y Pass) in 1860.  Tyndall, despite his Alpine experience, had arrived in the area on a snowy December day rather ill prepared for a winter assault on Snowdon, but they managed to gain the summit despite having to wade through drifts of soft snow.  Tyndall, with his friend Huxley, had brought no ice axes or gaiters with them.  They bought two rake handles at  a shop in Bethesda, while on their way from Bangor to Capel Curig, and had the local blacksmith fit them with rings and iron spikes.  During the ascent Tyndall complained of numbness in the feet as the result of his boots becoming filled with snow due to the absence of gaiters.

So, with all due credit for the last minute improvisations, one still wonders what they were thinking – especially Tyndall.  With Tyndall aged 40 and Huxley 35 in 1860, it’s not like either man could claim the inexperience of  youth.

View down Llanberis Pass from Llanberis (Photo: Tim Jones)
View down Llanberis Pass from Llanberis (Photo: Tim Jones)

A bit more digging suggests Huxley at least was distracted. The Snowdon trip had been arranged by his wife Nettie, with the help of Tyndall, to relieve the depression he suffered at the recent death of their son, Noel.  That Nettie had soon after given birth to another son only added to Huxley’s confusion (Desmond):

[Hal hardly knew whether] ‘it was pleasure or pain.  The ground has gone from under my feet once & I hardly know how to rest on anything again’

Desmond continues:

Nettie…..conspired with Tyndall to get Hal away.  That meant one thing.  In unprecedented Boxing Day frosts, when the thermometer plummeted to -17 degrees, Busk and Tyndall marched him off to the rareified air of the Welsh mountains, reaching Snowdon on 28th December.  The grandeur of it matched ‘most things Alpine. (Busk is George Busk (TJ)).

On 19th December, Huxley had written to his friend Joseph Hooker that he was:

“…going to do one sensible thing, however, viz. to rush down to Llanberis with Busk between Christmas Day and New Year’s Day and get my lungs full of hill-air for the coming session.(The Huxley Letters.)

Llanberis is the village at the base of Snowdon, and Pen y Pass the highest point in the nearby pass.  There’s a pub there now, and in 1860 an inn, where, according to Tyndall, Hughes fueled up with whisky before the trip, [and Huxley doubtless topped off his brandy flask] (Tyndall).

Snowdon Summit - in better weather (Photo:Tim Jones)
Crib Goch, Snowdon (Photo:Tim Jones)
Crib Goch, Snowdon (Photo:Tim Jones)
Snowdon Summit
Snowdon summit. No train or cafe in Tyndall's day

Fifteen years later, writing his book Hours of Exercise in the Alps, Tyndall’s torment on Snowdon was fresh in his mind:

“I had no gaiters, and my boots were incessantly filled with snow.  My own heat sufficed for a time to melt the snow; but this clearly could not go on for ever.  My left heel first became numbed and painful; and this increased till both feet were in great distress.  I sought relief by quitting the track and trying to get along the impending shingle to the right.  The high ridges afforded me some relief, but they were separated by couloirs in which the snow had accumulated, and through which I sometimes floundered waist-deep.  The pain at length became unbearable; I sat down, took off my boots and emptied them; put them on again; tied Huxley’s pocket handkerchief round one ankle; and my own round the other, and went forward once more.  It was a great improvement – the pain vanished and did not return.”

And that’s pretty much the story.  Maybe it’s because I know the territory so well, or just that I’m a big fan of both these guys; but I love the imagery of Huxley and Tyndall spilling out of Pen y Pass with their half-cut guide, then trogging up Snowdon with their frozen feet and rake handles.

Anyway, all this staring at a computer screen is unhealthy; I’m off out.

Now where did I put  those gloves……

Sources

Jones, Dewi.  The Botanists and Guides of Snowdonia. Pub. Gwasg Carreg Gwalch (Jun 1996), ISBN-10: 0863813836, ISBN-13: 978-0863813832

Tyndall, J. Hours of Exercise in the Alps. Pub. Appleton and Company 1875 (Tyndall originally described his exploits in the Saturday Review 6 Jan 1861 as ‘The Ascent of Snowdon in Winter‘, but clearly felt the tale was worth re-telling in his Alpine book)

Desmond, Adrian. Huxley The Devil’s Disciple. Pub. MIchael Joseph 1994. pp 289-290.

Jones, G.Lindsay. The Capel Curig Footpaths up Snowdon, A Brief History (link to pdf at http://www.snowdonia-society.org.uk)

The Huxley File (Charles Blinderman) at Clark University  http://aleph0.clarku.edu/huxley/

Clark, R.W. The Huxleys. Pub. Heinemann, 1968. P64

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