Figure 1 - Sand Martin approaches from rear of convoyFigure 2 - Sand Martin passes over second duck in convoy
When I lived in the Midlands of the UK, away from the bussle of London’s controlled airspace, one of my pleasures on an evening was to hire a light aircraft at my local airfield and tootle off for an hour or so practicing maneoveurs and generally enjoying the sunset – all very peaceful.
Except, one evening when I was out tootling above the Cotswolds; like a flash, an RAF Tornado jet whooshed from under me, matching my track but far exceeding my speed, and all uncomfortably close – a disappearing dot before I could blink.
In fact, he was probably a good 500 ft below me and certainly had on-board radar – so nothing actually dangerous going on. (There’s a popular myth – that may be true – that on such occasions the military use light aircraft for practice interception.)
Anyhow, it made an impression on me, and today the memory returned unbidden with these two photographs snapped at the Rick Pond in Hampton Court Park. They show a Sand Martin in a low-level, high speed pass over a convoy of ducklings – as bemused, no doubt, as I was 4000 feet above the Cotswolds (Figs 1 & 2).
Low-flying Sand Martin (Riparia riparia) with Mallards
I’d been trying to catch the Martins’ aerobatic fly-catching with no success, and started snapping the ducks more as a gesture of resigned failure. I only spotted the Martin when I downloaded the flash card.
This type of ‘buzzing’ seems to be in the Sand Martin’s nature. People on the bank get similar treatment – the bird coming from behind, passing within inches of heads, as if honing their own targeting systems.
I’d left the camera in rapid fire mode of 8 fps, so the time interval between the two photographs is known. If we also know the length of a duck, we can calculate the Martin’s speed, in ducks per second – or more tedious conventional units. So:
Assuming SML = 0.3m (Standard Mallard Length)
Time between pictures at 8 f.p.s = 0.125 s
Ducks passed between frames = 5.75 (use the grid to measure; one duck = 2 grid squares)
Meet the new arrivals. At a pool close to where I live in the south of England, I’ve been following the progress of these cygnets since their birth five weeks ago; the picture and the video were taken about a week after hatching.
The same breeding pair has built a nest in the same spot for the last four years: sometimes they get lucky – othertimes it looks like they go through the motions – or maybe the youngsters get dispatched by predators before I see them.
And for sure, it’s not all sweetness and light. Since I shot the video, one of the cygnets has developed a problem with its neck.
Swans , and particularly cygnets in their first year, are vulnerable to a host of threats: from natural predators like herons, crows, magpies and foxes;
to a bunch of man-made hazards including: being shot at, getting caught up with fishing tackle, lead poisoning, being attacked by pet dogs, crashing into electricity pylons, and getting run down by cars. Even well-meaning but misguided feeding can be injurious – mouldy bread is poisonous to swans.
When I visited the brood on 30th May, when the cygnets were about three weeks old, I noticed one of their number struggling to keep its head up. That might be caused by an injury, but it’s also a known symptom of lead poisoning.
Cygnets on 30th May, one is having trouble holding its head upLead fishing sinker weights are banned in the UK
As Doreen Graham of the Scottish Society for the Protection of Animals said in this 2007 BBC report : “Lead poisoning is quite easy to identify in a swan because they cannot lift their heads and their heads are resting on their backs”. There was a particularly bad spate of lead poisoning during the 1960s, although since then, with a ban on lead fishing weights, or sinkers, the Royal Society for the Protection of Birds (RSPB) believes the problem has diminished.
Lead shotgun pellets are the other likely culprit. There are bans or restrictions on the use of lead shot throughout the UK, with detail variations across the devolved constituencies; but there’s always the danger of legacy poisoning from old pellets lying in the reeds or on the pool bed.
All swans rest their heads and necks at times – it’s how they rest and sleep; but this one’s doing it most of the time, standing out from the group:
The other cygnets appear to sense the difference, taking the occasional peck at their handicapped sibling:
While the parents appear indifferent:
Fast forward to 8th June, when the cygnets are a month old, and at first sight there’s an improvement: it’s all heads-up in this convoy. But on closer inspection, number 4 from the left isn’t quite right:
Cygnets on 8th June
and in this pre-roost preening session, there’s clearly still a problem:
As twilight deepens, the female swan, or pen, climbs into the nest, followed by the cygnets:
It’s easy to make up stories, but here a parent appears to attend the neck of one of the cygnets (I can’t confirm it’s ‘the’ cygnet):
And they settle for the night:
For now, the afflicted cygnet appears to be growing at a normal rate and, despite some earlier sniping by siblings, appears to be accepted by the group. I’ll be keeping an eye on this family over the coming weeks and update the blog with any developments.
UPDATE 8 July
Happy ending. Here’s the whole crew on 19th June – 11 days after the pics above. All six cygnets holding their heads up high. I’ve only just got round to updating, but if they’ve got this far they’re probably going to make the distance. Whatever was wrong with the afflicted cygnet seems to have worked itself through/out. (Not that these guys aren’t still in a warzone.)
Q – What did the grape say when an elephant stepped on him?
A – Nothing. He just let out a little wine.
The first alcohol I ever drank was home brewed. I was twelve when the evil liquor – orange and raison wine – was served up by my refreshingly enlightened policeman uncle of all people. We’d visit the house and find these wort-filled vessels in the bathroom, glug-glug-glugging as bubbles of carbon dioxide chugged through little glass airlocks.
Not that I was swilling the stuff in quantity you understand, but what better introduction to the practical application of biochemistry and chemical engineering. Who knows what influence these little episodes have on later life decisions?
Six years later, as an impoverished student at Birmingham University, I was brewing my own 40 pints of barely drinkable delicious Mild Ale (pronounced ‘m + oiled’ in the local dialect). And while I never got into the brewing habit big time, I still on occasion reach for the demijohn and yeast – like recently, prompted by the promise of summer blackberries and the pungent whiff of Thames-side hops.
It’s obvious booze is an educational resource we ignore at our peril; but to consolidate, consider what’s going on in that murky ochre, as it sits in my hall, infusing the carpets and curtains with its fruity ambience. I hope it’s this:
The contents of the bottle are yellow because the blackberries haven’t actually appeared yet, so for now I’m using Chardonnay grape concentrate out of a can. And as that contains fructose from the grapes plus added glucose syrup, and I’m adding sucrose on top of that, both reactions should have kicked off immediately – the whole thing enabled by one of my favourite eukaryotic micro-organisms – Saccharomyces cerevisiae: a wine yeast.
There’s nothing to do now until it ferments out, but I managed to kill 20 minutes using the chemistry and bubble rate data to figure out how things are ticking along. I reckon I’ll produce 511g of alcohol and 488g (273 litres) of CO2, which at the current bubble rate means the fermentation will take 6 days (workings in the end-notes for those interested and assuming I’ve remembered my O-level chem.).
We covered production of ethanol from fermentation at school, but I don’t remember doing any distillation (which is illegal without a license in the UK). Certainly nothing to compare with the alcohol education afforded 1960s American youth courtesy of the fabulous Golden Book of Chemistry Experiments (excerpts below), which covers fermentation with yeast plus the distillation/synthesis of ethanol, methanol, and a bunch of other fun compounds from the ethanol ‘Family Tree’:
I love the helpful precautionary note on chloroform:’THEN SNIFF CAREFULLY’. A complete home schooling if ever there was one:
That’s all really. I’ll update with a report on the finished product, assuming the wrong types of bug and oxygen don’t intervene and vinegarate the show.
One last item though. Yeast is of course also used in baking; the carbon dioxide from fermentation causes dough to rise. So here’s a particularly rigorous explanation of the process from Alton Browne. It’s over my head, but I’m sure the trained biochemists out there will relate. (Quality isn’t up to much either – sorry about that.)
Guessing there’s about 300g of glucose in the concentrate, and I know I’ve added 450g sucrose to 5.5 litres of water. As 1 Mole sucrose (242g) yields 2 Moles glucose/fructose (360g), 450g sucrose will make 669g glucose/fructose. With the 300g in the syrup that rounds up to about 1000g total C6H12O6. 1 Mole of C6H12O6 (180g) makes 2 Moles ethanol (92g) plus 2 Moles carbon dioxide (88), so 1000g should make 511g of alcohol and 488g carbon dioxide. That’s roughly half a kilo of alcohol in 5.5kg water, or, ignoring the density difference, about 10% by volume . These kits supposedly deliver 12%, so the 300g estimate was probably low. The volume of gas produced can be calculated given 1 Mole CO2 (44g) has a volume of 22.4 litres at STP (24.6 at current 25deg C room temp), so our 488g equates to 273 litres of gas having to bubble through the airlock. It’s bubbling at about 1 per second with an estimated bubble volume of half a cm3 ; so I figure at that rate it will take 6 days to ferment out. All of which seems to hang together with what it says on the tin.
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.
Boulder and SnowdonLocation in WalesLocation 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: WikicommonsSubduction 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 leftView 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
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:
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.
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.
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