The Oak at the Gate of the Dead

Posted on May 8, 2013 by Ash

The Oak at the Gate of the Dead (a.k.a. the Crogen Oak).

Once I’d seen all there was to see of the uprooted Pontfadog Oak, I got back in the car and headed for home. But only a couple of miles down the road I pulled over to visit two more giant oaks: the Oak at the Gate of the Dead and the Duelling Oak. Both of these veterans grow within a stone’s throw of one another (and right close to the Wales-England border), beside the road linking Pontfadog with Chirk.

The massive girth of the Oak at the Gate of the Dead.

The Oak at the Gate of the Dead (Derwen Adwy’r Meirwon in Welsh) is famous, at least locally, for growing at the Pass of the Graves (Adwy’r Beddau). This is thought to be the place where in 1165, during the Battle of Crogen, the forces of Henry II of England were ambushed by the Welsh under Owain Gwynedd. The battle is described in Thomas Pennant’s A Tour in Wales, published in 1778:

Offa’s ditch [Offa’s Dyke]… decends to the Ceiriog, and thence to Glyn, where there is a large breach, supposed to be the place of interment of the English who fell in the battle of Crogen, hereafter to be mentioned…

In this deep valley [of Ceiriog], which winds along the foot of the vast Berwyn mountains, was a bloody conflict between part of the forces of Henry II, and the Welsh, in 1165. Henry had determined once more to attempt the subjection of Wales, and to revenge the ravages carried through the borders by its gallant prince Owen Gwynedd; for that end, he assembled a vast army at Oswestry. Owen, on the contrary, collected all his chieftains, with their dependents, at Corwen. The king, hearing that his antagonist was so near, resolved to bring the matter to a speedy decision. He marched towards him; and in this valley, finding himself intangled in impenetrable woods, and recollecting his ill-fortune among the forests of Eula, directed his vanguard to make the passage clear, by cutting down the trees, in order to secure himself from ambuscade. The pikemen, and flower of his army, were posted to cover the workmen. The spirit of the common soldiers of the Welsh army grew indignant at this attempt; and, without the knowledge of their officers, fell with unspeakable fury on these troops. The contest was violent; numbers of brave men perished; in the end, the Welsh retired to Corwen. Henry gained the summit of the Berwyn; but was so distressed by dreadful rains, and by the activity and prudence of Owen, who cut him off from all supplies, that he was obliged to return ingloriously, with great loss of men and equipage.

This conflict is sometimes called the battle of Corwen; but with more propriety that of Crogen: for it happened beneath Castelh Crogen, the present Chirk castle; and the place is still called Adey’r Beddau, or the pass of the graves of the men who were slain here.

Pennant makes no mention of a large oak. Can we therefore infer, perhaps, that 250 years ago the Oak at the Gate of the Dead wasn’t significantly large or famous? ‘According to legend’, before the Battle of Crogen Owain Gwynedd rallied his troops beneath none other than the Pontfadog Oak… Would that have been at all a significant tree 850 years ago? Almost certainly not, I think it’s safe to say.

According to its page on the Woodland Trust’s Ancient Tree Hunt site, the Oak at the Gate of the Dead is a pedunculate or English oak (Quercus robur) that has a girth of 9.6 m (31 ft 6 in) at a height of 1.5 m – which equates to a dbh of 3.1 m (10 ft 2 in). By comparison, the Pontfadog Oak was listed by the Tree Register as having a dbh in 1999 of 409 cm (13 ft 5 in): a whole metre thicker! That isn’t to claim that the Oak at the Gate of the Dead is a small tree though – far from it.

Unfortunately the Oak at the Gate of the Dead split in half in January 2010. This YouTube video, by Rob McBride, tree hunter, records a visit he made to the tree just days before its collapse. In this Flickr collection, he has a photo showing the tree pre-collapse in October 2009 and another from December 2006 in which the large split in the trunk is obvious – a clear signal of impending collapse. It goes without saying that I wish I could have seen the tree in person while it was still intact.

Small Ganoderma bracket growing on the Oak at the Gate of the Dead.

Ganoderma is a wood-decay fungus causing a white rot in the roots and the stem bases of trees. Affected wood is turned soft, spongy and fibrous. It commonly leads to windthrow as afflicted trees are no longer effectively anchored into the ground. Another of Rob McBride’s photographs shows what look to be Fistulina hepatica (beefsteak fungus) brackets on the Oak at the Gate of the Dead. This fungus will also decay the base of the stem, but it causes a brown rot where the affected wood is turned brittle.

Another small Ganoderma bracket on the Oak at the Gate of the Dead.

An article at treehugger.com on the Oak at the Gate of the Dead - riddled with inaccuracies, such as that the Oak died in 2010 and that it is thought to date back to the reign of King Egbert in 802 “when Wales beat back Henry the Second” (the Battle of Crogen was in 1165) - repeats an incorrect theory put forward in this BBC News article from 2010 as to why the tree split in half. Said local historian Mark Williams:

“It seems to be a victim of the very cold weather. The tree is on marshy ground in a basin with a stream running down nearby. With the stream overflowing because of melting snow, the water must have settled around the trunk and it looks as if this has caused it to split.”

Actually the cold probably had nothing to do with the split, and I really doubt that the wee stream nearby played any part whatsoever. In all probability the Oak split in two simply because it was a very big, very old tree with a much decayed, hollow stem that was pulled apart by its long and extremely heavy limbs acting as levers, each limb pulling downwards and outwards in different directions. The tree had plainly reached a point where the trunk was no longer structurally sound enough to hold together under these forces; a strong wind could have finished it off sooner, or a heavy covering of snow, or some other loading factor. What could have prevented the split? By supporting the larger limbs with props, the forces pulling apart the stem could have been greatly reduced and the Oak at the Gate of the Dead could potentially have been kept in one piece for many years to come.

I actually met Mark Williams while I was at the Oak, where he was showing a Brummie family around, telling them of the big tree and the Battle of Crogen. He approached me because he’d just seen me at the Pontfadog Oak, where he’d been one of the farmyard group. He was a nice bloke; we talked about the two trees, and he was surprised that I knew about them - especially surprised that I knew the Duelling Oak, whose fame is not on a par with the others. Hey, a good treeblogger does his research before setting off on one of these trips!

Mark mentioned that he’d been on TV before – either to do with the battle or the trees, or both (my memory fails me) – and that he would hopefully be on again soon to get out the message that more needs to be done to protect and preserve our ancient trees.

* * * * *

The Duelling Oak

The Duelling Oak or Duelling Tree.

The Duelling Oak stands perhaps fifty metres away from the Oak at the Gate of the Dead. It is so-called because duels was supposedly fought here, although I’ve been unable to discover any more information than that. According to the Ancient Tree Hunt, its girth at 1.5 m height was 7.3 m (23 ft 11 in) in 2012, giving a dbh of 2.3 m (7 ft 7 in). This makes the Duelling Oak almost a metre narrower than the Oak at the Gate of the Dead, but it is still an impressive veteran tree.

The mossy trunk branches off into several large limbs just above head height, so it is probably an old pollard.

The Duelling Oak, despite its age (and probably having been pollarded many years since), is still a tall tree. It is also supporting a great weight of ivy…

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The fall of the Pontfadog Oak: Britain has lost one of its greatest trees

Posted on April 26, 2013 by Ash

Thursday last week I heard from my father that a great oak had blown down overnight near Wrexham. From the internet I learned it was the Pontfadog Oak that had fallen – Britain’s second-biggest-girthed sessile oak (Quercus petraea). After doing a bit of research and discovering two other named oaks nearby (a story for another day), I decided to pay my respects and get some photographs of the fallen champion. So on Saturday morning I jumped in the car and drove the 100 miles to Wales – hey, if Yorkshire’s greatest lapsed treeblogger can’t do that, then who can?

Arriving in the tiny village of Pontfadog in Wrexham County Borough about midday, I called in to the post office, bought a Tango, and nonchalantly asked the man behind the counter where exactly could one find ‘the old oak’? He was hesitant. I assured him I would seek permission from the landowner before approaching the tree. Still doubtful, he nevertheless spilled the beans: “up the hill by the pub, left at the chapel, then right along the private drive”. After passing the chapel without realising it, I wandered up and down various lanes until my eagley eyes picked out the prostrate behemoth from a distance.

Once I homed in on Cilcochwyn Farm it became apparent I wasn’t the only one who had made the pilgrimage. A small group were gathered in the farmyard with cups of tea discussing the fate of the unfortunate Pontfadog Oak, which lay sprawled before them, its extremities pressing on the farmhouse. A few other people were standing around the oak, some with their cameras out. I addressed a bloke in the farmyard group.
“Is this your farm?”
“It is.”
“Can I take some photographs of the tree please?”
“Of course you can!” The man in the post office needn’t have been so reticent; there was almost a party atmosphere here!

I had only taken a few pictures when an old man asked if I was looking for the other ramblers. “No, I’m here to see the tree,” I replied. “Really?” He seemed pleasantly surprised. “Where have you come from?” “Sheffield,” I said. “Really?” Surprised again (maybe even astounded). “What’s your interest in trees?” he asked. I told him that I’d studied forestry and ecology at university, that I’m an arborist, and that I have a general interest in trees, really old ones in particular. He produced a small notebook and with the aid of a quick sketch explained the theory put to him as to why the tree had fallen over. The tree was splitting in half so an iron band was installed around the trunk to keep the two halves together; but when one half was ready to fall it had no choice but to bring the other half with it. I didn’t think this plausible. More likely, I explained, was that the oak had little left in the way of structural integrity - the inevitable consequence of an exceptionally long life and the work of wood-decay fungi. Yet it still maintained a respectable crown which unfortunately acted as a sail in the wind. Enough wind that night and over it went. Perhaps if the tree had been propped up, like many grand old trees are, then the Pontfadog Oak could have survived last week’s gales and remained standing for many years to come.

A snapped root; the tissue appears to be living albeit with fungal rot present.

Still, I was in for a shock when I saw both the underside of the tree and the soil on which had it stood for centuries. Where were all the roots? For all intents and purposes, there was nothing at all to anchor it to the ground. The biggest roots there, which were really nothing, were completely rotten. There were a couple of small straggly roots that were live wood, but had they really managed to sustain the whole tree? Like I said, the crown was quite respectable, so I was completely baffled by the apparent absence of anything to pull water out of the ground. The only reason the tree remained upright prior to Wednesday night was the sheer bulk of its enormous trunk: simple gravity! When too much wind dragged in its sail (which was still leafless, so not even that effective a sail) the whole tree just rolled over without a fight, exposing a bare patch of undisturbed soil. The Pontfadog Oak really ought to have been artificially supported!

A completely dead and rotten snapped root. This could no longer anchor the tree in the ground.

So what can I tell you about the Pontfadog Oak prior to this catastrophe? Its demise has made the news, where unfortunately certain myths regarding this famed tree have been promulgated as facts. I’ll summarise here under the heading ‘Facts’ a few things that I think are safe to call the truth, followed under the heading ‘Non-facts’ by a few things I believe are doubtful or implausible. ‘Tis a valuable public service I perform…

I spotted this graffiti on a piece of old deadwood: ‘T.L. 1939’

Facts
- In 2007 the director of the Tree Register, David Alderman, measured the girth of the Pontfadog Oak at 1.5 m from the ground as 12.9 m. ¹
- In 2006 the tree was around 11 m tall. ¹
- In 2012 “a group of experts from the Ancient Tree Forum visited the Pontfadog Oak and put together a list of actions that they believed could help conserve it. Although the total cost was only £5,700, these actions were never taken as no funding source was available.” ²
- The tree is referred to by George Borrow in his book Wild Wales, first published in 1862. ³
- It was perhaps the third ‘fattest’ of our two native oaks, Quercus petraea and Quercus robur. ³ The Tree Register considers the Marton Oak in Cheshire to be the fattest, with a diameter of 446 cm, even though it is in a state of collapse with the trunk made up of three separated sections. The Tree Register’s Handbook records the diameter of the Pontfadog Oak as being 409 cm in 1999 “around collapsing parts”. The only other fatter oak listed is one at Great Witley, Worcestershire, which had a diameter of 411 cm at 1 m height in 2007 “under division of three parts”. ⁴
- Rob McBride, tree hunter: “…until about 200 years ago [it] was a tree that was pollarded – with branches and leaves regularly cut to feed animals and build fencing.” This guy was a local and I trust he knows his stuff. ⁵
- The Pontfadog Oak was designated one of fifty Great British Trees in celebration of the Golden Jubilee of Queen Elizabeth II in 2002 “in recognition of its place in the national heritage”. ⁶

Old deadwood colonised by colourful lichens.

Non-facts
- “The 1,200 year old Pontfadog Oak... is said to have grown near Chirk in Wrexham since 802 [AD]…” ² It is next to impossible to date a tree of this size and condition with any accuracy. You can’t count the annual rings – the tree is hollow and very rotten, so the oldest wood no longer exists. You can’t make an estimation based on known growth rates of oak – way too many variables, especially on that time scale and with the likely variations in crown size over time. Arriving at one specific year – 802 – is frankly ridiculous and almost certainly wrong.
- “It is known that the Welsh Prince Owain Gwynedd rallied his army under the tree in 1157, before taking on, and defeating the English King Henry II at the battle of Crogen nearby.” ² How is this ‘known’? Are there contemporary records pinpointing this exact tree? Could this information have been reliably passed down for nearly 900 years? (See the number of lost battle sites in this country.) Would the Pontfadog Oak really have been a large enough tree almost nine centuries ago for a Welsh prince to choose it as his rally point?
- “It was the oldest oak tree in Wales, probably the oldest in Britain and one of the oldest in the world. Although it has been said since it came down the tree was about 1,200 years old I believe it may be even older. I remember there was a millennium project done on it in 2000 and at that time experts suggested it may be even about 1,700 years.” ⁷ 1,700 years old? I really can’t see it.

A burr (or burl) halfway up the trunk.

I wonder what will happen next to this enormous and extraordinarily long-lived tree. I hope at least that the trunk can be preserved in some way; it would be a shame to leave it to rot away in the corner of a field somewhere, or to have it carved up for firewood.

Last week this would have been a bird’s-eye view.

Sources
¹ Sessile oak close to Pontfadog in Gyntraian. Monumental Trees.
² Wales loses its oldest oak tree, the Pontfadog Oak. Woodland Trust.
³ Condolences for Wales’ National Tree. Woodland Matters.
⁴ Johnson, Owen (2011). Champion Trees of Britain and Ireland (The Tree Register Handbook).
⁵ Pontfadog Oak: 1,200-year-old tree toppled by winds. BBC.
⁶ List of Great British Trees. Wikipedia.
⁷ Expert says 1,200-year-old oak tree near Oswestry cannot be saved. Shropshire Star.

The massive, hollow, burred bole of the fallen Pontfadog Oak.

* * * * *

Next post: A visit to the nearby Oak at the Gate of the Dead & the Duelling Oak.

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PSAUS defoliated by lesser willow sawfly (Nematus pavidus) larvae

Posted on July 16, 2012 by Ash

It’s only the middle of July but the PSAUS, a willow (Salix) has already lost most of its leaves…

Nope, autumn hasn’t come early. It has been munched to destruction by these hungry fellas: lesser willow sawfly (Nematus pavidus) larvae.

I recognised them straightaway as sawfly larvae, rather than caterpillars, after the Set A grey alders played host a similar species a few years ago.

This photograph shows a birch sawfly aka hazel sawfly (Croesus septentrionalis) larva on grey alder No. 3 in October 2009...

…and on the same day I took this photograph of an alder sawfly (Eriocampa ovata) larva on grey alder No. 2.

Little wonder the PSAUS has been almost entirely defoliated – there are dozens and dozens of larvae! I’ve decided to leave them to do what they do best, and wait and see whether or not the PSAUS can weather the storm.

In this photo the second-right larva is caught in a classic pose while the furthest-right larva has an injury halfway along its body.

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treeblog update: the Set A Scots pines, the PSAUS, & the Set D(b) beeches (May/June 2012)

Posted on June 13, 2012 by Ash

Get set for the latest update on the development of the two Set A Scots pines, the post-Set A unknown seedling (PSAUS), and the two Set D(b) European beeches! In the intervening two-and-a-half months since the previous Set A update, Scots pine Alpha has produced 2012’s candles, Scots pine Gamma has been struck by pests, and the PSAUS has come fully into leaf. The last Set D(b) update was in October 2011; since then the two beeches have lost their last autumn leaves and regrown a whole new set.

I photographed the Scots pines and the PSAUS on Sunday (Day 1901, or just over five years and two months since I planted the Set A trees as seeds). I photographed the two beeches a fortnight earlier on the 29th of May (Day 972, or two years and eight months since I planted the Set D(b) beeches as nuts).

Behold ye fine Scots pine Alpha with this season’s growth so far strikingly manifested as candles sprouting from the tip of every branch. You may perhaps have noticed a skinny foxglove growing through the tree to the right of the stem; this is a self-set which I do not have the heart to pull up. (The tent in the background was there to dry out, having just got back from walking the Rob Roy Way!)

A close-up view from the candles at the very top of my pine. The candles will get even longer and then sprout needles, transforming into ordinary branches.

A close-up of a branch rosette on the sturdy main stem.

Scots pine Gamma, sadly looking nowhere near as perky as Alpha. The candles are barely grown! Why?

This is why – Gamma is under attack from a pest, perhaps some kind of aphid. The poor tree is infested with these tiny, dark grey insects and they are definitely having an adverse effect.

The PSAUS is looking slender but healthy.

PSAUS detail.

Beech Alpha looks great with its fresh, new leaves!

Beech Beta looks lovely too. I can’t wait to see how these two develop this year!

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treeblog update: the Set C(r) rowans (May 2012)

Posted on May 31, 2012 by Ash

I’ve left it a stupidly long time since the last one, but here’s the latest update on all thirteen Set C(r) rowans (excluding the tricots, which I haven’t shown on treeblog in an even looonger time, but which will make an appearance soon). I took the photos on Tuesday – Day 1113 – just over three years since I planted the rowans as seeds. The last update was in May of last year on Day 720.

There are four ‘U’s, which are the offspring of a tree that grew near Upper Midhope, and nine ‘W’s. which are the offpring of a tree that still grows on Whitwell Moor. On the whole, the Ws are doing far better, but the tallest Set C(r) rowan is a U.

U2 – Tiny. Along with U7, this seedling has the same mildew-type affliction that affected the majority of the Set C(r) rowans last year.

U5 – healthy but tiny.

U7 – tiny and suffering from the mildew-type disease.

U14 – the tallest tree in the set, measuring a whopping 67 cm tall.

W2 – another tall one.

W6 – kind of average.

W7 – I think the the two little branches sprouting from near the base have died.

W11 – another tall one, with a suppressed second stem.

W12 – a little smaller than average.

W15 – pleasing to look at.

W17 – has the leafiest stem.

W18 – kind of average.

W19 – doesn’t look very sturdy, and one tiny branch has a bit of that mildewy stuff, but otherwise looks healthy.

* * * * *

I also measured the heights of all thirteen rowans. They are ranked in descending order in the table below:

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treeblog update: the Set C downy birches (May 2012)

Posted on May 14, 2012 by Ash

Here’s a quick update on the progress of the Set C downy birches. I took the photographs this evening (Day 1160). All twelve trees are looking healthy and they’ve all come nicely into leaf.

No. 1.

No. 2.

No. 4.

No. 5.

No. 10.

No. 14.

No. 15.

No. 21.

No. 22.

No. 23.

No. 25.

No. 27.

I didn’t measure the trees this time around because they’ve not really started this year’s growth yet. To see how they looked in November, and to see a list of all their heights then, check out the last Set C downy birch update.

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A beech at the height of its powers

Posted on April 29, 2012 by Ash

They don’t come much better than this: an enormous beech (Fagus sylvatica) at the top of its game, yet net showing any sign of decline. It is one of a long row of mature beeches running mysteriously through the middle of Spout House Wood in the in delightful Ewden Valley. Who planted them, and when, and why?

In the bottom of the valley More Hall Reservoir is so full it’s overflowing. We’ve had a hell of a lot of rain recently, but the local reservoirs already filled in a short period in the autumn after spending most of last year half empty. It’s been so long since they’ve been properly full that it’s weird seeing them like this. I’d gotten used to seeing More Hall Reservoir as I photographed it in these posts from January and September 2011!

Wood anemone (Anemone nemorosa), an ancient woodland indicator species, in Morehall Reservoir Plantation. I confess I hadn’t a clue what it was until I looked it up. I need to work on my herb ident!

Much of the plantation was clear-felled at the end of 2010 but it has since been replanted. I had a look inside a fair few of the tree guards and they all contained baby hazels (Corylus avellana).

This is one herb I do know: wood sorrel (Oxalis acetosella), another indicator of ancient woodland.

Downy birch (Betula pubescens) catkins. The drooping yellowish catkins are made up of male flowers and will soon be dispensing pollen. The upright green catkins are made up of female flowers, and will dispense seeds later in the year when they too will be hanging downwards.

The view north across Ewden, taken with my back to Spout House Wood. The hand of spring has given the landscape a welcome boost of greenery.

Back to that sublime beech…

A mind-boggling number of branches!

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MacCulloch’s Fossil Tree

Posted on April 15, 2012 by Ash

The Ardmeanach Peninsula with Loch Scridain on the left.

I went on my own up to Mull for a few days at the end of March. On my first full day there I climbed Ben More, 966 metres tall and the island’s only Munro - my seventh. On my third day there I took the ferry across to Iona and visited the ruined nunnery and restored abbey, and the next day I had an eleven-hour drive back to Sheffield. On my second full day on Mull – the 31st of March - I went for a walk to see MacCulloch’s fossil tree.

I left the car at the National Trust car-park just past Tiroran on the Ardmeanach Peninsula and set off west along a Landrover track. It was a beautiful day, warm enough for shorts and t-shirt for the most part. The previous day I’d climbed Ben More in dense fog, relying on map and compass to reach the summit and descending in chilly rain. The day after, on Iona, the weather was miserably overcast and drizzly. But the day I chose to visit the fossil tree was absolutely lovely. Lucky me!

Looking back at the farmhouse at Burg, the last inhabited house on the peninsula and home to the only person I saw on my whole six-hour walk – an old man who stood looking after me once I’d passed by. Today this farmhouse and a small bothy are about all that’s left here, but over fifty people lived at Burg before the Highland clearances in the 1840s. East of Burg, there were also settlements at Culliemore and Salachry, but these too were cleared in the 1800s for sheep-farming. I saw a lot of ruins of small buildings along the track.

This 19th-century monument stands in the centre of a ruined iron age fort – you can see the thick, curved wall in the right of the picture. This “probable D-shaped semibroch or a sub-oval dun” is known as Dun Bhuirg. Archaeological notes are available at the Royal Commission on the Ancient and Historic Monuments of Scotland’s website.

It was also called Castle Dare at one time. A plaque on the other side of the monument, erected by Mr. John Hamilton Turner, reads:

DAISY CHEAPE
ACCIDENTALLY DROWNED IN THIS LOCH
15TH AUGUST 1896
”BELOVED”
”CASTLE DARE” HER FAVOURITE PLACE

Puir wee lassie. According to Walking on the Isle of Mull by Terry Marsh, Daisy’s family owned the Tiroran and Carsaig Estates. She died, aged twelve, when the small boat she was in with her brothers Ronald and Leslie was overtaken by a storm as they sailed to Carsaig. The boat capsized and sank with Daisy caught in the rigging; the boatmen and her brothers survived. Her proper name was Helen Margaret Cheape. [I found this further information here.]

Looking east, back along Loch Scridain.

At one point in my walk, I rounded a corner and was surprised by this sight: two stags (red deer or roe?), a family of feral goats, and a buzzard!

This mad wheel of basaltic cooling columns is in the sea close to MacCulloch’s fossil tree. I have read that this wheel itself was formed by lava cooling around a tree – we’re seeing a horizontal cross-section of the tree and the surrounding lava, whereas MacCulloch’s tree is seen in vertical cross-section. It seemed to me that this wheel was the terrifying maw of a gigantic kraken.

The wheel and a collection of more regular vertical cooling columns.

Even closer to MacCulloch’s fossil tree, the path takes you to a rusty old ladder that leads down onto this stony beach. The ladder looked very old and seriously corroded, so it was an act of faith to climb down it. An even older and rustier ladder still hangs on beside it!

And so, finally, to MacCulloch’s fossil tree – after a four hour walk which I reduced to two hours on the return leg simply by taking next to no photographs.

The tree was probably swallowed up by a lava flow from Ben More, then an active volcano, between fifty and sixty million years ago during the Paleogene period. Although the fossil today is mainly just an imprint, at the time its discovery by John MacCulloch in 1819 the imprint was lined with a two-inch deep layer of charcoal which has since been removed by souvenir hunters and unscrupulous geologists. The remains of the stump are capped by concrete to preserve what is left.

The best and most technical description of the fossil I could find was in a paper by Marsh, B. D. &. Coleman, N. M., published in the Journal of Volcanology and Geothermal Research (volume 182, issues 1-2, pp. 76-96) in 2009, entitled ‘Magma Flow and Interaction with Waste Packages in a Geologic Repository at Yucca Mountain, Nevada’:

Perhaps a more pertinent example [of quenching] is MacCulloch’s Tree in Ardmeanach of the western Mull magmatic comples of Scotland. Here a large (~2 x 15 m) upright Eocence (~55 Ma) conifer (Taxodioxylon) has been encased in a columnar basalt lava flow. The clearly defined quenched margins are of a thickness approximately that of the radius of the tree (see Figure 7). In addition to the distinct quenched margins, also clear in this example is notable horizontal columnar jointing or fracturing due to contraction upon cooling. Columnar jointing is an indicator of the direction of cooling, with the trend of the columns being in the direction of the local strongest influence on cooling. This pattern of jointing shows the major effect of this tree in quenching massive flowing basalt.

I’ve annotated my photo to match Figure 7 in Marsh & Coleman’s paper, which they caption: ‘Upright Paleocene conifer caught in a thick basalt flow in Scotland. The distinctive quenched rinds have been noted along with the strong horizontal columnar jointing reflecting the overall effect of quenching and local rapid cooling. Also notice the man for scale. (after Emeleus and Bell, 2005).’ Emeleus and Bell are the authors of The Paleogene Volcanic Districts of Scotland. I provide the scale!

Posted in Gone for a walk + Holidays and field trips   |  6 comments

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